main.js

var express = require('express');
var redis = require('redis');
var io = require('socket.io');
var mu2Express = require("mu2express");
var util = require('util')
var app = express();
var http = require('http');
var server = http.createServer(app);
var io = require('socket.io').listen(server);
var crypto = require('crypto');
var crypto_salt = 'salty';

// Initialize db
var db = redis.createClient();
db.on("error", function (err) {
  console.log("Error: " + err);
});

//  Create new document. Basically increment a counter and hash the value with a salt.
app.post('/create', function(req, res) {
  db.incr('document_id', function (err, val) {
    res.redirect('/docs/'+crypto.createHash('sha1').update('salty'+val).digest('hex'));
    res.end();
  });
});

// Document specific page
app.get(/\/docs\/([A-Za-z0-9]{20})\/?/, function (req, res) {
  db.get("document."+req.params[0], function(err, reply) {
    reply = reply == null ? '' : new Buffer(reply, 'base64').toString('utf8');
    res.render('docs', {'locals' : {'content':reply, 'id':req.params[0]}});
  })
});

// Set up socket.io connection
io.on('connection', function (socket) {
  
  // set document, socket ids
  var document_id = 0;
  
  // bind method to map connections
  socket.on('bind', function (id) {
    console.info('socket ' + socket.id + ' bound to document ' + id.document_id);
    document_id = id.document_id;
    socket.emit('bound', {id:socket.id});
  });

  // text changed
  socket.on('update', function (data) {
    console.info('update on socket ' + socket.id + ' for document ' + document_id);
    
    // get the old content
    db.get(
      "document."+document_id,
      function(err, reply) {
        reply = reply == null ? '' : new Buffer(reply, 'base64').toString('utf8');
        
        // merge the new content
        var d = data;
        do {
          // calculate offsets 
          var lines = reply.split('\n');
          var offsets = [];
          for (var l=0; l < lines.length; ++l) {
            if (l == 0)
              offsets.push(0);
            else
              offsets.push(lines[l-1].length + offsets[l-1] + 1);
          }
          
          // perform edits
          var i = offsets[d.to.line] + d.to.ch;
          var j = offsets[d.from.line] + d.from.ch;
          if (i > j) {
            var k = j;
            j = i;
            i = k;
          }
          reply = reply.substring(0, i) + d.text.join('\n') + reply.substring(j);
          d = d.next;
        } while (d != undefined);
        
        console.log('Saving string:\n\n' + reply);
        
        // save the new content
        db.set(
          "document."+document_id,
          new Buffer(reply).toString('base64'),
          function (err, reply) {
            if (err != null) {
              console.log(err);
            }
            socket.broadcast.emit('update-'+document_id, data);
          }
        );
      }
    );
  });

  // disconnecting clients
  socket.on('disconnect', function () {
  });
});

// Run web server
app.engine('mustache', mu2Express.engine);
app.set('view engine', 'mustache');
app.set('views', __dirname + '/views');
app.use(express.bodyParser());
app.use(express.static(__dirname + '/public'));
app.use(express.static(__dirname + '/node_modules'));
server.listen(8000);