chrome/browser/resources/gaia_auth/channel.js

   1 // Copyright 2013 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  * Channel to the background script.
   7  */
   8 function Channel() {
   9 }
  10
  11 /** @const */
  12 Channel.INTERNAL_REQUEST_MESSAGE = 'internal-request-message';
  13
  14 /** @const */
  15 Channel.INTERNAL_REPLY_MESSAGE = 'internal-reply-message';
  16
  17 Channel.prototype = {
  18   // Message port to use to communicate with background script.
  19   port_: null,
  20
  21   // Registered message callbacks.
  22   messageCallbacks_: {},
  23
  24   // Internal request id to track pending requests.
  25   nextInternalRequestId_: 0,
  26
  27   // Pending internal request callbacks.
  28   internalRequestCallbacks_: {},
  29
  30   /**
  31    * Initialize the channel with given port for the background script.
  32    */
  33   init: function(port) {
  34     this.port_ = port;
  35     this.port_.onMessage.addListener(this.onMessage_.bind(this));
  36   },
  37
  38   /**
  39    * Connects to the background script with the given name.
  40    */
  41   connect: function(name) {
  42     this.port_ = chrome.runtime.connect({name: name});
  43     this.port_.onMessage.addListener(this.onMessage_.bind(this));
  44   },
  45
  46   /**
  47    * Associates a message name with a callback. When a message with the name
  48    * is received, the callback will be invoked with the message as its arg.
  49    * Note only the last registered callback will be invoked.
  50    */
  51   registerMessage: function(name, callback) {
  52     this.messageCallbacks_[name] = callback;
  53   },
  54
  55   /**
  56    * Sends a message to the other side of the channel.
  57    */
  58   send: function(msg) {
  59     this.port_.postMessage(msg);
  60   },
  61
  62   /**
  63    * Sends a message to the other side and invokes the callback with
  64    * the replied object. Useful for message that expects a returned result.
  65    */
  66   sendWithCallback: function(msg, callback) {
  67     var requestId = this.nextInternalRequestId_++;
  68     this.internalRequestCallbacks_[requestId] = callback;
  69     this.send({
  70       name: Channel.INTERNAL_REQUEST_MESSAGE,
  71       requestId: requestId,
  72       payload: msg
  73     });
  74   },
  75
  76   /**
  77    * Invokes message callback using given message.
  78    * @return {*} The return value of the message callback or null.
  79    */
  80   invokeMessageCallbacks_: function(msg) {
  81     var name = msg.name;
  82     if (this.messageCallbacks_[name])
  83       return this.messageCallbacks_[name](msg);
  84
  85     console.error('Error: Unexpected message, name=' + name);
  86     return null;
  87   },
  88
  89   /**
  90    * Invoked when a message is received.
  91    */
  92   onMessage_: function(msg) {
  93     var name = msg.name;
  94     if (name == Channel.INTERNAL_REQUEST_MESSAGE) {
  95       var payload = msg.payload;
  96       var result = this.invokeMessageCallbacks_(payload);
  97       this.send({
  98         name: Channel.INTERNAL_REPLY_MESSAGE,
  99         requestId: msg.requestId,
 100         result: result
 101       });
 102     } else if (name == Channel.INTERNAL_REPLY_MESSAGE) {
 103       var callback = this.internalRequestCallbacks_[msg.requestId];
 104       delete this.internalRequestCallbacks_[msg.requestId];
 105       if (callback)
 106         callback(msg.result);
 107     } else {
 108       this.invokeMessageCallbacks_(msg);
 109     }
 110   }
 111 };