Create PeerConnection when PeerConnectionChannel is created. (#532)

* Create PeerConnection when PeerConnectionChannel is created.

This change allows application to get PeerConnection before publishing
or subscribing. Then the application can create RTCRtpTransceivers on
the PeerConnection returned, and publish a stream with
RTCRtpTransceivers pre-configurated.

* Notify ConferenceClient when a new publication ID is ready.

This is actually not needed because conference server supports multiple
streams on a single PeerConnection, so only a single
PeerConnectionChannel is created. But let's keep the old behavior until
ConferenceClient is updated.

Author: jianjunz

src/sdk/conference/channel.js

@@ -61,6 +61,8 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
     this._sdpResolvers = []; // [{finish, resolve, reject}]
     this._sdpResolveNum = 0;
     this._remoteMediaStreams = new Map(); // Key is subscription ID, value is MediaStream.
+
+    this._createPeerConnection();
   }
 
   /**
@@ -129,14 +131,29 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
           mid: t.mid,
         };
       });
-      const publicationId =
-          await this._signaling.sendSignalingMessage('publish', {
-            media: {tracks: trackOptions},
-            attributes: stream.attributes,
-            transport: {id: this._id, type: 'webrtc'},
-          }).id;
+      const publicationResp =
+        await this._signaling.sendSignalingMessage('publish', {
+          media: {tracks: trackOptions},
+          attributes: stream.attributes,
+          transport: {id: this._id, type: 'webrtc'},
+        });
+      const publicationId = publicationResp.id;
       this._publishTransceivers.get(internalId).id = publicationId;
       this._reverseIdMap.set(publicationId, internalId);
+
+      if (this._id && this._id !== publicationResp.transportId) {
+        Logger.warning('Server returns conflict ID: ' + publicationResp
+            .transportId);
+        return;
+      }
+      this._id = publicationResp.transportId;
+
+      const messageEvent = new MessageEvent('id', {
+        message: publicationId,
+        origin: this._remoteId,
+      });
+      this.dispatchEvent(messageEvent);
+
       await this._signaling.sendSignalingMessage(
           'soac', {id: this._id, signaling: offer});
       return new Promise((resolve, reject) => {
@@ -223,7 +240,6 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
       }
     }
     const mediaOptions = {};
-    this._createPeerConnection();
     if (stream.mediaStream.getAudioTracks().length > 0 && options.audio !==
       false && options.audio !== null) {
       if (stream.mediaStream.getAudioTracks().length > 1) {
@@ -373,20 +389,21 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
       });
     }).then((data) => {
       const publicationId = data.id;
-      const messageEvent = new MessageEvent('id', {
-        message: publicationId,
-        origin: this._remoteId,
-      });
-      this.dispatchEvent(messageEvent);
-
       this._publishTransceivers.get(internalId).id = publicationId;
       this._reverseIdMap.set(publicationId, internalId);
 
       if (this._id && this._id !== data.transportId) {
         Logger.warning('Server returns conflict ID: ' + data.transportId);
+        return;
       }
       this._id = data.transportId;
 
+      const messageEvent = new MessageEvent('id', {
+        message: publicationId,
+        origin: this._remoteId,
+      });
+      this.dispatchEvent(messageEvent);
+
       // Modify local SDP before sending
       if (options) {
         transceivers.forEach(({type, transceiver, option}) => {
@@ -511,7 +528,6 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
 
     const offerOptions = {};
     const transceivers = [];
-    this._createPeerConnection();
     if (typeof this.pc.addTransceiver === 'function') {
       // |direction| seems not working on Safari.
       if (mediaOptions.audio) {
@@ -577,19 +593,20 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
       });
     }).then((data) => {
       const subscriptionId = data.id;
-      const messageEvent = new MessageEvent('id', {
-        message: subscriptionId,
-        origin: this._remoteId,
-      });
-      this.dispatchEvent(messageEvent);
-
       this._subscribeTransceivers.get(internalId).id = subscriptionId;
       this._reverseIdMap.set(subscriptionId, internalId);
       if (this._id && this._id !== data.transportId) {
         Logger.warning('Server returns conflict ID: ' + data.transportId);
+        return;
       }
       this._id = data.transportId;
 
+      const messageEvent = new MessageEvent('id', {
+        message: subscriptionId,
+        origin: this._remoteId,
+      });
+      this.dispatchEvent(messageEvent);
+
       // Modify local SDP before sending
       if (options) {
         transceivers.forEach(({type, transceiver, option}) => {
@@ -898,6 +915,8 @@ export class ConferencePeerConnectionChannel extends EventDispatcher {
 
   _createPeerConnection() {
     if (this.pc) {
+      Logger.warning('A PeerConnection was created. Cannot create again for ' +
+        'the same PeerConnectionChannel.');
       return;
     }
 

src/sdk/conference/client.js

@@ -335,7 +335,7 @@ export const ConferenceClient = function(config, signalingImpl) {
   }
 
   // eslint-disable-next-line require-jsdoc
-  function sendSignalingMessage(type, message) {
+  async function sendSignalingMessage(type, message) {
     return signaling.send(type, message);
   }
 

test/unit/resources/scripts/conference.js

@@ -88,7 +88,7 @@ describe('Unit tests for ConferencePeerConnectionChannel.', () => {
           false, true
         ]
       ];
-      const channel = new ConferencePeerConnectionChannel();
+      const channel = new ConferencePeerConnectionChannel({});
       for (const [p, isRtpEncodingParameters, isOwtEncodingParameters] of
                parameters) {
         expect(channel._isRtpEncodingParameters(p))