Support m.call.reject

Start the migration to v1 VoIP by supporting m.call.reject, which
we'll send if the caller says they're v1. Our version stays as v0
for now, until we speak the rest of v1.

Honour the default reaosn in a hangup being user_hangup.

src/@types/event.ts

@@ -45,6 +45,7 @@ export enum EventType {
     CallCandidates = "m.call.candidates",
     CallAnswer = "m.call.answer",
     CallHangup = "m.call.hangup",
+    CallReject = "m.call.reject",
     KeyVerificationRequest = "m.key.verification.request",
     KeyVerificationStart = "m.key.verification.start",
     KeyVerificationCancel = "m.key.verification.cancel",

src/webrtc/call.ts

@@ -164,6 +164,14 @@ export enum CallErrorCode {
     Replaced = 'replaced',
 }
 
+/**
+ * The version field that we set in m.call.* events
+ * Once we are able to speak v1 VoIP sufficiently, this
+ * bumped to 1. While we partially speak v1 VoIP, it remains
+ * as 0.
+ */
+const VOIP_PROTO_VERSION = 0;
+
 /** The fallback ICE server to use for STUN or TURN protocols. */
 const FALLBACK_ICE_SERVER = 'stun:turn.matrix.org';
 
@@ -222,6 +230,7 @@ export class MatrixCall extends EventEmitter {
     // XXX: I don't know why this is called 'config'.
     private config: MediaStreamConstraints;
     private successor: MatrixCall;
+    private opponentVersion: number;
 
     constructor(opts: CallOpts) {
         super();
@@ -439,6 +448,7 @@ export class MatrixCall extends EventEmitter {
 
         this.setState(CallState.Ringing);
         this.direction = CallDirection.Inbound;
+        this.opponentVersion = this.msg.version;
 
         if (event.getLocalAge()) {
             setTimeout(() => {
@@ -457,7 +467,7 @@ export class MatrixCall extends EventEmitter {
     }
 
     /**
-     * Configure this call from a hangup event. Used by MatrixClient.
+     * Configure this call from a hangup or reject event. Used by MatrixClient.
      * @param {MatrixEvent} event The m.call.hangup event
      */
     initWithHangup(event: MatrixEvent) {
@@ -536,7 +546,7 @@ export class MatrixCall extends EventEmitter {
         logger.debug("Ending call " + this.callId);
         this.terminate(CallParty.Local, reason, !suppressEvent);
         const content = {
-            version: 0,
+            version: VOIP_PROTO_VERSION,
             call_id: this.callId,
         };
         // Continue to send no reason for user hangups temporarily, until
@@ -545,6 +555,33 @@ export class MatrixCall extends EventEmitter {
         this.sendEvent('m.call.hangup', content);
     }
 
+    /**
+     * Reject a call
+     * This used to be done by calling hangup, but is a separate method and protocol
+     * event as of MSC2746.
+     */
+    reject() {
+        if (this.state !== CallState.Ringing) {
+            throw Error("Call must be in 'ringing' state to reject!");
+        }
+
+        if (this.opponentVersion < 1) {
+            logger.info(
+                `Opponent version is less than 1 (${this.opponentVersion}): sending hangup instead of reject`,
+            );
+            this.hangup(CallErrorCode.UserHangup, true);
+            return;
+        }
+
+        logger.debug("Rejecting call: " + this.callId);
+        this.terminate(CallParty.Local, CallErrorCode.UserHangup, true);
+        const content = {
+            version: VOIP_PROTO_VERSION,
+            call_id: this.callId,
+        };
+        this.sendEvent('m.call.reject', content);
+    }
+
     /**
      * Set whether the local video preview should be muted or not.
      * @param {boolean} muted True to mute the local video.
@@ -713,7 +750,7 @@ export class MatrixCall extends EventEmitter {
             await this.peerConn.setLocalDescription(myAnswer);
 
             this.answerContent = {
-                version: 0,
+                version: VOIP_PROTO_VERSION,
                 call_id: this.callId,
                 answer: {
                     sdp: this.peerConn.localDescription.sdp,
@@ -800,6 +837,8 @@ export class MatrixCall extends EventEmitter {
             return;
         }
 
+        this.opponentVersion = msg.version;
+
         try {
             this.peerConn.setRemoteDescription(msg.answer);
         } catch (e) {
@@ -829,7 +868,7 @@ export class MatrixCall extends EventEmitter {
         }
 
         const content = {
-            version: 0,
+            version: VOIP_PROTO_VERSION,
             call_id: this.callId,
             // OpenWebRTC appears to add extra stuff (like the DTLS fingerprint)
             // to the description when setting it on the peerconnection.
@@ -1004,7 +1043,17 @@ export class MatrixCall extends EventEmitter {
 
     onHangupReceived = (msg) => {
         logger.debug("Hangup received");
-        this.terminate(CallParty.Remote, msg.reason, true);
+        // default reason is user_hangup
+        this.terminate(CallParty.Remote, msg.reason || CallErrorCode.UserHangup, true);
+    };
+
+    onRejectReceived = (msg) => {
+        logger.debug("Reject received");
+        if (this.state === CallState.InviteSent) {
+            this.terminate(CallParty.Remote, CallErrorCode.UserHangup, true);
+        } else {
+            logger.debug(`Call is in state: ${this.state}: ignoring reject`);
+        }
     };
 
     onAnsweredElsewhere = (msg) => {
@@ -1127,7 +1176,7 @@ export class MatrixCall extends EventEmitter {
         this.candidateSendQueue = [];
         ++this.candidateSendTries;
         const content = {
-            version: 0,
+            version: VOIP_PROTO_VERSION,
             call_id: this.callId,
             candidates: cands,
         };

src/webrtc/callEventHandler.ts

@@ -232,7 +232,7 @@ export class CallEventHandler {
                     call.gotRemoteIceCandidate(cand);
                 }
             }
-        } else if (event.getType() === EventType.CallHangup) {
+        } else if ([EventType.CallHangup, EventType.CallReject].includes(event.getType())) {
             // Note that we also observe our own hangups here so we can see
             // if we've already rejected a call that would otherwise be valid
             if (!call) {
@@ -247,7 +247,11 @@ export class CallEventHandler {
                 }
             } else {
                 if (call.state !== CallState.Ended) {
+                    if (event.getType() === EventType.CallHangup) {
                         call.onHangupReceived(content);
+                    } else {
+                        call.onRejectReceived(content);
+                    }
                     this.calls.delete(content.call_id);
                 }
             }