feat(conference) Implement audio/video mute disable when sender limit is reached.

Jicofo sends a presence when the audio/video sender limit is reaced in the conference. The client can then proceed to disable the audio and video mute buttons when this occurs.

JitsiConference.js

@@ -285,6 +285,20 @@ export default function JitsiConference(options) {
 
         this._e2eEncryption = new E2EEncryption(this);
     }
+
+    /**
+     * Flag set to <tt>true</tt> when Jicofo sends a presence message indicating that the max audio sender limit has
+     * been reached for the call. Once this is set, unmuting audio will be disabled from the client until it gets reset
+     * again by Jicofo.
+     */
+    this._audioSenderLimitReached = undefined;
+
+    /**
+     * Flag set to <tt>true</tt> when Jicofo sends a presence message indicating that the max video sender limit has
+     * been reached for the call. Once this is set, unmuting video will be disabled from the client until it gets reset
+     * again by Jicofo.
+     */
+    this._videoSenderLimitReached = undefined;
 }
 
 // FIXME convert JitsiConference to ES6 - ASAP !
@@ -3151,9 +3165,22 @@ JitsiConference.prototype._updateProperties = function(properties = {}) {
 
     this.properties = properties;
     if (changed) {
-        this.eventEmitter.emit(
-            JitsiConferenceEvents.PROPERTIES_CHANGED,
-            this.properties);
+        this.eventEmitter.emit(JitsiConferenceEvents.PROPERTIES_CHANGED, this.properties);
+
+        const audioLimitReached = this.properties['audio-limit-reached'] === 'true';
+        const videoLimitReached = this.properties['video-limit-reached'] === 'true';
+
+        if (this._audioSenderLimitReached !== audioLimitReached) {
+            this._audioSenderLimitReached = audioLimitReached;
+            this.eventEmitter.emit(JitsiConferenceEvents.AUDIO_UNMUTE_PERMISSIONS_CHANGED, audioLimitReached);
+            logger.info(`Audio unmute permissions set by Jicofo to ${audioLimitReached}`);
+        }
+
+        if (this._videoSenderLimitReached !== videoLimitReached) {
+            this._videoSenderLimitReached = videoLimitReached;
+            this.eventEmitter.emit(JitsiConferenceEvents.VIDEO_UNMUTE_PERMISSIONS_CHANGED, videoLimitReached);
+            logger.info(`Video unmute permissions set by Jicofo to ${videoLimitReached}`);
+        }
 
         // Some of the properties need to be added to analytics events.
         const analyticsKeys = [

JitsiConferenceEvents.js

@@ -8,6 +8,12 @@
  */
 export const AUDIO_INPUT_STATE_CHANGE = 'conference.audio_input_state_changed';
 
+/**
+ * Event indicates that the permission for unmuting audio has changed based on the number of audio senders in the call
+ * and the audio sender limit configured in Jicofo.
+ */
+export const AUDIO_UNMUTE_PERMISSIONS_CHANGED = 'conference.audio_unmute_permissions_changed';
+
 /**
  * Indicates that authentication status changed.
  */
@@ -362,6 +368,12 @@ export const USER_ROLE_CHANGED = 'conference.roleChanged';
  */
 export const USER_STATUS_CHANGED = 'conference.statusChanged';
 
+/**
+ * Event indicates that the permission for unmuting video has changed based on the number of video senders in the call
+ * and the video sender limit configured in Jicofo.
+ */
+export const VIDEO_UNMUTE_PERMISSIONS_CHANGED = 'conference.video_unmute_permissions_changed';
+
 /**
  * Event indicates that the bot participant type changed.
  */

modules/xmpp/ChatRoom.js

@@ -741,11 +741,14 @@ export default class ChatRoom extends Listenable {
                         }
                     }
 
-                    this.eventEmitter.emit(
-                        XMPPEvents.CONFERENCE_PROPERTIES_CHANGED, properties);
+                    this.eventEmitter.emit(XMPPEvents.CONFERENCE_PROPERTIES_CHANGED, properties);
 
-                    this.restartByTerminateSupported = properties['support-terminate-restart'] === 'true';
-                    logger.info(`Jicofo supports restart by terminate: ${this.supportsRestartByTerminate()}`);
+                    // Log if Jicofo supports restart by terminate only once. This conference property does not change
+                    // during the call.
+                    if (typeof this.restartByTerminateSupported === 'undefined') {
+                        this.restartByTerminateSupported = properties['support-terminate-restart'] === 'true';
+                        logger.info(`Jicofo supports restart by terminate: ${this.supportsRestartByTerminate()}`);
+                    }
                 }
                 break;
             case 'transcription-status': {