use data channel to communicate video enabling status

Session/Calls/CallVC.swift

@@ -189,7 +189,7 @@ final class CallVC : UIViewController, WebRTCSessionDelegate {
             Storage.write { transaction in
                 self.webRTCSession.sendPreOffer(to: self.sessionID, using: transaction).done {
                     self.webRTCSession.sendOffer(to: self.sessionID, using: transaction).retainUntilComplete()
-                }
+                }.retainUntilComplete()
             }
             answerButton.isHidden = true
         }
@@ -274,7 +274,7 @@ final class CallVC : UIViewController, WebRTCSessionDelegate {
     }
     
     // MARK: Delegate
-    func webRTCDidConnected() {
+    func webRTCIsConnected() {
         DispatchQueue.main.async {
             self.callInfoLabel.text = "Connected"
             UIView.animate(withDuration: 0.5, delay: 1, options: [], animations: {
@@ -286,6 +286,10 @@ final class CallVC : UIViewController, WebRTCSessionDelegate {
         }
     }
     
+    func isRemoteVideoDidChange(isEnabled: Bool) {
+        remoteVideoView.isHidden = !isEnabled
+    }
+    
     // MARK: Interaction
     func handleAnswerMessage(_ message: CallMessage) {
         callInfoLabel.text = "Connecting..."

SessionMessagingKit/Calls/WebRTCSession+DataChannel.swift

@@ -14,7 +14,7 @@ extension WebRTCSession: RTCDataChannelDelegate {
     }
     
     public func sendJSON(_ json: JSON) {
-        if let dataChannel = self.dataChannel, let jsonAsData = try? JSONSerialization.data(withJSONObject: json, options: [ .fragmentsAllowed ]) {
+        if let dataChannel = dataChannel, let jsonAsData = try? JSONSerialization.data(withJSONObject: json, options: [ .fragmentsAllowed ]) {
             let dataBuffer = RTCDataBuffer(data: jsonAsData, isBinary: false)
             dataChannel.sendData(dataBuffer)
         }
@@ -27,8 +27,10 @@ extension WebRTCSession: RTCDataChannelDelegate {
     
     public func dataChannel(_ dataChannel: RTCDataChannel, didReceiveMessageWith buffer: RTCDataBuffer) {
         print("[Calls] Data channel did receive data: \(buffer)")
-        if let json = try? JSONSerialization.jsonObject(with: buffer.data, options: [ .fragmentsAllowed ]) {
+        if let json = try? JSONSerialization.jsonObject(with: buffer.data, options: [ .fragmentsAllowed ]) as? JSON {
-            
+            if let isRemoteVideoEnabled = json["video"] as? Bool {
+                delegate?.isRemoteVideoDidChange(isEnabled: isRemoteVideoEnabled)
+            }
         }
     }
 }

SessionMessagingKit/Calls/WebRTCSession.swift

@@ -4,7 +4,8 @@ import WebRTC
 public protocol WebRTCSessionDelegate : AnyObject {
     var videoCapturer: RTCVideoCapturer { get }
     
-    func webRTCDidConnected()
+    func webRTCIsConnected()
+    func isRemoteVideoDidChange(isEnabled: Bool)
 }
 
 /// See https://webrtc.org/getting-started/overview for more information.
@@ -244,7 +245,7 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
     public func peerConnection(_ peerConnection: RTCPeerConnection, didChange state: RTCIceConnectionState) {
         print("[Calls] ICE connection state changed to: \(state).")
         if state == .connected {
-            delegate?.webRTCDidConnected()
+            delegate?.webRTCIsConnected()
         }
     }
     
@@ -290,9 +291,11 @@ extension WebRTCSession {
     
     public func turnOffVideo() {
         localVideoTrack.isEnabled = false
+        sendJSON(["video": false])
     }
     
     public func turnOnVideo() { 
         localVideoTrack.isEnabled = true
+        sendJSON(["video": true])
     }
 }