CastExtensionHandler for Chromoting Webapp

remoting/webapp/cast_extension_handler.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview Description of this file.
+ * Class handling interaction with the cast extension session of the Chromoting
+ * host. It receives and sends extension messages from/to the host through
+ * the client session. It uses the Google Cast Chrome Sender API library to
+ * interact with nearby Cast receivers.
+ *
+ * Once it establishes connection with a Cast device (upon user choice), it
+ * creates a session, loads our registered receiver application and then becomes
+ * a message proxy between the host and cast device, helping negotiate
+ * their peer connection.
+ */
+
+'use strict';
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+/**
+ * @constructor
+ * @param {!remoting.ClientSession} clientSession The client session to send
+ * cast extension messages to.
+ */
+remoting.CastExtensionHandler = function(clientSession) {
+  /** @private */
+  this.clientSession_ = clientSession;
+
+  /** @type {chrome.cast.Session} @private */
+  this.session_ = null;
+
+  /** @type {string} @private */
+  this.kCastNamespace_ = 'urn:x-cast:com.chromoting.cast.all';
+
+  /** @type {string} @private */
+  this.kApplicationId_ = "8A1211E3";
+
+  /** @type {Array.<Object>} @private */
+  this.messageQueue_ = [];
+
+  this.start_();
+};
+
+/**
+ * The id of the script node.
+ * @type {string}
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.SCRIPT_NODE_ID_ = 'cast-script-node';
+
+/**
+ * Attempts to load the Google Cast Chrome Sender API libary.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.start_ = function() {
+  var node = document.getElementById(this.SCRIPT_NODE_ID_);
+  if (node) {
+    console.error(
+        'Multiple calls to CastExtensionHandler.start_ not expected.');
+    return;
+  }
+
+  // Create a script node to load the Cast Sender API.
+  node = document.createElement('script');
+  node.id = this.SCRIPT_NODE_ID_;
+  node.src = "https://www.gstatic.com/cv/js/sender/v1/cast_sender.js";
+  node.type = 'text/javascript';
+  document.body.insertBefore(node, document.body.firstChild);
+
+  /** @type {remoting.CastExtensionHandler} */
+  var that = this;
+  var onLoad = function() {
+    window['__onGCastApiAvailable'] = that.onGCastApiAvailable.bind(that);
+
+  };
+  var onLoadError = function(event) {
+    console.error("Failed to load Chrome Cast Sender API.");
+  }
+  node.addEventListener('load', onLoad, false);
+  node.addEventListener('error', onLoadError, false);
+
+};
+
+/**
+ * Process Cast Extension Messages from the Chromoting host.
+ * @param {string} msgString The extension message's data.
+ */
+remoting.CastExtensionHandler.prototype.onMessage = function(msgString) {
+  var message = getJsonObjectFromString(msgString);
+
+  // Save messages to send after a session is established.
+  this.messageQueue_.push(message);
+  // Trigger the sending of pending messages, followed by the one just
+  // received.
+  if (this.session_) {
+    this.sendPendingMessages_();
+  }
+};
+
+/**
+ * Send cast-extension messages through the client session.
+ * @param {Object} response The JSON response to be sent to the host. The
+ * response object must contain the appropriate keys.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.sendMessageToHost_ =
+    function(response) {
+  this.clientSession_.sendCastExtensionMessage(response);
+};
+
+/**
+ * Send pending messages from the host to the receiver app.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.sendPendingMessages_ = function() {
+  var len = this.messageQueue_.length;
+  for(var i = 0; i<len; i++) {
+    this.session_.sendMessage(this.kCastNamespace_,
+                              this.messageQueue_[i],
+                              this.sendMessageSuccess.bind(this),
+                              this.sendMessageFailure.bind(this));
+  }
+  this.messageQueue_ = [];
+};
+
+/**
+ * Event handler for '__onGCastApiAvailable' window event. This event is
+ * triggered if the Google Cast Chrome Sender API is available. We attempt to
+ * load this API in this.start(). If the API loaded successfully, we can proceed
+ * to initialize it and configure it to launch our Cast Receiver Application.
+ *
+ * @param {boolean} loaded True if the API loaded succesfully.
+ * @param {Object} errorInfo Info if the API load failed.
+ */
+remoting.CastExtensionHandler.prototype.onGCastApiAvailable =
+    function(loaded, errorInfo) {
+  if (loaded) {
+    this.initializeCastApi();
+  } else {
+    console.log(errorInfo);
+  }
+};
+
+/**
+ * Initialize the Cast API.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.initializeCastApi = function() {
+  var sessionRequest = new chrome.cast.SessionRequest(this.kApplicationId_);
+  var apiConfig =
+      new chrome.cast.ApiConfig(sessionRequest,
+                                this.sessionListener.bind(this),
+                                this.receiverListener.bind(this),
+                                chrome.cast.AutoJoinPolicy.PAGE_SCOPED,
+                                chrome.cast.DefaultActionPolicy.CREATE_SESSION);
+  chrome.cast.initialize(
+      apiConfig, this.onInitSuccess.bind(this), this.onInitError.bind(this));
+};
+
+/**
+ * Callback for successful initialization of the Cast API.
+ */
+remoting.CastExtensionHandler.prototype.onInitSuccess = function() {
+  console.log("Initialization Successful.");
+};
+
+/**
+ * Callback for failed initialization of the Cast API.
+ */
+remoting.CastExtensionHandler.prototype.onInitError = function() {
+  console.error("Initialization Failed.");
+};
+
+/**
+ * Listener invoked when a session is created or connected by the SDK.
+ * Note: The requestSession method would not cause this callback to be invoked
+ * since it is passed its own listener.
+ * @param {chrome.cast.Session} session The resulting session.
+ */
+remoting.CastExtensionHandler.prototype.sessionListener = function(session) {
+  console.log('New Session:' + /** @type {string} */ (session.sessionId));
+  this.session_ = session;
+  if (this.session_.media.length != 0) {
+
+    // There should be no media associated with the session, since we never
+    // directly load media from the Sender application.
+    this.onMediaDiscovered('sessionListener', this.session_.media[0]);
+  }
+  this.session_.addMediaListener(
+      this.onMediaDiscovered.bind(this, 'addMediaListener'));
+  this.session_.addUpdateListener(this.sessionUpdateListener.bind(this));
+  this.session_.addMessageListener(this.kCastNamespace_,
+                                   this.chromotingMessageListener.bind(this));
+  this.session_.sendMessage(this.kCastNamespace_,
+      {subject : 'test', chromoting_data : 'Hello, Cast.'},
+      this.sendMessageSuccess.bind(this),
+      this.sendMessageFailure.bind(this));
+  this.sendPendingMessages_();
+};
+
+/**
+ * Listener invoked when a media session is created by another sender.
+ * @param {string} how How this callback was triggered.
+ * @param {chrome.cast.media.Media} media The media item discovered.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.onMediaDiscovered =
+    function(how, media) {
+      console.error("Unexpected media session discovered.");
+};
+
+/**
+ * Listener invoked when a cast extension message was sent to the cast device
+ * successfully.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.sendMessageSuccess = function() {
+};
+
+/**
+ * Listener invoked when a cast extension message failed to be sent to the cast
+ * device.
+ * @param {Object} error The error.
+ * @private
+ */
+remoting.CastExtensionHandler.prototype.sendMessageFailure = function(error) {
+  console.error('Failed to Send Message.', error);
+};
+
+/**
+ * Listener invoked when a cast extension message is received from the Cast
+ * device.
+ * @param {string} ns The namespace of the message received.
+ * @param {string} message The stringified JSON message received.
+ */
+remoting.CastExtensionHandler.prototype.chromotingMessageListener =
+    function(ns, message) {
+  if (ns === this.kCastNamespace_) {
+    try {
+        var messageObj = getJsonObjectFromString(message);
+        this.sendMessageToHost_(messageObj);
+    } catch (err) {
+      console.error('Failed to process message from Cast device.');
+    }
+  } else {
+    console.error("Unexpected message from Cast device.");
+  }
+};
+
+/**
+ * Listener invoked when there updates to the current session.
+ *
+ * @param {boolean} isAlive True if the session is still alive.
+ */
+remoting.CastExtensionHandler.prototype.sessionUpdateListener =
+    function(isAlive) {
+  var message = isAlive ? 'Session Updated' : 'Session Removed';
+  message += ': ' + this.session_.sessionId +'.';
+  console.log(message);
+};
+
+/**
+ * Listener invoked when the availability of a Cast receiver that supports
+ * the application in sessionRequest is known or changes.
+ *
+ * @param {chrome.cast.ReceiverAvailability} availability Receiver availability.
+ */
+remoting.CastExtensionHandler.prototype.receiverListener =
+    function(availability) {
+  if (availability === chrome.cast.ReceiverAvailability.AVAILABLE) {
+    console.log("Receiver(s) Found.");
+  } else {
+    console.error("No Receivers Available.");
+  }
+};
+
+/**
+ * Launches the associated receiver application by requesting that it be created
+ * on the Cast device. It uses the SessionRequest passed during initialization
+ * to determine what application to launch on the Cast device.
+ *
+ * Note: This method is intended to be used as a click listener for a custom
+ * cast button on the webpage. We currently use the default cast button in
+ * Chrome, so this method is unused.
+ */
+remoting.CastExtensionHandler.prototype.launchApp = function() {
+  chrome.cast.requestSession(this.onRequestSessionSuccess.bind(this),
+                             this.onLaunchError.bind(this));
+};
+
+/**
+ * Listener invoked when chrome.cast.requestSession completes successfully.
+ *
+ * @param {chrome.cast.Session} session The requested session.
+ */
+remoting.CastExtensionHandler.prototype.onRequestSessionSuccess =
+    function (session) {
+  this.session_ = session;
+  this.session_.addUpdateListener(this.sessionUpdateListener.bind(this));
+  if (this.session_.media.length != 0) {
+    this.onMediaDiscovered('onRequestSession', this.session_.media[0]);
+  }
+  this.session_.addMediaListener(
+      this.onMediaDiscovered.bind(this, 'addMediaListener'));
+  this.session_.addMessageListener(this.kCastNamespace_,
+                                   this.chromotingMessageListener.bind(this));
+};
+
+/**
+ * Listener invoked when chrome.cast.requestSession fails.
+ * @param {chrome.cast.Error} error The error code.
+ */
+remoting.CastExtensionHandler.prototype.onLaunchError = function(error) {
+  console.error("Error Casting to Receiver.", error);
+};
+
+/**
+ * Stops the running receiver application associated with the session.
+ * TODO(aiguha): When the user disconnects using the blue drop down bar,
+ * the client session should notify the CastExtensionHandler, which should
+ * call this method to close the session with the Cast device.
+ */
+remoting.CastExtensionHandler.prototype.stopApp = function() {
+  this.session_.stop(this.onStopAppSuccess.bind(this),
+                     this.onStopAppError.bind(this));
+};
+
+/**
+ * Listener invoked when the receiver application is stopped successfully.
+ */
+remoting.CastExtensionHandler.prototype.onStopAppSuccess = function() {
+};
+
+/**
+ * Listener invoked when we fail to stop the receiver application.
+ *
+ * @param {chrome.cast.Error} error The error code.
+ */
+remoting.CastExtensionHandler.prototype.onStopAppError = function(error) {
+  console.error('Error Stopping App: ', error);
+};