Added support of operational transformation

lib/ot/client.js

@@ -0,0 +1,312 @@
+// translation of https://github.com/djspiewak/cccp/blob/master/agent/src/main/scala/com/codecommit/cccp/agent/state.scala
+
+if (typeof ot === 'undefined') {
+  var ot = {};
+}
+
+ot.Client = (function (global) {
+  'use strict';
+
+  // Client constructor
+  function Client (revision) {
+    this.revision = revision; // the next expected revision number
+    this.setState(synchronized_); // start state
+  }
+
+  Client.prototype.setState = function (state) {
+    this.state = state;
+  };
+
+  // Call this method when the user changes the document.
+  Client.prototype.applyClient = function (operation) {
+    this.setState(this.state.applyClient(this, operation));
+  };
+
+  // Call this method with a new operation from the server
+  Client.prototype.applyServer = function (revision, operation) {
+    this.setState(this.state.applyServer(this, revision, operation));
+  };
+
+  Client.prototype.applyOperations = function (head, operations) {
+    this.setState(this.state.applyOperations(this, head, operations));
+  };
+
+  Client.prototype.serverAck = function (revision) {
+    this.setState(this.state.serverAck(this, revision));
+  };
+
+  Client.prototype.serverReconnect = function () {
+    if (typeof this.state.resend === 'function') { this.state.resend(this); }
+  };
+
+  // Transforms a selection from the latest known server state to the current
+  // client state. For example, if we get from the server the information that
+  // another user's cursor is at position 3, but the server hasn't yet received
+  // our newest operation, an insertion of 5 characters at the beginning of the
+  // document, the correct position of the other user's cursor in our current
+  // document is 8.
+  Client.prototype.transformSelection = function (selection) {
+    return this.state.transformSelection(selection);
+  };
+
+  // Override this method.
+  Client.prototype.sendOperation = function (revision, operation) {
+    throw new Error("sendOperation must be defined in child class");
+  };
+
+  // Override this method.
+  Client.prototype.applyOperation = function (operation) {
+    throw new Error("applyOperation must be defined in child class");
+  };
+
+
+  // In the 'Synchronized' state, there is no pending operation that the client
+  // has sent to the server.
+  function Synchronized () {}
+  Client.Synchronized = Synchronized;
+
+  Synchronized.prototype.applyClient = function (client, operation) {
+    // When the user makes an edit, send the operation to the server and
+    // switch to the 'AwaitingConfirm' state
+    client.sendOperation(client.revision, operation);
+    return new AwaitingConfirm(operation);
+  };
+
+  Synchronized.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // When we receive a new operation from the server, the operation can be
+    // simply applied to the current document
+    client.applyOperation(operation);
+    return this;
+  };
+
+  Synchronized.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  // Nothing to do because the latest server state and client state are the same.
+  Synchronized.prototype.transformSelection = function (x) { return x; };
+
+  // Singleton
+  var synchronized_ = new Synchronized();
+
+
+  // In the 'AwaitingConfirm' state, there's one operation the client has sent
+  // to the server and is still waiting for an acknowledgement.
+  function AwaitingConfirm (outstanding) {
+    // Save the pending operation
+    this.outstanding = outstanding;
+  }
+  Client.AwaitingConfirm = AwaitingConfirm;
+
+  AwaitingConfirm.prototype.applyClient = function (client, operation) {
+    // When the user makes an edit, don't send the operation immediately,
+    // instead switch to 'AwaitingWithBuffer' state
+    return new AwaitingWithBuffer(this.outstanding, operation);
+  };
+
+  AwaitingConfirm.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // This is another client's operation. Visualization:
+    //
+    //                   /\
+    // this.outstanding /  \ operation
+    //                 /    \
+    //                 \    /
+    //  pair[1]         \  / pair[0] (new outstanding)
+    //  (can be applied  \/
+    //  to the client's
+    //  current document)
+    var pair = operation.constructor.transform(this.outstanding, operation);
+    client.applyOperation(pair[1]);
+    return new AwaitingConfirm(pair[0]);
+  };
+
+  AwaitingConfirm.prototype.serverAck = function (client, revision) {
+    if (revision - client.revision > 1) {
+      return new Stale(this.outstanding, client, revision).getOperations();
+    }
+    client.revision = revision;
+    // The client's operation has been acknowledged
+    // => switch to synchronized state
+    return synchronized_;
+  };
+
+  AwaitingConfirm.prototype.transformSelection = function (selection) {
+    return selection.transform(this.outstanding);
+  };
+
+  AwaitingConfirm.prototype.resend = function (client) {
+    // The confirm didn't come because the client was disconnected.
+    // Now that it has reconnected, we resend the outstanding operation.
+    client.sendOperation(client.revision, this.outstanding);
+  };
+
+
+  // In the 'AwaitingWithBuffer' state, the client is waiting for an operation
+  // to be acknowledged by the server while buffering the edits the user makes
+  function AwaitingWithBuffer (outstanding, buffer) {
+    // Save the pending operation and the user's edits since then
+    this.outstanding = outstanding;
+    this.buffer = buffer;
+  }
+  Client.AwaitingWithBuffer = AwaitingWithBuffer;
+
+  AwaitingWithBuffer.prototype.applyClient = function (client, operation) {
+    // Compose the user's changes onto the buffer
+    var newBuffer = this.buffer.compose(operation);
+    return new AwaitingWithBuffer(this.outstanding, newBuffer);
+  };
+
+  AwaitingWithBuffer.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // Operation comes from another client
+    //
+    //                       /\
+    //     this.outstanding /  \ operation
+    //                     /    \
+    //                    /\    /
+    //       this.buffer /  \* / pair1[0] (new outstanding)
+    //                  /    \/
+    //                  \    /
+    //          pair2[1] \  / pair2[0] (new buffer)
+    // the transformed    \/
+    // operation -- can
+    // be applied to the
+    // client's current
+    // document
+    //
+    // * pair1[1]
+    var transform = operation.constructor.transform;
+    var pair1 = transform(this.outstanding, operation);
+    var pair2 = transform(this.buffer, pair1[1]);
+    client.applyOperation(pair2[1]);
+    return new AwaitingWithBuffer(pair1[0], pair2[0]);
+  };
+
+  AwaitingWithBuffer.prototype.serverAck = function (client, revision) {
+    if (revision - client.revision > 1) {
+      return new StaleWithBuffer(this.outstanding, this.buffer, client, revision).getOperations();
+    }
+    client.revision = revision;
+    // The pending operation has been acknowledged
+    // => send buffer
+    client.sendOperation(client.revision, this.buffer);
+    return new AwaitingConfirm(this.buffer);
+  };
+
+  AwaitingWithBuffer.prototype.transformSelection = function (selection) {
+    return selection.transform(this.outstanding).transform(this.buffer);
+  };
+
+  AwaitingWithBuffer.prototype.resend = function (client) {
+    // The confirm didn't come because the client was disconnected.
+    // Now that it has reconnected, we resend the outstanding operation.
+    client.sendOperation(client.revision, this.outstanding);
+  };
+
+
+  function Stale(acknowlaged, client, revision) {
+    this.acknowlaged = acknowlaged;
+    this.client = client;
+    this.revision = revision;
+  }
+  Client.Stale = Stale;
+
+  Stale.prototype.applyClient = function (client, operation) {
+    return new StaleWithBuffer(this.acknowlaged, operation, client, this.revision);
+  };
+
+  Stale.prototype.applyServer = function (client, revision, operation) {
+    throw new Error("Ignored server-side change.");
+  };
+
+  Stale.prototype.applyOperations = function (client, head, operations) {
+    var transform = this.acknowlaged.constructor.transform;
+    for (var i = 0; i < operations.length; i++) {
+      var op = ot.TextOperation.fromJSON(operations[i]);
+      var pair = transform(this.acknowlaged, op);
+      client.applyOperation(pair[1]);
+      this.acknowlaged = pair[0];
+    }
+    client.revision = this.revision;
+    return synchronized_;
+  };
+
+  Stale.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  Stale.prototype.transformSelection = function (selection) {
+    return selection;
+  };
+
+  Stale.prototype.getOperations = function () {
+    this.client.getOperations(this.client.revision, this.revision - 1); // acknowlaged is the one at revision
+    return this;
+  };
+
+
+  function StaleWithBuffer(acknowlaged, buffer, client, revision) {
+    this.acknowlaged = acknowlaged;
+    this.buffer = buffer;
+    this.client = client;
+    this.revision = revision;
+  }
+  Client.StaleWithBuffer = StaleWithBuffer;
+
+  StaleWithBuffer.prototype.applyClient = function (client, operation) {
+    var buffer = this.buffer.compose(operation);
+    return new StaleWithBuffer(this.acknowlaged, buffer, client, this.revision);
+  };
+
+  StaleWithBuffer.prototype.applyServer = function (client, revision, operation) {
+    throw new Error("Ignored server-side change.");
+  };
+
+  StaleWithBuffer.prototype.applyOperations = function (client, head, operations) {
+    var transform = this.acknowlaged.constructor.transform;
+    for (var i = 0; i < operations.length; i++) {
+      var op = ot.TextOperation.fromJSON(operations[i]);
+      var pair1 = transform(this.acknowlaged, op);
+      var pair2 = transform(this.buffer, pair1[1]);
+      client.applyOperation(pair2[1]);
+      this.acknowlaged = pair1[0];
+      this.buffer = pair2[0];
+    }
+    client.revision = this.revision;
+    client.sendOperation(client.revision, this.buffer);
+    return new AwaitingConfirm(this.buffer);
+  };
+
+  StaleWithBuffer.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  StaleWithBuffer.prototype.transformSelection = function (selection) {
+    return selection;
+  };
+
+  StaleWithBuffer.prototype.getOperations = function () {
+    this.client.getOperations(this.client.revision, this.revision - 1); // acknowlaged is the one at revision
+    return this;
+  };
+
+
+  return Client;
+
+}(this));
+
+if (typeof module === 'object') {
+  module.exports = ot.Client;
+}
+

lib/ot/editor-socketio-server.js

@@ -0,0 +1,146 @@
+'use strict';
+
+var EventEmitter = require('events').EventEmitter;
+var TextOperation = require('./text-operation');
+var WrappedOperation = require('./wrapped-operation');
+var Server = require('./server');
+var Selection = require('./selection');
+var util = require('util');
+
+var LZString = require('lz-string');
+
+function EditorSocketIOServer(document, operations, docId, mayWrite) {
+    EventEmitter.call(this);
+    Server.call(this, document, operations);
+    this.users = {};
+    this.docId = docId;
+    this.mayWrite = mayWrite || function (_, cb) {
+        cb(true);
+    };
+}
+
+util.inherits(EditorSocketIOServer, Server);
+extend(EditorSocketIOServer.prototype, EventEmitter.prototype);
+
+function extend(target, source) {
+    for (var key in source) {
+        if (source.hasOwnProperty(key)) {
+            target[key] = source[key];
+        }
+    }
+}
+
+EditorSocketIOServer.prototype.addClient = function (socket) {
+    var self = this;
+    socket.join(this.docId);
+    var docOut = {
+        str: this.document,
+        revision: this.operations.length,
+        clients: this.users
+    };
+    socket.emit('doc', LZString.compressToUTF16(JSON.stringify(docOut)));
+    socket.on('operation', function (revision, operation, selection) {
+        operation = LZString.decompressFromUTF16(operation);
+        operation = JSON.parse(operation);
+        self.mayWrite(socket, function (mayWrite) {
+            if (!mayWrite) {
+                console.log("User doesn't have the right to edit.");
+                return;
+            }
+            self.onOperation(socket, revision, operation, selection);
+        });
+    });
+    socket.on('get_operations', function (base, head) {
+        self.onGetOperations(socket, base, head);
+    });
+    socket.on('selection', function (obj) {
+        self.mayWrite(socket, function (mayWrite) {
+            if (!mayWrite) {
+                console.log("User doesn't have the right to edit.");
+                return;
+            }
+            self.updateSelection(socket, obj && Selection.fromJSON(obj));
+        });
+    });
+    socket.on('disconnect', function () {
+        //console.log("Disconnect");
+        socket.leave(self.docId);
+        self.onDisconnect(socket);
+        /*
+        if (socket.manager && socket.manager.sockets.clients(self.docId).length === 0) {
+          self.emit('empty-room');
+        }
+        */
+    });
+};
+
+EditorSocketIOServer.prototype.onOperation = function (socket, revision, operation, selection) {
+    var wrapped;
+    try {
+        wrapped = new WrappedOperation(
+            TextOperation.fromJSON(operation),
+            selection && Selection.fromJSON(selection)
+        );
+    } catch (exc) {
+        console.error("Invalid operation received: " + exc);
+        return;
+    }
+
+    try {
+        var clientId = socket.id;
+        var wrappedPrime = this.receiveOperation(revision, wrapped);
+        //console.log("new operation: " + JSON.stringify(wrapped));
+        this.getClient(clientId).selection = wrappedPrime.meta;
+        revision = this.operations.length;
+        socket.emit('ack', revision);
+        socket.broadcast.in(this.docId).emit(
+            'operation', clientId, revision,
+            wrappedPrime.wrapped.toJSON(), wrappedPrime.meta
+        );
+        this.isDirty = true;
+    } catch (exc) {
+        console.error(exc);
+    }
+};
+
+EditorSocketIOServer.prototype.onGetOperations = function (socket, base, head) {
+    var operations = this.operations.slice(base, head).map(function (op) {
+        return op.wrapped.toJSON();
+    });
+    operations = LZString.compressToUTF16(JSON.stringify(operations));
+    socket.emit('operations', head, operations);
+};
+
+EditorSocketIOServer.prototype.updateSelection = function (socket, selection) {
+    var clientId = socket.id;
+    if (selection) {
+        this.getClient(clientId).selection = selection;
+    } else {
+        delete this.getClient(clientId).selection;
+    }
+    socket.broadcast.to(this.docId).emit('selection', clientId, selection);
+};
+
+EditorSocketIOServer.prototype.setName = function (socket, name) {
+    var clientId = socket.id;
+    this.getClient(clientId).name = name;
+    socket.broadcast.to(this.docId).emit('set_name', clientId, name);
+};
+
+EditorSocketIOServer.prototype.setColor = function (socket, color) {
+    var clientId = socket.id;
+    this.getClient(clientId).color = color;
+    socket.broadcast.to(this.docId).emit('set_color', clientId, color);
+};
+
+EditorSocketIOServer.prototype.getClient = function (clientId) {
+    return this.users[clientId] || (this.users[clientId] = {});
+};
+
+EditorSocketIOServer.prototype.onDisconnect = function (socket) {
+    var clientId = socket.id;
+    delete this.users[clientId];
+    socket.broadcast.to(this.docId).emit('client_left', clientId);
+};
+
+module.exports = EditorSocketIOServer;

lib/ot/index.js

@@ -0,0 +1,8 @@
+exports.version = '0.0.15';
+
+exports.TextOperation        = require('./text-operation');
+exports.SimpleTextOperation  = require('./simple-text-operation');
+exports.Client               = require('./client');
+exports.Server               = require('./server');
+exports.Selection            = require('./selection');
+exports.EditorSocketIOServer = require('./editor-socketio-server');

lib/ot/selection.js

@@ -0,0 +1,117 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.Selection = (function (global) {
+  'use strict';
+
+  var TextOperation = global.ot ? global.ot.TextOperation : require('./text-operation');
+
+  // Range has `anchor` and `head` properties, which are zero-based indices into
+  // the document. The `anchor` is the side of the selection that stays fixed,
+  // `head` is the side of the selection where the cursor is. When both are
+  // equal, the range represents a cursor.
+  function Range (anchor, head) {
+    this.anchor = anchor;
+    this.head = head;
+  }
+
+  Range.fromJSON = function (obj) {
+    return new Range(obj.anchor, obj.head);
+  };
+
+  Range.prototype.equals = function (other) {
+    return this.anchor === other.anchor && this.head === other.head;
+  };
+
+  Range.prototype.isEmpty = function () {
+    return this.anchor === this.head;
+  };
+
+  Range.prototype.transform = function (other) {
+    function transformIndex (index) {
+      var newIndex = index;
+      var ops = other.ops;
+      for (var i = 0, l = other.ops.length; i < l; i++) {
+        if (TextOperation.isRetain(ops[i])) {
+          index -= ops[i];
+        } else if (TextOperation.isInsert(ops[i])) {
+          newIndex += ops[i].length;
+        } else {
+          newIndex -= Math.min(index, -ops[i]);
+          index += ops[i];
+        }
+        if (index < 0) { break; }
+      }
+      return newIndex;
+    }
+
+    var newAnchor = transformIndex(this.anchor);
+    if (this.anchor === this.head) {
+      return new Range(newAnchor, newAnchor);
+    }
+    return new Range(newAnchor, transformIndex(this.head));
+  };
+
+  // A selection is basically an array of ranges. Every range represents a real
+  // selection or a cursor in the document (when the start position equals the
+  // end position of the range). The array must not be empty.
+  function Selection (ranges) {
+    this.ranges = ranges || [];
+  }
+
+  Selection.Range = Range;
+
+  // Convenience method for creating selections only containing a single cursor
+  // and no real selection range.
+  Selection.createCursor = function (position) {
+    return new Selection([new Range(position, position)]);
+  };
+
+  Selection.fromJSON = function (obj) {
+    var objRanges = obj.ranges || obj;
+    for (var i = 0, ranges = []; i < objRanges.length; i++) {
+      ranges[i] = Range.fromJSON(objRanges[i]);
+    }
+    return new Selection(ranges);
+  };
+
+  Selection.prototype.equals = function (other) {
+    if (this.position !== other.position) { return false; }
+    if (this.ranges.length !== other.ranges.length) { return false; }
+    // FIXME: Sort ranges before comparing them?
+    for (var i = 0; i < this.ranges.length; i++) {
+      if (!this.ranges[i].equals(other.ranges[i])) { return false; }
+    }
+    return true;
+  };
+
+  Selection.prototype.somethingSelected = function () {
+    for (var i = 0; i < this.ranges.length; i++) {
+      if (!this.ranges[i].isEmpty()) { return true; }
+    }
+    return false;
+  };
+
+  // Return the more current selection information.
+  Selection.prototype.compose = function (other) {
+    return other;
+  };
+
+  // Update the selection with respect to an operation.
+  Selection.prototype.transform = function (other) {
+    for (var i = 0, newRanges = []; i < this.ranges.length; i++) {
+      newRanges[i] = this.ranges[i].transform(other);
+    }
+    return new Selection(newRanges);
+  };
+
+  return Selection;
+
+}(this));
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.Selection;
+}

lib/ot/server.js

@@ -0,0 +1,46 @@
+if (typeof ot === 'undefined') {
+  var ot = {};
+}
+
+ot.Server = (function (global) {
+  'use strict';
+
+  // Constructor. Takes the current document as a string and optionally the array
+  // of all operations.
+  function Server (document, operations) {
+    this.document = document;
+    this.operations = operations || [];
+  }
+
+  // Call this method whenever you receive an operation from a client.
+  Server.prototype.receiveOperation = function (revision, operation) {
+    if (revision < 0 || this.operations.length < revision) {
+      throw new Error("operation revision not in history");
+    }
+    // Find all operations that the client didn't know of when it sent the
+    // operation ...
+    var concurrentOperations = this.operations.slice(revision);
+
+    // ... and transform the operation against all these operations ...
+    var transform = operation.constructor.transform;
+    for (var i = 0; i < concurrentOperations.length; i++) {
+      operation = transform(operation, concurrentOperations[i])[0];
+    }
+
+    // ... and apply that on the document.
+    this.document = operation.apply(this.document);
+    // Store operation in history.
+    this.operations.push(operation);
+
+    // It's the caller's responsibility to send the operation to all connected
+    // clients and an acknowledgement to the creator.
+    return operation;
+  };
+
+  return Server;
+
+}(this));
+
+if (typeof module === 'object') {
+  module.exports = ot.Server;
+}

lib/ot/simple-text-operation.js

@@ -0,0 +1,188 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.SimpleTextOperation = (function (global) {
+
+  var TextOperation = global.ot ? global.ot.TextOperation : require('./text-operation');
+
+  function SimpleTextOperation () {}
+
+
+  // Insert the string `str` at the zero-based `position` in the document.
+  function Insert (str, position) {
+    if (!this || this.constructor !== SimpleTextOperation) {
+      // => function was called without 'new'
+      return new Insert(str, position);
+    }
+    this.str = str;
+    this.position = position;
+  }
+
+  Insert.prototype = new SimpleTextOperation();
+  SimpleTextOperation.Insert = Insert;
+
+  Insert.prototype.toString = function () {
+    return 'Insert(' + JSON.stringify(this.str) + ', ' + this.position + ')';
+  };
+
+  Insert.prototype.equals = function (other) {
+    return other instanceof Insert &&
+      this.str === other.str &&
+      this.position === other.position;
+  };
+
+  Insert.prototype.apply = function (doc) {
+    return doc.slice(0, this.position) + this.str + doc.slice(this.position);
+  };
+
+
+  // Delete `count` many characters at the zero-based `position` in the document.
+  function Delete (count, position) {
+    if (!this || this.constructor !== SimpleTextOperation) {
+      return new Delete(count, position);
+    }
+    this.count = count;
+    this.position = position;
+  }
+
+  Delete.prototype = new SimpleTextOperation();
+  SimpleTextOperation.Delete = Delete;
+
+  Delete.prototype.toString = function () {
+    return 'Delete(' + this.count + ', ' + this.position + ')';
+  };
+
+  Delete.prototype.equals = function (other) {
+    return other instanceof Delete &&
+      this.count === other.count &&
+      this.position === other.position;
+  };
+
+  Delete.prototype.apply = function (doc) {
+    return doc.slice(0, this.position) + doc.slice(this.position + this.count);
+  };
+
+
+  // An operation that does nothing. This is needed for the result of the
+  // transformation of two deletions of the same character.
+  function Noop () {
+    if (!this || this.constructor !== SimpleTextOperation) { return new Noop(); }
+  }
+
+  Noop.prototype = new SimpleTextOperation();
+  SimpleTextOperation.Noop = Noop;
+
+  Noop.prototype.toString = function () {
+    return 'Noop()';
+  };
+
+  Noop.prototype.equals = function (other) { return other instanceof Noop; };
+
+  Noop.prototype.apply = function (doc) { return doc; };
+
+  var noop = new Noop();
+
+
+  SimpleTextOperation.transform = function (a, b) {
+    if (a instanceof Noop || b instanceof Noop) { return [a, b]; }
+
+    if (a instanceof Insert && b instanceof Insert) {
+      if (a.position < b.position || (a.position === b.position && a.str < b.str)) {
+        return [a, new Insert(b.str, b.position + a.str.length)];
+      }
+      if (a.position > b.position || (a.position === b.position && a.str > b.str)) {
+        return [new Insert(a.str, a.position + b.str.length), b];
+      }
+      return [noop, noop];
+    }
+
+    if (a instanceof Insert && b instanceof Delete) {
+      if (a.position <= b.position) {
+        return [a, new Delete(b.count, b.position + a.str.length)];
+      }
+      if (a.position >= b.position + b.count) {
+        return [new Insert(a.str, a.position - b.count), b];
+      }
+      // Here, we have to delete the inserted string of operation a.
+      // That doesn't preserve the intention of operation a, but it's the only
+      // thing we can do to get a valid transform function.
+      return [noop, new Delete(b.count + a.str.length, b.position)];
+    }
+
+    if (a instanceof Delete && b instanceof Insert) {
+      if (a.position >= b.position) {
+        return [new Delete(a.count, a.position + b.str.length), b];
+      }
+      if (a.position + a.count <= b.position) {
+        return [a, new Insert(b.str, b.position - a.count)];
+      }
+      // Same problem as above. We have to delete the string that was inserted
+      // in operation b.
+      return [new Delete(a.count + b.str.length, a.position), noop];
+    }
+
+    if (a instanceof Delete && b instanceof Delete) {
+      if (a.position === b.position) {
+        if (a.count === b.count) {
+          return [noop, noop];
+        } else if (a.count < b.count) {
+          return [noop, new Delete(b.count - a.count, b.position)];
+        }
+        return [new Delete(a.count - b.count, a.position), noop];
+      }
+      if (a.position < b.position) {
+        if (a.position + a.count <= b.position) {
+          return [a, new Delete(b.count, b.position - a.count)];
+        }
+        if (a.position + a.count >= b.position + b.count) {
+          return [new Delete(a.count - b.count, a.position), noop];
+        }
+        return [
+          new Delete(b.position - a.position, a.position),
+          new Delete(b.position + b.count - (a.position + a.count), a.position)
+        ];
+      }
+      if (a.position > b.position) {
+        if (a.position >= b.position + b.count) {
+          return [new Delete(a.count, a.position - b.count), b];
+        }
+        if (a.position + a.count <= b.position + b.count) {
+          return [noop, new Delete(b.count - a.count, b.position)];
+        }
+        return [
+          new Delete(a.position + a.count - (b.position + b.count), b.position),
+          new Delete(a.position - b.position, b.position)
+        ];
+      }
+    }
+  };
+
+  // Convert a normal, composable `TextOperation` into an array of
+  // `SimpleTextOperation`s.
+  SimpleTextOperation.fromTextOperation = function (operation) {
+    var simpleOperations = [];
+    var index = 0;
+    for (var i = 0; i < operation.ops.length; i++) {
+      var op = operation.ops[i];
+      if (TextOperation.isRetain(op)) {
+        index += op;
+      } else if (TextOperation.isInsert(op)) {
+        simpleOperations.push(new Insert(op, index));
+        index += op.length;
+      } else {
+        simpleOperations.push(new Delete(Math.abs(op), index));
+      }
+    }
+    return simpleOperations;
+  };
+
+
+  return SimpleTextOperation;
+})(this);
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.SimpleTextOperation;
+}

lib/ot/text-operation.js

@@ -0,0 +1,530 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.TextOperation = (function () {
+  'use strict';
+
+  // Constructor for new operations.
+  function TextOperation () {
+    if (!this || this.constructor !== TextOperation) {
+      // => function was called without 'new'
+      return new TextOperation();
+    }
+
+    // When an operation is applied to an input string, you can think of this as
+    // if an imaginary cursor runs over the entire string and skips over some
+    // parts, deletes some parts and inserts characters at some positions. These
+    // actions (skip/delete/insert) are stored as an array in the "ops" property.
+    this.ops = [];
+    // An operation's baseLength is the length of every string the operation
+    // can be applied to.
+    this.baseLength = 0;
+    // The targetLength is the length of every string that results from applying
+    // the operation on a valid input string.
+    this.targetLength = 0;
+  }
+
+  TextOperation.prototype.equals = function (other) {
+    if (this.baseLength !== other.baseLength) { return false; }
+    if (this.targetLength !== other.targetLength) { return false; }
+    if (this.ops.length !== other.ops.length) { return false; }
+    for (var i = 0; i < this.ops.length; i++) {
+      if (this.ops[i] !== other.ops[i]) { return false; }
+    }
+    return true;
+  };
+
+  // Operation are essentially lists of ops. There are three types of ops:
+  //
+  // * Retain ops: Advance the cursor position by a given number of characters.
+  //   Represented by positive ints.
+  // * Insert ops: Insert a given string at the current cursor position.
+  //   Represented by strings.
+  // * Delete ops: Delete the next n characters. Represented by negative ints.
+
+  var isRetain = TextOperation.isRetain = function (op) {
+    return typeof op === 'number' && op > 0;
+  };
+
+  var isInsert = TextOperation.isInsert = function (op) {
+    return typeof op === 'string';
+  };
+
+  var isDelete = TextOperation.isDelete = function (op) {
+    return typeof op === 'number' && op < 0;
+  };
+
+
+  // After an operation is constructed, the user of the library can specify the
+  // actions of an operation (skip/insert/delete) with these three builder
+  // methods. They all return the operation for convenient chaining.
+
+  // Skip over a given number of characters.
+  TextOperation.prototype.retain = function (n) {
+    if (typeof n !== 'number') {
+      throw new Error("retain expects an integer");
+    }
+    if (n === 0) { return this; }
+    this.baseLength += n;
+    this.targetLength += n;
+    if (isRetain(this.ops[this.ops.length-1])) {
+      // The last op is a retain op => we can merge them into one op.
+      this.ops[this.ops.length-1] += n;
+    } else {
+      // Create a new op.
+      this.ops.push(n);
+    }
+    return this;
+  };
+
+  // Insert a string at the current position.
+  TextOperation.prototype.insert = function (str) {
+    if (typeof str !== 'string') {
+      throw new Error("insert expects a string");
+    }
+    if (str === '') { return this; }
+    this.targetLength += str.length;
+    var ops = this.ops;
+    if (isInsert(ops[ops.length-1])) {
+      // Merge insert op.
+      ops[ops.length-1] += str;
+    } else if (isDelete(ops[ops.length-1])) {
+      // It doesn't matter when an operation is applied whether the operation
+      // is delete(3), insert("something") or insert("something"), delete(3).
+      // Here we enforce that in this case, the insert op always comes first.
+      // This makes all operations that have the same effect when applied to
+      // a document of the right length equal in respect to the `equals` method.
+      if (isInsert(ops[ops.length-2])) {
+        ops[ops.length-2] += str;
+      } else {
+        ops[ops.length] = ops[ops.length-1];
+        ops[ops.length-2] = str;
+      }
+    } else {
+      ops.push(str);
+    }
+    return this;
+  };
+
+  // Delete a string at the current position.
+  TextOperation.prototype['delete'] = function (n) {
+    if (typeof n === 'string') { n = n.length; }
+    if (typeof n !== 'number') {
+      throw new Error("delete expects an integer or a string");
+    }
+    if (n === 0) { return this; }
+    if (n > 0) { n = -n; }
+    this.baseLength -= n;
+    if (isDelete(this.ops[this.ops.length-1])) {
+      this.ops[this.ops.length-1] += n;
+    } else {
+      this.ops.push(n);
+    }
+    return this;
+  };
+
+  // Tests whether this operation has no effect.
+  TextOperation.prototype.isNoop = function () {
+    return this.ops.length === 0 || (this.ops.length === 1 && isRetain(this.ops[0]));
+  };
+
+  // Pretty printing.
+  TextOperation.prototype.toString = function () {
+    // map: build a new array by applying a function to every element in an old
+    // array.
+    var map = Array.prototype.map || function (fn) {
+      var arr = this;
+      var newArr = [];
+      for (var i = 0, l = arr.length; i < l; i++) {
+        newArr[i] = fn(arr[i]);
+      }
+      return newArr;
+    };
+    return map.call(this.ops, function (op) {
+      if (isRetain(op)) {
+        return "retain " + op;
+      } else if (isInsert(op)) {
+        return "insert '" + op + "'";
+      } else {
+        return "delete " + (-op);
+      }
+    }).join(', ');
+  };
+
+  // Converts operation into a JSON value.
+  TextOperation.prototype.toJSON = function () {
+    return this.ops;
+  };
+
+  // Converts a plain JS object into an operation and validates it.
+  TextOperation.fromJSON = function (ops) {
+    var o = new TextOperation();
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        o.retain(op);
+      } else if (isInsert(op)) {
+        o.insert(op);
+      } else if (isDelete(op)) {
+        o['delete'](op);
+      } else {
+        throw new Error("unknown operation: " + JSON.stringify(op));
+      }
+    }
+    return o;
+  };
+
+  // Apply an operation to a string, returning a new string. Throws an error if
+  // there's a mismatch between the input string and the operation.
+  TextOperation.prototype.apply = function (str) {
+    var operation = this;
+    if (str.length !== operation.baseLength) {
+      throw new Error("The operation's base length must be equal to the string's length.");
+    }
+    var newStr = [], j = 0;
+    var strIndex = 0;
+    var ops = this.ops;
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        if (strIndex + op > str.length) {
+          throw new Error("Operation can't retain more characters than are left in the string.");
+        }
+        // Copy skipped part of the old string.
+        newStr[j++] = str.slice(strIndex, strIndex + op);
+        strIndex += op;
+      } else if (isInsert(op)) {
+        // Insert string.
+        newStr[j++] = op;
+      } else { // delete op
+        strIndex -= op;
+      }
+    }
+    if (strIndex !== str.length) {
+      throw new Error("The operation didn't operate on the whole string.");
+    }
+    return newStr.join('');
+  };
+
+  // Computes the inverse of an operation. The inverse of an operation is the
+  // operation that reverts the effects of the operation, e.g. when you have an
+  // operation 'insert("hello "); skip(6);' then the inverse is 'delete("hello ");
+  // skip(6);'. The inverse should be used for implementing undo.
+  TextOperation.prototype.invert = function (str) {
+    var strIndex = 0;
+    var inverse = new TextOperation();
+    var ops = this.ops;
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        inverse.retain(op);
+        strIndex += op;
+      } else if (isInsert(op)) {
+        inverse['delete'](op.length);
+      } else { // delete op
+        inverse.insert(str.slice(strIndex, strIndex - op));
+        strIndex -= op;
+      }
+    }
+    return inverse;
+  };
+
+  // Compose merges two consecutive operations into one operation, that
+  // preserves the changes of both. Or, in other words, for each input string S
+  // and a pair of consecutive operations A and B,
+  // apply(apply(S, A), B) = apply(S, compose(A, B)) must hold.
+  TextOperation.prototype.compose = function (operation2) {
+    var operation1 = this;
+    if (operation1.targetLength !== operation2.baseLength) {
+      throw new Error("The base length of the second operation has to be the target length of the first operation");
+    }
+
+    var operation = new TextOperation(); // the combined operation
+    var ops1 = operation1.ops, ops2 = operation2.ops; // for fast access
+    var i1 = 0, i2 = 0; // current index into ops1 respectively ops2
+    var op1 = ops1[i1++], op2 = ops2[i2++]; // current ops
+    while (true) {
+      // Dispatch on the type of op1 and op2
+      if (typeof op1 === 'undefined' && typeof op2 === 'undefined') {
+        // end condition: both ops1 and ops2 have been processed
+        break;
+      }
+
+      if (isDelete(op1)) {
+        operation['delete'](op1);
+        op1 = ops1[i1++];
+        continue;
+      }
+      if (isInsert(op2)) {
+        operation.insert(op2);
+        op2 = ops2[i2++];
+        continue;
+      }
+
+      if (typeof op1 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too short.");
+      }
+      if (typeof op2 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too long.");
+      }
+
+      if (isRetain(op1) && isRetain(op2)) {
+        if (op1 > op2) {
+          operation.retain(op2);
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          operation.retain(op1);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation.retain(op1);
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+      } else if (isInsert(op1) && isDelete(op2)) {
+        if (op1.length > -op2) {
+          op1 = op1.slice(-op2);
+          op2 = ops2[i2++];
+        } else if (op1.length === -op2) {
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          op2 = op2 + op1.length;
+          op1 = ops1[i1++];
+        }
+      } else if (isInsert(op1) && isRetain(op2)) {
+        if (op1.length > op2) {
+          operation.insert(op1.slice(0, op2));
+          op1 = op1.slice(op2);
+          op2 = ops2[i2++];
+        } else if (op1.length === op2) {
+          operation.insert(op1);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation.insert(op1);
+          op2 = op2 - op1.length;
+          op1 = ops1[i1++];
+        }
+      } else if (isRetain(op1) && isDelete(op2)) {
+        if (op1 > -op2) {
+          operation['delete'](op2);
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (op1 === -op2) {
+          operation['delete'](op2);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation['delete'](op1);
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+      } else {
+        throw new Error(
+          "This shouldn't happen: op1: " +
+          JSON.stringify(op1) + ", op2: " +
+          JSON.stringify(op2)
+        );
+      }
+    }
+    return operation;
+  };
+
+  function getSimpleOp (operation, fn) {
+    var ops = operation.ops;
+    var isRetain = TextOperation.isRetain;
+    switch (ops.length) {
+    case 1:
+      return ops[0];
+    case 2:
+      return isRetain(ops[0]) ? ops[1] : (isRetain(ops[1]) ? ops[0] : null);
+    case 3:
+      if (isRetain(ops[0]) && isRetain(ops[2])) { return ops[1]; }
+    }
+    return null;
+  }
+
+  function getStartIndex (operation) {
+    if (isRetain(operation.ops[0])) { return operation.ops[0]; }
+    return 0;
+  }
+
+  // When you use ctrl-z to undo your latest changes, you expect the program not
+  // to undo every single keystroke but to undo your last sentence you wrote at
+  // a stretch or the deletion you did by holding the backspace key down. This
+  // This can be implemented by composing operations on the undo stack. This
+  // method can help decide whether two operations should be composed. It
+  // returns true if the operations are consecutive insert operations or both
+  // operations delete text at the same position. You may want to include other
+  // factors like the time since the last change in your decision.
+  TextOperation.prototype.shouldBeComposedWith = function (other) {
+    if (this.isNoop() || other.isNoop()) { return true; }
+
+    var startA = getStartIndex(this), startB = getStartIndex(other);
+    var simpleA = getSimpleOp(this), simpleB = getSimpleOp(other);
+    if (!simpleA || !simpleB) { return false; }
+
+    if (isInsert(simpleA) && isInsert(simpleB)) {
+      return startA + simpleA.length === startB;
+    }
+
+    if (isDelete(simpleA) && isDelete(simpleB)) {
+      // there are two possibilities to delete: with backspace and with the
+      // delete key.
+      return (startB - simpleB === startA) || startA === startB;
+    }
+
+    return false;
+  };
+
+  // Decides whether two operations should be composed with each other
+  // if they were inverted, that is
+  // `shouldBeComposedWith(a, b) = shouldBeComposedWithInverted(b^{-1}, a^{-1})`.
+  TextOperation.prototype.shouldBeComposedWithInverted = function (other) {
+    if (this.isNoop() || other.isNoop()) { return true; }
+
+    var startA = getStartIndex(this), startB = getStartIndex(other);
+    var simpleA = getSimpleOp(this), simpleB = getSimpleOp(other);
+    if (!simpleA || !simpleB) { return false; }
+
+    if (isInsert(simpleA) && isInsert(simpleB)) {
+      return startA + simpleA.length === startB || startA === startB;
+    }
+
+    if (isDelete(simpleA) && isDelete(simpleB)) {
+      return startB - simpleB === startA;
+    }
+
+    return false;
+  };
+
+  // Transform takes two operations A and B that happened concurrently and
+  // produces two operations A' and B' (in an array) such that
+  // `apply(apply(S, A), B') = apply(apply(S, B), A')`. This function is the
+  // heart of OT.
+  TextOperation.transform = function (operation1, operation2) {
+    if (operation1.baseLength !== operation2.baseLength) {
+      throw new Error("Both operations have to have the same base length");
+    }
+
+    var operation1prime = new TextOperation();
+    var operation2prime = new TextOperation();
+    var ops1 = operation1.ops, ops2 = operation2.ops;
+    var i1 = 0, i2 = 0;
+    var op1 = ops1[i1++], op2 = ops2[i2++];
+    while (true) {
+      // At every iteration of the loop, the imaginary cursor that both
+      // operation1 and operation2 have that operates on the input string must
+      // have the same position in the input string.
+
+      if (typeof op1 === 'undefined' && typeof op2 === 'undefined') {
+        // end condition: both ops1 and ops2 have been processed
+        break;
+      }
+
+      // next two cases: one or both ops are insert ops
+      // => insert the string in the corresponding prime operation, skip it in
+      // the other one. If both op1 and op2 are insert ops, prefer op1.
+      if (isInsert(op1)) {
+        operation1prime.insert(op1);
+        operation2prime.retain(op1.length);
+        op1 = ops1[i1++];
+        continue;
+      }
+      if (isInsert(op2)) {
+        operation1prime.retain(op2.length);
+        operation2prime.insert(op2);
+        op2 = ops2[i2++];
+        continue;
+      }
+
+      if (typeof op1 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too short.");
+      }
+      if (typeof op2 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too long.");
+      }
+
+      var minl;
+      if (isRetain(op1) && isRetain(op2)) {
+        // Simple case: retain/retain
+        if (op1 > op2) {
+          minl = op2;
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          minl = op2;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = op1;
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+        operation1prime.retain(minl);
+        operation2prime.retain(minl);
+      } else if (isDelete(op1) && isDelete(op2)) {
+        // Both operations delete the same string at the same position. We don't
+        // need to produce any operations, we just skip over the delete ops and
+        // handle the case that one operation deletes more than the other.
+        if (-op1 > -op2) {
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+      // next two cases: delete/retain and retain/delete
+      } else if (isDelete(op1) && isRetain(op2)) {
+        if (-op1 > op2) {
+          minl = op2;
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (-op1 === op2) {
+          minl = op2;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = -op1;
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+        operation1prime['delete'](minl);
+      } else if (isRetain(op1) && isDelete(op2)) {
+        if (op1 > -op2) {
+          minl = -op2;
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (op1 === -op2) {
+          minl = op1;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = op1;
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+        operation2prime['delete'](minl);
+      } else {
+        throw new Error("The two operations aren't compatible");
+      }
+    }
+
+    return [operation1prime, operation2prime];
+  };
+
+  return TextOperation;
+
+}());
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.TextOperation;
+}

lib/ot/wrapped-operation.js

@@ -0,0 +1,80 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.WrappedOperation = (function (global) {
+  'use strict';
+
+  // A WrappedOperation contains an operation and corresponing metadata.
+  function WrappedOperation (operation, meta) {
+    this.wrapped = operation;
+    this.meta    = meta;
+  }
+
+  WrappedOperation.prototype.apply = function () {
+    return this.wrapped.apply.apply(this.wrapped, arguments);
+  };
+
+  WrappedOperation.prototype.invert = function () {
+    var meta = this.meta;
+    return new WrappedOperation(
+      this.wrapped.invert.apply(this.wrapped, arguments),
+      meta && typeof meta === 'object' && typeof meta.invert === 'function' ?
+        meta.invert.apply(meta, arguments) : meta
+    );
+  };
+
+  // Copy all properties from source to target.
+  function copy (source, target) {
+    for (var key in source) {
+      if (source.hasOwnProperty(key)) {
+        target[key] = source[key];
+      }
+    }
+  }
+
+  function composeMeta (a, b) {
+    if (a && typeof a === 'object') {
+      if (typeof a.compose === 'function') { return a.compose(b); }
+      var meta = {};
+      copy(a, meta);
+      copy(b, meta);
+      return meta;
+    }
+    return b;
+  }
+
+  WrappedOperation.prototype.compose = function (other) {
+    return new WrappedOperation(
+      this.wrapped.compose(other.wrapped),
+      composeMeta(this.meta, other.meta)
+    );
+  };
+
+  function transformMeta (meta, operation) {
+    if (meta && typeof meta === 'object') {
+      if (typeof meta.transform === 'function') {
+        return meta.transform(operation);
+      }
+    }
+    return meta;
+  }
+
+  WrappedOperation.transform = function (a, b) {
+    var transform = a.wrapped.constructor.transform;
+    var pair = transform(a.wrapped, b.wrapped);
+    return [
+      new WrappedOperation(pair[0], transformMeta(a.meta, b.wrapped)),
+      new WrappedOperation(pair[1], transformMeta(b.meta, a.wrapped))
+    ];
+  };
+
+  return WrappedOperation;
+
+}(this));
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.WrappedOperation;
+}

lib/realtime.js

@@ -16,6 +16,9 @@ var moment = require('moment');
 var config = require("../config.js");
 var logger = require("./logger.js");
 
+//ot
+var ot = require("./ot/index.js");
+
 //others
 var db = require("./db.js");
 var Note = require("./note.js");
@@ -60,28 +63,41 @@ function secure(socket, next) {
     }
 }
 
+function emitCheck(note) {
+    var out = {
+        updatetime: note.updatetime
+    };
+    for (var i = 0, l = note.socks.length; i < l; i++) {
+        var sock = note.socks[i];
+        sock.emit('check', out);
+    };
+}
+
 //actions
 var users = {};
 var notes = {};
 var updater = setInterval(function () {
     async.each(Object.keys(notes), function (key, callback) {
         var note = notes[key];
-        if (note.isDirty) {
+        if (note.server.isDirty) {
             if (config.debug)
                 logger.info("updater found dirty note: " + key);
-            var body = LZString.decompressFromUTF16(note.body);
+            var body = note.server.document;
             var title = Note.getNoteTitle(body);
             title = LZString.compressToBase64(title);
             body = LZString.compressToBase64(body);
-            db.saveToDB(key, title, body,
+            db.saveToDB(key, title, body, function (err, result) {
-                function (err, result) {});
+                if (err) return;
-            note.isDirty = false;
+                note.server.isDirty = false;
+                note.updatetime = Date.now();
+                emitCheck(note);
+            });
         }
         callback();
     }, function (err) {
         if (err) return logger.error('updater error', err);
     });
-}, 5000);
+}, 1000);
 
 function getStatus(callback) {
     db.countFromDB(function (err, data) {
@@ -189,9 +205,6 @@ function emitRefresh(socket) {
     socket.emit('refresh', {
         owner: note.owner,
         permission: note.permission,
-        body: note.body,
-        otk: note.otk,
-        hash: note.hash,
         updatetime: note.updatetime
     });
 }
@@ -202,8 +215,13 @@ var isDisconnectBusy = false;
 var disconnectSocketQueue = [];
 
 function finishConnection(socket, notename) {
-    notes[notename].users[socket.id] = users[socket.id];
+    var note = notes[notename];
-    notes[notename].socks.push(socket);
+    note.users[socket.id] = users[socket.id];
+    note.socks.push(socket);
+    note.server.addClient(socket);
+    note.server.setName(socket, users[socket.id].name);
+    note.server.setColor(socket, users[socket.id].color);
+
     emitOnlineUsers(socket);
     emitRefresh(socket);
 
@@ -260,18 +278,16 @@ function startConnection(socket) {
                     return;
                 }
                 var body = LZString.decompressFromBase64(data.rows[0].content);
-                body = LZString.compressToUTF16(body);
+                //body = LZString.compressToUTF16(body);
                 var updatetime = data.rows[0].update_time;
+                var server = new ot.EditorSocketIOServer(body, [], notename, ifMayEdit);
                 notes[notename] = {
                     owner: owner,
                     permission: note.permission,
                     socks: [],
-                    body: body,
-                    isDirty: false,
                     users: {},
-                    otk: shortId.generate(),
+                    updatetime: moment(updatetime).valueOf(),
-                    hash: md5(body),
+                    server: server
-                    updatetime: moment(updatetime).valueOf()
                 };
                 finishConnection(socket, notename);
             });
@@ -294,17 +310,18 @@ function disconnect(socket) {
     if (users[socket.id]) {
         delete users[socket.id];
     }
-    if (notes[notename]) {
+    var note = notes[notename];
-        delete notes[notename].users[socket.id];
+    if (note) {
+        delete note.users[socket.id];
         do {
-            var index = notes[notename].socks.indexOf(socket);
+            var index = note.socks.indexOf(socket);
             if (index != -1) {
-                notes[notename].socks.splice(index, 1);
+                note.socks.splice(index, 1);
             }
         } while (index != -1);
-        if (Object.keys(notes[notename].users).length <= 0) {
+        if (Object.keys(note.users).length <= 0) {
-            if (notes[notename].isDirty) {
+            if (note.server.isDirty) {
-                var body = LZString.decompressFromUTF16(notes[notename].body);
+                var body = note.server.document;
                 var title = Note.getNoteTitle(body);
                 title = LZString.compressToBase64(title);
                 body = LZString.compressToBase64(body);
@@ -363,20 +380,20 @@ function updateUserData(socket, user) {
     if (socket.request.user && socket.request.user.logged_in) {
         var profile = JSON.parse(socket.request.user.profile);
         var photo = null;
-        switch(profile.provider) {
+        switch (profile.provider) {
-            case "facebook":
+        case "facebook":
-                photo = 'https://graph.facebook.com/' + profile.id + '/picture';
+            photo = 'https://graph.facebook.com/' + profile.id + '/picture';
-                break;
+            break;
-            case "twitter":
+        case "twitter":
-                photo = profile.photos[0].value;
+            photo = profile.photos[0].value;
-                break;
+            break;
-            case "github":
+        case "github":
-                photo = 'https://avatars.githubusercontent.com/u/' + profile.id + '?s=48';
+            photo = 'https://avatars.githubusercontent.com/u/' + profile.id + '?s=48';
-                break;
+            break;
-            case "dropbox":
+        case "dropbox":
-                //no image api provided, use gravatar
+            //no image api provided, use gravatar
-                photo = 'https://www.gravatar.com/avatar/' + md5(profile.emails[0].value);
+            photo = 'https://www.gravatar.com/avatar/' + md5(profile.emails[0].value);
-                break;
+            break;
         }
         user.photo = photo;
         user.name = profile.displayName || profile.username;
@@ -389,6 +406,29 @@ function updateUserData(socket, user) {
     }
 }
 
+function ifMayEdit(socket, callback) {
+    var notename = getNotenameFromSocket(socket);
+    if (!notename || !notes[notename]) return;
+    var note = notes[notename];
+    var mayEdit = true;
+    switch (note.permission) {
+    case "freely":
+        //not blocking anyone
+        break;
+    case "editable":
+        //only login user can change
+        if (!socket.request.user || !socket.request.user.logged_in)
+            mayEdit = false;
+        break;
+    case "locked":
+        //only owner can change
+        if (note.owner != socket.request.user._id)
+            mayEdit = false;
+        break;
+    }
+    callback(mayEdit);
+}
+
 function connection(socket) {
     //split notename from socket
     var notename = getNotenameFromSocket(socket);
@@ -442,30 +482,6 @@ function connection(socket) {
         emitRefresh(socket);
     });
 
-    //received client data updated
-    socket.on('update', function (body_) {
-        var notename = getNotenameFromSocket(socket);
-        if (!notename || !notes[notename]) return;
-        if (config.debug)
-            logger.info('SERVER received [' + notename + '] data updated: ' + socket.id);
-        var note = notes[notename];
-        if (note.body != body_) {
-            note.body = body_;
-            note.hash = md5(body_);
-            note.updatetime = Date.now();
-            note.isDirty = true;
-        }
-        var out = {
-            id: socket.id,
-            hash: note.hash,
-            updatetime: note.updatetime
-        };
-        for (var i = 0, l = note.socks.length; i < l; i++) {
-            var sock = note.socks[i];
-            sock.emit('check', out);
-        };
-    });
-
     //received user status
     socket.on('user status', function (data) {
         var notename = getNotenameFromSocket(socket);
@@ -591,67 +607,6 @@ function connection(socket) {
         disconnectSocketQueue.push(socket);
         disconnect(socket);
     });
-
-    //when received client change data request
-    socket.on('change', function (op) {
-        var notename = getNotenameFromSocket(socket);
-        if (!notename || !notes[notename]) return;
-        var note = notes[notename];
-        switch (note.permission) {
-        case "freely":
-            //not blocking anyone
-            break;
-        case "editable":
-            //only login user can change
-            if (!socket.request.user || !socket.request.user.logged_in)
-                return;
-            break;
-        case "locked":
-            //only owner can change
-            if (note.owner != socket.request.user._id)
-                return;
-            break;
-        }
-        op = LZString.decompressFromUTF16(op);
-        if (op)
-            op = JSON.parse(op);
-        else
-            return;
-        if (config.debug)
-            logger.info('SERVER received [' + notename + '] data changed: ' + socket.id + ', op:' + JSON.stringify(op));
-        switch (op.origin) {
-        case '+input':
-        case '+delete':
-        case '+transpose':
-        case 'paste':
-        case 'cut':
-        case 'undo':
-        case 'redo':
-        case 'drag':
-        case '*compose':
-        case 'case':
-        case '+insert':
-        case '+insertLine':
-        case '+swapLine':
-        case '+joinLines':
-        case '+duplicateLine':
-        case '+sortLines':
-            op.id = socket.id;
-            op.otk = note.otk;
-            op.nextotk = note.otk = shortId.generate();
-            var stringop = JSON.stringify(op);
-            var compressstringop = LZString.compressToUTF16(stringop);
-            for (var i = 0, l = note.socks.length; i < l; i++) {
-                var sock = note.socks[i];
-                if (config.debug)
-                    logger.info('SERVER emit sync data out [' + notename + ']: ' + sock.id + ', op:' + stringop);
-                sock.emit('change', compressstringop);
-            };
-            break;
-        default:
-            logger.info('SERVER received uncaught [' + notename + '] data changed: ' + socket.id + ', op:' + JSON.stringify(op));
-        }
-    });
 }
 
 module.exports = realtime;

public/js/index.js

@@ -386,7 +386,10 @@ $(window).resize(function () {
 });
 //when page unload
 $(window).unload(function () {
-    emitUpdate();
+    //na
+});
+$(window).error(function () {
+    setNeedRefresh();
 });
 
 //when page hash change
@@ -898,21 +901,9 @@ socket.on('version', function (data) {
         setNeedRefresh();
 });
 socket.on('check', function (data) {
-    if (data.id == socket.id) {
+    lastchangetime = data.updatetime;
-        lastchangetime = data.updatetime;
+    lastchangeui = ui.infobar.lastchange;
-        lastchangeui = ui.infobar.lastchange;
+    updateLastChange();
-        updateLastChange();
-        return;
-    }
-    var currentHash = md5(LZString.compressToUTF16(editor.getValue()));
-    var hashMismatch = (currentHash != data.hash);
-    if (hashMismatch)
-        socket.emit('refresh');
-    else {
-        lastchangetime = data.updatetime;
-        lastchangeui = ui.infobar.lastchange;
-        updateLastChange();
-    }
 });
 socket.on('permission', function (data) {
     permission = data.permission;
@@ -922,26 +913,46 @@ var otk = null;
 var owner = null;
 var permission = null;
 socket.on('refresh', function (data) {
-    var currentHash = md5(LZString.compressToUTF16(editor.getValue()));
-    var hashMismatch = (currentHash != data.hash);
-    saveInfo();
-
     otk = data.otk;
     owner = data.owner;
     permission = data.permission;
+    lastchangetime = data.updatetime;
+    lastchangeui = ui.infobar.lastchange;
+    updateLastChange();
+    checkPermission();
+});
 
-    if (hashMismatch) {
+var EditorClient = ot.EditorClient;
-        var body = data.body;
+var SocketIOAdapter = ot.SocketIOAdapter;
-        body = LZString.decompressFromUTF16(body);
+var CodeMirrorAdapter = ot.CodeMirrorAdapter;
+var cmClient = null;
+
+socket.on('doc', function (obj) {
+    obj = LZString.decompressFromUTF16(obj);
+    obj = JSON.parse(obj);
+    var body = obj.str;
+    var bodyMismatch = (editor.getValue() != body);
+
+    saveInfo();
+    if (bodyMismatch) {
         if (body)
             editor.setValue(body);
         else
             editor.setValue("");
     }
-
+    if (!cmClient) {
-    lastchangetime = data.updatetime;
+        cmClient = window.cmClient = new EditorClient(
-    lastchangeui = ui.infobar.lastchange;
+            obj.revision, obj.clients,
-    updateLastChange();
+            new SocketIOAdapter(socket), new CodeMirrorAdapter(editor)
+        );
+    } else {
+        cmClient.revision = obj.revision;
+        cmClient.initializeClients(obj.clients);
+        if (bodyMismatch) {
+            cmClient.undoManager.undoStack.length = 0;
+            cmClient.undoManager.redoStack.length = 0;
+        }
+    }
 
     if (!loaded) {
         editor.clearHistory();
@@ -963,7 +974,7 @@ socket.on('refresh', function (data) {
         }, 1);
     } else {
         //if current doc is equal to the doc before disconnect
-        if (hashMismatch)
+        if (bodyMismatch)
             editor.clearHistory();
         else {
             if (lastInfo.history)
@@ -972,57 +983,26 @@ socket.on('refresh', function (data) {
         lastInfo.history = null;
     }
 
-    if (hashMismatch)
+    if (bodyMismatch) {
+        isDirty = true;
         updateView();
+    }
 
     if (editor.getOption('readOnly'))
         editor.setOption('readOnly', false);
 
     restoreInfo();
-    checkPermission();
 });
 
-var changeStack = [];
+socket.on('ack', _.debounce(function () {
-var changeBusy = false;
+    isDirty = true;
+    updateView();
+}, finishChangeDelay));
 
-socket.on('change', function (data) {
+socket.on('operation', _.debounce(function () {
-    data = LZString.decompressFromUTF16(data);
+    isDirty = true;
-    data = JSON.parse(data);
+    updateView();
-    changeStack.push(data);
+}, finishChangeDelay));
-    if (!changeBusy)
-        executeChange();
-});
-
-function executeChange() {
-    if (changeStack.length > 0) {
-        changeBusy = true;
-        var data = changeStack.shift();
-        if (data.otk != otk) {
-            var found = false;
-            for (var i = 0, l = changeStack.length; i < l; i++) {
-                if (changeStack[i].otk == otk) {
-                    changeStack.unshift(data);
-                    data = changeStack[i];
-                    found = true;
-                    break;
-                }
-            }
-            if (!found) {
-                socket.emit('refresh');
-                changeBusy = false;
-                return;
-            }
-        }
-        otk = data.nextotk;
-        if (data.id == personalInfo.id)
-            editor.replaceRange(data.text, data.from, data.to, 'self::' + data.origin);
-        else
-            editor.replaceRange(data.text, data.from, data.to, "ignoreHistory");
-        executeChange();
-    } else {
-        changeBusy = false;
-    }
-}
 
 socket.on('online users', function (data) {
     data = LZString.decompressFromUTF16(data);
@@ -1214,7 +1194,7 @@ function renderUserStatusList(list) {
         var item = items[j];
         var userstatus = $(item.elm).find('.ui-user-status');
         var usericon = $(item.elm).find('.ui-user-icon');
-        if(item.values().login && item.values().photo) {
+        if (item.values().login && item.values().photo) {
             usericon.css('background-image', 'url(' + item.values().photo + ')');
             usericon.css('box-shadow', '0px 0px 2px ' + item.values().color);
             //add 1px more to right, make it feel aligned
@@ -1420,6 +1400,7 @@ function buildCursor(user) {
         checkCursorTag(coord, cursortag);
     } else {
         var cursor = $('#' + user.id);
+        var lineDiff = Math.abs(cursor.attr('data-line') - user.cursor.line);
         cursor.attr('data-line', user.cursor.line);
         cursor.attr('data-ch', user.cursor.ch);
 
@@ -1454,65 +1435,31 @@ function buildCursor(user) {
 }
 
 //editor actions
+var ignoreEmitEvents = ['setValue', 'ignoreHistory'];
 editor.on('beforeChange', function (cm, change) {
     if (debug)
         console.debug(change);
-    var self = change.origin.split('self::');
+    var isIgnoreEmitEvent = (ignoreEmitEvents.indexOf(change.origin) != -1);
-    if (self.length == 2) {
+    if (!isIgnoreEmitEvent) {
-        change.origin = self[1];
+        switch (permission) {
-        self = true;
+        case "freely":
-    } else {
+            //na
-        self = false;
+            break;
-    }
+        case "editable":
-    if (self) {
+            if (!personalInfo.login) {
-        change.canceled = true;
+                change.canceled = true;
-    } else {
+                $('.signin-modal').modal('show');
-        var isIgnoreEmitEvent = (ignoreEmitEvents.indexOf(change.origin) != -1);
-        if (!isIgnoreEmitEvent) {
-            switch (permission) {
-            case "freely":
-                //na
-                break;
-            case "editable":
-                if (!personalInfo.login) {
-                    change.canceled = true;
-                    $('.signin-modal').modal('show');
-                }
-                break;
-            case "locked":
-                if (personalInfo.userid != owner) {
-                    change.canceled = true;
-                    $('.locked-modal').modal('show');
-                }
-                break;
             }
+            break;
+        case "locked":
+            if (personalInfo.userid != owner) {
+                change.canceled = true;
+                $('.locked-modal').modal('show');
+            }
+            break;
         }
     }
 });
-
-var ignoreEmitEvents = ['setValue', 'ignoreHistory'];
-editor.on('change', function (i, op) {
-    if (debug)
-        console.debug(op);
-    var isIgnoreEmitEvent = (ignoreEmitEvents.indexOf(op.origin) != -1);
-    if (!isIgnoreEmitEvent) {
-        var out = {
-            text: op.text,
-            from: op.from,
-            to: op.to,
-            origin: op.origin
-        };
-        socket.emit('change', LZString.compressToUTF16(JSON.stringify(out)));
-    }
-    isDirty = true;
-    clearTimeout(finishChangeTimer);
-    finishChangeTimer = setTimeout(function () {
-        if (!isIgnoreEmitEvent)
-            finishChange(true);
-        else
-            finishChange(false);
-    }, finishChangeDelay);
-});
 editor.on('focus', function (cm) {
     for (var i = 0; i < onlineUsers.length; i++) {
         if (onlineUsers[i].id == personalInfo.id) {
@@ -1617,24 +1564,15 @@ function restoreInfo() {
 var finishChangeTimer = null;
 
 function finishChange(emit) {
-    if (emit)
-        emitUpdate();
     updateView();
 }
 
-function emitUpdate() {
-    var value = editor.getValue();
-    socket.emit('update', LZString.compressToUTF16(value));
-}
-
 var lastResult = null;
 
 function updateView() {
     if (currentMode == modeType.edit || !isDirty) return;
     var value = editor.getValue();
     var result = postProcess(md.render(value)).children().toArray();
-    //ui.area.markdown.html(result);
-    //finishView(ui.area.markdown);
     partialUpdate(result, lastResult, ui.area.markdown.children().toArray());
     if (result && lastResult && result.length != lastResult.length)
         updateDataAttrs(result, ui.area.markdown.children().toArray());

public/vendor/ot/ajax-adapter.js

@@ -0,0 +1,116 @@
+/*global ot, $ */
+
+ot.AjaxAdapter = (function () {
+  'use strict';
+
+  function AjaxAdapter (path, ownUserName, revision) {
+    if (path[path.length - 1] !== '/') { path += '/'; }
+    this.path = path;
+    this.ownUserName = ownUserName;
+    this.majorRevision = revision.major || 0;
+    this.minorRevision = revision.minor || 0;
+    this.poll();
+  }
+
+  AjaxAdapter.prototype.renderRevisionPath = function () {
+    return 'revision/' + this.majorRevision + '-' + this.minorRevision;
+  };
+
+  AjaxAdapter.prototype.handleResponse = function (data) {
+    var i;
+    var operations = data.operations;
+    for (i = 0; i < operations.length; i++) {
+      if (operations[i].user === this.ownUserName) {
+        this.trigger('ack');
+      } else {
+        this.trigger('operation', operations[i].operation);
+      }
+    }
+    if (operations.length > 0) {
+      this.majorRevision += operations.length;
+      this.minorRevision = 0;
+    }
+
+    var events = data.events;
+    if (events) {
+      for (i = 0; i < events.length; i++) {
+        var user = events[i].user;
+        if (user === this.ownUserName) { continue; }
+        switch (events[i].event) {
+          case 'joined':    this.trigger('set_name', user, user); break;
+          case 'left':      this.trigger('client_left', user); break;
+          case 'selection': this.trigger('selection', user, events[i].selection); break;
+        }
+      }
+      this.minorRevision += events.length;
+    }
+
+    var users = data.users;
+    if (users) {
+      delete users[this.ownUserName];
+      this.trigger('clients', users);
+    }
+
+    if (data.revision) {
+      this.majorRevision = data.revision.major;
+      this.minorRevision = data.revision.minor;
+    }
+  };
+
+  AjaxAdapter.prototype.poll = function () {
+    var self = this;
+    $.ajax({
+      url: this.path + this.renderRevisionPath(),
+      type: 'GET',
+      dataType: 'json',
+      timeout: 5000,
+      success: function (data) {
+        self.handleResponse(data);
+        self.poll();
+      },
+      error: function () {
+        setTimeout(function () { self.poll(); }, 500);
+      }
+    });
+  };
+
+  AjaxAdapter.prototype.sendOperation = function (revision, operation, selection) {
+    if (revision !== this.majorRevision) { throw new Error("Revision numbers out of sync"); }
+    var self = this;
+    $.ajax({
+      url: this.path + this.renderRevisionPath(),
+      type: 'POST',
+      data: JSON.stringify({ operation: operation, selection: selection }),
+      contentType: 'application/json',
+      processData: false,
+      success: function (data) {},
+      error: function () {
+        setTimeout(function () { self.sendOperation(revision, operation, selection); }, 500);
+      }
+    });
+  };
+
+  AjaxAdapter.prototype.sendSelection = function (obj) {
+    $.ajax({
+      url: this.path + this.renderRevisionPath() + '/selection',
+      type: 'POST',
+      data: JSON.stringify(obj),
+      contentType: 'application/json',
+      processData: false,
+      timeout: 1000
+    });
+  };
+
+  AjaxAdapter.prototype.registerCallbacks = function (cb) {
+    this.callbacks = cb;
+  };
+
+  AjaxAdapter.prototype.trigger = function (event) {
+    var args = Array.prototype.slice.call(arguments, 1);
+    var action = this.callbacks && this.callbacks[event];
+    if (action) { action.apply(this, args); }
+  };
+
+  return AjaxAdapter;
+
+})();

public/vendor/ot/client.js

@@ -0,0 +1,312 @@
+// translation of https://github.com/djspiewak/cccp/blob/master/agent/src/main/scala/com/codecommit/cccp/agent/state.scala
+
+if (typeof ot === 'undefined') {
+  var ot = {};
+}
+
+ot.Client = (function (global) {
+  'use strict';
+
+  // Client constructor
+  function Client (revision) {
+    this.revision = revision; // the next expected revision number
+    this.setState(synchronized_); // start state
+  }
+
+  Client.prototype.setState = function (state) {
+    this.state = state;
+  };
+
+  // Call this method when the user changes the document.
+  Client.prototype.applyClient = function (operation) {
+    this.setState(this.state.applyClient(this, operation));
+  };
+
+  // Call this method with a new operation from the server
+  Client.prototype.applyServer = function (revision, operation) {
+    this.setState(this.state.applyServer(this, revision, operation));
+  };
+
+  Client.prototype.applyOperations = function (head, operations) {
+    this.setState(this.state.applyOperations(this, head, operations));
+  };
+
+  Client.prototype.serverAck = function (revision) {
+    this.setState(this.state.serverAck(this, revision));
+  };
+
+  Client.prototype.serverReconnect = function () {
+    if (typeof this.state.resend === 'function') { this.state.resend(this); }
+  };
+
+  // Transforms a selection from the latest known server state to the current
+  // client state. For example, if we get from the server the information that
+  // another user's cursor is at position 3, but the server hasn't yet received
+  // our newest operation, an insertion of 5 characters at the beginning of the
+  // document, the correct position of the other user's cursor in our current
+  // document is 8.
+  Client.prototype.transformSelection = function (selection) {
+    return this.state.transformSelection(selection);
+  };
+
+  // Override this method.
+  Client.prototype.sendOperation = function (revision, operation) {
+    throw new Error("sendOperation must be defined in child class");
+  };
+
+  // Override this method.
+  Client.prototype.applyOperation = function (operation) {
+    throw new Error("applyOperation must be defined in child class");
+  };
+
+
+  // In the 'Synchronized' state, there is no pending operation that the client
+  // has sent to the server.
+  function Synchronized () {}
+  Client.Synchronized = Synchronized;
+
+  Synchronized.prototype.applyClient = function (client, operation) {
+    // When the user makes an edit, send the operation to the server and
+    // switch to the 'AwaitingConfirm' state
+    client.sendOperation(client.revision, operation);
+    return new AwaitingConfirm(operation);
+  };
+
+  Synchronized.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // When we receive a new operation from the server, the operation can be
+    // simply applied to the current document
+    client.applyOperation(operation);
+    return this;
+  };
+
+  Synchronized.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  // Nothing to do because the latest server state and client state are the same.
+  Synchronized.prototype.transformSelection = function (x) { return x; };
+
+  // Singleton
+  var synchronized_ = new Synchronized();
+
+
+  // In the 'AwaitingConfirm' state, there's one operation the client has sent
+  // to the server and is still waiting for an acknowledgement.
+  function AwaitingConfirm (outstanding) {
+    // Save the pending operation
+    this.outstanding = outstanding;
+  }
+  Client.AwaitingConfirm = AwaitingConfirm;
+
+  AwaitingConfirm.prototype.applyClient = function (client, operation) {
+    // When the user makes an edit, don't send the operation immediately,
+    // instead switch to 'AwaitingWithBuffer' state
+    return new AwaitingWithBuffer(this.outstanding, operation);
+  };
+
+  AwaitingConfirm.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // This is another client's operation. Visualization:
+    //
+    //                   /\
+    // this.outstanding /  \ operation
+    //                 /    \
+    //                 \    /
+    //  pair[1]         \  / pair[0] (new outstanding)
+    //  (can be applied  \/
+    //  to the client's
+    //  current document)
+    var pair = operation.constructor.transform(this.outstanding, operation);
+    client.applyOperation(pair[1]);
+    return new AwaitingConfirm(pair[0]);
+  };
+
+  AwaitingConfirm.prototype.serverAck = function (client, revision) {
+    if (revision - client.revision > 1) {
+      return new Stale(this.outstanding, client, revision).getOperations();
+    }
+    client.revision = revision;
+    // The client's operation has been acknowledged
+    // => switch to synchronized state
+    return synchronized_;
+  };
+
+  AwaitingConfirm.prototype.transformSelection = function (selection) {
+    return selection.transform(this.outstanding);
+  };
+
+  AwaitingConfirm.prototype.resend = function (client) {
+    // The confirm didn't come because the client was disconnected.
+    // Now that it has reconnected, we resend the outstanding operation.
+    client.sendOperation(client.revision, this.outstanding);
+  };
+
+
+  // In the 'AwaitingWithBuffer' state, the client is waiting for an operation
+  // to be acknowledged by the server while buffering the edits the user makes
+  function AwaitingWithBuffer (outstanding, buffer) {
+    // Save the pending operation and the user's edits since then
+    this.outstanding = outstanding;
+    this.buffer = buffer;
+  }
+  Client.AwaitingWithBuffer = AwaitingWithBuffer;
+
+  AwaitingWithBuffer.prototype.applyClient = function (client, operation) {
+    // Compose the user's changes onto the buffer
+    var newBuffer = this.buffer.compose(operation);
+    return new AwaitingWithBuffer(this.outstanding, newBuffer);
+  };
+
+  AwaitingWithBuffer.prototype.applyServer = function (client, revision, operation) {
+    if (revision - client.revision > 1) {
+      throw new Error("Invalid revision.");
+    }
+    client.revision = revision;
+    // Operation comes from another client
+    //
+    //                       /\
+    //     this.outstanding /  \ operation
+    //                     /    \
+    //                    /\    /
+    //       this.buffer /  \* / pair1[0] (new outstanding)
+    //                  /    \/
+    //                  \    /
+    //          pair2[1] \  / pair2[0] (new buffer)
+    // the transformed    \/
+    // operation -- can
+    // be applied to the
+    // client's current
+    // document
+    //
+    // * pair1[1]
+    var transform = operation.constructor.transform;
+    var pair1 = transform(this.outstanding, operation);
+    var pair2 = transform(this.buffer, pair1[1]);
+    client.applyOperation(pair2[1]);
+    return new AwaitingWithBuffer(pair1[0], pair2[0]);
+  };
+
+  AwaitingWithBuffer.prototype.serverAck = function (client, revision) {
+    if (revision - client.revision > 1) {
+      return new StaleWithBuffer(this.outstanding, this.buffer, client, revision).getOperations();
+    }
+    client.revision = revision;
+    // The pending operation has been acknowledged
+    // => send buffer
+    client.sendOperation(client.revision, this.buffer);
+    return new AwaitingConfirm(this.buffer);
+  };
+
+  AwaitingWithBuffer.prototype.transformSelection = function (selection) {
+    return selection.transform(this.outstanding).transform(this.buffer);
+  };
+
+  AwaitingWithBuffer.prototype.resend = function (client) {
+    // The confirm didn't come because the client was disconnected.
+    // Now that it has reconnected, we resend the outstanding operation.
+    client.sendOperation(client.revision, this.outstanding);
+  };
+
+
+  function Stale(acknowlaged, client, revision) {
+    this.acknowlaged = acknowlaged;
+    this.client = client;
+    this.revision = revision;
+  }
+  Client.Stale = Stale;
+
+  Stale.prototype.applyClient = function (client, operation) {
+    return new StaleWithBuffer(this.acknowlaged, operation, client, this.revision);
+  };
+
+  Stale.prototype.applyServer = function (client, revision, operation) {
+    throw new Error("Ignored server-side change.");
+  };
+
+  Stale.prototype.applyOperations = function (client, head, operations) {
+    var transform = this.acknowlaged.constructor.transform;
+    for (var i = 0; i < operations.length; i++) {
+      var op = ot.TextOperation.fromJSON(operations[i]);
+      var pair = transform(this.acknowlaged, op);
+      client.applyOperation(pair[1]);
+      this.acknowlaged = pair[0];
+    }
+    client.revision = this.revision;
+    return synchronized_;
+  };
+
+  Stale.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  Stale.prototype.transformSelection = function (selection) {
+    return selection;
+  };
+
+  Stale.prototype.getOperations = function () {
+    this.client.getOperations(this.client.revision, this.revision - 1); // acknowlaged is the one at revision
+    return this;
+  };
+
+
+  function StaleWithBuffer(acknowlaged, buffer, client, revision) {
+    this.acknowlaged = acknowlaged;
+    this.buffer = buffer;
+    this.client = client;
+    this.revision = revision;
+  }
+  Client.StaleWithBuffer = StaleWithBuffer;
+
+  StaleWithBuffer.prototype.applyClient = function (client, operation) {
+    var buffer = this.buffer.compose(operation);
+    return new StaleWithBuffer(this.acknowlaged, buffer, client, this.revision);
+  };
+
+  StaleWithBuffer.prototype.applyServer = function (client, revision, operation) {
+    throw new Error("Ignored server-side change.");
+  };
+
+  StaleWithBuffer.prototype.applyOperations = function (client, head, operations) {
+    var transform = this.acknowlaged.constructor.transform;
+    for (var i = 0; i < operations.length; i++) {
+      var op = ot.TextOperation.fromJSON(operations[i]);
+      var pair1 = transform(this.acknowlaged, op);
+      var pair2 = transform(this.buffer, pair1[1]);
+      client.applyOperation(pair2[1]);
+      this.acknowlaged = pair1[0];
+      this.buffer = pair2[0];
+    }
+    client.revision = this.revision;
+    client.sendOperation(client.revision, this.buffer);
+    return new AwaitingConfirm(this.buffer);
+  };
+
+  StaleWithBuffer.prototype.serverAck = function (client, revision) {
+    throw new Error("There is no pending operation.");
+  };
+
+  StaleWithBuffer.prototype.transformSelection = function (selection) {
+    return selection;
+  };
+
+  StaleWithBuffer.prototype.getOperations = function () {
+    this.client.getOperations(this.client.revision, this.revision - 1); // acknowlaged is the one at revision
+    return this;
+  };
+
+
+  return Client;
+
+}(this));
+
+if (typeof module === 'object') {
+  module.exports = ot.Client;
+}
+

public/vendor/ot/codemirror-adapter.js

@@ -0,0 +1,393 @@
+/*global ot */
+
+ot.CodeMirrorAdapter = (function (global) {
+    'use strict';
+
+    var TextOperation = ot.TextOperation;
+    var Selection = ot.Selection;
+
+    function CodeMirrorAdapter(cm) {
+        this.cm = cm;
+        this.ignoreNextChange = false;
+        this.changeInProgress = false;
+        this.selectionChanged = false;
+
+        bind(this, 'onChanges');
+        bind(this, 'onChange');
+        bind(this, 'onCursorActivity');
+        bind(this, 'onFocus');
+        bind(this, 'onBlur');
+
+        cm.on('changes', this.onChanges);
+        cm.on('change', this.onChange);
+        cm.on('cursorActivity', this.onCursorActivity);
+        cm.on('focus', this.onFocus);
+        cm.on('blur', this.onBlur);
+    }
+
+    // Removes all event listeners from the CodeMirror instance.
+    CodeMirrorAdapter.prototype.detach = function () {
+        this.cm.off('changes', this.onChanges);
+        this.cm.off('change', this.onChange);
+        this.cm.off('cursorActivity', this.onCursorActivity);
+        this.cm.off('focus', this.onFocus);
+        this.cm.off('blur', this.onBlur);
+    };
+
+    function cmpPos(a, b) {
+        if (a.line < b.line) {
+            return -1;
+        }
+        if (a.line > b.line) {
+            return 1;
+        }
+        if (a.ch < b.ch) {
+            return -1;
+        }
+        if (a.ch > b.ch) {
+            return 1;
+        }
+        return 0;
+    }
+
+    function posEq(a, b) {
+        return cmpPos(a, b) === 0;
+    }
+
+    function posLe(a, b) {
+        return cmpPos(a, b) <= 0;
+    }
+
+    function minPos(a, b) {
+        return posLe(a, b) ? a : b;
+    }
+
+    function maxPos(a, b) {
+        return posLe(a, b) ? b : a;
+    }
+
+    function codemirrorDocLength(doc) {
+        return doc.indexFromPos({
+                line: doc.lastLine(),
+                ch: 0
+            }) +
+            doc.getLine(doc.lastLine()).length;
+    }
+
+    // Converts a CodeMirror change array (as obtained from the 'changes' event
+    // in CodeMirror v4) or single change or linked list of changes (as returned
+    // by the 'change' event in CodeMirror prior to version 4) into a
+    // TextOperation and its inverse and returns them as a two-element array.
+    CodeMirrorAdapter.operationFromCodeMirrorChanges = function (changes, doc) {
+        // Approach: Replay the changes, beginning with the most recent one, and
+        // construct the operation and its inverse. We have to convert the position
+        // in the pre-change coordinate system to an index. We have a method to
+        // convert a position in the coordinate system after all changes to an index,
+        // namely CodeMirror's `indexFromPos` method. We can use the information of
+        // a single change object to convert a post-change coordinate system to a
+        // pre-change coordinate system. We can now proceed inductively to get a
+        // pre-change coordinate system for all changes in the linked list.
+        // A disadvantage of this approach is its complexity `O(n^2)` in the length
+        // of the linked list of changes.
+
+        var docEndLength = codemirrorDocLength(doc);
+        var operation = new TextOperation().retain(docEndLength);
+        var inverse = new TextOperation().retain(docEndLength);
+
+        var indexFromPos = function (pos) {
+            return doc.indexFromPos(pos);
+        };
+
+        function last(arr) {
+            return arr[arr.length - 1];
+        }
+
+        function sumLengths(strArr) {
+            if (strArr.length === 0) {
+                return 0;
+            }
+            var sum = 0;
+            for (var i = 0; i < strArr.length; i++) {
+                sum += strArr[i].length;
+            }
+            return sum + strArr.length - 1;
+        }
+
+        function updateIndexFromPos(indexFromPos, change) {
+            return function (pos) {
+                if (posLe(pos, change.from)) {
+                    return indexFromPos(pos);
+                }
+                if (posLe(change.to, pos)) {
+                    return indexFromPos({
+                        line: pos.line + change.text.length - 1 - (change.to.line - change.from.line),
+                        ch: (change.to.line < pos.line) ?
+                            pos.ch : (change.text.length <= 1) ?
+                            pos.ch - (change.to.ch - change.from.ch) + sumLengths(change.text) : pos.ch - change.to.ch + last(change.text).length
+                    }) + sumLengths(change.removed) - sumLengths(change.text);
+                }
+                if (change.from.line === pos.line) {
+                    return indexFromPos(change.from) + pos.ch - change.from.ch;
+                }
+                return indexFromPos(change.from) +
+                    sumLengths(change.removed.slice(0, pos.line - change.from.line)) +
+                    1 + pos.ch;
+            };
+        }
+
+        for (var i = changes.length - 1; i >= 0; i--) {
+            var change = changes[i];
+            indexFromPos = updateIndexFromPos(indexFromPos, change);
+
+            var fromIndex = indexFromPos(change.from);
+            var restLength = docEndLength - fromIndex - sumLengths(change.text);
+
+            operation = new TextOperation()
+                .retain(fromIndex)['delete'](sumLengths(change.removed))
+                .insert(change.text.join('\n'))
+                .retain(restLength)
+                .compose(operation);
+
+            inverse = inverse.compose(new TextOperation()
+                .retain(fromIndex)['delete'](sumLengths(change.text))
+                .insert(change.removed.join('\n'))
+                .retain(restLength)
+            );
+
+            docEndLength += sumLengths(change.removed) - sumLengths(change.text);
+        }
+
+        return [operation, inverse];
+    };
+
+    // Singular form for backwards compatibility.
+    CodeMirrorAdapter.operationFromCodeMirrorChange =
+        CodeMirrorAdapter.operationFromCodeMirrorChanges;
+
+    // Apply an operation to a CodeMirror instance.
+    CodeMirrorAdapter.applyOperationToCodeMirror = function (operation, cm) {
+        cm.operation(function () {
+            var ops = operation.ops;
+            var index = 0; // holds the current index into CodeMirror's content
+            for (var i = 0, l = ops.length; i < l; i++) {
+                var op = ops[i];
+                if (TextOperation.isRetain(op)) {
+                    index += op;
+                } else if (TextOperation.isInsert(op)) {
+                    cm.replaceRange(op, cm.posFromIndex(index), null, 'ignoreHistory');
+                    index += op.length;
+                } else if (TextOperation.isDelete(op)) {
+                    var from = cm.posFromIndex(index);
+                    var to = cm.posFromIndex(index - op);
+                    cm.replaceRange('', from, to, 'ignoreHistory');
+                }
+            }
+        });
+    };
+
+    CodeMirrorAdapter.prototype.registerCallbacks = function (cb) {
+        this.callbacks = cb;
+    };
+
+    CodeMirrorAdapter.prototype.onChange = function () {
+        // By default, CodeMirror's event order is the following:
+        // 1. 'change', 2. 'cursorActivity', 3. 'changes'.
+        // We want to fire the 'selectionChange' event after the 'change' event,
+        // but need the information from the 'changes' event. Therefore, we detect
+        // when a change is in progress by listening to the change event, setting
+        // a flag that makes this adapter defer all 'cursorActivity' events.
+        this.changeInProgress = true;
+    };
+
+    CodeMirrorAdapter.prototype.onChanges = function (_, changes) {
+        if (!this.ignoreNextChange) {
+            var pair = CodeMirrorAdapter.operationFromCodeMirrorChanges(changes, this.cm);
+            this.trigger('change', pair[0], pair[1]);
+        }
+        if (this.selectionChanged) {
+            this.trigger('selectionChange');
+        }
+        this.changeInProgress = false;
+        this.ignoreNextChange = false;
+    };
+
+    CodeMirrorAdapter.prototype.onCursorActivity =
+        CodeMirrorAdapter.prototype.onFocus = function () {
+            if (this.changeInProgress) {
+                this.selectionChanged = true;
+            } else {
+                this.trigger('selectionChange');
+            }
+        };
+
+    CodeMirrorAdapter.prototype.onBlur = function () {
+        if (!this.cm.somethingSelected()) {
+            this.trigger('blur');
+        }
+    };
+
+    CodeMirrorAdapter.prototype.getValue = function () {
+        return this.cm.getValue();
+    };
+
+    CodeMirrorAdapter.prototype.getSelection = function () {
+        var cm = this.cm;
+
+        var selectionList = cm.listSelections();
+        var ranges = [];
+        for (var i = 0; i < selectionList.length; i++) {
+            ranges[i] = new Selection.Range(
+                cm.indexFromPos(selectionList[i].anchor),
+                cm.indexFromPos(selectionList[i].head)
+            );
+        }
+
+        return new Selection(ranges);
+    };
+
+    CodeMirrorAdapter.prototype.setSelection = function (selection) {
+        var ranges = [];
+        for (var i = 0; i < selection.ranges.length; i++) {
+            var range = selection.ranges[i];
+            ranges[i] = {
+                anchor: this.cm.posFromIndex(range.anchor),
+                head: this.cm.posFromIndex(range.head)
+            };
+        }
+        this.cm.setSelections(ranges);
+    };
+
+    var addStyleRule = (function () {
+        var added = {};
+        var styleElement = document.createElement('style');
+        document.documentElement.getElementsByTagName('head')[0].appendChild(styleElement);
+        var styleSheet = styleElement.sheet;
+
+        return function (css) {
+            if (added[css]) {
+                return;
+            }
+            added[css] = true;
+            styleSheet.insertRule(css, (styleSheet.cssRules || styleSheet.rules).length);
+        };
+    }());
+
+    CodeMirrorAdapter.prototype.setOtherCursor = function (position, color, clientId) {
+        var cursorPos = this.cm.posFromIndex(position);
+        var cursorCoords = this.cm.cursorCoords(cursorPos);
+        var cursorEl = document.createElement('span');
+        cursorEl.className = 'other-client';
+        cursorEl.style.display = 'none';
+        /*
+        cursorEl.style.padding = '0';
+        cursorEl.style.marginLeft = cursorEl.style.marginRight = '-1px';
+        cursorEl.style.borderLeftWidth = '2px';
+        cursorEl.style.borderLeftStyle = 'solid';
+        cursorEl.style.borderLeftColor = color;
+        cursorEl.style.height = (cursorCoords.bottom - cursorCoords.top) * 0.9 + 'px';
+        cursorEl.style.zIndex = 0;
+        */
+        cursorEl.setAttribute('data-clientid', clientId);
+        return this.cm.setBookmark(cursorPos, {
+            widget: cursorEl,
+            insertLeft: true
+        });
+    };
+
+    CodeMirrorAdapter.prototype.setOtherSelectionRange = function (range, color, clientId) {
+        var match = /^#([0-9a-fA-F]{6})$/.exec(color);
+        if (!match) {
+            throw new Error("only six-digit hex colors are allowed.");
+        }
+        var selectionClassName = 'selection-' + match[1];
+        var rgbcolor = hex2rgb(color);
+        var rule = '.' + selectionClassName + ' { background: rgba(' + rgbcolor.red + ',' + rgbcolor.green + ',' + rgbcolor.blue + ',0.2); }';
+        addStyleRule(rule);
+
+        var anchorPos = this.cm.posFromIndex(range.anchor);
+        var headPos = this.cm.posFromIndex(range.head);
+
+        return this.cm.markText(
+            minPos(anchorPos, headPos),
+            maxPos(anchorPos, headPos), {
+                className: selectionClassName
+            }
+        );
+    };
+
+    CodeMirrorAdapter.prototype.setOtherSelection = function (selection, color, clientId) {
+        var selectionObjects = [];
+        for (var i = 0; i < selection.ranges.length; i++) {
+            var range = selection.ranges[i];
+            if (range.isEmpty()) {
+                selectionObjects[i] = this.setOtherCursor(range.head, color, clientId);
+            } else {
+                selectionObjects[i] = this.setOtherSelectionRange(range, color, clientId);
+            }
+        }
+        return {
+            clear: function () {
+                for (var i = 0; i < selectionObjects.length; i++) {
+                    selectionObjects[i].clear();
+                }
+            }
+        };
+    };
+
+    CodeMirrorAdapter.prototype.trigger = function (event) {
+        var args = Array.prototype.slice.call(arguments, 1);
+        var action = this.callbacks && this.callbacks[event];
+        if (action) {
+            action.apply(this, args);
+        }
+    };
+
+    CodeMirrorAdapter.prototype.applyOperation = function (operation) {
+        this.ignoreNextChange = true;
+        CodeMirrorAdapter.applyOperationToCodeMirror(operation, this.cm);
+    };
+
+    CodeMirrorAdapter.prototype.registerUndo = function (undoFn) {
+        this.cm.undo = undoFn;
+    };
+
+    CodeMirrorAdapter.prototype.registerRedo = function (redoFn) {
+        this.cm.redo = redoFn;
+    };
+
+    // Throws an error if the first argument is falsy. Useful for debugging.
+    function assert(b, msg) {
+        if (!b) {
+            throw new Error(msg || "assertion error");
+        }
+    }
+
+    // Bind a method to an object, so it doesn't matter whether you call
+    // object.method() directly or pass object.method as a reference to another
+    // function.
+    function bind(obj, method) {
+        var fn = obj[method];
+        obj[method] = function () {
+            fn.apply(obj, arguments);
+        };
+    }
+
+    return CodeMirrorAdapter;
+
+}(this));
+
+function hex2rgb(hex) {
+    if (hex[0] == "#") hex = hex.substr(1);
+    if (hex.length == 3) {
+        var temp = hex;
+        hex = '';
+        temp = /^([a-f0-9])([a-f0-9])([a-f0-9])$/i.exec(temp).slice(1);
+        for (var i = 0; i < 3; i++) hex += temp[i] + temp[i];
+    }
+    var triplets = /^([a-f0-9]{2})([a-f0-9]{2})([a-f0-9]{2})$/i.exec(hex).slice(1);
+    return {
+        red: parseInt(triplets[0], 16),
+        green: parseInt(triplets[1], 16),
+        blue: parseInt(triplets[2], 16)
+    }
+}

public/vendor/ot/compress.sh

@@ -0,0 +1,10 @@
+uglifyjs --compress --mangle --output ot.min.js \
+./text-operation.js \
+./selection.js \
+./wrapped-operation.js \
+./undo-manager.js \
+./client.js \
+./codemirror-adapter.js \
+./socketio-adapter.js \
+./ajax-adapter.js \
+./editor-client.js

public/vendor/ot/editor-client.js

@@ -0,0 +1,354 @@
+/*global ot */
+
+ot.EditorClient = (function () {
+  'use strict';
+
+  var Client = ot.Client;
+  var Selection = ot.Selection;
+  var UndoManager = ot.UndoManager;
+  var TextOperation = ot.TextOperation;
+  var WrappedOperation = ot.WrappedOperation;
+
+
+  function SelfMeta (selectionBefore, selectionAfter) {
+    this.selectionBefore = selectionBefore;
+    this.selectionAfter  = selectionAfter;
+  }
+
+  SelfMeta.prototype.invert = function () {
+    return new SelfMeta(this.selectionAfter, this.selectionBefore);
+  };
+
+  SelfMeta.prototype.compose = function (other) {
+    return new SelfMeta(this.selectionBefore, other.selectionAfter);
+  };
+
+  SelfMeta.prototype.transform = function (operation) {
+    return new SelfMeta(
+      this.selectionBefore.transform(operation),
+      this.selectionAfter.transform(operation)
+    );
+  };
+
+
+  function OtherMeta (clientId, selection) {
+    this.clientId  = clientId;
+    this.selection = selection;
+  }
+
+  OtherMeta.fromJSON = function (obj) {
+    return new OtherMeta(
+      obj.clientId,
+      obj.selection && Selection.fromJSON(obj.selection)
+    );
+  };
+
+  OtherMeta.prototype.transform = function (operation) {
+    return new OtherMeta(
+      this.clientId,
+      this.selection && this.selection.transform(operation)
+    );
+  };
+
+
+  function OtherClient (id, listEl, editorAdapter, name, color, selection) {
+    this.id = id;
+    this.listEl = listEl;
+    this.editorAdapter = editorAdapter;
+    this.name = name;
+    this.color = color;
+
+    this.li = document.createElement('li');
+    if (name) {
+      this.li.textContent = name;
+      this.listEl.appendChild(this.li);
+    }
+    
+    if(!color)
+      this.setColor(name ? hueFromName(name) : Math.random());
+    else
+      this.setForceColor(color);
+    if (selection) { this.updateSelection(selection); }
+  }
+
+  OtherClient.prototype.setColor = function (hue) {
+    this.hue = hue;
+    this.color = hsl2hex(hue, 0.75, 0.5);
+    this.lightColor = hsl2hex(hue, 0.5, 0.9);
+    if (this.li) { this.li.style.color = this.color; }
+  };
+    
+  OtherClient.prototype.setForceColor = function (color) {
+    this.hue = null;
+    this.color = color;
+    this.lightColor = color;
+    if (this.li) { this.li.style.color = this.color; }
+  };
+
+  OtherClient.prototype.setName = function (name) {
+    if (this.name === name) { return; }
+    this.name = name;
+
+    this.li.textContent = name;
+    if (!this.li.parentNode) {
+      this.listEl.appendChild(this.li);
+    }
+
+    this.setColor(hueFromName(name));
+  };
+
+  OtherClient.prototype.updateSelection = function (selection) {
+    this.removeSelection();
+    this.selection = selection;
+    this.mark = this.editorAdapter.setOtherSelection(
+      selection,
+      selection.position === selection.selectionEnd ? this.color : this.lightColor,
+      this.id
+    );
+  };
+
+  OtherClient.prototype.remove = function () {
+    if (this.li) { removeElement(this.li); }
+    this.removeSelection();
+  };
+
+  OtherClient.prototype.removeSelection = function () {
+    if (this.mark) {
+      this.mark.clear();
+      this.mark = null;
+    }
+  };
+
+
+  function EditorClient (revision, clients, serverAdapter, editorAdapter) {
+    Client.call(this, revision);
+    this.serverAdapter = serverAdapter;
+    this.editorAdapter = editorAdapter;
+    this.undoManager = new UndoManager();
+
+    this.initializeClientList();
+    this.initializeClients(clients);
+
+    var self = this;
+
+    this.editorAdapter.registerCallbacks({
+      change: function (operation, inverse) { self.onChange(operation, inverse); },
+      selectionChange: function () { self.onSelectionChange(); },
+      blur: function () { self.onBlur(); }
+    });
+    this.editorAdapter.registerUndo(function () { self.undo(); });
+    this.editorAdapter.registerRedo(function () { self.redo(); });
+
+    this.serverAdapter.registerCallbacks({
+      client_left: function (clientId) { self.onClientLeft(clientId); },
+      set_name: function (clientId, name) { self.getClientObject(clientId).setName(name); },
+      set_color: function (clientId, color) { self.getClientObject(clientId).setForceColor(color); },
+      ack: function (revision) { self.serverAck(revision); },
+      operation: function (revision, operation) {
+        self.applyServer(revision, TextOperation.fromJSON(operation));
+      },
+      operations: function (head, operations) {
+        self.applyOperations(head, operations);
+      },
+      selection: function (clientId, selection) {
+        if (selection) {
+          self.getClientObject(clientId).updateSelection(
+            self.transformSelection(Selection.fromJSON(selection))
+          );
+        } else {
+          self.getClientObject(clientId).removeSelection();
+        }
+      },
+      clients: function (clients) {
+        var clientId;
+        for (clientId in self.clients) {
+          if (self.clients.hasOwnProperty(clientId) && !clients.hasOwnProperty(clientId)) {
+            self.onClientLeft(clientId);
+          }
+        }
+
+        for (clientId in clients) {
+          if (clients.hasOwnProperty(clientId)) {
+            var clientObject = self.getClientObject(clientId);
+
+            if (clients[clientId].name) {
+              clientObject.setName(clients[clientId].name);
+            }
+
+            var selection = clients[clientId].selection;
+            if (selection) {
+              self.clients[clientId].updateSelection(
+                self.transformSelection(Selection.fromJSON(selection))
+              );
+            } else {
+              self.clients[clientId].removeSelection();
+            }
+          }
+        }
+      },
+      reconnect: function () { self.serverReconnect(); }
+    });
+  }
+
+  inherit(EditorClient, Client);
+
+  EditorClient.prototype.addClient = function (clientId, clientObj) {
+    this.clients[clientId] = new OtherClient(
+      clientId,
+      this.clientListEl,
+      this.editorAdapter,
+      clientObj.name || clientId,
+      clientObj.color || null,
+      clientObj.selection ? Selection.fromJSON(clientObj.selection) : null
+    );
+  };
+
+  EditorClient.prototype.initializeClients = function (clients) {
+    this.clients = {};
+    for (var clientId in clients) {
+      if (clients.hasOwnProperty(clientId)) {
+        this.addClient(clientId, clients[clientId]);
+      }
+    }
+  };
+
+  EditorClient.prototype.getClientObject = function (clientId) {
+    var client = this.clients[clientId];
+    if (client) { return client; }
+    return this.clients[clientId] = new OtherClient(
+      clientId,
+      this.clientListEl,
+      this.editorAdapter
+    );
+  };
+
+  EditorClient.prototype.onClientLeft = function (clientId) {
+    //console.log("User disconnected: " + clientId);
+    var client = this.clients[clientId];
+    if (!client) { return; }
+    client.remove();
+    delete this.clients[clientId];
+  };
+
+  EditorClient.prototype.initializeClientList = function () {
+    this.clientListEl = document.createElement('ul');
+  };
+
+  EditorClient.prototype.applyUnredo = function (operation) {
+    this.undoManager.add(operation.invert(this.editorAdapter.getValue()));
+    this.editorAdapter.applyOperation(operation.wrapped);
+    this.selection = operation.meta.selectionAfter;
+    this.editorAdapter.setSelection(this.selection);
+    this.applyClient(operation.wrapped);
+  };
+
+  EditorClient.prototype.undo = function () {
+    var self = this;
+    if (!this.undoManager.canUndo()) { return; }
+    this.undoManager.performUndo(function (o) { self.applyUnredo(o); });
+  };
+
+  EditorClient.prototype.redo = function () {
+    var self = this;
+    if (!this.undoManager.canRedo()) { return; }
+    this.undoManager.performRedo(function (o) { self.applyUnredo(o); });
+  };
+
+  EditorClient.prototype.onChange = function (textOperation, inverse) {
+    var selectionBefore = this.selection;
+    this.updateSelection();
+    var meta = new SelfMeta(selectionBefore, this.selection);
+    var operation = new WrappedOperation(textOperation, meta);
+
+    var compose = this.undoManager.undoStack.length > 0 &&
+      inverse.shouldBeComposedWithInverted(last(this.undoManager.undoStack).wrapped);
+    var inverseMeta = new SelfMeta(this.selection, selectionBefore);
+    this.undoManager.add(new WrappedOperation(inverse, inverseMeta), compose);
+    this.applyClient(textOperation);
+  };
+
+  EditorClient.prototype.updateSelection = function () {
+    this.selection = this.editorAdapter.getSelection();
+  };
+
+  EditorClient.prototype.onSelectionChange = function () {
+    var oldSelection = this.selection;
+    this.updateSelection();
+    if (oldSelection && this.selection.equals(oldSelection)) { return; }
+    this.sendSelection(this.selection);
+  };
+
+  EditorClient.prototype.onBlur = function () {
+    this.selection = null;
+    this.sendSelection(null);
+  };
+
+  EditorClient.prototype.sendSelection = function (selection) {
+    if (this.state instanceof Client.AwaitingWithBuffer) { return; }
+    this.serverAdapter.sendSelection(selection);
+  };
+
+  EditorClient.prototype.sendOperation = function (revision, operation) {
+    this.serverAdapter.sendOperation(revision, operation.toJSON(), this.selection);
+  };
+
+  EditorClient.prototype.getOperations = function (base, head) {
+    this.serverAdapter.getOperations(base, head);
+  };
+
+  EditorClient.prototype.applyOperation = function (operation) {
+    this.editorAdapter.applyOperation(operation);
+    this.updateSelection();
+    this.undoManager.transform(new WrappedOperation(operation, null));
+  };
+
+  function rgb2hex (r, g, b) {
+    function digits (n) {
+      var m = Math.round(255*n).toString(16);
+      return m.length === 1 ? '0'+m : m;
+    }
+    return '#' + digits(r) + digits(g) + digits(b);
+  }
+
+  function hsl2hex (h, s, l) {
+    if (s === 0) { return rgb2hex(l, l, l); }
+    var var2 = l < 0.5 ? l * (1+s) : (l+s) - (s*l);
+    var var1 = 2 * l - var2;
+    var hue2rgb = function (hue) {
+      if (hue < 0) { hue += 1; }
+      if (hue > 1) { hue -= 1; }
+      if (6*hue < 1) { return var1 + (var2-var1)*6*hue; }
+      if (2*hue < 1) { return var2; }
+      if (3*hue < 2) { return var1 + (var2-var1)*6*(2/3 - hue); }
+      return var1;
+    };
+    return rgb2hex(hue2rgb(h+1/3), hue2rgb(h), hue2rgb(h-1/3));
+  }
+
+  function hueFromName (name) {
+    var a = 1;
+    for (var i = 0; i < name.length; i++) {
+      a = 17 * (a+name.charCodeAt(i)) % 360;
+    }
+    return a/360;
+  }
+
+  // Set Const.prototype.__proto__ to Super.prototype
+  function inherit (Const, Super) {
+    function F () {}
+    F.prototype = Super.prototype;
+    Const.prototype = new F();
+    Const.prototype.constructor = Const;
+  }
+
+  function last (arr) { return arr[arr.length - 1]; }
+
+  // Remove an element from the DOM.
+  function removeElement (el) {
+    if (el.parentNode) {
+      el.parentNode.removeChild(el);
+    }
+  }
+
+  return EditorClient;
+}());

public/vendor/ot/selection.js

@@ -0,0 +1,117 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.Selection = (function (global) {
+  'use strict';
+
+  var TextOperation = global.ot ? global.ot.TextOperation : require('./text-operation');
+
+  // Range has `anchor` and `head` properties, which are zero-based indices into
+  // the document. The `anchor` is the side of the selection that stays fixed,
+  // `head` is the side of the selection where the cursor is. When both are
+  // equal, the range represents a cursor.
+  function Range (anchor, head) {
+    this.anchor = anchor;
+    this.head = head;
+  }
+
+  Range.fromJSON = function (obj) {
+    return new Range(obj.anchor, obj.head);
+  };
+
+  Range.prototype.equals = function (other) {
+    return this.anchor === other.anchor && this.head === other.head;
+  };
+
+  Range.prototype.isEmpty = function () {
+    return this.anchor === this.head;
+  };
+
+  Range.prototype.transform = function (other) {
+    function transformIndex (index) {
+      var newIndex = index;
+      var ops = other.ops;
+      for (var i = 0, l = other.ops.length; i < l; i++) {
+        if (TextOperation.isRetain(ops[i])) {
+          index -= ops[i];
+        } else if (TextOperation.isInsert(ops[i])) {
+          newIndex += ops[i].length;
+        } else {
+          newIndex -= Math.min(index, -ops[i]);
+          index += ops[i];
+        }
+        if (index < 0) { break; }
+      }
+      return newIndex;
+    }
+
+    var newAnchor = transformIndex(this.anchor);
+    if (this.anchor === this.head) {
+      return new Range(newAnchor, newAnchor);
+    }
+    return new Range(newAnchor, transformIndex(this.head));
+  };
+
+  // A selection is basically an array of ranges. Every range represents a real
+  // selection or a cursor in the document (when the start position equals the
+  // end position of the range). The array must not be empty.
+  function Selection (ranges) {
+    this.ranges = ranges || [];
+  }
+
+  Selection.Range = Range;
+
+  // Convenience method for creating selections only containing a single cursor
+  // and no real selection range.
+  Selection.createCursor = function (position) {
+    return new Selection([new Range(position, position)]);
+  };
+
+  Selection.fromJSON = function (obj) {
+    var objRanges = obj.ranges || obj;
+    for (var i = 0, ranges = []; i < objRanges.length; i++) {
+      ranges[i] = Range.fromJSON(objRanges[i]);
+    }
+    return new Selection(ranges);
+  };
+
+  Selection.prototype.equals = function (other) {
+    if (this.position !== other.position) { return false; }
+    if (this.ranges.length !== other.ranges.length) { return false; }
+    // FIXME: Sort ranges before comparing them?
+    for (var i = 0; i < this.ranges.length; i++) {
+      if (!this.ranges[i].equals(other.ranges[i])) { return false; }
+    }
+    return true;
+  };
+
+  Selection.prototype.somethingSelected = function () {
+    for (var i = 0; i < this.ranges.length; i++) {
+      if (!this.ranges[i].isEmpty()) { return true; }
+    }
+    return false;
+  };
+
+  // Return the more current selection information.
+  Selection.prototype.compose = function (other) {
+    return other;
+  };
+
+  // Update the selection with respect to an operation.
+  Selection.prototype.transform = function (other) {
+    for (var i = 0, newRanges = []; i < this.ranges.length; i++) {
+      newRanges[i] = this.ranges[i].transform(other);
+    }
+    return new Selection(newRanges);
+  };
+
+  return Selection;
+
+}(this));
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.Selection;
+}

public/vendor/ot/socketio-adapter.js

@@ -0,0 +1,66 @@
+/*global ot */
+
+ot.SocketIOAdapter = (function () {
+    'use strict';
+
+    function SocketIOAdapter(socket) {
+        this.socket = socket;
+
+        var self = this;
+        socket.on('client_left', function (clientId) {
+            self.trigger('client_left', clientId);
+        });
+        socket.on('set_name', function (clientId, name) {
+            self.trigger('set_name', clientId, name);
+        });
+        socket.on('set_color', function (clientId, color) {
+            self.trigger('set_color', clientId, color);
+        });
+        socket.on('ack', function (revision) {
+            self.trigger('ack', revision);
+        });
+        socket.on('operation', function (clientId, revision, operation, selection) {
+            self.trigger('operation', revision, operation);
+            self.trigger('selection', clientId, selection);
+        });
+        socket.on('operations', function (head, operations) {
+            operations = LZString.decompressFromUTF16(operations);
+            operations = JSON.parse(operations);
+            self.trigger('operations', head, operations);
+        });
+        socket.on('selection', function (clientId, selection) {
+            self.trigger('selection', clientId, selection);
+        });
+        socket.on('reconnect', function () {
+            self.trigger('reconnect');
+        });
+    }
+
+    SocketIOAdapter.prototype.sendOperation = function (revision, operation, selection) {
+        operation = LZString.compressToUTF16(JSON.stringify(operation));
+        this.socket.emit('operation', revision, operation, selection);
+    };
+
+    SocketIOAdapter.prototype.sendSelection = function (selection) {
+        this.socket.emit('selection', selection);
+    };
+
+    SocketIOAdapter.prototype.getOperations = function (base, head) {
+        this.socket.emit('get_operations', base, head);
+    };
+
+    SocketIOAdapter.prototype.registerCallbacks = function (cb) {
+        this.callbacks = cb;
+    };
+
+    SocketIOAdapter.prototype.trigger = function (event) {
+        var args = Array.prototype.slice.call(arguments, 1);
+        var action = this.callbacks && this.callbacks[event];
+        if (action) {
+            action.apply(this, args);
+        }
+    };
+
+    return SocketIOAdapter;
+
+}());

public/vendor/ot/text-operation.js

@@ -0,0 +1,530 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.TextOperation = (function () {
+  'use strict';
+
+  // Constructor for new operations.
+  function TextOperation () {
+    if (!this || this.constructor !== TextOperation) {
+      // => function was called without 'new'
+      return new TextOperation();
+    }
+
+    // When an operation is applied to an input string, you can think of this as
+    // if an imaginary cursor runs over the entire string and skips over some
+    // parts, deletes some parts and inserts characters at some positions. These
+    // actions (skip/delete/insert) are stored as an array in the "ops" property.
+    this.ops = [];
+    // An operation's baseLength is the length of every string the operation
+    // can be applied to.
+    this.baseLength = 0;
+    // The targetLength is the length of every string that results from applying
+    // the operation on a valid input string.
+    this.targetLength = 0;
+  }
+
+  TextOperation.prototype.equals = function (other) {
+    if (this.baseLength !== other.baseLength) { return false; }
+    if (this.targetLength !== other.targetLength) { return false; }
+    if (this.ops.length !== other.ops.length) { return false; }
+    for (var i = 0; i < this.ops.length; i++) {
+      if (this.ops[i] !== other.ops[i]) { return false; }
+    }
+    return true;
+  };
+
+  // Operation are essentially lists of ops. There are three types of ops:
+  //
+  // * Retain ops: Advance the cursor position by a given number of characters.
+  //   Represented by positive ints.
+  // * Insert ops: Insert a given string at the current cursor position.
+  //   Represented by strings.
+  // * Delete ops: Delete the next n characters. Represented by negative ints.
+
+  var isRetain = TextOperation.isRetain = function (op) {
+    return typeof op === 'number' && op > 0;
+  };
+
+  var isInsert = TextOperation.isInsert = function (op) {
+    return typeof op === 'string';
+  };
+
+  var isDelete = TextOperation.isDelete = function (op) {
+    return typeof op === 'number' && op < 0;
+  };
+
+
+  // After an operation is constructed, the user of the library can specify the
+  // actions of an operation (skip/insert/delete) with these three builder
+  // methods. They all return the operation for convenient chaining.
+
+  // Skip over a given number of characters.
+  TextOperation.prototype.retain = function (n) {
+    if (typeof n !== 'number') {
+      throw new Error("retain expects an integer");
+    }
+    if (n === 0) { return this; }
+    this.baseLength += n;
+    this.targetLength += n;
+    if (isRetain(this.ops[this.ops.length-1])) {
+      // The last op is a retain op => we can merge them into one op.
+      this.ops[this.ops.length-1] += n;
+    } else {
+      // Create a new op.
+      this.ops.push(n);
+    }
+    return this;
+  };
+
+  // Insert a string at the current position.
+  TextOperation.prototype.insert = function (str) {
+    if (typeof str !== 'string') {
+      throw new Error("insert expects a string");
+    }
+    if (str === '') { return this; }
+    this.targetLength += str.length;
+    var ops = this.ops;
+    if (isInsert(ops[ops.length-1])) {
+      // Merge insert op.
+      ops[ops.length-1] += str;
+    } else if (isDelete(ops[ops.length-1])) {
+      // It doesn't matter when an operation is applied whether the operation
+      // is delete(3), insert("something") or insert("something"), delete(3).
+      // Here we enforce that in this case, the insert op always comes first.
+      // This makes all operations that have the same effect when applied to
+      // a document of the right length equal in respect to the `equals` method.
+      if (isInsert(ops[ops.length-2])) {
+        ops[ops.length-2] += str;
+      } else {
+        ops[ops.length] = ops[ops.length-1];
+        ops[ops.length-2] = str;
+      }
+    } else {
+      ops.push(str);
+    }
+    return this;
+  };
+
+  // Delete a string at the current position.
+  TextOperation.prototype['delete'] = function (n) {
+    if (typeof n === 'string') { n = n.length; }
+    if (typeof n !== 'number') {
+      throw new Error("delete expects an integer or a string");
+    }
+    if (n === 0) { return this; }
+    if (n > 0) { n = -n; }
+    this.baseLength -= n;
+    if (isDelete(this.ops[this.ops.length-1])) {
+      this.ops[this.ops.length-1] += n;
+    } else {
+      this.ops.push(n);
+    }
+    return this;
+  };
+
+  // Tests whether this operation has no effect.
+  TextOperation.prototype.isNoop = function () {
+    return this.ops.length === 0 || (this.ops.length === 1 && isRetain(this.ops[0]));
+  };
+
+  // Pretty printing.
+  TextOperation.prototype.toString = function () {
+    // map: build a new array by applying a function to every element in an old
+    // array.
+    var map = Array.prototype.map || function (fn) {
+      var arr = this;
+      var newArr = [];
+      for (var i = 0, l = arr.length; i < l; i++) {
+        newArr[i] = fn(arr[i]);
+      }
+      return newArr;
+    };
+    return map.call(this.ops, function (op) {
+      if (isRetain(op)) {
+        return "retain " + op;
+      } else if (isInsert(op)) {
+        return "insert '" + op + "'";
+      } else {
+        return "delete " + (-op);
+      }
+    }).join(', ');
+  };
+
+  // Converts operation into a JSON value.
+  TextOperation.prototype.toJSON = function () {
+    return this.ops;
+  };
+
+  // Converts a plain JS object into an operation and validates it.
+  TextOperation.fromJSON = function (ops) {
+    var o = new TextOperation();
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        o.retain(op);
+      } else if (isInsert(op)) {
+        o.insert(op);
+      } else if (isDelete(op)) {
+        o['delete'](op);
+      } else {
+        throw new Error("unknown operation: " + JSON.stringify(op));
+      }
+    }
+    return o;
+  };
+
+  // Apply an operation to a string, returning a new string. Throws an error if
+  // there's a mismatch between the input string and the operation.
+  TextOperation.prototype.apply = function (str) {
+    var operation = this;
+    if (str.length !== operation.baseLength) {
+      throw new Error("The operation's base length must be equal to the string's length.");
+    }
+    var newStr = [], j = 0;
+    var strIndex = 0;
+    var ops = this.ops;
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        if (strIndex + op > str.length) {
+          throw new Error("Operation can't retain more characters than are left in the string.");
+        }
+        // Copy skipped part of the old string.
+        newStr[j++] = str.slice(strIndex, strIndex + op);
+        strIndex += op;
+      } else if (isInsert(op)) {
+        // Insert string.
+        newStr[j++] = op;
+      } else { // delete op
+        strIndex -= op;
+      }
+    }
+    if (strIndex !== str.length) {
+      throw new Error("The operation didn't operate on the whole string.");
+    }
+    return newStr.join('');
+  };
+
+  // Computes the inverse of an operation. The inverse of an operation is the
+  // operation that reverts the effects of the operation, e.g. when you have an
+  // operation 'insert("hello "); skip(6);' then the inverse is 'delete("hello ");
+  // skip(6);'. The inverse should be used for implementing undo.
+  TextOperation.prototype.invert = function (str) {
+    var strIndex = 0;
+    var inverse = new TextOperation();
+    var ops = this.ops;
+    for (var i = 0, l = ops.length; i < l; i++) {
+      var op = ops[i];
+      if (isRetain(op)) {
+        inverse.retain(op);
+        strIndex += op;
+      } else if (isInsert(op)) {
+        inverse['delete'](op.length);
+      } else { // delete op
+        inverse.insert(str.slice(strIndex, strIndex - op));
+        strIndex -= op;
+      }
+    }
+    return inverse;
+  };
+
+  // Compose merges two consecutive operations into one operation, that
+  // preserves the changes of both. Or, in other words, for each input string S
+  // and a pair of consecutive operations A and B,
+  // apply(apply(S, A), B) = apply(S, compose(A, B)) must hold.
+  TextOperation.prototype.compose = function (operation2) {
+    var operation1 = this;
+    if (operation1.targetLength !== operation2.baseLength) {
+      throw new Error("The base length of the second operation has to be the target length of the first operation");
+    }
+
+    var operation = new TextOperation(); // the combined operation
+    var ops1 = operation1.ops, ops2 = operation2.ops; // for fast access
+    var i1 = 0, i2 = 0; // current index into ops1 respectively ops2
+    var op1 = ops1[i1++], op2 = ops2[i2++]; // current ops
+    while (true) {
+      // Dispatch on the type of op1 and op2
+      if (typeof op1 === 'undefined' && typeof op2 === 'undefined') {
+        // end condition: both ops1 and ops2 have been processed
+        break;
+      }
+
+      if (isDelete(op1)) {
+        operation['delete'](op1);
+        op1 = ops1[i1++];
+        continue;
+      }
+      if (isInsert(op2)) {
+        operation.insert(op2);
+        op2 = ops2[i2++];
+        continue;
+      }
+
+      if (typeof op1 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too short.");
+      }
+      if (typeof op2 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too long.");
+      }
+
+      if (isRetain(op1) && isRetain(op2)) {
+        if (op1 > op2) {
+          operation.retain(op2);
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          operation.retain(op1);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation.retain(op1);
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+      } else if (isInsert(op1) && isDelete(op2)) {
+        if (op1.length > -op2) {
+          op1 = op1.slice(-op2);
+          op2 = ops2[i2++];
+        } else if (op1.length === -op2) {
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          op2 = op2 + op1.length;
+          op1 = ops1[i1++];
+        }
+      } else if (isInsert(op1) && isRetain(op2)) {
+        if (op1.length > op2) {
+          operation.insert(op1.slice(0, op2));
+          op1 = op1.slice(op2);
+          op2 = ops2[i2++];
+        } else if (op1.length === op2) {
+          operation.insert(op1);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation.insert(op1);
+          op2 = op2 - op1.length;
+          op1 = ops1[i1++];
+        }
+      } else if (isRetain(op1) && isDelete(op2)) {
+        if (op1 > -op2) {
+          operation['delete'](op2);
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (op1 === -op2) {
+          operation['delete'](op2);
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          operation['delete'](op1);
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+      } else {
+        throw new Error(
+          "This shouldn't happen: op1: " +
+          JSON.stringify(op1) + ", op2: " +
+          JSON.stringify(op2)
+        );
+      }
+    }
+    return operation;
+  };
+
+  function getSimpleOp (operation, fn) {
+    var ops = operation.ops;
+    var isRetain = TextOperation.isRetain;
+    switch (ops.length) {
+    case 1:
+      return ops[0];
+    case 2:
+      return isRetain(ops[0]) ? ops[1] : (isRetain(ops[1]) ? ops[0] : null);
+    case 3:
+      if (isRetain(ops[0]) && isRetain(ops[2])) { return ops[1]; }
+    }
+    return null;
+  }
+
+  function getStartIndex (operation) {
+    if (isRetain(operation.ops[0])) { return operation.ops[0]; }
+    return 0;
+  }
+
+  // When you use ctrl-z to undo your latest changes, you expect the program not
+  // to undo every single keystroke but to undo your last sentence you wrote at
+  // a stretch or the deletion you did by holding the backspace key down. This
+  // This can be implemented by composing operations on the undo stack. This
+  // method can help decide whether two operations should be composed. It
+  // returns true if the operations are consecutive insert operations or both
+  // operations delete text at the same position. You may want to include other
+  // factors like the time since the last change in your decision.
+  TextOperation.prototype.shouldBeComposedWith = function (other) {
+    if (this.isNoop() || other.isNoop()) { return true; }
+
+    var startA = getStartIndex(this), startB = getStartIndex(other);
+    var simpleA = getSimpleOp(this), simpleB = getSimpleOp(other);
+    if (!simpleA || !simpleB) { return false; }
+
+    if (isInsert(simpleA) && isInsert(simpleB)) {
+      return startA + simpleA.length === startB;
+    }
+
+    if (isDelete(simpleA) && isDelete(simpleB)) {
+      // there are two possibilities to delete: with backspace and with the
+      // delete key.
+      return (startB - simpleB === startA) || startA === startB;
+    }
+
+    return false;
+  };
+
+  // Decides whether two operations should be composed with each other
+  // if they were inverted, that is
+  // `shouldBeComposedWith(a, b) = shouldBeComposedWithInverted(b^{-1}, a^{-1})`.
+  TextOperation.prototype.shouldBeComposedWithInverted = function (other) {
+    if (this.isNoop() || other.isNoop()) { return true; }
+
+    var startA = getStartIndex(this), startB = getStartIndex(other);
+    var simpleA = getSimpleOp(this), simpleB = getSimpleOp(other);
+    if (!simpleA || !simpleB) { return false; }
+
+    if (isInsert(simpleA) && isInsert(simpleB)) {
+      return startA + simpleA.length === startB || startA === startB;
+    }
+
+    if (isDelete(simpleA) && isDelete(simpleB)) {
+      return startB - simpleB === startA;
+    }
+
+    return false;
+  };
+
+  // Transform takes two operations A and B that happened concurrently and
+  // produces two operations A' and B' (in an array) such that
+  // `apply(apply(S, A), B') = apply(apply(S, B), A')`. This function is the
+  // heart of OT.
+  TextOperation.transform = function (operation1, operation2) {
+    if (operation1.baseLength !== operation2.baseLength) {
+      throw new Error("Both operations have to have the same base length");
+    }
+
+    var operation1prime = new TextOperation();
+    var operation2prime = new TextOperation();
+    var ops1 = operation1.ops, ops2 = operation2.ops;
+    var i1 = 0, i2 = 0;
+    var op1 = ops1[i1++], op2 = ops2[i2++];
+    while (true) {
+      // At every iteration of the loop, the imaginary cursor that both
+      // operation1 and operation2 have that operates on the input string must
+      // have the same position in the input string.
+
+      if (typeof op1 === 'undefined' && typeof op2 === 'undefined') {
+        // end condition: both ops1 and ops2 have been processed
+        break;
+      }
+
+      // next two cases: one or both ops are insert ops
+      // => insert the string in the corresponding prime operation, skip it in
+      // the other one. If both op1 and op2 are insert ops, prefer op1.
+      if (isInsert(op1)) {
+        operation1prime.insert(op1);
+        operation2prime.retain(op1.length);
+        op1 = ops1[i1++];
+        continue;
+      }
+      if (isInsert(op2)) {
+        operation1prime.retain(op2.length);
+        operation2prime.insert(op2);
+        op2 = ops2[i2++];
+        continue;
+      }
+
+      if (typeof op1 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too short.");
+      }
+      if (typeof op2 === 'undefined') {
+        throw new Error("Cannot compose operations: first operation is too long.");
+      }
+
+      var minl;
+      if (isRetain(op1) && isRetain(op2)) {
+        // Simple case: retain/retain
+        if (op1 > op2) {
+          minl = op2;
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          minl = op2;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = op1;
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+        operation1prime.retain(minl);
+        operation2prime.retain(minl);
+      } else if (isDelete(op1) && isDelete(op2)) {
+        // Both operations delete the same string at the same position. We don't
+        // need to produce any operations, we just skip over the delete ops and
+        // handle the case that one operation deletes more than the other.
+        if (-op1 > -op2) {
+          op1 = op1 - op2;
+          op2 = ops2[i2++];
+        } else if (op1 === op2) {
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          op2 = op2 - op1;
+          op1 = ops1[i1++];
+        }
+      // next two cases: delete/retain and retain/delete
+      } else if (isDelete(op1) && isRetain(op2)) {
+        if (-op1 > op2) {
+          minl = op2;
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (-op1 === op2) {
+          minl = op2;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = -op1;
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+        operation1prime['delete'](minl);
+      } else if (isRetain(op1) && isDelete(op2)) {
+        if (op1 > -op2) {
+          minl = -op2;
+          op1 = op1 + op2;
+          op2 = ops2[i2++];
+        } else if (op1 === -op2) {
+          minl = op1;
+          op1 = ops1[i1++];
+          op2 = ops2[i2++];
+        } else {
+          minl = op1;
+          op2 = op2 + op1;
+          op1 = ops1[i1++];
+        }
+        operation2prime['delete'](minl);
+      } else {
+        throw new Error("The two operations aren't compatible");
+      }
+    }
+
+    return [operation1prime, operation2prime];
+  };
+
+  return TextOperation;
+
+}());
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.TextOperation;
+}

public/vendor/ot/undo-manager.js

@@ -0,0 +1,111 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.UndoManager = (function () {
+  'use strict';
+
+  var NORMAL_STATE = 'normal';
+  var UNDOING_STATE = 'undoing';
+  var REDOING_STATE = 'redoing';
+
+  // Create a new UndoManager with an optional maximum history size.
+  function UndoManager (maxItems) {
+    this.maxItems  = maxItems || 50;
+    this.state = NORMAL_STATE;
+    this.dontCompose = false;
+    this.undoStack = [];
+    this.redoStack = [];
+  }
+
+  // Add an operation to the undo or redo stack, depending on the current state
+  // of the UndoManager. The operation added must be the inverse of the last
+  // edit. When `compose` is true, compose the operation with the last operation
+  // unless the last operation was alread pushed on the redo stack or was hidden
+  // by a newer operation on the undo stack.
+  UndoManager.prototype.add = function (operation, compose) {
+    if (this.state === UNDOING_STATE) {
+      this.redoStack.push(operation);
+      this.dontCompose = true;
+    } else if (this.state === REDOING_STATE) {
+      this.undoStack.push(operation);
+      this.dontCompose = true;
+    } else {
+      var undoStack = this.undoStack;
+      if (!this.dontCompose && compose && undoStack.length > 0) {
+        undoStack.push(operation.compose(undoStack.pop()));
+      } else {
+        undoStack.push(operation);
+        if (undoStack.length > this.maxItems) { undoStack.shift(); }
+      }
+      this.dontCompose = false;
+      this.redoStack = [];
+    }
+  };
+
+  function transformStack (stack, operation) {
+    var newStack = [];
+    var Operation = operation.constructor;
+    for (var i = stack.length - 1; i >= 0; i--) {
+      var pair = Operation.transform(stack[i], operation);
+      if (typeof pair[0].isNoop !== 'function' || !pair[0].isNoop()) {
+        newStack.push(pair[0]);
+      }
+      operation = pair[1];
+    }
+    return newStack.reverse();
+  }
+
+  // Transform the undo and redo stacks against a operation by another client.
+  UndoManager.prototype.transform = function (operation) {
+    this.undoStack = transformStack(this.undoStack, operation);
+    this.redoStack = transformStack(this.redoStack, operation);
+  };
+
+  // Perform an undo by calling a function with the latest operation on the undo
+  // stack. The function is expected to call the `add` method with the inverse
+  // of the operation, which pushes the inverse on the redo stack.
+  UndoManager.prototype.performUndo = function (fn) {
+    this.state = UNDOING_STATE;
+    if (this.undoStack.length === 0) { throw new Error("undo not possible"); }
+    fn(this.undoStack.pop());
+    this.state = NORMAL_STATE;
+  };
+
+  // The inverse of `performUndo`.
+  UndoManager.prototype.performRedo = function (fn) {
+    this.state = REDOING_STATE;
+    if (this.redoStack.length === 0) { throw new Error("redo not possible"); }
+    fn(this.redoStack.pop());
+    this.state = NORMAL_STATE;
+  };
+
+  // Is the undo stack not empty?
+  UndoManager.prototype.canUndo = function () {
+    return this.undoStack.length !== 0;
+  };
+
+  // Is the redo stack not empty?
+  UndoManager.prototype.canRedo = function () {
+    return this.redoStack.length !== 0;
+  };
+
+  // Whether the UndoManager is currently performing an undo.
+  UndoManager.prototype.isUndoing = function () {
+    return this.state === UNDOING_STATE;
+  };
+
+  // Whether the UndoManager is currently performing a redo.
+  UndoManager.prototype.isRedoing = function () {
+    return this.state === REDOING_STATE;
+  };
+
+  return UndoManager;
+
+}());
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.UndoManager;
+}

public/vendor/ot/wrapped-operation.js

@@ -0,0 +1,80 @@
+if (typeof ot === 'undefined') {
+  // Export for browsers
+  var ot = {};
+}
+
+ot.WrappedOperation = (function (global) {
+  'use strict';
+
+  // A WrappedOperation contains an operation and corresponing metadata.
+  function WrappedOperation (operation, meta) {
+    this.wrapped = operation;
+    this.meta    = meta;
+  }
+
+  WrappedOperation.prototype.apply = function () {
+    return this.wrapped.apply.apply(this.wrapped, arguments);
+  };
+
+  WrappedOperation.prototype.invert = function () {
+    var meta = this.meta;
+    return new WrappedOperation(
+      this.wrapped.invert.apply(this.wrapped, arguments),
+      meta && typeof meta === 'object' && typeof meta.invert === 'function' ?
+        meta.invert.apply(meta, arguments) : meta
+    );
+  };
+
+  // Copy all properties from source to target.
+  function copy (source, target) {
+    for (var key in source) {
+      if (source.hasOwnProperty(key)) {
+        target[key] = source[key];
+      }
+    }
+  }
+
+  function composeMeta (a, b) {
+    if (a && typeof a === 'object') {
+      if (typeof a.compose === 'function') { return a.compose(b); }
+      var meta = {};
+      copy(a, meta);
+      copy(b, meta);
+      return meta;
+    }
+    return b;
+  }
+
+  WrappedOperation.prototype.compose = function (other) {
+    return new WrappedOperation(
+      this.wrapped.compose(other.wrapped),
+      composeMeta(this.meta, other.meta)
+    );
+  };
+
+  function transformMeta (meta, operation) {
+    if (meta && typeof meta === 'object') {
+      if (typeof meta.transform === 'function') {
+        return meta.transform(operation);
+      }
+    }
+    return meta;
+  }
+
+  WrappedOperation.transform = function (a, b) {
+    var transform = a.wrapped.constructor.transform;
+    var pair = transform(a.wrapped, b.wrapped);
+    return [
+      new WrappedOperation(pair[0], transformMeta(a.meta, b.wrapped)),
+      new WrappedOperation(pair[1], transformMeta(b.meta, a.wrapped))
+    ];
+  };
+
+  return WrappedOperation;
+
+}(this));
+
+// Export for CommonJS
+if (typeof module === 'object') {
+  module.exports = ot.WrappedOperation;
+}

public/views/body.ejs

@@ -58,7 +58,7 @@
                 <h4 class="modal-title" id="myModalLabel">This page need refresh</h4>
             </div>
             <div class="modal-body">
-                <h5>This page have a mismatch client version or incorrect user state.</h5>
+                <h5>This page have a mismatch client version or incorrect user state or errors.</h5>
                 <strong>Please refresh this page.</strong>
             </div>
             <div class="modal-footer">

public/views/foot.ejs

@@ -8,6 +8,8 @@
 <script src="/vendor/codemirror/codemirror.min.js" defer></script>
 <script src="/vendor/inlineAttachment/inline-attachment.js" defer></script>
 <script src="/vendor/inlineAttachment/codemirror.inline-attachment.js" defer></script>
+<!--ot-->
+<script src="/vendor/ot/ot.min.js" defer></script>
 <!--others-->
 <script src="/vendor/socket.io-1.3.5.js" defer></script>
 <script src="/vendor/remarkable.min.js" defer></script>