Use WsChannel to handle media webrtc handshake

src/packages/collaboration/lib/media-connection.coffee

@@ -6,13 +6,12 @@ module.exports =
 class MediaConnection
   _.extend @prototype, require('event-emitter')
 
-  local: null
-  remote: null
+  channel: null
   connection: null
   stream: null
   isLeader: null
 
-  constructor: (@local, @remote, {@isLeader}={}) ->
+  constructor: (@channel, {@isLeader}={}) ->
 
   start: ->
     video = config.get('collaboration.enableVideo') ? true
@@ -31,40 +30,44 @@ class MediaConnection
   onUserMediaAvailable: (stream) =>
     @connection = new webkitRTCPeerConnection(sessionUtils.getIceServers())
     @connection.addStream(stream)
-    @remote.on 'changed', @onRemoteSignal
+    @channel.on 'media-handshake', (event) =>
+      try
+        @onSignal(event)
+      catch e
+        console.error event
+        throw e
 
     @connection.onicecandidate = (event) =>
       return unless event.candidate?
-      @local.set 'candidate', event.candidate
+      @channel.send 'media-handshake', {candidate: event.candidate}
 
     @connection.onaddstream = (event) =>
       @stream = event.stream
       @trigger 'stream-ready', @stream
 
-    @local.set 'ready', true unless @isLeader
+    unless @isLeader
+      @channel.send 'media-handshake', {ready: true}
 
-  onRemoteSignal: ({key, newValue}) =>
-    switch key
-      when 'ready'
-        success = (description) =>
-          @connection.setLocalDescription(description)
-          @local.set 'description', description
-        @connection.createOffer success, console.error
+  onSignal: (event) =>
+    if value = event.ready
+      success = (description) =>
+        @connection.setLocalDescription(description)
+        @channel.send 'media-handshake', {description}
+      @connection.createOffer success, console.error
 
-      when 'description'
-        remoteDescription = newValue.toObject()
-        sessionDescription = new RTCSessionDescription(remoteDescription)
-        @connection.setRemoteDescription(sessionDescription)
+    else if value = event.description
+      remoteDescription = value
+      sessionDescription = new RTCSessionDescription(remoteDescription)
+      @connection.setRemoteDescription(sessionDescription)
 
-        if not @isLeader
-          success = (localDescription) =>
-            @connection.setLocalDescription(localDescription)
-            @local.set('description', localDescription)
-          @connection.createAnswer success, console.error
+      if not @isLeader
+        success = (localDescription) =>
+          @connection.setLocalDescription(localDescription)
+          @channel.send 'media-handshake', {description: localDescription}
+        @connection.createAnswer success, console.error
 
-      when 'candidate'
-        remoteCandidate = new RTCIceCandidate newValue.toObject()
-        @connection.addIceCandidate(remoteCandidate)
-
-      else
-        throw new Error("Unknown remote key '#{key}'")
+    else if value = event.candidate
+      remoteCandidate = new RTCIceCandidate value
+      @connection.addIceCandidate(remoteCandidate)
+    else
+      throw new Error("Unknown remote key '#{event}'")

src/packages/collaboration/lib/session.coffee

@@ -80,12 +80,7 @@ class Session
             @trigger 'started', @getParticipants()
 
   createMediaConnection: ->
-    guest = @doc.get('collaborationState.guest')
-    host = @doc.get('collaborationState.host')
-    if @isLeader()
-      new MediaConnection(guest, host, isLeader: true)
-    else
-      new MediaConnection(host, guest)
+    new MediaConnection(@channel, isLeader: @isLeader())
 
   waitForStream: (callback) ->
     @mediaConnection.waitForStream callback