Process toDevice events in order

src/webrtc/call.ts

@@ -272,6 +272,7 @@ export class MatrixCall extends EventEmitter {
     public direction: CallDirection;
     public ourPartyId: string;
     public peerConn?: RTCPeerConnection;
+    public toDeviceSeq = 0;
 
     private client: MatrixClient;
     private forceTURN: boolean;
@@ -1984,6 +1985,8 @@ export class MatrixCall extends EventEmitter {
         });
 
         if (this.opponentDeviceId) {
+            const toDeviceSeq = this.toDeviceSeq++;
+
             this.emit(CallEvent.SendVoipEvent, {
                 type: "toDevice",
                 eventType,
@@ -1994,6 +1997,7 @@ export class MatrixCall extends EventEmitter {
                     device_id: this.client.deviceId,
                     sender_session_id: this.client.getSessionId(),
                     dest_session_id: this.opponentSessionId,
+                    seq: toDeviceSeq,
                 },
             });
 
@@ -2004,6 +2008,7 @@ export class MatrixCall extends EventEmitter {
                         device_id: this.client.deviceId,
                         sender_session_id: this.client.getSessionId(),
                         dest_session_id: this.opponentSessionId,
+                        seq: toDeviceSeq,
                     },
                 },
             });

src/webrtc/callEventHandler.ts

@@ -31,6 +31,8 @@ export class CallEventHandler {
     calls: Map<string, MatrixCall>;
     callEventBuffer: MatrixEvent[];
     candidateEventsByCall: Map<string, Array<MatrixEvent>>;
+    nextSeqByCall: Map<string, number> = new Map();
+    toDeviceEventBuffers: Map<string, Array<MatrixEvent>> = new Map();
 
     private eventBufferPromiseChain?: Promise<void>;
 
@@ -80,7 +82,45 @@ export class CallEventHandler {
     };
 
     private onToDeviceEvent = (event: MatrixEvent): void => {
-        this.callEventBuffer.push(event);
+        const content = event.getContent();
+
+        if (!content.call_id) {
+            this.callEventBuffer.push(event);
+            return;
+        }
+
+        if (!this.nextSeqByCall.has(content.call_id)) {
+            this.nextSeqByCall.set(content.call_id, 0);
+        }
+
+        if (content.seq === undefined) {
+            this.callEventBuffer.push(event);
+            return;
+        }
+
+        const nextSeq = this.nextSeqByCall.get(content.call_id) || 0;
+
+        if (content.seq !== nextSeq) {
+            if (!this.toDeviceEventBuffers.has(content.call_id)) {
+                this.toDeviceEventBuffers.set(content.call_id, []);
+            }
+
+            const buffer = this.toDeviceEventBuffers.get(content.call_id);
+            const index = buffer.findIndex((e) => e.getContent().seq > content.seq);
+            buffer.splice(index, 0, event);
+        } else {
+            const callId = content.call_id;
+            this.callEventBuffer.push(event);
+            this.nextSeqByCall.set(callId, content.seq + 1);
+
+            const buffer = this.toDeviceEventBuffers.get(callId);
+
+            while (buffer.length > 0 && buffer[0].getContent().seq === content.seq + 1) {
+                const nextEvent = buffer.pop();
+                this.callEventBuffer.push(nextEvent);
+                this.nextSeqByCall.set(callId, nextEvent.getContent().seq + 1);
+            }
+        }
     };
 
     private async evaluateEventBuffer(eventBuffer: MatrixEvent[]) {
@@ -122,6 +162,8 @@ export class CallEventHandler {
     }
 
     private async handleCallEvent(event: MatrixEvent) {
+        this.client.emit("received_voip_event", event);
+
         const content = event.getContent();
         const callRoomId = (
             event.getRoomId() ||