mapshaper.js

(function(){

var error = function() {
  var msg = Utils.toArray(arguments).join(' ');
  throw new Error(msg);
};

var Utils = {
  getUniqueName: function(prefix) {
    var n = Utils.__uniqcount || 0;
    Utils.__uniqcount = n + 1;
    return (prefix || "__id_") + n;
  },

  isFunction: function(obj) {
    return typeof obj == 'function';
  },

  isObject: function(obj) {
    return obj === Object(obj); // via underscore
  },

  clamp: function(val, min, max) {
    return val < min ? min : (val > max ? max : val);
  },

  interpolate: function(val1, val2, pct) {
    return val1 * (1-pct) + val2 * pct;
  },

  isArray: function(obj) {
    return Array.isArray(obj);
  },

  // NaN -> true
  isNumber: function(obj) {
    // return toString.call(obj) == '[object Number]'; // ie8 breaks?
    return obj != null && obj.constructor == Number;
  },

  isInteger: function(obj) {
    return Utils.isNumber(obj) && ((obj | 0) === obj);
  },

  isString: function(obj) {
    return obj != null && obj.toString === String.prototype.toString;
    // TODO: replace w/ something better.
  },

  isBoolean: function(obj) {
    return obj === true || obj === false;
  },

  // Convert an array-like object to an Array, or make a copy if @obj is an Array
  toArray: function(obj) {
    var arr;
    if (!Utils.isArrayLike(obj)) error("Utils.toArray() requires an array-like object");
    try {
      arr = Array.prototype.slice.call(obj, 0); // breaks in ie8
    } catch(e) {
      // support ie8
      arr = [];
      for (var i=0, n=obj.length; i<n; i++) {
        arr[i] = obj[i];
      }
    }
    return arr;
  },

  // Array like: has length property, is numerically indexed and mutable.
  // TODO: try to detect objects with length property but no indexed data elements
  isArrayLike: function(obj) {
    if (!obj) return false;
    if (Utils.isArray(obj)) return true;
    if (Utils.isString(obj)) return false;
    if (obj.length === 0) return true;
    if (obj.length > 0) return true;
    return false;
  },

  // See https://raw.github.com/kvz/phpjs/master/functions/strings/addslashes.js
  addslashes: function(str) {
    return (str + '').replace(/[\\"']/g, '\\$&').replace(/\u0000/g, '\\0');
  },

  // Escape a literal string to use in a regexp.
  // Ref.: http://simonwillison.net/2006/Jan/20/escape/
  regexEscape: function(str) {
    return str.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, '\\$&');
  },

  defaults: function(dest) {
    for (var i=1, n=arguments.length; i<n; i++) {
      var src = arguments[i] || {};
      for (var key in src) {
        if (key in dest === false && src.hasOwnProperty(key)) {
          dest[key] = src[key];
        }
      }
    }
    return dest;
  },

  extend: function(o) {
    var dest = o || {},
        n = arguments.length,
        key, i, src;
    for (i=1; i<n; i++) {
      src = arguments[i] || {};
      for (key in src) {
        if (src.hasOwnProperty(key)) {
          dest[key] = src[key];
        }
      }
    }
    return dest;
  },

  // Pseudoclassical inheritance
  //
  // Inherit from a Parent function:
  //    Utils.inherit(Child, Parent);
  // Call parent's constructor (inside child constructor):
  //    this.__super__([args...]);
  inherit: function(targ, src) {
    var f = function() {
      if (this.__super__ == f) {
        // add __super__ of parent to front of lookup chain
        // so parent class constructor can call its parent using this.__super__
        this.__super__ = src.prototype.__super__;
        // call parent constructor function. this.__super__ now points to parent-of-parent
        src.apply(this, arguments);
        // remove temp __super__, expose targ.prototype.__super__ again
        delete this.__super__;
      }
    };

    f.prototype = src.prototype || src; // added || src to allow inheriting from objects as well as functions
    // Extend targ prototype instead of wiping it out --
    //   in case inherit() is called after targ.prototype = {stuff}; statement
    targ.prototype = Utils.extend(new f(), targ.prototype); //
    targ.prototype.constructor = targ;
    targ.prototype.__super__ = f;
  },

  // Inherit from a parent, call the parent's constructor, optionally extend
  // prototype with optional additional arguments
  subclass: function(parent) {
    var child = function() {
      this.__super__.apply(this, Utils.toArray(arguments));
    };
    Utils.inherit(child, parent);
    for (var i=1; i<arguments.length; i++) {
      Utils.extend(child.prototype, arguments[i]);
    }
    return child;
  }

};



var Env = (function() {
  var inNode = typeof module !== 'undefined' && !!module.exports;
  var inBrowser = typeof window !== 'undefined' && !inNode;
  var inPhantom = inBrowser && !!(window.phantom && window.phantom.exit);
  var ieVersion = inBrowser && /MSIE ([0-9]+)/.exec(navigator.appVersion) && parseInt(RegExp.$1) || NaN;

  return {
    iPhone : inBrowser && !!(navigator.userAgent.match(/iPhone/i)),
    iPad : inBrowser && !!(navigator.userAgent.match(/iPad/i)),
    canvas: inBrowser && !!document.createElement('canvas').getContext,
    inNode : inNode,
    inPhantom : inPhantom,
    inBrowser: inBrowser,
    ieVersion: ieVersion,
    ie: !isNaN(ieVersion)
  };
})();


// Support for timing using T.start() and T.stop("message")
//
var T = {
  stack: [],
  verbose: true,

  start: function(msg) {
    if (T.verbose && msg) verbose(T.prefix() + msg);
    T.stack.push(+new Date);
  },

  // Stop timing, print a message if T.verbose == true
  stop: function(note) {
    var startTime = T.stack.pop();
    var elapsed = (+new Date - startTime);
    if (T.verbose) {
      var msg =  T.prefix() + elapsed + 'ms';
      if (note) {
        msg += " " + note;
      }
      verbose(msg);
    }
    return elapsed;
  },

  prefix: function() {
    var str = "- ",
        level = this.stack.length;
    while (level--) str = "-" + str;
    return str;
  }
};




// Append elements of @src array to @dest array
Utils.merge = function(dest, src) {
  if (!Utils.isArray(dest) || !Utils.isArray(src)) {
    error("Usage: Utils.merge(destArray, srcArray);")
  }
  if (src.length > 0) {
    dest.push.apply(dest, src);
  }
  return dest;
};

// Returns elements in arr and not in other
// (similar to underscore diff)
Utils.difference = function(arr, other) {
  var index = Utils.arrayToIndex(other);
  return arr.filter(function(el) {
    return !Object.prototype.hasOwnProperty.call(index, el);
  });
};

// Test a string or array-like object for existence of substring or element
Utils.contains = function(container, item) {
  if (Utils.isString(container)) {
    return container.indexOf(item) != -1;
  }
  else if (Utils.isArrayLike(container)) {
    return Utils.indexOf(container, item) != -1;
  }
  error("Expected Array or String argument");
};

Utils.some = function(arr, test) {
  return arr.reduce(function(val, item) {
    return val || test(item); // TODO: short-circuit?
  }, false);
};

Utils.every = function(arr, test) {
  return arr.reduce(function(val, item) {
    return val && test(item);
  }, true);
};

Utils.find = function(arr, test, ctx) {
  var matches = arr.filter(test, ctx);
  return matches.length === 0 ? null : matches[0];
};

Utils.indexOf = function(arr, item, prop) {
  if (prop) error("Utils.indexOf() No longer supports property argument");
  var nan = !(item === item);
  for (var i = 0, len = arr.length || 0; i < len; i++) {
    if (arr[i] === item) return i;
    if (nan && !(arr[i] === arr[i])) return i;
  }
  return -1;
};

Utils.range = function(len, start, inc) {
  var arr = [],
      v = start === void 0 ? 0 : start,
      i = inc === void 0 ? 1 : inc;
  while(len--) {
    arr.push(v);
    v += i;
  }
  return arr;
};

Utils.repeat = function(times, func) {
  var values = [],
      val;
  for (var i=0; i<times; i++) {
    val = func(i);
    if (val !== void 0) {
      values[i] = val;
    }
  }
  return values.length > 0 ? values : void 0;
};

// Calc sum, skip falsy and NaN values
// Assumes: no other non-numeric objects in array
//
Utils.sum = function(arr, info) {
  if (!Utils.isArrayLike(arr)) error ("Utils.sum() expects an array, received:", arr);
  var tot = 0,
      nan = 0,
      val;
  for (var i=0, n=arr.length; i<n; i++) {
    val = arr[i];
    if (val) {
      tot += val;
    } else if (isNaN(val)) {
      nan++;
    }
  }
  if (info) {
    info.nan = nan;
  }
  return tot;
};

// Calculate min and max values of an array, ignoring NaN values
Utils.getArrayBounds = function(arr) {
  var min = Infinity,
    max = -Infinity,
    nan = 0, val;
  for (var i=0, len=arr.length; i<len; i++) {
    val = arr[i];
    if (val !== val) nan++;
    if (val < min) min = val;
    if (val > max) max = val;
  }
  return {
    min: min,
    max: max,
    nan: nan
  };
};

Utils.uniq = function(src) {
  var index = {};
  return src.reduce(function(memo, el) {
    if (el in index === false) {
      index[el] = true;
      memo.push(el);
    }
    return memo;
  }, []);
};

Utils.pluck = function(arr, key) {
  return arr.map(function(obj) {
    return obj[key];
  });
};

Utils.countValues = function(arr) {
  return arr.reduce(function(memo, val) {
    memo[val] = (val in memo) ? memo[val] + 1 : 1;
    return memo;
  }, {});
};

Utils.indexOn = function(arr, k) {
  return arr.reduce(function(index, o) {
    index[o[k]] = o;
    return index;
  }, {});
};

Utils.groupBy = function(arr, k) {
  return arr.reduce(function(index, o) {
    var keyval = o[k];
    if (keyval in index) {
      index[keyval].push(o);
    } else {
      index[keyval] = [o]
    }
    return index;
  }, {});
};

Utils.arrayToIndex = function(arr, val) {
  var init = arguments.length > 1;
  return arr.reduce(function(index, key) {
    index[key] = init ? val : true;
    return index;
  }, {});
};

// Support for iterating over array-like objects, like typed arrays
Utils.forEach = function(arr, func, ctx) {
  if (!Utils.isArrayLike(arr)) {
    throw new Error("#forEach() takes an array-like argument. " + arr);
  }
  for (var i=0, n=arr.length; i < n; i++) {
    func.call(ctx, arr[i], i);
  }
};

Utils.forEachProperty = function(o, func, ctx) {
  Object.keys(o).forEach(function(key) {
    func.call(ctx, o[key], key);
  });
};

Utils.initializeArray = function(arr, init) {
  for (var i=0, len=arr.length; i<len; i++) {
    arr[i] = init;
  }
  return arr;
};

Utils.replaceArray = function(arr, arr2) {
  arr.splice(0, arr.length);
  arr.push.apply(arr, arr2);
};




Utils.repeatString = function(src, n) {
  var str = "";
  for (var i=0; i<n; i++)
    str += src;
  return str;
};

Utils.pluralSuffix = function(count) {
  return count != 1 ? 's' : '';
};

Utils.endsWith = function(str, ending) {
    return str.indexOf(ending, str.length - ending.length) !== -1;
};

Utils.lpad = function(str, size, pad) {
  pad = pad || ' ';
  str = String(str);
  return Utils.repeatString(pad, size - str.length) + str;
};

Utils.rpad = function(str, size, pad) {
  pad = pad || ' ';
  str = String(str);
  return str + Utils.repeatString(pad, size - str.length);
};

Utils.trim = function(str) {
  return Utils.ltrim(Utils.rtrim(str));
};

var ltrimRxp = /^\s+/;
Utils.ltrim = function(str) {
  return str.replace(ltrimRxp, '');
};

var rtrimRxp = /\s+$/;
Utils.rtrim = function(str) {
  return str.replace(rtrimRxp, '');
};

Utils.addThousandsSep = function(str) {
  var fmt = '',
      start = str[0] == '-' ? 1 : 0,
      dec = str.indexOf('.'),
      end = str.length,
      ins = (dec == -1 ? end : dec) - 3;
  while (ins > start) {
    fmt = ',' + str.substring(ins, end) + fmt;
    end = ins;
    ins -= 3;
  }
  return str.substring(0, end) + fmt;
};

Utils.numToStr = function(num, decimals) {
  return decimals >= 0 ? num.toFixed(decimals) : String(num);
};

Utils.formatNumber = function(num, decimals, nullStr, showPos) {
  var fmt;
  if (isNaN(num)) {
    fmt = nullStr || '-';
  } else {
    fmt = Utils.numToStr(num, decimals);
    fmt = Utils.addThousandsSep(fmt);
    if (showPos && parseFloat(fmt) > 0) {
      fmt = "+" + fmt;
    }
  }
  return fmt;
};



function Transform() {
  this.mx = this.my = 1;
  this.bx = this.by = 0;
}

Transform.prototype.isNull = function() {
  return !this.mx || !this.my || isNaN(this.bx) || isNaN(this.by);
};

Transform.prototype.invert = function() {
  var inv = new Transform();
  inv.mx = 1 / this.mx;
  inv.my = 1 / this.my;
  //inv.bx = -this.bx * inv.mx;
  //inv.by = -this.by * inv.my;
  inv.bx = -this.bx / this.mx;
  inv.by = -this.by / this.my;
  return inv;
};


Transform.prototype.transform = function(x, y, xy) {
  xy = xy || [];
  xy[0] = x * this.mx + this.bx;
  xy[1] = y * this.my + this.by;
  return xy;
};

Transform.prototype.toString = function() {
  return Utils.toString(Utils.extend({}, this));
};




function Bounds() {
  if (arguments.length > 0) {
    this.setBounds.apply(this, arguments);
  }
}

Bounds.prototype.toString = function() {
  return JSON.stringify({
    xmin: this.xmin,
    xmax: this.xmax,
    ymin: this.ymin,
    ymax: this.ymax
  });
};

Bounds.prototype.toArray = function() {
  return this.hasBounds() ? [this.xmin, this.ymin, this.xmax, this.ymax] : [];
};

Bounds.prototype.hasBounds = function() {
  return this.xmin <= this.xmax && this.ymin <= this.ymax;
};

Bounds.prototype.sameBounds =
Bounds.prototype.equals = function(bb) {
  return bb && this.xmin === bb.xmin && this.xmax === bb.xmax &&
    this.ymin === bb.ymin && this.ymax === bb.ymax;
};

Bounds.prototype.width = function() {
  return (this.xmax - this.xmin) || 0;
};

Bounds.prototype.height = function() {
  return (this.ymax - this.ymin) || 0;
};

Bounds.prototype.area = function() {
  return this.width() * this.height() || 0;
};

Bounds.prototype.empty = function() {
  this.xmin = this.ymin = this.xmax = this.ymax = void 0;
  return this;
};

Bounds.prototype.setBounds = function(a, b, c, d) {
  if (arguments.length == 1) {
    // assume first arg is a Bounds or array
    if (Utils.isArrayLike(a)) {
      b = a[1];
      c = a[2];
      d = a[3];
      a = a[0];
    } else {
      b = a.ymin;
      c = a.xmax;
      d = a.ymax;
      a = a.xmin;
    }
  }

  this.xmin = a;
  this.ymin = b;
  this.xmax = c;
  this.ymax = d;
  if (a > c || b > d) this.update();
  // error("Bounds#setBounds() min/max reversed:", a, b, c, d);
  return this;
};


Bounds.prototype.centerX = function() {
  var x = (this.xmin + this.xmax) * 0.5;
  return x;
};

Bounds.prototype.centerY = function() {
  var y = (this.ymax + this.ymin) * 0.5;
  return y;
};

Bounds.prototype.containsPoint = function(x, y) {
  if (x >= this.xmin && x <= this.xmax &&
    y <= this.ymax && y >= this.ymin) {
    return true;
  }
  return false;
};

// intended to speed up slightly bubble symbol detection; could use intersects() instead
// TODO: fix false positive where circle is just outside a corner of the box
Bounds.prototype.containsBufferedPoint =
Bounds.prototype.containsCircle = function(x, y, buf) {
  if ( x + buf > this.xmin && x - buf < this.xmax ) {
    if ( y - buf < this.ymax && y + buf > this.ymin ) {
      return true;
    }
  }
  return false;
};

Bounds.prototype.intersects = function(bb) {
  if (bb.xmin <= this.xmax && bb.xmax >= this.xmin &&
    bb.ymax >= this.ymin && bb.ymin <= this.ymax) {
    return true;
  }
  return false;
};

Bounds.prototype.contains = function(bb) {
  if (bb.xmin >= this.xmin && bb.ymax <= this.ymax &&
    bb.xmax <= this.xmax && bb.ymin >= this.ymin) {
    return true;
  }
  return false;
};

Bounds.prototype.shift = function(x, y) {
  this.setBounds(this.xmin + x,
    this.ymin + y, this.xmax + x, this.ymax + y);
};

Bounds.prototype.padBounds = function(a, b, c, d) {
  this.xmin -= a;
  this.ymin -= b;
  this.xmax += c;
  this.ymax += d;
};

// Rescale the bounding box by a fraction. TODO: implement focus.
// @param {number} pct Fraction of original extents
// @param {number} pctY Optional amount to scale Y
//
Bounds.prototype.scale = function(pct, pctY) { /*, focusX, focusY*/
  var halfWidth = (this.xmax - this.xmin) * 0.5;
  var halfHeight = (this.ymax - this.ymin) * 0.5;
  var kx = pct - 1;
  var ky = pctY === undefined ? kx : pctY - 1;
  this.xmin -= halfWidth * kx;
  this.ymin -= halfHeight * ky;
  this.xmax += halfWidth * kx;
  this.ymax += halfHeight * ky;
};

// Return a bounding box with the same extent as this one.
Bounds.prototype.cloneBounds = // alias so child classes can override clone()
Bounds.prototype.clone = function() {
  return new Bounds(this.xmin, this.ymin, this.xmax, this.ymax);
};

Bounds.prototype.clearBounds = function() {
  this.setBounds(new Bounds());
};

Bounds.prototype.mergePoint = function(x, y) {
  if (this.xmin === void 0) {
    this.setBounds(x, y, x, y);
  } else {
    // this works even if x,y are NaN
    if (x < this.xmin)  this.xmin = x;
    else if (x > this.xmax)  this.xmax = x;

    if (y < this.ymin) this.ymin = y;
    else if (y > this.ymax) this.ymax = y;
  }
};

// expands either x or y dimension to match @aspect (width/height ratio)
// @focusX, @focusY (optional): expansion focus, as a fraction of width and height
Bounds.prototype.fillOut = function(aspect, focusX, focusY) {
  if (arguments.length < 3) {
    focusX = 0.5;
    focusY = 0.5;
  }
  var w = this.width(),
      h = this.height(),
      currAspect = w / h,
      pad;
  if (isNaN(aspect) || aspect <= 0) {
    // error condition; don't pad
  } else if (currAspect < aspect) { // fill out x dimension
    pad = h * aspect - w;
    this.xmin -= (1 - focusX) * pad;
    this.xmax += focusX * pad;
  } else {
    pad = w / aspect - h;
    this.ymin -= (1 - focusY) * pad;
    this.ymax += focusY * pad;
  }
  return this;
};

Bounds.prototype.update = function() {
  var tmp;
  if (this.xmin > this.xmax) {
    tmp = this.xmin;
    this.xmin = this.xmax;
    this.xmax = tmp;
  }
  if (this.ymin > this.ymax) {
    tmp = this.ymin;
    this.ymin = this.ymax;
    this.ymax = tmp;
  }
};

Bounds.prototype.transform = function(t) {
  this.xmin = this.xmin * t.mx + t.bx;
  this.xmax = this.xmax * t.mx + t.bx;
  this.ymin = this.ymin * t.my + t.by;
  this.ymax = this.ymax * t.my + t.by;
  this.update();
  return this;
};

// Returns a Transform object for mapping this onto Bounds @b2
// @flipY (optional) Flip y-axis coords, for converting to/from pixel coords
//
Bounds.prototype.getTransform = function(b2, flipY) {
  var t = new Transform();
  t.mx = b2.width() / this.width();
  t.bx = b2.xmin - t.mx * this.xmin;
  if (flipY) {
    t.my = -b2.height() / this.height();
    t.by = b2.ymax - t.my * this.ymin;
  } else {
    t.my = b2.height() / this.height();
    t.by = b2.ymin - t.my * this.ymin;
  }
  return t;
};

Bounds.prototype.mergeCircle = function(x, y, r) {
  if (r < 0) r = -r;
  this.mergeBounds([x - r, y - r, x + r, y + r]);
};

Bounds.prototype.mergeBounds = function(bb) {
  var a, b, c, d;
  if (bb instanceof Bounds) {
    a = bb.xmin, b = bb.ymin, c = bb.xmax, d = bb.ymax;
  } else if (arguments.length == 4) {
    a = arguments[0];
    b = arguments[1];
    c = arguments[2];
    d = arguments[3];
  } else if (bb.length == 4) {
    // assume array: [xmin, ymin, xmax, ymax]
    a = bb[0], b = bb[1], c = bb[2], d = bb[3];
  } else {
    error("Bounds#mergeBounds() invalid argument:", bb);
  }

  if (this.xmin === void 0) {
    this.setBounds(a, b, c, d);
  } else {
    if (a < this.xmin) this.xmin = a;
    if (b < this.ymin) this.ymin = b;
    if (c > this.xmax) this.xmax = c;
    if (d > this.ymax) this.ymax = d;
  }
  return this;
};




// Sort an array of objects based on one or more properties.
// Usage: Utils.sortOn(array, key1, asc?[, key2, asc? ...])
//
Utils.sortOn = function(arr) {
  var comparators = [];
  for (var i=1; i<arguments.length; i+=2) {
    comparators.push(Utils.getKeyComparator(arguments[i], arguments[i+1]));
  }
  arr.sort(function(a, b) {
    var cmp = 0,
        i = 0,
        n = comparators.length;
    while (i < n && cmp === 0) {
      cmp = comparators[i](a, b);
      i++;
    }
    return cmp;
  });
  return arr;
};

// Sort array of values that can be compared with < > operators (strings, numbers)
// null, undefined and NaN are sorted to the end of the array
//
Utils.genericSort = function(arr, asc) {
  var compare = Utils.getGenericComparator(asc);
  Array.prototype.sort.call(arr, compare);
  return arr;
};

Utils.sortOnKey = function(arr, getter, asc) {
  var compare = Utils.getGenericComparator(asc !== false) // asc is default
  arr.sort(function(a, b) {
    return compare(getter(a), getter(b));
  });
};

// Stashes keys in a temp array (better if calculating key is expensive).
Utils.sortOnKey2 = function(arr, getKey, asc) {
  Utils.sortArrayByKeys(arr, arr.map(getKey), asc);
};

Utils.sortArrayByKeys = function(arr, keys, asc) {
  var ids = Utils.getSortedIds(keys, asc);
  Utils.reorderArray(arr, ids);
};

Utils.getSortedIds = function(arr, asc) {
  var ids = Utils.range(arr.length);
  Utils.sortArrayIndex(ids, arr, asc);
  return ids;
};

Utils.sortArrayIndex = function(ids, arr, asc) {
  var compare = Utils.getGenericComparator(asc);
  ids.sort(function(i, j) {
    // added i, j comparison to guarantee that sort is stable
    var cmp = compare(arr[i], arr[j]);
    return cmp > 0 || cmp === 0 && i < j ? 1 : -1;
  });
};

Utils.reorderArray = function(arr, idxs) {
  var len = idxs.length;
  var arr2 = [];
  for (var i=0; i<len; i++) {
    var idx = idxs[i];
    if (idx < 0 || idx >= len) error("Out-of-bounds array idx");
    arr2[i] = arr[idx];
  }
  Utils.replaceArray(arr, arr2);
};

Utils.getKeyComparator = function(key, asc) {
  var compare = Utils.getGenericComparator(asc);
  return function(a, b) {
    return compare(a[key], b[key]);
  };
};

Utils.getGenericComparator = function(asc) {
  asc = asc !== false;
  return function(a, b) {
    var retn = 0;
    if (b == null) {
      retn = a == null ? 0 : -1;
    } else if (a == null) {
      retn = 1;
    } else if (a < b) {
      retn = asc ? -1 : 1;
    } else if (a > b) {
      retn = asc ? 1 : -1;
    } else if (a !== a) {
      retn = 1;
    } else if (b !== b) {
      retn = -1;
    }
    return retn;
  };
};





// Generic in-place sort (null, NaN, undefined not handled)
Utils.quicksort = function(arr, asc) {
  Utils.quicksortPartition(arr, 0, arr.length-1);
  if (asc === false) Array.prototype.reverse.call(arr); // Works with typed arrays
  return arr;
};

// Moved out of Utils.quicksort() (saw >100% speedup in Chrome with deep recursion)
Utils.quicksortPartition = function (a, lo, hi) {
  var i = lo,
      j = hi,
      pivot, tmp;
  while (i < hi) {
    pivot = a[lo + hi >> 1]; // avoid n^2 performance on sorted arrays
    while (i <= j) {
      while (a[i] < pivot) i++;
      while (a[j] > pivot) j--;
      if (i <= j) {
        tmp = a[i];
        a[i] = a[j];
        a[j] = tmp;
        i++;
        j--;
      }
    }
    if (lo < j) Utils.quicksortPartition(a, lo, j);
    lo = i;
    j = hi;
  }
};




Utils.findRankByValue = function(arr, value) {
  if (isNaN(value)) return arr.length;
  var rank = 1;
  for (var i=0, n=arr.length; i<n; i++) {
    if (value > arr[i]) rank++;
  }
  return rank;
}

Utils.findValueByPct = function(arr, pct) {
  var rank = Math.ceil((1-pct) * (arr.length));
  return Utils.findValueByRank(arr, rank);
};

// See http://ndevilla.free.fr/median/median/src/wirth.c
// Elements of @arr are reordered
//
Utils.findValueByRank = function(arr, rank) {
  if (!arr.length || rank < 1 || rank > arr.length) error("[findValueByRank()] invalid input");

  rank = Utils.clamp(rank | 0, 1, arr.length);
  var k = rank - 1, // conv. rank to array index
      n = arr.length,
      l = 0,
      m = n - 1,
      i, j, val, tmp;

  while (l < m) {
    val = arr[k];
    i = l;
    j = m;
    do {
      while (arr[i] < val) {i++;}
      while (val < arr[j]) {j--;}
      if (i <= j) {
        tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
        i++;
        j--;
      }
    } while (i <= j);
    if (j < k) l = i;
    if (k < i) m = j;
  }
  return arr[k];
};

//
//
Utils.findMedian = function(arr) {
  var n = arr.length,
      rank = Math.floor(n / 2) + 1,
      median = Utils.findValueByRank(arr, rank);
  if ((n & 1) == 0) {
    median = (median + Utils.findValueByRank(arr, rank - 1)) / 2;
  }
  return median;
};




// Wrapper for DataView class for more convenient reading and writing of
//   binary data; Remembers endianness and read/write position.
// Has convenience methods for copying from buffers, etc.
//
function BinArray(buf, le) {
  if (Utils.isNumber(buf)) {
    buf = new ArrayBuffer(buf);
  } else if (Env.inNode && buf instanceof Buffer == true) {
    // Since node 0.10, DataView constructor doesn't accept Buffers,
    //   so need to copy Buffer to ArrayBuffer
    buf = BinArray.toArrayBuffer(buf);
  }
  if (buf instanceof ArrayBuffer == false) {
    error("BinArray constructor takes an integer, ArrayBuffer or Buffer argument");
  }
  this._buffer = buf;
  this._bytes = new Uint8Array(buf);
  this._view = new DataView(buf);
  this._idx = 0;
  this._le = le !== false;
}

BinArray.bufferToUintArray = function(buf, wordLen) {
  if (wordLen == 4) return new Uint32Array(buf);
  if (wordLen == 2) return new Uint16Array(buf);
  if (wordLen == 1) return new Uint8Array(buf);
  error("BinArray.bufferToUintArray() invalid word length:", wordLen)
};

BinArray.uintSize = function(i) {
  return i & 1 || i & 2 || 4;
};

BinArray.bufferCopy = function(dest, destId, src, srcId, bytes) {
  srcId = srcId || 0;
  bytes = bytes || src.byteLength - srcId;
  if (dest.byteLength - destId < bytes)
    error("Buffer overflow; tried to write:", bytes);

  // When possible, copy buffer data in multi-byte chunks... Added this for faster copying of
  // shapefile data, which is aligned to 32 bits.
  var wordSize = Math.min(BinArray.uintSize(bytes), BinArray.uintSize(srcId),
      BinArray.uintSize(dest.byteLength), BinArray.uintSize(destId),
      BinArray.uintSize(src.byteLength));

  var srcArr = BinArray.bufferToUintArray(src, wordSize),
      destArr = BinArray.bufferToUintArray(dest, wordSize),
      count = bytes / wordSize,
      i = srcId / wordSize,
      j = destId / wordSize;

  while (count--) {
    destArr[j++] = srcArr[i++];
  }
  return bytes;
};

BinArray.toArrayBuffer = function(src) {
  var n = src.length,
      dest = new ArrayBuffer(n),
      view = new Uint8Array(dest);
  for (var i=0; i<n; i++) {
      view[i] = src[i];
  }
  return dest;
};

// Return length in bytes of an ArrayBuffer or Buffer
//
BinArray.bufferSize = function(buf) {
  return (buf instanceof ArrayBuffer ?  buf.byteLength : buf.length | 0);
};

Utils.buffersAreIdentical = function(a, b) {
  var alen = BinArray.bufferSize(a);
  var blen = BinArray.bufferSize(b);
  if (alen != blen) {
    return false;
  }
  for (var i=0; i<alen; i++) {
    if (a[i] !== b[i]) {
      return false;
    }
  }
  return true;
};

BinArray.prototype = {
  size: function() {
    return this._buffer.byteLength;
  },

  littleEndian: function() {
    this._le = true;
    return this;
  },

  bigEndian: function() {
    this._le = false;
    return this;
  },

  buffer: function() {
    return this._buffer;
  },

  bytesLeft: function() {
    return this._buffer.byteLength - this._idx;
  },

  skipBytes: function(bytes) {
    this._idx += (bytes + 0);
    return this;
  },

  readUint8: function() {
    return this._bytes[this._idx++];
  },

  writeUint8: function(val) {
    this._bytes[this._idx++] = val;
    return this;
  },

  readInt8: function() {
    return this._view.getInt8(this._idx++);
  },

  writeInt8: function(val) {
    this._view.setInt8(this._idx++, val);
    return this;
  },

  readUint16: function() {
    var val = this._view.getUint16(this._idx, this._le);
    this._idx += 2;
    return val;
  },

  writeUint16: function(val) {
    this._view.setUint16(this._idx, val, this._le);
    this._idx += 2;
    return this;
  },

  readUint32: function() {
    var val = this._view.getUint32(this._idx, this._le);
    this._idx += 4;
    return val;
  },

  writeUint32: function(val) {
    this._view.setUint32(this._idx, val, this._le);
    this._idx += 4;
    return this;
  },

  readInt32: function() {
    var val = this._view.getInt32(this._idx, this._le);
    this._idx += 4;
    return val;
  },

  writeInt32: function(val) {
    this._view.setInt32(this._idx, val, this._le);
    this._idx += 4;
    return this;
  },

  readFloat64: function() {
    var val = this._view.getFloat64(this._idx, this._le);
    this._idx += 8;
    return val;
  },

  writeFloat64: function(val) {
    this._view.setFloat64(this._idx, val, this._le);
    this._idx += 8;
    return this;
  },

  // Returns a Float64Array containing @len doubles
  //
  readFloat64Array: function(len) {
    var bytes = len * 8,
        i = this._idx,
        buf = this._buffer,
        arr;
    // Inconsistent: first is a view, second a copy...
    if (i % 8 === 0) {
      arr = new Float64Array(buf, i, len);
    } else if (buf.slice) {
      arr = new Float64Array(buf.slice(i, i + bytes));
    } else { // ie10, etc
      var dest = new ArrayBuffer(bytes);
      BinArray.bufferCopy(dest, 0, buf, i, bytes);
      arr = new Float64Array(dest);
    }
    this._idx += bytes;
    return arr;
  },

  readUint32Array: function(len) {
    var arr = [];
    for (var i=0; i<len; i++) {
      arr.push(this.readUint32());
    }
    return arr;
  },

  peek: function() {
    return this._view.getUint8(this._idx);
  },

  position: function(i) {
    if (i != null) {
      this._idx = i;
      return this;
    }
    return this._idx;
  },

  readCString: function(fixedLen, asciiOnly) {
    var str = "",
        count = fixedLen >= 0 ? fixedLen : this.bytesLeft();
    while (count > 0) {
      var byteVal = this.readUint8();
      count--;
      if (byteVal == 0) {
        break;
      } else if (byteVal > 127 && asciiOnly) {
        str = null;
        break;
      }
      str += String.fromCharCode(byteVal);
    }

    if (fixedLen > 0 && count > 0) {
      this.skipBytes(count);
    }
    return str;
  },

  writeString: function(str, maxLen) {
    var bytesWritten = 0,
        charsToWrite = str.length,
        cval;
    if (maxLen) {
      charsToWrite = Math.min(charsToWrite, maxLen);
    }
    for (var i=0; i<charsToWrite; i++) {
      cval = str.charCodeAt(i);
      if (cval > 127) {
        trace("#writeCString() Unicode value beyond ascii range")
        cval = '?'.charCodeAt(0);
      }
      this.writeUint8(cval);
      bytesWritten++;
    }
    return bytesWritten;
  },

  writeCString: function(str, fixedLen) {
    var maxChars = fixedLen ? fixedLen - 1 : null,
        bytesWritten = this.writeString(str, maxChars);

    this.writeUint8(0); // terminator
    bytesWritten++;

    if (fixedLen) {
      while (bytesWritten < fixedLen) {
        this.writeUint8(0);
        bytesWritten++;
      }
    }
    return this;
  },

  writeBuffer: function(buf, bytes, startIdx) {
    this._idx += BinArray.bufferCopy(this._buffer, this._idx, buf, startIdx, bytes);
    return this;
  }
};




/*
A simplified version of printf formatting
Format codes: %[flags][width][.precision]type

supported flags:
  +   add '+' before positive numbers
  0   left-pad with '0'
  '   Add thousands separator
width: 1 to many
precision: .(1 to many)
type:
  s     string
  di    integers
  f     decimal numbers
  xX    hexidecimal (unsigned)
  %     literal '%'

Examples:
  code    val    formatted
  %+d     1      '+1'
  %4i     32     '  32'
  %04i    32     '0032'
  %x      255    'ff'
  %.2f    0.125  '0.13'
  %'f     1000   '1,000'
*/

// Usage: Utils.format(formatString, [values])
// Tip: When reusing the same format many times, use Utils.formatter() for 5x - 10x better performance
//
Utils.format = function(fmt) {
  var fn = Utils.formatter(fmt);
  var str = fn.apply(null, Array.prototype.slice.call(arguments, 1));
  return str;
};

function formatValue(val, matches) {
  var flags = matches[1];
  var padding = matches[2];
  var decimals = matches[3] ? parseInt(matches[3].substr(1)) : void 0;
  var type = matches[4];
  var isString = type == 's',
      isHex = type == 'x' || type == 'X',
      isInt = type == 'd' || type == 'i',
      isFloat = type == 'f',
      isNumber = !isString;

  var sign = "",
      padDigits = 0,
      isZero = false,
      isNeg = false;

  var str;
  if (isString) {
    str = String(val);
  }
  else if (isHex) {
    str = val.toString(16);
    if (type == 'X')
      str = str.toUpperCase();
  }
  else if (isNumber) {
    str = Utils.numToStr(val, isInt ? 0 : decimals);
    if (str[0] == '-') {
      isNeg = true;
      str = str.substr(1);
    }
    isZero = parseFloat(str) == 0;
    if (flags.indexOf("'") != -1 || flags.indexOf(',') != -1) {
      str = Utils.addThousandsSep(str);
    }
    if (!isZero) { // BUG: sign is added when num rounds to 0
      if (isNeg) {
        sign = "\u2212"; // U+2212
      } else if (flags.indexOf('+') != -1) {
        sign = '+';
      }
    }
  }

  if (padding) {
    var strLen = str.length + sign.length;
    var minWidth = parseInt(padding, 10);
    if (strLen < minWidth) {
      padDigits = minWidth - strLen;
      var padChar = flags.indexOf('0') == -1 ? ' ' : '0';
      var padStr = Utils.repeatString(padChar, padDigits);
    }
  }

  if (padDigits == 0) {
    str = sign + str;
  } else if (padChar == '0') {
    str = sign + padStr + str;
  } else {
    str = padStr + sign + str;
  }
  return str;
}

// Get a function for interpolating formatted values into a string.
Utils.formatter = function(fmt) {
  var codeRxp = /%([\',+0]*)([1-9]?)((?:\.[1-9])?)([sdifxX%])/g;
  var literals = [],
      formatCodes = [],
      startIdx = 0,
      prefix = "",
      literal,
      matches;

  while (matches=codeRxp.exec(fmt)) {
    literal = fmt.substring(startIdx, codeRxp.lastIndex - matches[0].length);
    if (matches[0] == '%%') {
      prefix += literal + '%';
    } else {
      literals.push(prefix + literal);
      prefix = '';
      formatCodes.push(matches);
    }
    startIdx = codeRxp.lastIndex;
  }
  literals.push(prefix + fmt.substr(startIdx));

  return function() {
    var str = literals[0],
        n = arguments.length;
    if (n != formatCodes.length) {
      error("[format()] Data does not match format string; format:", fmt, "data:", arguments);
    }
    for (var i=0; i<n; i++) {
      str += formatValue(arguments[i], formatCodes[i]) + literals[i+1];
    }
    return str;
  };
};





var api = {};
var MapShaper = api.internal = {};
var geom = api.geom = {};
var cli = api.cli = {};
var utils = api.utils = Utils.extend({}, Utils);

MapShaper.VERSION = '0.3.13';
MapShaper.LOGGING = false;
MapShaper.TRACING = false;
MapShaper.VERBOSE = false;
MapShaper.CLI = typeof cli != 'undefined';

api.enableLogging = function() {
  MapShaper.LOGGING = true;
  return api;
};

api.printError = function(err) {
  var msg;
  if (utils.isString(err)) {
    err = new APIError(err);
  }
  if (MapShaper.LOGGING && err.name == 'APIError') {
    msg = err.message;
    if (!/Error/.test(msg)) {
      msg = "Error: " + msg;
    }
    message(msg);
    message("Run mapshaper -h to view help");
  } else {
    throw err;
  }
};

function APIError(msg) {
  var err = new Error(msg);
  err.name = 'APIError';
  return err;
}

var warning = function() {
  message("Warning: " + MapShaper.formatLogArgs(arguments));
};

var message = function() {
  if (MapShaper.LOGGING) {
    MapShaper.logArgs(arguments);
  }
};

// alias for message; useful in web UI for sending some messages to the
// debugging console instead of the command line.
var consoleMessage = message;

var verbose = function() {
  if (MapShaper.VERBOSE && MapShaper.LOGGING) {
    MapShaper.logArgs(arguments);
  }
};

var trace = function() {
  if (MapShaper.TRACING) {
    MapShaper.logArgs(arguments);
  }
};

MapShaper.formatLogArgs = function(args) {
  return utils.toArray(args).join(' ');
};

// Format an array of (preferably short) strings in columns for console logging.
MapShaper.formatStringsAsGrid = function(arr) {
  // TODO: variable column width
  var longest = arr.reduce(function(len, str) {
        return Math.max(len, str.length);
      }, 0),
      colWidth = longest + 2,
      perLine = Math.floor(80 / colWidth) || 1;
  return arr.reduce(function(memo, name, i) {
    var col = i % perLine;
    if (i > 0 && col === 0) memo += '\n';
    if (col < perLine - 1) { // right-pad all but rightmost column
      name = utils.rpad(name, colWidth - 2, ' ');
    }
    return memo +  '  ' + name;
  }, '');
};

MapShaper.logArgs = function(args) {
  if (utils.isArrayLike(args)) {
    (console.error || console.log).call(console, MapShaper.formatLogArgs(args));
  }
};

function absArcId(arcId) {
  return arcId >= 0 ? arcId : ~arcId;
}

utils.wildcardToRegExp = function(name) {
  var rxp = name.split('*').map(function(str) {
    return utils.regexEscape(str);
  }).join('.*');
  return new RegExp(rxp);
};

MapShaper.expandoBuffer = function(constructor, rate) {
  var capacity = 0,
      k = rate >= 1 ? rate : 1.2,
      buf;
  return function(size) {
    if (size > capacity) {
      capacity = Math.ceil(size * k);
      buf = new constructor(capacity);
    }
    return buf;
  };
};

MapShaper.copyElements = function(src, i, dest, j, n, rev) {
  if (src === dest && j > i) error ("copy error");
  var inc = 1,
      offs = 0;
  if (rev) {
    inc = -1;
    offs = n - 1;
  }
  for (var k=0; k<n; k++, offs += inc) {
    dest[k + j] = src[i + offs];
  }
};

MapShaper.extendBuffer = function(src, newLen, copyLen) {
  var len = Math.max(src.length, newLen);
  var n = copyLen || src.length;
  var dest = new src.constructor(len);
  MapShaper.copyElements(src, 0, dest, 0, n);
  return dest;
};

MapShaper.mergeNames = function(name1, name2) {
  var merged = "";
  if (name1 && name2) {
    merged = utils.findStringPrefix(name1, name2).replace(/[-_]$/, '');
  }
  return merged;
};

utils.findStringPrefix = function(a, b) {
  var i = 0;
  for (var n=a.length; i<n; i++) {
    if (a[i] !== b[i]) break;
  }
  return a.substr(0, i);
};

// Resolve name conflicts in field names by appending numbers
// @fields Array of field names
// @maxLen (optional) Maximum chars in name
//
MapShaper.getUniqFieldNames = function(fields, maxLen) {
  var used = {};
  return fields.map(function(name) {
    var i = 0,
        validName;
    do {
      validName = MapShaper.adjustFieldName(name, maxLen, i);
      i++;
    } while (validName in used);
    used[validName] = true;
    return validName;
  });
};

// Truncate and/or uniqify a name (if relevant params are present)
MapShaper.adjustFieldName = function(name, maxLen, i) {
  var name2, suff;
  maxLen = maxLen || 256;
  if (!i) {
    name2 = name.substr(0, maxLen);
  } else {
    suff = String(i);
    if (suff.length == 1) {
      suff = '_' + suff;
    }
    name2 = name.substr(0, maxLen - suff.length) + suff;
  }
  return name2;
};


// Similar to isFinite() but returns false for null
utils.isFiniteNumber = function(val) {
  return isFinite(val) && val !== null;
};

MapShaper.getWorldBounds = function(e) {
  e = utils.isFiniteNumber(e) ? e : 1e-10;
  return [-180 + e, -90 + e, 180 - e, 90 - e];
};

MapShaper.probablyDecimalDegreeBounds = function(b) {
  var world = MapShaper.getWorldBounds(-1), // add a bit of excess
      bbox = (b instanceof Bounds) ? b.toArray() : b;
  return containsBounds(world, bbox);
};

MapShaper.layerHasGeometry = function(lyr) {
  return MapShaper.layerHasPaths(lyr) || MapShaper.layerHasPoints(lyr);
};

MapShaper.layerHasPaths = function(lyr) {
  return (lyr.geometry_type == 'polygon' || lyr.geometry_type == 'polyline') &&
    MapShaper.layerHasNonNullShapes(lyr);
};

MapShaper.layerHasPoints = function(lyr) {
  return lyr.geometry_type == 'point' && MapShaper.layerHasNonNullShapes(lyr);
};

MapShaper.layerHasNonNullShapes = function(lyr) {
  return utils.some(lyr.shapes || [], function(shp) {
    return !!shp;
  });
};

MapShaper.requirePolygonLayer = function(lyr, msg) {
  if (!lyr || lyr.geometry_type !== 'polygon') stop(msg || "Expected a polygon layer");
};

MapShaper.requirePathLayer = function(lyr, msg) {
  if (!lyr || !MapShaper.layerHasPaths(lyr)) stop(msg || "Expected a polygon or polyline layer");
};




utils.replaceFileExtension = function(path, ext) {
  var info = utils.parseLocalPath(path);
  return info.pathbase + '.' + ext;
};

utils.getPathSep = function(path) {
  // TODO: improve
  return path.indexOf('/') == -1 && path.indexOf('\\') != -1 ? '\\' : '/';
};

// Parse the path to a file without using Node
// Assumes: not a directory path
utils.parseLocalPath = function(path) {
  var obj = {},
      sep = utils.getPathSep(path),
      parts = path.split(sep),
      i;

  if (parts.length == 1) {
    obj.filename = parts[0];
    obj.directory = "";
  } else {
    obj.filename = parts.pop();
    obj.directory = parts.join(sep);
  }
  i = obj.filename.lastIndexOf('.');
  if (i > -1) {
    obj.extension = obj.filename.substr(i + 1);
    obj.basename = obj.filename.substr(0, i);
    obj.pathbase = path.substr(0, path.lastIndexOf('.'));
  } else {
    obj.extension = "";
    obj.basename = obj.filename;
    obj.pathbase = path;
  }
  return obj;
};

utils.getFileBase = function(path) {
  return utils.parseLocalPath(path).basename;
};

utils.getFileExtension = function(path) {
  return utils.parseLocalPath(path).extension;
};

utils.getPathBase = function(path) {
  return utils.parseLocalPath(path).pathbase;
};

MapShaper.getCommonFileBase = function(names) {
  return names.reduce(function(memo, name, i) {
    if (i === 0) {
      memo = utils.getFileBase(name);
    } else {
      memo = MapShaper.mergeNames(memo, name);
    }
    return memo;
  }, "");
};






// Guess the type of a data file from file extension, or return null if not sure
MapShaper.guessInputFileType = function(file) {
  var ext = utils.getFileExtension(file || '').toLowerCase(),
      type = null;
  if (ext == 'dbf' || ext == 'shp' || ext == 'prj') {
    type = ext;
  } else if (/json$/.test(ext)) {
    type = 'json';
  }
  return type;
};

MapShaper.guessInputContentType = function(content) {
  var type = null;
  if (utils.isString(content)) {
    type = MapShaper.stringLooksLikeJSON(content) ? 'json' : 'text';
  } else if (utils.isObject(content) && content.type || utils.isArray(content)) {
    type = 'json';
  }
  return type;
};

MapShaper.guessInputType = function(file, content) {
  return MapShaper.guessInputFileType(file) || MapShaper.guessInputContentType(content);
};

//
MapShaper.stringLooksLikeJSON = function(str) {
  return /^\s*[{[]/.test(String(str));
};

MapShaper.couldBeDsvFile = function(name) {
  var ext = utils.getFileExtension(name).toLowerCase();
  return /csv|tsv|txt$/.test(ext);
};

// Infer output format by considering file name and (optional) input format
MapShaper.inferOutputFormat = function(file, inputFormat) {
  var ext = utils.getFileExtension(file).toLowerCase(),
      format = null;
  if (ext == 'shp') {
    format = 'shapefile';
  } else if (ext == 'dbf') {
    format = 'dbf';
  } else if (/json$/.test(ext)) {
    format = 'geojson';
    if (ext == 'topojson' || inputFormat == 'topojson' && ext != 'geojson') {
      format = 'topojson';
    } else if (ext == 'json' && inputFormat == 'json') {
      format = 'json'; // JSON table
    }
  } else if (MapShaper.couldBeDsvFile(file)) {
    format = 'dsv';
  } else if (inputFormat) {
    format = inputFormat;
  }
  return format;
};

MapShaper.isZipFile = function(file) {
  return /\.zip$/i.test(file);
};

MapShaper.isSupportedOutputFormat = function(fmt) {
  var types = ['geojson', 'topojson', 'json', 'dsv', 'dbf', 'shapefile'];
  return types.indexOf(fmt) > -1;
};

// Assumes file at @path is one of Mapshaper's supported file types
MapShaper.isBinaryFile = function(path) {
  var ext = utils.getFileExtension(path).toLowerCase();
  return ext == 'shp' || ext == 'dbf' || ext == 'zip'; // GUI accepts zip files
};

// Detect extensions of some unsupported file types, for cmd line validation
MapShaper.filenameIsUnsupportedOutputType = function(file) {
  var rxp = /\.(shx|prj|xls|xlsx|gdb|sbn|sbx|xml|kml)$/i;
  return rxp.test(file);
};




var R = 6378137;
var D2R = Math.PI / 180;

// Equirectangular projection
function degreesToMeters(deg) {
  return deg * D2R * R;
}

function distance3D(ax, ay, az, bx, by, bz) {
  var dx = ax - bx,
    dy = ay - by,
    dz = az - bz;
  return Math.sqrt(dx * dx + dy * dy + dz * dz);
}

function distanceSq(ax, ay, bx, by) {
  var dx = ax - bx,
      dy = ay - by;
  return dx * dx + dy * dy;
}

function distance2D(ax, ay, bx, by) {
  var dx = ax - bx,
      dy = ay - by;
  return Math.sqrt(dx * dx + dy * dy);
}

function distanceSq3D(ax, ay, az, bx, by, bz) {
  var dx = ax - bx,
      dy = ay - by,
      dz = az - bz;
  return dx * dx + dy * dy + dz * dz;
}

function getRoundingFunction(inc) {
  if (!utils.isNumber(inc) || inc === 0) {
    error("Rounding increment must be a non-zero number.");
  }
  var inv = 1 / inc;
  if (inv > 1) inv = Math.round(inv);
  return function(x) {
    return Math.round(x * inv) / inv;
    // these alternatives show rounding error after JSON.stringify()
    // return Math.round(x / inc) / inv;
    // return Math.round(x / inc) * inc;
    // return Math.round(x * inv) * inc;
  };
}

// Return id of nearest point to x, y, among x0, y0, x1, y1, ...
function nearestPoint(x, y, x0, y0) {
  var minIdx = -1,
      minDist = Infinity,
      dist;
  for (var i = 0, j = 2, n = arguments.length; j < n; i++, j += 2) {
    dist = distanceSq(x, y, arguments[j], arguments[j+1]);
    if (dist < minDist) {
      minDist = dist;
      minIdx = i;
    }
  }
  return minIdx;
}

function lineIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  var den = determinant2D(s1p2x - s1p1x, s1p2y - s1p1y, s2p2x - s2p1x, s2p2y - s2p1y);
  if (den === 0) return null;
  var m = orient2D(s2p1x, s2p1y, s2p2x, s2p2y, s1p1x, s1p1y) / den;
  var x = s1p1x + m * (s1p2x - s1p1x);
  var y = s1p1y + m * (s1p2y - s1p1y);
  return [x, y];
}

// Get intersection point if segments are non-collinear, else return null
// Assumes that segments intersect
function crossIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  var p = lineIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y);
  var nearest;
  if (p) {
    // Re-order operands so intersection point is closest to s1p1 (better precision)
    // Source: Jonathan Shewchuk http://www.cs.berkeley.edu/~jrs/meshpapers/robnotes.pdf
    nearest = nearestPoint(p[0], p[1], s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y);
    if (nearest == 1) {
      // use b a c d
      p = lineIntersection(s1p2x, s1p2y, s1p1x, s1p1y, s2p1x, s2p1y, s2p2x, s2p2y);
    } else if (nearest == 2) {
      // use c d a b
      p = lineIntersection(s2p1x, s2p1y, s2p2x, s2p2y, s1p1x, s1p1y, s1p2x, s1p2y);
    } else if (nearest == 3) {
      // use d c a b
      p = lineIntersection(s2p2x, s2p2y, s2p1x, s2p1y, s1p1x, s1p1y, s1p2x, s1p2y);
    }
  }
  return p;
}

// Source: Sedgewick, _Algorithms in C_
// (Tried various other functions that failed owing to floating point errors)
function segmentHit(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  return orient2D(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y) *
      orient2D(s1p1x, s1p1y, s1p2x, s1p2y, s2p2x, s2p2y) <= 0 &&
      orient2D(s2p1x, s2p1y, s2p2x, s2p2y, s1p1x, s1p1y) *
      orient2D(s2p1x, s2p1y, s2p2x, s2p2y, s1p2x, s1p2y) <= 0;
}

function inside(x, minX, maxX) {
  return x > minX && x < maxX;
}

function sortSeg(x1, y1, x2, y2) {
  return x1 < x2 || x1 == x2 && y1 < y2 ? [x1, y1, x2, y2] : [x2, y2, x1, y1];
}

// Assume segments s1 and s2 are collinear and overlap; find one or two internal endpoints points
// TODO: refactor
function collinearIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  var minX = Math.min(s1p1x, s1p2x, s2p1x, s2p2x),
      maxX = Math.max(s1p1x, s1p2x, s2p1x, s2p2x),
      minY = Math.min(s1p1y, s1p2y, s2p1y, s2p2y),
      maxY = Math.max(s1p1y, s1p2y, s2p1y, s2p2y),
      useY = maxY - minY > maxX - minX,
      coords = [];

  if (useY ? inside(s1p1y, minY, maxY) : inside(s1p1x, minX, maxX)) {
    coords.push(s1p1x, s1p1y);
  }
  if (useY ? inside(s1p2y, minY, maxY) : inside(s1p2x, minX, maxX)) {
    coords.push(s1p2x, s1p2y);
  }
  if (useY ? inside(s2p1y, minY, maxY) : inside(s2p1x, minX, maxX)) {
    coords.push(s2p1x, s2p1y);
  }
  if (useY ? inside(s2p2y, minY, maxY) : inside(s2p2x, minX, maxX)) {
    coords.push(s2p2x, s2p2y);
  }
  if (coords.length != 2 && coords.length != 4) {
    // e.g. congruent segments
    trace("Invalid collinear segment intersection", coords);
    coords = null;
  } else if (coords.length == 4 && coords[0] == coords[2] && coords[1] == coords[3]) {
    // segs that meet in the middle don't count
    coords = null;
  }
  return coords;
}

function endpointHit(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  return s1p1x == s2p1x && s1p1y == s2p1y || s1p1x == s2p2x && s1p1y == s2p2y ||
          s1p2x == s2p1x && s1p2y == s2p1y || s1p2x == s2p2x && s1p2y == s2p2y;
}

// Find intersections between two 2D segments.
// Return [x, y] point if segments intersect at a single point or are overlapping+collinear
//   and one endpoint is inside overlapping portion
// Return [x1, y1, x2, y2] if segments are overlapping+collinear and have two endpoints inside overlapping portion
// Return null if segments do not touch
function segmentIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y) {
  var hit = segmentHit(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y),
      p = null;
  if (hit) {
    p = crossIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y);
    if (!p) { // colinear if p is null
      p = collinearIntersection(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y);
    } else if (endpointHit(s1p1x, s1p1y, s1p2x, s1p2y, s2p1x, s2p1y, s2p2x, s2p2y)) {
      p = null; // filter out segments that only intersect at an endpoint
    }
  }
  return p;
}

// Determinant of matrix
//  | a  b |
//  | c  d |
function determinant2D(a, b, c, d) {
  return a * d - b * c;
}

// Source: Jonathan Shewchuk http://www.cs.berkeley.edu/~jrs/meshpapers/robnotes.pdf
function orient2D(x0, y0, x1, y1, x2, y2) {
  return determinant2D(x0 - x2, y0 - y2, x1 - x2, y1 - y2);
}

// atan2() makes this function fairly slow, replaced by ~2x faster formula
function innerAngle2(ax, ay, bx, by, cx, cy) {
  var a1 = Math.atan2(ay - by, ax - bx),
      a2 = Math.atan2(cy - by, cx - bx),
      a3 = Math.abs(a1 - a2);
  if (a3 > Math.PI) {
    a3 = 2 * Math.PI - a3;
  }
  return a3;
}

// Return angle abc in range [0, 2PI) or NaN if angle is invalid
// (e.g. if length of ab or bc is 0)
/*
function signedAngle2(ax, ay, bx, by, cx, cy) {
  var a1 = Math.atan2(ay - by, ax - bx),
      a2 = Math.atan2(cy - by, cx - bx),
      a3 = a2 - a1;

  if (ax == bx && ay == by || bx == cx && by == cy) {
    a3 = NaN; // Use NaN for invalid angles
  } else if (a3 >= Math.PI * 2) {
    a3 = 2 * Math.PI - a3;
  } else if (a3 < 0) {
    a3 = a3 + 2 * Math.PI;
  }
  return a3;
}
*/

function standardAngle(a) {
  var twoPI = Math.PI * 2;
  while (a < 0) {
    a += twoPI;
  }
  while (a >= twoPI) {
    a -= twoPI;
  }
  return a;
}

function signedAngle(ax, ay, bx, by, cx, cy) {
  if (ax == bx && ay == by || bx == cx && by == cy) {
    return NaN; // Use NaN for invalid angles
  }
  var abx = ax - bx,
      aby = ay - by,
      cbx = cx - bx,
      cby = cy - by,
      dotp = abx * cbx + aby * cby,
      crossp = abx * cby - aby * cbx,
      a = Math.atan2(crossp, dotp);
  return standardAngle(a);
}

// Calc bearing in radians at lng1, lat1
function bearing(lng1, lat1, lng2, lat2) {
  var D2R = Math.PI / 180;
  lng1 *= D2R;
  lng2 *= D2R;
  lat1 *= D2R;
  lat2 *= D2R;
  var y = Math.sin(lng2-lng1) * Math.cos(lat2),
      x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(lng2-lng1);
  return Math.atan2(y, x);
}

// Calc angle of turn from ab to bc, in range [0, 2PI)
// Receive lat-lng values in degrees
function signedAngleSph(alng, alat, blng, blat, clng, clat) {
  if (alng == blng && alat == blat || blng == clng && blat == clat) {
    return NaN;
  }
  var b1 = bearing(blng, blat, alng, alat), // calc bearing at b
      b2 = bearing(blng, blat, clng, clat),
      a = Math.PI * 2 + b1 - b2;
  return standardAngle(a);
}

// Convert arrays of lng and lat coords (xsrc, ysrc) into
// x, y, z coords on the surface of a sphere with radius 6378137
// (the radius of spherical Earth datum in meters)
//
function convLngLatToSph(xsrc, ysrc, xbuf, ybuf, zbuf) {
  var deg2rad = Math.PI / 180,
      r = R;
  for (var i=0, len=xsrc.length; i<len; i++) {
    var lng = xsrc[i] * deg2rad,
        lat = ysrc[i] * deg2rad,
        cosLat = Math.cos(lat);
    xbuf[i] = Math.cos(lng) * cosLat * r;
    ybuf[i] = Math.sin(lng) * cosLat * r;
    zbuf[i] = Math.sin(lat) * r;
  }
}

// Haversine formula (well conditioned at small distances)
function sphericalDistance(lam1, phi1, lam2, phi2) {
  var dlam = lam2 - lam1,
      dphi = phi2 - phi1,
      a = Math.sin(dphi / 2) * Math.sin(dphi / 2) +
          Math.cos(phi1) * Math.cos(phi2) *
          Math.sin(dlam / 2) * Math.sin(dlam / 2),
      c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  return c;
}

// Receive: coords in decimal degrees;
// Return: distance in meters on spherical earth
function greatCircleDistance(lng1, lat1, lng2, lat2) {
  var D2R = Math.PI / 180,
      dist = sphericalDistance(lng1 * D2R, lat1 * D2R, lng2 * D2R, lat2 * D2R);
  return dist * R;
}

// TODO: make this safe for small angles
function innerAngle(ax, ay, bx, by, cx, cy) {
  var ab = distance2D(ax, ay, bx, by),
      bc = distance2D(bx, by, cx, cy),
      theta, dotp;
  if (ab === 0 || bc === 0) {
    theta = 0;
  } else {
    dotp = ((ax - bx) * (cx - bx) + (ay - by) * (cy - by)) / (ab * bc);
    if (dotp >= 1 - 1e-14) {
      theta = 0;
    } else if (dotp <= -1 + 1e-14) {
      theta = Math.PI;
    } else {
      theta = Math.acos(dotp); // consider using other formula at small dp
    }
  }
  return theta;
}

function innerAngle3D(ax, ay, az, bx, by, bz, cx, cy, cz) {
  var ab = distance3D(ax, ay, az, bx, by, bz),
      bc = distance3D(bx, by, bz, cx, cy, cz),
      theta, dotp;
  if (ab === 0 || bc === 0) {
    theta = 0;
  } else {
    dotp = ((ax - bx) * (cx - bx) + (ay - by) * (cy - by) + (az - bz) * (cz - bz)) / (ab * bc);
    if (dotp >= 1) {
      theta = 0;
    } else if (dotp <= -1) {
      theta = Math.PI;
    } else {
      theta = Math.acos(dotp); // consider using other formula at small dp
    }
  }
  return theta;
}

function triangleArea(ax, ay, bx, by, cx, cy) {
  var area = Math.abs(((ay - cy) * (bx - cx) + (by - cy) * (cx - ax)) / 2);
  return area;
}

function detSq(ax, ay, bx, by, cx, cy) {
  var det = ax * by - ax * cy + bx * cy - bx * ay + cx * ay - cx * by;
  return det * det;
}

function cosine(ax, ay, bx, by, cx, cy) {
  var den = distance2D(ax, ay, bx, by) * distance2D(bx, by, cx, cy),
      cos = 0;
  if (den > 0) {
    cos = ((ax - bx) * (cx - bx) + (ay - by) * (cy - by)) / den;
    if (cos > 1) cos = 1; // handle fp rounding error
    else if (cos < -1) cos = -1;
  }
  return cos;
}

function cosine3D(ax, ay, az, bx, by, bz, cx, cy, cz) {
  var den = distance3D(ax, ay, az, bx, by, bz) * distance3D(bx, by, bz, cx, cy, cz),
      cos = 0;
  if (den > 0) {
    cos = ((ax - bx) * (cx - bx) + (ay - by) * (cy - by) + (az - bz) * (cz - bz)) / den;
    if (cos > 1) cos = 1; // handle fp rounding error
    else if (cos < -1) cos = -1;
  }
  return cos;
}

function triangleArea3D(ax, ay, az, bx, by, bz, cx, cy, cz) {
  var area = 0.5 * Math.sqrt(detSq(ax, ay, bx, by, cx, cy) +
    detSq(ax, az, bx, bz, cx, cz) + detSq(ay, az, by, bz, cy, cz));
  return area;
}

// Given point B and segment AC, return the squared distance from B to the
// nearest point on AC
// Receive the squared length of segments AB, BC, AC
//
function apexDistSq(ab2, bc2, ac2) {
  var dist2;
  if (ac2 === 0) {
    dist2 = ab2;
  } else if (ab2 >= bc2 + ac2) {
    dist2 = bc2;
  } else if (bc2 >= ab2 + ac2) {
    dist2 = ab2;
  } else {
    var dval = (ab2 + ac2 - bc2);
    dist2 = ab2 -  dval * dval / ac2  * 0.25;
  }
  if (dist2 < 0) {
    dist2 = 0;
  }
  return dist2;
}

function pointSegDistSq(ax, ay, bx, by, cx, cy) {
  var ab2 = distanceSq(ax, ay, bx, by),
      ac2 = distanceSq(ax, ay, cx, cy),
      bc2 = distanceSq(bx, by, cx, cy);
  return apexDistSq(ab2, ac2, bc2);
}

function pointSegDistSq3D(ax, ay, az, bx, by, bz, cx, cy, cz) {
  var ab2 = distanceSq3D(ax, ay, az, bx, by, bz),
      ac2 = distanceSq3D(ax, ay, az, cx, cy, cz),
      bc2 = distanceSq3D(bx, by, bz, cx, cy, cz);
  return apexDistSq(ab2, ac2, bc2);
}

MapShaper.calcArcBounds = function(xx, yy, start, len) {
  var xmin = Infinity,
      ymin = Infinity,
      xmax = -Infinity,
      ymax = -Infinity,
      i = start | 0,
      n = isNaN(len) ? xx.length - i : len + i,
      x, y;
  for (; i<n; i++) {
    x = xx[i];
    y = yy[i];
    if (x < xmin) xmin = x;
    if (x > xmax) xmax = x;
    if (y < ymin) ymin = y;
    if (y > ymax) ymax = y;
  }
  if (xmin > xmax || ymin > ymax) {
    error("#calcArcBounds() null bounds");
  }
  return [xmin, ymin, xmax, ymax];
};

MapShaper.reversePathCoords = function(arr, start, len) {
  var i = start,
      j = start + len - 1,
      tmp;
  while (i < j) {
    tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
    i++;
    j--;
  }
};

// merge B into A
function mergeBounds(a, b) {
  if (b[0] < a[0]) a[0] = b[0];
  if (b[1] < a[1]) a[1] = b[1];
  if (b[2] > a[2]) a[2] = b[2];
  if (b[3] > a[3]) a[3] = b[3];
}

function containsBounds(a, b) {
  return a[0] <= b[0] && a[2] >= b[2] && a[1] <= b[1] && a[3] >= b[3];
}

function boundsArea(b) {
  return (b[2] - b[0]) * (b[3] - b[1]);
}

// export functions so they can be tested
utils.extend(geom, {
  R: R,
  D2R: D2R,
  degreesToMeters: degreesToMeters,
  getRoundingFunction: getRoundingFunction,
  segmentHit: segmentHit,
  segmentIntersection: segmentIntersection,
  distance3D: distance3D,
  innerAngle: innerAngle,
  innerAngle2: innerAngle2,
  signedAngle: signedAngle,
  bearing: bearing,
  signedAngleSph: signedAngleSph,
  standardAngle: standardAngle,
  convLngLatToSph: convLngLatToSph,
  sphericalDistance: sphericalDistance,
  greatCircleDistance: greatCircleDistance,
  pointSegDistSq: pointSegDistSq,
  pointSegDistSq3D: pointSegDistSq3D,
  innerAngle3D: innerAngle3D,
  triangleArea: triangleArea,
  triangleArea3D: triangleArea3D,
  cosine: cosine,
  cosine3D: cosine3D
});



// Constructor takes arrays of coords: xx, yy, zz (optional)
//
// Iterate over the points of an arc
// properties: x, y
// method: hasNext()
// usage:
//   while (iter.hasNext()) {
//     iter.x, iter.y; // do something w/ x & y
//   }
//
function ArcIter(xx, yy) {
  this._i = 0;
  this._inc = 1;
  this._stop = 0;
  this._xx = xx;
  this._yy = yy;
  this.i = 0;
  this.x = 0;
  this.y = 0;
}

ArcIter.prototype.init = function(i, len, fw) {
  if (fw) {
    this._i = i;
    this._inc = 1;
    this._stop = i + len;
  } else {
    this._i = i + len - 1;
    this._inc = -1;
    this._stop = i - 1;
  }
  return this;
};

ArcIter.prototype.hasNext = function() {
  var i = this._i;
  if (i == this._stop) return false;
  this._i = i + this._inc;
  this.x = this._xx[i];
  this.y = this._yy[i];
  this.i = i;
  return true;
};

function FilteredArcIter(xx, yy, zz) {
  var _zlim = 0,
      _i = 0,
      _inc = 1,
      _stop = 0;

  this.init = function(i, len, fw, zlim) {
    _zlim = zlim || 0;
    if (fw) {
      _i = i;
      _inc = 1;
      _stop = i + len;
    } else {
      _i = i + len - 1;
      _inc = -1;
      _stop = i - 1;
    }
    return this;
  };

  this.hasNext = function() {
    // using local vars is significantly faster when skipping many points
    var zarr = zz,
        i = _i,
        j = i,
        zlim = _zlim,
        stop = _stop,
        inc = _inc;
    if (i == stop) return false;
    do {
      j += inc;
    } while (j != stop && zarr[j] < zlim);
    _i = j;
    this.x = xx[i];
    this.y = yy[i];
    this.i = i;
    return true;
  };
}

// Iterate along a path made up of one or more arcs.
// Similar interface to ArcIter()
//
function ShapeIter(arcs) {
  this._arcs = arcs;
  this._i = 0;
  this._n = 0;
  this.x = 0;
  this.y = 0;
}

ShapeIter.prototype.hasNext = function() {
  var arc = this._arc;
  if (this._i >= this._n) {
    return false;
  } else if (arc.hasNext()) {
    this.x = arc.x;
    this.y = arc.y;
    return true;
  } else {
    this.nextArc();
    return this.hasNext();
  }
};

ShapeIter.prototype.init = function(ids) {
  this._ids = ids;
  this._n = ids.length;
  this.reset();
  return this;
};

ShapeIter.prototype.nextArc = function() {
  var i = this._i + 1;
  if (i < this._n) {
    this._arc = this._arcs.getArcIter(this._ids[i]);
    if (i > 0) this._arc.hasNext(); // skip first point
  }
  this._i = i;
};

ShapeIter.prototype.reset = function() {
  this._i = -1;
  this.nextArc();
};




// export for testing
MapShaper.ArcCollection = ArcCollection;
MapShaper.ArcIter = ArcIter;

// An interface for managing a collection of paths.
// Constructor signatures:
//
// ArcCollection(arcs)
//    arcs is an array of polyline arcs; each arc is an array of points: [[x0, y0], [x1, y1], ... ]
//
// ArcCollection(nn, xx, yy)
//    nn is an array of arc lengths; xx, yy are arrays of concatenated coords;
function ArcCollection() {
  var _xx, _yy,  // coordinates data
      _ii, _nn,  // indexes, sizes
      _zz, _zlimit = 0, // simplification
      _bb, _allBounds, // bounding boxes
      _arcIter, _filteredArcIter; // path iterators

  if (arguments.length == 1) {
    initLegacyArcs(arguments[0]);  // want to phase this out
  } else if (arguments.length == 3) {
    initXYData.apply(this, arguments);
  } else {
    error("ArcCollection() Invalid arguments");
  }

  function initLegacyArcs(arcs) {
    var xx = [], yy = [];
    var nn = arcs.map(function(points) {
      var n = points ? points.length : 0;
      for (var i=0; i<n; i++) {
        xx.push(points[i][0]);
        yy.push(points[i][1]);
      }
      return n;
    });
    initXYData(nn, xx, yy);
  }

  function initXYData(nn, xx, yy) {
    var size = nn.length;
    if (nn instanceof Array) nn = new Uint32Array(nn);
    if (xx instanceof Array) xx = new Float64Array(xx);
    if (yy instanceof Array) yy = new Float64Array(yy);
    _xx = xx;
    _yy = yy;
    _nn = nn;
    _zz = null;
    _filteredArcIter = null;

    // generate array of starting idxs of each arc
    _ii = new Uint32Array(size);
    for (var idx = 0, j=0; j<size; j++) {
      _ii[j] = idx;
      idx += nn[j];
    }

    if (idx != _xx.length || _xx.length != _yy.length) {
      error("ArcCollection#initXYData() Counting error");
    }

    initBounds();
    // Pre-allocate some path iterators for repeated use.
    _arcIter = new ArcIter(_xx, _yy);
    return this;
  }

  function initZData(zz) {
    if (!zz) {
      _zz = null;
      _filteredArcIter = null;
    } else {
      if (zz.length != _xx.length) error("ArcCollection#initZData() mismatched arrays");
      if (zz instanceof Array) zz = new Float64Array(zz);
      _zz = zz;
      _filteredArcIter = new FilteredArcIter(_xx, _yy, _zz);
    }
  }

  function initBounds() {
    var data = calcArcBounds(_xx, _yy, _nn);
    _bb = data.bb;
    _allBounds = data.bounds;
  }

  function calcArcBounds(xx, yy, nn) {
    var numArcs = nn.length,
        bb = new Float64Array(numArcs * 4),
        bounds = new Bounds(),
        arcOffs = 0,
        arcLen,
        j, b;
    for (var i=0; i<numArcs; i++) {
      arcLen = nn[i];
      if (arcLen > 0) {
        j = i * 4;
        b = MapShaper.calcArcBounds(xx, yy, arcOffs, arcLen);
        bb[j++] = b[0];
        bb[j++] = b[1];
        bb[j++] = b[2];
        bb[j] = b[3];
        arcOffs += arcLen;
        bounds.mergeBounds(b);
      }
    }
    return {
      bb: bb,
      bounds: bounds
    };
  }

  this.updateVertexData = function(nn, xx, yy, zz) {
    initXYData(nn, xx, yy);
    initZData(zz || null);
  };

  // Give access to raw data arrays...
  this.getVertexData = function() {
    return {
      xx: _xx,
      yy: _yy,
      zz: _zz,
      bb: _bb,
      nn: _nn,
      ii: _ii
    };
  };

  this.getCopy = function() {
    var copy = new ArcCollection(new Int32Array(_nn), new Float64Array(_xx),
        new Float64Array(_yy));
    if (_zz) copy.setThresholds(new Float64Array(_zz));
    return copy;
  };

  function getFilteredPointCount() {
    var zz = _zz, z = _zlimit;
    if (!zz || !z) return this.getPointCount();
    var count = 0;
    for (var i=0, n = zz.length; i<n; i++) {
      if (zz[i] >= z) count++;
    }
    return count;
  }

  function getFilteredVertexData() {
    var len2 = getFilteredPointCount();
    var arcCount = _nn.length;
    var xx2 = new Float64Array(len2),
        yy2 = new Float64Array(len2),
        zz2 = new Float64Array(len2),
        nn2 = new Int32Array(arcCount),
        i=0, i2 = 0,
        n, n2;

    for (var arcId=0; arcId < arcCount; arcId++) {
      n2 = 0;
      n = _nn[arcId];
      for (var end = i+n; i < end; i++) {
        if (_zz[i] >= _zlimit) {
          xx2[i2] = _xx[i];
          yy2[i2] = _yy[i];
          zz2[i2] = _zz[i];
          i2++;
          n2++;
        }
      }
      if (n2 < 2) error("Collapsed arc"); // endpoints should be z == Infinity
      nn2[arcId] = n2;
    }
    return {
      xx: xx2,
      yy: yy2,
      zz: zz2,
      nn: nn2
    };
  }

  this.getFilteredCopy = function() {
    if (!_zz || _zlimit === 0) return this.getCopy();
    var data = getFilteredVertexData();
    var copy = new ArcCollection(data.nn, data.xx, data.yy);
    copy.setThresholds(data.zz);
    return copy;
  };

  // Return arcs as arrays of [x, y] points (intended for testing).
  this.toArray = function() {
    var arr = [];
    this.forEach(function(iter) {
      var arc = [];
      while (iter.hasNext()) {
        arc.push([iter.x, iter.y]);
      }
      arr.push(arc);
    });
    return arr;
  };

  this.toString = function() {
    return JSON.stringify(this.toArray());
  };

  // Snap coordinates to a grid of @quanta locations on both axes
  // This may snap nearby points to the same coordinates.
  // Consider a cleanup pass to remove dupes, make sure collapsed arcs are
  //   removed on export.
  //
  this.quantize = function(quanta) {
    var bb1 = this.getBounds(),
        bb2 = new Bounds(0, 0, quanta-1, quanta-1),
        transform = bb1.getTransform(bb2),
        inverse = transform.invert();

    this.applyTransform(transform, true);
    this.applyTransform(inverse);
  };

  // Return average segment length (with simplification)
  this.getAvgSegment = function() {
    var sum = 0;
    var count = this.forEachSegment(function(i, j, xx, yy) {
      var dx = xx[i] - xx[j],
          dy = yy[i] - yy[j];
      sum += Math.sqrt(dx * dx + dy * dy);
    });
    return sum / count || 0;
  };

  // Return average magnitudes of dx, dy (with simplification)
  this.getAvgSegment2 = function() {
    var dx = 0, dy = 0;
    var count = this.forEachSegment(function(i, j, xx, yy) {
      dx += Math.abs(xx[i] - xx[j]);
      dy += Math.abs(yy[i] - yy[j]);
    });
    return [dx / count || 0, dy / count || 0];
  };

  // Return average magnitudes of dx, dy (with simplification)
  /*
  this.getAvgSegmentSph2 = function() {
    var sumx = 0, sumy = 0;
    var count = this.forEachSegment(function(i, j, xx, yy) {
      var lat1 = yy[i],
          lat2 = yy[j];
      sumy += geom.degreesToMeters(Math.abs(lat1 - lat2));
      sumx += geom.degreesToMeters(Math.abs(xx[i] - xx[j]) *
          Math.cos((lat1 + lat2) * 0.5 * geom.D2R);
    });
    return [sumx / count || 0, sumy / count || 0];
  };
  */

  // @cb function(i, j, xx, yy)
  this.forEachArcSegment = function(arcId, cb) {
    var fw = arcId >= 0,
        absId = fw ? arcId : ~arcId,
        zlim = this.getRetainedInterval(),
        n = _nn[absId],
        i = fw ? _ii[absId] : _ii[absId] + n - 1,
        step = fw ? 1 : -1,
        count = 0,
        prev;

    for (var j = 0; j < n; j++, i += step) {
      if (zlim === 0 || _zz[i] >= zlim) {
        if (j > 0) {
          cb(prev, i, _xx, _yy);
          count++;
        }
        prev = i;
      }
    }
    return count;
  };

  // @cb function(i, j, xx, yy)
  this.forEachSegment = function(cb) {
    var count = 0;
    for (var i=0, n=this.size(); i<n; i++) {
      count += this.forEachArcSegment(i, cb);
    }
    return count;
  };

  // Apply a linear transform to the data, with or without rounding.
  //
  this.applyTransform = function(t, round) {
    var xx = _xx, yy = _yy, x, y;
    if (round && typeof round != 'function') {
      round = Math.round;
    }
    if (!t) {
      t = new Transform(); // null transform
    }
    for (var i=0, n=xx.length; i<n; i++) {
      x = xx[i] * t.mx + t.bx;
      y = yy[i] * t.my + t.by;
      if (round) {
        x = round(x);
        y = round(y);
      }
      xx[i] = x;
      yy[i] = y;
    }
    initBounds();
  };

  // Return an ArcIter object for each path in the dataset
  //
  this.forEach = function(cb) {
    for (var i=0, n=this.size(); i<n; i++) {
      cb(this.getArcIter(i), i);
    }
  };

  // Iterate over arcs with access to low-level data
  //
  this.forEach2 = function(cb) {
    for (var arcId=0, n=this.size(); arcId<n; arcId++) {
      cb(_ii[arcId], _nn[arcId], _xx, _yy, _zz, arcId);
    }
  };

  this.forEach3 = function(cb) {
    var start, end, xx, yy, zz;
    for (var arcId=0, n=this.size(); arcId<n; arcId++) {
      start = _ii[arcId];
      end = start + _nn[arcId];
      xx = _xx.subarray(start, end);
      yy = _yy.subarray(start, end);
      if (_zz) zz = _zz.subarray(start, end);
      cb(xx, yy, zz, arcId);
    }
  };

  // Remove arcs that don't pass a filter test and re-index arcs
  // Return array mapping original arc ids to re-indexed ids. If arr[n] == -1
  // then arc n was removed. arr[n] == m indicates that the arc at n was
  // moved to index m.
  // Return null if no arcs were re-indexed (and no arcs were removed)
  //
  this.filter = function(cb) {
    var map = new Int32Array(this.size()),
        goodArcs = 0,
        goodPoints = 0;
    for (var i=0, n=this.size(); i<n; i++) {
      if (cb(this.getArcIter(i), i)) {
        map[i] = goodArcs++;
        goodPoints += _nn[i];
      } else {
        map[i] = -1;
      }
    }
    if (goodArcs === this.size()) {
      return null;
    } else {
      condenseArcs(map);
      if (goodArcs === 0) {
        // no remaining arcs
      }
      return map;
    }
  };

  function condenseArcs(map) {
    var goodPoints = 0,
        goodArcs = 0,
        copyElements = MapShaper.copyElements,
        k, arcLen;
    for (var i=0, n=map.length; i<n; i++) {
      k = map[i];
      arcLen = _nn[i];
      if (k > -1) {
        copyElements(_xx, _ii[i], _xx, goodPoints, arcLen);
        copyElements(_yy, _ii[i], _yy, goodPoints, arcLen);
        if (_zz) copyElements(_zz, _ii[i], _zz, goodPoints, arcLen);
        _nn[k] = arcLen;
        goodPoints += arcLen;
        goodArcs++;
      }
    }

    initXYData(_nn.subarray(0, goodArcs), _xx.subarray(0, goodPoints),
        _yy.subarray(0, goodPoints));
    if (_zz) initZData(_zz.subarray(0, goodPoints));
  }

  this.dedupCoords = function() {
    var arcId = 0, i = 0, i2 = 0,
        arcCount = this.size(),
        zz = _zz,
        arcLen, arcLen2;
    while (arcId < arcCount) {
      arcLen = _nn[arcId];
      arcLen2 = MapShaper.dedupArcCoords(i, i2, arcLen, _xx, _yy, zz);
      _nn[arcId] = arcLen2;
      i += arcLen;
      i2 += arcLen2;
      arcId++;
    }
    if (i > i2) {
      initXYData(_nn, _xx.subarray(0, i2), _yy.subarray(0, i2));
      if (zz) initZData(zz.subarray(0, i2));
    }
    return i - i2;
  };

  this.getVertex = function(arcId, nth) {
    var i = this.indexOfVertex(arcId, nth);
    return {
      x: _xx[i],
      y: _yy[i]
    };
  };

  this.indexOfVertex = function(arcId, nth) {
    var absId = arcId < 0 ? ~arcId : arcId,
        len = _nn[absId];
    if (nth < 0) nth = len + nth;
    if (absId != arcId) nth = len - nth - 1;
    if (nth < 0 || nth >= len) error("[ArcCollection] out-of-range vertex id");
    return _ii[absId] + nth;
  };

  // Test whether the vertex at index @idx is the endpoint of an arc
  this.pointIsEndpoint = function(idx) {
    var ii = _ii,
        nn = _nn;
    for (var j=0, n=ii.length; j<n; j++) {
      if (idx === ii[j] || idx === ii[j] + nn[j] - 1) return true;
    }
    return false;
  };

  // Tests if arc endpoints have same x, y coords
  // (arc may still have collapsed);
  this.arcIsClosed = function(arcId) {
    var i = this.indexOfVertex(arcId, 0),
        j = this.indexOfVertex(arcId, -1);
    return i != j && _xx[i] == _xx[j] && _yy[i] == _yy[j];
  };

  // Tests if first and last segments mirror each other
  // A 3-vertex arc with same endpoints tests true
  this.arcIsLollipop = function(arcId) {
    var len = this.getArcLength(arcId),
        i, j;
    if (len <= 2 || !this.arcIsClosed(arcId)) return false;
    i = this.indexOfVertex(arcId, 1);
    j = this.indexOfVertex(arcId, -2);
    return _xx[i] == _xx[j] && _yy[i] == _yy[j];
  };

  this.arcIsDegenerate = function(arcId) {
    var iter = this.getArcIter(arcId);
    var i = 0,
        x, y;
    while (iter.hasNext()) {
      if (i > 0) {
        if (x != iter.x || y != iter.y) return false;
      }
      x = iter.x;
      y = iter.y;
      i++;
    }
    return true;
  };

  this.getArcLength = function(arcId) {
    return _nn[absArcId(arcId)];
  };

  this.getArcIter = function(arcId) {
    var fw = arcId >= 0,
        i = fw ? arcId : ~arcId,
        iter = _zz && _zlimit ? _filteredArcIter : _arcIter;
    if (i >= _nn.length) {
      error("#getArcId() out-of-range arc id:", arcId);
    }
    return iter.init(_ii[i], _nn[i], fw, _zlimit);
  };

  this.getShapeIter = function(ids) {
    return new ShapeIter(this).init(ids);
  };

  // Add simplification data to the dataset
  // @thresholds is either a single typed array or an array of arrays of removal thresholds for each arc;
  //
  this.setThresholds = function(thresholds) {
    var n = this.getPointCount(),
        zz = null;
    if (!thresholds) {
      // nop
    } else if (thresholds.length == n) {
      zz = thresholds;
    } else if (thresholds.length == this.size()) {
      zz = flattenThresholds(thresholds, n);
    } else {
      error("Invalid threshold data");
    }
    initZData(zz);
    return this;
  };

  function flattenThresholds(arr, n) {
    var zz = new Float64Array(n),
        i = 0;
    arr.forEach(function(arr) {
      for (var j=0, n=arr.length; j<n; i++, j++) {
        zz[i] = arr[j];
      }
    });
    if (i != n) error("Mismatched thresholds");
    return zz;
  }

  // bake in current simplification level, if any
  this.flatten = function() {
    if (_zlimit > 0) {
      var data = getFilteredVertexData();
      this.updateVertexData(data.nn, data.xx, data.yy);
      _zlimit = 0;
    } else {
      _zz = null;
    }
  };

  this.getRetainedInterval = function() {
    return _zlimit;
  };

  this.setRetainedInterval = function(z) {
    _zlimit = z;
    return this;
  };

  this.getRetainedPct = function() {
    return this.getPctByThreshold(_zlimit);
  };

  this.setRetainedPct = function(pct) {
    if (pct >= 1) {
      _zlimit = 0;
    } else {
      _zlimit = this.getThresholdByPct(pct);
      _zlimit = MapShaper.clampIntervalByPct(_zlimit, pct);
    }
    return this;
  };

  // Return array of z-values that can be removed for simplification
  //
  this.getRemovableThresholds = function(nth) {
    if (!_zz) error("[arcs] Missing simplification data.");
    var skip = nth | 1,
        arr = new Float64Array(Math.ceil(_zz.length / skip)),
        z;
    for (var i=0, j=0, n=this.getPointCount(); i<n; i+=skip) {
      z = _zz[i];
      if (z != Infinity) {
        arr[j++] = z;
      }
    }
    return arr.subarray(0, j);
  };

  this.getArcThresholds = function(arcId) {
    if (!(arcId >= 0 && arcId < this.size())) {
      error("[arcs] Invalid arc id:", arcId);
    }
    var start = _ii[arcId],
        end = start + _nn[arcId];
    return _zz.subarray(start, end);
  };

  this.getPctByThreshold = function(val) {
    var arr, rank, pct;
    if (val > 0) {
      arr = this.getRemovableThresholds();
      rank = utils.findRankByValue(arr, val);
      pct = arr.length > 0 ? 1 - (rank - 1) / arr.length : 1;
    } else {
      pct = 1;
    }
    return pct;
  };

  this.getThresholdByPct = function(pct) {
    var tmp = this.getRemovableThresholds(),
        rank, z;
    if (tmp.length === 0) { // No removable points
      rank = 0;
    } else {
      rank = Math.floor((1 - pct) * (tmp.length + 2));
    }

    if (rank <= 0) {
      z = 0;
    } else if (rank > tmp.length) {
      z = Infinity;
    } else {
      z = utils.findValueByRank(tmp, rank);
    }
    return z;
  };

  this.arcIntersectsBBox = function(i, b1) {
    var b2 = _bb,
        j = i * 4;
    return b2[j] <= b1[2] && b2[j+2] >= b1[0] && b2[j+3] >= b1[1] && b2[j+1] <= b1[3];
  };

  this.arcIsContained = function(i, b1) {
    var b2 = _bb,
        j = i * 4;
    return b2[j] >= b1[0] && b2[j+2] <= b1[2] && b2[j+1] >= b1[1] && b2[j+3] <= b1[3];
  };

  this.arcIsSmaller = function(i, units) {
    var bb = _bb,
        j = i * 4;
    return bb[j+2] - bb[j] < units && bb[j+3] - bb[j+1] < units;
  };

  // TODO: allow datasets in lat-lng coord range to be flagged as planar
  this.isPlanar = function() {
    return !MapShaper.probablyDecimalDegreeBounds(this.getBounds());
  };

  this.size = function() {
    return _ii && _ii.length || 0;
  };

  this.getPointCount = function() {
    return _xx && _xx.length || 0;
  };

  this.getBounds = function() {
    return _allBounds;
  };

  this.getSimpleShapeBounds = function(arcIds, bounds) {
    bounds = bounds || new Bounds();
    for (var i=0, n=arcIds.length; i<n; i++) {
      this.mergeArcBounds(arcIds[i], bounds);
    }
    return bounds;
  };

  this.getSimpleShapeBounds2 = function(arcIds, arr) {
    var bbox = arr || [],
        bb = _bb,
        id = absArcId(arcIds[0]) * 4;
    bbox[0] = bb[id];
    bbox[1] = bb[++id];
    bbox[2] = bb[++id];
    bbox[3] = bb[++id];
    for (var i=1, n=arcIds.length; i<n; i++) {
      id = absArcId(arcIds[i]) * 4;
      if (bb[id] < bbox[0]) bbox[0] = bb[id];
      if (bb[++id] < bbox[1]) bbox[1] = bb[id];
      if (bb[++id] > bbox[2]) bbox[2] = bb[id];
      if (bb[++id] > bbox[3]) bbox[3] = bb[id];
    }
    return bbox;
  };

  this.getMultiShapeBounds = function(shapeIds, bounds) {
    bounds = bounds || new Bounds();
    if (shapeIds) { // handle null shapes
      for (var i=0, n=shapeIds.length; i<n; i++) {
        this.getSimpleShapeBounds(shapeIds[i], bounds);
      }
    }
    return bounds;
  };

  this.mergeArcBounds = function(arcId, bounds) {
    if (arcId < 0) arcId = ~arcId;
    var offs = arcId * 4;
    bounds.mergeBounds(_bb[offs], _bb[offs+1], _bb[offs+2], _bb[offs+3]);
  };
}

ArcCollection.prototype.inspect = function() {
  var n = this.getPointCount(), str;
  if (n < 50) {
    str = JSON.stringify(this.toArray());
  } else {
    str = '[ArcCollection (' + this.size() + ')]';
  }
  return str;
};

MapShaper.dedupArcCoords = function(src, dest, arcLen, xx, yy, zz) {
  var n = 0, n2 = 0; // counters
  while (n < arcLen) {
    if (n === 0 || xx[src] != xx[src-1] || yy[src] != yy[src-1]) {
      xx[dest] = xx[src];
      yy[dest] = yy[src];
      if (zz) zz[dest] = zz[src];
      dest++;
      n2++;
    } else if (n > 0 && zz && zz[src] > zz[dest]) {
      zz[dest-1] = zz[src];
    }
    src++;
    n++;
  }
  return n2 > 1 ? n2 : 0;
};




// Utility functions for working with ArcCollection and arrays of arc ids.

// @counts A typed array for accumulating count of each abs arc id
//   (assume it won't overflow)
MapShaper.countArcsInShapes = function(shapes, counts) {
  MapShaper.traverseShapes(shapes, null, function(obj) {
    var arcs = obj.arcs,
        id;
    for (var i=0; i<arcs.length; i++) {
      id = arcs[i];
      if (id < 0) id = ~id;
      counts[id]++;
    }
  });
};

MapShaper.countPointsInLayer = function(lyr) {
  var count = 0;
  if (MapShaper.layerHasPoints(lyr)) {
    MapShaper.forEachPoint(lyr, function() {count++;});
  }
  return count;
};

// Returns subset of shapes in @shapes that contain one or more arcs in @arcIds
MapShaper.findShapesByArcId = function(shapes, arcIds, numArcs) {
  var index = numArcs ? new Uint8Array(numArcs) : [],
      found = [];
  arcIds.forEach(function(id) {
    index[absArcId(id)] = 1;
  });
  shapes.forEach(function(shp, shpId) {
    var isHit = false;
    MapShaper.forEachArcId(shp || [], function(id) {
      isHit = isHit || index[absArcId(id)] == 1;
    });
    if (isHit) {
      found.push(shpId);
    }
  });
  return found;
};

// @shp An element of the layer.shapes array
//   (may be null, or, depending on layer type, an array of points or an array of arrays of arc ids)
MapShaper.cloneShape = function(shp) {
  if (!shp) return null;
  return shp.map(function(part) {
    return part.concat();
  });
};

MapShaper.cloneShapes = function(arr) {
  return utils.isArray(arr) ? arr.map(MapShaper.cloneShape) : null;
};

// a and b are arrays of arc ids
MapShaper.pathsAreIdentical = function(a, b) {
  if (a.length != b.length) return false;
  for (var i=0, n=a.length; i<n; i++) {
    if (a[i] != b[i]) return false;
  }
  return true;
};

MapShaper.reversePath = function(ids) {
  ids.reverse();
  for (var i=0, n=ids.length; i<n; i++) {
    ids[i] = ~ids[i];
  }
};

MapShaper.clampIntervalByPct = function(z, pct) {
  if (pct <= 0) z = Infinity;
  else if (pct >= 1) z = 0;
  return z;
};

MapShaper.findNextRemovableVertices = function(zz, zlim, start, end) {
  var i = MapShaper.findNextRemovableVertex(zz, zlim, start, end),
      arr, k;
  if (i > -1) {
    k = zz[i];
    arr = [i];
    while (++i < end) {
      if (zz[i] == k) {
        arr.push(i);
      }
    }
  }
  return arr || null;
};

// Return id of the vertex between @start and @end with the highest
// threshold that is less than @zlim, or -1 if none
//
MapShaper.findNextRemovableVertex = function(zz, zlim, start, end) {
  var tmp, jz = 0, j = -1, z;
  if (start > end) {
    tmp = start;
    start = end;
    end = tmp;
  }
  for (var i=start+1; i<end; i++) {
    z = zz[i];
    if (z < zlim && z > jz) {
      j = i;
      jz = z;
    }
  }
  return j;
};

MapShaper.forEachPoint = function(lyr, cb) {
  if (lyr.geometry_type != 'point') {
    error("[forEachPoint()] Expects a point layer");
  }
  lyr.shapes.forEach(function(shape, id) {
    var n = shape ? shape.length : 0;
    for (var i=0; i<n; i++) {
      cb(shape[i], id);
    }
  });
};

// Visit each arc id in a shape (array of array of arc ids)
// Use non-undefined return values of callback @cb as replacements.
MapShaper.forEachArcId = function(arr, cb) {
  var item;
  for (var i=0; i<arr.length; i++) {
    item = arr[i];
    if (item instanceof Array) {
      MapShaper.forEachArcId(item, cb);
    } else if (utils.isInteger(item)) {
      var val = cb(item);
      if (val !== void 0) {
        arr[i] = val;
      }
    } else if (item) {
      error("Non-integer arc id in:", arr);
    }
  }
};

MapShaper.forEachPath = function(paths, cb) {
  MapShaper.editPaths(paths, cb);
};

// @cb: function(path, i, paths)
//
MapShaper.editPaths = function(paths, cb) {
  if (!paths) return null; // null shape
  if (!utils.isArray(paths)) error("[editPaths()] Expected an array, found:", arr);
  var nulls = 0,
      n = paths.length,
      retn;

  for (var i=0; i<n; i++) {
    retn = cb(paths[i], i, paths);
    if (retn === null) {
      nulls++;
      paths[i] = null;
    } else if (utils.isArray(retn)) {
      paths[i] = retn;
    }
  }
  if (nulls == n) {
    return null;
  } else if (nulls > 0) {
    return paths.filter(function(ids) {return !!ids;});
  } else {
    return paths;
  }
};

MapShaper.forEachPathSegment = function(shape, arcs, cb) {
  MapShaper.forEachArcId(shape, function(arcId) {
    arcs.forEachArcSegment(arcId, cb);
  });
};

MapShaper.traverseShapes = function traverseShapes(shapes, cbArc, cbPart, cbShape) {
  var segId = 0;
  shapes.forEach(function(parts, shapeId) {
    if (!parts || parts.length === 0) return; // null shape
    var arcIds, arcId;
    if (cbShape) {
      cbShape(shapeId);
    }
    for (var i=0, m=parts.length; i<m; i++) {
      arcIds = parts[i];
      if (cbPart) {
        cbPart({
          i: i,
          shapeId: shapeId,
          shape: parts,
          arcs: arcIds
        });
      }

      if (cbArc) {
        for (var j=0, n=arcIds.length; j<n; j++, segId++) {
          arcId = arcIds[j];
          cbArc({
            i: j,
            shapeId: shapeId,
            partId: i,
            arcId: arcId,
            segId: segId
          });
        }
      }
    }
  });
};

MapShaper.arcHasLength = function(id, coords) {
  var iter = coords.getArcIter(id), x, y;
  if (iter.hasNext()) {
    x = iter.x;
    y = iter.y;
    while (iter.hasNext()) {
      if (iter.x != x || iter.y != y) return true;
    }
  }
  return false;
};

MapShaper.filterEmptyArcs = function(shape, coords) {
  if (!shape) return null;
  var shape2 = [];
  shape.forEach(function(ids) {
    var path = [];
    for (var i=0; i<ids.length; i++) {
      if (MapShaper.arcHasLength(ids[i], coords)) {
        path.push(ids[i]);
      }
    }
    if (path.length > 0) shape2.push(path);
  });
  return shape2.length > 0 ? shape2 : null;
};

// Bundle holes with their containing rings for Topo/GeoJSON polygon export.
// Assumes outer rings are CW and inner (hole) rings are CCW.
// @paths array of objects with path metadata -- see MapShaper.exportPathData()
//
// TODO: Improve reliability. Currently uses winding order, area and bbox to
//   identify holes and their enclosures -- could be confused by strange
//   geometry.
//
MapShaper.groupPolygonRings = function(paths) {
  var pos = [],
      neg = [];
  if (paths) {
    paths.forEach(function(path) {
      if (path.area > 0) {
        pos.push(path);
      } else if (path.area < 0) {
        neg.push(path);
      } else {
        // verbose("Zero-area ring, skipping");
      }
    });
  }

  var output = pos.map(function(part) {
    return [part];
  });

  neg.forEach(function(hole) {
    var containerId = -1,
        containerArea = 0;
    for (var i=0, n=pos.length; i<n; i++) {
      var part = pos[i],
          contained = part.bounds.contains(hole.bounds) && part.area > -hole.area;
      if (contained && (containerArea === 0 || part.area < containerArea)) {
        containerArea = part.area;
        containerId = i;
      }
    }
    if (containerId == -1) {
      verbose("[groupPolygonRings()] polygon hole is missing a containing ring, dropping.");
    } else {
      output[containerId].push(hole);
    }
  });
  return output;
};

MapShaper.getPathMetadata = function(shape, arcs, type) {
  return (shape || []).map(function(ids) {
    if (!utils.isArray(ids)) throw new Error("expected array");
    return {
      ids: ids,
      area: type == 'polygon' ? geom.getPlanarPathArea(ids, arcs) : 0,
      bounds: arcs.getSimpleShapeBounds(ids)
    };
  });
};




// utility functions for datasets and layers

// clone all layers, make a filtered copy of arcs
MapShaper.copyDataset = function(dataset) {
  var d2 = utils.extend({}, dataset);
  d2.layers = d2.layers.map(MapShaper.copyLayer);
  if (d2.arcs) {
    d2.arcs = d2.arcs.getFilteredCopy();
  }
  return d2;
};

// make a stub copy if the no_replace option is given, else pass thru src layer
MapShaper.getOutputLayer = function(src, opts) {
  return opts && opts.no_replace ? {geometry_type: src.geometry_type} : src;
};

// Make a deep copy of a layer
MapShaper.copyLayer = function(lyr) {
  var copy = utils.extend({}, lyr);
  if (lyr.data) {
    copy.data = lyr.data.clone();
  }
  if (lyr.shapes) {
    copy.shapes = MapShaper.cloneShapes(lyr.shapes);
  }
  return copy;
};

MapShaper.getDatasetBounds = function(data) {
  var bounds = new Bounds();
  data.layers.forEach(function(lyr) {
    var lyrbb = MapShaper.getLayerBounds(lyr, data.arcs);
    if (lyrbb) bounds.mergeBounds(lyrbb);
  });
  return bounds;
};

MapShaper.datasetHasPaths = function(dataset) {
  return utils.some(dataset.layers, function(lyr) {
    return MapShaper.layerHasPaths(lyr);
  });
};

MapShaper.getFeatureCount = function(lyr) {
  var count = 0;
  if (lyr.data) {
    count = lyr.data.size();
  } else if (lyr.shapes) {
    count = lyr.shapes.length;
  }
  return count;
};

MapShaper.getLayerBounds = function(lyr, arcs) {
  var bounds = null;
  if (lyr.geometry_type == 'point') {
    bounds = new Bounds();
    MapShaper.forEachPoint(lyr, function(p) {
      bounds.mergePoint(p[0], p[1]);
    });
  } else if (lyr.geometry_type == 'polygon' || lyr.geometry_type == 'polyline') {
    bounds = MapShaper.getPathBounds(lyr.shapes, arcs);
  } else {
    // just return null if layer has no bounds
    // error("Layer is missing a valid geometry type");
  }
  return bounds;
};

MapShaper.getPathBounds = function(shapes, arcs) {
  var bounds = new Bounds();
  MapShaper.forEachArcId(shapes, function(id) {
    arcs.mergeArcBounds(id, bounds);
  });
  return bounds;
};

// replace cut layers in-sequence (to maintain layer indexes)
// append any additional new layers
MapShaper.replaceLayers = function(dataset, cutLayers, newLayers) {
  // modify a copy in case cutLayers == dataset.layers
  var currLayers = dataset.layers.concat();
  utils.repeat(Math.max(cutLayers.length, newLayers.length), function(i) {
    var cutLyr = cutLayers[i],
        newLyr = newLayers[i],
        idx = cutLyr ? currLayers.indexOf(cutLyr) : currLayers.length;

    if (cutLyr) {
      currLayers.splice(idx, 1);
    }
    if (newLyr) {
      currLayers.splice(idx, 0, newLyr);
    }
  });
  dataset.layers = currLayers;
};

MapShaper.isolateLayer = function(layer, dataset) {
  return utils.defaults({
    layers: dataset.layers.filter(function(lyr) {return lyr == layer;})
  }, dataset);
};

// @target is a layer identifier or a comma-sep. list of identifiers
// an identifier is a literal name, a name containing "*" wildcard or
// a 0-based array index
MapShaper.findMatchingLayers = function(layers, target) {
  var ii = [];
  String(target).split(',').forEach(function(id) {
    var i = Number(id),
        rxp = utils.wildcardToRegExp(id);
    if (utils.isInteger(i)) {
      ii.push(i); // TODO: handle out-of-range index
    } else {
      layers.forEach(function(lyr, i) {
        if (rxp.test(lyr.name)) ii.push(i);
      });
    }
  });

  ii = utils.uniq(ii); // remove dupes
  return ii.map(function(i) {
    return layers[i];
  });
};




// Convert an array of intersections into an ArcCollection (for display)
//
MapShaper.getIntersectionPoints = function(intersections) {
  return intersections.map(function(obj) {
        return [obj.x, obj.y];
      });
};

// Identify intersecting segments in an ArcCollection
//
// To find all intersections:
// 1. Assign each segment to one or more horizontal stripes/bins
// 2. Find intersections inside each stripe
// 3. Concat and dedup
//
MapShaper.findSegmentIntersections = (function() {

  // Re-use buffer for temp data -- Chrome's gc starts bogging down
  // if large buffers are repeatedly created.
  var buf;
  function getUint32Array(count) {
    var bytes = count * 4;
    if (!buf || buf.byteLength < bytes) {
      buf = new ArrayBuffer(bytes);
    }
    return new Uint32Array(buf, 0, count);
  }

  return function(arcs) {
    var bounds = arcs.getBounds(),
        // TODO: handle spherical bounds
        spherical = !arcs.isPlanar() &&
            containsBounds(MapShaper.getWorldBounds(), bounds.toArray()),
        ymin = bounds.ymin,
        yrange = bounds.ymax - ymin,
        stripeCount = MapShaper.calcSegmentIntersectionStripeCount(arcs),
        stripeSizes = new Uint32Array(stripeCount),
        stripeId = stripeCount > 1 ? multiStripeId : singleStripeId,
        i;

    function multiStripeId(y) {
      return Math.floor((stripeCount-1) * (y - ymin) / yrange);
    }

    function singleStripeId(y) {return 0;}

    // Count segments in each stripe
    arcs.forEachSegment(function(id1, id2, xx, yy) {
      var s1 = stripeId(yy[id1]),
          s2 = stripeId(yy[id2]);
      while (true) {
        stripeSizes[s1] = stripeSizes[s1] + 2;
        if (s1 == s2) break;
        s1 += s2 > s1 ? 1 : -1;
      }
    });

    // Allocate arrays for segments in each stripe
    var stripeData = getUint32Array(utils.sum(stripeSizes)),
        offs = 0;
    var stripes = [];
    utils.forEach(stripeSizes, function(stripeSize) {
      var start = offs;
      offs += stripeSize;
      stripes.push(stripeData.subarray(start, offs));
    });
    // Assign segment ids to each stripe
    utils.initializeArray(stripeSizes, 0);

    arcs.forEachSegment(function(id1, id2, xx, yy) {
      var s1 = stripeId(yy[id1]),
          s2 = stripeId(yy[id2]),
          count, stripe;
      while (true) {
        count = stripeSizes[s1];
        stripeSizes[s1] = count + 2;
        stripe = stripes[s1];
        stripe[count] = id1;
        stripe[count+1] = id2;
        if (s1 == s2) break;
        s1 += s2 > s1 ? 1 : -1;
      }
    });

    // Detect intersections among segments in each stripe.
    var raw = arcs.getVertexData(),
        intersections = [],
        arr;
    for (i=0; i<stripeCount; i++) {
      arr = MapShaper.intersectSegments(stripes[i], raw.xx, raw.yy, spherical);
      if (arr.length > 0) {
        intersections.push.apply(intersections, arr);
      }
    }
    return MapShaper.dedupIntersections(intersections);
  };
})();

MapShaper.sortIntersections = function(arr) {
  arr.sort(function(a, b) {
    return a.x - b.x || a.y - b.y;
  });
};

MapShaper.dedupIntersections = function(arr) {
  var index = {};
  return arr.filter(function(o) {
    var key = MapShaper.getIntersectionKey(o);
    if (key in index) {
      return false;
    }
    index[key] = true;
    return true;
  });
};

// Get an indexable key from an intersection object
// Assumes that vertex ids of o.a and o.b are sorted
MapShaper.getIntersectionKey = function(o) {
  return o.a.join(',') + ';' + o.b.join(',');
};

MapShaper.calcSegmentIntersectionStripeCount = function(arcs) {
  var yrange = arcs.getBounds().height(),
      segLen = arcs.getAvgSegment2()[1],
      count = 1;
  if (segLen > 0 && yrange > 0) {
    count = Math.ceil(yrange / segLen / 20);
  }
  return count || 1;
};

// Find intersections among a group of line segments
//
// TODO: handle case where a segment starts and ends at the same point (i.e. duplicate coords);
//
// @ids: Array of indexes: [s0p0, s0p1, s1p0, s1p1, ...] where xx[sip0] <= xx[sip1]
// @xx, @yy: Arrays of x- and y-coordinates
//
MapShaper.intersectSegments = function(ids, xx, yy, spherical) {
  var lim = ids.length - 2,
      intersections = [];
  var s1p1, s1p2, s2p1, s2p2,
      s1p1x, s1p2x, s2p1x, s2p2x,
      s1p1y, s1p2y, s2p1y, s2p2y,
      hit, seg1, seg2, i, j;

  // Sort segments by xmin, to allow efficient exclusion of segments with
  // non-overlapping x extents.
  MapShaper.sortSegmentIds(xx, ids); // sort by ascending xmin

  i = 0;
  while (i < lim) {
    s1p1 = ids[i];
    s1p2 = ids[i+1];
    s1p1x = xx[s1p1];
    s1p2x = xx[s1p2];
    s1p1y = yy[s1p1];
    s1p2y = yy[s1p2];
    // count++;

    j = i;
    while (j < lim) {
      j += 2;
      s2p1 = ids[j];
      s2p1x = xx[s2p1];

      if (s1p2x < s2p1x) break; // x extent of seg 2 is greater than seg 1: done with seg 1
      //if (s1p2x <= s2p1x) break; // this misses point-segment intersections when s1 or s2 is vertical

      s2p1y = yy[s2p1];
      s2p2 = ids[j+1];
      s2p2x = xx[s2p2];
      s2p2y = yy[s2p2];

      // skip segments with non-overlapping y ranges
      if (s1p1y >= s2p1y) {
        if (s1p1y > s2p2y && s1p2y > s2p1y && s1p2y > s2p2y) continue;
      } else {
        if (s1p1y < s2p2y && s1p2y < s2p1y && s1p2y < s2p2y) continue;
      }

      // skip segments that are adjacent in a path (optimization)
      // TODO: consider if this eliminates some cases that should
      // be detected, e.g. spikes formed by unequal segments
      if (s1p1 == s2p1 || s1p1 == s2p2 || s1p2 == s2p1 || s1p2 == s2p2) {
        continue;
      }

      // test two candidate segments for intersection
      hit = segmentIntersection(s1p1x, s1p1y, s1p2x, s1p2y,
          s2p1x, s2p1y, s2p2x, s2p2y);
      if (hit) {
        seg1 = [s1p1, s1p2];
        seg2 = [s2p1, s2p2];
        intersections.push(MapShaper.formatIntersection(hit, seg1, seg2, xx, yy));
        if (hit.length == 4) {
          intersections.push(MapShaper.formatIntersection(hit.slice(2), seg1, seg2, xx, yy));
        }
      }
    }
    i += 2;
  }
  return intersections;

  // @p is an [x, y] location along a segment defined by ids @id1 and @id2
  // return array [i, j] where i and j are the same endpoint ids with i <= j
  // if @p coincides with an endpoint, return the id of that endpoint twice
  function getEndpointIds(id1, id2, p) {
    var i = id1 < id2 ? id1 : id2,
        j = i === id1 ? id2 : id1;
    if (xx[i] == p[0] && yy[i] == p[1]) {
      j = i;
    } else if (xx[j] == p[0] && yy[j] == p[1]) {
      i = j;
    }
    return [i, j];
  }
};

MapShaper.formatIntersection = function(xy, s1, s2, xx, yy) {
  var x = xy[0],
      y = xy[1],
      a, b;
  s1 = MapShaper.formatIntersectingSegment(x, y, s1[0], s1[1], xx, yy);
  s2 = MapShaper.formatIntersectingSegment(x, y, s2[0], s2[1], xx, yy);
  a = s1[0] < s2[0] ? s1 : s2;
  b = a == s1 ? s2 : s1;
  return {x: x, y: y, a: a, b: b};
};

MapShaper.formatIntersectingSegment = function(x, y, id1, id2, xx, yy) {
  var i = id1 < id2 ? id1 : id2,
      j = i === id1 ? id2 : id1;
  if (xx[i] == x && yy[i] == y) {
    j = i;
  } else if (xx[j] == x && yy[j] == y) {
    i = j;
  }
  return [i, j];
};

MapShaper.orderSegmentIds = function(xx, ids, spherical) {
  function swap(i, j) {
    var tmp = ids[i];
    ids[i] = ids[j];
    ids[j] = tmp;
  }
  for (var i=0, n=ids.length; i<n; i+=2) {
    if (xx[ids[i]] > xx[ids[i+1]]) {
      swap(i, i+1);
    }
  }
};

MapShaper.sortSegmentIds = function(xx, ids) {
  MapShaper.orderSegmentIds(xx, ids);
  MapShaper.quicksortSegmentIds(xx, ids, 0, ids.length-2);
};

MapShaper.insertionSortSegmentIds = function(arr, ids, start, end) {
  var id, id2;
  for (var j = start + 2; j <= end; j+=2) {
    id = ids[j];
    id2 = ids[j+1];
    for (var i = j - 2; i >= start && arr[id] < arr[ids[i]]; i-=2) {
      ids[i+2] = ids[i];
      ids[i+3] = ids[i+1];
    }
    ids[i+2] = id;
    ids[i+3] = id2;
  }
};

MapShaper.quicksortSegmentIds = function (a, ids, lo, hi) {
  var i = lo,
      j = hi,
      pivot, tmp;
  while (i < hi) {
    pivot = a[ids[(lo + hi >> 2) << 1]]; // avoid n^2 performance on sorted arrays
    while (i <= j) {
      while (a[ids[i]] < pivot) i+=2;
      while (a[ids[j]] > pivot) j-=2;
      if (i <= j) {
        tmp = ids[i];
        ids[i] = ids[j];
        ids[j] = tmp;
        tmp = ids[i+1];
        ids[i+1] = ids[j+1];
        ids[j+1] = tmp;
        i+=2;
        j-=2;
      }
    }

    if (j - lo < 40) MapShaper.insertionSortSegmentIds(a, ids, lo, j);
    else MapShaper.quicksortSegmentIds(a, ids, lo, j);
    if (hi - i < 40) {
      MapShaper.insertionSortSegmentIds(a, ids, i, hi);
      return;
    }
    lo = i;
    j = hi;
  }
};




// Calculations for planar geometry of shapes
// TODO: consider 3D versions of some of these

geom.getPlanarShapeArea = function(shp, arcs) {
  return (shp || []).reduce(function(area, ids) {
    return area + geom.getPlanarPathArea(ids, arcs);
  }, 0);
};

geom.getSphericalShapeArea = function(shp, arcs) {
  if (arcs.isPlanar()) {
    error("[getSphericalShapeArea()] Function requires decimal degree coordinates");
  }
  return (shp || []).reduce(function(area, ids) {
    return area + geom.getSphericalPathArea(ids, arcs);
  }, 0);
};

// Return path with the largest (area) bounding box
// @shp array of array of arc ids
// @arcs ArcCollection
geom.getMaxPath = function(shp, arcs) {
  var maxArea = 0;
  return (shp || []).reduce(function(maxPath, path) {
    var bbArea = arcs.getSimpleShapeBounds(path).area();
    if (bbArea > maxArea) {
      maxArea = bbArea;
      maxPath = path;
    }
    return maxPath;
  }, null);
};

// @ids array of arc ids
// @arcs ArcCollection
geom.getAvgPathXY = function(ids, arcs) {
  var iter = arcs.getShapeIter(ids);
  if (!iter.hasNext()) return null;
  var x0 = iter.x,
      y0 = iter.y,
      count = 0,
      sumX = 0,
      sumY = 0;
  while (iter.hasNext()) {
    count++;
    sumX += iter.x;
    sumY += iter.y;
  }
  if (count === 0 || iter.x !== x0 || iter.y !== y0) {
    sumX += x0;
    sumY += y0;
    count++;
  }
  return {
    x: sumX / count,
    y: sumY / count
  };
};

// Return true if point is inside or on boundary of a shape
//
geom.testPointInPolygon = function(x, y, shp, arcs) {
  var isIn = false,
      isOn = false;
  if (shp) {
    shp.forEach(function(ids) {
      var inRing = geom.testPointInRing(x, y, ids, arcs);
      if (inRing == 1) {
        isIn = !isIn;
      } else if (inRing == -1) {
        isOn = true;
      }
    });
  }
  return isOn || isIn;
};


geom.getPointToPathDistance = function(px, py, ids, arcs) {
  var iter = arcs.getShapeIter(ids);
  if (!iter.hasNext()) return Infinity;
  var ax = iter.x,
      ay = iter.y,
      paSq = distanceSq(px, py, ax, ay),
      pPathSq = paSq,
      pbSq, abSq,
      bx, by;

  while (iter.hasNext()) {
    bx = iter.x;
    by = iter.y;
    pbSq = distanceSq(px, py, bx, by);
    abSq = distanceSq(ax, ay, bx, by);
    pPathSq = Math.min(pPathSq, apexDistSq(paSq, pbSq, abSq));
    ax = bx;
    ay = by;
    paSq = pbSq;
  }
  return Math.sqrt(pPathSq);
};

geom.getYIntercept = function(x, ax, ay, bx, by) {
  return ay + (x - ax) * (by - ay) / (bx - ax);
};

geom.getXIntercept = function(y, ax, ay, bx, by) {
  return ax + (y - ay) * (bx - ax) / (by - ay);
};

// Return unsigned distance of a point to a shape
//
geom.getPointToShapeDistance = function(x, y, shp, arcs) {
  var minDist = (shp || []).reduce(function(minDist, ids) {
    var pathDist = geom.getPointToPathDistance(x, y, ids, arcs);
    return Math.min(minDist, pathDist);
  }, Infinity);
  return minDist;
};

// Test if point (x, y) is inside, outside or on the boundary of a polygon ring
// Return 0: outside; 1: inside; -1: on boundary
//
geom.testPointInRing = function(x, y, ids, arcs) {
  /*
  // arcs.getSimpleShapeBounds() doesn't apply simplification, can't use here
  //// wait, why not? simplifcation shoudn't expand bounds, so this test makes sense
  if (!arcs.getSimpleShapeBounds(ids).containsPoint(x, y)) {
    return false;
  }
  */
  var isIn = false,
      isOn = false;
  MapShaper.forEachPathSegment(ids, arcs, function(a, b, xx, yy) {
    var result = geom.testRayIntersection(x, y, xx[a], yy[a], xx[b], yy[b]);
    if (result == 1) {
      isIn = !isIn;
    } else if (isNaN(result)) {
      isOn = true;
    }
  });
  return isOn ? -1 : (isIn ? 1 : 0);
};

// test if a vertical ray originating at (x, y) intersects a segment
// returns 1 if intersection, 0 if no intersection, NaN if point touches segment
// (Special rules apply to endpoint intersections, to support point-in-polygon testing.)
geom.testRayIntersection = function(x, y, ax, ay, bx, by) {
  var val = geom.getRayIntersection(x, y, ax, ay, bx, by);
  if (val != val) {
    return NaN;
  }
  return val == -Infinity ? 0 : 1;
};

geom.getRayIntersection = function(x, y, ax, ay, bx, by) {
  var hit = -Infinity, // default: no hit
      yInt;

  // case: p is entirely above, left or right of segment
  if (x < ax && x < bx || x > ax && x > bx || y > ay && y > by) {
      // no intersection
  }
  // case: px aligned with a segment vertex
  else if (x === ax || x === bx) {
    // case: vertical segment or collapsed segment
    if (x === ax && x === bx) {
      // p is on segment
      if (y == ay || y == by || y > ay != y > by) {
        hit = NaN;
      }
      // else: no hit
    }
    // case: px equal to ax (only)
    else if (x === ax) {
      if (y === ay) {
        hit = NaN;
      } else if (bx < ax && y < ay) {
        // only score hit if px aligned to rightmost endpoint
        hit = ay;
      }
    }
    // case: px equal to bx (only)
    else {
      if (y === by) {
        hit = NaN;
      } else if (ax < bx && y < by) {
        // only score hit if px aligned to rightmost endpoint
        hit = by;
      }
    }
  // case: px is between endpoints
  } else {
    yInt = geom.getYIntercept(x, ax, ay, bx, by);
    if (yInt > y) {
      hit = yInt;
    } else if (yInt == y) {
      hit = NaN;
    }
  }
  return hit;
};

geom.getSphericalPathArea = function(ids, arcs) {
  var iter = arcs.getShapeIter(ids),
      sum = 0,
      started = false,
      deg2rad = Math.PI / 180,
      x, y, xp, yp;
  while (iter.hasNext()) {
    x = iter.x * deg2rad;
    y = Math.sin(iter.y * deg2rad);
    if (started) {
      sum += (x - xp) * (2 + y + yp);
    } else {
      started = true;
    }
    xp = x;
    yp = y;
  }
  return sum / 2 * 6378137 * 6378137;
};

// Get path area from an array of [x, y] points
// TODO: consider removing duplication with getPathArea(), e.g. by
//   wrapping points in an iterator.
//
geom.getPlanarPathArea2 = function(points) {
  var sum = 0,
      ax, ay, bx, by, dx, dy, p;
  for (var i=0, n=points.length; i<n; i++) {
    p = points[i];
    if (i === 0) {
      ax = 0;
      ay = 0;
      dx = -p[0];
      dy = -p[1];
    } else {
      ax = p[0] + dx;
      ay = p[1] + dy;
      sum += ax * by - bx * ay;
    }
    bx = ax;
    by = ay;
  }
  return sum / 2;
};

geom.getPlanarPathArea = function(ids, arcs) {
  var iter = arcs.getShapeIter(ids),
      sum = 0,
      ax, ay, bx, by, dx, dy;
  if (iter.hasNext()) {
    ax = 0;
    ay = 0;
    dx = -iter.x;
    dy = -iter.y;
    while (iter.hasNext()) {
      bx = ax;
      by = ay;
      ax = iter.x + dx;
      ay = iter.y + dy;
      sum += ax * by - bx * ay;
    }
  }
  return sum / 2;
};

geom.countVerticesInPath = function(ids, arcs) {
  var iter = arcs.getShapeIter(ids),
      count = 0;
  while (iter.hasNext()) count++;
  return count;
};

geom.getPathBounds = function(points) {
  var bounds = new Bounds();
  for (var i=0, n=points.length; i<n; i++) {
    bounds.mergePoint(points[i][0], points[i][1]);
  }
  return bounds;
};

geom.transposePoints = function(points) {
  var xx = [], yy = [], n=points.length;
  for (var i=0; i<n; i++) {
    xx.push(points[i][0]);
    yy.push(points[i][1]);
  }
  return [xx, yy];
};




// PolygonIndex indexes the coordinates in one polygon feature for efficient
// point-in-polygon tests

MapShaper.PolygonIndex = PolygonIndex;

function PolygonIndex(shape, arcs) {
  var data = arcs.getVertexData(),
      polygonBounds = arcs.getMultiShapeBounds(shape),
      boundsLeft,
      p1Arr, p2Arr,
      bucketCount,
      bucketOffsets,
      bucketWidth;

  init();

  // Return 0 if outside, 1 if inside, -1 if on boundary
  this.pointInPolygon = function(x, y) {
    if (!polygonBounds.containsPoint(x, y)) {
      return false;
    }
    var bucketId = getBucketId(x);
    var count = countCrosses(x, y, bucketId);
    if (bucketId > 0) {
      count += countCrosses(x, y, bucketId - 1);
    }
    if (bucketId < bucketCount - 1) {
      count += countCrosses(x, y, bucketId + 1);
    }
    count += countCrosses(x, y, bucketCount); // check oflo bucket
    if (isNaN(count)) return -1;
    return count % 2 == 1 ? 1 : 0;
  };

  function init() {
    var xx = data.xx,
        segCount = 0,
        bucketId = 0,
        bucketLeft = boundsLeft,
        segId = 0,
        segments,
        lastX,
        head, tail,
        a, b, i, j, xmin, xmax;

    // get sorted array of segment ids
    MapShaper.forEachPathSegment(shape, arcs, function() {
      segCount++;
    });
    segments = new Uint32Array(segCount * 2);
    i = 0;
    MapShaper.forEachPathSegment(shape, arcs, function(a, b, xx, yy) {
      segments[i++] = a;
      segments[i++] = b;
    });
    MapShaper.sortSegmentIds(xx, segments);

    // populate buckets
    p1Arr = new Uint32Array(segCount);
    p2Arr = new Uint32Array(segCount);
    bucketCount = Math.ceil(segCount / 100);
    bucketOffsets = new Uint32Array(bucketCount + 1);
    lastX = xx[segments[segments.length - 2]]; // xmin of last segment
    bucketLeft = boundsLeft = xx[segments[0]]; // xmin of first segment
    bucketWidth = (lastX - boundsLeft) / bucketCount;
    head = 0;
    tail = segCount - 1;

    while (bucketId < bucketCount && segId < segCount) {
      j = segId * 2;
      a = segments[j];
      b = segments[j+1];
      xmin = xx[a];
      xmax = xx[b];

      if (xmin > bucketLeft + bucketWidth && bucketId < bucketCount - 1) {
        bucketId++;
        bucketLeft = bucketId * bucketWidth + boundsLeft;
        bucketOffsets[bucketId] = head;
      } else {
        if (getBucketId(xmin) != bucketId) console.log("wrong bucket");
        if (xmin < bucketLeft) error("out-of-range");
        if (xmax - xmin >= 0 === false) error("invalid segment");
        if (xmax > bucketLeft + 2 * bucketWidth) {
          p1Arr[tail] = a;
          p2Arr[tail] = b;
          tail--;
        } else {
          p1Arr[head] = a;
          p2Arr[head] = b;
          head++;
        }
        segId++;
      }
    }
    bucketOffsets[bucketCount] = head;
    if (head != tail + 1) error("counting error; head:", head, "tail:", tail);
  }

  function countCrosses(x, y, bucketId) {
    var offs = bucketOffsets[bucketId],
        n = (bucketId == bucketCount) ? p1Arr.length - offs : bucketOffsets[bucketId + 1] - offs,
        count = 0,
        xx = data.xx,
        yy = data.yy,
        a, b;

    for (var i=0; i<n; i++) {
      a = p1Arr[i + offs];
      b = p2Arr[i + offs];
      count += geom.testRayIntersection(x, y, xx[a], yy[a], xx[b], yy[b]);
    }
    return count;
  }

  function getBucketId(x) {
    var i = Math.floor((x - boundsLeft) / bucketWidth);
    if (i < 0) i = 0;
    if (i >= bucketCount) i = bucketCount - 1;
    return i;
  }

}




MapShaper.PathIndex = PathIndex;

function PathIndex(shapes, arcs) {
  var _index;
  // var totalArea = arcs.getBounds().area();
  var totalArea = MapShaper.getPathBounds(shapes, arcs).area();
  init(shapes);

  function init(shapes) {
    var boxes = [];

    shapes.forEach(function(shp, shpId) {
      var n = shp ? shp.length : 0;
      for (var i=0; i<n; i++) {
        addPath(shp[i], shpId);
      }
    });

    _index = require('rbush')();
    _index.load(boxes);

    function addPath(ids, shpId) {
      var bounds = arcs.getSimpleShapeBounds(ids);
      var bbox = bounds.toArray();
      bbox.ids = ids;
      bbox.bounds = bounds;
      bbox.id = shpId;
      boxes.push(bbox);
      // TODO: Better test for whether or not to index a path
      if (bounds.area() > totalArea * 0.02) {
        bbox.index = new PolygonIndex([ids], arcs);
      }
    }
  }

  this.findEnclosingShape = function(p) {
    var shpId = -1;
    var shapes = findPointHitShapes(p);
    shapes.forEach(function(paths) {
      if (testPointInRings(p, paths)) {
        shpId = paths[0].id;
      }
    });
    return shpId;
  };

  this.pointIsEnclosed = function(p) {
    return testPointInRings(p, findPointHitRings(p));
  };

  this.arcIsEnclosed = function(arcId) {
    return this.pointIsEnclosed(getTestPoint(arcId));
  };

  // Test if a polygon ring is contained within an indexed ring
  // Not a true polygon-in-polygon test
  // Assumes that the target ring does not cross an indexed ring at any point
  // or share a segment with an indexed ring. (Intersecting rings should have
  // been detected previously).
  //
  this.pathIsEnclosed = function(pathIds) {
    var arcId = pathIds[0];
    var p = getTestPoint(arcId);
    return this.pointIsEnclosed(p);
  };

  // return array of paths that are contained within a path, or null if none
  // @pathIds Array of arc ids comprising a closed path
  this.findEnclosedPaths = function(pathIds) {
    var pathBounds = arcs.getSimpleShapeBounds(pathIds),
        cands = _index.search(pathBounds.toArray()),
        paths = [],
        index;

    if (cands.length > 6) {
      index = new PolygonIndex([pathIds], arcs);
    }


    cands.forEach(function(cand) {
      var p = getTestPoint(cand.ids[0]);
      var isEnclosed = index ?
        index.pointInPolygon(p[0], p[1]) : pathContainsPoint(pathIds, pathBounds, p);
      if (isEnclosed) {
        paths.push(cand.ids);
      }
    });
    return paths.length > 0 ? paths : null;
  };

  this.findPathsInsideShape = function(shape) {
    var paths = [];
    shape.forEach(function(ids) {
      var enclosed = this.findEnclosedPaths(ids);
      if (enclosed) {
        paths = xorArrays(paths, enclosed);
      }
    }, this);
    return paths.length > 0 ? paths : null;
  };

  function testPointInRings(p, cands) {
    var isOn = false,
        isIn = false;
    cands.forEach(function(cand) {
      var inRing = cand.index ?
        cand.index.pointInPolygon(p[0], p[1]) :
        pathContainsPoint(cand.ids, cand.bounds, p);
      if (inRing == -1) {
        isOn = true;
      } else if (inRing == 1) {
        isIn = !isIn;
      }
    });
    return isOn || isIn;
  }

  function findPointHitShapes(p) {
    var rings = findPointHitRings(p),
        shapes = [],
        shape, bbox;
    if (rings.length > 0) {
      rings.sort(function(a, b) {return a.id - b.id;});
      for (var i=0; i<rings.length; i++) {
        bbox = rings[i];
        if (i === 0 || bbox.id != rings[i-1].id) {
          shapes.push(shape=[]);
        }
        shape.push(bbox);
      }
    }
    return shapes;
  }

  function findPointHitRings(p) {
    var x = p[0],
        y = p[1];
    return _index.search([x, y, x, y]);
  }

  function getTestPoint(arcId) {
    // test point halfway along first segment because ring might still be
    // enclosed if a segment endpoint touches an indexed ring.
    var p0 = arcs.getVertex(arcId, 0),
        p1 = arcs.getVertex(arcId, 1);
    return [(p0.x + p1.x) / 2, (p0.y + p1.y) / 2];
  }

  function pathContainsPoint(pathIds, pathBounds, p) {
    if (pathBounds.containsPoint(p[0], p[1]) === false) return 0;
    // A contains B iff some point on B is inside A
    return geom.testPointInRing(p[0], p[1], pathIds, arcs);
  }

  function xorArrays(a, b) {
    var xor = [];
    a.forEach(function(el) {
      if (b.indexOf(el) == -1) xor.push(el);
    });
    b.forEach(function(el) {
      if (xor.indexOf(el) == -1) xor.push(el);
    });
    return xor;
  }
}




MapShaper.NodeCollection = NodeCollection;

// @arcs ArcCollection
// @filter Optional filter function, arcIds that return false are excluded
//
function NodeCollection(arcs, filter) {
  if (utils.isArray(arcs)) {
    arcs = new ArcCollection(arcs);
  }
  var arcData = arcs.getVertexData(),
      nn = arcData.nn,
      xx = arcData.xx,
      yy = arcData.yy;

  var nodeData = MapShaper.findNodeTopology(arcs, filter);

  if (nn.length * 2 != nodeData.chains.length) error("[NodeCollection] count error");

  // TODO: could check that arc collection hasn't been modified, using accessor function
  Object.defineProperty(this, 'arcs', {value: arcs});

  this.toArray = function() {
    var flags = new Uint8Array(nodeData.xx.length),
        nodes = [];
    utils.forEach(nodeData.chains, function(next, i) {
      if (flags[i] == 1) return;
      nodes.push([nodeData.xx[i], nodeData.yy[i]]);
      while (flags[next] != 1) {
        flags[next] = 1;
        next = nodeData.chains[next];
      }
    });
    return nodes;
  };

  this.size = function() {
    return this.toArray().length;
  };

  this.debugNode = function(arcId) {
    if (!MapShaper.TRACING) return;
    var ids = [arcId];
    this.forEachConnectedArc(arcId, function(id) {
      ids.push(id);
    });

    message("node ids:",  ids);
    ids.forEach(printArc);

    function printArc(id) {
      var str = id + ": ";
      var len = arcs.getArcLength(id);
      if (len > 0) {
        var p1 = arcs.getVertex(id, -1);
        str += utils.format("[%f, %f]", p1.x, p1.y);
        if (len > 1) {
          var p2 = arcs.getVertex(id, -2);
          str += utils.format(", [%f, %f]", p2.x, p2.y);
          if (len > 2) {
            var p3 = arcs.getVertex(id, 0);
            str += utils.format(", [%f, %f]", p3.x, p3.y);
          }
          str += " len: " + distance2D(p1.x, p1.y, p2.x, p2.y);
        }
      } else {
        str = "[]";
      }
      message(str);
    }
  };

  this.forEachConnectedArc = function(arcId, cb) {
    var nextId = nextConnectedArc(arcId),
        i = 0;
    while (nextId != arcId) {
      cb(nextId, i++);
      nextId = nextConnectedArc(nextId);
    }
  };

  // Returns the id of the first identical arc or @arcId if none found
  // TODO: find a better function name
  this.findMatchingArc = function(arcId) {
    var verbose = arcId ==  -12794 || arcId == 19610;
    var nextId = nextConnectedArc(arcId),
        match = arcId;
    while (nextId != arcId) {
      if (testArcMatch(arcId, nextId)) {
        if (absArcId(nextId) < absArcId(match)) match = nextId;
      }
      nextId = nextConnectedArc(nextId);
    }
    if (match != arcId) {
      trace("found identical arc:", arcId, "->", match);
      // this.debugNode(arcId);
    }
    return match;
  };

  function testArcMatch(a, b) {
    var absA = a >= 0 ? a : ~a,
        absB = b >= 0 ? b : ~b,
        lenA = nn[absA];
    if (lenA < 2) {
      // Don't throw error on collapsed arcs -- assume they will be handled
      //   appropriately downstream.
      // error("[testArcMatch() defective arc; len:", lenA);
      return false;
    }
    if (lenA != nn[absB]) return false;
    if (testVertexMatch(a, b, -1) &&
        testVertexMatch(a, b, 1) &&
        testVertexMatch(a, b, -2)) {
      return true;
    }
    return false;
  }

  function testVertexMatch(a, b, i) {
    var ai = arcs.indexOfVertex(a, i),
        bi = arcs.indexOfVertex(b, i);
    return xx[ai] == xx[bi] && yy[ai] == yy[bi];
  }

  // return arcId of next arc in the chain, pointed towards the shared vertex
  function nextConnectedArc(arcId) {
    var fw = arcId >= 0,
        absId = fw ? arcId : ~arcId,
        nodeId = fw ? absId * 2 + 1: absId * 2, // if fw, use end, if rev, use start
        chainedId = nodeData.chains[nodeId],
        nextAbsId = chainedId >> 1,
        nextArcId = chainedId & 1 == 1 ? nextAbsId : ~nextAbsId;

    if (chainedId < 0 || chainedId >= nodeData.chains.length) error("out-of-range chain id");
    if (absId >= nn.length) error("out-of-range arc id");
    if (nodeData.chains.length <= nodeId) error("out-of-bounds node id");
    return nextArcId;
  }

  // expose for testing
  this.internal = {
    testArcMatch: testArcMatch,
    testVertexMatch: testVertexMatch
  };
}

MapShaper.findNodeTopology = function(arcs, filter) {
  var n = arcs.size() * 2,
      xx2 = new Float64Array(n),
      yy2 = new Float64Array(n),
      ids2 = new Int32Array(n);

  arcs.forEach2(function(i, n, xx, yy, zz, arcId) {
    if (filter && !filter(arcId)) {
      return;
    }
    var start = i,
        end = i + n - 1,
        start2 = arcId * 2,
        end2 = start2 + 1;
    xx2[start2] = xx[start];
    yy2[start2] = yy[start];
    ids2[start2] = arcId;
    xx2[end2] = xx[end];
    yy2[end2] = yy[end];
    ids2[end2] = arcId;
  });

  var chains = initPointChains(xx2, yy2);
  return {
    xx: xx2,
    yy: yy2,
    ids: ids2,
    chains: chains
  };
};




// Return function for splitting self-intersecting polygon rings
// Returned function receives a single path, returns an array of paths
// Assumes that any intersections occur at vertices, not along segments
// (requires that MapShaper.divideArcs() has already been run)
//
MapShaper.getSelfIntersectionSplitter = function(nodes) {

  function contains(arr, el) {
    for (var i=0, n=arr.length; i<n; i++) {
      if (arr[i] === el) return true;
    }
    return false;
  }

  // If arc @enterId enters a node with more than one open routes leading out:
  //   return array of sub-paths
  // else return null
  function dividePathAtNode(path, enterId) {
    var count = 0,
        subPaths = null,
        exitIds, firstExitId;
    nodes.forEachConnectedArc(enterId, function(arcId) {
      var exitId = ~arcId;
      // TODO: remove performance bottleneck
      // contains() is faster than native array.indexOf(), could do better.
      // if (path.indexOf(exitId) > -1) { // ignore arcs that are not on this path
      if (contains(path, exitId)) { // ignore arcs that are not on this path
        if (count === 0) {
          firstExitId = exitId;
        } else if (count === 1) {
          exitIds = [firstExitId, exitId];
        } else {
          exitIds.push(exitId);
        }
        count++;
      }
    });
    if (exitIds) {
      subPaths = MapShaper.splitPathByIds(path, exitIds);
      // recursively divide each sub-path
      return subPaths.reduce(function(memo, subPath) {
        return memo.concat(dividePath(subPath));
      }, []);
    }
    return null;
  }

  function dividePath(path) {
    var subPaths = null;
    for (var i=0; i<path.length - 1; i++) { // don't need to check last arc
      subPaths = dividePathAtNode(path, path[i]);
      if (subPaths) {
        return subPaths;
      }
    }
    // indivisible path -- remove any spikes
    MapShaper.removeSpikesInPath(path);
    return path.length > 0 ? [path] : [];
  }

  return dividePath;
};

// @path An array of arc ids
// @ids An array of two or more start ids
MapShaper.splitPathByIds = function(path, ids) {
  var n = ids.length;
  var ii = ids.map(function(id) {
    var idx = path.indexOf(id);
    if (idx == -1) error("[splitPathByIds()] Path is missing id:", id);
    return idx;
  });
  utils.genericSort(ii, true);
  var subPaths = ii.map(function(idx, i) {
    var split;
    if (i == n-1) {
      // place first path item first
      split = path.slice(0, ii[0]).concat(path.slice(idx));
    } else {
      split = path.slice(idx, ii[i+1]);
    }
    return split;
  });

  // make sure first sub-path starts with arc at path[0]
  if (ii[0] !== 0) {
    subPaths.unshift(subPaths.pop());
  }
  if (subPaths[0][0] !== path[0]) {
    error("[splitPathByIds()] Indexing error");
  }
  return subPaths;
};




// Functions for redrawing polygons for clipping / erasing / flattening / division

MapShaper.setBits = function(src, flags, mask) {
  return (src & ~mask) | (flags & mask);
};

MapShaper.andBits = function(src, flags, mask) {
  return src & (~mask | flags);
};

MapShaper.setRouteBits = function(bits, id, flags) {
  var abs = absArcId(id),
      mask;
  if (abs == id) { // fw
    mask = ~3;
  } else {
    mask = ~0x30;
    bits = bits << 4;
  }
  flags[abs] &= (bits | mask);
};

MapShaper.getRouteBits = function(id, flags) {
  var abs = absArcId(id),
      bits = flags[abs];
  if (abs != id) bits = bits >> 4;
  return bits & 7;
};


// enable arc pathways in a single shape or array of shapes
// Uses 8 bits to control traversal of each arc
// 0-3: forward arc; 4-7: rev arc
// 0: fw path is visible
// 1: fw path is open for traversal
// ...
//
MapShaper.openArcRoutes = function(arcIds, arcs, flags, fwd, rev, dissolve, orBits) {
  MapShaper.forEachArcId(arcIds, function(id) {
    var isInv = id < 0,
        absId = isInv ? ~id : id,
        currFlag = flags[absId],
        openFwd = isInv ? rev : fwd,
        openRev = isInv ? fwd : rev,
        newFlag = currFlag;

    // error condition: lollipop arcs can cause problems; ignore these
    if (arcs.arcIsLollipop(id)) {
      trace('lollipop');
      newFlag = 0; // unset (i.e. make invisible)
    } else {
      if (openFwd) {
        newFlag |= 3; // visible / open
      }
      if (openRev) {
        newFlag |= 0x30; // visible / open
      }

      // placing this in front of dissolve - dissolve has to be able to hide
      // arcs that are set to visible
      if (orBits > 0) {
        newFlag |= orBits;
      }

      // dissolve hides arcs that have both fw and rev pathways open
      if (dissolve && (newFlag & 0x22) === 0x22) {
        newFlag &= ~0x11; // make invisible
      }
    }

    flags[absId] = newFlag;
  });
};

MapShaper.closeArcRoutes = function(arcIds, arcs, flags, fwd, rev, hide) {
  MapShaper.forEachArcId(arcIds, function(id) {
    var isInv = id < 0,
        absId = isInv ? ~id : id,
        currFlag = flags[absId],
        mask = 0xff,
        closeFwd = isInv ? rev : fwd,
        closeRev = isInv ? fwd : rev;

    if (closeFwd) {
      if (hide) mask &= ~1;
      mask ^= 0x2;
    }
    if (closeRev) {
      if (hide) mask &= ~0x10;
      mask ^= 0x20;
    }

    flags[absId] = currFlag & mask;
  });
};

// Return a function for generating a path across a field of intersecting arcs
// TODO: add option to calculate angle on sphere for lat-lng coords
//
MapShaper.getPathFinder = function(nodes, useRoute, routeIsVisible, chooseRoute, spherical) {
  var arcs = nodes.arcs,
      coords = arcs.getVertexData(),
      xx = coords.xx,
      yy = coords.yy,
      calcAngle = spherical ? geom.signedAngleSph : geom.signedAngle;

  function getNextArc(prevId) {
    var ai = arcs.indexOfVertex(prevId, -2),
        ax = xx[ai],
        ay = yy[ai],
        bi = arcs.indexOfVertex(prevId, -1),
        bx = xx[bi],
        by = yy[bi],
        nextId = NaN,
        nextAngle = 0;

    nodes.forEachConnectedArc(prevId, function(candId) {
      if (!routeIsVisible(~candId)) return;
      if (arcs.getArcLength(candId) < 2) error("[pathfinder] defective arc");

      var ci = arcs.indexOfVertex(candId, -2),
          cx = xx[ci],
          cy = yy[ci],

          // sanity check: make sure both arcs share the same vertex;
          di = arcs.indexOfVertex(candId, -1),
          dx = xx[di],
          dy = yy[di],
          candAngle;
      if (dx !== bx || dy !== by) {
        message("cd:", cx, cy, dx, dy, 'arc:', candId);
        error("Error in node topology");
      }

      candAngle = calcAngle(ax, ay, bx, by, cx, cy);

      if (candAngle > 0) {
        if (nextAngle === 0) {
          nextId = candId;
          nextAngle = candAngle;
        } else {
          var choice = chooseRoute(~nextId, nextAngle, ~candId, candAngle, prevId);
          if (choice == 2) {
            nextId = candId;
            nextAngle = candAngle;
          }
        }
      } else {
        // candAngle is NaN or 0
        trace("#getNextArc() Invalid angle; id:", candId, "angle:", candAngle);
        nodes.debugNode(prevId);
      }
    });

    if (nextId === prevId) {
      // TODO: confirm that this can't happen
      nodes.debugNode(prevId);
      error("#getNextArc() nextId === prevId");
    }
    return ~nextId; // reverse arc to point onwards
  }

  return function(startId) {
    var path = [],
        nextId, msg,
        candId = startId,
        verbose = false;

    do {
      if (verbose) msg = (nextId === undefined ? " " : "  " + nextId) + " -> " + candId;
      if (useRoute(candId)) {
        path.push(candId);
        nextId = candId;
        if (verbose) message(msg);
        candId = getNextArc(nextId);
        if (verbose && candId == startId ) message("  o", geom.getPlanarPathArea(path, arcs));
      } else {
        if (verbose) message(msg + " x");
        return null;
      }

      if (candId == ~nextId) {
        trace("dead-end"); // TODO: handle or prevent this error condition
        return null;
      }
    } while (candId != startId);
    return path.length === 0 ? null : path;
  };
};

// types: "dissolve" "flatten"
// Returns a function for flattening or dissolving a collection of rings
// Assumes rings are oriented in CW direction
//
MapShaper.getRingIntersector = function(nodes, type, flags, spherical) {
  var arcs = nodes.arcs;
  var findPath = MapShaper.getPathFinder(nodes, useRoute, routeIsActive, chooseRoute, spherical);
  flags = flags || new Uint8Array(arcs.size());

  return function(rings) {
    var dissolve = type == 'dissolve',
        openFwd = true,
        openRev = type == 'flatten',
        output;
    // even single rings get transformed (e.g. to remove spikes)
    if (rings.length > 0) {
      output = [];
      MapShaper.openArcRoutes(rings, arcs, flags, openFwd, openRev, dissolve);
      MapShaper.forEachPath(rings, function(ids) {
        var path;
        for (var i=0, n=ids.length; i<n; i++) {
          path = findPath(ids[i]);
          if (path) {
            output.push(path);
          }
        }
      });
      MapShaper.closeArcRoutes(rings, arcs, flags, openFwd, openRev, true);
    } else {
      output = rings;
    }
    return output;
  };

  function chooseRoute(id1, angle1, id2, angle2, prevId) {
    var route = 1;
    if (angle1 == angle2) {
      trace("[chooseRoute()] parallel routes, unsure which to choose");
      //MapShaper.debugRoute(id1, id2, nodes.arcs);
    } else if (angle2 < angle1) {
      route = 2;
    }
    return route;
  }

  function routeIsActive(arcId) {
    var bits = MapShaper.getRouteBits(arcId, flags);
    return (bits & 1) == 1;
  }

  function useRoute(arcId) {
    var route = MapShaper.getRouteBits(arcId, flags),
        isOpen = false;

    if (route == 3) {
      isOpen = true;
      MapShaper.setRouteBits(1, arcId, flags); // close the path, leave visible
    }

    return isOpen;
  }
};

MapShaper.debugFlags = function(flags) {
  var arr = [];
  utils.forEach(flags, function(flag) {
    arr.push(bitsToString(flag));
  });
  message(arr);

  function bitsToString(bits) {
    var str = "";
    for (var i=0; i<8; i++) {
      str += (bits & (1 << i)) > 0 ? "1" : "0";
      if (i < 7) str += ' ';
      if (i == 3) str += ' ';
    }
    return str;
  }
};

/*
// Print info about two arcs whose first segments are parallel
//
MapShaper.debugRoute = function(id1, id2, arcs) {
  var n1 = arcs.getArcLength(id1),
      n2 = arcs.getArcLength(id2),
      len1 = 0,
      len2 = 0,
      p1, p2, pp1, pp2, ppp1, ppp2,
      angle1, angle2;

      console.log("chooseRoute() lengths:", n1, n2, 'ids:', id1, id2);
  for (var i=0; i<n1 && i<n2; i++) {
    p1 = arcs.getVertex(id1, i);
    p2 = arcs.getVertex(id2, i);
    if (i === 0) {
      if (p1.x != p2.x || p1.y != p2.y) {
        error("chooseRoute() Routes should originate at the same point)");
      }
    }

    if (i > 1) {
      angle1 = signedAngle(ppp1.x, ppp1.y, pp1.x, pp1.y, p1.x, p1.y);
      angle2 = signedAngle(ppp2.x, ppp2.y, pp2.x, pp2.y, p2.x, p2.y);

      console.log("angles:", angle1, angle2, 'lens:', len1, len2);
      // return;
    }

    if (i >= 1) {
      len1 += distance2D(p1.x, p1.y, pp1.x, pp1.y);
      len2 += distance2D(p2.x, p2.y, pp2.x, pp2.y);
    }

    if (i == 1 && (n1 == 2 || n2 == 2)) {
      console.log("arc1:", pp1, p1, "len:", len1);
      console.log("arc2:", pp2, p2, "len:", len2);
    }

    ppp1 = pp1;
    ppp2 = pp2;
    pp1 = p1;
    pp2 = p2;
  }
  return 1;
};
*/




// Returns a function that separates rings in a polygon into space-enclosing rings
// and holes. Also fixes self-intersections.
//
MapShaper.getHoleDivider = function(nodes, spherical) {
  var split = MapShaper.getSelfIntersectionSplitter(nodes);

  return function(rings, cw, ccw) {
    var pathArea = spherical ? geom.getSphericalPathArea : geom.getPlanarPathArea;
    MapShaper.forEachPath(rings, function(ringIds) {
      var splitRings = split(ringIds);
      if (splitRings.length === 0) {
        trace("[getRingDivider()] Defective path:", ringIds);
      }
      splitRings.forEach(function(ringIds, i) {
        var ringArea = pathArea(ringIds, nodes.arcs);
        if (ringArea > 0) {
          cw.push(ringIds);
        } else if (ringArea < 0) {
          ccw.push(ringIds);
        }
      });
    });
  };
};




// clean polygon or polyline shapes, in-place
//
MapShaper.cleanShapes = function(shapes, arcs, type) {
  for (var i=0, n=shapes.length; i<n; i++) {
    shapes[i] = MapShaper.cleanShape(shapes[i], arcs, type);
  }
};

// Remove defective arcs and zero-area polygon rings
// Don't remove duplicate points
// Don't remove spikes (between arcs or within arcs)
// Don't check winding order of polygon rings
MapShaper.cleanShape = function(shape, arcs, type) {
  return MapShaper.editPaths(shape, function(path) {
    var cleaned = MapShaper.cleanPath(path, arcs);
    if (type == 'polygon' && cleaned) {
      MapShaper.removeSpikesInPath(cleaned); // assumed by divideArcs()
      if (geom.getPlanarPathArea(cleaned, arcs) === 0) {
        cleaned = null;
      }
    }
    return cleaned;
  });
};

MapShaper.cleanPath = function(path, arcs) {
  var nulls = 0;
  for (var i=0, n=path.length; i<n; i++) {
    if (arcs.arcIsDegenerate(path[i])) {
      nulls++;
      path[i] = null;
    }
  }
  return nulls > 0 ? path.filter(function(id) {return id !== null;}) : path;
};

// Remove pairs of ids where id[n] == ~id[n+1] or id[0] == ~id[n-1];
// (in place)
MapShaper.removeSpikesInPath = function(ids) {
  var n = ids.length;
  if (n >= 2) {
    if (ids[0] == ~ids[n-1]) {
      ids.pop();
      ids.shift();
    } else {
      for (var i=1; i<n; i++) {
        if (ids[i-1] == ~ids[i]) {
          ids.splice(i-1, 2);
          break;
        }
      }
    }
    if (ids.length < n) {
      MapShaper.removeSpikesInPath(ids);
    }
  }
};


// TODO: Need to rethink polygon repair: these function can cause problems
// when part of a self-intersecting polygon is removed
//
MapShaper.repairPolygonGeometry = function(layers, dataset, opts) {
  var nodes = MapShaper.divideArcs(dataset);
  layers.forEach(function(lyr) {
    MapShaper.repairSelfIntersections(lyr, nodes);
  });
  return layers;
};

// Remove any small shapes formed by twists in each ring
// // OOPS, NO // Retain only the part with largest area
// // this causes problems when a cut-off hole has a matching ring in another polygon
// TODO: consider cases where cut-off parts should be retained
//
MapShaper.repairSelfIntersections = function(lyr, nodes) {
  var splitter = MapShaper.getSelfIntersectionSplitter(nodes);

  lyr.shapes = lyr.shapes.map(function(shp, i) {
    return cleanPolygon(shp);
  });

  function cleanPolygon(shp) {
    var cleanedPolygon = [];
    MapShaper.forEachPath(shp, function(ids) {
      // TODO: consider returning null if path can't be split
      var splitIds = splitter(ids);
      if (splitIds.length === 0) {
        error("[cleanPolygon()] Defective path:", ids);
      } else if (splitIds.length == 1) {
        cleanedPolygon.push(splitIds[0]);
      } else {
        var shapeArea = geom.getPlanarPathArea(ids, nodes.arcs),
            sign = shapeArea > 0 ? 1 : -1,
            mainRing;

        var maxArea = splitIds.reduce(function(max, ringIds, i) {
          var pathArea = geom.getPlanarPathArea(ringIds, nodes.arcs) * sign;
          if (pathArea > max) {
            mainRing = ringIds;
            max = pathArea;
          }
          return max;
        }, 0);

        if (mainRing) {
          cleanedPolygon.push(mainRing);
        }
      }
    });
    return cleanedPolygon.length > 0 ? cleanedPolygon : null;
  }
};




// Functions for dividing polygons and polygons at points where arc-segments intersect

// Divide a collection of arcs at points where segments intersect
// and re-index the paths of all the layers that reference the arc collection.
// (in-place)
MapShaper.divideArcs = function(dataset) {
  var arcs = dataset.arcs;
  T.start();
  T.start();
  var snapDist = MapShaper.getHighPrecisionSnapInterval(arcs);
  var snapCount = MapShaper.snapCoordsByInterval(arcs, snapDist);
  var dupeCount = arcs.dedupCoords();
  T.stop('snap points');
  if (snapCount > 0 || dupeCount > 0) {
    T.start();
    // Detect topology again if coordinates have changed
    api.buildTopology(dataset);
    T.stop('rebuild topology');
  }

  // clip arcs at points where segments intersect
  T.start();
  var map = MapShaper.insertClippingPoints(arcs);
  T.stop('insert clipping points');
  T.start();
  // update arc ids in arc-based layers and clean up arc geometry
  // to remove degenerate arcs and duplicate points
  var nodes = new NodeCollection(arcs);
  dataset.layers.forEach(function(lyr) {
    if (MapShaper.layerHasPaths(lyr)) {
      MapShaper.updateArcIds(lyr.shapes, map, nodes);
      // TODO: consider alternative -- avoid creating degenerate arcs
      // in insertClippingPoints()
      MapShaper.cleanShapes(lyr.shapes, arcs, lyr.geometry_type);
    }
  });
  T.stop('update arc ids / clean geometry');
  T.stop("divide arcs");
  return nodes;
};

MapShaper.updateArcIds = function(shapes, map, nodes) {
  var arcCount = nodes.arcs.size(),
      shape2;
  for (var i=0; i<shapes.length; i++) {
    shape2 = [];
    MapShaper.forEachPath(shapes[i], remapPathIds);
    shapes[i] = shape2;
  }

  function remapPathIds(ids) {
    if (!ids) return; // null shape
    var ids2 = [];
    for (var j=0; j<ids.length; j++) {
      remapArcId(ids[j], ids2);
    }
    shape2.push(ids2);
  }

  function remapArcId(id, ids) {
    var rev = id < 0,
        absId = rev ? ~id : id,
        min = map[absId],
        max = (absId >= map.length - 1 ? arcCount : map[absId + 1]) - 1,
        id2;
    do {
      if (rev) {
        id2 = ~max;
        max--;
      } else {
        id2 = min;
        min++;
      }
      // If there are duplicate arcs, always use the same one
      if (nodes) {
        id2 = nodes.findMatchingArc(id2);
      }
      ids.push(id2);
    } while (max - min >= 0);
  }
};

// divide a collection of arcs at points where line segments cross each other
// @arcs ArcCollection
// returns array that maps original arc ids to new arc ids
MapShaper.insertClippingPoints = function(arcs) {
  var points = MapShaper.findClippingPoints(arcs),
      p;
  // TODO: avoid some or all of the following if no points need to be added

  // original arc data
  var pointTotal0 = arcs.getPointCount(),
      arcTotal0 = arcs.size(),
      data = arcs.getVertexData(),
      xx0 = data.xx,
      yy0 = data.yy,
      nn0 = data.nn,
      i0 = 0,
      n0, arcLen0;

  // new arc data
  var pointTotal1 = pointTotal0 + points.length * 2,
      xx1 = new Float64Array(pointTotal1),
      yy1 = new Float64Array(pointTotal1),
      nn1 = [],  // number of arcs may vary
      i1 = 0,
      n1;

  var map = new Uint32Array(arcTotal0);

  // sort from last point to first point
  points.sort(function(a, b) {
    return b.i - a.i || b.pct - a.pct;
  });
  p = points.pop();

  for (var id0=0, id1=0; id0 < arcTotal0; id0++) {
    arcLen0 = nn0[id0];
    map[id0] = id1;
    n0 = 0;
    n1 = 0;
    while (n0 < arcLen0) {
      n1++;
      xx1[i1] = xx0[i0];
      yy1[i1++] = yy0[i0];
      while (p && p.i === i0) {
        xx1[i1] = p.x;
        yy1[i1++] = p.y;
        n1++;
        nn1[id1++] = n1; // end current arc at intersection
        n1 = 0;          // begin new arc

        xx1[i1] = p.x;
        yy1[i1++] = p.y;
        n1++;
        p = points.pop();
      }
      n0++;
      i0++;
    }
    nn1[id1++] = n1;
  }

  if (i1 != pointTotal1) error("[insertClippingPoints()] Counting error");
  arcs.updateVertexData(nn1, xx1, yy1, null);

  // segment-point intersections create duplicate points
  // TODO: consider removing call to dedupCoords() -- empty arcs are removed by cleanShapes()
  arcs.dedupCoords();
  return map;
};

MapShaper.findClippingPoints = function(arcs) {
  var intersections = MapShaper.findSegmentIntersections(arcs),
      data = arcs.getVertexData(),
      xx = data.xx,
      yy = data.yy,
      points = [];

  intersections.forEach(function(o) {
    var p1 = getSegmentIntersection(o.x, o.y, o.a),
        p2 = getSegmentIntersection(o.x, o.y, o.b);
    if (p1) points.push(p1);
    if (p2) points.push(p2);
  });

  // remove 1. points that are at arc endpoints and 2. duplicate points
  // (kludgy -- look into preventing these cases, which are caused by T intersections)
  var index = {};
  return points.filter(function(p) {
    var key = p.i + "," + p.pct;
    if (key in index) return false;
    index[key] = true;
    if (p.pct <= 0 && arcs.pointIsEndpoint(p.i) ||
        p.pct >= 1 && arcs.pointIsEndpoint(p.j)) {
      return false;
    }
    return true;
  });

  function getSegmentIntersection(x, y, ids) {
    var i = ids[0],
        j = ids[1],
        dx = xx[j] - xx[i],
        dy = yy[j] - yy[i],
        pct;
    if (i > j) error("[findClippingPoints()] Out-of-sequence arc ids");
    if (dx === 0 && dy === 0) {
      pct = 0;
    } else if (Math.abs(dy) > Math.abs(dx)) {
      pct = (y - yy[i]) / dy;
    } else {
      pct = (x - xx[i]) / dx;
    }

    if (pct < 0 || pct > 1) {
      verbose("[findClippingPoints()] Off-segment intersection (caused by rounding error");
      trace("pct:", pct, "dx:", dx, "dy:", dy, 'x:', x, 'y:', y, 'xx[i]:', xx[i], 'xx[j]:', xx[j], 'yy[i]:', yy[i], 'yy[j]:', yy[j]);
      trace("xpct:", (x - xx[i]) / dx, 'ypct:', (y - yy[i]) / dy);
      if (pct < 0) pct = 0;
      if (pct > 1) pct = 1;
    }

    return {
        pct: pct,
        i: i,
        j: j,
        x: x,
        y: y
      };
  }
};




// List of encodings supported by iconv-lite:
// https://github.com/ashtuchkin/iconv-lite/wiki/Supported-Encodings

// Return list of supported encodings
MapShaper.getEncodings = function() {
  var iconv = require('iconv-lite');
  iconv.encodingExists('ascii'); // make iconv load its encodings
  return Object.keys(iconv.encodings);
};

MapShaper.validateEncoding = function(enc) {
  if (!MapShaper.encodingIsSupported(enc)) {
    stop("Unknown encoding:", enc, "\nRun the -encodings command see a list of supported encodings");
  }
  return enc;
};

MapShaper.encodingIsSupported = function(raw) {
  var enc = MapShaper.standardizeEncodingName(raw);
  return utils.contains(MapShaper.getEncodings(), enc);
};

// @buf a Node Buffer
MapShaper.decodeString = function(buf, encoding) {
  var iconv = require('iconv-lite'),
      str = iconv.decode(buf, encoding);
  // remove BOM if present
  if (str.charCodeAt(0) == 0xfeff) {
    str = str.substr(1);
  }
  return str;
};

// Ex. convert UTF-8 to utf8
MapShaper.standardizeEncodingName = function(enc) {
  return enc.toLowerCase().replace(/[_-]/g, '');
};

MapShaper.printEncodings = function() {
  var encodings = MapShaper.getEncodings().filter(function(name) {
    // filter out some aliases and non-applicable encodings
    return !/^(_|cs|internal|ibm|isoir|singlebyte|table|[0-9]|l[0-9]|windows)/.test(name);
  });
  encodings.sort();
  message("Supported encodings:");
  message(MapShaper.formatStringsAsGrid(encodings));
};




// Try to detect the encoding of some sample text.
// Returns an encoding name or null.
// @samples Array of buffers containing sample text fields
// TODO: Improve reliability and number of detectable encodings.
MapShaper.detectEncoding = function(samples) {
  var encoding = null;
  if (MapShaper.looksLikeUtf8(samples)) {
    encoding = 'utf8';
  } else if (MapShaper.looksLikeWin1252(samples)) {
    // Win1252 is the same as Latin1, except it replaces a block of control
    // characters with n-dash, Euro and other glyphs. Encountered in-the-wild
    // in Natural Earth (airports.dbf uses n-dash).
    encoding = 'win1252';
  }
  return encoding;
};

// Convert an array of text samples to a single string using a given encoding
MapShaper.decodeSamples = function(enc, samples) {
  return samples.map(function(buf) {
    return MapShaper.decodeString(buf, enc).trim();
  }).join('\n');
};

MapShaper.formatSamples = function(str) {
  return MapShaper.formatStringsAsGrid(str.split('\n'));
};

// Quick-and-dirty win1251 detection: decoded string contains mostly common ascii
// chars and almost no chars other than word chars + punctuation.
// This excludes encodings like Greek, Cyrillic or Thai, but
// is susceptible to false positives with encodings like codepage 1250 ("Eastern
// European").
MapShaper.looksLikeWin1252 = function(samples) {
  var ascii = 'abcdefghijklmnopqrstuvwxyz0123456789.\'"?+-\n,:;/|_$% ', //common l.c. ascii chars
      extended = 'ßàáâãäåæçèéêëìíîïðñòóôõöøùúûüýÿ°–', // common extended
      str = MapShaper.decodeSamples('win1252', samples),
      asciiScore = MapShaper.getCharScore(str, ascii),
      totalScore = MapShaper.getCharScore(str, extended + ascii);
  return totalScore > 0.97 && asciiScore > 0.7;
};

// Accept string if it doesn't contain the "replacement character"
MapShaper.looksLikeUtf8 = function(samples) {
  var str = MapShaper.decodeSamples('utf8', samples);
  return str.indexOf('\ufffd') == -1;
};

// Calc percentage of chars in a string that are present in a second string
// @chars String of chars to look for in @str
MapShaper.getCharScore = function(str, chars) {
  var index = {},
      count = 0,
      score;
  str = str.toLowerCase();
  for (var i=0, n=chars.length; i<n; i++) {
    index[chars[i]] = 1;
  }
  for (i=0, n=str.length; i<n; i++) {
    count += index[str[i]] || 0;
  }
  return count / str.length;
};



//
// DBF format references:
// http://www.dbf2002.com/dbf-file-format.html
// http://www.digitalpreservation.gov/formats/fdd/fdd000325.shtml
// http://www.clicketyclick.dk/databases/xbase/format/index.html
// http://www.clicketyclick.dk/databases/xbase/format/data_types.html

var Dbf = {};

// source: http://webhelp.esri.com/arcpad/8.0/referenceguide/index.htm#locales/task_code.htm
Dbf.languageIds = [0x01,'437',0x02,'850',0x03,'1252',0x08,'865',0x09,'437',0x0A,'850',0x0B,'437',0x0D,'437',0x0E,'850',0x0F,'437',0x10,'850',0x11,'437',0x12,'850',0x13,'932',0x14,'850',0x15,'437',0x16,'850',0x17,'865',0x18,'437',0x19,'437',0x1A,'850',0x1B,'437',0x1C,'863',0x1D,'850',0x1F,'852',0x22,'852',0x23,'852',0x24,'860',0x25,'850',0x26,'866',0x37,'850',0x40,'852',0x4D,'936',0x4E,'949',0x4F,'950',0x50,'874',0x57,'1252',0x58,'1252',0x59,'1252',0x64,'852',0x65,'866',0x66,'865',0x67,'861',0x6A,'737',0x6B,'857',0x6C,'863',0x78,'950',0x79,'949',0x7A,'936',0x7B,'932',0x7C,'874',0x86,'737',0x87,'852',0x88,'857',0xC8,'1250',0xC9,'1251',0xCA,'1254',0xCB,'1253',0xCC,'1257'];

// Language & Language family names for some code pages
Dbf.encodingNames = {
  '932': "Japanese",
  '936': "Simplified Chinese",
  '950': "Traditional Chinese",
  '1252': "Western European",
  '949': "Korean",
  '874': "Thai",
  '1250': "Eastern European",
  '1251': "Russian",
  '1254': "Turkish",
  '1253': "Greek",
  '1257': "Baltic"
};

Dbf.ENCODING_PROMPT =
  "To avoid corrupted text, re-import using the \"encoding=\" option.\n" +
  "To see a list of supported encodings, run the \"encodings\" command.";

Dbf.lookupCodePage = function(lid) {
  var i = Dbf.languageIds.indexOf(lid);
  return i == -1 ? null : Dbf.languageIds[i+1];
};

Dbf.readAsciiString = function(bin, size) {
  var require7bit = Env.inNode;
  var str = bin.readCString(size, require7bit);
  if (str === null) {
    stop("DBF file contains non-ascii text.\n" + Dbf.ENCODING_PROMPT);
  }
  return utils.trim(str);
};

Dbf.readStringBytes = function(bin, size, buf) {
  // TODO: simplify by reading backwards from end of field
  var c;
  for (var i=0; i<size; i++) {
    c = bin.readUint8();
    if (c === 0) break;
    buf[i] = c;
  }
  // ignore trailing spaces (DBF fields are typically padded w/ spaces)
  while (i > 0 && buf[i-1] == 32) {
    i--;
  }
  return i;
};

Dbf.getEncodedStringReader = function(encoding) {
  var buf = new Buffer(256),
      isUtf8 = MapShaper.standardizeEncodingName(encoding) == 'utf8';
  return function(bin, size) {
    var eos = false,
        i = Dbf.readStringBytes(bin, size, buf),
        str;
    if (i === 0) {
      str = '';
    } else if (isUtf8) {
      str = buf.toString('utf8', 0, i);
    } else {
      str = MapShaper.decodeString(buf.slice(0, i), encoding); // slice references same memory
    }
    str = utils.trim(str);
    return str;
  };
};

Dbf.getStringReader = function(encoding) {
  if (!encoding || encoding === 'ascii') {
    return Dbf.readAsciiString;
  } else if (Env.inNode) {
    return Dbf.getEncodedStringReader(encoding);
  } else {
    // TODO: user browserify or other means of decoding string data in the browser
    error("[Dbf.getStringReader()] Non-ascii encodings only supported in Node.");
  }
};

Dbf.bufferContainsHighBit = function(buf, n) {
  for (var i=0; i<n; i++) {
    if (buf[i] >= 128) return true;
  }
  return false;
};

Dbf.readNumber = function(bin, size) {
  var str = bin.readCString(size),
      val;
  str = str.replace(',', '.'); // handle comma decimal separator
  val = parseFloat(str);
  return isNaN(val) ? null : val;
};

Dbf.readInt = function(bin, size) {
  return bin.readInt32();
};

Dbf.readBool = function(bin, size) {
  var c = bin.readCString(size),
      val = null;
  if (/[ty]/i.test(c)) val = true;
  else if (/[fn]/i.test(c)) val = false;
  return val;
};

Dbf.readDate = function(bin, size) {
  var str = bin.readCString(size),
      yr = str.substr(0, 4),
      mo = str.substr(4, 2),
      day = str.substr(6, 2);
  return new Date(Date.UTC(+yr, +mo - 1, +day));
};


// cf. http://code.google.com/p/stringencoding/
//
// @src is a Buffer or ArrayBuffer or filename
//
function DbfReader(src, encoding) {
  if (utils.isString(src)) {
    error("[DbfReader] Expected a buffer, not a string");
  }
  this.bin = new BinArray(src);
  this.header = this.readHeader(this.bin);
  this.encoding = encoding;
}

DbfReader.prototype.getEncoding = function() {
  if (!this.encoding) {
    this.encoding = this.findStringEncoding();
    if (!this.encoding) {
      // fall back to utf8 if detection fails (so GUI can continue without further errors)
      this.encoding = 'utf8';
      stop("Unable to auto-detect the text encoding of the DBF file.\n" + Dbf.ENCODING_PROMPT);
    }
  }
  return this.encoding;
};

DbfReader.prototype.rows = function() {
  return this.header.recordCount;
};

DbfReader.prototype.findStringEncoding = function() {
  var ldid = this.header.ldid,
      codepage = Dbf.lookupCodePage(ldid),
      samples = this.getNonAsciiSamples(50),
      only7bit = samples.length === 0,
      encoding, msg;

  // First, check the ldid (language driver id) (an obsolete way to specify which
  // codepage to use for text encoding.)
  // ArcGIS up to v.10.1 sets ldid and encoding based on the 'locale' of the
  // user's Windows system :P
  //
  if (codepage && ldid != 87) {
    // if 8-bit data is found and codepage is detected, use the codepage,
    // except ldid 87, which some GIS software uses regardless of encoding.
    encoding = codepage;
  } else if (only7bit) {
    // Text with no 8-bit chars should be compatible with 7-bit ascii
    // (Most encodings are supersets of ascii)
    encoding = 'ascii';
  }

  // As a last resort, try to guess the encoding:
  if (!encoding) {
    encoding = MapShaper.detectEncoding(samples);
  }

  // Show a sample of decoded text if non-ascii-range text has been found
  if (encoding && samples.length > 0) {
    msg = "Detected DBF text encoding: " + encoding;
    if (encoding in Dbf.encodingNames) {
      msg += " (" + Dbf.encodingNames[encoding] + ")";
    }
    consoleMessage(msg);
    msg = MapShaper.decodeSamples(encoding, samples);
    msg = MapShaper.formatStringsAsGrid(msg.split('\n'));
    consoleMessage("Sample text containing non-ascii characters:" + (msg.length > 60 ? '\n' : '') + msg);
  }
  return encoding;
};

// Return up to @size buffers containing text samples
// with at least one byte outside the 7-bit ascii range.
// TODO: filter out duplicate samples
DbfReader.prototype.getNonAsciiSamples = function(size) {
  var samples = [];
  var stringFields = this.header.fields.filter(function(f) {
    return f.type == 'C';
  });
  var rowOffs = this.getRowOffset();
  var buf = new Buffer(256);
  var index = {};
  var f, chars, sample, hash;
  for (var r=0, rows=this.rows(); r<rows; r++) {
    for (var c=0, cols=stringFields.length; c<cols; c++) {
      if (samples.length >= size) break;
      f = stringFields[c];
      this.bin.position(rowOffs(r) + f.columnOffset);
      chars = Dbf.readStringBytes(this.bin, f.size, buf);
      if (chars > 0 && Dbf.bufferContainsHighBit(buf, chars)) {
        sample = new Buffer(buf.slice(0, chars)); //
        hash = sample.toString('hex');
        if (hash in index === false) { // avoid duplicate samples
          index[hash] = true;
          samples.push(sample);
        }
      }
    }
  }
  return samples;
};

DbfReader.prototype.getRowOffset = function() {
  var start = this.header.headerSize,
      recLen = this.header.recordSize;
  return function(r) {
    return start + recLen * r;
  };
};

DbfReader.prototype.getRecordReader = function(header) {
  var fields = header.fields,
      readers = fields.map(this.getFieldReader, this),
      uniqNames = MapShaper.getUniqFieldNames(utils.pluck(fields, 'name')),
      rowOffs = this.getRowOffset(),
      bin = this.bin;
  return function(r) {
    var rec = {},
        offs = rowOffs(r),
        field;
    for (var c=0, cols=fields.length; c<cols; c++) {
      field = fields[c];
      bin.position(offs + field.columnOffset);
      rec[uniqNames[c]] = readers[c](bin, field.size);
    }
    return rec;
  };
};

// @f Field metadata from dbf header
DbfReader.prototype.getFieldReader = function(f) {
  var type = f.type,
      r = null;
  if (type == 'I') {
    r = Dbf.readInt;
  } else if (type == 'F' || type == 'N') {
    r = Dbf.readNumber;
  } else if (type == 'L') {
    r = Dbf.readBool;
  } else if (type == 'D') {
    r = Dbf.readDate;
  } else if (type == 'C') {
    r = Dbf.getStringReader(this.getEncoding());
  } else {
    message("[dbf] Field \"" + field.name + "\" has an unsupported type (" + field.type + ") -- converting to null values");
    r = function() {return null;};
  }
  return r;
};

DbfReader.prototype.readRows = function() {
  var data = [],
      reader = this.getRecordReader(this.header);
  for (var r=0, rows=this.rows(); r<rows; r++) {
    data.push(reader(r));
  }
  return data;
};

DbfReader.prototype.readHeader = function(bin, encoding) {
  bin.position(0).littleEndian();
  var header = {
    version: bin.readInt8(),
    updateYear: bin.readUint8(),
    updateMonth: bin.readUint8(),
    updateDay: bin.readUint8(),
    recordCount: bin.readUint32(),
    headerSize: bin.readUint16(),
    recordSize: bin.readUint16(),
    incompleteTransaction: bin.skipBytes(2).readUint8(),
    encrypted: bin.readUint8(),
    mdx: bin.skipBytes(12).readUint8(),
    ldid: bin.readUint8()
  };
  var colOffs = 1; // first column starts on second byte of record
  var field;
  bin.skipBytes(2);
  header.fields = [];
  // stop at ascii newline or carriage return (LF is standard, CR has been used)
  while (bin.peek() != 0x0D && bin.peek() != 0x0A) {
    field = this.readFieldHeader(bin, encoding);
    field.columnOffset = colOffs;
    header.fields.push(field);
    colOffs += field.size;
  }
  if (colOffs != header.recordSize)
    error("Record length mismatch; header:", header.recordSize, "detected:", colOffs);
  return header;
};

DbfReader.prototype.readFieldHeader = function(bin, encoding) {
  return {
    name: bin.readCString(11),
    type: String.fromCharCode(bin.readUint8()),
    address: bin.readUint32(),
    size: bin.readUint8(),
    decimals: bin.readUint8(),
    id: bin.skipBytes(2).readUint8(),
    position: bin.skipBytes(2).readUint8(),
    indexFlag: bin.skipBytes(7).readUint8()
  };
};

// export for testing
MapShaper.Dbf = Dbf;
MapShaper.DbfReader = DbfReader;




Dbf.MAX_STRING_LEN = 254;

Dbf.exportRecords = function(arr, encoding) {
  encoding = encoding || 'ascii';
  var fields = Dbf.getFieldNames(arr);
  var uniqFields = MapShaper.getUniqFieldNames(fields, 10);
  var rows = arr.length;
  var fieldData = fields.map(function(name) {
    return Dbf.getFieldInfo(arr, name, encoding);
  });

  var headerBytes = Dbf.getHeaderSize(fieldData.length),
      recordBytes = Dbf.getRecordSize(utils.pluck(fieldData, 'size')),
      fileBytes = headerBytes + rows * recordBytes + 1;

  var buffer = new ArrayBuffer(fileBytes);
  var bin = new BinArray(buffer).littleEndian();
  var now = new Date();

  // write header
  bin.writeUint8(3);
  bin.writeUint8(now.getFullYear() - 1900);
  bin.writeUint8(now.getMonth() + 1);
  bin.writeUint8(now.getDate());
  bin.writeUint32(rows);
  bin.writeUint16(headerBytes);
  bin.writeUint16(recordBytes);
  bin.skipBytes(17);
  bin.writeUint8(0); // language flag; TODO: improve this
  bin.skipBytes(2);

  // field subrecords
  fieldData.reduce(function(recordOffset, obj, i) {
    var fieldName = uniqFields[i];
    bin.writeCString(fieldName, 11);
    bin.writeUint8(obj.type.charCodeAt(0));
    bin.writeUint32(recordOffset);
    bin.writeUint8(obj.size);
    bin.writeUint8(obj.decimals);
    bin.skipBytes(14);
    return recordOffset + obj.size;
  }, 1);

  bin.writeUint8(0x0d); // "field descriptor terminator"
  if (bin.position() != headerBytes) {
    error("Dbf#exportRecords() header size mismatch; expected:", headerBytes, "written:", bin.position());
  }

  arr.forEach(function(rec, i) {
    var start = bin.position();
    bin.writeUint8(0x20); // delete flag; 0x20 valid 0x2a deleted
    for (var j=0, n=fieldData.length; j<n; j++) {
      fieldData[j].write(i, bin);
    }
    if (bin.position() - start != recordBytes) {
      error("#exportRecords() Error exporting record:", rec);
    }
  });

  bin.writeUint8(0x1a); // end-of-file

  if (bin.position() != fileBytes) {
    error("Dbf#exportRecords() file size mismatch; expected:", fileBytes, "written:", bin.position());
  }
  return buffer;
};


Dbf.getFieldNames = function(records) {
  if (!records || !records.length) {
    return [];
  }
  var names = Object.keys(records[0]);
  names.sort(); // kludge: sorting gives correct order when truncating fields
  return names;
};


Dbf.getHeaderSize = function(numFields) {
  return 33 + numFields * 32;
};

Dbf.getRecordSize = function(fieldSizes) {
  return utils.sum(fieldSizes) + 1; // delete byte plus data bytes
};

/*
Dbf.getValidFieldName = function(name) {
  // TODO: handle non-ascii chars in name
  return name.substr(0, 10); // max 10 chars
};
*/

Dbf.initNumericField = function(info, arr, name) {
  var MAX_FIELD_SIZE = 18,
      size;

  data = this.getNumericFieldInfo(arr, name);
  info.decimals = data.decimals;
  size = Math.max(data.max.toFixed(info.decimals).length,
      data.min.toFixed(info.decimals).length);
  if (size > MAX_FIELD_SIZE) {
    size = MAX_FIELD_SIZE;
    info.decimals -= size - MAX_FIELD_SIZE;
    if (info.decimals < 0) {
      error ("Dbf#getFieldInfo() Out-of-range error.");
    }
  }
  info.size = size;

  var formatter = Dbf.getDecimalFormatter(size, info.decimals);
  info.write = function(i, bin) {
    var rec = arr[i],
        str = formatter(rec[name]);
    if (str.length < size) {
      str = utils.lpad(str, size, ' ');
    }
    bin.writeString(str, size);
  };
};

Dbf.initBooleanField = function(info, arr, name) {
  info.size = 1;
  info.write = function(i, bin) {
    var val = arr[i][name],
        c;
    if (val === true) c = 'T';
    else if (val === false) c = 'F';
    else c = '?';
    bin.writeString(c);
  };
};

Dbf.initDateField = function(info, arr, name) {
  info.size = 8;
  info.write = function(i, bin) {
    var d = arr[i][name],
        str;
    if (d instanceof Date === false) {
      str = '00000000';
    } else {
      str = utils.lpad(d.getUTCFullYear(), 4, '0') +
            utils.lpad(d.getUTCMonth() + 1, 2, '0') +
            utils.lpad(d.getUTCDate(), 2, '0');
    }
    bin.writeString(str);
  };
};

Dbf.initStringField = function(info, arr, name, encoding) {
  var formatter = Dbf.getStringWriter(encoding);
  var size = 0;
  var values = arr.map(function(rec) {
    var buf = formatter(rec[name]);
    size = Math.max(size, buf.byteLength);
    return buf;
  });
  info.size = size;
  info.write = function(i, bin) {
    var buf = values[i],
        bytes = Math.min(size, buf.byteLength),
        idx = bin.position();
    bin.writeBuffer(buf, bytes, 0);
    bin.position(idx + size);
  };
};

Dbf.getFieldInfo = function(arr, name, encoding) {
  var type = this.discoverFieldType(arr, name),
      info = {
        name: name,
        type: type,
        decimals: 0
      };
  if (type == 'N') {
    Dbf.initNumericField(info, arr, name);
  } else if (type == 'C') {
    Dbf.initStringField(info, arr, name, encoding);
  } else if (type == 'L') {
    Dbf.initBooleanField(info, arr, name);
  } else if (type == 'D') {
    Dbf.initDateField(info, arr, name);
  } else {
    // Treat null fields as empty numeric fields; this way, they will be imported
    // again as nulls.
    info.size = 0;
    info.type = 'N';
    info.write = function() {};
  }
  return info;
};

Dbf.discoverFieldType = function(arr, name) {
  var val;
  for (var i=0, n=arr.length; i<n; i++) {
    val = arr[i][name];
    if (utils.isString(val)) return "C";
    if (utils.isNumber(val)) return "N";
    if (utils.isBoolean(val)) return "L";
    if (val instanceof Date) return "D";
  }
  return null;
};

Dbf.getDecimalFormatter = function(size, decimals) {
  // TODO: find better way to handle nulls
  var nullValue = ' '; // ArcGIS may use 0
  return function(val) {
    // TODO: handle invalid values better
    var valid = utils.isFiniteNumber(val),
        strval = valid ? val.toFixed(decimals) : String(nullValue);
    return utils.lpad(strval, size, ' ');
  };
};

Dbf.getNumericFieldInfo = function(arr, name) {
  var maxDecimals = 0,
      limit = 15,
      min = Infinity,
      max = -Infinity,
      k = 1,
      val, decimals;
  for (var i=0, n=arr.length; i<n; i++) {
    val = arr[i][name];
    if (!utils.isFiniteNumber(val)) {
      continue;
    }
    decimals = 0;
    if (val < min) min = val;
    if (val > max) max = val;
    while (val * k % 1 !== 0) {
      if (decimals == limit) {
        // TODO: verify limit, remove oflo message, round overflowing values
        // trace ("#getNumericFieldInfo() Number field overflow; value:", val);
        break;
      }
      decimals++;
      k *= 10;
    }
    if (decimals > maxDecimals) maxDecimals = decimals;
  }
  return {
    decimals: maxDecimals,
    min: min,
    max: max
  };
};

// Return function to convert a JS str to an ArrayBuffer containing encoded str.
Dbf.getStringWriter = function(encoding) {
  if (encoding === 'ascii') {
    return Dbf.getStringWriterAscii();
  } else {
    return Dbf.getStringWriterEncoded(encoding);
  }
};

// TODO: handle non-ascii chars. Option: switch to
// utf8 encoding if non-ascii chars are found.
Dbf.getStringWriterAscii = function() {
  return function(val) {
    var str = String(val),
        n = Math.min(str.length, Dbf.MAX_STRING_LEN),
        dest = new ArrayBuffer(n),
        view = new Uint8ClampedArray(dest);
    for (var i=0; i<n; i++) {
      view[i] = str.charCodeAt(i);
    }
    return dest;
  };
};

Dbf.getStringWriterEncoded = function(encoding) {
  var iconv = require('iconv-lite');
  return function(val) {
    var buf = iconv.encode(val, encoding);
    if (buf.length >= Dbf.MAX_STRING_LEN) {
      buf = Dbf.truncateEncodedString(buf, encoding, Dbf.MAX_STRING_LEN);
    }
    return BinArray.toArrayBuffer(buf);
  };
};

// try to remove partial multi-byte characters from the end of an encoded string.
Dbf.truncateEncodedString = function(buf, encoding, maxLen) {
  var truncated = buf.slice(0, maxLen);
  var len = maxLen;
  var tmp, str;
  while (len > 0 && len >= maxLen - 3) {
    tmp = len == maxLen ? truncated : buf.slice(0, len);
    str = MapShaper.decodeString(tmp, encoding);
    if (str.charAt(str.length-1) != '\ufffd') {
      truncated = tmp;
      break;
    }
    len--;
  }
  return truncated;
};




var dataFieldRxp = /^[a-zA-Z_][a-zA-Z_0-9]*$/;

function DataTable(obj) {
  var records;
  if (utils.isArray(obj)) {
    records = obj;
  } else {
    records = [];
    // integer object: create empty records
    if (utils.isInteger(obj)) {
      for (var i=0; i<obj; i++) {
        records.push({});
      }
    } else if (obj) {
      error("[DataTable] Invalid constructor argument:", obj);
    }
  }

  this.exportAsDbf = function(encoding) {
    return Dbf.exportRecords(records, encoding);
  };

  this.getRecords = function() {
    return records;
  };
}

var dataTableProto = {
  fieldExists: function(name) {
    return utils.contains(this.getFields(), name);
  },

  exportAsJSON: function() {
    return JSON.stringify(this.getRecords());
  },

  addField: function(name, init) {
    var useFunction = utils.isFunction(init);
    if (!utils.isNumber(init) && !utils.isString(init) && !useFunction) {
      error("DataTable#addField() requires a string, number or function for initialization");
    }
    if (this.fieldExists(name)) error("DataTable#addField() tried to add a field that already exists:", name);
    if (!dataFieldRxp.test(name)) error("DataTable#addField() invalid field name:", name);

    this.getRecords().forEach(function(obj, i) {
      obj[name] = useFunction ? init(obj, i) : init;
    });
  },

  addIdField: function() {
    this.addField('FID', function(obj, i) {
      return i;
    });
  },

  deleteField: function(f) {
    this.getRecords().forEach(function(o) {
      delete o[f];
    });
  },

  getFields: function() {
    var records = this.getRecords();
    return records.length > 0 ? Object.keys(records[0]) : [];
  },

  update: function(f) {
    var records = this.getRecords();
    for (var i=0, n=records.length; i<n; i++) {
      records[i] = f(records[i], i);
    }
  },

  clone: function() {
    var records2 = this.getRecords().map(function(rec) {
      return utils.extend({}, rec);
    });
    return new DataTable(records2);
  },

  size: function() {
    return this.getRecords().length;
  }
};

utils.extend(DataTable.prototype, dataTableProto);

// export for testing
MapShaper.DataTable = DataTable;




// Generate a dissolved layer
// @opts.field (optional) name of data field (dissolves all if falsy)
// @opts.sum-fields (Array) (optional)
// @opts.copy-fields (Array) (optional)
api.dissolvePolygons = // TODO: remove deprecated name
api.dissolve = function(lyr, arcs, opts) {
  var getGroupId = MapShaper.getCategoryClassifier(opts.field, lyr.data),
      dissolveShapes = null,
      dissolveData = null,
      lyr2;

  if (lyr.geometry_type) {
    MapShaper.requirePolygonLayer(lyr, "[dissolve] Only polygon type layers can be dissolved");
    dissolveShapes = dissolvePolygonGeometry(lyr.shapes, getGroupId);
  }
  if (lyr.data) {
    dissolveData = MapShaper.calcDissolveData(lyr.data.getRecords(), getGroupId, opts);
    // replace missing shapes with nulls
    for (var i=0, n=dissolveData.length; i<n; i++) {
      if (dissolveShapes && !dissolveShapes[i]) {
        dissolveShapes[i] = null;
      }
    }
  }
  lyr2 = {
    name: opts.no_replace ? null : lyr.name,
    shapes: dissolveShapes,
    data: dissolveData ? new DataTable(dissolveData) : null,
    geometry_type: lyr.geometry_type
  };
  if (!opts.silent) {
    MapShaper.printDissolveMessage(lyr, lyr2);
  }
  return lyr2;
};

MapShaper.printDissolveMessage = function(pre, post, cmd) {
  var n1 = MapShaper.getFeatureCount(pre),
      n2 = MapShaper.getFeatureCount(post),
      msg = utils.format('[%s] Dissolved %,d feature%s into %,d feature%s',
        cmd || 'dissolve', n1, utils.pluralSuffix(n1), n2,
        utils.pluralSuffix(n2));
  message(msg);
};

// Get a function to convert original feature ids into ids of combined features
// Use categorical classification (a different id for each unique value)
MapShaper.getCategoryClassifier = function(field, data) {
  if (!field) return function(i) {return 0;};
  if (!data || !data.fieldExists(field)) {
    stop("[dissolve] Data table is missing field:", field);
  }
  var index = {},
      count = 0,
      records = data.getRecords();
  return function(i) {
    var val = String(records[i][field]);
    if (val in index === false) {
      index[val] = count++;
    }
    return index[val];
  };
};

function dissolvePolygonGeometry(shapes, getGroupId) {
  var segments = dissolveFirstPass(shapes, getGroupId);
  return dissolveSecondPass(segments, shapes, getGroupId);
}

// First pass -- identify pairs of segments that can be dissolved
function dissolveFirstPass(shapes, getGroupId) {
  var groups = [],
      largeGroups = [],
      segments = [],
      ids = shapes.map(function(shp, i) {
        return getGroupId(i);
      });

  MapShaper.traverseShapes(shapes, procArc);
  largeGroups.forEach(splitGroup);
  return segments;

  function procArc(obj) {
    var arcId = obj.arcId,
        idx = arcId < 0 ? ~arcId : arcId,
        segId = segments.length,
        group = groups[idx];
    if (!group) {
      group = [];
      groups[idx] = group;
    }
    group.push(segId);
    obj.group = group;
    segments.push(obj);

    // Three or more segments sharing the same arc is abnormal topology...
    // Need to try to identify pairs of matching segments in each of these
    // groups.
    //
    if (group.length == 3) {
      largeGroups.push(group);
    }
  }

  function findMatchingPair(group, cb) {
    var arc1, arc2;
    for (var i=0; i<group.length - 1; i++) {
      arc1 = segments[group[i]];
      for (var j=i+1; j<group.length; j++) {
        arc2 = segments[group[j]];
        if (cb(arc1, arc2)) {
          return [arc1.segId, arc2.segId];
        }
      }
    }
    return null;
  }

  function checkFwExtension(arc1, arc2) {
    return getNextSegment(arc1, segments, shapes).arcId ===
        ~getNextSegment(arc2, segments, shapes).arcId;
  }

  function checkBwExtension(arc1, arc2) {
    return getPrevSegment(arc1, segments, shapes).arcId ===
        ~getPrevSegment(arc2, segments, shapes).arcId;
  }

  function checkDoubleExtension(arc1, arc2) {
    return checkPairwiseMatch(arc1, arc2) &&
        checkFwExtension(arc1, arc2) &&
        checkBwExtension(arc1, arc2);
  }

  function checkSingleExtension(arc1, arc2) {
    return checkPairwiseMatch(arc1, arc2) &&
        (checkFwExtension(arc1, arc2) ||
        checkBwExtension(arc1, arc2));
  }

  function checkPairwiseMatch(arc1, arc2) {
    return arc1.arcId === ~arc2.arcId && ids[arc1.shapeId] ===
        ids[arc2.shapeId];
  }

  function updateGroupIds(ids) {
    ids.forEach(function(id) {
      segments[id].group = ids;
    });
  }

  // split a group of segments into pairs of matching segments + a residual group
  // @group Array of segment ids
  //
  function splitGroup(group) {
    // find best-match segment pair
    var group2 = findMatchingPair(group, checkDoubleExtension) ||
        findMatchingPair(group, checkSingleExtension) ||
        findMatchingPair(group, checkPairwiseMatch);
    if (group2) {
      group = group.filter(function(i) {
        return !utils.contains(group2, i);
      });
      updateGroupIds(group);
      updateGroupIds(group2);
      // Split again if reduced group is still large
      if (group.length > 2) splitGroup(group);
    }
  }
}

// Second pass -- generate dissolved shapes
//
function dissolveSecondPass(segments, shapes, getGroupId) {
  var dissolveShapes = [];
  segments.forEach(procSegment);
  return dissolveShapes;

  // @obj is an arc instance
  function procSegment(obj) {
    if (obj.used) return;
    var match = findDissolveArc(obj);
    if (!match) buildRing(obj);
  }

  function addRing(arcs, i) {
    if (i in dissolveShapes === false) {
      dissolveShapes[i] = [];
    }
    dissolveShapes[i].push(arcs);
  }

  // Generate a dissolved ring
  // @firstArc the first arc instance in the ring
  //
  function buildRing(firstArc) {
    var newArcs = [firstArc.arcId],
        nextArc = getNextArc(firstArc);
        firstArc.used = true;

    while (nextArc && nextArc != firstArc) {
      newArcs.push(nextArc.arcId);
      nextArc.used = true;
      nextArc = getNextArc(nextArc);
      if (nextArc && nextArc != firstArc && nextArc.used) error("buildRing() topology error");
    }

    if (!nextArc) error("buildRing() traversal error");
    firstArc.used = true;
    addRing(newArcs, getGroupId(firstArc.shapeId));
  }

  // Get the next arc in a dissolved polygon ring
  // @obj an undissolvable arc instance
  //
  function getNextArc(obj, depth) {
    var next = getNextSegment(obj, segments, shapes),
        match;
    depth = depth || 0;
    if (next != obj) {
      match = findDissolveArc(next);
      if (match) {
        if (depth > 100) {
          error ('[dissolve] deep recursion -- unhandled topology problem');
        }
        // if (match.part.arcs.length == 1) {
        if (shapes[match.shapeId][match.partId].length == 1) {
          // case: @obj has an island inclusion -- keep traversing @obj
          // TODO: test case if @next is first arc in the ring
          next = getNextArc(next, depth + 1);
        } else {
          next = getNextArc(match, depth + 1);
        }
      }
    }
    return next;
  }

  // Look for an arc instance that can be dissolved with segment @obj
  // (must be going the opposite direction and have same dissolve key, etc)
  // Return matching segment or null if no match
  //
  function findDissolveArc(obj) {
    var dissolveId = getGroupId(obj.shapeId), // obj.shape.dissolveKey,
        match, matchId;
    matchId = utils.find(obj.group, function(i) {
      var a = obj,
          b = segments[i];
      if (a == b ||
          b.used ||
          getGroupId(b.shapeId) !== dissolveId ||
          // don't prevent rings from dissolving with themselves (risky?)
          // a.shapeId == b.shapeId && a.partId == b.partId ||
          a.arcId != ~b.arcId) return false;
      return true;
    });
    match = matchId === null ? null : segments[matchId];
    return match;
  }
}

function getNextSegment(seg, segments, shapes) {
  return getSegmentByOffs(seg, segments, shapes, 1);
}

function getPrevSegment(seg, segments, shapes) {
  return getSegmentByOffs(seg, segments, shapes, -1);
}

function getSegmentByOffs(seg, segments, shapes, offs) {
  var arcs = shapes[seg.shapeId][seg.partId],
      partLen = arcs.length,
      nextOffs = (seg.i + offs) % partLen,
      nextSeg;
  if (nextOffs < 0) nextOffs += partLen;
  nextSeg = segments[seg.segId - seg.i + nextOffs];
  if (!nextSeg || nextSeg.shapeId != seg.shapeId) error("index error");
  return nextSeg;
}

// Return a properties array for a set of dissolved shapes
// Records contain dissolve field data (or are empty if not dissolving on a field)
// TODO: copy other user-specified fields
//
// @properties original records
// @index hash of dissolve shape ids, indexed on dissolve keys
//
MapShaper.calcDissolveData = function(properties, getGroupId, opts) {
  var arr = [];
  var sumFields = opts.sum_fields || [],
      copyFields = opts.copy_fields || [];

  if (opts.field) {
    copyFields.push(opts.field);
  }

  properties.forEach(function(rec, i) {
    if (!rec) return;
    var idx = getGroupId(i),
        dissolveRec;

    if (idx in arr) {
      dissolveRec = arr[idx];
    } else {
      arr[idx] = dissolveRec = {};
      copyFields.forEach(function(f) {
        dissolveRec[f] = rec[f];
      });
    }

    sumFields.forEach(function(f) {
      // TODO: handle strings
      dissolveRec[f] = (rec[f] || 0) + (dissolveRec[f] || 0);
    });
  });
  return arr;
};




api.dissolvePolygons2 = function(lyr, dataset, opts) {
  MapShaper.requirePolygonLayer(lyr, "[dissolve2] Expected a polygon type layer");
  var nodes = MapShaper.divideArcs(dataset);
  return MapShaper.dissolvePolygonLayer(lyr, nodes, opts);
};

MapShaper.dissolvePolygonLayer = function(lyr, nodes, opts) {
  opts = opts || {};
  var getGroupId = MapShaper.getCategoryClassifier(opts.field, lyr.data);
  var groups = lyr.shapes.reduce(function(groups, shape, i) {
    var i2 = getGroupId(i);
    if (i2 in groups === false) {
      groups[i2] = [];
    }
    MapShaper.extendShape(groups[i2], shape);
    return groups;
  }, []);
  var dissolve = MapShaper.getPolygonDissolver(nodes);
  var lyr2, data2;

  T.start();
  if (lyr.data) {
    data2 = new DataTable(MapShaper.calcDissolveData(lyr.data.getRecords(), getGroupId, opts));
  }
  lyr2 = {
    name: opts.no_replace ? null : lyr.name,
    data: data2,
    shapes: groups.map(dissolve),
    geometry_type: lyr.geometry_type
  };
  T.stop('dissolve2');
  MapShaper.printDissolveMessage(lyr, lyr2, 'dissolve2');
  return lyr2;
};

MapShaper.concatShapes = function(shapes) {
  return shapes.reduce(function(memo, shape) {
    MapShaper.extendShape(memo, shape);
    return memo;
  }, []);
};

MapShaper.extendShape = function(dest, src) {
  if (src) {
    for (var i=0, n=src.length; i<n; i++) {
      dest.push(src[i]);
    }
  }
};

MapShaper.getPolygonDissolver = function(nodes, spherical) {
  spherical = spherical && !nodes.arcs.isPlanar();
  var flags = new Uint8Array(nodes.arcs.size());
  var divide = MapShaper.getHoleDivider(nodes, spherical);
  var flatten = MapShaper.getRingIntersector(nodes, 'flatten', flags, spherical);
  var dissolve = MapShaper.getRingIntersector(nodes, 'dissolve', flags, spherical);

  return function(shp) {
    if (!shp) return null;
    var cw = [],
        ccw = [];

    divide(shp, cw, ccw);
    cw = flatten(cw);
    ccw.forEach(MapShaper.reversePath);
    ccw = flatten(ccw);
    ccw.forEach(MapShaper.reversePath);

    var shp2 = MapShaper.appendHolestoRings(cw, ccw);
    var dissolved = dissolve(shp2);
    return dissolved.length > 0 ? dissolved : null;
  };
};

// TODO: to prevent invalid holes,
// could erase the holes from the space-enclosing rings.
MapShaper.appendHolestoRings = function(cw, ccw) {
  for (var i=0, n=ccw.length; i<n; i++) {
    cw.push(ccw[i]);
  }
  return cw;
};




// assumes layers and arcs have been prepared for clipping
MapShaper.clipPolygons = function(targetShapes, clipShapes, nodes, type) {
  var arcs = nodes.arcs;
  var clipFlags = new Uint8Array(arcs.size());
  var routeFlags = new Uint8Array(arcs.size());
  var clipArcTouches = 0;
  var clipArcUses = 0;
  var usedClipArcs = [];
  var dividePath = MapShaper.getPathFinder(nodes, useRoute, routeIsActive, chooseRoute);
  var dissolvePolygon = MapShaper.getPolygonDissolver(nodes);

  // clean each target polygon by dissolving its rings
  targetShapes = targetShapes.map(dissolvePolygon);

  // merge rings of clip/erase polygons and dissolve them all
  clipShapes = [dissolvePolygon(MapShaper.concatShapes(clipShapes))];

  // Open pathways in the clip/erase layer
  // Need to expose clip/erase routes in both directions by setting route
  // in both directions to visible -- this is how cut-out shapes are detected
  // Or-ing with 0x11 makes both directions visible (so reverse paths will block)
  MapShaper.openArcRoutes(clipShapes, arcs, clipFlags, type == 'clip', type == 'erase', !!"dissolve", 0x11);

  var index = new PathIndex(clipShapes, arcs);
  var clippedShapes = targetShapes.map(function(shape) {
    if (shape) {
      return clipPolygon(shape, type, index);
    }
    return null;
  });

  // add clip/erase polygons that are fully contained in a target polygon
  // need to index only non-intersecting clip shapes
  // (Intersecting shapes have one or more arcs that have been scanned)
  //
  var undividedClipShapes = findUndividedClipShapes(clipShapes);

  MapShaper.closeArcRoutes(clipShapes, arcs, routeFlags, true, true); // not needed?
  index = new PathIndex(undividedClipShapes, arcs);
  targetShapes.forEach(function(shape, shapeId) {
    var paths = shape ? findInteriorPaths(shape, type, index) : null;
    if (paths) {
      clippedShapes[shapeId] = (clippedShapes[shapeId] || []).concat(paths);
    }
  });

  return clippedShapes;

  function clipPolygon(shape, type, index) {
    var dividedShape = [],
        clipping = type == 'clip',
        erasing = type == 'erase';

    // open pathways for entire polygon rather than one ring at a time --
    // need to create polygons that connect positive-space rings and holes
    MapShaper.openArcRoutes(shape, arcs, routeFlags, true, false, false);

    MapShaper.forEachPath(shape, function(ids) {
      var path;
      for (var i=0, n=ids.length; i<n; i++) {
        clipArcTouches = 0;
        clipArcUses = 0;
        path = dividePath(ids[i]);
        if (path) {
          // if ring doesn't touch/intersect a clip/erase polygon, check if it is contained
          // if (clipArcTouches === 0) {
          // if ring doesn't incorporate an arc from the clip/erase polygon,
          // check if it is contained (assumes clip shapes are dissolved)
          if (clipArcTouches === 0 || clipArcUses === 0) { //
            var contained = index.pathIsEnclosed(path);
            if (clipping && contained || erasing && !contained) {
              dividedShape.push(path);
            }
            // TODO: Consider breaking if polygon is unchanged
          } else {
            dividedShape.push(path);
          }
        }
      }
    });

    // Clear pathways of current target shape to hidden/closed
    MapShaper.closeArcRoutes(shape, arcs, routeFlags, true, true, true);
    // Also clear pathways of any clip arcs that were used
    if (usedClipArcs.length > 0) {
      MapShaper.closeArcRoutes(usedClipArcs, arcs, routeFlags, true, true, true);
      usedClipArcs = [];
    }

    return dividedShape.length === 0 ? null : dividedShape;
  }

  function routeIsActive(id) {
    var fw = id >= 0,
        abs = fw ? id : ~id,
        visibleBit = fw ? 1 : 0x10,
        targetBits = routeFlags[abs],
        clipBits = clipFlags[abs];

    if (clipBits > 0) clipArcTouches++;
    return (targetBits & visibleBit) > 0 || (clipBits & visibleBit) > 0;
  }

  function useRoute(id) {
    var fw = id >= 0,
        abs = fw ? id : ~id,
        targetBits = routeFlags[abs],
        clipBits = clipFlags[abs],
        targetRoute, clipRoute;

    if (fw) {
      targetRoute = targetBits;
      clipRoute = clipBits;
    } else {
      targetRoute = targetBits >> 4;
      clipRoute = clipBits >> 4;
    }
    targetRoute &= 3;
    clipRoute &= 3;

    var usable = false;
    // var usable = targetRoute === 3 || targetRoute === 0 && clipRoute == 3;
    if (targetRoute == 3) {
      // special cases where clip route and target route both follow this arc
      if (clipRoute == 1) {
        // 1. clip/erase polygon blocks this route, not usable
      } else if (clipRoute == 2 && type == 'erase') {
        // 2. route is on the boundary between two erase polygons, not usable
      } else {
        usable = true;
      }

    } else if (targetRoute === 0 && clipRoute == 3) {
      usedClipArcs.push(id);
      usable = true;
    }

    if (usable) {
      if (clipRoute == 3) {
        clipArcUses++;
      }
      // Need to close all arcs after visiting them -- or could cause a cycle
      //   on layers with strange topology
      if (fw) {
        targetBits = MapShaper.setBits(targetBits, 1, 3);
      } else {
        targetBits = MapShaper.setBits(targetBits, 0x10, 0x30);
      }
    }

    targetBits |= fw ? 4 : 0x40; // record as visited
    routeFlags[abs] = targetBits;
    return usable;
  }

  function chooseRoute(id1, angle1, id2, angle2, prevId) {
    var selection = 1;
    if (angle1 == angle2) {
      // less likely now that congruent arcs are prevented in updateArcIds()
      var bits2 = MapShaper.getRouteBits(id2, routeFlags);
      if (bits2 == 3) { // route2 follows a target layer arc; prefer it
        selection = 2;
      }
    } else {
      // prefer right-hand angle
      if (angle2 < angle1) {
        selection = 2;
      }
    }
    return selection;
  }

  // Filter a collection of shapes to exclude paths that contain clip/erase arcs
  // and paths that are hidden (e.g. internal boundaries)
  function findUndividedClipShapes(clipShapes) {
    return clipShapes.map(function(shape) {
      var usableParts = [];
      MapShaper.forEachPath(shape, function(ids) {
        var pathIsClean = true,
            pathIsVisible = false;
        for (var i=0; i<ids.length; i++) {
          // check if arc was used in fw or rev direction
          if (!arcIsUnused(ids[i], routeFlags)) {
            pathIsClean = false;
            break;
          }
          // check if clip arc is visible
          if (!pathIsVisible && arcIsVisible(ids[i], clipFlags)) {
            pathIsVisible = true;
          }
        }
        if (pathIsClean && pathIsVisible) usableParts.push(ids);
      });
      return usableParts.length > 0 ? usableParts : null;
    });
  }

  // Test if arc is unused in both directions
  // (not testing open/closed or visible/hidden)
  function arcIsUnused(id, flags) {
    var abs = absArcId(id),
        flag = flags[abs];
        return (flag & 0x44) === 0;
  }

  function arcIsVisible(id, flags) {
    var flag = flags[absArcId(id)];
    return (flag & 0x11) > 0;
  }

  // search for indexed clipping paths contained in a shape
  // dissolve them if needed
  function findInteriorPaths(shape, type, index) {
    var enclosedPaths = index.findPathsInsideShape(shape),
        dissolvedPaths = [];
    if (!enclosedPaths) return null;
    // ...
    if (type == 'erase') enclosedPaths.forEach(MapShaper.reversePath);
    if (enclosedPaths.length <= 1) {
      dissolvedPaths = enclosedPaths; // no need to dissolve single-part paths
    } else {
      MapShaper.openArcRoutes(enclosedPaths, arcs, routeFlags, true, false, true);
      enclosedPaths.forEach(function(ids) {
        var path;
        for (var j=0; j<ids.length; j++) {
          path = dividePath(ids[j]);
          if (path) {
            dissolvedPaths.push(path);
          }
        }
      });
    }

    return dissolvedPaths.length > 0 ? dissolvedPaths : null;
  }
}; // end clipPolygons()




// Assumes: Arcs have been divided
//
MapShaper.clipPolylines = function(targetShapes, clipShapes, nodes, type) {
  var index = new PathIndex(clipShapes, nodes.arcs);

  return targetShapes.map(function(shp) {
    return clipPolyline(shp);
  });

  function clipPolyline(shp) {
    var clipped = shp.reduce(clipPath, []);
    return clipped.length > 0 ? clipped : null;
  }

  function clipPath(memo, path) {
    var clippedPath = null,
        arcId, enclosed;
    for (var i=0; i<path.length; i++) {
      arcId = path[i];
      enclosed = index.arcIsEnclosed(arcId);
      if (enclosed && type == 'clip' || !enclosed && type == 'erase') {
        if (!clippedPath) {
          memo.push(clippedPath = []);
        }
        clippedPath.push(arcId);
      } else {
        clippedPath = null;
      }
    }
    return memo;
  }
};




//
MapShaper.clipPoints = function(points, clipShapes, arcs, type) {
  var index = new PathIndex(clipShapes, arcs);

  var points2 = points.reduce(function(memo, feat) {
    var n = feat ? feat.length : 0,
        feat2 = [],
        enclosed;

    for (var i=0; i<n; i++) {
      enclosed = index.findEnclosingShape(feat[i]) > -1;
      if (type == 'clip' && enclosed || type == 'erase' && !enclosed) {
        feat2.push(feat[i].concat());
      }
    }

    memo.push(feat2.length > 0 ? feat2 : null);
    return memo;
  }, []);

  return points2;
};




api.convertPolygonsToInnerLines = function(lyr, arcs, opts) {
  if (lyr.geometry_type != 'polygon') {
    stop("[innerlines] Command requires a polygon layer");
  }
  var arcs2 = MapShaper.convertShapesToArcs(lyr.shapes, arcs.size(), 'inner'),
      lyr2 = MapShaper.convertArcsToLineLayer(arcs2, null);
  if (lyr2.shapes.length === 0) {
    message("[innerlines] No shared boundaries were found");
  }
  lyr2.name = opts && opts.no_replace ? null : lyr.name;
  return lyr2;
};

api.convertPolygonsToTypedLines = function(lyr, arcs, fields, opts) {
  if (lyr.geometry_type != 'polygon') {
    stop("[lines] Command requires a polygon layer");
  }
  var arcCount = arcs.size(),
      outerArcs = MapShaper.convertShapesToArcs(lyr.shapes, arcCount, 'outer'),
      typeCode = 0,
      allArcs = [],
      allData = [],
      innerArcs, lyr2;

  function addArcs(typeArcs) {
    var typeData = utils.repeat(typeArcs.length, function(i) {
          return {TYPE: typeCode};
        }) || [];
    allArcs = utils.merge(typeArcs, allArcs);
    allData = utils.merge(typeData, allData);
    typeCode++;
  }

  addArcs(outerArcs);

  if (utils.isArray(fields)) {
    if (!lyr.data) {
      stop("[lines] Missing a data table:");
    }
    fields.forEach(function(field) {
      if (!lyr.data.fieldExists(field)) {
        stop("[lines] Unknown data field:", field);
      }
      var dissolved = api.dissolve(lyr, arcs, {field: field, silent: true}),
          dissolvedArcs = MapShaper.convertShapesToArcs(dissolved.shapes, arcCount, 'inner');
      dissolvedArcs = utils.difference(dissolvedArcs, allArcs);
      addArcs(dissolvedArcs);
    });
  }

  innerArcs = MapShaper.convertShapesToArcs(lyr.shapes, arcCount, 'inner');
  innerArcs = utils.difference(innerArcs, allArcs);
  addArcs(innerArcs);
  lyr2 = MapShaper.convertArcsToLineLayer(allArcs, allData);
  lyr2.name = opts && opts.no_replace ? null : lyr.name;
  return lyr2;
};


MapShaper.convertArcsToLineLayer = function(arcs, data) {
  var shapes = MapShaper.convertArcsToShapes(arcs),
      lyr = {
        geometry_type: 'polyline',
        shapes: shapes
      };
  if (data) {
    lyr.data = new DataTable(data);
  }
  return lyr;
};

MapShaper.convertArcsToShapes = function(arcs) {
  return arcs.map(function(id) {
    return [[id]];
  });
};

MapShaper.convertShapesToArcs = function(shapes, arcCount, type) {
  type = type || 'all';
  var counts = new Uint8Array(arcCount),
      arcs = [],
      count;

  MapShaper.countArcsInShapes(shapes, counts);

  for (var i=0, n=counts.length; i<n; i++) {
    count = counts[i];
    if (count > 0) {
      if (type == 'all' || type == 'outer' && count == 1 ||
          type == 'inner' && count > 1) {
        arcs.push(i);
      }
    }
  }
  return arcs;
};




// Dissolve arcs that can be merged without affecting topology of layers
// remove arcs that are not referenced by any layer; remap arc ids
// in layers. (In-place).
MapShaper.dissolveArcs = function(dataset) {
  var arcs = dataset.arcs,
      layers = dataset.layers.filter(MapShaper.layerHasPaths),
      test = MapShaper.getArcDissolveTest(layers, arcs),
      groups = [],
      totalPoints = 0,
      arcIndex = new Int32Array(arcs.size()), // maps old arc ids to new ids
      arcStatus = new Uint8Array(arcs.size());
      // arcStatus: 0 = unvisited, 1 = dropped, 2 = remapped, 3 = remapped + reversed
  layers.forEach(function(lyr) {
    // modify copies of the original shapes; original shapes should be unmodified
    // (need to test this)
    lyr.shapes = lyr.shapes.map(function(shape) {
      return MapShaper.editPaths(shape && shape.concat(), translatePath);
    });
  });
  MapShaper.dissolveArcCollection(arcs, groups, totalPoints);

  function translatePath(path) {
    var pointCount = 0;
    var path2 = [];
    var group, arcId, absId, arcLen, fw, arcId2;

    for (var i=0, n=path.length; i<n; i++) {
      arcId = path[i];
      absId = absArcId(arcId);
      fw = arcId === absId;

      if (arcs.arcIsDegenerate(arcId)) {
        // skip
      } else if (arcStatus[absId] === 0) {
        arcLen = arcs.getArcLength(arcId);

        if (group && test(path[i-1], arcId)) {
          if (arcLen > 0) {
            arcLen--; // shared endpoint not counted;
          }
          group.push(arcId);  // arc data is appended to previous arc
          arcStatus[absId] = 1; // arc is dropped from output
        } else {
          // new group (i.e. new dissolved arc)
          group = [arcId];
          arcIndex[absId] = groups.length;
          groups.push(group);
          arcStatus[absId] = fw ? 2 : 3; // 2: unchanged; 3: reversed
        }
        pointCount += arcLen;
      } else {
        group = null;
      }

      if (arcStatus[absId] > 1) {
        // arc is retained (and renumbered) in the dissolved path.
        arcId2 = arcIndex[absId];
        if (fw && arcStatus[absId] == 3 || !fw && arcStatus[absId] == 2) {
          arcId2 = ~arcId2;
        }
        path2.push(arcId2);
      }
    }
    totalPoints += pointCount;
    return path2;
  }
};

MapShaper.dissolveArcCollection = function(arcs, groups, len2) {
  var nn2 = new Uint32Array(groups.length),
      xx2 = new Float64Array(len2),
      yy2 = new Float64Array(len2),
      src = arcs.getVertexData(),
      zz2 = src.zz ? new Float64Array(len2) : null,
      offs = 0;

  groups.forEach(function(group, newId) {
    group.forEach(function(oldId, i) {
      extendDissolvedArc(oldId, newId);
    });
  });

  arcs.updateVertexData(nn2, xx2, yy2, zz2);

  function extendDissolvedArc(oldId, newId) {
    var absId = absArcId(oldId),
        rev = oldId < 0,
        n = src.nn[absId],
        i = src.ii[absId],
        n2 = nn2[newId];

    if (n > 0) {
      if (n2 > 0) {
        n--;
        if (!rev) i++;
      }
      MapShaper.copyElements(src.xx, i, xx2, offs, n, rev);
      MapShaper.copyElements(src.yy, i, yy2, offs, n, rev);
      if (zz2) MapShaper.copyElements(src.zz, i, zz2, offs, n, rev);
      nn2[newId] += n;
      offs += n;
    }
  }
};

MapShaper.getArcDissolveTest = function(layers, arcs) {
  var nodes = MapShaper.getFilteredNodeCollection(layers, arcs),
      count = 0,
      lastId;

  return function(id1, id2) {
    if (id1 == id2 || id1 == ~id2) {
      verbose("Unexpected arc sequence:", id1, id2);
      return false; // This is unexpected; don't try to dissolve, anyway
    }
    count = 0;
    nodes.forEachConnectedArc(id1, countArc);
    return count == 1 && lastId == ~id2;
  };

  function countArc(arcId, i) {
    count++;
    lastId = arcId;
  }
};

MapShaper.getFilteredNodeCollection = function(layers, arcs) {
  var counts = MapShaper.countArcReferences(layers, arcs),
      test = function(arcId) {
        return counts[absArcId(arcId)] > 0;
      };
  return new NodeCollection(arcs, test);
};

MapShaper.countArcReferences = function(layers, arcs) {
  var counts = new Uint32Array(arcs.size());
  layers.forEach(function(lyr) {
    MapShaper.countArcsInShapes(lyr.shapes, counts);
  });
  return counts;
};




MapShaper.simplifyArcsFast = function(arcs, dist) {
  var xx = [],
      yy = [],
      nn = [],
      count;
  for (var i=0, n=arcs.size(); i<n; i++) {
    count = MapShaper.simplifyPathFast([i], arcs, dist, xx, yy);
    if (count == 1) {
      count = 0;
      xx.pop();
      yy.pop();
    }
    nn.push(count);
  }
  return new ArcCollection(nn, xx, yy);
};

MapShaper.simplifyPolygonFast = function(shp, arcs, dist) {
  if (!shp || !dist) return null;
  var xx = [],
      yy = [],
      nn = [],
      shp2 = [];

  shp.forEach(function(path) {
    var count = MapShaper.simplifyPathFast(path, arcs, dist, xx, yy);
    while (count < 4 && count > 0) {
      xx.pop();
      yy.pop();
      count--;
    }
    if (count > 0) {
      shp2.push([nn.length]);
      nn.push(count);
    }
  });
  return {
    shape: shp2.length > 0 ? shp2 : null,
    arcs: new ArcCollection(nn, xx, yy)
  };
};

MapShaper.simplifyPathFast = function(path, arcs, dist, xx, yy) {
  var iter = arcs.getShapeIter(path),
      count = 0,
      prevX, prevY, x, y;
  while (iter.hasNext()) {
    x = iter.x;
    y = iter.y;
    if (count === 0 || distance2D(x, y, prevX, prevY) > dist) {
      xx.push(x);
      yy.push(y);
      prevX = x;
      prevY = y;
      count++;
    }
  }
  if (x != prevX || y != prevY) {
    xx.push(x);
    yy.push(y);
    count++;
  }
  return count;
};




// Get the centroid of the largest ring of a polygon
// TODO: Include holes in the calculation
// TODO: Add option to find centroid of all rings, not just the largest
geom.getShapeCentroid = function(shp, arcs) {
  var maxPath = geom.getMaxPath(shp, arcs);
  return maxPath ? geom.getPathCentroid(maxPath, arcs) : null;
};

geom.getPathCentroid = function(ids, arcs) {
  var iter = arcs.getShapeIter(ids),
      sum = 0,
      sumX = 0,
      sumY = 0,
      ax, ay, tmp, area;
  if (!iter.hasNext()) return null;
  ax = iter.x;
  ay = iter.y;
  while (iter.hasNext()) {
    tmp = ax * iter.y - ay * iter.x;
    sum += tmp;
    sumX += tmp * (iter.x + ax);
    sumY += tmp * (iter.y + ay);
    ax = iter.x;
    ay = iter.y;
  }
  area = sum / 2;
  if (area === 0) {
    return geom.getAvgPathXY(ids, arcs);
  } else return {
    x: sumX / (6 * area),
    y: sumY / (6 * area)
  };
};

// Find a point inside a polygon and located away from the polygon edge
// Method:
// - get the largest ring of the polygon
// - get an array of x-values distributed along the horizontal extent of the ring
// - for each x:
//     intersect a vertical line with the polygon at x
//     find midpoints of each intersecting segment
// - for each midpoint:
//     adjust point vertically to maximize weighted distance from polygon edge
// - return the adjusted point having the maximum weighted distance from the edge
//
// (distance is weighted to slightly favor points near centroid)
//
geom.findInteriorPoint = function(shp, arcs) {
  var maxPath = shp && geom.getMaxPath(shp, arcs),
      pathBounds = maxPath && arcs.getSimpleShapeBounds(maxPath),
      thresh, simple;
  if (!pathBounds || !pathBounds.hasBounds() || pathBounds.area() === 0) {
    return null;
  }
  thresh = Math.sqrt(pathBounds.area()) * 0.01;
  simple = MapShaper.simplifyPolygonFast(shp, arcs, thresh);
  if (!simple.shape) {
    return null; // collapsed shape
  }
  return geom.findInteriorPoint2(simple.shape, simple.arcs);
};

// Assumes: shp is a polygon with at least one space-enclosing ring
geom.findInteriorPoint2 = function(shp, arcs) {
  var maxPath = geom.getMaxPath(shp, arcs);
  var pathBounds = arcs.getSimpleShapeBounds(maxPath);
  var centroid = geom.getPathCentroid(maxPath, arcs);
  var weight = MapShaper.getPointWeightingFunction(centroid, pathBounds);
  var area = geom.getPlanarPathArea(maxPath, arcs);
  var hrange, lbound, rbound, focus, htics, hstep, p, p2;

  // Limit test area if shape is simple and squarish
  if (shp.length == 1 && area * 1.2 > pathBounds.area()) {
    htics = 5;
    focus = 0.2;
  } else if (shp.length == 1 && area * 1.7 > pathBounds.area()) {
    htics = 7;
    focus = 0.4;
  } else {
    htics = 11;
    focus = 0.5;
  }
  hrange = pathBounds.width() * focus;
  lbound = centroid.x - hrange / 2;
  rbound = lbound + hrange;
  hstep = hrange / htics;

  // Find a best-fit point
  p = MapShaper.probeForBestInteriorPoint(shp, arcs, lbound, rbound, htics, weight);
  if (!p) {
    verbose("[points inner] failed, falling back to centroid");
   p = centroid;
  } else {
    // Look for even better fit close to best-fit point
    p2 = MapShaper.probeForBestInteriorPoint(shp, arcs, p.x - hstep / 2,
        p.x + hstep / 2, 2, weight);
    if (p2.distance > p.distance) {
      p = p2;
    }
  }
  return p;
};

MapShaper.getPointWeightingFunction = function(centroid, pathBounds) {
  // Get a factor for weighting a candidate point
  // Points closer to the centroid are slightly preferred
  var referenceDist = Math.max(pathBounds.width(), pathBounds.height()) / 2;
  return function(x, y) {
    var offset = distance2D(centroid.x, centroid.y, x, y);
    return 1 - Math.min(0.6 * offset / referenceDist, 0.25);
  };
};

MapShaper.findInteriorPointCandidates = function(shp, arcs, xx) {
  var ymin = arcs.getBounds().ymin - 1;
  return xx.reduce(function(memo, x) {
    var cands = MapShaper.findHitCandidates(x, ymin, shp, arcs);
    return memo.concat(cands);
  }, []);
};

MapShaper.probeForBestInteriorPoint = function(shp, arcs, lbound, rbound, htics, weight) {
  var tics = MapShaper.getInnerTics(lbound, rbound, htics);
  var interval = (rbound - lbound) / htics;
  // Get candidate points, distributed along x-axis
  var candidates = MapShaper.findInteriorPointCandidates(shp, arcs, tics);
  var bestP, adjustedP, candP;

  // Sort candidates so points at the center of longer segments are tried first
  candidates.forEach(function(p) {
    p.interval *= weight(p.x, p.y);
  });
  candidates.sort(function(a, b) {
    return b.interval - a.interval;
  });

  for (var i=0; i<candidates.length; i++) {
    candP = candidates[i];
    // Optimization: Stop searching if weighted half-segment length of remaining
    //   points is less than the weighted edge distance of the best candidate
    if (bestP && bestP.distance > candP.interval) {
      break;
    }
    adjustedP = MapShaper.getAdjustedPoint(candP.x, candP.y, shp, arcs, interval, weight);

    if (!bestP || adjustedP.distance > bestP.distance) {
      bestP = adjustedP;
    }
  }
  return bestP;
};

// [x, y] is a point assumed to be inside a polygon @shp
// Try to move the point farther from the polygon edge
MapShaper.getAdjustedPoint = function(x, y, shp, arcs, vstep, weight) {
  var p = {
    x: x,
    y: y,
    distance: geom.getPointToShapeDistance(x, y, shp, arcs) * weight(x, y)
  };
  MapShaper.scanForBetterPoint(p, shp, arcs, vstep, weight); // scan up
  MapShaper.scanForBetterPoint(p, shp, arcs, -vstep, weight); // scan down
  return p;
};

// Try to find a better-fit point than @p by scanning vertically
// Modify p in-place
MapShaper.scanForBetterPoint = function(p, shp, arcs, vstep, weight) {
  var x = p.x,
      y = p.y,
      dmax = p.distance,
      d;

  while (true) {
    y += vstep;
    d = geom.getPointToShapeDistance(x, y, shp, arcs) * weight(x, y);
    // overcome vary small local minima
    if (d > dmax * 0.90 && geom.testPointInPolygon(x, y, shp, arcs)) {
      if (d > dmax) {
        p.distance = dmax = d;
        p.y = y;
      }
    } else {
      break;
    }
  }
};

// Return array of points at the midpoint of each line segment formed by the
//   intersection of a vertical ray at [x, y] and a polygon shape
MapShaper.findHitCandidates = function(x, y, shp, arcs) {
  var yy = MapShaper.findRayShapeIntersections(x, y, shp, arcs);
  var cands = [], y1, y2, interval;

  // sortying by y-coord organizes y-intercepts into interior segments
  utils.genericSort(yy);
  for (var i=0; i<yy.length; i+=2) {
    y1 = yy[i];
    y2 = yy[i+1];
    interval = (y2 - y1) / 2;
    if (interval > 0) {
      cands.push({
        y: (y1 + y2) / 2,
        x: x,
        interval: interval
      });
    }
  }
  return cands;
};

// Return array of y-intersections between vertical ray with origin at [x, y]
//   and a polygon
MapShaper.findRayShapeIntersections = function(x, y, shp, arcs) {
  if (!shp) return [];
  return shp.reduce(function(memo, path) {
    var yy = MapShaper.findRayRingIntersections(x, y, path, arcs);
    return memo.concat(yy);
  }, []);
};

// Return array of y-intersections between vertical ray and a polygon ring
MapShaper.findRayRingIntersections = function(x, y, path, arcs) {
  var yints = [];
  MapShaper.forEachPathSegment(path, arcs, function(a, b, xx, yy) {
    var result = geom.getRayIntersection(x, y, xx[a], yy[a], xx[b], yy[b]);
    if (result > -Infinity) {
      yints.push(result);
    }
  });
  // Ignore odd number of intersections -- probably caused by a ray that touches
  //   but doesn't cross the ring
  // TODO: improve method to handle edge case with two touches and no crosses.
  if (yints.length % 2 === 1) {
    yints = [];
  }
  return yints;
};

// TODO: find better home + name for this
MapShaper.getInnerTics = function(min, max, steps) {
  var range = max - min,
      step = range / (steps + 1),
      arr = [];
  for (var i = 1; i<=steps; i++) {
    arr.push(min + step * i);
  }
  return arr;
};




MapShaper.compileFeatureExpression = function(rawExp, lyr, arcs) {
  var RE_ASSIGNEE = /[A-Za-z_][A-Za-z0-9_]*(?= *=[^=])/g,
      exp = MapShaper.validateExpression(rawExp),
      newFields = exp.match(RE_ASSIGNEE) || null,
      env = MapShaper.getBaseContext(),
      records,
      func;

  if (newFields && !lyr.data) {
    lyr.data = new DataTable(MapShaper.getFeatureCount(lyr));
  }
  if (lyr.data) records = lyr.data.getRecords();

  env.$ = new FeatureExpressionContext(lyr, arcs);
  try {
    func = new Function("record,env", "with(env){with(record) { return " +
        MapShaper.removeExpressionSemicolons(exp) + "}}");
  } catch(e) {
    stop(e.name, "in expression [" + exp + "]");
  }

  var compiled = function(recId) {
    var record = records ? records[recId] || (records[recId] = {}) : {},
        value, f;

    // initialize new fields to null so assignments work
    if (newFields) {
      for (var i=0; i<newFields.length; i++) {
        f = newFields[i];
        if (f in record === false) {
          record[f] = null;
        }
      }
    }
    env.$.__setId(recId);
    try {
      value = func.call(null, record, env);
    } catch(e) {
      stop(e.name, "in expression [" + exp + "]:", e.message);
    }
    return value;
  };

  compiled.context = env;
  return compiled;
};

MapShaper.getBaseContext = function() {
  var obj = {};
  // Mask global properties (is this effective/worth doing?)
  (function() {
    for (var key in this) {
      obj[key] = null;
    }
  }());
  obj.console = console;
  return obj;
};

MapShaper.validateExpression = function(exp) {
  exp = exp || '';
  return MapShaper.removeExpressionSemicolons(exp);
};

// Semicolons that divide the expression into two or more js statements
// cause problems when 'return' is added before the expression
// (only the first statement is evaluated). Replacing with commas fixes this
//
MapShaper.removeExpressionSemicolons = function(exp) {
  if (exp.indexOf(';') != -1) {
    // remove any ; from end of expression
    exp = exp.replace(/[; ]+$/, '');
    // change any other semicolons to commas
    // (this is not very safe -- what if a string literal contains a semicolon?)
    exp = exp.replace(/;/g, ',');
  }
  return exp;
};

function addGetters(obj, getters) {
  Object.keys(getters).forEach(function(name) {
    Object.defineProperty(obj, name, {get: getters[name]});
  });
}

function FeatureExpressionContext(lyr, arcs) {
  var hasData = !!lyr.data,
      hasPoints = MapShaper.layerHasPoints(lyr),
      hasPaths = arcs && MapShaper.layerHasPaths(lyr),
      _isPlanar,
      _self = this,
      _centroid, _innerXY, _xy,
      _record, _records,
      _id, _ids, _bounds;

  if (hasData) {
    _records = lyr.data.getRecords();
    Object.defineProperty(this, 'properties',
      {set: function(obj) {
        if (utils.isObject(obj)) {
          _records[_id] = obj;
        } else {
          stop("Can't assign non-object to $.properties");
        }
      }, get: function() {
        var rec = _records[_id];
        if (!rec) {
          rec = _records[_id] = {};
        }
        return rec;
      }});
  }

  if (hasPaths) {
    _isPlanar = arcs.isPlanar();
    addGetters(this, {
      // TODO: count hole/s + containing ring as one part
      partCount: function() {
        return _ids ? _ids.length : 0;
      },
      isNull: function() {
        return this.partCount === 0;
      },
      bounds: function() {
        return shapeBounds().toArray();
      },
      height: function() {
        return shapeBounds().height();
      },
      width: function() {
        return shapeBounds().width();
      }
    });

    if (lyr.geometry_type == 'polygon') {
      addGetters(this, {
        area: function() {
          return _isPlanar ? geom.getPlanarShapeArea(_ids, arcs) : geom.getSphericalShapeArea(_ids, arcs);
        },
        originalArea: function() {
          var i = arcs.getRetainedInterval(),
              area;
          arcs.setRetainedInterval(0);
          area = _self.area;
          arcs.setRetainedInterval(i);
          return area;
        },
        centroidX: function() {
          var p = centroid();
          return p ? p.x : null;
        },
        centroidY: function() {
          var p = centroid();
          return p ? p.y : null;
        },
        innerX: function() {
          var p = innerXY();
          return p ? p.x : null;
        },
        innerY: function() {
          var p = innerXY();
          return p ? p.y : null;
        }
      });
    }

  } else if (hasPoints) {
    // TODO: add functions like bounds, isNull, pointCount
    Object.defineProperty(this, 'coordinates',
      {set: function(obj) {
        if (!obj || utils.isArray(obj)) {
          lyr.shapes[_id] = obj || null;
        } else {
          stop("Can't assign non-array to $.coordinates");
        }
      }, get: function() {
        return lyr.shapes[_id] || null;
      }});

    addGetters(this, {
      x: function() {
        xy();
        return _xy ? _xy[0] : null;
      },
      y: function() {
        xy();
        return _xy ? _xy[1] : null;
      }
    });
  }

  // all contexts have $.id
  addGetters(this, {id: function() { return _id; }});

  this.__setId = function(id) {
    _id = id;
    if (hasPaths) {
      _bounds = null;
      _centroid = null;
      _innerXY = null;
      _ids = lyr.shapes[id];
    }
    if (hasPoints) {
      _xy = null;
    }
    if (hasData) {
      _record = _records[id];
    }
  };

  function xy() {
    var shape = lyr.shapes[_id];
    if (!_xy) {
      _xy = shape && shape[0] || null;
    }
    return _xy;
  }

  function centroid() {
    _centroid = _centroid || geom.getShapeCentroid(_ids, arcs);
    return _centroid;
  }

  function innerXY() {
    _innerXY = _innerXY || geom.findInteriorPoint(_ids, arcs);
    return _innerXY;
  }

  function shapeBounds() {
    if (!_bounds) {
      _bounds = arcs.getMultiShapeBounds(_ids);
    }
    return _bounds;
  }
}




api.filterFeatures = function(lyr, arcs, opts) {
  var records = lyr.data ? lyr.data.getRecords() : null,
      shapes = lyr.shapes || null,
      n = MapShaper.getFeatureCount(lyr),
      filteredShapes = shapes ? [] : null,
      filteredRecords = records ? [] : null,
      filteredLyr = MapShaper.getOutputLayer(lyr, opts),
      filter;

  if (opts.expression) {
    filter = MapShaper.compileFeatureExpression(opts.expression, lyr, arcs);
  }

  if (opts.remove_empty) {
    filter = MapShaper.combineFilters(filter, MapShaper.getNullGeometryFilter(lyr, arcs));
  }

  if (!filter) {
    stop("[filter] Missing a filter expression");
  }

  utils.repeat(n, function(shapeId) {
    var result = filter(shapeId);
    if (result === true) {
      if (shapes) filteredShapes.push(shapes[shapeId] || null);
      if (records) filteredRecords.push(records[shapeId] || null);
    } else if (result !== false) {
      stop("[filter] Expressions must return true or false");
    }
  });

  filteredLyr.shapes = filteredShapes;
  filteredLyr.data = filteredRecords ? new DataTable(filteredRecords) : null;
  if (opts.no_replace) {
    // if adding a layer, don't share objects between source and filtered layer
    filteredLyr = MapShaper.copyLayer(filteredLyr);
  }

  if (opts.verbose !== false) {
    message(utils.format('[filter] Retained %,d of %,d features', MapShaper.getFeatureCount(filteredLyr), n));
  }

  return filteredLyr;
};

MapShaper.getNullGeometryFilter = function(lyr, arcs) {
  var shapes = lyr.shapes;
  if (lyr.geometry_type == 'polygon') {
    return MapShaper.getEmptyPolygonFilter(shapes, arcs);
  }
  return function(i) {return !!shapes[i];};
};

MapShaper.getEmptyPolygonFilter = function(shapes, arcs) {
  return function(i) {
    var shp = shapes[i];
    return !!shp && geom.getPlanarShapeArea(shapes[i], arcs) > 0;
  };
};

MapShaper.combineFilters = function(a, b) {
  return (a && b && function(id) {
      return a(id) && b(id);
    }) || a || b;
};




api.filterIslands = function(lyr, arcs, opts) {
  var removed = 0;
  if (lyr.geometry_type != 'polygon') {
    return;
  }

  if (opts.min_area || opts.min_vertices) {
    if (opts.min_area) {
      removed += MapShaper.filterIslands(lyr, arcs, MapShaper.getRingAreaTest(opts.min_area, arcs));
    }
    if (opts.min_vertices) {
      removed += MapShaper.filterIslands(lyr, arcs, MapShaper.getVertexCountTest(opts.min_vertices, arcs));
    }
    if (opts.remove_empty) {
      api.filterFeatures(lyr, arcs, {remove_empty: true, verbose: false});
    }
    message(utils.format("Removed %'d island%s", removed, utils.pluralSuffix(removed)));
  } else {
    message("[filter-islands] Missing a criterion for filtering islands; use min-area or min-vertices");
  }
};

MapShaper.getVertexCountTest = function(minVertices, arcs) {
  return function(path) {
    // first and last vertex in ring count as one
    return geom.countVerticesInPath(path, arcs) <= minVertices;
  };
};

MapShaper.getRingAreaTest = function(minArea, arcs) {
  var pathArea = arcs.isPlanar() ? geom.getPlanarPathArea : geom.getSphericalPathArea;
  return function(path) {
    var area = pathArea(path, arcs);
    return Math.abs(area) < minArea;
  };
};

MapShaper.filterIslands = function(lyr, arcs, ringTest) {
  var removed = 0;
  var counts = new Uint8Array(arcs.size());
  MapShaper.countArcsInShapes(lyr.shapes, counts);

  var pathFilter = function(path, i, paths) {
    if (path.length == 1) { // got an island ring
      if (counts[absArcId(path[0])] === 1) { // and not part of a donut hole
        if (!ringTest || ringTest(path)) { // and it meets any filtering criteria
          // and it does not contain any holes itself
          // O(n^2), so testing this last
          if (!MapShaper.ringHasHoles(path, paths, arcs)) {
            removed++;
            return null;
          }
        }
      }
    }
  };
  MapShaper.filterShapes(lyr.shapes, pathFilter);
  return removed;
};

MapShaper.ringIntersectsBBox = function(ring, bbox, arcs) {
  for (var i=0, n=ring.length; i<n; i++) {
    if (arcs.arcIntersectsBBox(absArcId(ring[i]), bbox)) {
      return true;
    }
  }
  return false;
};

// Assumes that ring boundaries to not cross
MapShaper.ringHasHoles = function(ring, rings, arcs) {
  var bbox = arcs.getSimpleShapeBounds2(ring);
  var sibling, p;
  for (var i=0, n=rings.length; i<n; i++) {
    sibling = rings[i];
    // try to avoid expensive point-in-ring test
    if (sibling && sibling != ring && MapShaper.ringIntersectsBBox(sibling, bbox, arcs)) {
      p = arcs.getVertex(sibling[0], 0);
      if (geom.testPointInRing(p.x, p.y, ring, arcs)) {
        return true;
      }
    }
  }
  return false;
};

MapShaper.filterShapes = function(shapes, pathFilter) {
  var shapeFilter = function(paths) {
    return MapShaper.editPaths(paths, pathFilter);
  };
  for (var i=0, n=shapes.length; i<n; i++) {
    shapes[i] = shapeFilter(shapes[i]);
  }
};




// Remove small-area polygon rings (very simple implementation of sliver removal)
// TODO: more sophisticated sliver detection (e.g. could consider ratio of area to perimeter)
// TODO: consider merging slivers into adjacent polygons to prevent gaps from forming
// TODO: consider separate gap removal function as an alternative to merging slivers
//
api.filterSlivers = function(lyr, arcs, opts) {
  if (lyr.geometry_type != 'polygon') {
    return 0;
  }
  return MapShaper.filterSlivers(lyr, arcs, opts);
};

MapShaper.filterSlivers = function(lyr, arcs, opts) {
  var ringTest = MapShaper.getSliverTest(arcs, opts && opts.min_area);
  var removed = 0;
  var pathFilter = function(path, i, paths) {
    if (ringTest(path)) {
      removed++;
      return null;
    }
  };

  MapShaper.filterShapes(lyr.shapes, pathFilter);
  return removed;
};

MapShaper.filterClipSlivers = function(lyr, clipLyr, arcs) {
  var flags = new Uint8Array(arcs.size());
  var ringTest = MapShaper.getSliverTest(arcs);
  var removed = 0;
  var pathFilter = function(path) {
    var clipped = false;
    var absId;
    for (var i=0, n=path && path.length || 0; i<n; i++) {
      if (flags[absArcId(path[i])] > 0) {
        clipped = true;
        break;
      }
    }
    if (clipped && ringTest(path)) {
      removed++;
      return null;
    }
  };

  MapShaper.countArcsInShapes(clipLyr.shapes, flags);
  MapShaper.filterShapes(lyr.shapes, pathFilter);
  return removed;
};

MapShaper.calcDefaultSliverArea = function(arcs) {
  var xy = arcs.getAvgSegment2();
  return xy[0] * xy[1]; // TODO: do some testing to find a better default
};

MapShaper.getSliverTest = function(arcs, minArea) {
  var pathArea;
  if (minArea) {
    pathArea = arcs.isPlanar() ? geom.getPlanarPathArea : geom.getSphericalPathArea;
  } else {
    // use planar area if no min area is given
    pathArea = geom.getPlanarPathArea;
    minArea = MapShaper.calcDefaultSliverArea(arcs);
  }
  return function(path) {
    var area = pathArea(path, arcs);
    return Math.abs(area) < minArea;
  };
};




api.clipLayers = function(target, src, dataset, opts) {
  return MapShaper.clipLayers(target, src, dataset, "clip", opts);
};

api.eraseLayers = function(target, src, dataset, opts) {
  return MapShaper.clipLayers(target, src, dataset, "erase", opts);
};

api.clipLayer = function(targetLyr, src, dataset, opts) {
  return api.clipLayers([targetLyr], src, dataset, opts)[0];
};

api.eraseLayer = function(targetLyr, src, dataset, opts) {
  return api.eraseLayers([targetLyr], src, dataset, opts)[0];
};

// @target: a single layer or an array of layers
// @type: 'clip' or 'erase'
MapShaper.clipLayers = function(targetLayers, src, srcDataset, type, opts) {
  var clipLyr =  MapShaper.getClipLayer(src, srcDataset, opts),
      usingPathClip = utils.some(targetLayers, MapShaper.layerHasPaths),
      nullCount = 0, sliverCount = 0,
      nodes, outputLayers, dataset;
  opts = opts || {};
  MapShaper.requirePolygonLayer(clipLyr, "[" + type + "] Requires a polygon clipping layer");

  // If clipping layer was imported from a second file, it won't be included in
  // dataset
  // (assuming that clipLyr arcs have been merged with dataset.arcs)
  //
  if (utils.contains(srcDataset.layers, clipLyr) === false) {
    dataset = {
      layers: [clipLyr].concat(srcDataset.layers),
      arcs: srcDataset.arcs
    };
  } else {
    dataset = srcDataset;
  }

  if (usingPathClip) {
    nodes = MapShaper.divideArcs(dataset);
  }

  outputLayers = targetLayers.map(function(targetLyr) {
    var shapeCount = targetLyr.shapes ? targetLyr.shapes.length : 0;
    var clippedShapes, outputLyr;
    if (targetLyr === clipLyr) {
      stop('[' + type + '] Can\'t clip a layer with itself');
    } else if (targetLyr.geometry_type == 'point') {
      clippedShapes = MapShaper.clipPoints(targetLyr.shapes, clipLyr.shapes, dataset.arcs, type);
    } else if (targetLyr.geometry_type == 'polygon') {
      clippedShapes = MapShaper.clipPolygons(targetLyr.shapes, clipLyr.shapes, nodes, type);
    } else if (targetLyr.geometry_type == 'polyline') {
      clippedShapes = MapShaper.clipPolylines(targetLyr.shapes, clipLyr.shapes, nodes, type);
    } else {
      stop('[' + type + '] Invalid target layer:', targetLyr.name);
    }

    outputLyr = MapShaper.getOutputLayer(targetLyr, opts);
    if (opts.no_replace && targetLyr.data) {
      outputLyr.data = targetLyr.data.clone();
    }
    outputLyr.shapes = clippedShapes;

    // Remove sliver polygons
    if (opts.cleanup && outputLyr.geometry_type == 'polygon') {
      sliverCount += MapShaper.filterClipSlivers(outputLyr, clipLyr, dataset.arcs);
    }

    // Remove null shapes (likely removed by clipping/erasing)
    api.filterFeatures(outputLyr, dataset.arcs, {remove_empty: true, verbose: false});
    nullCount += shapeCount - outputLyr.shapes.length;
    return outputLyr;
  });

  // Cleanup is set by option parser; use no-cleanup to disable
  if (usingPathClip && opts.cleanup) {
    // Delete unused arcs, merge remaining arcs, remap arcs of retained shapes.
    // This is to remove arcs belonging to the clipping paths from the target
    // dataset, and to heal the cuts that were made where clipping paths
    // crossed target paths
    dataset = {arcs: srcDataset.arcs, layers: srcDataset.layers};
    if (opts.no_replace) {
      dataset.layers = dataset.layers.concat(outputLayers);
    } else {
      MapShaper.replaceLayers(dataset, targetLayers, outputLayers);
    }
    MapShaper.dissolveArcs(dataset);
  }

  if (nullCount && sliverCount) {
    message(MapShaper.getClipMessage(type, nullCount, sliverCount));
  }

  return outputLayers;
};


MapShaper.getClipMessage = function(type, nullCount, sliverCount) {
  var nullMsg = nullCount ? utils.format('%,d null feature%s', nullCount, utils.pluralSuffix(nullCount)) : '';
  var sliverMsg = sliverCount ? utils.format('%,d sliver%s', sliverCount, utils.pluralSuffix(sliverCount)) : '';
  if (nullMsg || sliverMsg) {
    return utils.format('[%s] Removed %s%s%s', type, nullMsg, (nullMsg && sliverMsg ? ' and ' : ''), sliverMsg);
  }
  return '';
};

// @src: a layer object, layer identifier or filename
MapShaper.getClipLayer = function(src, dataset, opts) {
  var clipLayers, clipDataset, mergedDataset;
  if (utils.isObject(src)) {
    // src is layer object
    return src;
  }
  // check if src is the name of an existing layer
  if (src) {
    clipLayers = MapShaper.findMatchingLayers(dataset.layers, src);
    if (clipLayers.length > 1) {
      stop("[clip/erase] Received more than one source layer");
    } else if (clipLayers.length == 1) {
      return clipLayers[0];
    }
  }
  if (src) {
    // assuming src is a filename
    clipDataset = MapShaper.readClipFile(src, opts);
    if (!clipDataset) {
      stop("Unable to find file [" + src + "]");
    }
    // TODO: handle multi-layer sources, e.g. TopoJSON files
    if (clipDataset.layers.length != 1) {
      stop("Clip/erase only supports clipping with single-layer datasets");
    }
  } else if (opts.bbox) {
    clipDataset = MapShaper.convertClipBounds(opts.bbox);
  } else {
    stop("[clip/erase] Missing clipping data");
  }
  mergedDataset = MapShaper.mergeDatasets([dataset, clipDataset]);
  api.buildTopology(mergedDataset);

  // use arcs from merged dataset, but don't add clip layer to target dataset
  dataset.arcs = mergedDataset.arcs;
  return clipDataset.layers[0];
};

// @src Filename
MapShaper.readClipFile = function(src, opts) {
  // Load clip file without topology; later merge clipping data with target
  //   dataset and build topology.
  opts = utils.extend(opts, {no_topology: true});
  return api.importFile(src, opts);
};

MapShaper.convertClipBounds = function(bb) {
  var x0 = bb[0], y0 = bb[1], x1 = bb[2], y1 = bb[3],
      arc = [[x0, y0], [x0, y1], [x1, y1], [x1, y0], [x0, y0]];

  if (!(y1 > y0 && x1 > x0)) {
    stop("[clip/erase] Invalid bbox (should be [xmin, ymin, xmax, ymax]):", bb);
  }
  return {
    arcs: new ArcCollection([arc]),
    layers: [{
      shapes: [[[0]]],
      geometry_type: 'polygon'
    }]
  };
};




// Get function to Hash an x, y point to a non-negative integer
function getXYHash(size) {
  var buf = new ArrayBuffer(16),
      floats = new Float64Array(buf),
      uints = new Uint32Array(buf),
      lim = size | 0;
  if (lim > 0 === false) {
    throw new Error("Invalid size param: " + size);
  }

  return function(x, y) {
    var u = uints, h;
    floats[0] = x;
    floats[1] = y;
    h = u[0] ^ u[1];
    h = h << 5 ^ h >> 7 ^ u[2] ^ u[3];
    return (h & 0x7fffffff) % lim;
  };
}

// Get function to Hash a single coordinate to a non-negative integer
function getXHash(size) {
  var buf = new ArrayBuffer(8),
      floats = new Float64Array(buf),
      uints = new Uint32Array(buf),
      lim = size | 0;
  if (lim > 0 === false) {
    throw new Error("Invalid size param: " + size);
  }

  return function(x) {
    var h;
    floats[0] = x;
    h = uints[0] ^ uints[1];
    h = h << 5 ^ h >> 7;
    return (h & 0x7fffffff) % lim;
  };
}




// Used for building topology
//
function ArcIndex(pointCount) {
  var hashTableSize = Math.ceil(pointCount * 0.25),
      hash = getXYHash(hashTableSize),
      hashTable = new Int32Array(hashTableSize),
      chainIds = [],
      arcs = [],
      arcPoints = 0;

  utils.initializeArray(hashTable, -1);

  this.addArc = function(xx, yy) {
    var end = xx.length - 1,
        key = hash(xx[end], yy[end]),
        chainId = hashTable[key],
        arcId = arcs.length;
    hashTable[key] = arcId;
    arcs.push([xx, yy]);
    arcPoints += xx.length;
    chainIds.push(chainId);
    return arcId;
  };

  // Look for a previously generated arc with the same sequence of coords, but in the
  // opposite direction. (This program uses the convention of CW for space-enclosing rings, CCW for holes,
  // so coincident boundaries should contain the same points in reverse sequence).
  //
  this.findMatchingArc = function(xx, yy, start, end, getNext, getPrev) {
    // First, look for a reverse match
    var arcId = findArcNeighbor(xx, yy, start, end, getNext);
    if (arcId === null) {
      // Look for forward match
      // (Abnormal topology, but we're accepting it because in-the-wild
      // Shapefiles sometimes have duplicate paths)
      arcId = findArcNeighbor(xx, yy, end, start, getPrev);
    } else {
      arcId = ~arcId;
    }
    return arcId;
  };

  function findArcNeighbor(xx, yy, start, end, getNext) {
    var next = getNext(start),
        key = hash(xx[start], yy[start]),
        arcId = hashTable[key],
        arcX, arcY, len;

    while (arcId != -1) {
      // check endpoints and one segment...
      // it would be more rigorous but slower to identify a match
      // by comparing all segments in the coordinate sequence
      arcX = arcs[arcId][0];
      arcY = arcs[arcId][1];
      len = arcX.length;
      if (arcX[0] === xx[end] && arcX[len-1] === xx[start] && arcX[len-2] === xx[next] &&
          arcY[0] === yy[end] && arcY[len-1] === yy[start] && arcY[len-2] === yy[next]) {
        return arcId;
      }
      arcId = chainIds[arcId];
    }
    return null;
  }

  this.getVertexData = function() {
    var xx = new Float64Array(arcPoints),
        yy = new Float64Array(arcPoints),
        nn = new Uint32Array(arcs.length),
        copied = 0,
        arc, len;
    for (var i=0, n=arcs.length; i<n; i++) {
      arc = arcs[i];
      len = arc[0].length;
      MapShaper.copyElements(arc[0], 0, xx, copied, len);
      MapShaper.copyElements(arc[1], 0, yy, copied, len);
      nn[i] = len;
      copied += len;
    }
    return {
      xx: xx,
      yy: yy,
      nn: nn
    };
  };
}




function initHashChains(xx, yy) {
  // Performance doesn't improve much above ~1.3 * point count
  var n = xx.length,
      m = Math.floor(n * 1.3) || 1,
      hash = getXYHash(m),
      hashTable = new Int32Array(m),
      chainIds = new Int32Array(n), // Array to be filled with chain data
      key, j;

  for (var i=0; i<n; i++) {
    key = hash(xx[i], yy[i]);
    j = hashTable[key] - 1; // coord ids are 1-based in hash table; 0 used as null value.
    hashTable[key] = i + 1;
    chainIds[i] = j < 0 ? i : j; // first item in a chain points to self
  }
  return chainIds;
}

function initPointChains(xx, yy) {
  var chainIds = initHashChains(xx, yy),
      j, next, prevMatchId, prevUnmatchId;

  // disentangle, reverse and close the chains created by initHashChains()
  for (var i = xx.length-1; i>=0; i--) {
    next = chainIds[i];
    if (next >= i) continue;
    prevMatchId = i;
    prevUnmatchId = -1;
    do {
      j = next;
      next = chainIds[j];
      if (yy[j] == yy[i] && xx[j] == xx[i]) {
        chainIds[j] = prevMatchId;
        prevMatchId = j;
      } else {
        if (prevUnmatchId > -1) {
          chainIds[prevUnmatchId] = j;
        }
        prevUnmatchId = j;
      }
    } while (next < j);
    if (prevUnmatchId > -1) {
      // Make sure last unmatched entry is terminated
      chainIds[prevUnmatchId] = prevUnmatchId;
    }
    chainIds[i] = prevMatchId; // close the chain
  }
  return chainIds;
}




// Converts all polygon and polyline paths in a dataset to a topological format,
// (in-place);
api.buildTopology = function(dataset) {
  if (!dataset.arcs) return;
  var raw = dataset.arcs.getVertexData(),
      cooked = MapShaper.buildPathTopology(raw.nn, raw.xx, raw.yy);
  dataset.arcs.updateVertexData(cooked.nn, cooked.xx, cooked.yy);
  dataset.layers.forEach(function(lyr) {
    if (lyr.geometry_type == 'polyline' || lyr.geometry_type == 'polygon') {
      lyr.shapes = MapShaper.replaceArcIds(lyr.shapes, cooked.paths);
    }
  });
};

// buildPathTopology() converts non-topological paths into
// a topological format
//
// Arguments:
//    xx: [Array|Float64Array],   // x coords of each point in the dataset
//    yy: [Array|Float64Array],   // y coords ...
//    nn: [Array]  // length of each path
//
// (x- and y-coords of all paths are concatenated into two arrays)
//
// Returns:
// {
//    xx, yy (array)   // coordinate data
//    nn: (array)      // points in each arc
//    paths: (array)   // Paths are arrays of one or more arc id.
// }
//
// Negative arc ids in the paths array indicate a reversal of arc -(id + 1)
//
MapShaper.buildPathTopology = function(nn, xx, yy) {
  var pointCount = xx.length,
      chainIds = initPointChains(xx, yy),
      pathIds = initPathIds(pointCount, nn),
      index = new ArcIndex(pointCount),
      slice = usingTypedArrays() ? xx.subarray : Array.prototype.slice,
      paths, retn;
  paths = convertPaths(nn);
  retn = index.getVertexData();
  retn.paths = paths;
  return retn;

  function usingTypedArrays() {
    return !!(xx.subarray && yy.subarray);
  }

  function convertPaths(nn) {
    var paths = [],
        pointId = 0,
        pathLen;
    for (var i=0, len=nn.length; i<len; i++) {
      pathLen = nn[i];
      paths.push(pathLen < 2 ? null : convertPath(pointId, pointId + pathLen - 1));
      pointId += pathLen;
    }
    return paths;
  }

  function nextPoint(id) {
    var partId = pathIds[id],
        nextId = id + 1;
    if (nextId < pointCount && pathIds[nextId] === partId) {
      return id + 1;
    }
    var len = nn[partId];
    return sameXY(id, id - len + 1) ? id - len + 2 : -1;
  }

  function prevPoint(id) {
    var partId = pathIds[id],
        prevId = id - 1;
    if (prevId >= 0 && pathIds[prevId] === partId) {
      return id - 1;
    }
    var len = nn[partId];
    return sameXY(id, id + len - 1) ? id + len - 2 : -1;
  }

  function sameXY(a, b) {
    return xx[a] == xx[b] && yy[a] == yy[b];
  }

  // Convert a non-topological path to one or more topological arcs
  // @start, @end are ids of first and last points in the path
  // TODO: don't allow id ~id pairs
  //
  function convertPath(start, end) {
    var arcIds = [],
        firstNodeId = -1,
        arcStartId;

    // Visit each point in the path, up to but not including the last point
    for (var i = start; i < end; i++) {
      if (pointIsArcEndpoint(i)) {
        if (firstNodeId > -1) {
          arcIds.push(addEdge(arcStartId, i));
        } else {
          firstNodeId = i;
        }
        arcStartId = i;
      }
    }

    // Identify the final arc in the path
    if (firstNodeId == -1) {
      // Not in an arc, i.e. no nodes have been found...
      // Assuming that path is either an island or is congruent with one or more rings
      arcIds.push(addRing(start, end));
    }
    else if (firstNodeId == start) {
      // path endpoint is a node;
      if (!pointIsArcEndpoint(end)) {
        error("Topology error"); // TODO: better error handling
      }
      arcIds.push(addEdge(arcStartId, i));
    } else {
      // final arc wraps around
      arcIds.push(addSplitEdge(arcStartId, end, start + 1, firstNodeId));
    }
    return arcIds;
  }

  // Test if a point @id is an endpoint of a topological path
  function pointIsArcEndpoint(id) {
    var id2 = chainIds[id],
        prev = prevPoint(id),
        next = nextPoint(id),
        prev2, next2;
    if (prev == -1 || next == -1) {
      // @id is an endpoint if it is the start or end of an open path
      return true;
    }
    while (id != id2) {
      prev2 = prevPoint(id2);
      next2 = nextPoint(id2);
      if (prev2 == -1 || next2 == -1 || brokenEdge(prev, next, prev2, next2)) {
        // there is a discontinuity at @id -- point is arc endpoint
        return true;
      }
      id2 = chainIds[id2];
    }
    return false;
  }

  // a and b are two vertices with the same x, y coordinates
  // test if the segments on either side of them are also identical
  function brokenEdge(aprev, anext, bprev, bnext) {
    var apx = xx[aprev],
        anx = xx[anext],
        bpx = xx[bprev],
        bnx = xx[bnext],
        apy = yy[aprev],
        any = yy[anext],
        bpy = yy[bprev],
        bny = yy[bnext];
    if (apx == bnx && anx == bpx && apy == bny && any == bpy ||
        apx == bpx && anx == bnx && apy == bpy && any == bny) {
      return false;
    }
    return true;
  }

  function mergeArcParts(src, startId, endId, startId2, endId2) {
    var len = endId - startId + endId2 - startId2 + 2,
        ArrayClass = usingTypedArrays() ? Float64Array : Array,
        dest = new ArrayClass(len),
        j = 0, i;
    for (i=startId; i <= endId; i++) {
      dest[j++] = src[i];
    }
    for (i=startId2; i <= endId2; i++) {
      dest[j++] = src[i];
    }
    return dest;
  }

  function addSplitEdge(start1, end1, start2, end2) {
    var arcId = index.findMatchingArc(xx, yy, start1, end2, nextPoint, prevPoint);
    if (arcId === null) {
      arcId = index.addArc(mergeArcParts(xx, start1, end1, start2, end2),
          mergeArcParts(yy, start1, end1, start2, end2));
    }
    return arcId;
  }

  function addEdge(start, end) {
    // search for a matching edge that has already been generated
    var arcId = index.findMatchingArc(xx, yy, start, end, nextPoint, prevPoint);
    if (arcId === null) {
      arcId = index.addArc(slice.call(xx, start, end + 1),
          slice.call(yy, start, end + 1));
    }
    return arcId;
  }

  function addRing(startId, endId) {
    var chainId = chainIds[startId],
        pathId = pathIds[startId],
        arcId;

    while (chainId != startId) {
      if (pathIds[chainId] < pathId) {
        break;
      }
      chainId = chainIds[chainId];
    }

    if (chainId == startId) {
      return addEdge(startId, endId);
    }

    for (var i=startId; i<endId; i++) {
      arcId = index.findMatchingArc(xx, yy, i, i, nextPoint, prevPoint);
      if (arcId !== null) return arcId;
    }
    error("Unmatched ring; id:", pathId, "len:", nn[pathId]);
  }
};


// Create a lookup table for path ids; path ids are indexed by point id
//
function initPathIds(size, pathSizes) {
  var pathIds = new Int32Array(size),
      j = 0;
  for (var pathId=0, pathCount=pathSizes.length; pathId < pathCount; pathId++) {
    for (var i=0, n=pathSizes[pathId]; i<n; i++, j++) {
      pathIds[j] = pathId;
    }
  }
  return pathIds;
}

MapShaper.replaceArcIds = function(src, replacements) {
  return src.map(function(shape) {
    return replaceArcsInShape(shape, replacements);
  });

  function replaceArcsInShape(shape, replacements) {
    if (!shape) return null;
    return shape.map(function(path) {
      return replaceArcsInPath(path, replacements);
    });
  }

  function replaceArcsInPath(path, replacements) {
    return path.reduce(function(memo, id) {
      var abs = absArcId(id);
      var topoPath = replacements[abs];
      if (topoPath) {
        if (id < 0) {
          topoPath = topoPath.concat(); // TODO: need to copy?
          MapShaper.reversePath(topoPath);
        }
        for (var i=0, n=topoPath.length; i<n; i++) {
          memo.push(topoPath[i]);
        }
      }
      return memo;
    }, []);
  }
};




MapShaper.getHighPrecisionSnapInterval = function(arcs) {
  var bb = arcs.getBounds();
  if (!bb.hasBounds()) return 0;
  var maxCoord = Math.max(Math.abs(bb.xmin), Math.abs(bb.ymin),
      Math.abs(bb.xmax), Math.abs(bb.ymax));
  return maxCoord * 1e-14;
};

MapShaper.snapCoords = function(arcs, threshold) {
    var avgDist = arcs.getAvgSegment(),
        autoSnapDist = avgDist * 0.0025,
        snapDist = autoSnapDist;

  if (threshold > 0) {
    snapDist = threshold;
    message(utils.format("Applying snapping threshold of %s -- %.6f times avg. segment length", threshold, threshold / avgDist));
  }

  var snapCount = MapShaper.snapCoordsByInterval(arcs, snapDist);
  if (snapCount > 0) arcs.dedupCoords();
  message(utils.format("Snapped %s point%s", snapCount, utils.pluralSuffix(snapCount)));
};

// Snap together points within a small threshold
//
MapShaper.snapCoordsByInterval = function(arcs, snapDist) {
  var snapCount = 0,
      data = arcs.getVertexData();

  // Get sorted coordinate ids
  // Consider: speed up sorting -- try bucket sort as first pass.
  //
  var ids = utils.sortCoordinateIds(data.xx);
  for (var i=0, n=ids.length; i<n; i++) {
    snapCount += snapPoint(i, snapDist, ids, data.xx, data.yy);
  }
  return snapCount;

  function snapPoint(i, limit, ids, xx, yy) {
    var j = i,
        n = ids.length,
        x = xx[ids[i]],
        y = yy[ids[i]],
        snaps = 0,
        id2, dx, dy;

    while (++j < n) {
      id2 = ids[j];
      dx = xx[id2] - x;
      if (dx > limit) break;
      dy = yy[id2] - y;
      if (dx === 0 && dy === 0 || dx * dx + dy * dy > limit * limit) continue;
      xx[id2] = x;
      yy[id2] = y;
      snaps++;
    }
    return snaps;
  }
};

utils.sortCoordinateIds = function(a) {
  var n = a.length,
      ids = new Uint32Array(n);
  for (var i=0; i<n; i++) {
    ids[i] = i;
  }
  utils.quicksortIds(a, ids, 0, ids.length-1);
  return ids;
};

/*
// Returns array of array ids, in ascending order.
// @a array of numbers
//
utils.sortCoordinateIds = function(a) {
  return utils.bucketSortIds(a);
};

// This speeds up sorting of large datasets (~2x faster for 1e7 values)
// worth the additional code?
utils.bucketSortIds = function(a, n) {
  var len = a.length,
      ids = new Uint32Array(len),
      bounds = utils.getArrayBounds(a),
      buckets = Math.ceil(n > 0 ? n : len / 10),
      counts = new Uint32Array(buckets),
      offsets = new Uint32Array(buckets),
      i, j, offs, count;

  // get bucket sizes
  for (i=0; i<len; i++) {
    j = bucketId(a[i], bounds.min, bounds.max, buckets);
    counts[j]++;
  }

  // convert counts to offsets
  offs = 0;
  for (i=0; i<buckets; i++) {
    offsets[i] = offs;
    offs += counts[i];
  }

  // assign ids to buckets
  for (i=0; i<len; i++) {
    j = bucketId(a[i], bounds.min, bounds.max, buckets);
    offs = offsets[j]++;
    ids[offs] = i;
  }

  // sort each bucket with quicksort
  for (i = 0; i<buckets; i++) {
    count = counts[i];
    if (count > 1) {
      offs = offsets[i] - count;
      utils.quicksortIds(a, ids, offs, offs + count - 1);
    }
  }
  return ids;

  function bucketId(val, min, max, buckets) {
    var id = (buckets * (val - min) / (max - min)) | 0;
    return id < buckets ? id : buckets - 1;
  }
};
*/

utils.quicksortIds = function (a, ids, lo, hi) {
  if (hi - lo > 24) {
    var pivot = a[ids[lo + hi >> 1]],
        i = lo,
        j = hi,
        tmp;
    while (i <= j) {
      while (a[ids[i]] < pivot) i++;
      while (a[ids[j]] > pivot) j--;
      if (i <= j) {
        tmp = ids[i];
        ids[i] = ids[j];
        ids[j] = tmp;
        i++;
        j--;
      }
    }
    if (j > lo) utils.quicksortIds(a, ids, lo, j);
    if (i < hi) utils.quicksortIds(a, ids, i, hi);
  } else {
    utils.insertionSortIds(a, ids, lo, hi);
  }
};

utils.insertionSortIds = function(arr, ids, start, end) {
  var id, i, j;
  for (j = start + 1; j <= end; j++) {
    id = ids[j];
    for (i = j - 1; i >= start && arr[id] < arr[ids[i]]; i--) {
      ids[i+1] = ids[i];
    }
    ids[i+1] = id;
  }
};




// Import path data from a non-topological source (Shapefile, GeoJSON, etc)
// in preparation for identifying topology.
// @reservedPoints (optional) estimate of points in dataset, for allocating buffers
//
function PathImporter(opts, reservedPoints) {
  opts = opts || {};

  var bufSize = reservedPoints > 0 ? reservedPoints : 20000,
      xx = new Float64Array(bufSize),
      yy = new Float64Array(bufSize),
      buf = new Float64Array(1024),
      shapes = [],
      nn = [],
      collectionType = null,
      round = null,
      pathId = -1,
      shapeId = -1,
      pointId = 0,
      dupeCount = 0,
      skippedPathCount = 0;

  if (opts.precision) {
    round = getRoundingFunction(opts.precision);
  }

  function addShapeType(t) {
    if (!collectionType) {
      collectionType = t;
    } else if (t != collectionType) {
      collectionType = "mixed";
    }
  }

  function checkBuffers(needed) {
    if (needed > xx.length) {
      var newLen = Math.max(needed, Math.ceil(xx.length * 1.5));
      xx = MapShaper.extendBuffer(xx, newLen, pointId);
      yy = MapShaper.extendBuffer(yy, newLen, pointId);
    }
  }

  function getPointBuf(n) {
    var len = n * 2;
    if (buf.length < len) {
      buf = new Float64Array(Math.ceil(len * 1.3));
    }
    return buf;
  }

  this.startShape = function() {
    shapes[++shapeId] = null;
  };

  function appendToShape(part) {
    var currShape = shapes[shapeId] || (shapes[shapeId] = []);
    currShape.push(part);
  }

  function appendPath(n, type) {
    addShapeType(type);
    pathId++;
    nn[pathId] = n;
    appendToShape([pathId]);
  }

  function roundPoints(points, round) {
    points.forEach(function(p) {
      p[0] = round(p[0]);
      p[1] = round(p[1]);
    });
  }

  // Import coordinates from an array with coordinates in format: [x, y, x, y, ...]
  //
  this.importPathFromFlatArray = function(arr, type, len, start) {
    var i = start || 0,
        end = i + len,
        n = 0,
        x, y, prevX, prevY;

    checkBuffers(pointId + len);
    while (i < end) {
      x = arr[i++];
      y = arr[i++];
      if (round) {
        x = round(x);
        y = round(y);
      }
      if (i > 0 && x == prevX && y == prevY) {
        dupeCount++;
      } else {
        xx[pointId] = x;
        yy[pointId] = y;
        pointId++;
        n++;
      }
      prevY = y;
      prevX = x;
    }

    appendPath(n, type);

  };

  // Import an array of [x, y] Points
  //
  this.importPath = function(points, type) {
    var n = points.length,
        buf = getPointBuf(n),
        j = 0;
    for (var i=0; i < n; i++) {
      buf[j++] = points[i][0];
      buf[j++] = points[i][1];
    }
    this.importPathFromFlatArray(buf, type, j, 0);
  };

  this.importPoints = function(points) {
    addShapeType('point');
    if (round) {
      roundPoints(points, round);
    }
    points.forEach(appendToShape);
  };

  this.importLine = function(points) {
    this.importPath(points, 'polyline');
  };

  this.importPolygon = function(points, isHole) {
    var area = geom.getPlanarPathArea2(points);

    if (isHole === true && area > 0 || isHole === false && area < 0) {
      verbose("Warning: reversing", isHole ? "a CW hole" : "a CCW ring");
      points.reverse();
    }
    this.importPath(points, 'polygon');
  };

  // Return topological shape data
  // Apply any requested snapping and rounding
  // Remove duplicate points, check for ring inversions
  //
  this.done = function() {
    var arcs;

    // possible values: polygon, polyline, point, mixed, null
    if (collectionType == 'mixed') {
      stop("[PathImporter] Mixed feature types are not allowed");
    } else if (collectionType == 'polygon' || collectionType == 'polyline') {

      if (dupeCount > 0) {
        verbose(utils.format("Removed %,d duplicate point%s", dupeCount, utils.pluralSuffix(dupeCount)));
      }
      if (skippedPathCount > 0) {
        // TODO: consider showing details about type of error
        message(utils.format("Removed %,d path%s with defective geometry", skippedPathCount, utils.pluralSuffix(skippedPathCount)));
      }

      if (pointId > 0) {
        if (pointId < xx.length) {
          xx = xx.subarray(0, pointId);
          yy = yy.subarray(0, pointId);
        }
        arcs = new ArcCollection(nn, xx, yy);

        // TODO: move shape validation after snapping (which may corrupt shapes)
        if (opts.auto_snap || opts.snap_interval) {
          T.start();
          MapShaper.snapCoords(arcs, opts.snap_interval);
          T.stop("Snapping points");
        }
        MapShaper.cleanShapes(shapes, arcs, collectionType);
      } else {
        message("No geometries were imported");
        collectionType = null;
      }
    } else if (collectionType == 'point' || collectionType === null) {
      // pass
    } else {
      error("Unexpected collection type:", collectionType);
    }

    // TODO: remove empty arcs, collapsed arcs
    // ...

    return {
      arcs: arcs || null,
      info: {},
      layers: [{
        name: '',
        geometry_type: collectionType,
        shapes: shapes
      }]
    };
  };
}




MapShaper.exportPointData = function(points) {
  var data, path;
  if (!points || points.length === 0) {
    data = {partCount: 0, pointCount: 0};
  } else {
    path = {
      points: points,
      pointCount: points.length,
      bounds: geom.getPathBounds(points)
    };
    data = {
      bounds: path.bounds,
      pathData: [path],
      partCount: 1,
      pointCount: path.pointCount
    };
  }
  return data;
};

// TODO: remove duplication with MapShaper.getPathMetadata()
MapShaper.exportPathData = function(shape, arcs, type) {
  // kludge until Shapefile exporting is refactored
  if (type == 'point') return MapShaper.exportPointData(shape);

  var pointCount = 0,
      bounds = new Bounds(),
      paths = [];

  if (shape && (type == 'polyline' || type == 'polygon')) {
    shape.forEach(function(arcIds, i) {
      var iter = arcs.getShapeIter(arcIds),
          path = MapShaper.exportPathCoords(iter),
          valid = true;
      if (type == 'polygon') {
        path.area = geom.getPlanarPathArea2(path.points);
        valid = path.pointCount > 3 && path.area !== 0;
      } else if (type == 'polyline') {
        valid = path.pointCount > 1;
      }
      if (valid) {
        pointCount += path.pointCount;
        path.bounds = geom.getPathBounds(path.points);
        bounds.mergeBounds(path.bounds);
        paths.push(path);
      } else {
        verbose("Skipping a collapsed", type, "path");
      }
    });
  }

  return {
    pointCount: pointCount,
    pathData: paths,
    pathCount: paths.length,
    bounds: bounds
  };
};

MapShaper.exportPathCoords = function(iter) {
  var points = [],
      i = 0,
      x, y, prevX, prevY;
  while (iter.hasNext()) {
    x = iter.x;
    y = iter.y;
    if (i === 0 || prevX != x || prevY != y) {
      points.push([x, y]);
      i++;
    }
    prevX = x;
    prevY = y;
  }
  return {
    points: points,
    pointCount: points.length
  };
};




MapShaper.getFormattedStringify = function(numArrayKeys) {
  var keyIndex = utils.arrayToIndex(numArrayKeys);
  var quoteStr = '\u1000\u2FD5\u0310'; // TODO: avoid using a string that might be present in the content
  var stripRxp = new RegExp('"' + quoteStr + '|' + quoteStr + '"', 'g');
  var indentChars = '\t';

  function replace(key, val) {
    // pre-format coordinate arrays
    if (key in keyIndex && utils.isArray(val)) {
      var str = JSON.stringify(val);
      // skip arrays containing strings (problem with double-quote escaping)
      if (str.indexOf('"' == -1)) {
        return quoteStr + str.replace(/,/g, ', ') + quoteStr;
      }
    }
    return val;
  }

  return function(obj) {
    var json = JSON.stringify(obj, replace, indentChars);
    return json.replace(stripRxp, '');
  };
};




var GeoJSON = MapShaper.geojson = {};
GeoJSON.ID_FIELD = "FID"; // default field name of imported *JSON feature ids

MapShaper.importGeoJSON = function(src, opts) {
  var srcObj = utils.isString(src) ? JSON.parse(src) : src,
      supportedGeometries = Object.keys(GeoJSON.pathImporters),
      idField = opts.id_field || GeoJSON.ID_FIELD,
      properties = null,
      geometries, srcCollection, importer, dataset;

  // Convert single feature or geometry into a collection with one member
  if (srcObj.type == 'Feature') {
    srcCollection = {
      type: 'FeatureCollection',
      features: [srcObj]
    };
  } else if (utils.contains(supportedGeometries, srcObj.type)) {
    srcCollection = {
      type: 'GeometryCollection',
      geometries: [srcObj]
    };
  } else {
    srcCollection = srcObj;
  }

  if (srcCollection.type == 'FeatureCollection') {
    properties = [];
    geometries = srcCollection.features.map(function(feat) {
      var rec = feat.properties || {};
      if ('id' in feat) {
        rec[idField] = feat.id;
      }
      properties.push(rec);
      return feat.geometry;
    });
  } else if (srcCollection.type == 'GeometryCollection') {
    geometries = srcCollection.geometries;
  } else {
    stop("[i] Unsupported GeoJSON type:", srcCollection.type);
  }

  if (!geometries) {
    stop("[i] Missing geometry data");
  }

  // Import GeoJSON geometries
  importer = new PathImporter(opts);
  geometries.forEach(function(geom) {
    importer.startShape();
    if (geom) {
      GeoJSON.importGeometry(geom, importer);
    }
  });
  dataset = importer.done();

  if (properties) {
    dataset.layers[0].data = new DataTable(properties);
  }
  MapShaper.importCRS(dataset, srcObj);

  return dataset;
};

GeoJSON.translateGeoJSONType = function(type) {
  return GeoJSON.typeLookup[type] || null;
};

GeoJSON.typeLookup = {
  LineString: 'polyline',
  MultiLineString: 'polyline',
  Polygon: 'polygon',
  MultiPolygon: 'polygon',
  Point: 'point',
  MultiPoint: 'point'
};

GeoJSON.importGeometry = function(geom, importer) {
  var type = geom.type;
  if (type in GeoJSON.pathImporters) {
    GeoJSON.pathImporters[type](geom.coordinates, importer);
  } else if (type == 'GeometryCollection') {
    geom.geometries.forEach(function(geom) {
      GeoJSON.importGeometry(geom, importer);
    });
  } else {
    verbose("TopoJSON.importGeometryCollection() Unsupported geometry type:", geom.type);
  }
};

// Functions for importing geometry coordinates using a PathImporter
//
GeoJSON.pathImporters = {
  LineString: function(coords, importer) {
    importer.importLine(coords);
  },
  MultiLineString: function(coords, importer) {
    for (var i=0; i<coords.length; i++) {
      GeoJSON.pathImporters.LineString(coords[i], importer);
    }
  },
  Polygon: function(coords, importer) {
    for (var i=0; i<coords.length; i++) {
      importer.importPolygon(coords[i], i > 0);
    }
  },
  MultiPolygon: function(coords, importer) {
    for (var i=0; i<coords.length; i++) {
      GeoJSON.pathImporters.Polygon(coords[i], importer);
    }
  },
  Point: function(coord, importer) {
    importer.importPoints([coord]);
  },
  MultiPoint: function(coords, importer) {
    importer.importPoints(coords);
  }
};

MapShaper.exportGeoJSON = function(dataset, opts) {
  var extension = "json";
  if (opts.output_file) {
    // override default output extension if output filename is given
    extension = utils.getFileExtension(opts.output_file);
  }
  return dataset.layers.map(function(lyr) {
    return {
      content: MapShaper.exportGeoJSONString(lyr, dataset, opts),
      filename: lyr.name ? lyr.name + '.' + extension : ""
    };
  });
};

// @opt value of id-field option (empty, string or array of strings)
// @fields array
MapShaper.getIdField = function(fields, opt) {
  var ids = [];
  if (utils.isString(opt)) {
    ids.push(opt);
  } else if (utils.isArray(opt)) {
    ids = opt;
  }
  ids.push(GeoJSON.ID_FIELD); // default id field
  return utils.find(ids, function(name) {
    return utils.contains(fields, name);
  });
};

MapShaper.exportProperties = function(table, opts) {
  var fields = table ? table.getFields() : [],
      idField = MapShaper.getIdField(fields, opts.id_field),
      deleteId = idField == GeoJSON.ID_FIELD, // delete default field, not user-set fields
      properties, records;
  if (opts.drop_table || opts.cut_table || fields.length === 0 || deleteId && fields.length == 1) {
    return null;
  }
  records = table.getRecords();
  if (deleteId) {
    properties = records.map(function(rec) {
      rec = utils.extend({}, rec); // copy rec;
      delete rec[idField];
      return rec;
    });
  } else {
    properties = records;
  }
  return properties;
};

MapShaper.exportIds = function(table, opts) {
  var fields = table ? table.getFields() : [],
      idField = MapShaper.getIdField(fields, opts.id_field);
  if (!idField) return null;
  return table.getRecords().map(function(rec) {
    return idField in rec ? rec[idField] : null;
  });
};

MapShaper.importCRS = function(dataset, jsonObj) {
  if ('crs' in jsonObj) {
    dataset.info.input_crs = jsonObj.crs;
  }
};

// @jsonObj is a top-level GeoJSON or TopoJSON object
MapShaper.exportCRS = function(dataset, jsonObj) {
  var info = dataset.info || {};
  if ('output_crs' in info) {
    jsonObj.crs = info.output_crs;
  } else if ('input_crs' in info) {
    jsonObj.crs = info.input_crs;
  }
};

MapShaper.exportGeoJSONString = function(lyr, dataset, opts) {
  opts = opts || {};
  var properties = MapShaper.exportProperties(lyr.data, opts),
      arcs = dataset.arcs,
      ids = MapShaper.exportIds(lyr.data, opts),
      useFeatures = !!(properties || ids),
      stringify = JSON.stringify;

  if (opts.prettify) {
    stringify = MapShaper.getFormattedStringify(['bbox', 'coordinates']);
  }
  if (properties && properties.length !== lyr.shapes.length) {
    error("[-o] Mismatch between number of properties and number of shapes");
  }

  var output = {
    type: useFeatures ? 'FeatureCollection' : 'GeometryCollection'
  };

  MapShaper.exportCRS(dataset, output);

  if (opts.bbox) {
    var bounds = MapShaper.getLayerBounds(lyr, arcs);
    if (bounds.hasBounds()) {
      output.bbox = bounds.toArray();
    }
  }

  output[useFeatures ? 'features' : 'geometries'] = ['$'];

  // serialize features one at a time to avoid allocating lots of arrays
  // TODO: consider serializing once at the end, for clarity
  var objects = lyr.shapes.reduce(function(memo, shape, i) {
    var obj = MapShaper.exportGeoJSONGeometry(shape, arcs, lyr.geometry_type),
        str;
    if (useFeatures) {
      obj = {
        type: "Feature",
        properties: properties && properties[i] || null,
        geometry: obj
      };
    } else if (obj === null) {
      return memo; // null geometries not allowed in GeometryCollection, skip them
    }
    if (ids) {
      obj.id = ids[i];
    }
    str = stringify(obj);
    return memo === "" ? str : memo + (",\n" + str);
  }, "");

  return stringify(output).replace(/[\t ]*"\$"[\t ]*/, objects);
};

MapShaper.exportGeoJSONObject = function(lyr, arcs, opts) {
  return JSON.parse(MapShaper.exportGeoJSONString(lyr, arcs, opts));
};

// export GeoJSON or TopoJSON point geometry
GeoJSON.exportPointGeom = function(points, arcs) {
  var geom = null;
  if (points.length == 1) {
    geom = {
      type: "Point",
      coordinates: points[0]
    };
  } else if (points.length > 1) {
    geom = {
      type: "MultiPoint",
      coordinates: points
    };
  }
  return geom;
};

GeoJSON.exportLineGeom = function(ids, arcs) {
  var obj = MapShaper.exportPathData(ids, arcs, "polyline");
  if (obj.pointCount === 0) return null;
  var coords = obj.pathData.map(function(path) {
    return path.points;
  });
  return coords.length == 1 ? {
    type: "LineString",
    coordinates: coords[0]
  } : {
    type: "MultiLineString",
    coordinates: coords
  };
};

GeoJSON.exportPolygonGeom = function(ids, arcs) {
  var obj = MapShaper.exportPathData(ids, arcs, "polygon");
  if (obj.pointCount === 0) return null;
  var groups = MapShaper.groupPolygonRings(obj.pathData);
  var coords = groups.map(function(paths) {
    return paths.map(function(path) {
      return path.points;
    });
  });
  return coords.length == 1 ? {
    type: "Polygon",
    coordinates: coords[0]
  } : {
    type: "MultiPolygon",
    coordinates: coords
  };
};

MapShaper.exportGeoJSONGeometry = function(shape, arcs, type) {
  return shape ? GeoJSON.exporters[type](shape, arcs) : null;
};

GeoJSON.exporters = {
  polygon: GeoJSON.exportPolygonGeom,
  polyline: GeoJSON.exportLineGeom,
  point: GeoJSON.exportPointGeom
};



var TopoJSON = {};

// Iterate over all arrays of arc is in a geometry object
// @cb callback: function(ids)
// callback returns undefined or an array of replacement ids
//
TopoJSON.forEachPath = function forEachPath(obj, cb) {
  var iterators = {
        GeometryCollection: function(o) {o.geometries.forEach(eachGeom);},
        LineString: function(o) {
          var retn = cb(o.arcs);
          if (retn) o.arcs = retn;
        },
        MultiLineString: function(o) {eachMultiPath(o.arcs);},
        Polygon: function(o) {eachMultiPath(o.arcs);},
        MultiPolygon: function(o) {o.arcs.forEach(eachMultiPath);}
      };

  eachGeom(obj);

  function eachGeom(o) {
    if (o.type in iterators) {
      iterators[o.type](o);
    }
  }

  function eachMultiPath(arr) {
    var retn;
    for (var i=0; i<arr.length; i++) {
      retn = cb(arr[i]);
      if (retn) arr[i] = retn;
    }
  }
};

TopoJSON.forEachArc = function forEachArc(obj, cb) {
  TopoJSON.forEachPath(obj, function(ids) {
    var retn;
    for (var i=0; i<ids.length; i++) {
      retn = cb(ids[i]);
      if (utils.isInteger(retn)) {
        ids[i] = retn;
      }
    }
  });
};




TopoJSON.decodeArcs = function(arcs, transform) {
  var mx = transform.scale[0],
      my = transform.scale[1],
      bx = transform.translate[0],
      by = transform.translate[1];

  arcs.forEach(function(arc) {
    var prevX = 0,
        prevY = 0,
        xy, x, y;
    for (var i=0, len=arc.length; i<len; i++) {
      xy = arc[i];
      x = xy[0] + prevX;
      y = xy[1] + prevY;
      xy[0] = x * mx + bx;
      xy[1] = y * my + by;
      prevX = x;
      prevY = y;
    }
  });
};

// TODO: consider removing dupes...
TopoJSON.roundCoords = function(arcs, precision) {
  var round = getRoundingFunction(precision),
      p;
  arcs.forEach(function(arc) {
    for (var i=0, len=arc.length; i<len; i++) {
      p = arc[i];
      p[0] = round(p[0]);
      p[1] = round(p[1]);
    }
  });
};

TopoJSON.importObject = function(obj, opts) {
  if (obj.type != 'GeometryCollection') {
    obj = {
      type: "GeometryCollection",
      geometries: [obj]
    };
  }
  return TopoJSON.importGeometryCollection(obj, opts);
};

TopoJSON.importGeometryCollection = function(obj, opts) {
  var importer = new TopoJSON.GeometryImporter(opts);
  obj.geometries.forEach(importer.addGeometry, importer);
  return importer.done();
};

//
//
TopoJSON.GeometryImporter = function(opts) {
  var idField = opts && opts.id_field || GeoJSON.ID_FIELD,
      properties = [],
      shapes = [], // topological ids
      collectionType = null;

  this.addGeometry = function(geom) {
    var type = GeoJSON.translateGeoJSONType(geom.type),
        shapeId = shapes.length,
        rec = geom.properties,
        shape = null;

    if ('id' in geom) {
      rec = rec || {};
      rec[idField] = geom.id;
    }
    if (rec) {
      properties[shapeId] = rec;
    }
    if (type == 'point') {
      shape = this.importPointGeometry(geom);
    } else if (geom.type in TopoJSON.pathImporters) {
      shape = TopoJSON.pathImporters[geom.type](geom.arcs);
    } else {
      if (geom.type) {
        verbose("[TopoJSON] Unknown geometry type:", geom.type);
      }
      // null geometry -- ok
    }
    shapes.push(shape);
    this.updateCollectionType(type);
  };

  this.importPointGeometry = function(geom) {
    var shape = null;
    if (geom.type == 'Point') {
      shape = [geom.coordinates];
    } else if (geom.type == 'MultiPoint') {
      shape = geom.coordinates;
    } else {
      stop("Invalid TopoJSON point geometry:", geom);
    }
    return shape;
  };

  this.updateCollectionType = function(type) {
    if (!collectionType) {
      collectionType = type;
    } else if (type && collectionType != type) {
      collectionType = 'mixed';
    }
  };

  this.done = function() {
    var lyr = {
      shapes: shapes,
      geometry_type: collectionType
    };
    if (properties.length > 0) {
      lyr.data = new DataTable(properties);
    }
    // console.log(lyr.shapes)
    return lyr;
  };
};

TopoJSON.pathImporters = {
  LineString: function(arcs) {
    return [arcs];
  },
  MultiLineString: function(arcs) {
    return arcs;
  },
  Polygon: function(arcs) {
    return arcs;
  },
  MultiPolygon: function(arcs) {
    return arcs.reduce(function(memo, arr) {
      return memo ? memo.concat(arr) : arr;
    }, null);
  }
};




api.explodeFeatures = function(lyr, arcs, opts) {
  var properties = lyr.data ? lyr.data.getRecords() : null,
      explodedProperties = properties ? [] : null,
      explodedShapes = [],
      explodedLyr = utils.extend({}, lyr);

  lyr.shapes.forEach(function(shp, shpId) {
    var exploded;
    if (!shp) {
      explodedShapes.push(null);
    } else {
      if (lyr.geometry_type == 'polygon' && shp.length > 1) {
        exploded = MapShaper.explodePolygon(shp, arcs);
      } else {
        exploded = MapShaper.explodeShape(shp);
      }
      utils.merge(explodedShapes, exploded);
    }

    explodedLyr.shapes = explodedShapes;
    if (explodedProperties) {
      for (var i=0, n=exploded ? exploded.length : 1; i<n; i++) {
        explodedProperties.push(MapShaper.cloneProperties(properties[shpId]));
      }
    }
  });

  explodedLyr.shapes = explodedShapes;
  if (explodedProperties) {
    explodedLyr.data = new DataTable(explodedProperties);
  }
  return explodedLyr;
};

MapShaper.explodeShape = function(shp) {
  return shp.map(function(part) {
    return [part.concat()];
  });
};

MapShaper.explodePolygon = function(shape, arcs) {
  var paths = MapShaper.getPathMetadata(shape, arcs, "polygon");
  var groups = MapShaper.groupPolygonRings(paths);
  return groups.map(function(shape) {
    return shape.map(function(path) {
      return path.ids;
    });
  });
};

MapShaper.cloneProperties = function(obj) {
  var clone = {};
  for (var key in obj) {
    clone[key] = obj[key];
  }
  return clone;
};




TopoJSON.getPresimplifyFunction = function(width) {
  var quanta = 10000,  // enough resolution for pixel-level detail at 1000px width and 10x zoom
      k = quanta / width;
  return function(z) {
    // could substitute a rounding function with decimal precision
    return z === Infinity ? 0 : Math.ceil(z * k);
  };
};




// Convert a dataset object to a TopoJSON topology object
TopoJSON.exportTopology = function(src, opts) {
  var dataset = TopoJSON.copyDatasetForExport(src),
      arcs = dataset.arcs,
      topology = {type: "Topology"},
      bounds;

  // generate arcs and transform
  if (MapShaper.datasetHasPaths(dataset)) {
    bounds = MapShaper.getDatasetBounds(dataset);
    if (opts.bbox && bounds.hasBounds()) {
      topology.bbox = bounds.toArray();
    }
    if (!opts.no_quantization) {
      topology.transform = TopoJSON.transformDataset(dataset, bounds, opts);
    }
    MapShaper.dissolveArcs(dataset); // dissolve/prune arcs for more compact output
    topology.arcs = TopoJSON.exportArcs(arcs, bounds, opts);
    if (topology.transform) {
      TopoJSON.deltaEncodeArcs(topology.arcs);
    }
  } else {
    // some datasets may lack arcs; spec seems to require an array anyway
    topology.arcs = [];
  }

  // export layers as TopoJSON named objects
  topology.objects = dataset.layers.reduce(function(objects, lyr, i) {
    var name = lyr.name || "layer" + (i + 1);
    objects[name] = TopoJSON.exportLayer(lyr, arcs, opts);
    return objects;
  }, {});

  // retain crs data if relevant
  MapShaper.exportCRS(dataset, topology);
  return topology;
};

// Clone arc data (this gets modified in place during TopoJSON export)
// Shallow-copy shape data in each layer (gets replaced with remapped shapes)
TopoJSON.copyDatasetForExport = function(dataset) {
  var copy = {info: dataset.info};
  copy.layers = dataset.layers.map(function(lyr) {
    var shapes = lyr.shapes ? lyr.shapes.concat() : null;
    return utils.defaults({shapes: shapes}, lyr);
  });
  if (dataset.arcs) {
    copy.arcs = dataset.arcs.getFilteredCopy();
  }
  return copy;
};

TopoJSON.transformDataset = function(dataset, bounds, opts) {
  var bounds2 = TopoJSON.calcExportBounds(bounds, dataset.arcs, opts),
      transform = bounds.getTransform(bounds2),
      inv = transform.invert();
  dataset.arcs.applyTransform(transform, true); // flag -> round coords
  // TODO: think about handling geometrical errors introduced by quantization,
  // e.g. segment intersections and collapsed polygon rings.
  return {
    scale: [inv.mx, inv.my],
    translate: [inv.bx, inv.by]
  };
};

// Export arcs as arrays of [x, y] and possibly [z] coordinates
TopoJSON.exportArcs = function(arcs, bounds, opts) {
  var fromZ = null,
      output = [];
  if (opts.presimplify) {
    // Calculate simplification thresholds if none exist
    if (!arcs.getVertexData().zz) {
      MapShaper.simplifyPaths(arcs, opts);
    }
    fromZ = TopoJSON.getPresimplifyFunction(bounds.width());
  }
  arcs.forEach2(function(i, n, xx, yy, zz) {
    var arc = [], p;
    for (var j=i + n; i<j; i++) {
      p = [xx[i], yy[i]];
      if (fromZ) {
        p.push(fromZ(zz[i]));
      }
      arc.push(p);
    }
    output.push(arc.length > 1 ? arc : null);
  });
  return output;
};

// Apply delta encoding in-place to an array of topojson arcs
TopoJSON.deltaEncodeArcs = function(arcs) {
  arcs.forEach(function(arr) {
    var ax, ay, bx, by, p;
    for (var i=0, n=arr.length; i<n; i++) {
      p = arr[i];
      bx = p[0];
      by = p[1];
      if (i > 0) {
        p[0] = bx - ax;
        p[1] = by - ay;
      }
      ax = bx;
      ay = by;
    }
  });
};

// Calculate the x, y extents that map to an integer unit in topojson output
// as a fraction of the x- and y- extents of the average segment.
TopoJSON.calcExportResolution = function(arcs, k) {
  // TODO: think about the effect of long lines, e.g. from polar cuts.
  var xy = arcs.getAvgSegment2();
  return [xy[0] * k, xy[1] * k];
};

// Calculate the bounding box of quantized topojson coordinates using one
// of several methods.
TopoJSON.calcExportBounds = function(bounds, arcs, opts) {
  var unitXY, xmax, ymax;
  if (opts.topojson_precision > 0) {
    unitXY = TopoJSON.calcExportResolution(arcs, opts.topojson_precision);
  } else if (opts.quantization > 0) {
    unitXY = [bounds.width() / (opts.quantization-1), bounds.height() / (opts.quantization-1)];
  } else if (opts.precision > 0) {
    unitXY = [opts.precision, opts.precision];
  } else {
    // default -- auto quantization at 0.02 of avg. segment len
    unitXY = TopoJSON.calcExportResolution(arcs, 0.02);
  }
  xmax = Math.ceil(bounds.width() / unitXY[0]);
  ymax = Math.ceil(bounds.height() / unitXY[1]);
  return new Bounds(0, 0, xmax, ymax);
};

TopoJSON.exportProperties = function(geometries, table, opts) {
  var properties = MapShaper.exportProperties(table, opts),
      ids = MapShaper.exportIds(table, opts);
  geometries.forEach(function(geom, i) {
    if (properties) {
      geom.properties = properties[i];
    }
    if (ids) {
      geom.id = ids[i];
    }
  });
};

// Export a mapshaper layer as a GeometryCollection
TopoJSON.exportLayer = function(lyr, arcs, opts) {
  var n = MapShaper.getFeatureCount(lyr),
      geometries = [];
  // initialize to null geometries
  for (var i=0; i<n; i++) {
    geometries[i] = {type: null};
  }
  if (MapShaper.layerHasGeometry(lyr)) {
    TopoJSON.exportGeometries(geometries, lyr.shapes, arcs, lyr.geometry_type);
  }
  if (lyr.data) {
    TopoJSON.exportProperties(geometries, lyr.data, opts);
  }
  return {
    type: "GeometryCollection",
    geometries: geometries
  };
};

TopoJSON.exportGeometries = function(geometries, shapes, coords, type) {
  var exporter = TopoJSON.exporters[type];
  if (exporter && shapes) {
    shapes.forEach(function(shape, i) {
      if (shape && shape.length > 0) {
        geometries[i] = exporter(shape, coords);
      }
    });
  }
};

TopoJSON.exportPolygonGeom = function(shape, coords) {
  var geom = {};
  shape = MapShaper.filterEmptyArcs(shape, coords);
  if (!shape || shape.length === 0) {
    geom.type = null;
  } else if (shape.length > 1) {
    geom.arcs = MapShaper.explodePolygon(shape, coords);
    if (geom.arcs.length == 1) {
      geom.arcs = geom.arcs[0];
      geom.type = "Polygon";
    } else {
      geom.type = "MultiPolygon";
    }
  } else {
    geom.arcs = shape;
    geom.type = "Polygon";
  }
  return geom;
};

TopoJSON.exportLineGeom = function(shape, coords) {
  var geom = {};
  shape = MapShaper.filterEmptyArcs(shape, coords);
  if (!shape || shape.length === 0) {
    geom.type = null;
  } else if (shape.length == 1) {
    geom.type = "LineString";
    geom.arcs = shape[0];
  } else {
    geom.type = "MultiLineString";
    geom.arcs = shape;
  }
  return geom;
};

TopoJSON.exporters = {
  polygon: TopoJSON.exportPolygonGeom,
  polyline: TopoJSON.exportLineGeom,
  point: GeoJSON.exportPointGeom
};




MapShaper.topojson = TopoJSON;

// Convert a TopoJSON topology into mapshaper's internal format
// Side-effect: data in topology is modified
//
MapShaper.importTopoJSON = function(topology, opts) {
  var layers = [],
      dataset, arcs;

  if (utils.isString(topology)) {
    topology = JSON.parse(topology);
  }

  if (topology.arcs && topology.arcs.length > 0) {
    // TODO: apply transform to ArcCollection, not input arcs
    if (topology.transform) {
      TopoJSON.decodeArcs(topology.arcs, topology.transform);
    }

    if (opts && opts.precision) {
      TopoJSON.roundCoords(topology.arcs, opts.precision);
    }

    arcs = new ArcCollection(topology.arcs);
  }

  utils.forEachProperty(topology.objects, function(object, name) {
    var lyr = TopoJSON.importObject(object, opts);

    if (MapShaper.layerHasPaths(lyr)) {
      MapShaper.cleanShapes(lyr.shapes, arcs, lyr.geometry_type);
    }

    lyr.name = name;
    layers.push(lyr);
  });

  dataset = {
    layers: layers,
    arcs: arcs,
    info: {}
  };

  MapShaper.importCRS(dataset, topology);

  return dataset;
};

MapShaper.exportTopoJSON = function(dataset, opts) {
  var topology = TopoJSON.exportTopology(dataset, opts),
      stringify = JSON.stringify,
      filename;
  if (opts.prettify) {
    stringify = MapShaper.getFormattedStringify('coordinates,arcs,bbox,translate,scale'.split(','));
  }
  if (opts.output_file) {
    filename = opts.output_file;
  } else if (dataset.info && dataset.info.input_files) {
    // use base name of input file(s)
    filename = (MapShaper.getCommonFileBase(dataset.info.input_files) || 'output') + '.json';
  } else {
    filename = 'output.json';
  }

  return [{
    content: stringify(topology),
    filename: filename
  }];
};


var ShpType = {
  NULL: 0,
  POINT: 1,
  POLYLINE: 3,
  POLYGON: 5,
  MULTIPOINT: 8,
  POINTZ: 11,
  POLYLINEZ: 13,
  POLYGONZ: 15,
  MULTIPOINTZ: 18,
  POINTM: 21,
  POLYLINEM: 23,
  POLYGONM: 25,
  MULIPOINTM: 28,
  MULTIPATCH: 31 // not supported
};

ShpType.isPolygonType = function(t) {
  return t == 5 || t == 15 || t == 25;
};

ShpType.isPolylineType = function(t) {
  return t == 3 || t == 13 || t == 23;
};

ShpType.isMultiPartType = function(t) {
  return ShpType.isPolygonType(t) || ShpType.isPolylineType(t);
};

ShpType.isMultiPointType = function(t) {
  return t == 8 || t == 18 || t == 28;
};

ShpType.isZType = function(t) {
  return utils.contains([11,13,15,18], t);
};

ShpType.isMType = function(t) {
  return ShpType.isZType(t) || utils.contains([21,23,25,28], t);
};

ShpType.hasBounds = function(t) {
  return ShpType.isMultiPartType(t) || ShpType.isMultiPointType(t);
};





var NullRecord = function() {
  return {
    isNull: true,
    pointCount: 0,
    partCount: 0,
    byteLength: 12
  };
};

// Returns a constructor function for a shape record class with
//   properties and methods for reading coordinate data.
//
// Record properties
//   type, isNull, byteLength, pointCount, partCount (all types)
//
// Record methods
//   read(), readPoints() (all types)
//   readBounds(), readCoords()  (all but single point types)
//   readPartSizes() (polygon and polyline types)
//   readZBounds(), readZ() (Z types except POINTZ)
//   readMBounds(), readM(), hasM() (M and Z types, except POINT[MZ])
//
function ShpRecordClass(type) {
  var hasBounds = ShpType.hasBounds(type),
      hasParts = ShpType.isMultiPartType(type),
      hasZ = ShpType.isZType(type),
      hasM = ShpType.isMType(type),
      singlePoint = !hasBounds,
      mzRangeBytes = singlePoint ? 0 : 16,
      constructor;

  if (type === 0) {
    return NullRecord;
  }

  // @bin is a BinArray set to the first data byte of a shape record
  constructor = function ShapeRecord(bin, bytes) {
    var pos = bin.position();
    this.id = bin.bigEndian().readUint32();
    this.type = bin.littleEndian().skipBytes(4).readUint32();
    if (this.type === 0) {
      return new NullRecord();
    }
    if (bytes > 0 !== true || (this.type != type && this.type !== 0)) {
      error("Unable to read a shape -- .shp file may be corrupted");
    }
    this.byteLength = bytes; // bin.readUint32() * 2 + 8; // bytes in content section + 8 header bytes
    if (singlePoint) {
      this.pointCount = 1;
      this.partCount = 1;
    } else {
      bin.skipBytes(32); // skip bbox
      this.partCount = hasParts ? bin.readUint32() : 1;
      this.pointCount = bin.readUint32();
    }
    this._data = function() {
      return bin.position(pos);
    };
  };

  // base prototype has methods shared by all Shapefile types except NULL type
  // (Type-specific methods are mixed in below)
  var proto = {
    // return offset of [x, y] point data in the record
    _xypos: function() {
      var offs = 12; // skip header & record type
      if (!singlePoint) offs += 4; // skip point count
      if (hasBounds) offs += 32;
      if (hasParts) offs += 4 * this.partCount + 4; // skip part count & index
      return offs;
    },

    readCoords: function() {
      if (this.pointCount === 0) return null;
      var partSizes = this.readPartSizes(),
          xy = this._data().skipBytes(this._xypos());

      return partSizes.map(function(pointCount) {
        return xy.readFloat64Array(pointCount * 2);
      });
    },

    readXY: function() {
      if (this.pointCount === 0) return null;
      return this._data().skipBytes(this._xypos()).readFloat64Array(this.pointCount * 2);
    },

    readPoints: function() {
      var xy = this.readXY(),
          zz = hasZ ? this.readZ() : null,
          mm = hasM && this.hasM() ? this.readM() : null,
          points = [], p;

      for (var i=0, n=xy.length / 2; i<n; i++) {
        p = [xy[i*2], xy[i*2+1]];
        if (zz) p.push(zz[i]);
        if (mm) p.push(mm[i]);
        points.push(p);
      }
      return points;
    },

    read: function() {
      return this.readPoints();
    },

    readPartSizes: function() {
      if (this.partCount == 1) return [this.pointCount];
      if (this.partCount === 0) return [];
      var partLen,
          startId = 0,
          sizes = [],
          bin = this._data().skipBytes(56); // skip to second entry in part index
      for (var i=0, n=this.partCount; i<n; i++) {
        if (i < n - 1)
          partLen = bin.readUint32() - startId;
        else
          partLen = this.pointCount - startId;

        if (partLen <= 0) error("ShapeRecord#readPartSizes() corrupted part");
        sizes.push(partLen);
        startId += partLen;
      }
      return sizes;
    }
  };

  var singlePointProto = {
    read: function() {
      var n = 2;
      if (hasZ) n++;
      if (this.hasM()) n++;
      return this._data().skipBytes(12).readFloat64Array(n);
    }
  };

  var multiCoordProto = {
    readBounds: function() {
      return this._data().skipBytes(12).readFloat64Array(4);
    },

    read: function() {
      var points = this.readPoints();
      var parts = this.readPartSizes().map(function(size) {
          return points.splice(0, size);
        });
      return parts;
    }
  };

  var mProto = {
    _mpos: function() {
      var pos = this._xypos() + this.pointCount * 16;
      if (hasZ) {
        pos += this.pointCount * 8 + mzRangeBytes;
      }
      return pos;
    },

    readMBounds: function() {
      return this.hasM() ? this._data().skipBytes(this._mpos()).readFloat64Array(2) : null;
    },

    // TODO: group into parts, like readCoords()
    readM: function() {
      return this.hasM() ? this._data().skipBytes(this._mpos() + mzRangeBytes).readFloat64Array(this.pointCount) : null;
    },

    // Test if this record contains M data
    // (according to the Shapefile spec, M data is optional in a record)
    //
    hasM: function() {
      var bytesWithoutM = this._mpos(),
          bytesWithM = bytesWithoutM + this.pointCount * 8 + mzRangeBytes;
      if (this.byteLength == bytesWithoutM) {
        return false;
      } else if (this.byteLength == bytesWithM) {
        return true;
      } else {
        error("#hasM() Counting error");
      }
    }
  };

  var zProto = {
    _zpos: function() {
      return this._xypos() + this.pointCount * 16;
    },

    readZBounds: function() {
      return this._data().skipBytes(this._zpos()).readFloat64Array(2);
    },

    // TODO: group into parts, like readCoords()
    readZ: function() {
      return this._data().skipBytes(this._zpos() + mzRangeBytes).readFloat64Array(this.pointCount);
    }
  };

  if (singlePoint) {
    utils.extend(proto, singlePointProto);
  } else {
    utils.extend(proto, multiCoordProto);
  }
  if (hasZ) utils.extend(proto, zProto);
  if (hasM) utils.extend(proto, mProto);

  constructor.prototype = proto;
  proto.constructor = constructor;
  return constructor;
}




// Read data from a .shp file
// @src is an ArrayBuffer, Node.js Buffer or filename
//
//    // Example: iterating using #nextShape()
//    var reader = new ShpReader(buf), s;
//    while (s = reader.nextShape()) {
//      // process the raw coordinate data yourself...
//      var coords = s.readCoords(); // [[x,y,x,y,...], ...] Array of parts
//      var zdata = s.readZ();  // [z,z,...]
//      var mdata = s.readM();  // [m,m,...] or null
//      // .. or read the shape into nested arrays
//      var data = s.read();
//    }
//
//    // Example: reading records using a callback
//    var reader = new ShpReader(buf);
//    reader.forEachShape(function(s) {
//      var data = s.read();
//    });
//
function ShpReader(src) {
  if (this instanceof ShpReader === false) {
    return new ShpReader(src);
  }

  var file = utils.isString(src) ? new FileBytes(src) : new BufferBytes(src);
  var header = parseHeader(file.readBytes(100, 0));
  var fileSize = file.size();
  var RecordClass = new ShpRecordClass(header.type);
  var recordOffs, i, skippedBytes;

  reset();

  this.header = function() {
    return header;
  };

  // Callback interface: for each record in a .shp file, pass a
  //   record object to a callback function
  //
  this.forEachShape = function(callback) {
    var shape = this.nextShape();
    while (shape) {
      callback(shape);
      shape = this.nextShape();
    }
  };

  // Iterator interface for reading shape records
  this.nextShape = function() {
    var shape = readShapeAtOffset(recordOffs, i),
        offs2, skipped;
    if (!shape && recordOffs + 12 <= fileSize) {
      // Very rarely, in-the-wild .shp files may contain junk bytes between
      // records; it may be possible to scan past the junk to find the next record.
      shape = huntForNextShape(recordOffs + 4, i);
    }
    if (shape) {
      recordOffs += shape.byteLength;
      if (shape.id < i) {
        // Encountered in ne_10m_railroads.shp from natural earth v2.0.0
        message("[shp] Record " + shape.id + " appears more than once -- possible file corruption.");
        return this.nextShape();
      }
      i++;
    } else {
      if (skippedBytes > 0) {
        // Encountered in ne_10m_railroads.shp from natural earth v2.0.0
        message("[shp] Skipped " + skippedBytes + " bytes in .shp file -- possible data loss.");
      }
      file.close();
      reset();
    }
    return shape;
  };

  function reset() {
    recordOffs = 100;
    skippedBytes = 0;
    i = 1; // Shapefile id of first record
  }

  function parseHeader(bin) {
    var header = {
      signature: bin.bigEndian().readUint32(),
      byteLength: bin.skipBytes(20).readUint32() * 2,
      version: bin.littleEndian().readUint32(),
      type: bin.readUint32(),
      bounds: bin.readFloat64Array(4), // xmin, ymin, xmax, ymax
      zbounds: bin.readFloat64Array(2),
      mbounds: bin.readFloat64Array(2)
    };

    if (header.signature != 9994) {
      error("Not a valid .shp file");
    }

    var supportedTypes = [1,3,5,8,11,13,15,18,21,23,25,28];
    if (!utils.contains(supportedTypes, header.type))
      error("Unsupported .shp type:", header.type);

    if (header.byteLength != file.size())
      error("File size of .shp doesn't match size in header");

    return header;
  }

  function readShapeAtOffset(recordOffs, i) {
    var shape = null,
        recordSize, recordType, recordId, goodId, goodSize, goodType, bin;

    if (recordOffs + 12 <= fileSize) {
      bin = file.readBytes(12, recordOffs);
      recordId = bin.bigEndian().readUint32();
      // record size is bytes in content section + 8 header bytes
      recordSize = bin.readUint32() * 2 + 8;
      recordType = bin.littleEndian().readUint32();
      goodId = recordId == i; // not checking id ...
      goodSize = recordOffs + recordSize <= fileSize && recordSize >= 12;
      goodType = recordType === 0 || recordType == header.type;
      if (goodSize && goodType) {
        bin = file.readBytes(recordSize, recordOffs);
        shape = new RecordClass(bin, recordSize);
      }
    }
    return shape;
  }

  // TODO: add tests
  // Try to scan past unreadable content to find next record
  function huntForNextShape(start, id) {
    var offset = start,
        shape = null,
        bin, recordId, recordType;
    while (offset + 12 <= fileSize) {
      bin = file.readBytes(12, offset);
      recordId = bin.bigEndian().readUint32();
      recordType = bin.littleEndian().skipBytes(4).readUint32();
      if (recordId == id && (recordType == header.type || recordType === 0)) {
        // we have a likely position, but may still be unparsable
        shape = readShapeAtOffset(offset, id);
        break;
      }
      offset += 4; // try next integer position
    }
    skippedBytes += shape ? offset - start : fileSize - start;
    return shape;
  }
}

ShpReader.prototype.type = function() {
  return this.header().type;
};

ShpReader.prototype.getCounts = function() {
  var counts = {
    nullCount: 0,
    partCount: 0,
    shapeCount: 0,
    pointCount: 0
  };
  this.forEachShape(function(shp) {
    if (shp.isNull) counts.nullCount++;
    counts.pointCount += shp.pointCount;
    counts.partCount += shp.partCount;
    counts.shapeCount++;
  });
  return counts;
};

// Same interface as FileBytes, for reading from a buffer instead of a file.
function BufferBytes(buf) {
  var bin = new BinArray(buf),
      bufSize = bin.size();
  this.readBytes = function(len, offset) {
    if (bufSize < offset + len) error("Out-of-range error");
    bin.position(offset);
    return bin;
  };

  this.size = function() {
    return bufSize;
  };

  this.close = function() {};
}

// Read a binary file in chunks, to support files > 1GB in Node
function FileBytes(path) {
  var DEFAULT_BUF_SIZE = 0xffffff, // 16 MB
      fs = require('fs'),
      fileSize = cli.fileSize(path),
      cacheOffs = 0,
      cache, fd;

  this.readBytes = function(len, start) {
    if (fileSize < start + len) error("Out-of-range error");
    if (!cache || start < cacheOffs || start + len > cacheOffs + cache.size()) {
      updateCache(len, start);
    }
    cache.position(start - cacheOffs);
    return cache;
  };

  this.size = function() {
    return fileSize;
  };

  this.close = function() {
    if (fd) {
      fs.closeSync(fd);
      fd = null;
      cache = null;
      cacheOffs = 0;
    }
  };

  function updateCache(len, start) {
    var headroom = fileSize - start,
        bufSize = Math.min(headroom, Math.max(DEFAULT_BUF_SIZE, len)),
        buf = new Buffer(bufSize),
        bytesRead;
    if (!fd) fd = fs.openSync(path, 'r');
    bytesRead = fs.readSync(fd, buf, 0, bufSize, start);
    if (bytesRead < bufSize) error("Error reading file");
    cacheOffs = start;
    cache = new BinArray(buf);
  }
}





MapShaper.importDbfTable = function(buf, opts) {
  return new ShapefileTable(buf, opts && opts.encoding);
};

MapShaper.exportDbf = function(dataset, opts) {
  return dataset.layers.reduce(function(files, lyr) {
    if (lyr.data) {
      files = files.concat(MapShaper.exportDbfFile(lyr, dataset, opts));
    }
    return files;
  }, []);
};

MapShaper.exportDbfFile = function(lyr, dataset, opts) {
  var data = lyr.data,
      buf;
  // create empty data table if missing a table or table is being cut out
  if (!data || opts.cut_table || opts.drop_table) {
    data = new DataTable(lyr.shapes.length);
  }
  // dbfs should have at least one column; add id field if none
  if (data.getFields().length === 0) {
    data.addIdField();
  }
  buf = data.exportAsDbf(opts.encoding || 'utf8');
  if (utils.isInteger(opts.ldid)) {
    new Uint8Array(buf)[29] = opts.ldid; // set language driver id
  }
  // TODO: also export .cpg page
  return [{
    content: buf,
    filename: lyr.name + '.dbf'
  }];
};

// Implements the DataTable api for DBF file data.
// We avoid touching the raw DBF field data if possible. This way, we don't need
// to parse the DBF at all in common cases, like importing a Shapefile, editing
// just the shapes and exporting in Shapefile format.
// TODO: consider accepting just the filename, so buffer doesn't consume memory needlessly.
//
function ShapefileTable(buf, encoding) {
  var reader = new DbfReader(buf, encoding),
      table;

  function getTable() {
    if (!table) {
      // export DBF records on first table access
      table = new DataTable(reader.readRows());
      reader = null;
      buf = null; // null out references to DBF data for g.c.
    }
    return table;
  }

  this.exportAsDbf = function(encoding) {
    // export original dbf string if records haven't been touched.
    return table ? table.exportAsDbf(encoding) : reader.bin.buffer();
  };

  this.getRecords = function() {
    return getTable().getRecords();
  };

  this.getFields = function() {
    return reader ? utils.pluck(reader.header.fields, 'name') : table.getFields();
  };

  this.size = function() {
    return reader ? reader.rows() : table.size();
  };
}

utils.extend(ShapefileTable.prototype, dataTableProto);
MapShaper.ShapefileTable = ShapefileTable;




MapShaper.translateShapefileType = function(shpType) {
  if (utils.contains([ShpType.POLYGON, ShpType.POLYGONM, ShpType.POLYGONZ], shpType)) {
    return 'polygon';
  } else if (utils.contains([ShpType.POLYLINE, ShpType.POLYLINEM, ShpType.POLYLINEZ], shpType)) {
    return 'polyline';
  } else if (utils.contains([ShpType.POINT, ShpType.POINTM, ShpType.POINTZ,
      ShpType.MULTIPOINT, ShpType.MULTIPOINTM, ShpType.MULTIPOINTZ], shpType)) {
    return 'point';
  }
  return null;
};

MapShaper.getShapefileType = function(type) {
  if (type === null) return ShpType.NULL;
  return {
    polygon: ShpType.POLYGON,
    polyline: ShpType.POLYLINE,
    point: ShpType.MULTIPOINT  // TODO: use POINT when possible
  }[type] || null;
};

// Read Shapefile data from a file, ArrayBuffer or Buffer
// @src filename or buffer
MapShaper.importShp = function(src, opts) {
  var reader = new ShpReader(src),
      shpType = reader.type(),
      type = MapShaper.translateShapefileType(shpType),
      maxPoints = Math.round(reader.header().byteLength / 16), // for reserving buffer space
      importer = new PathImporter(opts, maxPoints);

  if (!type) {
    stop("Unsupported Shapefile type:", shpType);
  }
  if (ShpType.isZType(shpType)) {
    message("Warning: Shapefile Z data will be lost.");
  } else if (ShpType.isMType(shpType)) {
    message("Warning: Shapefile M data will be lost.");
  }

  // TODO: test cases: null shape; non-null shape with no valid parts
  reader.forEachShape(function(shp) {
    importer.startShape();
    if (shp.isNull) return;
    if (type == 'point') {
      importer.importPoints(shp.readPoints());
    } else {
      var xy = shp.readXY(),
          parts = shp.readPartSizes(),
          start = 0,
          len;

      for (var i=0; i<parts.length; i++) {
        len = parts[i] * 2;
        importer.importPathFromFlatArray(xy, type, len, start);
        start += len;
      }
    }
  });

  return importer.done();
};

// Convert a dataset to Shapefile files
MapShaper.exportShapefile = function(dataset, opts) {
  return dataset.layers.reduce(function(files, lyr) {
    var prj = MapShaper.exportPrjFile(lyr, dataset);
    files = files.concat(MapShaper.exportShpAndShxFiles(lyr, dataset, opts));
    files = files.concat(MapShaper.exportDbfFile(lyr, dataset, opts));
    if (prj) files.push(prj);
    return files;
  }, []);
};

MapShaper.exportPrjFile = function(lyr, dataset) {
  var outputPrj = dataset.info.output_prj;
  if (!outputPrj && outputPrj !== null) { // null value indicates crs is unknown
    outputPrj = dataset.info.input_prj;
  }
  return outputPrj ? {
    content: outputPrj,
    filename: lyr.name + '.prj'
  } : null;
};

MapShaper.exportShpAndShxFiles = function(layer, dataset, opts) {
  var geomType = layer.geometry_type;
  var shpType = MapShaper.getShapefileType(geomType);
  if (shpType === null) {
    error("[exportShpAndShx()] Unable to export geometry type:", geomType);
  }

  var fileBytes = 100;
  var bounds = new Bounds();
  var shapeBuffers = layer.shapes.map(function(shape, i) {
    var pathData = MapShaper.exportPathData(shape, dataset.arcs, geomType);
    var rec = MapShaper.exportShpRecord(pathData, i+1, shpType);
    fileBytes += rec.buffer.byteLength;
    if (rec.bounds) bounds.mergeBounds(rec.bounds);
    return rec.buffer;
  });

  // write .shp header section
  var shpBin = new BinArray(fileBytes, false)
    .writeInt32(9994)
    .skipBytes(5 * 4)
    .writeInt32(fileBytes / 2)
    .littleEndian()
    .writeInt32(1000)
    .writeInt32(shpType);

  if (bounds.hasBounds()) {
    shpBin.writeFloat64(bounds.xmin || 0) // using 0s as empty value
      .writeFloat64(bounds.ymin || 0)
      .writeFloat64(bounds.xmax || 0)
      .writeFloat64(bounds.ymax || 0);
  } else {
    // no bounds -- assume no shapes or all null shapes -- using 0s as bbox
    shpBin.skipBytes(4 * 8);
  }

  shpBin.skipBytes(4 * 8); // skip Z & M type bounding boxes;

  // write .shx header
  var shxBytes = 100 + shapeBuffers.length * 8;
  var shxBin = new BinArray(shxBytes, false)
    .writeBuffer(shpBin.buffer(), 100) // copy .shp header to .shx
    .position(24)
    .bigEndian()
    .writeInt32(shxBytes/2)
    .position(100);

  // write record sections of .shp and .shx
  shapeBuffers.forEach(function(buf, i) {
    var shpOff = shpBin.position() / 2,
        shpSize = (buf.byteLength - 8) / 2; // alternative: shxBin.writeBuffer(buf, 4, 4);
    shxBin.writeInt32(shpOff);
    shxBin.writeInt32(shpSize);
    shpBin.writeBuffer(buf);
  });

  return [{
      content: shpBin.buffer(),
      filename: layer.name + ".shp"
    }, {
      content: shxBin.buffer(),
      filename: layer.name + ".shx"
    }];
};

// Returns an ArrayBuffer containing a Shapefile record for one shape
//   and the bounding box of the shape.
// TODO: remove collapsed rings, convert to null shape if necessary
//
MapShaper.exportShpRecord = function(data, id, shpType) {
  var bounds = null,
      bin = null;
  if (data.pointCount > 0) {
    var multiPart = ShpType.isMultiPartType(shpType),
        partIndexIdx = 52,
        pointsIdx = multiPart ? partIndexIdx + 4 * data.pathCount : 48,
        recordBytes = pointsIdx + 16 * data.pointCount,
        pointCount = 0;

    bounds = data.bounds;
    bin = new BinArray(recordBytes, false)
      .writeInt32(id)
      .writeInt32((recordBytes - 8) / 2)
      .littleEndian()
      .writeInt32(shpType)
      .writeFloat64(bounds.xmin)
      .writeFloat64(bounds.ymin)
      .writeFloat64(bounds.xmax)
      .writeFloat64(bounds.ymax);

    if (multiPart) {
      bin.writeInt32(data.pathCount);
    } else {
      if (data.pathData.length > 1) {
        error("[exportShpRecord()] Tried to export multiple paths as type:", shpType);
      }
    }

    bin.writeInt32(data.pointCount);

    data.pathData.forEach(function(path, i) {
      if (multiPart) {
        bin.position(partIndexIdx + i * 4).writeInt32(pointCount);
      }
      bin.position(pointsIdx + pointCount * 16);

      var points = path.points;
      for (var j=0, len=points.length; j<len; j++) {
        bin.writeFloat64(points[j][0]);
        bin.writeFloat64(points[j][1]);
      }
      pointCount += j;
    });
    if (data.pointCount != pointCount)
      error("Shp record point count mismatch; pointCount:",
          pointCount, "data.pointCount:", data.pointCount);

  } else {
    // no data -- export null record
    bin = new BinArray(12, false)
      .writeInt32(id)
      .writeInt32(2)
      .littleEndian()
      .writeInt32(0);
  }

  return {bounds: bounds, buffer: bin.buffer()};
};




// Return a copy of a dataset with all coordinates rounded without modifying
// the original dataset
//
MapShaper.setCoordinatePrecision = function(dataset, precision) {
  var round = geom.getRoundingFunction(precision),
      d2 = MapShaper.copyDataset(dataset), // copies arc data
      dissolvePolygon, nodes;

  if (d2.arcs) {
    d2.arcs.applyTransform(null, round);
    nodes = MapShaper.divideArcs(d2);
    dissolvePolygon = MapShaper.getPolygonDissolver(nodes);
  }

  d2.layers.forEach(function(lyr) {
    if (MapShaper.layerHasPoints(lyr)) {
      MapShaper.roundPoints(lyr, round);
    } else if (lyr.geometry_type == 'polygon' && dissolvePolygon) {
      // clean each polygon -- use dissolve function to remove spikes
      // TODO: better handling of corrupted polygons
      lyr.shapes = lyr.shapes.map(dissolvePolygon);
    }
  });
  return d2;
};

MapShaper.roundPoints = function(lyr, round) {
  MapShaper.forEachPoint(lyr, function(p) {
    p[0] = round(p[0]);
    p[1] = round(p[1]);
  });
};




// Generate output content from a dataset object
MapShaper.exportDelim = function(dataset, opts) {
  var delim = MapShaper.getExportDelimiter(dataset.info, opts),
      ext = MapShaper.getDelimFileExtension(delim, opts);
  return dataset.layers.reduce(function(arr, lyr) {
    if (lyr.data){
      arr.push({
        // TODO: consider supporting encoding= option
        content: MapShaper.exportDelimTable(lyr, delim),
        filename: (lyr.name || 'output') + '.' + ext
      });
    }
    return arr;
  }, []);
};

MapShaper.exportDelimTable = function(lyr, delim) {
  var dsv = require("./lib/d3/d3-dsv.js").dsv(delim);
  return dsv.format(lyr.data.getRecords());
};

MapShaper.getExportDelimiter = function(info, opts) {
  var delim = ','; // default
  var outputExt = opts.output_file ? utils.getFileExtension(opts.output_file) : '';
  if (opts.delimiter) {
    delim = opts.delimiter;
  } else if (outputExt == 'tsv') {
    delim = '\t';
  } else if (outputExt == 'csv') {
    delim = ',';
  } else if (info.input_delimiter) {
    delim = info.input_delimiter;
  }
  return delim;
};

// If output filename is not specified, use the delimiter char to pick
// an extension.
MapShaper.getDelimFileExtension = function(delim, opts) {
  var ext = 'txt'; // default
  if (opts.output_file) {
    ext = utils.getFileExtension(opts.output_file);
  } else if (delim == '\t') {
    ext = 'tsv';
  } else if (delim == ',') {
    ext = 'csv';
  }
  return ext;
};




MapShaper.importJSONTable = function(arr) {
  return {
    layers: [{
      data: new DataTable(arr)
    }],
    info: {}
  };
};

MapShaper.exportJSON = function(dataset, opts) {
  return dataset.layers.reduce(function(arr, lyr) {
    if (lyr.data){
      arr.push({
        content: MapShaper.exportJSONTable(lyr),
        filename: (lyr.name || 'output') + '.json'
      });
    }
    return arr;
  }, []);
};

MapShaper.exportJSONTable = function(lyr) {
  return JSON.stringify(lyr.data.getRecords());
};




// Return an array of objects with "filename" "filebase" "extension" and
// "content" attributes.
//
MapShaper.exportFileContent = function(dataset, opts) {
  var outFmt = opts.format = MapShaper.getOutputFormat(dataset, opts),
      exporter = MapShaper.exporters[outFmt],
      layers = dataset.layers,
      files = [];

  if (!outFmt) {
    error("[o] Missing output format");
  } else if (!exporter) {
    error("[o] Unknown export format:", outFmt);
  }

  if (opts.output_file && outFmt != 'topojson') {
    layers.forEach(function(lyr) {
      lyr.name = utils.getFileBase(opts.output_file);
    });
  }

  if (opts.precision) {
    dataset = MapShaper.setCoordinatePrecision(dataset, opts.precision);
  }

  MapShaper.validateLayerData(layers);
  MapShaper.assignUniqueLayerNames(layers);

  if (opts.cut_table) {
    files = MapShaper.exportDataTables(layers, opts).concat(files);
  }

  files = exporter(dataset, opts).concat(files);
  // If rounding or quantization are applied during export, bounds may
  // change somewhat... consider adding a bounds property to each layer during
  // export when appropriate.
  if (opts.bbox_index) {
    files.push(MapShaper.createIndexFile(dataset));
  }

  MapShaper.validateFileNames(files);
  return files;
};

MapShaper.exporters = {
  geojson: MapShaper.exportGeoJSON,
  topojson: MapShaper.exportTopoJSON,
  shapefile: MapShaper.exportShapefile,
  dsv: MapShaper.exportDelim,
  dbf: MapShaper.exportDbf,
  json: MapShaper.exportJSON
};

MapShaper.getOutputFormat = function(dataset, opts) {
  var outFile = opts.output_file || null,
      inFmt = dataset.info && dataset.info.input_format,
      outFmt = null;

  if (opts.format) {
    outFmt = opts.format;
  } else if (outFile) {
    outFmt = MapShaper.inferOutputFormat(outFile, inFmt);
  } else if (inFmt) {
    outFmt = inFmt;
  }
  return outFmt;
};

// Generate json file with bounding boxes and names of each export layer
// TODO: consider making this a command, or at least make format settable
//
MapShaper.createIndexFile = function(dataset) {
  var index = dataset.layers.map(function(lyr) {
    var bounds = MapShaper.getLayerBounds(lyr, dataset.arcs);
    return {
      bbox: bounds.toArray(),
      name: lyr.name
    };
  });

  return {
    content: JSON.stringify(index),
    filename: "bbox-index.json"
  };
};

MapShaper.validateLayerData = function(layers) {
  layers.forEach(function(lyr) {
    if (!lyr.geometry_type) {
      // allowing data-only layers
      if (lyr.shapes && utils.some(lyr.shapes, function(o) {
        return !!o;
      })) {
        error("[export] A layer contains shape records and a null geometry type");
      }
    } else {
      if (!utils.contains(['polygon', 'polyline', 'point'], lyr.geometry_type)) {
        error ("[export] A layer has an invalid geometry type:", lyr.geometry_type);
      }
      if (!lyr.shapes) {
        error ("[export] A layer is missing shape data");
      }
    }
  });
};

MapShaper.validateFileNames = function(files) {
  var index = {};
  files.forEach(function(file, i) {
    var filename = file.filename;
    if (!filename) error("[o] Missing a filename for file" + i);
    if (filename in index) error("[o] Duplicate filename", filename);
    index[filename] = true;
  });
};

MapShaper.assignUniqueLayerNames = function(layers) {
  var names = layers.map(function(lyr) {
    return lyr.name || "layer";
  });
  var uniqueNames = MapShaper.uniqifyNames(names);
  layers.forEach(function(lyr, i) {
    lyr.name = uniqueNames[i];
  });
};

/*
MapShaper.getDefaultFileExtension = function(fileType) {
  var ext = "";
  if (fileType == 'shapefile') {
    ext = 'shp';
  } else if (fileType == 'geojson' || fileType == 'topojson') {
    ext = "json";
  }
  return ext;
};
*/

MapShaper.exportDataTables = function(layers, opts) {
  var tables = [];
  layers.forEach(function(lyr) {
    if (lyr.data) {
      tables.push({
        content: lyr.data.exportAsJSON(), // TODO: other formats
        filename: (lyr.name ? lyr.name + '-' : '') + 'table.json'
      });
    }
  });
  return tables;
};

MapShaper.uniqifyNames = function(names) {

  var counts = utils.countValues(names),
      index = {},
      suffix;
  return names.map(function(name) {
    var count = counts[name],
        i = 1;
    if (count > 1 || name in index) {
      do {
        suffix = String(i);
        if (/[0-9]$/.test(name)) {
          suffix = '-' + suffix;
        }
        i++;
      } while ((name + suffix) in index);
      name = name + suffix;
    }
    index[name] = true;
    return name;
  });
};




api.evaluateEachFeature = function(lyr, arcs, exp, opts) {
  var n = MapShaper.getFeatureCount(lyr),
      compiled, filter;

  // TODO: consider not creating a data table -- not needed if expression only references geometry
  if (n > 0 && !lyr.data) {
    lyr.data = new DataTable(n);
  }
  if (opts && opts.where) {
    filter = MapShaper.compileFeatureExpression(opts.where, lyr, arcs);
  }
  compiled = MapShaper.compileFeatureExpression(exp, lyr, arcs);
  // call compiled expression with id of each record
  for (var i=0; i<n; i++) {
    if (!filter || filter(i)) {
      compiled(i);
    }
  }
};




// Calculate an expression across a group of features, print and return the result
// Supported functions include sum(), average(), max(), min(), median(), count()
// Functions receive a field name or a feature expression (like the -each command)
// Examples: 'sum("$.area")' 'min(income)'
// opts.expression  Expression to evaluate
// opts.where  Optional filter expression (like -filter command)
//
api.calc = function(lyr, arcs, opts) {
  var msg = 'calc ' + opts.expression,
      result;
  if (opts.where) {
    // TODO: implement no_replace option for filter() instead of this
    lyr = {
      shapes: lyr.shapes,
      data: lyr.data
    };
    api.filterFeatures(lyr, arcs, {expression: opts.where});
    msg += ' where ' + opts.where;
  }
  result = MapShaper.evalCalcExpression(lyr, arcs, opts.expression);
  message(msg + ":  " + result);
  return result;
};

MapShaper.evalCalcExpression = function(lyr, arcs, exp) {
  var calc = MapShaper.compileCalcExpression(exp);
  return calc(lyr, arcs);
};

// Return a function to evaluate a calc expression
// (also used by mapshaper-subdivide.js)
MapShaper.compileCalcExpression = function(exp) {
  return function(lyr, arcs) {
    var env = MapShaper.getCalcExpressionContext(lyr, arcs),
        calc, retn;
    try {
      calc = new Function("env", "with(env){return " + exp + ";}");
      retn = calc.call(null, env);
    } catch(e) {
      message('Error ' + (calc ? 'compiling' : 'running') + ' expression: "' + exp + '"');
      stop(e);
    }
    return retn;
  };
};

MapShaper.getCalcExpressionContext = function(lyr, arcs) {
  var env = MapShaper.getBaseContext();
  if (lyr.data) {
    lyr.data.getFields().forEach(function(f) {
      env[f] = f;
    });
  }
  MapShaper.initCalcFunctions(env, lyr, arcs);
  return env;
};

MapShaper.initCalcFunctions = function(env, lyr, arcs) {
  var functions = Object.keys(new FeatureCalculator().functions);
  functions.forEach(function(fname) {
    env[fname] = MapShaper.getCalcFunction(fname, lyr, arcs);
  });
};

MapShaper.getCalcFunction = function(fname, lyr, arcs) {
  return function(rawExp) {
    var exp = MapShaper.validateExpression(rawExp);
    var calculator = new FeatureCalculator();
    var func = calculator.functions[fname];
    var compiled = MapShaper.compileFeatureExpression(exp, lyr, arcs);
    utils.repeat(MapShaper.getFeatureCount(lyr), function(i) {
      func(compiled(i));
    });
    return calculator.done()[fname];
  };
};

function FeatureCalculator() {
  var api = {},
      count = 0,
      sum = 0,
      sumFlag = false,
      avgSum = 0,
      avgCount = 0,
      min = Infinity,
      max = -Infinity,
      medianArr = [];

  api.sum = function(val) {
    sum += val;
    sumFlag = true;
  };

  api.count = function() {
    count++;
  };

  api.average = function(val) {
    avgCount++;
    avgSum += val;
  };

  api.median = function(val) {
    medianArr.push(val);
  };

  api.max = function(val) {
    if (val > max) max = val;
  };

  api.min = function(val) {
    if (val < min) min = val;
  };

  function done() {
    var results = {};
    if (sumFlag) results.sum = sum;
    if (avgCount > 0) results.average = avgSum / avgCount;
    if (medianArr.length > 0) results.median = utils.findMedian(medianArr);
    if (min < Infinity) results.min = min;
    if (max > -Infinity) results.max = max;
    if (count > 0) results.count = count;
    return results;
  }

  return {
    done: done,
    functions: api
  };
}




// Parse content of one or more input files and return a dataset
// @obj: file data, indexed by file type
// File data objects have two properties:
//    content: Buffer, ArrayBuffer, String or Object
//    filename: String or null
//
MapShaper.importContent = function(obj, opts) {
  var dataset, content, fileFmt, data;
  opts = opts || {};
  if (obj.json) {
    data = obj.json;
    content = data.content;
    if (utils.isString(content)) {
      content = JSON.parse(content);
    }
    if (content.type == 'Topology') {
      fileFmt = 'topojson';
      dataset = MapShaper.importTopoJSON(content, opts);
    } else if (content.type) {
      fileFmt = 'geojson';
      dataset = MapShaper.importGeoJSON(content, opts);
    } else if (utils.isArray(content)) {
      fileFmt = 'json';
      dataset = MapShaper.importJSONTable(content, opts);
    }
  } else if (obj.text) {
    fileFmt = 'dsv';
    data = obj.text;
    dataset = MapShaper.importDelim(data.content, opts);
  } else if (obj.shp) {
    fileFmt = 'shapefile';
    data = obj.shp;
    dataset = MapShaper.importShapefile(obj, opts);
  } else if (obj.dbf) {
    fileFmt = 'dbf';
    data = obj.dbf;
    dataset = MapShaper.importDbf(obj, opts);
  }

  if (!dataset) {
    stop("Missing an expected input type");
  }

  // Convert to topological format, if needed
  if (dataset.arcs && !opts.no_topology && fileFmt != 'topojson') {
    T.start();
    api.buildTopology(dataset);
    T.stop("Process topology");
  }

  // Use file basename for layer name, except TopoJSON, which uses object names
  if (fileFmt != 'topojson') {
    MapShaper.setLayerName(dataset.layers[0], MapShaper.filenameToLayerName(data.filename || ''));
  }

  // Add input filename and format to the dataset's 'info' object
  // (this is useful when exporting if format or name has not been specified.)
  if (data.filename) {
    dataset.info.input_files = [data.filename];
  }
  dataset.info.input_format = fileFmt;

  return dataset;
};

// Deprecated (included for compatibility with older tests)
MapShaper.importFileContent = function(content, filename, opts) {
  var type = MapShaper.guessInputType(filename, content),
      input = {};
  input[type] = {filename: filename, content: content};
  return MapShaper.importContent(input, opts);
};

MapShaper.importShapefile = function(obj, opts) {
  var shpSrc = obj.shp.content || obj.shp.filename, // content may be missing
      dataset = MapShaper.importShp(shpSrc, opts),
      lyr = dataset.layers[0],
      dbf;
  if (obj.dbf) {
    dbf = MapShaper.importDbf(obj, opts);
    utils.extend(dataset.info, dbf.info);
    lyr.data = dbf.layers[0].data;
    if (lyr.data.size() != lyr.shapes.length) {
      message("[shp] Mismatched .dbf and .shp record count -- possible data loss.");
    }
  }
  if (obj.prj) {
    dataset.info.input_prj = obj.prj.content;
  }
  return dataset;
};

MapShaper.importDbf = function(input, opts) {
  var table;
  opts = utils.extend({}, opts);
  if (input.cpg && !opts.encoding) {
    opts.encoding = input.cpg.content;
  }
  table = MapShaper.importDbfTable(input.dbf.content, opts);
  return {
    info: {},
    layers: [{data: table}]
  };
};

MapShaper.filenameToLayerName = function(path) {
  var name = 'layer1';
  var obj = utils.parseLocalPath(path);
  if (obj.basename && obj.extension) { // exclude paths like '/dev/stdin'
    name = obj.basename;
  }
  return name;
};

// initialize layer name using filename
MapShaper.setLayerName = function(lyr, path) {
  if (!lyr.name) {
    lyr.name = utils.getFileBase(path);
  }
};




api.importFiles = function(opts) {
  var files = opts.files ? cli.validateInputFiles(opts.files) : [],
      dataset;
  if ((opts.merge_files || opts.combine_files) && files.length > 1) {
    dataset = api.mergeFiles(files, opts);
  } else if (files.length == 1) {
    dataset = api.importFile(files[0], opts);
  } else if (opts.stdin) {
    dataset = api.importFile('/dev/stdin', opts);
  } else {
    stop('Missing input file(s)');
  }
  return dataset;
};

api.importFile = function(path, opts) {
  cli.checkFileExists(path);
  var isBinary = MapShaper.isBinaryFile(path),
      isShp = MapShaper.guessInputFileType(path) == 'shp',
      input = {},
      type, content;

  if (isShp) {
    content = null; // let ShpReader read the file (supports larger files)
  } else if (isBinary) {
    content = cli.readFile(path);
  } else {
    content = cli.readFile(path, opts && opts.encoding || 'utf-8');
  }

  type = MapShaper.guessInputType(path, content) || error("Unkown file type:", path);
  input[type] = {filename: path, content: content};
  if (type == 'shp' || type == 'dbf') {
    MapShaper.readShapefileAuxFiles(path, input);
  }
  if (type == 'shp' && !input.dbf) {
    message(utils.format("[%s] .dbf file is missing -- shapes imported without attribute data.", path));
  }
  return MapShaper.importContent(input, opts);
};

api.importDataTable = function(path, opts) {
  // TODO: avoid the overhead of importing shape data, if present
  var dataset = api.importFile(path, opts);
  return dataset.layers[0].data;
};

MapShaper.readShapefileAuxFiles = function(path, obj) {
  var dbfPath = utils.replaceFileExtension(path, 'dbf');
  var cpgPath = utils.replaceFileExtension(path, 'cpg');
  var prjPath = utils.replaceFileExtension(path, 'prj');
  if (cli.isFile(prjPath)) {
    obj.prj = {filename: prjPath, content: cli.readFile(prjPath, 'utf-8')};
  }
  if (!obj.dbf && cli.isFile(dbfPath)) {
    obj.dbf = {filename: dbfPath, content: cli.readFile(dbfPath)};
  }
  if (obj.dbf && cli.isFile(cpgPath)) {
    obj.cpg = {filename: cpgPath, content: cli.readFile(cpgPath, 'utf-8').trim()};
  }
};




// TODO: remove?
api.exportFiles = function(dataset, opts) {
  MapShaper.writeFiles(MapShaper.exportFileContent(dataset, opts), opts);
};

MapShaper.writeFiles = function(exports, opts, cb) {
  if (exports.length > 0 === false) {
    message("No files to save");
  } else if (opts.stdout) {
    cli.writeFile('/dev/stdout', exports[0].content);
  } else {
    var paths = MapShaper.getOutputPaths(utils.pluck(exports, 'filename'), opts);
    exports.forEach(function(obj, i) {
      var path = paths[i];
      cli.writeFile(path, obj.content);
      message("Wrote " + path);
    });
  }
  if (cb) cb(null);
};

MapShaper.getOutputPaths = function(files, opts) {
  var odir = opts.output_dir;
  if (odir) {
    files = files.map(function(file) {
      return require('path').join(odir, file);
    });
  }
  if (!opts.force) {
    files = resolveFileCollisions(files);
  }
  return files;
};

// Avoid naming conflicts with existing files
// by adding file suffixes to output filenames: -ms, -ms2, -ms3 etc.
function resolveFileCollisions(candidates) {
  var i = 0,
      suffix = "",
      paths = candidates.concat();

  while (testFileCollision(paths)) {
    i++;
    suffix = "-ms";
    if (i > 1) suffix += String(i);
    paths = addFileSuffix(candidates, suffix);
  }
  return paths;
}

function addFileSuffix(paths, suff) {
  return paths.map(function(path) {
     return utils.getPathBase(path) + suff + '.' + utils.getFileExtension(path);
  });
}

function testFileCollision(paths) {
  return utils.some(paths, function(path) {
    return cli.isFile(path) || cli.isDirectory(path);
  });
}




api.filterFields = function(lyr, names) {
  MapShaper.updateFields(lyr, names, "filter-fields");
};

api.renameFields = function(lyr, names) {
  MapShaper.updateFields(lyr, names, "rename-fields");
};

MapShaper.updateFields = function(lyr, names, cmd) {
  if (!lyr.data) {
    stop("[filter-fields] Layer is missing a data table");
  } else if (!utils.isArray(names)) {
    stop("[filter-fields] Expected an array of field names; found:", names);
  }

  var dataFields = lyr.data.getFields(),
      fieldMap = MapShaper.mapFieldNames(names, {}),
      mappedFields = Object.keys(fieldMap),
      unmappedFields = utils.difference(dataFields, mappedFields),
      missingFields = utils.difference(mappedFields, dataFields);

  if (missingFields.length > 0) {
    stop("[" + cmd + "] Table is missing one or more specified fields:\n",
        missingFields, "\nExisting fields:", '\n' + MapShaper.formatStringsAsGrid(dataFields));
  }

  if (cmd == "rename-fields" && unmappedFields.length > 0) {
    // add unmapped fields to the map, so all fields are retained
    MapShaper.mapFieldNames(unmappedFields, fieldMap);
  }

  lyr.data.update(MapShaper.getRecordMapper(fieldMap));
};

MapShaper.mapFieldNames = function(names, fieldMap) {
  return names.reduce(function(memo, str) {
    var parts = str.split('=');
    var dest = parts[0],
        src = parts[1] || dest;
    if (!src || !dest) stop("[fields] Invalid field description:", str);
    memo[src] = dest;
    return memo;
  }, fieldMap || {});
};

MapShaper.getRecordMapper = function(map) {
  var fields = Object.keys(map);
  return function(src) {
    var dest = {}, key;
    for (var i=0, n=fields.length; i<n; i++) {
      key = fields[i];
      dest[map[key]] = src[key];
    }
    return dest;
  };
};




api.printInfo = function(dataset, opts) {
  // str += utils.format("Number of layers: %d\n", dataset.layers.length);
  // if (dataset.arcs) str += utils.format("Topological arcs: %'d\n", dataset.arcs.size());
  var str = dataset.layers.map(function(lyr, i) {
    var infoStr = MapShaper.getLayerInfo(lyr, dataset.arcs);
    if (dataset.layers.length > 1) {
      infoStr = 'Layer ' + (i + 1) + '\n' + infoStr;
    }
    return infoStr;
  }).join('\n\n');
  message(str);
};

// TODO: consider polygons with zero area or other invalid geometries
MapShaper.countNullShapes = function(shapes) {
  var count = 0;
  for (var i=0; i<shapes.length; i++) {
    if (!shapes[i] || shapes[i].length === 0) count++;
  }
  return count;
};

MapShaper.getLayerInfo = function(lyr, arcs) {
  var shapeCount = lyr.shapes ? lyr.shapes.length : 0,
      nullCount = shapeCount > 0 ? MapShaper.countNullShapes(lyr.shapes) : 0,
      tableSize = lyr.data ? lyr.data.size() : 0,
      str;
  str = "Name: " + (lyr.name || "[unnamed]") + "\n";
  str += "Geometry: " + (lyr.geometry_type || "[none]") + "\n";
  str += utils.format("Records: %,d\n", Math.max(shapeCount, tableSize));
  if (nullCount > 0) {
    str += utils.format("Null shapes: %'d\n", nullCount);
  }
  if (shapeCount > nullCount) {
    str += "Bounds: " + MapShaper.getLayerBounds(lyr, arcs).toArray().join(' ') + "\n";
  }
  if (tableSize > 0 && lyr.data.getFields().length > 0) {
    str += MapShaper.getTableInfo(lyr.data);
  } else {
    str += "Missing attribute data";
  }
  return str;
};

MapShaper.getTableInfo = function(data) {
  var fields = data.getFields().sort();
  var replacements = {
    '\n': '\\n',
    '\r': '\\r',
    '\t': '\\t'
  };
  var cleanChar = function(c) {
    // convert newlines and carriage returns
    // TODO: better handling of non-printing chars
    return c in replacements ? replacements[c] : '';
  };
  var col1Chars = fields.reduce(function(memo, name) {
    return Math.max(memo, name.length);
  }, 5) + 2;
  var vals = fields.map(function(fname) {
    return data.getRecords()[0][fname];
  });
  var digits = vals.map(function(val, i) {
    return utils.isNumber(vals[i]) ? (val + '.').indexOf('.') + 1 :  0;
  });
  var maxDigits = Math.max.apply(null, digits);
  var table = vals.map(function(val, i) {
    var str = '  ' + utils.rpad(fields[i], col1Chars, ' ');
    if (utils.isNumber(val)) {
      str += utils.lpad("", maxDigits - digits[i], ' ') + val;
    } else if (utils.isString(val)) {
      val = val.replace(/[\r\t\n]/g, cleanChar);
      str += "'" + val + "'";
    } else {
      str += String(val);
    }
    return str;
  }).join('\n');
  return "Data table\n  " +
      utils.rpad('Field', col1Chars, ' ') + "First value\n" + table;
};

MapShaper.getSimplificationInfo = function(arcs) {
  var nodeCount = new NodeCollection(arcs).size();
  // get count of non-node vertices
  var internalVertexCount = MapShaper.countInteriorVertices(arcs);
};

MapShaper.countInteriorVertices = function(arcs) {
  var count = 0;
  arcs.forEach2(function(i, n) {
    if (n > 2) {
      count += n - 2;
    }
  });
  return count;
};




// Convert a string containing delimited text data into a dataset object
MapShaper.importDelim = function(str, opts) {
  var delim = MapShaper.guessDelimiter(str);
  return {
    layers: [{
      data: MapShaper.importDelimTable(str, delim, opts)
    }],
    info: {
      input_delimiter: delim
    }
  };
};

MapShaper.importDelimTable = function(str, delim, opts) {
  var records = require("./lib/d3/d3-dsv.js").dsv(delim).parse(str);
  if (records.length === 0) {
    stop("[dsv] Unable to read any records");
  }
  MapShaper.adjustRecordTypes(records, opts && opts.field_types);
  return new DataTable(records);
};

MapShaper.supportedDelimiters = ['|', '\t', ',', ';'];

MapShaper.isSupportedDelimiter = function(d) {
  return utils.contains(MapShaper.supportedDelimiters, d);
};

MapShaper.guessDelimiter = function(content) {
  return utils.find(MapShaper.supportedDelimiters, function(delim) {
    var rxp = MapShaper.getDelimiterRxp(delim);
    return rxp.test(content);
  }) || ',';
};

// Get RegExp to test for a delimiter before first line break of a string
// Assumes that the first line does not contain alternate delim chars (this will
// be true if the first line has field headers composed of word characters).
MapShaper.getDelimiterRxp = function(delim) {
  var rxp = "^[^\\n\\r]+" + utils.regexEscape(delim);
  return new RegExp(rxp);
};

// Detect and convert data types of data from csv files.
// TODO: decide how to handle records with inconstent properties. Mapshaper
//    currently assumes tabular data
// @fieldList (optional) array of field names with type hints; may contain
//    duplicate names with inconsistent type hints.
MapShaper.adjustRecordTypes = function(records, fieldList) {
  var hintIndex = {},
      fields = Object.keys(records[0] || []),
      type;
  if (fieldList) {
    // parse optional type hints
    MapShaper.parseFieldHeaders(fieldList, hintIndex);
  }
  fields.forEach(function(key) {
    type = hintIndex[key] || MapShaper.detectConversionType(key, records);
    if (type == 'number') {
      MapShaper.convertDataField(records, key, utils.parseNumber);
    } else if (type == 'string') {
      MapShaper.convertDataField(records, key, utils.parseString);
    }
  });
};

MapShaper.convertDataField = function(records, name, f) {
  for (var i=0, n=records.length; i<n; i++) {
    records[i][name] = f(records[i][name]);
  }
};

// Returns 'string', 'number' or null
// Detection is based on value of first non-empty record
MapShaper.detectConversionType = function(name, records) {
  var type = null, val;
  for (var i=0, n=records.length; i<n; i++) {
    val = records[i][name];
    if (!!val && utils.isString(val)) {
      type = utils.stringIsNumeric(val) ? 'number' : 'string';
      break;
    }
  }
  return type;
};

// Accept a type hint from a header like "FIPS:str"
// Return standard type name (number|string) or null if hint is not recognized
MapShaper.validateFieldType = function(hint) {
  var str = hint.toLowerCase(),
      type = null;
  if (str[0] == 'n') {
    type = 'number';
  } else if (str[0] == 's') {
    type = 'string';
  }
  return type;
};

MapShaper.removeTypeHints = function(arr) {
  return MapShaper.parseFieldHeaders(arr, {});
};

// Look for type hints in array of field headers
// return index of field types
// modify @fields to remove type hints
//
MapShaper.parseFieldHeaders = function(fields, index) {
  var parsed = fields.map(function(raw) {
    var parts, name, type;
    if (raw.indexOf(':') != -1) {
      parts = raw.split(':');
      name = parts[0];
      type = MapShaper.validateFieldType(parts[1]);
      if (!type) {
        message("Invalid type hint (expected :str or :num) [" + raw + "]");
      }
    } else if (raw[0] === '+') { // d3-style type hint: unary plus
      name = raw.substr(1);
      type = 'number';
    } else {
      name = raw;
    }
    if (type) {
      index[name] = type;
    }
    return name;
  });
  return parsed;
};

utils.stringIsNumeric = function(str) {
  var parsed = utils.parseNumber(str);
  // exclude values like '300 E'
  return !isNaN(parsed) && parsed == Number(utils.cleanNumericString(str));
};

// Remove comma separators from strings
// TODO: accept European-style numbers?
utils.cleanNumericString = function(raw) {
  return String(raw).replace(/,/g, '');
};

// Assume: @raw is string, undefined or null
utils.parseString = function(raw) {
  return raw ? raw : "";
};

// Assume: @raw is string, undefined or null
// Use null instead of NaN for unparsable values
// (in part because if NaN is used, empty strings get converted to "NaN"
// when re-exported).
utils.parseNumber = function(raw) {
  var parsed = raw ? parseFloat(utils.cleanNumericString(raw)) : NaN;
  return isNaN(parsed) ? null : parsed;
};





api.joinPointsToPolygons = function(targetLyr, arcs, pointLyr, opts) {
  // TODO: copy points that can't be joined to a new layer
  var joinFunction = MapShaper.getPolygonToPointsFunction(targetLyr, arcs, pointLyr, opts);
  MapShaper.prepJoinLayers(targetLyr, pointLyr);
  MapShaper.joinTables(targetLyr.data, pointLyr.data, joinFunction, opts);
};

api.joinPolygonsToPoints = function(targetLyr, polygonLyr, arcs, opts) {
  var joinFunction = MapShaper.getPointToPolygonFunction(targetLyr, polygonLyr, arcs, opts);
  MapShaper.prepJoinLayers(targetLyr, polygonLyr);
  MapShaper.joinTables(targetLyr.data, polygonLyr.data, joinFunction, opts);
};

MapShaper.prepJoinLayers = function(targetLyr, srcLyr) {
  if (!targetLyr.data) {
    // create an empty data table if target layer is missing attributes
    targetLyr.data = new DataTable(targetLyr.shapes.length);
  }
  if (!srcLyr.data) {
    stop("[join] Can't join a layer that is missing attribute data");
  }
};

MapShaper.getPolygonToPointsFunction = function(polygonLyr, arcs, pointLyr, opts) {
  var joinFunction = MapShaper.getPointToPolygonFunction(pointLyr, polygonLyr, arcs, opts);
  var index = [];
  var hit, polygonId;
  for (var i=0, n=pointLyr.shapes.length; i<n; i++) {
    hit = joinFunction(i);
    if (hit) {
      polygonId = hit[0]; // TODO: handle multiple hits
      if (polygonId in index) {
        index[polygonId].push(i);
      } else {
        index[polygonId] = [i];
      }
    }
  }
  // @i id of a polygon feature
  return function(i) {
    return index[i] || null;
  };
};

MapShaper.getPointToPolygonFunction = function(pointLyr, polygonLyr, arcs, opts) {
  var index = new PathIndex(polygonLyr.shapes, arcs),
      points = pointLyr.shapes;

  // @i id of a point feature
  return function(i) {
    var shp = points[i],
        shpId = -1;
    if (shp) {
      // TODO: handle multiple hits
      shpId = index.findEnclosingShape(shp[0]);
    }
    return shpId == -1 ? null : [shpId];
  };
};




api.join = function(targetLyr, dataset, opts) {
  var src, srcLyr, srcType, targetType;
  if (opts.keys) {
    // join using data in attribute fields
    if (opts.keys.length != 2) {
      stop("[join] Expected two key fields: a target field and a source field");
    }
    src = MapShaper.getJoinTable(dataset, opts);
    api.joinAttributesToFeatures(targetLyr, src, opts);
  } else {
    // spatial join
    src = MapShaper.getJoinData(dataset, opts);
    if (!src) {
      stop("[join] Missing a joinable data source");
    }
    srcLyr = src.layers[0];
    srcType = srcLyr.geometry_type;
    targetType = targetLyr.geometry_type;
    if (srcType == 'point' && targetType == 'polygon') {
      api.joinPointsToPolygons(targetLyr, dataset.arcs, srcLyr, opts);
    } else if (srcType == 'polygon' && targetType == 'point') {
      api.joinPolygonsToPoints(targetLyr, srcLyr, src.arcs, opts);
    } else {
      stop(utils.format("[join] Unable to join %s geometry to %s geometry",
          srcType || 'null', targetType || 'null'));
    }
  }
};

// Get a DataTable to join, either from a current layer or from a file.
MapShaper.getJoinTable = function(dataset, opts) {
  var layers = MapShaper.findMatchingLayers(dataset.layers, opts.source),
      table;
  if (layers.length > 0) {
    table = layers[0].data;
  } else {
    table = api.importJoinTable(opts.source, opts);
  }
  return table;
};

// Get a dataset containing a source layer to join
// TODO: remove duplication with getJoinTable()
MapShaper.getJoinData = function(dataset, opts) {
  var layers = MapShaper.findMatchingLayers(dataset.layers, opts.source);
  if (!layers.length) {
    dataset = api.importFile(opts.source, opts);
    layers = dataset.layers;
  }
  return layers.length ? {arcs: dataset.arcs, layers: [layers[0]]} : null;
};

api.importJoinTable = function(file, opts) {
  var fieldsWithTypeHints = [];
  if (opts.keys) {
    fieldsWithTypeHints.push(opts.keys[1]);
  }
  if (opts.fields) {
    fieldsWithTypeHints = fieldsWithTypeHints.concat(opts.fields);
  }
  if (opts.field_types) {
    fieldsWithTypeHints = fieldsWithTypeHints.concat(opts.field_types);
  }
  var importOpts = utils.defaults({field_types: fieldsWithTypeHints}, opts);
  return api.importDataTable(file, importOpts);
};

api.joinAttributesToFeatures = function(lyr, srcTable, opts) {
  var keys = MapShaper.removeTypeHints(opts.keys),
      destKey = keys[0],
      srcKey = keys[1],
      destTable = lyr.data,
      // exclude source key field from join unless explicitly listed
      joinFields = opts.fields || utils.difference(srcTable.getFields(), [srcKey]),
      joinFunction = MapShaper.getJoinByKey(destTable, destKey, srcTable, srcKey);

  opts = utils.defaults({fields: joinFields}, opts);
  MapShaper.joinTables(destTable, srcTable, joinFunction, opts);
};

MapShaper.joinTables = function(dest, src, join, opts) {
  var srcRecords = src.getRecords(),
      destRecords = dest.getRecords(),
      joinFields = MapShaper.getFieldsToJoin(dest, src, opts),
      sumFields = opts.sum_fields || [],
      copyFields = utils.difference(joinFields, sumFields),
      countField = MapShaper.getCountFieldName(dest.getFields()),
      addCountField = sumFields.length > 0, // add a count field if we're aggregating records
      joinCounts = new Uint32Array(srcRecords.length),
      matchCount = 0,
      collisionCount = 0,
      srcRec, srcId, destRec, joinIds, joins, count, filter;

  if (opts.where) {
    filter = MapShaper.getJoinFilter(src, opts.where);
  }

  // join source records to target records
  for (var i=0, n=destRecords.length; i<n; i++) {
    destRec = destRecords[i];
    joins = join(i);
    count = 0;
    for (var j=0, m=joins ? joins.length : 0; j<m; j++) {
      srcId = joins[j];
      if (filter && !filter(srcId)) {
        continue;
      }
      srcRec = srcRecords[srcId];
      if (copyFields.length > 0) {
        if (count === 0) {
          // only copying the first match
          MapShaper.joinByCopy(destRec, srcRec, copyFields);
        } else {
          collisionCount++;
        }
      }
      if (sumFields.length > 0) {
        MapShaper.joinBySum(destRec, srcRec, sumFields);
      }
      joinCounts[srcId]++;
      count++;
    }
    if (count > 0) {
      matchCount++;
    } else if (destRec) {
      // Unmatched records records get null/empty values
      MapShaper.updateUnmatchedRecord(destRec, copyFields, sumFields);
    }
    if (addCountField) {
      destRec[countField] = count;
    }
  }
  if (matchCount === 0) {
    stop("[join] No records could be joinCount");
  }
  MapShaper.printJoinMessage(matchCount, destRecords.length,
      MapShaper.countJoins(joinCounts), srcRecords.length, collisionCount);
};

MapShaper.countJoins = function(counts) {
  var joinCount = 0;
  for (var i=0, n=counts.length; i<n; i++) {
    if (counts[i] > 0) {
      joinCount++;
    }
  }
  return joinCount;
};

MapShaper.updateUnmatchedRecord = function(rec, copyFields, sumFields) {
  MapShaper.joinByCopy(rec, {}, copyFields);
  MapShaper.joinBySum(rec, {}, sumFields);
};

MapShaper.getCountFieldName = function(fields) {
  var uniq = MapShaper.getUniqFieldNames(fields.concat("joins"));
  return uniq.pop();
};

MapShaper.joinByCopy = function(dest, src, fields) {
  var f;
  for (var i=0, n=fields.length; i<n; i++) {
    // dest[fields[i]] = src[fields[i]];
    // Use null when the source record is missing an expected value
    // TODO: think some more about whether this is desirable
    f = fields[i];
    dest[f] = Object.prototype.hasOwnProperty.call(src, f) ? src[f] : null;
  }
};

MapShaper.joinBySum = function(dest, src, fields) {
  var f;
  for (var j=0; j<fields.length; j++) {
    f = fields[j];
    dest[f] = (dest[f] || 0) + (src[f] || 0);
  }
};

MapShaper.printJoinMessage = function(matches, n, joins, m, collisions) {
  // TODO: add tip for generating layer containing unmatched records, when
  // this option is implemented.
  message(utils.format("[join] Joined %'d data record%s", joins, utils.pluralSuffix(joins)));
  if (matches < n) {
    message(utils.format('[join] %d/%d target records received no data', n-matches, n));
  }
  if (joins < m) {
    message(utils.format("[join] %d/%d source records could not be joined", m-joins, m));
  }
  if (collisions > 0) {
    message(utils.format("[join] %'d collision%s occured; data was copied from the first matching source record",
      collisions, utils.pluralSuffix(collisions)));
  }
};

MapShaper.getFieldsToJoin = function(destTable, srcTable, opts) {
  var joinFields;
  if (opts.fields) {
    joinFields = MapShaper.removeTypeHints(opts.fields);
  } else {
    // If a list of fields to join is not given, try to join all the
    // source fields except the key field.
    joinFields = srcTable.getFields();
  }
  if (!opts.force) {
    // only overwrite existing fields if the "force" option is set.
    joinFields = utils.difference(joinFields, destTable.getFields());
  }
  return joinFields;
};

// Return a function for translating a target id to an array of source ids based on values
// of two key fields.
MapShaper.getJoinByKey = function(dest, destKey, src, srcKey) {
  var destRecords = dest.getRecords();
  var index = MapShaper.createTableIndex(src.getRecords(), srcKey);
  if (src.fieldExists(srcKey) === false) {
    stop("[join] External table is missing a field named:", srcKey);
  }
  if (!dest || !dest.fieldExists(destKey)) {
    stop("[join] Target layer is missing key field:", destKey);
  }
  return function(i) {
    var destRec = destRecords[i],
        val = destRec && destRec[destKey],
        retn = null;
    if (destRec && val in index) {
      retn = index[val];
    }
    return retn;
  };
};

MapShaper.getJoinFilter = function(data, exp) {
  var test =  MapShaper.compileFeatureExpression(exp, {data: data}, null);
  return function(i) {
    var retn = test(i);
    if (retn !== true && retn !== false) {
      stop('[join] "where" expression must return true or false');
    }
    return retn;
  };
};

MapShaper.createTableIndex = function(records, f) {
  var index = {}, rec, key;
  for (var i=0, n=records.length; i<n; i++) {
    rec = records[i];
    key = rec[f];
    if (key in index) {
      index[key].push(i);
    } else {
      index[key] = [i];
    }
  }
  return index;
};




api.keepEveryPolygon =
MapShaper.keepEveryPolygon = function(arcData, layers) {
  T.start();
  layers.forEach(function(lyr) {
    if (lyr.geometry_type == 'polygon') {
      MapShaper.protectLayerShapes(arcData, lyr.shapes);
    }
  });
  T.stop("Protect shapes");
};

MapShaper.protectLayerShapes = function(arcData, shapes) {
  shapes.forEach(function(shape) {
    MapShaper.protectShape(arcData, shape);
  });
};

// Protect a single shape from complete removal by simplification
// @arcData an ArcCollection
// @shape an array containing one or more arrays of arc ids, or null if null shape
//
MapShaper.protectShape = function(arcData, shape) {
  var maxArea = 0,
      arcCount = shape ? shape.length : 0,
      maxRing, area;
  // Find ring with largest bounding box
  for (var i=0; i<arcCount; i++) {
    area = arcData.getSimpleShapeBounds(shape[i]).area();
    if (area > maxArea) {
      maxRing = shape[i];
      maxArea = area;
    }
  }

  if (!maxRing || maxRing.length === 0) {
    // invald shape
    verbose("[protectShape()] Invalid shape:", shape);
  } else if (maxRing.length == 1) {
    MapShaper.protectIslandRing(arcData, maxRing);
  } else {
    MapShaper.protectMultiRing(arcData, maxRing);
  }
};

// Add two vertices to the ring to form a triangle.
// Assuming that this will inflate the ring.
// Consider using the function for multi-arc rings, which
//   calculates ring area...
MapShaper.protectIslandRing = function(arcData, ring) {
  var added = MapShaper.lockMaxThreshold(arcData, ring);
  if (added == 1) {
    added += MapShaper.lockMaxThreshold(arcData, ring);
  }
  if (added < 2) verbose("[protectIslandRing()] Failed on ring:", ring);
};

MapShaper.protectMultiRing = function(arcData, ring) {
  var zlim = arcData.getRetainedInterval(),
      minArea = 0, // 0.00000001, // Need to handle rounding error?
      area, added;
  arcData.setRetainedInterval(Infinity);
  area = geom.getPlanarPathArea(ring, arcData);
  while (area <= minArea) {
    added = MapShaper.lockMaxThreshold(arcData, ring);
    if (added === 0) {
      verbose("[protectMultiRing()] Failed on ring:", ring);
      break;
    }
    area = geom.getPlanarPathArea(ring, arcData);
  }
  arcData.setRetainedInterval(zlim);
};

// Protect the vertex or vertices with the largest non-infinite
// removal threshold in a ring.
//
MapShaper.lockMaxThreshold = function(arcData, ring) {
  var targZ = 0,
      targArcId,
      raw = arcData.getVertexData(),
      arcId, id, z,
      start, end;

  for (var i=0; i<ring.length; i++) {
    arcId = ring[i];
    if (arcId < 0) arcId = ~arcId;
    start = raw.ii[arcId];
    end = start + raw.nn[arcId] - 1;
    id = MapShaper.findNextRemovableVertex(raw.zz, Infinity, start, end);
    if (id == -1) continue;
    z = raw.zz[id];
    if (z > targZ) {
      targZ = z;
      targArcId = arcId;
    }
  }
  if (targZ > 0) {
    // There may be more than one vertex with the target Z value; lock them all.
    start = raw.ii[targArcId];
    end = start + raw.nn[targArcId] - 1;
    return MapShaper.replaceInArray(raw.zz, targZ, Infinity, start, end);
  }
  return 0;
};

MapShaper.replaceInArray = function(zz, value, replacement, start, end) {
  var count = 0;
  for (var i=start; i<=end; i++) {
    if (zz[i] === value) {
      zz[i] = replacement;
      count++;
    }
  }
  return count;
};




// WORK IN PROGRESS
// Remove 'cuts' in an unprojected dataset at the antemeridian and poles.
// This will be useful when generating rotated projections.
//
api.stitch = function(dataset) {
  var arcs = dataset.arcs,
      edgeArcs, dissolver, nodes;
  if (!arcs || arcs.isPlanar()) {
    error("[stitch] Requires lat-lng dataset");
  }
  if (!MapShaper.snapEdgeArcs(arcs)) {
    return;
  }
  nodes = MapShaper.divideArcs(dataset);
  // console.log(arcs.toArray())

  dissolver = MapShaper.getPolygonDissolver(nodes, !!'spherical');
  dataset.layers.forEach(function(lyr) {
    if (lyr.geometry_type != 'polygon') return;
    var shapes = lyr.shapes,
        edgeShapeIds = MapShaper.findEdgeShapes(shapes, arcs);
    edgeShapeIds.forEach(function(i) {
      shapes[i] = dissolver(shapes[i]);
    });
  });
};

// TODO: test with 'wrapped' datasets
MapShaper.findEdgeArcs = function(arcs) {
  var bbox = MapShaper.getWorldBounds(),
      ids = [];
  for (var i=0, n=arcs.size(); i<n; i++) {
    if (!arcs.arcIsContained(i, bbox)) {
      ids.push(i);
    }
  }
  return ids;
};

MapShaper.findEdgeShapes = function(shapes, arcs) {
  var arcIds = MapShaper.findEdgeArcs(arcs);
  return MapShaper.findShapesByArcId(shapes, arcIds, arcs.size());
};

// Snap arcs that either touch poles or prime meridian to 0 degrees longitude
// Return array of affected arc ids
MapShaper.snapEdgeArcs = function(arcs) {
  var data = arcs.getVertexData(),
      xx = data.xx,
      yy = data.yy,
      onEdge = false,
      e = 1e-10, // TODO: justify this...
      xmin = -180,
      xmax = 180,
      ymin = -90,
      ymax = 90,
      lat, lng;
  for (var i=0, n=xx.length; i<n; i++) {
    lat = yy[i];
    lng = xx[i];
    if (lng <= xmin + e || lng >= xmax - e) {
      onEdge = true;
      xx[i] = xmin;
      // console.log(">>> snapped lat:", lat, "lng:", lng, "to lng:", xmin);
    }
    if (lat <= ymin + e) {
      onEdge = true;
      yy[i] = ymin;
      xx[i] = xmin;
    } else if (lat >= ymax - e) {
      onEdge = true;
      yy[i] = ymax;
      xx[i] = xmin;
    }
  }
  return onEdge;
};




// Merge similar layers in a dataset, in-place
api.mergeLayers = function(layers) {
  var index = {},
      merged = [];

  // layers with same key can be merged
  function layerKey(lyr) {
    var key = lyr.geometry_type || '';
    if (lyr.data) {
      key += '~' + lyr.data.getFields().sort().join(',');
    }
    return key;
  }

  layers.forEach(function(lyr) {
    var key = layerKey(lyr),
        indexedLyr,
        records;
    if (key in index === false) {
      index[key] = lyr;
      merged.push(lyr);
    } else {
      indexedLyr = index[key];
      indexedLyr.name = MapShaper.mergeNames(indexedLyr.name, lyr.name);
      indexedLyr.shapes = indexedLyr.shapes.concat(lyr.shapes);
      if (indexedLyr.data) {
        records = indexedLyr.data.getRecords().concat(lyr.data.getRecords());
        indexedLyr.data = new DataTable(records);
      }
    }
  });

  if (merged.length >= 2) {
    stop("[merge-layers] Unable to merge " + (merged.length < layers.length ? "some " : "") + "layers. Geometry and data fields must be compatible.");
  }

  return merged;
};




MapShaper.mergeDatasets = function(arr) {
  var arcSources = [],
      arcCount = 0,
      mergedLayers = [],
      mergedArcs;

  arr.forEach(function(data) {
    var n = data.arcs ? data.arcs.size() : 0;
    if (n > 0) {
      arcSources.push(data.arcs);
    }
    data.layers.forEach(function(lyr) {
      if (lyr.geometry_type == 'polygon' || lyr.geometry_type == 'polyline') {
        // reindex arc ids
        MapShaper.forEachArcId(lyr.shapes, function(id) {
          return id < 0 ? id - arcCount : id + arcCount;
        });
      }
      mergedLayers.push(lyr);
    });
    arcCount += n;
  });

  mergedArcs = MapShaper.mergeArcs(arcSources);
  if (mergedArcs.size() != arcCount) {
    error("[mergeDatasets()] Arc indexing error");
  }

  return {
    arcs: mergedArcs,
    layers: mergedLayers
  };
};

MapShaper.mergeArcs = function(arr) {
  var dataArr = arr.map(function(arcs) {
    if (arcs.getRetainedInterval() > 0) {
      verbose("Baking-in simplification setting.");
      arcs.flatten();
    }
    return arcs.getVertexData();
  });
  var xx = utils.mergeArrays(utils.pluck(dataArr, 'xx'), Float64Array),
      yy = utils.mergeArrays(utils.pluck(dataArr, 'yy'), Float64Array),
      nn = utils.mergeArrays(utils.pluck(dataArr, 'nn'), Int32Array);

  return new ArcCollection(nn, xx, yy);
};

utils.countElements = function(arrays) {
  return arrays.reduce(function(memo, arr) {
    return memo + (arr.length || 0);
  }, 0);
};

utils.mergeArrays = function(arrays, TypedArr) {
  var size = utils.countElements(arrays),
      Arr = TypedArr || Array,
      merged = new Arr(size),
      offs = 0;
  arrays.forEach(function(src) {
    var n = src.length;
    for (var i = 0; i<n; i++) {
      merged[i + offs] = src[i];
    }
    offs += n;
  });
  return merged;
};




api.mergeFiles = function(files, opts) {
  var datasets = files.map(function(fname) {
    // import without topology or snapping
    var importOpts = utils.defaults({no_topology: true, auto_snap: false, snap_interval: null, files: [fname]}, opts);
    return api.importFile(fname, importOpts);
  });

  // Don't allow multiple input formats
  var formats = datasets.map(function(d) {
    return d.info.input_format;
  });
  if (utils.uniq(formats).length != 1) {
    stop("Importing files with different formats is not supported");
  }

  var merged = MapShaper.mergeDatasets(datasets);
  // kludge -- using info property of first dataset
  merged.info = datasets[0].info;
  merged.info.input_files = files;

  // Don't try to re-build topology of TopoJSON files
  // TODO: consider updating topology of TopoJSON files instead of concatenating arcs
  // (but problem of mismatched coordinates due to quantization in input files.)
  if (!opts.no_topology && merged.info.input_format != 'topojson') {
    // TODO: remove duplication with mapshaper-path-import.js; consider applying
    //   snapping option inside buildTopology()
    if (opts.auto_snap || opts.snap_interval) {
      T.start();
      MapShaper.snapCoords(merged.arcs, opts.snap_interval);
      T.stop("Snapping points");
    }

    api.buildTopology(merged);
  }

  if (opts.merge_files) {
    merged.layers = api.mergeLayers(merged.layers);
  }
  return merged;
};




api.createPointLayer = function(srcLyr, arcs, opts) {
  var destLyr = MapShaper.getOutputLayer(srcLyr, opts);
  destLyr.shapes = opts.x || opts.y ?
      MapShaper.pointsFromDataTable(srcLyr.data, opts) :
      MapShaper.pointsFromPolygons(srcLyr, arcs, opts);
  destLyr.geometry_type = 'point';

  var nulls = destLyr.shapes.reduce(function(sum, shp) {
    if (!shp) sum++;
    return sum;
  }, 0);

  if (nulls > 0) {
    message(utils.format('[points] %,d of %,d points are null', nulls, destLyr.shapes.length));
  }
  if (srcLyr.data) {
    destLyr.data = opts.no_replace ? srcLyr.data.clone() : srcLyr.data;
  }
  return destLyr;
};

MapShaper.pointsFromPolygons = function(lyr, arcs, opts) {
  if (lyr.geometry_type != "polygon") {
    stop("[points] Expected a polygon layer");
  }
  var func = opts.inner ? geom.findInteriorPoint : geom.getShapeCentroid;
  return lyr.shapes.map(function(shp) {
    var p = func(shp, arcs);
    return p ? [[p.x, p.y]] : null;
  });
};

MapShaper.pointsFromDataTable = function(data, opts) {
  if (!data) stop("[points] Layer is missing a data table");
  if (!opts.x || !opts.y || !data.fieldExists(opts.x) || !data.fieldExists(opts.y)) {
    stop("[points] Missing x,y data fields");
  }

  return data.getRecords().map(function(rec) {
    var x = rec[opts.x],
        y = rec[opts.y];
    if (!utils.isFiniteNumber(x) || !utils.isFiniteNumber(y)) {
      return null;
    }
    return [[x, y]];
  });

};




MapShaper.projectionIndex = {
  webmercator: WebMercator,
  mercator: Mercator,
  albers: AlbersEqualAreaConic,
  albersusa: AlbersNYT,
  albersnyt: AlbersNYT,
  lambertcc: LambertConformalConic,
  transversemercator: TransverseMercator,
  utm: UTM,
  winkeltripel: WinkelTripel,
  robinson: Robinson
};

var DEG2RAD = Math.PI / 180.0;

// @params (optional) array of decimal-degree params that should be present in opts
function initProj(proj, name, opts, params) {
  var base = {
    spherical: false, // Toggle for spherical / ellipsoidal formulas
    x0: 0,   // false easting (used by UTM and some other projections)
    y0: 0,   // false northing
    k0: 1,   // scale factor
    to_meter: 1,
    R: 6378137, // Earth radius / semi-major axis (spherical / ellipsoidal formulas)
    // E: flattening parameter for GRS80 ellipsoid (others not supported)
    E: 0.0818191908426214943348,

    projectLatLng: function(lat, lng, xy) {
      xy = xy || {};
      this.forward(lng * DEG2RAD, lat * DEG2RAD, xy);
      xy.x = (this.R * xy.x + this.x0) / this.to_meter;
      xy.y = (this.R * xy.y + this.y0) / this.to_meter;
      return xy;
    },
    unprojectXY: function(x, y, ll) {
      x = (x * this.to_meter - this.x0) / this.R;
      y = (y * this.to_meter - this.y0) / this.R;
      ll = ll || {};
      this.inverse(x , y, ll);
      ll.lat /= DEG2RAD;
      ll.lng /= DEG2RAD;
      return ll;
    },
    // Approximate the inverse ellipsoidal projection function when
    // the forward ellipsoidal formula and both spheroidal formulas are known.
    // (Many ellipsoidal inverse projections lack closed formulas and/or are a hassle to implement).
    // Accuracy depends on # of iterations, projection, etc.
    // n of 4 gives ~1e-10 degree accuracy with Lambert CC.
    inverseEllApprox: function(x, y, ll) {
      var xy = {};
      var dx = 0, dy = 0;
      var n = 4;
      while (true) {
        this.spherical = true;
        this.inverse(x + dx, y + dy, ll);
        this.spherical = false;
        if (!--n) break;
        this.forward(ll.lng, ll.lat, xy);
        dx += x - xy.x;
        dy += y - xy.y;
      }
    }
  };
  opts = utils.extend({}, opts); // make a copy, don't modify original param
  if (params) {
    // check for required decimal degree parameters and convert to radians
    params.forEach(function(param) {
      if (param in opts === false) {
        throw new Error('[' + name + '] Missing required parameter:', param);
      }
      opts[param] = opts[param] * DEG2RAD;
    });
  }
  utils.extend(proj, base, opts);
  proj.name = name;
  if (opts.units) {
    proj.to_meter = initProjUnits(opts.units);
  }
}

// Return multiplier for converting to meters
function initProjUnits(units) {
  units = units.toLowerCase().replace(/-_/g, '');
  var k = {
      meters: 1,
      feet: 0.3048,
      usfeet: 0.304800609601219 }[units];
  if (!k) {
    throw new Error("[proj] Unsupported units, use to_meter param:", units);
  }
  return 1 / k;
}

function WebMercator() {
  return new Mercator({spherical: true});
}

// Optional param: lng0 (in decimal degrees)
function Mercator(opts) {
  opts = utils.extend({lng0: 0}, opts);
  initProj(this, 'mercator', opts, ['lng0']);
  this.forward = function(lng, lat, xy) {
    xy.x = lng - this.lng0;
    if (!this.spherical) {
      xy.y = Math.log(Math.tan(Math.PI * 0.25 + lat * 0.5) *
        Math.pow((1 - this.E * Math.sin(lat)) / (1 + this.E * Math.sin(lat)), this.E * 0.5));
    } else {
      xy.y = Math.log(Math.tan(Math.PI * 0.25 + lat * 0.5));
    }
  };
  this.inverse = function(x, y, ll) {
    if (!this.spherical) {
      this.inverseEllApprox(x, y, ll);
    } else {
      ll.lng = x + this.lng0;
      ll.lat = Math.PI * 0.5 - 2 * Math.atan(Math.exp(-y));
    }
  };
}

function UTM(opts) {
  var m = /^([\d]+)([NS])$/.exec(opts.zone || "");
  if (!m) {
    throw new Error("[UTM] Expected a UTM zone parameter of the form: 17N");
  }
  var z = parseFloat(m[1]);
  var proj = new TransverseMercator({
    k0: 0.9996,
    lng0: z * 6 - 183,
    lat0: 0,
    x0: 500000,
    y0: m[2] == 'S' ? 1e7 : 0
  });
  return proj;
}

function TransverseMercator(opts) {
  initProj(this, 'transverse_mercator', opts, ['lat0', 'lng0']);
  var _m0 = calcTransMercM(this.lat0, this.E);
  this.forward = function(lng, lat, xy) {
    if (this.spherical) {
      var B = Math.cos(lat) * Math.sin(lng - this.lng0);
      xy.x = 0.5 * this.k0 * Math.log((1 + B) / (1 - B));
      xy.y = this.k0 * (Math.atan(Math.tan(lat) / Math.cos(lng - this.lng0)) - this.lat0);
    } else {
      var e2 = this.E * this.E,
          ep2 = e2 / (1 - e2),
          sinLat = Math.sin(lat),
          cosLat = Math.cos(lat),
          tanLat = Math.tan(lat),
          n = 1 / Math.sqrt(1 - e2 * sinLat * sinLat),
          t = tanLat * tanLat,
          c = ep2 * cosLat * cosLat,
          a = cosLat * (lng - this.lng0),
          a2 = a * a,
          m = calcTransMercM(lat, this.E);
      xy.x = this.k0 * n * (a + a * a2 / 6 * (1 - t + c) +
        a2 * a2 * a / 120 * (5 - 18 * t + t * t + 72 * c - 58 * ep2));
      xy.y = this.k0 * (m - _m0 + n * tanLat *
        (a2 / 2 + a2 * a2 / 24 * (5 - t + 9 * c + 4 * c * c)));
    }
  };
  this.inverse = function(x, y, ll) {
    if (this.spherical) {
      var D = y / this.k0 + this.lat0;
      ll.lat = Math.asin(Math.sin(D) / cosh(x / this.k0));
      ll.lng = this.lng0 + Math.atan(sinh(x / this.k0) / Math.cos(D));
    } else {
      this.inverseEllApprox(x, y, ll);
    }
  };
}

// Authalic sin
function sinh(x) {
  return (Math.exp(x) - Math.exp(-x)) * 0.5;
}

// Authalic cosine
function cosh(x) {
  return (Math.exp(x) + Math.exp(-x)) * 0.5;
}

function calcTransMercM(lat, e) {
  var e2 = e * e,
      e4 = e2 * e2,
      e6 = e4 * e2;
  return (lat * (1 - e2 / 4.0 - 3 * e4 / 64 - 5 * e6 / 256) -
    Math.sin(2 * lat) * (3 * e2 / 8 + 3 * e4 / 32 + 45 * e6 / 1024) +
    Math.sin(4 * lat) * (15 * e4 / 256 + 45 * e6 / 1024) -
    Math.sin(6 * lat) * (35 * e6 / 3072));
}

function AlbersNYT(opts) {
  var lambert = new LambertConformalConic({lng0:-96, lat1:33, lat2:45, lat0:39, spherical: true});
  return new MixedProjection(new AlbersUSA(opts))
    .addFrame(lambert, {lat:63, lng:-152}, {lat:27, lng:-115}, 6e6, 3e6, 0.31, 29.2)  // AK
    .addFrame(lambert, {lat:20.9, lng:-157}, {lat:28.2, lng:-106.6}, 3e6, 5e6, 0.9, 40); // HI
}

function AlbersUSA(opts) {
  return new AlbersEqualAreaConic(utils.extend({lng0:-96, lat1:29.5, lat2:45.5, lat0:37.5}, opts));
}

/*
function LambertUSA() {
  return new LambertConformalConic({lng0:-96, lat1:33, lat2:45, lat0:39});
}
*/

// Parameters (in decimal degrees):
//   lng0  Reference longitude
//   lat0  Reference latitude
//   lat1  First standard parallel
//   lat2  Second standard parallel
function AlbersEqualAreaConic(opts) {
  initProj(this, 'albers', opts, ['lat0', 'lat1', 'lat2', 'lng0']);
  var E = this.E;
  var cosLat1 = Math.cos(this.lat1),
      sinLat1 = Math.sin(this.lat1),
      _sphN = 0.5 * (sinLat1 + Math.sin(this.lat2)),
      _sphC = cosLat1 * cosLat1 + 2.0 * _sphN * sinLat1,
      _sphRho0 = Math.sqrt(_sphC - 2.0 * _sphN * Math.sin(this.lat0)) / _sphN;

  var m1 = calcAlbersMell(E, this.lat1),
      m2 = calcAlbersMell(E, this.lat2),
      q0 = calcAlbersQell(E, this.lat0),
      q1 = calcAlbersQell(E, this.lat1),
      q2 = calcAlbersQell(E, this.lat2),
      _ellN = (m1 * m1 - m2 * m2) / (q2 - q1),
      _ellC = m1 * m1 + _ellN * q1,
      _ellRho0 = Math.sqrt(_ellC - _ellN * q0) / _ellN,
      _ellAuthConst = 1 - (1 - E * E) / (2 * E) * Math.log((1 - E) / (1 + E));

  this.forward = function(lng, lat, xy) {
    var rho, theta, q;
    if (!this.spherical) {
      q = calcAlbersQell(E, lat);
      rho = Math.sqrt(_ellC - _ellN * q) / _ellN;
      theta = _ellN * (lng - this.lng0);
      xy.x = rho * Math.sin(theta);
      xy.y = _ellRho0 - rho * Math.cos(theta);
    } else {
      rho = Math.sqrt(_sphC - 2 * _sphN * Math.sin(lat)) / _sphN;
      theta = _sphN * (lng - this.lng0);
      xy.x = rho * Math.sin(theta);
      xy.y = _sphRho0 - rho * Math.cos(theta);
    }
  };

  this.inverse = function(x, y, ll) {
    var rho, theta, e2, e4, q, beta;
    if (!this.spherical) {
      theta = Math.atan(x / (_ellRho0 - y));
      ll.lng = this.lng0 + theta / _ellN;
      e2 = E * E;
      e4 = e2 * e2;
      rho = Math.sqrt(x * x + (_ellRho0 - y) * (_ellRho0 - y));
      q = (_ellC - rho * rho * _ellN * _ellN) / _ellN;
      beta = Math.asin(q / _ellAuthConst);
      ll.lat = beta + Math.sin(2 * beta) *
        (e2 / 3 + 31 * e4 / 180 + 517 * e4 * e2 / 5040) +
        Math.sin(4 * beta) * (23 * e4 / 360 + 251 * e4 * e2 / 3780) +
        Math.sin(6 * beta) * 761 * e4 * e2 / 45360;
    } else {
      rho = Math.sqrt(x * x + (_sphRho0 - y) * (_sphRho0 - y));
      theta = Math.atan(x / (_sphRho0 - y));
      ll.lat = Math.asin((_sphC - rho * rho * _sphN * _sphN) * 0.5 / _sphN);
      ll.lng = theta / _sphN + this.lng0;
    }
  };
}

function calcAlbersQell(e, lat) {
  var sinLat = Math.sin(lat);
  return (1 - e * e) * (sinLat / (1 - e * e * sinLat * sinLat) -
    0.5 / e * Math.log((1 - e * sinLat) / (1 + e * sinLat)));
}

function calcAlbersMell(e, lat) {
  var sinLat = Math.sin(lat);
  return Math.cos(lat) / Math.sqrt(1 - e * e * sinLat * sinLat);
}

// Parameters (in decimal degrees):
//   lng0  Reference longitude
//   lat0  Reference latitude
//   lat1  First standard parallel
//   lat2  Second standard parallel
function LambertConformalConic(opts) {
  initProj(this, 'lambertcc', opts, ['lat0', 'lat1', 'lat2', 'lng0']);
  var E = this.E;
  var _sphN = Math.log(Math.cos(this.lat1) / Math.cos(this.lat2)) /
    Math.log(Math.tan(Math.PI / 4.0 + this.lat2 / 2.0) /
    Math.tan(Math.PI / 4.0 + this.lat1 / 2.0));
  var _sphF = Math.cos(this.lat1) *
    Math.pow(Math.tan(Math.PI / 4.0 + this.lat1 / 2.0), _sphN) / _sphN;
  var _sphRho0 = _sphF /
    Math.pow(Math.tan(Math.PI / 4.0 + this.lat0 / 2.0), _sphN);
  var _ellN = (Math.log(calcLambertM(this.lat1, E)) -
    Math.log(calcLambertM(this.lat2, E))) /
    (Math.log(calcLambertT(this.lat1, E)) -
    Math.log(calcLambertT(this.lat2, E)));
  var _ellF = calcLambertM(this.lat1, E) / (_ellN *
    Math.pow(calcLambertT(this.lat1, E), _ellN));
  var _ellRho0 = _ellF *
    Math.pow(calcLambertT(this.lat0, E), _ellN);

  this.forward = function(lng, lat, xy) {
    var rho, theta;
    if (!this.spherical) {
      var t = calcLambertT(lat, E);
      rho = _ellF * Math.pow(t, _ellN);
      theta = _ellN * (lng - this.lng0);
      xy.x = rho * Math.sin(theta);
      xy.y = _ellRho0 - rho * Math.cos(theta);
    } else {
      rho = _sphF /
        Math.pow(Math.tan(Math.PI / 4 + lat / 2.0), _sphN);
      theta = _sphN * (lng - this.lng0);
      xy.x = rho * Math.sin(theta);
      xy.y = _sphRho0 - rho * Math.cos(theta);
    }
  };

  this.inverse = function(x, y, ll) {
    if (!this.spherical) {
      this.inverseEllApprox(x, y, ll);
    } else {
      var rho0 = _sphRho0;
      var rho = Math.sqrt(x * x + (rho0 - y) * (rho0 - y));
      if (_sphN < 0) {
        rho = -rho;
      }
      var theta = Math.atan(x / (rho0 - y));
      ll.lat = 2 * Math.atan(Math.pow(_sphF /
        rho, 1 / _sphN)) - 0.5 * Math.PI;
      ll.lng = theta / _sphN + this.lng0;
    }
  };
}

function calcLambertT(lat, e) {
  var sinLat = Math.sin(lat);
  return Math.tan(Math.PI / 4 - lat / 2) /
    Math.pow((1 - e * sinLat) / (1 + e * sinLat), e / 2);
}

function calcLambertM(lat, e) {
  var sinLat = Math.sin(lat);
  return Math.cos(lat) / Math.sqrt(1 - e * e * sinLat * sinLat);
}

function WinkelTripel() {
  initProj(this, 'winkel_tripel');
  this.forward = function(lng, lat, xy) {
    var lat0 = 50.4670 * DEG2RAD;
    var a = Math.acos( Math.cos(lat) * Math.cos(lng * 0.5));
    var sincAlpha = a === 0 ? 1 : Math.sin( a ) / a;
    xy.x = 0.5 * (lng * Math.cos(lat0) + 2 * Math.cos(lat) * Math.sin(0.5 * lng) / sincAlpha);
    xy.y = 0.5 * (lat + Math.sin(lat) / sincAlpha);
  };
}

function Robinson() {
  initProj(this, 'robinson');
  var FXC = 0.8487;
  var FYC = 1.3523;
  var xx = [
    1, -5.67239e-12, -7.15511e-05, 3.11028e-06,
    0.9986, -0.000482241, -2.4897e-05, -1.33094e-06,
    0.9954, -0.000831031, -4.4861e-05, -9.86588e-07,
    0.99, -0.00135363, -5.96598e-05, 3.67749e-06,
    0.9822, -0.00167442, -4.4975e-06, -5.72394e-06,
    0.973, -0.00214869, -9.03565e-05, 1.88767e-08,
    0.96, -0.00305084, -9.00732e-05, 1.64869e-06,
    0.9427, -0.00382792, -6.53428e-05, -2.61493e-06,
    0.9216, -0.00467747, -0.000104566, 4.8122e-06,
    0.8962, -0.00536222, -3.23834e-05, -5.43445e-06,
    0.8679, -0.00609364, -0.0001139, 3.32521e-06,
    0.835, -0.00698325, -6.40219e-05, 9.34582e-07,
    0.7986, -0.00755337, -5.00038e-05, 9.35532e-07,
    0.7597, -0.00798325, -3.59716e-05, -2.27604e-06,
    0.7186, -0.00851366, -7.0112e-05, -8.63072e-06,
    0.6732, -0.00986209, -0.000199572, 1.91978e-05,
    0.6213, -0.010418, 8.83948e-05, 6.24031e-06,
    0.5722, -0.00906601, 0.000181999, 6.24033e-06,
    0.5322, 0,0,0
  ];
  var yy = [
    0, 0.0124, 3.72529e-10, 1.15484e-09,
    0.062, 0.0124001, 1.76951e-08, -5.92321e-09,
    0.124, 0.0123998, -7.09668e-08, 2.25753e-08,
    0.186, 0.0124008, 2.66917e-07, -8.44523e-08,
    0.248, 0.0123971, -9.99682e-07, 3.15569e-07,
    0.31, 0.0124108, 3.73349e-06, -1.1779e-06,
    0.372, 0.0123598, -1.3935e-05, 4.39588e-06,
    0.434, 0.0125501, 5.20034e-05, -1.00051e-05,
    0.4968, 0.0123198, -9.80735e-05, 9.22397e-06,
    0.5571, 0.0120308, 4.02857e-05, -5.2901e-06,
    0.6176, 0.0120369, -3.90662e-05, 7.36117e-07,
    0.6769, 0.0117015, -2.80246e-05, -8.54283e-07,
    0.7346, 0.0113572, -4.08389e-05, -5.18524e-07,
    0.7903, 0.0109099, -4.86169e-05, -1.0718e-06,
    0.8435, 0.0103433, -6.46934e-05, 5.36384e-09,
    0.8936, 0.00969679, -6.46129e-05, -8.54894e-06,
    0.9394, 0.00840949, -0.000192847, -4.21023e-06,
    0.9761, 0.00616525, -0.000256001, -4.21021e-06,
    1,0,0,0
  ];
  this.forward = function(lng, lat, xy) {
    var absLat = Math.abs(lat),
        j = Math.min(Math.floor(absLat * 11.45915590261646417544), 17),
        dphi = (absLat - 0.08726646259971647884 * j) / DEG2RAD,
        sign = lat < 0 ? -1 : 1,
        i = j * 4;
    xy.x = (((dphi * xx[i+3] + xx[i+2]) * dphi + xx[i+1]) * dphi + xx[i]) * lng * FXC;
    xy.y = (((dphi * yy[i+3] + yy[i+2]) * dphi + yy[i+1]) * dphi + yy[i]) * FYC * sign;
  };
}

// A compound projection, consisting of a default projection and one or more rectangular frames
// that are reprojected and/or affine transformed.
// @proj Default projection.
function MixedProjection(proj) {
  var frames = [];
  // @proj2 projection to use.
  // @ctr1 {lat, lng} center of the frame contents.
  // @ctr2 {lat, lng} geo location to move the frame center
  // @frameWidth Width of the frame in base projection units
  // @frameHeight Height of the frame in base projection units
  // @scale Scale factor; 1 = no scaling.
  // @rotation Rotation in degrees; 0 = no rotation.
  this.addFrame = function(proj2, ctr1, ctr2, frameWidth, frameHeight, scale, rotation) {
    var xy1 = proj.projectLatLng(ctr1.lat, ctr1.lng);
    var xy2 = proj.projectLatLng(ctr2.lat, ctr2.lng);
    var bbox = [xy1.x - frameWidth * 0.5, xy1.y - frameHeight * 0.5, xy1.x + frameWidth * 0.5, xy1.y + frameHeight * 0.5];
    var m = new Matrix2D();
    m.rotate(rotation * DEG2RAD, xy1.x, xy1.y );
    m.scale(scale, scale);
    m.transformXY(xy1.x, xy1.y, xy1);
    m.translate(xy2.x - xy1.x, xy2.y - xy1.y);
    frames.push({
      bbox: bbox,
      matrix: m,
      projection: proj2
    });
    return this;
  };

  this.projectLatLng = function(lat, lng, xy) {
    var frame, bbox;
    xy = proj.projectLatLng(lat, lng, xy);
    for (var i=0, n=frames.length; i<n; i++) {
      frame = frames[i];
      bbox = frame.bbox;
      if (xy.x >= bbox[0] && xy.x <= bbox[2] && xy.y >= bbox[1] && xy.y <= bbox[3]) {
        frame.projection.projectLatLng(lat, lng, xy);
        frame.matrix.transformXY(xy.x, xy.y, xy);
        break;
      }
    }
    return xy;
  };

  // TODO: implement inverse projection for frames
  this.unprojectXY = function(x, y, ll) {
    return proj.unprojectXY.call(proj, x, y, ll);
  };
}

// A matrix class that supports affine transformations (scaling, translation, rotation).
// Elements:
//   a  c  tx
//   b  d  ty
//   0  0  1  (u v w are not used)
//
function Matrix2D() {
  this.a = 1;
  this.c = 0;
  this.tx = 0;
  this.b = 0;
  this.d = 1;
  this.ty = 0;
}

Matrix2D.prototype.transformXY = function(x, y, p) {
  p = p || {};
  p.x = x * this.a + y * this.c + this.tx;
  p.y = x * this.b + y * this.d + this.ty;
  return p;
};

Matrix2D.prototype.translate = function(dx, dy) {
  this.tx += dx;
  this.ty += dy;
};

Matrix2D.prototype.rotate = function(q, x, y) {
  var cos = Math.cos(q);
  var sin = Math.sin(q);
  x = x || 0;
  y = y || 0;
  this.a = cos;
  this.c = -sin;
  this.b = sin;
  this.d = cos;
  this.tx += x - x * cos + y * sin;
  this.ty += y - x * sin - y * cos;
};

Matrix2D.prototype.scale = function(sx, sy) {
  this.a *= sx;
  this.c *= sx;
  this.b *= sy;
  this.d *= sy;
};




MapShaper.editArcs = function(arcs, onPoint) {
  var nn2 = [],
      xx2 = [],
      yy2 = [],
      n;

  arcs.forEach(function(arc, i) {
    editArc(arc, onPoint);
  });
  arcs.updateVertexData(nn2, xx2, yy2);

  function append(p) {
    xx2.push(p.x);
    yy2.push(p.y);
    n++;
  }

  function editArc(arc, cb) {
    var x, y, xp, yp;
    var i = 0;
    n = 0;
    while (arc.hasNext()) {
      x = arc.x;
      y = arc.y;
      cb(append, x, y, xp, yp, i++);
      xp = x;
      yp = y;
    }
    if (n == 1) { // invalid arc len
      error("An invalid arc was created");
    }
    nn2.push(n);
  }
};




api.proj = function(dataset, opts) {
  var proj = MapShaper.getProjection(opts.projection, opts);
  if (!proj) {
    stop("[proj] Unknown projection:", opts.projection);
  }
  MapShaper.projectDataset(dataset, proj, opts);
};

MapShaper.getProjection = function(name, opts) {
  var f = MapShaper.projectionIndex[name.toLowerCase().replace(/-_ /g, '')];
  return f ? new f(opts) : null;
};

MapShaper.printProjections = function() {
  var names = Object.keys(MapShaper.projectionIndex);
  names.sort();
  names.forEach(function(n) {
    message(n);
  });
};

MapShaper.projectDataset = function(dataset, proj, opts) {
  dataset.layers.forEach(function(lyr) {
    if (MapShaper.layerHasPoints(lyr)) {
      MapShaper.projectPointLayer(lyr, proj);
    }
  });
  if (dataset.arcs) {
    if (opts.densify) {
      MapShaper.projectAndDensifyArcs(dataset.arcs, proj);
    } else {
      MapShaper.projectArcs(dataset.arcs, proj);
    }
  }
  if (dataset.info) {
    // Setting output crs to null: "If the value of CRS is null, no CRS can be assumed"
    // (by default, GeoJSON assumes WGS84)
    // source: http://geojson.org/geojson-spec.html#coordinate-reference-system-objects
    // TODO: create a valid GeoJSON crs object after projecting
    dataset.info.output_crs = null;
    dataset.info.output_prj = null;
  }
};

MapShaper.projectPointLayer = function(lyr, proj) {
  var xy = {x: 0, y: 0};
  MapShaper.forEachPoint(lyr, function(p) {
    proj.projectLatLng(p[1], p[0], xy);
    p[0] = xy.x;
    p[1] = xy.y;
  });
};

MapShaper.projectArcs = function(arcs, proj) {
  var data = arcs.getVertexData(),
      xx = data.xx,
      yy = data.yy,
      // old zz will not be optimal after reprojection; re-using it for now
      // to avoid error in web ui
      zz = data.zz,
      p = {x: 0, y: 0};
  if (arcs.isPlanar()) {
    stop("[proj] Only projection from lat-lng coordinates is supported");
  }
  for (var i=0, n=xx.length; i<n; i++) {
    proj.projectLatLng(yy[i], xx[i], p);
    xx[i] = p.x;
    yy[i] = p.y;
  }
  arcs.updateVertexData(data.nn, xx, yy, zz);
};

MapShaper.getDefaultDensifyInterval = function(arcs, proj) {
  var xy = arcs.getAvgSegment2(),
      bb = arcs.getBounds(),
      a = proj.projectLatLng(bb.centerY(), bb.centerX()),
      b = proj.projectLatLng(bb.centerY() + xy[1], bb.centerX());
  return distance2D(a.x, a.y, b.x, b.y);
};

// Interpolate points into a projected line segment if needed to prevent large
//   deviations from path of original unprojected segment.
// @points (optional) array of accumulated points
MapShaper.densifySegment = function(lng0, lat0, x0, y0, lng2, lat2, x2, y2, proj, interval, points) {
  // Find midpoint between two endpoints and project it (assumes longitude does
  // not wrap). TODO Consider bisecting along great circle path -- although this
  // would not be good for boundaries that follow line of constant latitude.
  var lng1 = (lng0 + lng2) / 2,
      lat1 = (lat0 + lat2) / 2,
      p = proj.projectLatLng(lat1, lng1),
      distSq = geom.pointSegDistSq(p.x, p.y, x0, y0, x2, y2); // sq displacement
  points = points || [];
  // Bisect current segment if the projected midpoint deviates from original
  //   segment by more than the @interval parameter.
  //   ... but don't bisect very small segments to prevent infinite recursion
  //   (e.g. if projection function is discontinuous)
  if (distSq > interval * interval && distance2D(lng0, lat0, lng2, lat2) > 0.01) {
    MapShaper.densifySegment(lng0, lat0, x0, y0, lng1, lat1, p.x, p.y, proj, interval, points);
    points.push(p);
    MapShaper.densifySegment(lng1, lat1, p.x, p.y, lng2, lat2, x2, y2, proj, interval, points);
  }
  return points;
};

MapShaper.projectAndDensifyArcs = function(arcs, proj) {
  var interval = MapShaper.getDefaultDensifyInterval(arcs, proj);
  var tmp = {x: 0, y: 0};
  MapShaper.editArcs(arcs, onPoint);

  function onPoint(append, lng, lat, prevLng, prevLat, i) {
    var p = tmp,
        prevX = p.x,
        prevY = p.y;
    proj.projectLatLng(lat, lng, p);
    // Try to densify longer segments (optimization)
    if (i > 0 && distanceSq(p.x, p.y, prevX, prevY) > interval * interval * 25) {
      MapShaper.densifySegment(prevLng, prevLat, prevX, prevY, lng, lat, p.x, p.y, proj, interval)
        .forEach(append);
    }
    append(p);
  }
};




api.renameLayers = function(layers, names) {
  var nameCount = names && names.length || 0;
  layers.forEach(function(lyr, i) {
    var name;
    if (nameCount === 0) {
      name = "layer" + (i + 1);
    } else {
      name = i < nameCount - 1 ? names[i] : names[nameCount - 1];
      if (nameCount < layers.length && i >= nameCount - 2) {
        name += i - nameCount + 2;
      }
    }
    lyr.name = name;
  });
};




MapShaper.Heap = Heap; // export for testing

// A minheap data structure used for computing Visvalingam simplification data.
//
function Heap() {
  var capacity = 0,
      itemsInHeap = 0,
      dataArr,
      heapArr,
      indexArr;

  this.init = function(values) {
    var i;
    dataArr = values;
    itemsInHeap = values.length;
    prepareHeap(itemsInHeap);
    for (i=0; i<itemsInHeap; i++) {
      insert(i, i);
    }
    for (i=(itemsInHeap-2) >> 1; i >= 0; i--) {
      downHeap(i);
    }
  };

  function prepareHeap(size) {
    if (size > capacity) {
      capacity = Math.ceil(size * 1.2);
      heapArr = new Int32Array(capacity);
      indexArr = new Int32Array(capacity);
    }
  }

  this.size = function() {
    return itemsInHeap;
  };

  // Update a single value and re-heap.
  this.updateValue = function(valId, val) {
    var heapIdx = indexArr[valId];
    dataArr[valId] = val;
    if (heapIdx < 0 || heapIdx >= itemsInHeap) {
      error("[heap] Out-of-range heap index.");
    }
    downHeap(upHeap(heapIdx));
  };

  this.testHeapOrder = function() {
    checkNode(0, -Infinity);
    return true;
  };

  // Return the idx of the lowest-value item in the heap
  //
  this.pop = function() {
    if (itemsInHeap <= 0) error("Tried to pop from an empty heap.");
    var minValId = heapArr[0],
        lastIdx = --itemsInHeap;
    if (itemsInHeap > 0) {
      insert(0, heapArr[lastIdx]); // copy last item in heap into root position
      downHeap(0);
    }
    return minValId;
  };

  // Associate a heap idx with the id of a value in valuesArr
  //
  function insert(heapIdx, valId) {
    indexArr[valId] = heapIdx;
    heapArr[heapIdx] = valId;
  }

  // Check that heap is ordered starting at a given node
  // (traverses heap recursively)
  //
  function checkNode(heapIdx, parentVal) {
    if (heapIdx >= itemsInHeap) {
      return;
    }
    var val = dataArr[heapArr[heapIdx]];
    if (parentVal > val) error("Heap is out-of-order");
    var childIdx = heapIdx * 2 + 1;
    checkNode(childIdx, val);
    checkNode(childIdx + 1, val);
  }

  function upHeap(currIdx) {
    var valId = heapArr[currIdx],
        currVal = dataArr[valId],
        parentIdx, parentValId;

    // Move item up in the heap until it's at the top or is heavier than its parent
    //
    while (currIdx > 0) {
      parentIdx = (currIdx - 1) >> 1; // integer division by two gives idx of parent
      parentValId = heapArr[parentIdx];
      if (dataArr[parentValId] <= currVal) {
        break;
      }
      // out-of-order; swap child && parent
      insert(currIdx, parentValId);
      insert(parentIdx, valId);
      currIdx = parentIdx;
    }
    return currIdx;
  }

  // Swap item at @idx with any lighter children
  function downHeap(startIdx) {
    var data = dataArr, heap = heapArr, n = itemsInHeap, // local vars, faster
        currIdx = startIdx,
        valId = heap[currIdx],
        currVal = data[valId],
        firstChildIdx = 2 * currIdx + 1,
        secondChildIdx, minChildIdx, childValId;

    while (firstChildIdx < n) {
      minChildIdx = firstChildIdx;
      secondChildIdx = firstChildIdx + 1;
      if (secondChildIdx < n && data[heap[firstChildIdx]] > data[heap[secondChildIdx]]) {
        minChildIdx = secondChildIdx;
      }
      childValId = heap[minChildIdx];
      if (currVal <= data[childValId]) {
        break;
      }
      insert(currIdx, childValId);
      insert(minChildIdx, valId);

      // descend in the heap:
      currIdx = minChildIdx;
      firstChildIdx = 2 * currIdx + 1;
    }
  }
}




var Visvalingam = {};

Visvalingam.getArcCalculator = function(metric, is3D) {
  var heap = new Heap(),
      prevBuf = MapShaper.expandoBuffer(Int32Array),
      nextBuf = MapShaper.expandoBuffer(Int32Array),
      calc = is3D ?
        function(b, c, d, xx, yy, zz) {
          return metric(xx[b], yy[b], zz[b], xx[c], yy[c], zz[c], xx[d], yy[d], zz[d]);
        } :
        function(b, c, d, xx, yy) {
          return metric(xx[b], yy[b], xx[c], yy[c], xx[d], yy[d]);
        };

  // Calculate Visvalingam simplification data for an arc
  // @kk (Float64Array|Array) Receives calculated simplification thresholds
  // @xx, @yy, (@zz) Buffers containing vertex coordinates
  return function calcVisvalingam(kk, xx, yy, zz) {
    var arcLen = kk.length,
        prevArr = prevBuf(arcLen),
        nextArr = nextBuf(arcLen),
        val, maxVal = -Infinity,
        b, c, d; // indexes of points along arc

    if (zz && !is3D) {
      error("[visvalingam] Received z-axis data for 2D simplification");
    } else if (!zz && is3D) {
      error("[visvalingam] Missing z-axis data for 3D simplification");
    } else if (kk.length > xx.length) {
      error("[visvalingam] Incompatible data arrays:", kk.length, xx.length);
    }

    // Initialize Visvalingam "effective area" values and references to
    //   prev/next points for each point in arc.
    for (c=0; c<arcLen; c++) {
      b = c-1;
      d = c+1;
      if (b < 0 || d >= arcLen) {
        val = Infinity; // endpoint maxVals
      } else {
        val = calc(b, c, d, xx, yy, zz);
      }
      kk[c] = val;
      nextArr[c] = d;
      prevArr[c] = b;
    }
    heap.init(kk);

    // Calculate removal thresholds for each internal point in the arc
    //
    while (heap.size() > 0) {
      c = heap.pop(); // Remove the point with the least effective area.
      val = kk[c];
      if (val === Infinity) {
        break;
      }
      if (val < maxVal) {
        // don't assign current point a lesser value than the last removed vertex
        kk[c] = maxVal;
      } else {
        maxVal = val;
      }

      // Recompute effective area of neighbors of the removed point.
      b = prevArr[c];
      d = nextArr[c];
      if (b > 0) {
        val = calc(prevArr[b], b, d, xx, yy, zz);
        heap.updateValue(b, val);
      }
      if (d < arcLen-1) {
        val = calc(b, d, nextArr[d], xx, yy, zz);
        heap.updateValue(d, val);
      }
      nextArr[b] = d;
      prevArr[d] = b;
    }
  };
};

Visvalingam.standardMetric = triangleArea;
Visvalingam.standardMetric3D = triangleArea3D;

Visvalingam.getWeightedMetric = function(opts) {
  var weight = Visvalingam.getWeightFunction(opts);
  return function(ax, ay, bx, by, cx, cy) {
    var area = triangleArea(ax, ay, bx, by, cx, cy),
        cos = cosine(ax, ay, bx, by, cx, cy);
    return weight(cos) * area;
  };
};

Visvalingam.getWeightedMetric3D = function(opts) {
  var weight = Visvalingam.getWeightFunction(opts);
  return function(ax, ay, az, bx, by, bz, cx, cy, cz) {
    var area = triangleArea3D(ax, ay, az, bx, by, bz, cx, cy, cz),
        cos = cosine3D(ax, ay, az, bx, by, bz, cx, cy, cz);
    return weight(cos) * area;
  };
};

Visvalingam.getWeightCoefficient = function(opts) {
  return opts && utils.isNumber(opts && opts.weighting) ? opts.weighting : 0.7;
};

// Get a parameterized version of Visvalingam.weight()
Visvalingam.getWeightFunction = function(opts) {
  var k = Visvalingam.getWeightCoefficient(opts);
  return function(cos) {
    return -cos * k + 1;
  };
};

// Weight triangle area by inverse cosine
// Standard weighting favors 90-deg angles; this curve peaks at 120 deg.
Visvalingam.weight = function(cos) {
  var k = 0.7;
  return -cos * k + 1;
};

Visvalingam.getEffectiveAreaSimplifier = function(use3D) {
  var metric = use3D ? Visvalingam.standardMetric3D : Visvalingam.standardMetric;
  return Visvalingam.getPathSimplifier(metric, use3D);
};

Visvalingam.getWeightedSimplifier = function(opts, use3D) {
  var metric = use3D ? Visvalingam.getWeightedMetric3D(opts) : Visvalingam.getWeightedMetric(opts);
  return Visvalingam.getPathSimplifier(metric, use3D);
};

Visvalingam.getPathSimplifier = function(metric, use3D) {
  return Visvalingam.scaledSimplify(Visvalingam.getArcCalculator(metric, use3D));
};

Visvalingam.scaledSimplify = function(f) {
  return function(kk, xx, yy, zz) {
    f(kk, xx, yy, zz);
    for (var i=1, n=kk.length - 1; i<n; i++) {
      // convert area metric to a linear equivalent
      kk[i] = Math.sqrt(kk[i]) * 0.65;
    }
  };
};




var DouglasPeucker = {};

DouglasPeucker.metricSq3D = geom.pointSegDistSq3D;
DouglasPeucker.metricSq = geom.pointSegDistSq;

// @dest array to contain point removal thresholds
// @xx, @yy arrays of x, y coords of a path
// @zz (optional) array of z coords for spherical simplification
//
DouglasPeucker.calcArcData = function(dest, xx, yy, zz) {
  var len = dest.length,
      useZ = !!zz;

  dest[0] = dest[len-1] = Infinity;
  if (len > 2) {
    procSegment(0, len-1, 1, Number.MAX_VALUE);
  }

  function procSegment(startIdx, endIdx, depth, distSqPrev) {
    // get endpoint coords
    var ax = xx[startIdx],
        ay = yy[startIdx],
        cx = xx[endIdx],
        cy = yy[endIdx],
        az, cz;
    if (useZ) {
      az = zz[startIdx];
      cz = zz[endIdx];
    }

    var maxDistSq = 0,
        maxIdx = 0,
        distSqLeft = 0,
        distSqRight = 0,
        distSq;

    for (var i=startIdx+1; i<endIdx; i++) {
      if (useZ) {
        distSq = DouglasPeucker.metricSq3D(xx[i], yy[i], zz[i], ax, ay, az, cx, cy, cz);
      } else {
        distSq = DouglasPeucker.metricSq(xx[i], yy[i], ax, ay, cx, cy);
      }

      if (distSq >= maxDistSq) {
        maxDistSq = distSq;
        maxIdx = i;
      }
    }

    // Case -- threshold of parent segment is less than threshold of curr segment
    // Curr max point is assigned parent's threshold, so parent is not removed
    // before child as simplification is increased.
    //
    if (distSqPrev < maxDistSq) {
      maxDistSq = distSqPrev;
    }

    if (maxIdx - startIdx > 1) {
      distSqLeft = procSegment(startIdx, maxIdx, depth+1, maxDistSq);
    }
    if (endIdx - maxIdx > 1) {
      distSqRight = procSegment(maxIdx, endIdx, depth+1, maxDistSq);
    }

    // Case -- max point of curr segment is highest-threshold point of an island polygon
    // Give point the same threshold as the next-highest point, to prevent
    // a 3-vertex degenerate ring.
    if (depth == 1 && ax == cx && ay == cy) {
      maxDistSq = Math.max(distSqLeft, distSqRight);
    }

    dest[maxIdx] =  Math.sqrt(maxDistSq);
    return maxDistSq;
  }
};




// Combine detection and repair for cli
//
api.findAndRepairIntersections = function(arcs) {
  T.start();
  var intersections = MapShaper.findSegmentIntersections(arcs),
      unfixable = MapShaper.repairIntersections(arcs, intersections),
      countPre = intersections.length,
      countPost = unfixable.length,
      countFixed = countPre > countPost ? countPre - countPost : 0,
      msg;
  T.stop('Find and repair intersections');
  if (countPre > 0) {
    msg = utils.format("[simplify] Repaired %'i intersection%s", countFixed,
        utils.pluralSuffix(countFixed));
    if (countPost > 0) {
      msg += utils.format("; %'i intersection%s could not be repaired", countPost,
          utils.pluralSuffix(countPost));
    }
    message(msg);
  }
};

// Try to resolve a collection of line-segment intersections by rolling
// back simplification along intersecting segments.
//
// Limitation of this method: it can't remove intersections that are present
// in the original dataset.
//
// @arcs ArcCollection object
// @intersections (Array) Output from MapShaper.findSegmentIntersections()
// Returns array of unresolved intersections, or empty array if none.
//
MapShaper.repairIntersections = function(arcs, intersections) {
  while (MapShaper.unwindIntersections(arcs, intersections) > 0) {
    intersections = MapShaper.findSegmentIntersections(arcs);
  }
  return intersections;
};

MapShaper.unwindIntersections = function(arcs, intersections) {
  var data = arcs.getVertexData(),
      zlim = arcs.getRetainedInterval(),
      changes = 0,
      loops = 0,
      replacements, queue, target, i;

  // create a queue of unwind targets
  queue = MapShaper.getUnwindTargets(intersections, zlim, data.zz);
  utils.sortOn(queue, 'z', !!"ascending");

  while (queue.length > 0) {
    target = queue.pop();
    // redetect unwind target, in case a previous unwind operation has changed things
    // TODO: don't redetect if target couldn't have been affected
    replacements = MapShaper.redetectIntersectionTarget(target, zlim, data.xx, data.yy, data.zz);
    if (replacements.length == 1) {
      replacements = MapShaper.unwindIntersection(replacements[0], zlim, data.zz);
      changes++;
    } else  {
      // either 0 or multiple intersections detected
    }

    for (i=0; i<replacements.length; i++) {
      MapShaper.insertUnwindTarget(queue, replacements[i]);
    }
  }
  if (++loops > 500000) {
    verbose("Caught an infinite loop at intersection:", target);
    return 0;
  }
  return changes;
};

MapShaper.getUnwindTargets = function(intersections, zlim, zz) {
  return intersections.reduce(function(memo, o) {
    var target = MapShaper.getUnwindTarget(o, zlim, zz);
    if (target !== null) {
      memo.push(target);
    }
    return memo;
  }, []);
};

// @o an intersection object
// returns null if no vertices can be added along both segments
// else returns an object with properties:
//   a: intersecting segment to be partitioned
//   b: intersecting segment to be retained
//   z: threshold value of one or more points along [a] to be re-added
MapShaper.getUnwindTarget = function(o, zlim, zz) {
  var ai = MapShaper.findNextRemovableVertex(zz, zlim, o.a[0], o.a[1]),
      bi = MapShaper.findNextRemovableVertex(zz, zlim, o.b[0], o.b[1]),
      targ;
  if (ai == -1 && bi == -1) {
    targ = null;
  } else if (bi == -1 || ai != -1 && zz[ai] > zz[bi]) {
    targ = {
      a: o.a,
      b: o.b,
      z: zz[ai]
    };
  } else {
    targ = {
      a: o.b,
      b: o.a,
      z: zz[bi]
    };
  }
  return targ;
};

// Insert an intersection into sorted position
MapShaper.insertUnwindTarget = function(arr, obj) {
  var ins = arr.length;
  while (ins > 0) {
    if (arr[ins-1].z <= obj.z) {
      break;
    }
    arr[ins] = arr[ins-1];
    ins--;
  }
  arr[ins] = obj;
};

// Partition one of two intersecting segments by setting the removal threshold
// of vertices indicated by @target equal to @zlim (the current simplification
// level of the ArcCollection)
MapShaper.unwindIntersection = function(target, zlim, zz) {
  var replacements = [];
  var start = target.a[0],
      end = target.a[1],
      z = target.z;
  for (var i = start + 1; i <= end; i++) {
    if (zz[i] == z || i == end) {
      replacements.push({
        a: [start, i],
        b: target.b,
        z: z
      });
      if (i != end) zz[i] = zlim;
      start = i;
    }
  }
  if (replacements.length < 2) error("Error in unwindIntersection()");
  return replacements;
};

MapShaper.redetectIntersectionTarget = function(targ, zlim, xx, yy, zz) {
  var segIds = MapShaper.getIntersectionCandidates(targ, zlim, xx, yy, zz);
  var intersections = MapShaper.intersectSegments(segIds, xx, yy);
  return MapShaper.getUnwindTargets(intersections, zlim, zz);
};

MapShaper.getIntersectionCandidates = function(o, zlim, xx, yy, zz) {
  var segIds = MapShaper.getSegmentVertices(o.a, zlim, xx, yy, zz);
  segIds = segIds.concat(MapShaper.getSegmentVertices(o.b, zlim, xx, yy, zz));
  return segIds;
};

// Get all segments defined by two endpoints and the vertices between
// them that are at or above the current simplification threshold.
// TODO: test intersections with identical start + end ids
MapShaper.getSegmentVertices = function(seg, zlim, xx, yy, zz) {
  var start, end, prev, ids = [];
  if (seg[0] <= seg[1]) {
    start = seg[0];
    end = seg[1];
  } else {
    start = seg[1];
    end = seg[0];
  }
  prev = start;
  for (var i=start+1; i<=end; i++) {
    if (zz[i] >= zlim) {
      if (xx[prev] < xx[i]) {
        ids.push(prev, i);
      } else {
        ids.push(i, prev);
      }
      prev = i;
    }
  }
  return ids;
};




MapShaper.calcSimplifyStats = function(arcs, use3D) {
  var distSq = use3D ? pointSegGeoDistSq : geom.pointSegDistSq,
      calcAngle = use3D ? geom.signedAngleSph : geom.signedAngle,
      removed = 0,
      retained = 0,
      collapsedRings = 0,
      max = 0,
      sum = 0,
      sumSq = 0,
      iprev = -1,
      jprev = -1,
      measures = [],
      angles = [],
      zz = arcs.getVertexData().zz,
      count, stats;

  arcs.forEachSegment(function(i, j, xx, yy) {
    var ax, ay, bx, by, d2, d, skipped, angle, tmp;
    ax = xx[i];
    ay = yy[i];
    bx = xx[j];
    by = yy[j];

    if (i == jprev) {
      angle = calcAngle(xx[iprev], yy[iprev], ax, ay, bx, by);
      if (angle > Math.PI) angle = 2 * Math.PI - angle;
      if (!isNaN(angle)) {
        angles.push(angle * 180 / Math.PI);
      }
    }
    iprev = i;
    jprev = j;

    if (zz[i] < Infinity) {
      retained++;
    }
    skipped = j - i - 1;
    if (skipped < 1) return;
    removed += skipped;

    if (ax == bx && ay == by) {
      collapsedRings++;
    } else {
      d2 = 0;
      while (++i < j) {
        tmp = distSq(xx[i], yy[i], ax, ay, bx, by);
        d2 = Math.max(d2, tmp);
      }
      sumSq += d2;
      d = Math.sqrt(d2);
      sum += d;
      measures.push(d);
      max = Math.max(max, d);
    }
  });

  function pointSegGeoDistSq(alng, alat, blng, blat, clng, clat) {
    var xx = [], yy = [], zz = [];
    geom.convLngLatToSph([alng, blng, clng], [alat, blat, clat], xx, yy, zz);
    return geom.pointSegDistSq3D(xx[0], yy[0], zz[0], xx[1], yy[1], zz[1],
          xx[2], yy[2], zz[2]);
  }

  stats = {
    angleMean: 0,
    displacementMean: 0,
    displacementMax: max,
    collapsedRings: collapsedRings,
    removed: removed,
    retained: retained,
    uniqueCount: MapShaper.countUniqueVertices(arcs),
    removableCount: removed + retained
  };

  if (angles.length > 0) {
    // stats.medianAngle = utils.findMedian(angles);
    stats.angleMean = utils.sum(angles) / angles.length;
    // stats.lt30 = utils.findRankByValue(angles, 30) / angles.length * 100;
    // stats.lt45 = utils.findRankByValue(angles, 45) / angles.length * 100;
    // stats.lt60 = utils.findRankByValue(angles, 60) / angles.length * 100;
    // stats.lt90 = utils.findRankByValue(angles, 90) / angles.length * 100;
    // stats.lt120 = utils.findRankByValue(angles, 120) / angles.length * 100;
    // stats.lt135 = utils.findRankByValue(angles, 135) / angles.length * 100;
    stats.angleQuartiles = [
      utils.findValueByPct(angles, 0.75),
      utils.findValueByPct(angles, 0.5),
      utils.findValueByPct(angles, 0.25)
    ];
  }

  if (measures.length > 0) {
    stats.displacementMean = sum / measures.length;
    // stats.median = utils.findMedian(measures);
    // stats.stdDev = Math.sqrt(sumSq / measures.length);
    stats.displacementQuartiles = [
      utils.findValueByPct(measures, 0.75),
      utils.findValueByPct(measures, 0.5),
      utils.findValueByPct(measures, 0.25)
    ];
  }
  return stats;
};

MapShaper.countUniqueVertices = function(arcs) {
  // TODO: exclude any zero-length arcs
  var endpoints = arcs.size() * 2;
  var nodes = new NodeCollection(arcs).size();
  return arcs.getPointCount() - endpoints + nodes;
};





MapShaper.getSimplifyMethodLabel = function(slug) {
  return {
    dp: "Ramer-Douglas-Peucker",
    visvalingam: "Visvalingam",
    weighted_visvalingam: "Weighted Visvalingam"
  }[slug] || "Unknown";
};

MapShaper.printSimplifyInfo = function(arcs, opts) {
  var method = MapShaper.getSimplifyMethod(opts);
  var name = MapShaper.getSimplifyMethodLabel(method);
  var spherical = MapShaper.useSphericalSimplify(arcs, opts);
  var stats = MapShaper.calcSimplifyStats(arcs, spherical);
  var pct1 = (stats.removed + stats.collapsedRings) / stats.uniqueCount || 0;
  var pct2 = stats.removed / stats.removableCount || 0;
  var aq = stats.angleQuartiles;
  var dq = stats.displacementQuartiles;
  var lines = ["Simplification statistics"];
  lines.push(utils.format("Method: %s (%s) %s", name, spherical ? 'spherical' : 'planar',
      method == 'weighted_visvalingam' ? '(weighting=' + Visvalingam.getWeightCoefficient(opts) + ')' : ''));
  lines.push(utils.format("Removed vertices: %,d", stats.removed + stats.collapsedRings));
  lines.push(utils.format("   %.1f% of %,d unique coordinate locations", pct1 * 100, stats.uniqueCount));
  lines.push(utils.format("   %.1f% of %,d filterable coordinate locations", pct2 * 100, stats.removableCount));
  lines.push(utils.format("Simplification interval: %.4f %s", arcs.getRetainedInterval(),
      spherical ? 'meters' : ''));
  lines.push(utils.format("Collapsed rings: %,d", stats.collapsedRings));
  lines.push("Displacement statistics");
  lines.push(utils.format("   Mean displacement: %.4f", stats.displacementMean));
  lines.push(utils.format("   Max displacement: %.4f", stats.displacementMax));
  lines.push(utils.format("   Quartiles: %.2f, %.2f, %.2f", dq[0], dq[1], dq[2]));
  lines.push("Vertex angle statistics");
  lines.push(utils.format("   Mean angle: %.2f degrees", stats.angleMean));
  // lines.push(utils.format("   Angles < 45: %.2f%", stats.lt45));
  lines.push(utils.format("   Quartiles: %.2f, %.2f, %.2f", aq[0], aq[1], aq[2]));

  message(lines.join('\n   '));
};




api.simplify = function(dataset, opts) {
  var arcs = dataset.arcs;
  if (!arcs) stop("[simplify] Missing path data");
  T.start();
  MapShaper.simplifyPaths(arcs, opts);

  if (utils.isNumber(opts.pct)) {
    arcs.setRetainedPct(opts.pct);
  } else if (utils.isNumber(opts.interval)) {
    arcs.setRetainedInterval(opts.interval);
  } else if (opts.resolution) {
    arcs.setRetainedInterval(MapShaper.calcSimplifyInterval(arcs, opts));
  } else {
    stop("[simplify] missing pct, interval or resolution parameter");
  }
  T.stop("Calculate simplification");

  if (opts.keep_shapes) {
    api.keepEveryPolygon(arcs, dataset.layers);
  }

  if (!opts.no_repair) {
    api.findAndRepairIntersections(arcs);
  }

  if (opts.stats) {
    MapShaper.printSimplifyInfo(arcs, opts);
  }
};

MapShaper.useSphericalSimplify = function(arcs, opts) {
  return !opts.cartesian && !arcs.isPlanar();
};

// Calculate simplification thresholds for each vertex of an arc collection
// (modifies @arcs ArcCollection in-place)
MapShaper.simplifyPaths = function(arcs, opts) {
  var use3D = MapShaper.useSphericalSimplify(arcs, opts);
  var method = MapShaper.getSimplifyMethod(opts);
  var simplifyPath = MapShaper.getSimplifyFunction(method, use3D, opts);
  arcs.setThresholds(new Float64Array(arcs.getPointCount())); // Create array to hold simplification data
  if (use3D) {
    MapShaper.simplifyPaths3D(arcs, simplifyPath);
    MapShaper.protectWorldEdges(arcs);
  } else {
    MapShaper.simplifyPaths2D(arcs, simplifyPath);
  }
};

MapShaper.simplifyPaths2D = function(arcs, simplify) {
  arcs.forEach3(function(xx, yy, kk, i) {
    simplify(kk, xx, yy);
  });
};

MapShaper.simplifyPaths3D = function(arcs, simplify) {
  var xbuf = MapShaper.expandoBuffer(Float64Array),
      ybuf = MapShaper.expandoBuffer(Float64Array),
      zbuf = MapShaper.expandoBuffer(Float64Array);
  arcs.forEach3(function(xx, yy, kk, i) {
    var n = xx.length,
        xx2 = xbuf(n),
        yy2 = ybuf(n),
        zz2 = zbuf(n);
    geom.convLngLatToSph(xx, yy, xx2, yy2, zz2);
    simplify(kk, xx2, yy2, zz2);
  });
};

MapShaper.getSimplifyMethod = function(opts) {
  var m = opts.method;
  if (!m || m == 'weighted' || m == 'visvalingam' && opts.weighting) {
    m =  'weighted_visvalingam';
  }
  return m;
};


MapShaper.getSimplifyFunction = function(method, use3D, opts) {
  var f;
  if (method == 'dp') {
    f = DouglasPeucker.calcArcData;
  } else if (method == 'visvalingam') {
    f = Visvalingam.getEffectiveAreaSimplifier(use3D);
  } else if (method == 'weighted_visvalingam') {
    f = Visvalingam.getWeightedSimplifier(opts, use3D);
  } else {
    stop('[simplify] Unsupported simplify method:', method);
  }
  return f;
};

// Protect polar coordinates and coordinates at the prime meridian from
// being removed before other points in a path.
// Assume: coordinates are in decimal degrees
//
MapShaper.protectWorldEdges = function(arcs) {
  // Need to handle coords with rounding errors:
  // -179.99999999999994 in test/test_data/ne/ne_110m_admin_0_scale_rank.shp
  // 180.00000000000003 in ne/ne_50m_admin_0_countries.shp
  var bb1 = MapShaper.getWorldBounds(1e-12),
      bb2 = arcs.getBounds().toArray();
  if (containsBounds(bb1, bb2) === true) return; // return if content doesn't reach edges
  arcs.forEach3(function(xx, yy, zz) {
    var maxZ = 0,
    x, y;
    for (var i=0, n=zz.length; i<n; i++) {
      x = xx[i];
      y = yy[i];
      if (x > bb1[2] || x < bb1[0] || y < bb1[1] || y > bb1[3]) {
        if (maxZ === 0) {
          maxZ = MapShaper.findMaxThreshold(zz);
        }
        if (zz[i] !== Infinity) { // don't override lock value
          zz[i] = maxZ;
        }
      }
    }
  });
};

// Return largest value in an array, ignoring Infinity (lock value)
//
MapShaper.findMaxThreshold = function(zz) {
  var z, maxZ = 0;
  for (var i=0, n=zz.length; i<n; i++) {
    z = zz[i];
    if (z > maxZ && z < Infinity) {
      maxZ = z;
    }
  }
  return maxZ;
};

MapShaper.parseSimplifyResolution = function(raw) {
  var parts, w, h;
  if (utils.isNumber(raw)) {
    w = raw;
    h = raw;
  }
  else if (utils.isString(raw)) {
    parts = raw.split('x');
    w = Number(parts[0]) || 0;
    h = parts.length == 2 ? Number(parts[1]) || 0 : w;
  }
  if (!(w >= 0 && h >= 0 && w + h > 0)) {
    stop("Invalid simplify resolution:", raw);
  }
  return [w, h]; // TODO: validate;
};

MapShaper.calcPlanarInterval = function(xres, yres, width, height) {
  var fitWidth = xres !== 0 && width / height > xres / yres || yres === 0;
  return fitWidth ? width / xres : height / yres;
};

// Calculate a simplification interval for unprojected data, given an output resolution
// (This is approximate, since we don't know how the data will be projected for display)
MapShaper.calcSphericalInterval = function(xres, yres, bounds) {
  // Using length of arc along parallel through center of bbox as content width
  // TODO: consider using great circle instead of parallel arc to calculate width
  //    (doesn't work if width of bbox is greater than 180deg)
  var width = geom.degreesToMeters(bounds.width()) * Math.cos(bounds.centerY() * geom.D2R);
  var height = geom.degreesToMeters(bounds.height());
  return MapShaper.calcPlanarInterval(xres, yres, width, height);
};

MapShaper.calcSimplifyInterval = function(arcs, opts) {
  var res, interval, bounds;
  if (opts.interval) {
    interval = opts.interval;
  } else if (opts.resolution) {
    res = MapShaper.parseSimplifyResolution(opts.resolution);
    bounds = arcs.getBounds();
    if (MapShaper.useSphericalSimplify(arcs, opts)) {
      interval = MapShaper.calcSphericalInterval(res[0], res[1], bounds);
    } else {
      interval = MapShaper.calcPlanarInterval(res[0], res[1], bounds.width(), bounds.height());
    }
    // scale interval to double the resolution (single-pixel resolution creates
    //  visible artefacts)
    interval *= 0.5;
  }
  return interval;
};




api.splitLayer = function(src, splitField, opts) {
  var lyr0 = opts && opts.no_replace ? MapShaper.copyLayer(src) : src,
      properties = lyr0.data ? lyr0.data.getRecords() : null,
      shapes = lyr0.shapes,
      index = {},
      splitLayers = [];

  if (splitField && (!properties || !lyr0.data.fieldExists(splitField))) {
    stop("[split] Missing attribute field:", splitField);
  }

  utils.repeat(MapShaper.getFeatureCount(lyr0), function(i) {
    var key = String(splitField ? properties[i][splitField] : i),
        lyr;

    if (key in index === false) {
      index[key] = splitLayers.length;
      lyr = utils.defaults({
        name: MapShaper.getSplitLayerName(lyr0.name, key),
        data: properties ? new DataTable() : null,
        shapes: shapes ? [] : null
      }, lyr0);
      splitLayers.push(lyr);
    } else {
      lyr = splitLayers[index[key]];
    }
    if (shapes) {
      lyr.shapes.push(shapes[i]);
    }
    if (properties) {
      lyr.data.getRecords().push(properties[i]);
    }
  });
  return splitLayers;
};

MapShaper.getSplitLayerName = function(base, key) {
  return (base || 'split') + '-' + (key || '');
};




// Split the shapes in a layer according to a grid
// Return array of layers and an index with the bounding box of each cell
//
api.splitLayerOnGrid = function(lyr, arcs, rows, cols) {
  var shapes = lyr.shapes,
      bounds = arcs.getBounds(),
      xmin = bounds.xmin,
      ymin = bounds.ymin,
      w = bounds.width(),
      h = bounds.height(),
      properties = lyr.data ? lyr.data.getRecords() : null,
      groups = [];

  function groupId(shpBounds) {
    var c = Math.floor((shpBounds.centerX() - xmin) / w * cols),
        r = Math.floor((shpBounds.centerY() - ymin) / h * rows);
    c = utils.clamp(c, 0, cols-1);
    r = utils.clamp(r, 0, rows-1);
    return r * cols + c;
  }

  function groupName(i) {
    var c = i % cols + 1,
        r = Math.floor(i / cols) + 1;
    return "r" + r + "c" + c;
  }

  shapes.forEach(function(shp, i) {
    var bounds = arcs.getMultiShapeBounds(shp),
        idx = groupId(bounds),
        group = groups[idx];
    if (!group) {
      group = groups[idx] = {
        shapes: [],
        properties: properties ? [] : null,
        bounds: new Bounds(),
        name: MapShaper.getSplitLayerName(lyr.name, groupName(idx))
      };
    }
    group.shapes.push(shp);
    group.bounds.mergeBounds(bounds);
    if (group.properties) {
      group.properties.push(properties[i]);
    }
  });

  var layers = [];
  groups.forEach(function(group, i) {
    if (!group) return; // empty cell
    var groupLyr = {
      shapes: group.shapes,
      name: group.name
    };
    utils.defaults(groupLyr, lyr);
    if (group.properties) {
      groupLyr.data = new DataTable(group.properties);
    }
    layers.push(groupLyr);
  });

  return layers;
};




// Recursively divide a layer into two layers until a (compiled) expression
// no longer returns true. The original layer is split along the long side of
// its bounding box, so that each split-off layer contains half of the original
// shapes (+/- 1).
//
api.subdivideLayer = function(lyr, arcs, exp) {
  return MapShaper.subdivide(lyr, arcs, MapShaper.compileCalcExpression(exp));
};

MapShaper.subdivide = function(lyr, arcs, compiled) {
  var divide = compiled(lyr, arcs),
      subdividedLayers = [],
      tmp, bounds, lyr1, lyr2;

  if (!utils.isBoolean(divide)) {
    stop("[subdivide] Expression must evaluate to true or false");
  }
  if (divide) {
    bounds = MapShaper.getLayerBounds(lyr, arcs);
    tmp = MapShaper.divideLayer(lyr, arcs, bounds);
    lyr1 = tmp[0];
    if (lyr1.shapes.length > 1 && lyr1.shapes.length < lyr.shapes.length) {
      utils.merge(subdividedLayers, MapShaper.subdivide(lyr1, arcs, compiled));
    } else {
      subdividedLayers.push(lyr1);
    }

    lyr2 = tmp[1];
    if (lyr2.shapes.length > 1 && lyr2.shapes.length < lyr.shapes.length) {
      utils.merge(subdividedLayers, MapShaper.subdivide(lyr2, arcs, compiled));
    } else {
      subdividedLayers.push(lyr2);
    }
  } else {
    subdividedLayers.push(lyr);
  }

  subdividedLayers.forEach(function(lyr2, i) {
    lyr2.name = MapShaper.getSplitLayerName(lyr.name, i + 1);
    utils.defaults(lyr2, lyr);
  });
  return subdividedLayers;
};

// split one layer into two layers containing the same number of shapes (+-1),
// either horizontally or vertically
//
MapShaper.divideLayer = function(lyr, arcs, bounds) {
  var properties = lyr.data ? lyr.data.getRecords() : null,
      shapes = lyr.shapes,
      lyr1, lyr2;
  lyr1 = {
    geometry_type: lyr.geometry_type,
    shapes: [],
    data: properties ? [] : null
  };
  lyr2 = {
    geometry_type: lyr.geometry_type,
    shapes: [],
    data: properties ? [] : null
  };

  var useX = bounds && bounds.width() > bounds.height();
  // TODO: think about case where there are null shapes with NaN centers
  var centers = shapes.map(function(shp) {
    var bounds = arcs.getMultiShapeBounds(shp);
    return useX ? bounds.centerX() : bounds.centerY();
  });
  var ids = utils.range(centers.length);
  ids.sort(function(a, b) {
    return centers[a] - centers[b];
  });
  ids.forEach(function(shapeId, i) {
    var dest = i < shapes.length / 2 ? lyr1 : lyr2;
    dest.shapes.push(shapes[shapeId]);
    if (properties) {
      dest.data.push(properties[shapeId]);
    }
  });

  if (properties) {
    lyr1.data = new DataTable(lyr1.data);
    lyr2.data = new DataTable(lyr2.data);
  }
  return [lyr1, lyr2];
};




api.sortFeatures = function(lyr, arcs, opts) {
  var n = MapShaper.getFeatureCount(lyr),
      ascending = !opts.descending,
      compiled = MapShaper.compileFeatureExpression(opts.expression, lyr, arcs),
      values = [];

  utils.repeat(n, function(i) {
    values.push(compiled(i));
  });

  var ids = utils.getSortedIds(values, ascending);
  if (lyr.shapes) {
    utils.reorderArray(lyr.shapes, ids);
  }
  if (lyr.data) {
    utils.reorderArray(lyr.data.getRecords(), ids);
  }
};




// TODO: consider refactoring to allow modules
// @cmd  example: {name: "dissolve", options:{field: "STATE"}}
// @dataset  format: {arcs: <ArcCollection>, layers:[]}
// @done callback: function(err, dataset)
//
api.runCommand = function(cmd, dataset, cb) {
  var name = cmd.name,
      opts = cmd.options,
      targetLayers,
      outputLayers,
      outputFiles,
      arcs;

  try { // catch errors from synchronous functions

    T.start();
    if (dataset) {
      arcs = dataset.arcs;
      if (dataset.layers.length > 0 === false) {
        error("Dataset contains 0 layers");
      }


      if (opts.target) {
        targetLayers = MapShaper.findMatchingLayers(dataset.layers, opts.target);
        if (!targetLayers.length) {
          stop(utils.format('[%s] Missing target layer: %s\nAvailable layers: %s',
            name, opts.target, MapShaper.getFormattedLayerList(dataset.layers)));
        }
      } else {
        targetLayers = dataset.layers; // default: all layers
      }
    }

    if (name == 'calc') {
      MapShaper.applyCommand(api.calc, targetLayers, arcs, opts);

    } else if (name == 'clip') {
      outputLayers = api.clipLayers(targetLayers, opts.source, dataset, opts);

    } else if (name == 'dissolve') {
      outputLayers = MapShaper.applyCommand(api.dissolve, targetLayers, arcs, opts);

    } else if (name == 'dissolve2') {
      outputLayers = MapShaper.applyCommand(api.dissolvePolygons2, targetLayers, dataset, opts);

    } else if (name == 'each') {
      MapShaper.applyCommand(api.evaluateEachFeature, targetLayers, arcs, opts.expression, opts);

    } else if (name == 'erase') {
      outputLayers = api.eraseLayers(targetLayers, opts.source, dataset, opts);

    } else if (name == 'explode') {
      outputLayers = MapShaper.applyCommand(api.explodeFeatures, targetLayers, arcs, opts);

    } else if (name == 'filter') {
      outputLayers = MapShaper.applyCommand(api.filterFeatures, targetLayers, arcs, opts);

    } else if (name == 'filter-fields') {
      MapShaper.applyCommand(api.filterFields, targetLayers, opts.fields);

    } else if (name == 'filter-islands') {
      MapShaper.applyCommand(api.filterIslands, targetLayers, arcs, opts);

    } else if (name == 'filter-slivers') {
      MapShaper.applyCommand(api.filterSlivers, targetLayers, arcs, opts);

    } else if (name == 'flatten') {
      outputLayers = MapShaper.applyCommand(api.flattenLayer, targetLayers, dataset, opts);

    } else if (name == 'i') {
      dataset = api.importFiles(cmd.options);

    } else if (name == 'info') {
      api.printInfo(dataset);

    } else if (name == 'innerlines') {
      outputLayers = MapShaper.applyCommand(api.convertPolygonsToInnerLines, targetLayers, arcs, opts);

    } else if (name == 'join') {
      MapShaper.applyCommand(api.join, targetLayers, dataset, opts);

    } else if (name == 'layers') {
      outputLayers = MapShaper.applyCommand(api.filterLayers, dataset.layers, opts.layers);

    } else if (name == 'lines') {
      outputLayers = MapShaper.applyCommand(api.convertPolygonsToTypedLines, targetLayers, arcs, opts.fields, opts);

    } else if (name == 'stitch') {
      api.stitch(dataset);

    } else if (name == 'merge-layers') {
      // careful, returned layers are modified input layers
      outputLayers = api.mergeLayers(targetLayers);

    } else if (name == 'o') {
      outputFiles = MapShaper.exportFileContent(utils.defaults({layers: targetLayers}, dataset), opts);
      if (opts.__nowrite) {
        done(null, outputFiles);
      } else {
        MapShaper.writeFiles(outputFiles, opts, done);
      }
      return;

    } else if (name == 'points') {
      outputLayers = MapShaper.applyCommand(api.createPointLayer, targetLayers, arcs, opts);

    } else if (name == 'proj') {
      api.proj(dataset, opts);

    } else if (name == 'rename-fields') {
      MapShaper.applyCommand(api.renameFields, targetLayers, opts.fields);

    } else if (name == 'rename-layers') {
      api.renameLayers(targetLayers, opts.names);

    } else if (name == 'repair') {
      outputLayers = MapShaper.repairPolygonGeometry(targetLayers, dataset, opts);

    } else if (name == 'simplify') {
      api.simplify(dataset, opts);

    } else if (name == 'sort') {
      MapShaper.applyCommand(api.sortFeatures, targetLayers, arcs, opts);

    } else if (name == 'split') {
      outputLayers = MapShaper.applyCommand(api.splitLayer, targetLayers, opts.field, opts);

    } else if (name == 'split-on-grid') {
      outputLayers = MapShaper.applyCommand(api.splitLayerOnGrid, targetLayers, arcs, opts.rows, opts.cols);

    } else if (name == 'subdivide') {
      outputLayers = MapShaper.applyCommand(api.subdivideLayer, targetLayers, arcs, opts.expression);

    } else {
      error("Unhandled command: [" + name + "]");
    }

    // apply name parameter
    if ('name' in opts) {
      // TODO: consider uniqifying multiple layers here
      (outputLayers || targetLayers || dataset.layers).forEach(function(lyr) {
        lyr.name = opts.name;
      });
    }

    // integrate output layers into the dataset
    if (outputLayers) {
      if (opts.no_replace) {
        dataset.layers = dataset.layers.concat(outputLayers);
      } else {
        // TODO: consider replacing old layers as they are generated, for gc
        MapShaper.replaceLayers(dataset, targetLayers, outputLayers);
      }
    }
  } catch(e) {
    done(e);
    return;
  }

  done(null);

  function done(err, output) {
    T.stop('-' + name);
    cb(err, err ? null : output || dataset);
  }
};

// Apply a command to an array of target layers
MapShaper.applyCommand = function(func, targetLayers) {
  var args = utils.toArray(arguments).slice(2);
  return targetLayers.reduce(function(memo, lyr) {
    var result = func.apply(null, [lyr].concat(args));
    if (utils.isArray(result)) { // some commands return an array of layers
      memo = memo.concat(result);
    } else if (result) { // assuming result is a layer
      memo.push(result);
    }
    return memo;
  }, []);
};

MapShaper.getFormattedLayerList = function(layers) {
  return layers.reduce(function(memo, lyr, i) {
    return memo + '\n  [' + i + ']  ' + (lyr.name || '[unnamed]');
  }, '') || '[none]';
};




function CommandParser() {
  var _usage = "",
      _examples = [],
      _commands = [],
      _default = null,
      _note;

  if (this instanceof CommandParser === false) return new CommandParser();

  this.usage = function(str) {
    _usage = str;
    return this;
  };

  this.note = function(str) {
    _note = str;
    return this;
  };

  // set a default command; applies to command line args preceding the first
  // explicit command
  this.default = function(str) {
    _default = str;
  };

  this.example = function(str) {
    _examples.push(str);
  };

  this.command = function(name) {
    var opts = new CommandOptions(name);
    _commands.push(opts);
    return opts;
  };

  this.parseArgv = function(raw) {
    var commandDefs = getCommands(),
        commandRxp = /^--?([a-z][\w-]*)$/i,
        commands = [], cmd,
        argv = raw.map(utils.trimQuotes), // remove one level of single or dbl quotes
        cmdName, cmdDef, opt;

    while (argv.length > 0) {
      // if there are arguments before the first explicit command, use the default command
      if (commands.length === 0 && moreOptions(argv)) {
        cmdName = _default;
      } else {
        cmdName = readCommandName(argv);
      }
      if (!cmdName) stop("Invalid command:", argv[0]);
      cmdDef = findCommandDefn(cmdName, commandDefs);
      if (!cmdDef) {
        stop("Unknown command:", cmdName);
      }
      cmd = {
        name: cmdDef.name,
        options: {},
        _: []
      };

      while (moreOptions(argv)) {
        opt = readNamedOption(argv, cmdDef);
        if (!opt) {
          // not a defined option; add it to _ array for later processing
          cmd._.push(argv.shift());
        } else {
          cmd.options[opt[0]] = opt[1];
        }
      }

      if (cmdDef.validate) {
        try {
          cmdDef.validate(cmd);
        } catch(e) {
          stop("[" + cmdName + "] " + e.message);
        }
      }
      commands.push(cmd);
    }
    return commands;

    function moreOptions(argv) {
      return argv.length > 0 && !commandRxp.test(argv[0]);
    }

    function readNamedOption(argv, cmdDef) {
      var token = argv[0],
          optRxp = /^([a-z0-9_+-]+)=(?!\=)(.*)$/i, // exclude ==
          match = optRxp.exec(token),
          name = match ? match[1] : token,
          optDef = findOptionDefn(name, cmdDef),
          optName,
          optVal;

      if (!optDef) return null;

      if (match && (optDef.type == 'flag' || optDef.assign_to)) {
        stop("-" + cmdDef.name + " " + name + " doesn't take a value");
      }

      if (match) {
        argv[0] = utils.trimQuotes(match[2]);
      } else {
        argv.shift();
      }

      optName = optDef.assign_to || optDef.name.replace(/-/g, '_');
      optVal = readOptionValue(argv, optDef);
      if (optVal === null) {
        stop("Invalid value for -" + cmdDef.name + " " + optName + "=<value>");
      }
      return [optName, optVal];
    }

    function readOptionValue(args, def) {
      var type = def.type,
          raw, val;
      if (type == 'flag') {
        val = true;
      } else if (def.assign_to) { // opt is a member of a set, assigned to another name
        val = def.name;
      } else if (args.length === 0 || commandRxp.test(args[0])) {
        val = null;
      } else {
        raw = args[0];
        if (type == 'number') {
          val = Number(raw);
        } else if (type == 'integer') {
          val = Math.round(Number(raw));
        } else if (type == 'comma-sep') {
          val = raw.split(',');
        } else if (type) {
          val = null; // unknown type
        } else {
          val = raw; // string
        }

        if (val !== val || val === null) {
          val = null; // null indicates invalid value
        } else {
          args.shift(); // good value, remove from argv
        }
      }

      return val;
    }

    // Check first element of an array of tokens; remove and return if it looks
    // like a command name, else return null;
    function readCommandName(args) {
      var match = commandRxp.exec(args[0]);
      if (match) {
        args.shift();
        return match[1];
      }
      return null;
    }

    function findCommandDefn(name, arr) {
      return utils.find(arr, function(cmd) {
        return cmd.name === name || cmd.alias === name;
      });
    }

    function findOptionDefn(name, cmd) {
      return utils.find(cmd.options, function(o) {
        return o.name === name || o.alias === name;
      });
    }
  };

  this.getHelpMessage = function(commandNames) {
    var helpStr = '',
        cmdPre = '  ',
        optPre = '  ',
        exPre = '  ',
        gutter = '  ',
        colWidth = 0,
        detailView = false,
        helpCommands, allCommands;

    allCommands = getCommands().filter(function(cmd) {
      // hide commands without a description
      return !!cmd.describe;
    });

    if (commandNames) {
      detailView = true;
      helpCommands = commandNames.reduce(function(memo, name) {
        var cmd = utils.find(allCommands, function(cmd) {return cmd.name == name;});
        if (cmd) memo.push(cmd);
        return memo;
      }, []);

      allCommands.filter(function(cmd) {
        return utils.contains(commandNames, cmd.name);
      });
      if (helpCommands.length === 0) {
        detailView = false;
      }
    }

    if (!detailView) {
      if (_usage) {
        helpStr +=  "\n" + _usage + "\n\n";
      }
      helpCommands = allCommands;
    }

    // Format help strings, calc width of left column.
    colWidth = helpCommands.reduce(function(w, obj) {
      var help = cmdPre + (obj.name ? "-" + obj.name : "");
      if (obj.alias) help += ", -" + obj.alias;
      obj.help = help;
      if (detailView) {
        w = obj.options.reduce(function(w, opt) {
          if (opt.describe) {
            w = Math.max(formatOption(opt), w);
          }
          return w;
        }, w);
      }
      return Math.max(w, help.length);
    }, 0);

    // Layout help display
    helpCommands.forEach(function(cmd) {
      if (!detailView && cmd.title) {
        helpStr += cmd.title + "\n";
      }
      if (detailView) {
        helpStr += '\nCommand\n';
      }
      helpStr += formatHelpLine(cmd.help, cmd.describe);
      if (detailView && cmd.options.length > 0) {
        helpStr += '\nOptions\n';
        cmd.options.forEach(function(opt) {
          if (opt.help && opt.describe) {
            helpStr += formatHelpLine(opt.help, opt.describe);
          }
        });
      }
      if (detailView && cmd.examples) {
        helpStr += '\nExample' + (cmd.examples.length > 1 ? 's' : ''); //  + '\n';
        cmd.examples.forEach(function(ex) {
          ex.split('\n').forEach(function(line) {
            helpStr += '\n' + exPre + line;
          });
          helpStr += '\n';
        });
      }
    });

    // additional notes for non-detail view
    if (!detailView) {
      if (_examples.length > 0) {
        helpStr += "\nExamples\n";
        _examples.forEach(function(str) {
          helpStr += "\n" + str + "\n";
        });
      }
      if (_note) {
        helpStr += '\n' + _note;
      }
    }

    return helpStr;

    function formatHelpLine(help, desc) {
      return utils.rpad(help, colWidth, ' ') + gutter + (desc || '') + '\n';
    }

    function formatOption(o) {
      o.help = optPre;
      if (o.label) {
        o.help += o.label;
      } else {
        o.help += o.name;
        if (o.alias) o.help += ", " + o.alias;
        if (o.type != 'flag' && !o.assign_to) o.help += "=";
      }
      return o.help.length;
    }

  };

  this.printHelp = function(commands) {
    message(this.getHelpMessage(commands));
  };

  function getCommands() {
    return _commands.map(function(cmd) {
      return cmd.done();
    });
  }
}

function CommandOptions(name) {
  var _command = {
    name: name,
    options: []
  };

  this.validate = function(f) {
    _command.validate = f;
    return this;
  };

  this.describe = function(str) {
    _command.describe = str;
    return this;
  };

  this.example = function(str) {
    if (!_command.examples) {
      _command.examples = [];
    }
    _command.examples.push(str);
    return this;
  };

  this.alias = function(name) {
    _command.alias = name;
    return this;
  };

  this.title = function(str) {
    _command.title = str;
    return this;
  };

  this.option = function(name, opts) {
    opts = opts || {}; // accept just a name -- some options don't need properties
    if (!utils.isString(name) || !name) error("Missing option name");
    if (!utils.isObject(opts)) error("Invalid option definition:", opts);
    opts.name = name;
    _command.options.push(opts);
    return this;
  };

  this.done = function() {
    return _command;
  };
}





function validateHelpOpts(cmd) {
  var commands = validateCommaSepNames(cmd._[0]);
  if (commands) {
    cmd.options.commands = commands;
  }
}

function validateInputOpts(cmd) {
  var o = cmd.options,
      _ = cmd._;

  if (_[0] == '-' || _[0] == '/dev/stdin') {
    o.stdin = true;
  } else if (_.length > 0) {
    o.files = _;
  }

  if ("precision" in o && o.precision > 0 === false) {
    error("precision= option should be a positive number");
  }

  if (o.encoding) {
    o.encoding = MapShaper.validateEncoding(o.encoding);
  }
}

function validateSimplifyOpts(cmd) {
  var o = cmd.options,
      _ = cmd._;

  var pctStr = o.pct || "";
  if (_.length > 0) {
    if (/^[0-9.]+%?$/.test(_[0])) {
      pctStr = _.shift();
    }
    if (_.length > 0) {
      error("Unparsable option:", _.join(' '));
    }
  }

  if (pctStr) {
    var isPct = pctStr.indexOf('%') > 0;
    if (isPct) {
      o.pct = Number(pctStr.replace('%', '')) / 100;
    } else {
      o.pct = Number(pctStr);
    }
    if (!(o.pct >= 0 && o.pct <= 1)) {
      error(utils.format("Out-of-range pct value: %s", pctStr));
    }
  }

  var intervalStr = o.interval;
  if (intervalStr) {
    o.interval = Number(intervalStr);
    if (o.interval >= 0 === false) {
      error(utils.format("Out-of-range interval value: %s", intervalStr));
    }
  }

  if (isNaN(o.interval) && isNaN(o.pct) && !o.resolution) {
    error("Command requires an interval, pct or resolution parameter");
  }
}

function validateJoinOpts(cmd) {
  var o = cmd.options;
  o.source = o.source || cmd._[0];
  if (!o.source) {
    error("Command requires the name of a layer or file to join");
  }
}

function validateSplitOpts(cmd) {
  if (cmd._.length == 1) {
    cmd.options.field = cmd._[0];
  } else if (cmd._.length > 1) {
    error("Command takes a single field name");
  }
}

function validateClipOpts(cmd) {
  var opts = cmd.options;
  if (cmd._[0]) {
    opts.source = cmd._[0];
  }
  if (opts.bbox) {
    // assume comma-sep bbox has been parsed into array of strings
    opts.bbox = opts.bbox.map(parseFloat);
  }
  if (!opts.source && !opts.bbox) {
    error("Command requires a source file, layer id or bbox");
  }
  if (!opts.no_cleanup) {
    // Remove unused arcs after clipping/erasing by default.
    opts.cleanup = true;
  }
}

function validateDissolveOpts(cmd) {
  var _= cmd._,
      o = cmd.options;
  if (_.length == 1) {
    o.field = _[0];
  } else if (_.length > 1) {
    error("Command takes a single field name");
  }
}

function validateMergeLayersOpts(cmd) {
  if (cmd._.length > 0) error("Unexpected option:", cmd._);
}

function validateRenameLayersOpts(cmd) {
  cmd.options.names = validateCommaSepNames(cmd._[0]) || null;
}

function validateSplitOnGridOpts(cmd) {
  var o = cmd.options;
  if (cmd._.length == 1) {
    var tmp = cmd._[0].split(',');
    o.cols = parseInt(tmp[0], 10);
    o.rows = parseInt(tmp[1], 10) || o.cols;
  }

  if (o.rows > 0 === false || o.cols > 0 === false) {
    error("Command expects cols,rows");
  }
}

function validateLinesOpts(cmd) {
  try {
    var fields = validateCommaSepNames(cmd.options.fields || cmd._[0]);
    if (fields) cmd.options.fields = fields;
  } catch (e) {
    error("Command takes a comma-separated list of fields");
  }
}


function validateInnerLinesOpts(cmd) {
  if (cmd._.length > 0) {
    error("Command takes no arguments");
  }
}

function validateSubdivideOpts(cmd) {
  if (cmd._.length !== 1) {
    error("Command requires a JavaScript expression");
  }
  cmd.options.expression = cmd._[0];
}

function validateFilterFieldsOpts(cmd) {
  try {
    var fields = validateCommaSepNames(cmd._[0]);
    cmd.options.fields = fields || [];
  } catch(e) {
    error("Command requires a comma-sep. list of fields");
  }
}

function validateExpressionOpts(cmd) {
  if (cmd._.length == 1) {
    cmd.options.expression = cmd._[0];
  } else if (cmd._.length > 1) {
    error("Unparsable arguments:", cmd._);
  }
}

function validateOutputOpts(cmd) {
  var _ = cmd._,
      o = cmd.options,
      arg = _[0] || "",
      pathInfo = utils.parseLocalPath(arg);

  if (_.length > 1) {
    error("Command takes one file or directory argument");
  }

  if (arg == '-' || arg == '/dev/stdout') {
    o.stdout = true;
  } else if (arg && !pathInfo.extension) {
    if (!cli.isDirectory(arg)) {
      error("Unknown output option:", arg);
    }
    o.output_dir = arg;
  } else if (arg) {
    if (pathInfo.directory) {
      o.output_dir = pathInfo.directory;
      cli.validateOutputDir(o.output_dir);
    }
    o.output_file = pathInfo.filename;
    if (MapShaper.filenameIsUnsupportedOutputType(o.output_file)) {
      error("Output file looks like an unsupported file type:", o.output_file);
    }
  }

  if (o.format) {
    o.format = o.format.toLowerCase();
    if (o.format == 'csv') {
      o.format = 'dsv';
      o.delimiter = o.delimiter || ',';
    } else if (o.format == 'tsv') {
      o.format = 'dsv';
      o.delimiter = o.delimiter || '\t';
    }
    if (!MapShaper.isSupportedOutputFormat(o.format)) {
      error("Unsupported output format:", o.format);
    }
  }

  if (o.delimiter) {
    // convert "\t" '\t' \t to tab
    o.delimiter = o.delimiter.replace(/^["']?\\t["']?$/, '\t');
    if (!MapShaper.isSupportedDelimiter(o.delimiter)) {
      error("Unsupported delimiter:", o.delimiter);
    }
  }

  if (o.encoding) {
    o.encoding = MapShaper.validateEncoding(o.encoding);
  }

  // topojson-specific
  if ("quantization" in o && o.quantization > 0 === false) {
    error("quantization= option should be a nonnegative integer");
  }

  if ("topojson_precision" in o && o.topojson_precision > 0 === false) {
    error("topojson-precision= option should be a positive number");
  }

}

// Convert a comma-separated string into an array of trimmed strings
// Return null if list is empty
function validateCommaSepNames(str, min) {
  if (!min && !str) return null; // treat
  if (!utils.isString(str)) {
    error ("Expected a comma-separated list; found:", str);
  }
  var parts = str.split(',').map(utils.trim).filter(function(s) {return !!s;});
  if (min && min > parts.length < min) {
    error(utils.format("Expected a list of at least %d member%s; found: %s", min, utils.pluralSuffix(min), str));
  }
  return parts.length > 0 ? parts : null;
}




MapShaper.splitShellTokens = function(str) {
  var BAREWORD = '([^\\s\'"])+';
  var SINGLE_QUOTE = '"((\\\\"|[^"])*?)"';
  var DOUBLE_QUOTE = '\'((\\\\\'|[^\'])*?)\'';
  var rxp = new RegExp('(' + BAREWORD + '|' + SINGLE_QUOTE + '|' + DOUBLE_QUOTE + ')*', 'g');
  var matches = str.match(rxp) || [];
  var chunks = matches.filter(function(chunk) {
    // single backslashes may be present in multiline commands pasted from a makefile, e.g.
    return !!chunk && chunk != '\\';
  }).map(utils.trimQuotes);
  return chunks;
};

utils.trimQuotes = function(raw) {
  var len = raw.length, first, last;
  if (len >= 2) {
    first = raw.charAt(0);
    last = raw.charAt(len-1);
    if (first == '"' && last == '"' || first == "'" && last == "'") {
      return raw.substr(1, len-2);
    }
  }
  return raw;
};




MapShaper.getOptionParser = function() {
  // definitions of options shared by more than one command
  var targetOpt = {
        describe: "layer(s) to target (comma-sep. list); default is all layers"
      },
      nameOpt = {
        describe: "rename the edited layer(s)"
      },
      noReplaceOpt = {
        alias: "+",
        type: 'flag',
        describe: "retain the original layer(s) instead of replacing"
      },
      encodingOpt = {
        describe: "text encoding (applies to .dbf and delimited text files)"
      },
      autoSnapOpt = {
        alias: "snap",
        describe: "snap nearly identical points to fix minor topology errors",
        type: "flag"
      },
      snapIntervalOpt = {
        describe: "specify snapping distance in source units",
        type: "number"
      },
      sumFieldsOpt = {
        describe: "fields to sum when dissolving  (comma-sep. list)",
        type: "comma-sep"
      },
      copyFieldsOpt = {
        describe: "fields to copy when dissolving (comma-sep. list)",
        type: "comma-sep"
      },
      dissolveFieldOpt = {
        label: "<field>",
        describe: "(optional) name of a data field to dissolve on"
      },
      bboxOpt = {
        type: "comma-sep",
        describe: "comma-sep. bounding box: xmin,ymin,xmax,ymax"
      };

  var parser = new CommandParser(),
      usage = "Usage:  mapshaper -<command> [options] ...";

  parser.usage(usage);

  /*
  parser.example("Fix minor topology errors, simplify to 10%, convert to GeoJSON\n" +
      "$ mapshaper states.shp auto-snap -simplify 10% -o format=geojson");

  parser.example("Aggregate census tracts to counties\n" +
      "$ mapshaper tracts.shp -each \"CTY_FIPS=FIPS.substr(0, 5)\" -dissolve CTY_FIPS");
  */

  parser.note("Enter mapshaper -help <command> to view options for a single command");

  parser.default('i');

  parser.command('i')
    .title("Editing commands")
    .describe("input one or more files")
    .validate(validateInputOpts)
    .option("files", {
      label: "<file(s)>",
      describe: "files to import (separated by spaces), or - to use stdin"
    })
    .option("merge-files", {
      describe: "merge features from compatible files into the same layer",
      type: "flag"
    })
    .option("combine-files", {
      describe: "import files to separate layers with shared topology",
      type: "flag"
    })
    .option("no-topology", {
      describe: "treat each shape as topologically independent",
      type: "flag"
    })
    .option("precision", {
      describe: "coordinate precision in source units, e.g. 0.001",
      type: "number"
    })
    .option("auto-snap", autoSnapOpt)
    .option("snap-interval", snapIntervalOpt)
    .option("encoding", encodingOpt)
    .option("id-field", {
      describe: "import Topo/GeoJSON id property to this field"
    })
    .option("field-types", {
      describe: "type hints for csv files, e.g. FIPS:str,STATE_FIPS:str",
      type: "comma-sep"
    })
    .option("name", {
      describe: "Rename the imported layer(s)"
    });

  parser.command('o')
    .describe("output edited content")
    .validate(validateOutputOpts)
    .option('_', {
      label: "<file|dir|->",
      describe: "(optional) name of output file or directory, or - for stdout"
    })
    .option("format", {
      describe: "export format (shapefile|geojson|topojson|json|dbf|csv|tsv)"
    })
    .option("target", targetOpt)
    .option("force", {
      type: "flag",
      describe: "let output files overwrite existing files"
    })
    .option("encoding", {
      describe: "text encoding of output dbf file"
    })
    .option("ldid", {
      // describe: "language driver id of dbf file",
      type: "number"
    })
    .option("bbox-index", {
      describe: "export a .json file with bbox of each layer",
      type: 'flag'
    })
    /*
    .option("drop-table", {
      describe: "delete data attributes",
      type: "flag"
    })
    */
    .option("cut-table", {
      describe: "detach data attributes from shapes and save as a JSON file",
      type: "flag"
    })
    .option("drop-table", {
      describe: "remove data attributes from output",
      type: "flag"
    })
    .option("precision", {
      describe: "coordinate precision in source units, e.g. 0.001",
      type: "number"
    })
    .option("bbox", {
      type: "flag",
      describe: "(Topo/GeoJSON) add bbox property"
    })
    .option("prettify", {
      type: "flag",
      describe: "(Topo/GeoJSON) format output for readability"
    })
    .option("id-field", {
      describe: "(Topo/GeoJSON) field to use for id property",
      type: "comma-sep"
    })
    .option("quantization", {
      describe: "(TopoJSON) specify quantization (auto-set by default)",
      type: "integer"
    })
    .option("no-quantization", {
      describe: "(TopoJSON) export arc coordinates without quantization",
      type: "flag"
    })
    .option('presimplify', {
      describe: "(TopoJSON) add per-vertex data for dynamic simplification",
      type: "flag"
    })
    .option("topojson-precision", {
      // describe: "pct of avg segment length for rounding (0.02 is default)",
      type: "number"
    })
    .option("delimiter", {
      describe: "(CSV) field delimiter"
    });

  parser.command('simplify')
    .validate(validateSimplifyOpts)
    .example("Retain 10% of removable vertices\n$ mapshaper input.shp -simplify 10%")
    .describe("simplify the geometry of polygon and polyline features")
    .option('pct', {
      alias: 'p',
      label: "<x%>",
      describe: "percentage of removable points to retain, e.g. 10%"
    })
    .option("dp", {
      alias: "rdp",
      describe: "use Ramer-Douglas-Peucker simplification",
      assign_to: "method"
    })
    .option("visvalingam", {
      describe: "use Visvalingam simplification with \"effective area\" metric",
      assign_to: "method"
    })
    .option("weighted", {
      describe: "use weighted Visvalingam simplification (default)",
      assign_to: "method"
    })
    .option("method", {
      // hidden option
    })
    .option("weighting", {
      type: "number",
      describe: "weighted Visvalingam coefficient (default is 0.7)"
    })
    .option("resolution", {
      describe: "output resolution as a grid (e.g. 1000x500)"
    })
    .option("interval", {
      // alias: "i",
      describe: "output resolution as a distance (e.g. 100)",
      type: "number"
    })
    .option("cartesian", {
      describe: "simplify decimal degree coords in 2D space (default is 3D)",
      type: "flag"
    })
    .option("keep-shapes", {
      describe: "prevent small polygon features from disappearing",
      type: "flag"
    })
    .option("no-repair", {
      describe: "don't remove intersections introduced by simplification",
      type: "flag"
    })
    .option("stats", {
      describe: "display simplification statistics",
      type: "flag"
    });

  parser.command("join")
    .describe("join data records from a file or layer to a layer")
    .example("Join a csv table to a Shapefile\n" +
      "(The :str suffix prevents FIPS field from being converted from strings to numbers)\n" +
      "$ mapshaper states.shp -join data.csv keys=STATE_FIPS,FIPS -field-types=FIPS:str -o joined.shp")
    .validate(validateJoinOpts)
    .option("source", {
      label: "<file>",
      describe: "file containing data records"
    })
    .option("keys", {
      describe: "join by matching target,source key fields; e.g. keys=FIPS,GEOID",
      type: "comma-sep"
    })
    .option("fields", {
      describe: "fields to join, e.g. fields=FIPS,POP (default is all fields)",
      type: "comma-sep"
    })
    .option("field-types", {
      describe: "type hints for importing csv files, e.g. FIPS:str,STATE_FIPS:str",
      type: "comma-sep"
    })
    .option("sum-fields", {
      describe: "fields to sum when multiple source records match the same target",
      type: "comma-sep"
    })
    .option("where", {
      describe: "use a JS expression to filter source records"
    })
    .option("force", {
      describe: "replace values from same-named fields",
      type: "flag"
    })
    .option("encoding", encodingOpt)
    .option("target", targetOpt);

  parser.command("each")
    .describe("create/update/delete data fields using a JS expression")
    .example("Add two calculated data fields to a layer of U.S. counties\n" +
        "$ mapshaper counties.shp -each 'STATE_FIPS=CNTY_FIPS.substr(0, 2), AREA=$.area'")
    .validate(validateExpressionOpts)
    .option("expression", {
      label: "<expression>",
      describe: "JS expression to apply to each target feature"
    })
    .option("where", {
      describe: "use a JS expression to select a subset of features"
    })
    .option("target", targetOpt);

   parser.command("sort")
    .describe("sort features using a JS expression")
    .validate(validateExpressionOpts)
    .option("expression", {
      label: "<expression>",
      describe: "JS expression to generate a sort key for each feature"
    })
    .option("ascending", {
      describe: "Sort in ascending order (default)",
      type: "flag"
    })
    .option("descending", {
      describe: "Sort in descending order",
      type: "flag"
    })
    .option("target", targetOpt);

  parser.command("filter")
    .describe("delete features using a JS expression")
    .validate(validateExpressionOpts)
    .option("expression", {
      label: "<expression>",
      describe: "delete features that evaluate to false"
    })
    .option("remove-empty", {
      type: "flag",
      describe: "delete features with null geometry"
    })
    .option("keep-shapes", {
      type: "flag"
    })
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("filter-islands")
    .describe("remove small detached polygon rings (islands)")
    .validate(validateExpressionOpts)

    .option("min-area", {
      type: "number",
      describe: "remove small-area islands (sq meters or projected units)"
    })
    .option("min-vertices", {
      type: "integer",
      describe: "remove low-vertex-count islands"
    })
    .option("remove-empty", {
      type: "flag",
      describe: "delete features with null geometry"
    })
    .option("target", targetOpt);

  parser.command("filter-slivers")
    // .describe("remove small polygon rings")
    .validate(validateExpressionOpts)

    .option("min-area", {
      type: "number",
      describe: "remove small-area rings (source units)"
    })
    /*
    .option("remove-empty", {
      type: "flag",
      describe: "delete features with null geometry"
    })
    */
    .option("target", targetOpt);

  parser.command("filter-fields")
    .describe('filter and optionally rename data fields')
    .validate(validateFilterFieldsOpts)
    .option("fields", {
      label: "<field(s)>",
      describe: "fields to retain/rename (comma-sep.), e.g. 'fips,st=state'"
    })
    .option("target", targetOpt);

  parser.command("rename-fields")
    .describe('rename data fields')
    .validate(validateFilterFieldsOpts)
    .option("fields", {
      label: "<field(s)>",
      describe: "fields to rename (comma-sep.), e.g. 'fips=STATE_FIPS,st=state'"
    })
    .option("target", targetOpt);

  parser.command("clip")
    .describe("use a polygon layer to clip another layer")
    .example("$ mapshaper states.shp -clip land_area.shp -o clipped.shp")
    .validate(validateClipOpts)
    .option("source", {
      label: "<file|layer>",
      describe: "file or layer containing clip polygons"
    })
    .option('no-cleanup', {type: 'flag'})
    .option("bbox", bboxOpt)
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("erase")
    .describe("use a polygon layer to erase another layer")
    .example("$ mapshaper land_areas.shp -erase water_bodies.shp -o erased.shp")
    .validate(validateClipOpts)
    .option("source", {
      label: "<file|layer>",
      describe: "file or layer containing erase polygons"
    })
    .option('no-cleanup', {type: 'flag'})
    .option("bbox", bboxOpt)
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("stitch");

  parser.command("dissolve")
    .validate(validateDissolveOpts)
    .describe("merge adjacent polygons")
    .example("Dissolve all polygons in a feature layer into a single polygon\n" +
      "$ mapshaper states.shp -dissolve -o country.shp")
    .example("Generate state-level polygons by dissolving a layer of counties\n" +
      "(STATE_FIPS, POPULATION and STATE_NAME are attribute field names)\n" +
      "$ mapshaper counties.shp -dissolve STATE_FIPS copy-fields=STATE_NAME sum-fields=POPULATION -o states.shp")
    .option("field", dissolveFieldOpt)
    .option("sum-fields", sumFieldsOpt)
    .option("copy-fields", copyFieldsOpt)
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("dissolve2")
    .validate(validateDissolveOpts)
    .describe("merge adjacent and overlapping polygons")
    .option("field", dissolveFieldOpt)
    .option("sum-fields", sumFieldsOpt)
    .option("copy-fields", copyFieldsOpt)
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("explode")
    .describe("divide multi-part features into single-part features")
    .option("convert-holes", {type: "flag"}) // testing
    .option("target", targetOpt);

  parser.command("innerlines")
    .describe("convert polygons to polylines along shared edges")
    .validate(validateInnerLinesOpts)
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("lines")
    .describe("convert polygons to polylines, classified by edge type")
    .validate(validateLinesOpts)
    .option("fields", {
      label: "<field(s)>",
      describe: "optional comma-sep. list of fields to create a hierarchy",
      type: "comma-sep"
    })
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("points")
    .describe("create a point layer from polygons or attribute data")
    .validate(function (cmd) {
      if (cmd._.length > 0) {
        error("Unknown argument:", cmd._[0]);
      }
    })
    .option("x", {
      describe: "field containing x coordinate"
    })
    .option("y", {
      describe: "field containing y coordinate"
    })
    .option("inner", {
      describe: "create an interior point for each polygon's largest ring",
      type: "flag"
    })
    .option("centroid", {
      describe: "create a centroid point for each polygon's largest ring",
      type: "flag"
    })
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("split")
    .describe("split features into separate layers using a data field")
    .validate(validateSplitOpts)
    .option("field", {
      label: '<field>',
      describe: "name of an attribute field (omit to split all features)"
    })
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("merge-layers")
    .describe("merge multiple layers into as few layers as possible")
    .validate(validateMergeLayersOpts)
    .option("name", nameOpt)
    .option("target", targetOpt);

  parser.command("rename-layers")
    .describe("assign new names to layers")
    .validate(validateRenameLayersOpts)
    .option("names", {
      label: "<name(s)>",
      type: "comma-sep",
      describe: "new layer name(s) (comma-sep. list)"
    })
    .option("target", targetOpt);

  parser.command("subdivide")
    .describe("recursively split a layer using a JS expression")
    .validate(validateSubdivideOpts)
    .option("expression", {
      label: "<expression>",
      describe: "boolean JS expression"
    })
    // .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("split-on-grid")
    .describe("split features into separate layers using a grid")
    .validate(validateSplitOnGridOpts)
    .option("-", {
      label: "<cols,rows>",
      describe: "size of the grid, e.g. -split-on-grid 12,10"
    })
    .option("cols", {
      type: "integer"
    })
    .option("rows", {
      type: "integer"
    })
    // .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("proj")
    // .describe("project the coordinates in a dataset")
    .option("densify", {
      type: "flag",
      describe: "interpolate points to approximate curves"
    })
    .option("spherical", {type: "flag"})
    .option("lng0", {type: "number"})
    .option("lat0", {type: "number"})
    .option("lat1", {type: "number"})
    .option("lat2", {type: "number"})
    .option("zone") // for UTM
    //.option("k0", {type: "number"})
    //.option("x0", {type: "number"})
    //.option("y0", {type: "number"})
    .validate(function(cmd) {
      var name = cmd._[0];
      if (!name) {
        error("Missing a projection name");
      }
      if (cmd._.length > 1) {
        error("Received one or more unknown projection parameters");
      }
      cmd.options.projection = name;
    });

  parser.command("calc")
    .title("\nInformational commands")
    .describe("Calculate statistics about the features in a layer")
    .example("Calculate the total area of a polygon layer\n" +
      "$ mapshaper polygons.shp -calc 'sum($.area)'")
    .example("Count census blocks in NY with zero population\n" +
      "$ mapshaper ny-census-blocks.shp -calc 'count()' where='POPULATION == 0'")
    .validate(function(cmd) {
      if (cmd._.length === 0) {
        error("Missing a JS expression");
      }
      validateExpressionOpts(cmd);
    })
    .option("expression", {
      label: "<expression>",
      describe: "functions: sum() average() median() max() min() count()"
    })
    .option("where", {
      describe: "use a JS expression to select a subset of features"
    })
    .option("target", targetOpt);

  parser.command('encodings')
    .describe("print list of supported text encodings (for .dbf import)");

  parser.command('projections');
    // .describe("print names of supported projections");

  parser.command('version')
    .alias('v')
    .describe("print mapshaper version");

  parser.command('info')
    .describe("print information about data layers");

  parser.command('verbose')
    .describe("print verbose processing messages");

  parser.command('help')
    .alias('h')
    .validate(validateHelpOpts)
    .describe("print help; takes optional command name")
    .option("commands", {
      label: "<command>",
      type: "comma-sep",
      describe: "view detailed information about a command"
    });

  // Work-in-progress (no .describe(), so hidden from -h)
  parser.command('tracing');
  parser.command("flatten")
    .option("target", targetOpt);
  /*
  parser.command("divide")
    .option("name", nameOpt)
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("fill-holes")
    .option("no-replace", noReplaceOpt)
    .option("target", targetOpt);

  parser.command("repair")
    .option("target", targetOpt);
  */

  return parser;
};




// Parse an array or a string of command line tokens into an array of
// command objects.
MapShaper.parseCommands = function(tokens) {
  if (utils.isString(tokens)) {
    tokens = MapShaper.splitShellTokens(tokens);
  }
  return MapShaper.getOptionParser().parseArgv(tokens);
};

// Parse a command line string for the browser console
MapShaper.parseConsoleCommands = function(raw) {
  var str = raw.replace(/^mapshaper\b/, '').trim();
  var parsed;
  if (/^[a-z]/.test(str)) {
    // add hyphen prefix to bare command
    str = '-' + str;
  }
  if (utils.contains(MapShaper.splitShellTokens(str), '-i')) {
    stop("The input command cannot be run in the browser");
  }
  parsed = MapShaper.parseCommands(str);
  // block implicit initial -i command
  if (parsed.length > 0 && parsed[0].name == 'i') {
    stop(utils.format("Unable to run [%s]", raw));
  }
  return parsed;
};





// Parse command line args into commands and run them
// @argv Array of command line tokens or single string of commands
api.runCommands = function(argv, done) {
  var commands;
  try {
    commands = MapShaper.parseCommands(argv);
  } catch(e) {
    return done(e);
  }

  if (commands.length === 0) {
    return done(new APIError("No commands to run"));
  }

  T.start("Start timing");
  MapShaper.runParsedCommands(commands, function(err, output) {
    T.stop("Total time");
    done(err, output);
  });
};

// Apply a set of processing commands to the contents of an input file
// @argv Command line arguments, as string or array
// @done Callback: function(<error>, <output>)
api.applyCommands = function(argv, content, done) {
  MapShaper.processFileContent(argv, content, function(err, exports) {
    var output = null;
    if (!err) {
      output = exports.map(function(obj) {
        return obj.content;
      });
      if (output.length == 1) {
        output = output[0];
      }
    }
    done(err, output);
  });
};

// Capture output data instead of writing files (useful for testing)
// @tokens Command line arguments, as string or array
// @content (may be null) Contents of input data file
// @done: Callback function(<error>, <output>); <output> is an array of objects
//        with properties "content" and "filename"
MapShaper.processFileContent = function(tokens, content, done) {
  var dataset, commands, lastCmd, inOpts;
  try {
    commands = MapShaper.parseCommands(tokens);
    commands = MapShaper.runAndRemoveInfoCommands(commands);

    // if we're processing raw content, import it to a dataset object
    if (content) {
      // if first command is -i, use -i options for importing
      if (commands[0] && commands[0].name == 'i') {
        inOpts = commands.shift().options;
      } else {
        inOpts = {};
      }
      dataset = MapShaper.importFileContent(content, null, inOpts);
    }

    // if last command is -o, use -o options for exporting
    lastCmd = commands[commands.length-1];
    if (!lastCmd || lastCmd.name != 'o') {
      lastCmd = {name: 'o', options: {}};
      commands.push(lastCmd);
    }
    // export to callback, not file
    lastCmd.options.__nowrite = true;
  } catch(e) {
    return done(e);
  }

  MapShaper.runParsedCommands(commands, dataset, done);
};

// Execute a sequence of commands
// Signature: function(commands, [dataset,] done)
// @commands Array of parsed commands
// @done: function(<error>, <dataset>)
//
MapShaper.runParsedCommands = function(commands) {
  var dataset = null,
      done;

  if (arguments.length == 2) {
    done = arguments[1];
  } else if (arguments.length == 3) {
    dataset = arguments[1];
    done = arguments[2];
  }

  if (!utils.isFunction(done)) {
    error("[runParsedCommands()] Missing a callback function");
  }

  if (!utils.isArray(commands)) {
    error("[runParsedCommands()] Expected an array of parsed commands");
  }

  commands = MapShaper.runAndRemoveInfoCommands(commands);
  if (commands.length === 0) {
    return done(null, dataset);
  }
  commands = MapShaper.divideImportCommand(commands);
  if (commands[0].name != 'i' && !dataset) {
    return done(new APIError("Missing a -i command"));
  }

  utils.reduceAsync(commands, dataset, function(dataset, cmd, nextCmd) {
    api.runCommand(cmd, dataset, nextCmd);
  }, done);
};

// If an initial import command indicates that several input files should be
//   processed separately, then duplicate the sequence of commands to run
//   once for each input file
// @commands Array of parsed commands
// Returns: either original command array or array of duplicated commands.
//
MapShaper.divideImportCommand = function(commands) {
  var firstCmd = commands[0],
      firstOpts = firstCmd.options,
      files = firstOpts.files || [];

  if (firstCmd.name != 'i' || files.length <= 1 || firstOpts.stdin ||
      firstOpts.merge_files || firstOpts.combine_files) {
    return commands;
  }
  return files.reduce(function(memo, file) {
    var importCmd = {
      name: 'i',
      options: utils.defaults({files:[file]}, firstOpts)
    };
    memo.push(importCmd);
    memo.push.apply(memo, commands.slice(1));
    return memo;
  }, []);
};

// Call @iter on each member of an array (similar to Array#reduce(iter))
//    iter: function(memo, item, callback)
// Call @done when all members have been processed or if an error occurs
//    done: function(err, memo)
// @memo: Initial value
//
utils.reduceAsync = function(arr, memo, iter, done) {
  var call = typeof setImmediate == 'undefined' ? setTimeout : setImmediate;
  var i=0;
  next(null, memo);

  function next(err, memo) {
    // Detach next operation from call stack to prevent overflow
    // Don't use setTimeout(, 0) if setImmediate is available
    // (setTimeout() can introduce a long delay if previous operation was slow,
    //    as of Node 0.10.32 -- a bug?)
    call(function() {
      if (err) {
        done(err, null);
      } else if (i < arr.length === false) {
        done(null, memo);
      } else {
        iter(memo, arr[i++], next);
      }
    }, 0);
  }
};

// Handle information commands and remove them from the list
MapShaper.runAndRemoveInfoCommands = function(commands) {
  return commands.filter(function(cmd) {
    if (cmd.name == 'version') {
      message(MapShaper.VERSION);
    } else if (cmd.name == 'encodings') {
      MapShaper.printEncodings();
    } else if (cmd.name == 'projections') {
      MapShaper.printProjections();
    } else if (cmd.name == 'help') {
      MapShaper.getOptionParser().printHelp(cmd.options.commands);
    } else if (cmd.name == 'verbose') {
      MapShaper.VERBOSE = true;
    } else if (cmd.name == 'tracing') {
      MapShaper.TRACING = true;
    } else {
      return true;
    }
    return false;
  });
};




// Handle an error caused by invalid input or misuse of API
function stop() {
  throw new APIError(MapShaper.formatLogArgs(arguments));
}

cli.isFile = function(path) {
  var ss = cli.statSync(path);
  return ss && ss.isFile() || false;
};

cli.fileSize = function(path) {
  var ss = cli.statSync(path);
  return ss && ss.size || 0;
};

cli.isDirectory = function(path) {
  var ss = cli.statSync(path);
  return ss && ss.isDirectory() || false;
};

// @encoding (optional) e.g. 'utf8'
cli.readFile = function(fname, encoding) {
  var rw = require('rw'),
      content = rw.readFileSync(fname);
  if (encoding) {
    content = MapShaper.decodeString(content, encoding);
  }
  return content;
};

// @content Buffer, ArrayBuffer or string
cli.writeFile = function(path, content) {
  if (content instanceof ArrayBuffer) {
    content = cli.convertArrayBuffer(content);
  }
  require('rw').writeFileSync(path, content);
};

// Returns Node Buffer
cli.convertArrayBuffer = function(buf) {
  var src = new Uint8Array(buf),
      dest = new Buffer(src.length);
  for (var i = 0, n=src.length; i < n; i++) {
    dest[i] = src[i];
  }
  return dest;
};

// Expand any "*" wild cards in file name
// (For the Windows command line; unix shells do this automatically)
cli.expandFileName = function(name) {
  if (name.indexOf('*') == -1) return [name];
  var path = utils.parseLocalPath(name),
      dir = path.directory || '.',
      listing = require('fs').readdirSync(dir),
      rxp = utils.wildcardToRegExp(path.filename);
  return listing.reduce(function(memo, item) {
    var path = require('path').join(dir, item);
    if (rxp.test(item) && cli.isFile(path)) {
      memo.push(path);
    }
    return memo;
  }, []);
};

// Expand any wildcards and check that files exist.
cli.validateInputFiles = function(files) {
  files = files.reduce(function(memo, name) {
    return memo.concat(cli.expandFileName(name));
  }, []);
  files.forEach(cli.checkFileExists);
  return files;
};

cli.validateOutputDir = function(name) {
  if (!cli.isDirectory(name)) {
    error("Output directory not found:", name);
  }
};

// TODO: rename and improve
// Want to test if a path is something readable (e.g. file or stdin)
cli.checkFileExists = function(path) {
  if (!cli.isFile(path) && path != '/dev/stdin') {
    stop("File not found (" + path + ")");
  }
};

cli.statSync = function(fpath) {
  var obj = null;
  try {
    obj = require('fs').statSync(fpath);
  } catch(e) {}
  return obj;
};

// Expose internal objects for testing
utils.extend(api.internal, {
  BinArray: BinArray,
  DouglasPeucker: DouglasPeucker,
  Visvalingam: Visvalingam,
  ShpReader: ShpReader,
  ShpType: ShpType,
  Bounds: Bounds
});

api.T = T;

if (typeof define === "function" && define.amd) {
  define("mapshaper", api);
} else if (typeof module === "object" && module.exports) {
  module.exports = api;
}
this.mapshaper = api;

}());