nbreader.js

/*
*  Author: James Martin (jamesml@cs.unc.edu)
*/

define(function() {
  "use strict";

  var Jupyter = require('base/js/namespace');
  var events = require('base/js/events');

  // Metadata
  var cell_ids = [];
  var selected_cell = 0;
  var selected_cell_id = 0;
  var selected_cell_num = 0; // Number of the selected cell down the page

  var mode = "command";
  var accessibility_mode = false;

  // jQuery Deferreds
  var $voices_loaded = $.Deferred();

  // Load voices before extension
  var voices;
  window.speechSynthesis.onvoiceschanged = function() {
    voices = window.speechSynthesis.getVoices();
    $voices_loaded.resolve();
  };

  // Use push() and shift() for queue functionality
  // Not super efficient for large queues (which may happen when we start adding individual messages to the queue)
  // There is an implementation of a queue in JavaScript which runs in amortized O(1) time
  var line_queue = []

  // Global speech properties
  var speech_properties;
  speech_properties = {
    lang: 'en-us',
    rate: 1
  }

  var applyProperties = function(msg, speech_properties) {
    msg.lang = speech_properties.lang;
    msg.voice = speech_properties.voice;
    msg.rate = speech_properties.rate;
  }

  /*
  * earcon_setup(): Prepares and binds functions to kernel and notebook events. Utilizes the WebAudio API to create tones
  */
  var earcon_setup = function(events) {

    var context = new AudioContext();

    /* VCO */
    var vco = context.createOscillator();
    vco.type = vco.SINE;
    vco.start(0);

    /* VCA */
    var vca = context.createGain();
    vca.gain.value = 0;

    /* Connections */
    vco.connect(vca);
    vca.connect(context.destination);

    var playHum = function() {
      vco.frequency.value = 200;
      vca.gain.value = 0.5;
    };

    var stopHum = function() {
      vca.gain.value = 0;
    };

    events.on("kernel_idle.Kernel", function() {
      stopHum();
    })

    events.on("kernel_busy.Kernel", function() {
      playHum();
    })

    events.on("notebook_saved.Notebook", function() {
      var m = "Notebook saved.";
      var msg = new SpeechSynthesisUtterance(m);

      msg.rate = 3;
      speechSynthesis.speak(msg);
    })

    events.on("edit_mode.Notebook", function() {
      var m = "Edit";
      mode = "edit"; // Set metadata
      var msg = new SpeechSynthesisUtterance(String(m));

      msg.rate = 3;
      speechSynthesis.speak(msg);
    })

    events.on("command_mode.Notebook", function() {
      var m = "Command";
      mode = "command"; // Set metadata
      var msg = new SpeechSynthesisUtterance(String(m));

      msg.rate = 3;
      speechSynthesis.speak(msg);
    })

    // This function provides navigational cues
    events.on("selected_cell_type_changed.Notebook", function() {
      $(".cell").css("border-style", "none");
      $(".cell.selected").css({"border-style": "solid", "border-width": "10px", "border-color": "green"})
      var previous_cell_num = selected_cell_num;

      cell_ids = get_cell_ids();

      selected_cell = Jupyter.notebook.get_selected_cell();
      selected_cell_id = Jupyter.notebook.get_selected_cell().cell_id;
      selected_cell_num = cell_ids.indexOf(selected_cell_id);

      var new_cell_num = selected_cell_num;

      var m = "";

      if (new_cell_num == 0) {
        m = "top";
      }else if (new_cell_num == cell_ids.length-1) {
        m = "bottom";
      }
      var msg = new SpeechSynthesisUtterance(String(m));
      msg.rate = 3
      speechSynthesis.speak(msg);
    })

    // jQuery delegation to bind this listener to any keypress
    $(document).on('keypress', '.code_cell.selected', function(e){
      var charCode = e.charCode;
      if (mode === 'edit' && e.ctrlKey === false){
        read_character(charCode);
      }
    })

    // jQuery delegation to bind this listener specifically to backspace
    $(document).on('keydown', '.code_cell.selected', function(e){
      // Backspace is registered on keydown rather than keypress

      // Switch statement for future expansion
      switch (e.keyCode){

        case 8:
        vco.frequency.value = 150;
        vca.gain.value = 0.5;

        setTimeout(function(){vca.gain.value = 0;}, 100);

        var msg = new SpeechSynthesisUtterance("back");
        msg.rate = 4;
        speechSynthesis.speak(msg);
        break;
      }
    })

  }

  function read_character(asciiNum){
    var keystroke = String.fromCharCode(asciiNum);
    var msg;

    // Create message to be read based on the ascii code of the keypress
    switch (asciiNum){

      // Exclamation
      case 33:
      msg = new SpeechSynthesisUtterance("exclamation");
      break;

      // Colon
      case 58:
      msg = new SpeechSynthesisUtterance("colon");
      break;

      // Semicolon
      case 59:
      msg = new SpeechSynthesisUtterance("Semicolon");
      break;

      // Equals
      case 61:
      msg = new SpeechSynthesisUtterance("equals");

      // Single quote
      case 39:
      msg = new SpeechSynthesisUtterance("single quote");
      break;

      // Double quote
      case 34:
      msg = new SpeechSynthesisUtterance("double quote");
      break;

      // Left paren
      case 40:
      msg = new SpeechSynthesisUtterance("left paren");
      break;

      // Right paren
      case 41:
      msg = new SpeechSynthesisUtterance("right paren");
      break;

      // Left bracket
      case 91:
      msg = new SpeechSynthesisUtterance("left bracket");
      break;

      // Right bracket
      case 93:
      msg = new SpeechSynthesisUtterance("right bracket");
      break;

      // Period
      case 46:
      msg = new SpeechSynthesisUtterance("dot");
      break;

      // Backslash
      case 47:
      msg = new SpeechSynthesisUtterance("backslash");
      break;

      default:
      msg = new SpeechSynthesisUtterance(keystroke);
    }
    msg.rate = 4;
    speechSynthesis.speak(msg);
  }


  /*
  * prepare(): Gets each line of the selected cell through the CodeMirror API and
  *            passes them to the global message queue to be read. Called by readLine()
  */
  function prepare(env) {

    var speech_properties = {
      lang: 'en-US',
      voice: voices.filter(function(voice) {
        return voice.name == 'Alex';
      })[0],
      rate: 1
    }

    // Grab selected cell
    var selected_cell = env.notebook.get_selected_cell();

    // Get the type of the current highlighted cell for intro line
    var cell_type = selected_cell.cell_type;

    // Grab doc of selected cell through the Code Mirror API
    var doc = selected_cell.code_mirror.doc;
    var type_msg = "" + cell_type + " cell with " + doc.size + "";
    if (doc.size == 1) {
      var type_msg = type_msg + " line.\n.";
    } else {
      var type_msg = type_msg + " lines.\n.";
    }
    var intro = new SpeechSynthesisUtterance(type_msg);
    applyProperties(intro, speech_properties);

    speechSynthesis.speak(intro);

    // Add each line of the cell to the global message queue
    doc.eachLine(function(line) {
      var l = {
        text: line.text,
        styles: line.styles,
        cell_type: cell_type,
        speech_properties: speech_properties
      }
      line_queue.push(l);
    })
  }

  /*
  * readLine() is the work horse for read.
  */
  function readLine() {
    if (line_queue.length > 0) {
      var l = line_queue.shift()
      console.log(l.styles);

      if (l.cell_type == 'markdown') {
        l.text = l.text.replace("#", "")
      }

      var utterance = new SpeechSynthesisUtterance(l.text);
      applyProperties(utterance, l.speech_properties);
      // After the line is finished speaking, call readLine() recursively to continue reading
      utterance.onend = function(event) {
        readLine()
      }

      speechSynthesis.speak(utterance);
    }
  }

  /*
  * read(): read a highlighted cell line by line. Lines of code are created as separate messages to speak and are added
  *         into the the global message queue sequentially. This allows for the entire reading to be cancelled (with kill) or a line to be
  *         skipped. prepare() adds lines to the global message queue, readLine() takes them off, parses, and adds to the speechSynthesis queue
  */
  var read = {
    help: 'read highlighted cell',
    handler: function(env) {
      prepare(env);
      readLine();
    }
  }

  // Abruptly stops reading, clears speech and line queue
  var cancel = {
    help: 'cancel reading of cell',
    handler: function() {
      window.speechSynthesis.cancel();
      line_queue = [];
    }
  }

  // Skips current line being read
  var skip = {
    help: 'skip current line being read',
    handler: function() {
      window.speechSynthesis.cancel();
    }
  }

  // Pause / resume reading
  var pause_resume = {
    help: 'pause/resume reading',
    handler: function() {
      if (window.speechSynthesis.paused == false) {
        window.speechSynthesis.pause();
      } else {
        window.speechSynthesis.resume();
      }
    }
  }

  var read_mode = {
    help: 'read current mode (command or edit)',
    handler: function() {
      var m = "You are in " + mode + " mode";
      var msg = new SpeechSynthesisUtterance(m);
      speechSynthesis.speak(msg);
    }
  }

  var read_cell_number = {
    help: 'read number of the cell in the notebook',
    handler: function() {
      var m = "Cell number " + (selected_cell_num+1) + " of " + cell_ids.length;
      var msg = new SpeechSynthesisUtterance(m);
      speechSynthesis.speak(msg);
    }
  }

  var toggle_accessibility_mode = {
    help: 'toggles CSS of the page for magnification',
    handler: function() {
      if(!accessibility_mode){
        $("#header").css('display', 'none');
        $("#site").css('display', 'inline');
        accessibility_mode = true;
      }else{
        $("#header").css('display', 'block');
        $("#site").css('display', 'block');
        accessibility_mode = false;
      }
    }
  }

  function get_cell_ids() {
    // Sets global cell_ids array
    var ids = Jupyter.notebook.get_cells().map(function(cell) {
      return cell.cell_id;
    });
    return ids;
  }

  var load_extension = function() {
    $.when($voices_loaded)
    .done(function() {
      console.log("Scripts loaded.")

      // Startup
      cell_ids = get_cell_ids();

      selected_cell_id = Jupyter.notebook.get_selected_cell().cell_id;
      selected_cell_num = cell_ids.indexOf(selected_cell_id);

      // Setup earcons
      earcon_setup(events);

      // Load actions
      var _toggle = Jupyter.keyboard_manager.actions.register(toggle_accessibility_mode, 'toggle', 'accessibility')

      var _read = Jupyter.keyboard_manager.actions.register(read, 'read', 'accessibility')
      var _read_cell_num = Jupyter.keyboard_manager.actions.register(read_cell_number, 'read cell number', 'accessibility')
      var _cancel = Jupyter.keyboard_manager.actions.register(cancel, 'cancel', 'accessibility')
      var _skip = Jupyter.keyboard_manager.actions.register(skip, 'skip', 'accessibility')
      var _pause_resume = Jupyter.keyboard_manager.actions.register(pause_resume, 'pause or resume reading', 'accessibility')
      var _read_mode = Jupyter.keyboard_manager.actions.register(read_mode, 'read current mode (command or edit)', 'accessibility')
      console.log("Reader loaded.")

      // Bind keyboard shortcuts
      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-T', _toggle)

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-R', _read)
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-R', _read)

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-G', _read_cell_num);
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-G', _read_cell_num);

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-ESC', _cancel)
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-ESC', _cancel)

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-P', _pause_resume)
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-P', _pause_resume)

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Shift-S', _skip)
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-S', _skip)

      Jupyter.keyboard_manager.command_shortcuts.add_shortcut('Ctrl-Shift-M', _read_mode)
      Jupyter.keyboard_manager.edit_shortcuts.add_shortcut('Ctrl-Shift-M', _read_mode)
      console.log("Shortcuts bound.")

      var msg = new SpeechSynthesisUtterance("Jupyter Notebook reader successfully loaded!");
      speechSynthesis.speak(msg);
    });
  }

  return {
    load_ipython_extension: load_extension
  }
})