Move hello message from It2MeService to It2MeChannel

remoting/webapp/background/it2me_helper_channel.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
  *
  * It2MeHelperChannel relays messages between Hangouts and Chrome Remote Desktop
  * (webapp) for the helper (the Hangouts participant who is giving remote
  * assistance).
  *
  * It runs in the background page and contains two chrome.runtime.Port objects,
- * respresenting connections to the webapp and hangout, respectively.
+ * representing connections to the webapp and hangout, respectively.
  *
- * Connection is always initiated from Hangouts.
+ * Connection is always initiated from Hangouts by calling
+ *   var port = chrome.runtime.connect({name:'it2me.helper.hangout'}, extId).
+ *   port.postMessage('hello')
+ * If the webapp is not installed, |port.onDisconnect| will fire.
+ * If the webapp is installed, Hangouts will receive a hello response with the
+ * list of supported features.
  *
  *   Hangout                     It2MeHelperChannel        Chrome Remote Desktop
  *      |-----runtime.connect() ------>|                                |
- *      |------connect message-------->|                                |
+ *      |--------hello message-------->|                                |
+ *      |                              |<-----helloResponse message-----|
+ *      |-------connect message------->|                                |
  *      |                              |-------appLauncher.launch()---->|
  *      |                              |<------runtime.connect()------- |
  *      |                              |<-----sessionStateChanged------ |
  *      |<----sessionStateChanged------|                                |
  *
  * Disconnection can be initiated from either side:
  * 1. In the normal flow initiated from hangout
  *    Hangout                    It2MeHelperChannel        Chrome Remote Desktop
  *       |-----disconnect message------>|                               |
  *       |<-sessionStateChanged(CLOSED)-|                               |
@@ skipping 72 matching lines @@
   this.onDisconnectCallback_ = onDisconnectCallback;
 
   this.onWebappMessageRef_ = this.onWebappMessage_.bind(this);
   this.onWebappDisconnectRef_ = this.onWebappDisconnect_.bind(this);
   this.onHangoutMessageRef_ = this.onHangoutMessage_.bind(this);
   this.onHangoutDisconnectRef_ = this.onHangoutDisconnect_.bind(this);
 };
 
 /** @enum {string} */
 remoting.It2MeHelperChannel.HangoutMessageTypes = {
+  HELLO: 'hello',
+  HELLO_RESPONSE: 'helloResponse',
   CONNECT: 'connect',
-  DISCONNECT: 'disconnect'
+  DISCONNECT: 'disconnect',
+  SESSION_STATE_CHANGED: 'sessionStateChanged',
+  ERROR: 'error'
+};
+
+/** @enum {string} */
+remoting.It2MeHelperChannel.Features = {
+  REMOTE_ASSISTANCE: 'remoteAssistance'
 };
 
 /** @enum {string} */
 remoting.It2MeHelperChannel.WebappMessageTypes = {
-  SESSION_STATE_CHANGED: 'sessionStateChanged'
+  SESSION_STATE_CHANGED: 'sessionStateChanged',
+  ERROR: 'error'
 };
 
 remoting.It2MeHelperChannel.prototype.init = function() {
   this.hangoutPort_.onMessage.addListener(this.onHangoutMessageRef_);
   this.hangoutPort_.onDisconnect.addListener(this.onHangoutDisconnectRef_);
 };
 
 /** @return {string} */
 remoting.It2MeHelperChannel.prototype.instanceId = function() {
   return this.instanceId_;
 };
 
 /**
  * @param {{method:string, data:Object.<string,*>}} message
  * @return {boolean} whether the message is handled or not.
  * @private
  */
 remoting.It2MeHelperChannel.prototype.onHangoutMessage_ = function(message) {
   try {
     var MessageTypes = remoting.It2MeHelperChannel.HangoutMessageTypes;
     switch (message.method) {
       case MessageTypes.CONNECT:
         this.launchWebapp_(message);
         return true;
       case MessageTypes.DISCONNECT:
         this.closeWebapp_(message);
         return true;
+      case MessageTypes.HELLO:
+        this.hangoutPort_.postMessage({
+          method: MessageTypes.HELLO_RESPONSE,
+          supportedFeatures: base.values(remoting.It2MeHelperChannel.Features)
+        });
+        return true;
     }
+    throw new Error('Unknown message method=' + message.method);
   } catch(e) {
     var error = /** @type {Error} */ e;
     console.error(error);
     this.hangoutPort_.postMessage({
-      method: message.method + 'Response',
+      method: MessageTypes.ERROR,

[Jamie, 2014/08/15 21:57:31]

My comment about appending "Response" was just in relation to the hello message.
I do prefer a dedicated error response, but I don't think it belongs in this CL.
I think the changes needed to support it are more far-reaching; specifically,
there's no longer any need to include an "error" field in every message.

[kelvinp, 2014/08/15 23:25:01]

I will make the change in error in later CL's

       error: error.message
     });
   }
   return false;
 };
 
 /**
  * Disconnect the existing connection to the helpee.
  *
  * @param {{method:string, data:Object.<string,*>}} message
  * @private
  */
 remoting.It2MeHelperChannel.prototype.closeWebapp_ =
     function(message) {
   // TODO(kelvinp): Closing the v2 app currently doesn't disconnect the IT2me
   // session (crbug.com/402137), so send an explicit notification to Hangouts.
+  var MessageTypes = remoting.It2MeHelperChannel.HangoutMessageTypes;
   this.sessionState_ = remoting.ClientSession.State.CLOSED;
   this.hangoutPort_.postMessage({
-    method: 'sessionStateChanged',
+    method: MessageTypes.SESSION_STATE_CHANGED,
     state: this.sessionState_
   });
   this.appLauncher_.close(this.instanceId_);
 };
 
 /**
  * Launches the web app.
  *
  * @param {{method:string, data:Object.<string,*>}} message
  * @private
@@ skipping 40 matching lines @@
   port.onMessage.addListener(this.onWebappMessageRef_);
   port.onDisconnect.addListener(this.onWebappDisconnectRef_);
   this.webappPort_ = port;
 };
 
 /** @param {chrome.runtime.Port} port The webapp port. */
 remoting.It2MeHelperChannel.prototype.onWebappDisconnect_ = function(port) {
   // If the webapp port got disconnected while the session is still connected,
   // treat it as an error.
   var States = remoting.ClientSession.State;
+  var HangoutMessageTypes = remoting.It2MeHelperChannel.HangoutMessageTypes;
   if (this.sessionState_ === States.CONNECTING ||
       this.sessionState_ === States.CONNECTED) {
     this.sessionState_ = States.FAILED;
     this.hangoutPort_.postMessage({
-      method: 'sessionStateChanged',
+      method: HangoutMessageTypes.SESSION_STATE_CHANGED,
       state: this.sessionState_
     });
   }
   this.unhookPorts_();
 };
 
 /**
  * @param {{method:string, data:Object.<string,*>}} message
  * @private
  */
 remoting.It2MeHelperChannel.prototype.onWebappMessage_ = function(message) {
   try {
     console.log('It2MeHelperChannel id=' + this.instanceId_ +
                 ' incoming message method=' + message.method);
-    var MessageTypes = remoting.It2MeHelperChannel.WebappMessageTypes;
+    var WebappMessageTypes = remoting.It2MeHelperChannel.WebappMessageTypes;
+    var HangoutMessageTypes = remoting.It2MeHelperChannel.HangoutMessageTypes;
     switch (message.method) {
-      case MessageTypes.SESSION_STATE_CHANGED:
+      case WebappMessageTypes.SESSION_STATE_CHANGED:
         var state = getNumberAttr(message, 'state');
-        this.sessionState_ =
-            /** @type {remoting.ClientSession.State} */ state;
-        this.hangoutPort_.postMessage(message);
+        this.sessionState_ = /** @type {remoting.ClientSession.State} */ state;
+        this.hangoutPort_.postMessage({
+          method: HangoutMessageTypes.SESSION_STATE_CHANGED,
+          state: state
+        });

[Jamie, 2014/08/15 21:57:31]

As above, I like this change, but it doesn't really relate to what this CL is
doing, and should be kept separate.

         return true;
     }
     throw new Error('Unknown message method=' + message.method);
   } catch(e) {
     var error = /** @type {Error} */ e;
     console.error(error);
     this.webappPort_.postMessage({
-      method: message.method + 'Response',
+      method: WebappMessageTypes.ERROR,
       error: error.message
     });
   }
   return false;
 };
 
 remoting.It2MeHelperChannel.prototype.unhookPorts_ = function() {
   if (this.webappPort_) {
     this.webappPort_.onMessage.removeListener(this.onWebappMessageRef_);
     this.webappPort_.onDisconnect.removeListener(this.onWebappDisconnectRef_);
     this.webappPort_.disconnect();
     this.webappPort_ = null;
   }
 
   if (this.hangoutPort_) {
     this.hangoutPort_.onMessage.removeListener(this.onHangoutMessageRef_);
     this.hangoutPort_.onDisconnect.removeListener(this.onHangoutDisconnectRef_);
     this.hangoutPort_.disconnect();
     this.hangoutPort_ = null;
   }
 
   if (this.onDisconnectCallback_) {
     this.onDisconnectCallback_(this);
     this.onDisconnectCallback_  = null;
   }
 };