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   this.messageCallbacks_ = {};
  10   this.internalRequestCallbacks_ = {};
  11 }
  12
  13 /** @const */
  14 Channel.INTERNAL_REQUEST_MESSAGE = 'internal-request-message';
  15
  16 /** @const */
  17 Channel.INTERNAL_REPLY_MESSAGE = 'internal-reply-message';
  18
  19 Channel.prototype = {
  20   // Message port to use to communicate with background script.
  21   port_: null,
  22
  23   // Registered message callbacks.
  24   messageCallbacks_: null,
  25
  26   // Internal request id to track pending requests.
  27   nextInternalRequestId_: 0,
  28
  29   // Pending internal request callbacks.
  30   internalRequestCallbacks_: null,
  31
  32   /**
  33    * Initialize the channel with given port for the background script.
  34    */
  35   init: function(port) {
  36     this.port_ = port;
  37     this.port_.onMessage.addListener(this.onMessage_.bind(this));
  38   },
  39
  40   /**
  41    * Connects to the background script with the given name.
  42    */
  43   connect: function(name) {
  44     this.port_ = chrome.runtime.connect({name: name});
  45     this.port_.onMessage.addListener(this.onMessage_.bind(this));
  46   },
  47
  48   /**
  49    * Associates a message name with a callback. When a message with the name
  50    * is received, the callback will be invoked with the message as its arg.
  51    * Note only the last registered callback will be invoked.
  52    */
  53   registerMessage: function(name, callback) {
  54     this.messageCallbacks_[name] = callback;
  55   },
  56
  57   /**
  58    * Sends a message to the other side of the channel.
  59    */
  60   send: function(msg) {
  61     this.port_.postMessage(msg);
  62   },
  63
  64   /**
  65    * Sends a message to the other side and invokes the callback with
  66    * the replied object. Useful for message that expects a returned result.
  67    */
  68   sendWithCallback: function(msg, callback) {
  69     var requestId = this.nextInternalRequestId_++;
  70     this.internalRequestCallbacks_[requestId] = callback;
  71     this.send({
  72       name: Channel.INTERNAL_REQUEST_MESSAGE,
  73       requestId: requestId,
  74       payload: msg
  75     });
  76   },
  77
  78   /**
  79    * Invokes message callback using given message.
  80    * @return {*} The return value of the message callback or null.
  81    */
  82   invokeMessageCallbacks_: function(msg) {
  83     var name = msg.name;
  84     if (this.messageCallbacks_[name])
  85       return this.messageCallbacks_[name](msg);
  86
  87     console.error('Error: Unexpected message, name=' + name);
  88     return null;
  89   },
  90
  91   /**
  92    * Invoked when a message is received.
  93    */
  94   onMessage_: function(msg) {
  95     var name = msg.name;
  96     if (name == Channel.INTERNAL_REQUEST_MESSAGE) {
  97       var payload = msg.payload;
  98       var result = this.invokeMessageCallbacks_(payload);
  99       this.send({
 100         name: Channel.INTERNAL_REPLY_MESSAGE,
 101         requestId: msg.requestId,
 102         result: result
 103       });
 104     } else if (name == Channel.INTERNAL_REPLY_MESSAGE) {
 105       var callback = this.internalRequestCallbacks_[msg.requestId];
 106       delete this.internalRequestCallbacks_[msg.requestId];
 107       if (callback)
 108         callback(msg.result);
 109     } else {
 110       this.invokeMessageCallbacks_(msg);
 111     }
 112   }
 113 };
 114
 115 /**
 116  * Class factory.
 117  * @return {Channel}
 118  */
 119 Channel.create = function() {
 120   return new Channel();
 121 };