remoting/webapp/base/js/window_message_dispatcher.js

   1 /* Copyright 2015 The Chromium Authors. All rights reserved.
   2  * Use of this source code is governed by a BSD-style license that can be
   3  * found in the LICENSE file.
   4  */
   5
   6 /**
   7  * @fileoverview
   8  * This class dispatches window messages (those sent using window.postMessage)
   9  * from different sources to the registered handlers.
  10  * This should be the only 'message' event listener in this app. Anyone who
  11  * wants to listen to window messages should register with this class.
  12  */
  13
  14 'use strict';
  15
  16 /** @suppress {duplicate} */
  17 var base = base || {};
  18
  19 (function() {
  20 /**
  21  * @constructor
  22  * @implements {base.Disposable}
  23  */
  24 base.WindowMessageDispatcher = function() {
  25   /** @private {Object<string, function(Event):void>} */
  26   this.handlers_ = {};
  27
  28   /** @private */
  29   this.eventHook_ = new base.DomEventHook(
  30       window, 'message', this.onMessage_.bind(this), false);
  31 };
  32
  33 base.WindowMessageDispatcher.prototype.dispose = function() {
  34   this.unregisterAllHandlers();
  35
  36   base.dispose(this.eventHook_);
  37   this.eventHook_ = null;
  38 };
  39
  40 /**
  41  * @param {string} source Message source to register handler for.
  42  * @param {function(Event):void} handler Handler for the messages from |source|.
  43  * @return {void}
  44  */
  45 base.WindowMessageDispatcher.prototype.registerMessageHandler =
  46     function(source, handler) {
  47   console.assert(Boolean(source), 'No source specified.');
  48   console.assert(Boolean(handler), 'No handler specified.');
  49
  50   if (source in this.handlers_) {
  51     console.error('Cannot register more than one handler for source: ', source);
  52   } else {
  53     this.handlers_[source] = handler;
  54   }
  55 };
  56
  57 /**
  58  * @param {string} source Message source to unregister handler for.
  59  * @return {void}
  60  */
  61 base.WindowMessageDispatcher.prototype.unregisterMessageHandler =
  62     function(source) {
  63   console.assert(Boolean(source), 'No source specified.');
  64
  65   if (source in this.handlers_) {
  66     delete this.handlers_[source];
  67   } else {
  68     console.error('Message handler doesn\'t exist for source: ', source);
  69   }
  70 };
  71
  72 /**
  73  * @return {void}
  74  */
  75 base.WindowMessageDispatcher.prototype.unregisterAllHandlers = function() {
  76   this.handlers_ = {};
  77 };
  78
  79 /**
  80  * Event handler to process window messages.
  81  *
  82  * @param {Event} event
  83  */
  84 base.WindowMessageDispatcher.prototype.onMessage_ = function(event) {
  85   var data = event.data;
  86   if (typeof data === 'object') {
  87     /** @type {string} */
  88     var source = data['source'];
  89     if (source === undefined) {
  90       console.error('Missing source field in incoming message: ', data);
  91       return;
  92     }
  93
  94     console.log('object message received from: ', source);
  95     var handler = this.handlers_[source];
  96     if (handler) {
  97       handler(event);
  98     } else {
  99       console.error('No handler registered for messages from: ', source);
 100     }
 101   } else {
 102     console.error('Unknown window message data type: ', data);
 103   }
 104 };
 105
 106 })();