feature: support restarting bidi streaming

src/app/components/chat-panel/chat-panel.component.scss

@@ -382,7 +382,8 @@ button.audio-rec-btn,
 button.video-rec-btn {
   background-color: var(--chat-card-background-color);
   &.recording {
-    background-color: var(--chat-panel-eval-fail-color);
+    background-color: var(--chat-panel-eval-fail-color) !important;
+    color: white !important;
   }
 }
 

src/app/components/chat/chat.component.spec.ts

@@ -806,15 +806,92 @@ describe('ChatComponent', () => {
 
     describe('when bidi streaming is restarted', () => {
       beforeEach(() => {
-        component.sessionHasUsedBidi.add(component.sessionId);
+        component.startAudioRecording();
+        component.stopAudioRecording();
         component.startAudioRecording();
       });
-      it('should show snackbar', () => {
-        expect(mockSnackBar.open)
-            .toHaveBeenCalledWith(
-                'Restarting bidirectional streaming is not currently supported. Please refresh the page or start a new session.',
-                OK_BUTTON_TEXT,
-            );
+      it('should allow restart without error', () => {
+        expect(component.isAudioRecording).toBe(true);
+        expect(mockStreamChatService.startAudioChat).toHaveBeenCalledTimes(2);
+      });
+    });
+
+    describe('when audio recording is stopped and restarted', () => {
+      beforeEach(() => {
+        component.startAudioRecording();
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(true);
+        component.stopAudioRecording();
+      });
+      it('should remove session from sessionHasUsedBidi set', () => {
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(false);
+      });
+
+      it('should allow restarting audio recording', () => {
+        component.startAudioRecording();
+        expect(mockSnackBar.open).not.toHaveBeenCalled();
+        expect(component.isAudioRecording).toBe(true);
+      });
+    });
+
+    describe('when video recording is stopped and restarted', () => {
+      beforeEach(() => {
+        component.startVideoRecording();
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(true);
+        component.stopVideoRecording();
+      });
+
+      it('should remove session from sessionHasUsedBidi set', () => {
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(false);
+      });
+
+      it('should allow restarting video recording', () => {
+        component.startVideoRecording();
+        expect(mockSnackBar.open).not.toHaveBeenCalled();
+        expect(component.isVideoRecording).toBe(true);
+      });
+    });
+
+    describe('when trying to start concurrent bidi streams', () => {
+      it('should prevent starting audio while already recording', () => {
+        component.startAudioRecording();
+        expect(component.isAudioRecording).toBe(true);
+
+        component.startAudioRecording();
+
+        expect(mockSnackBar.open).toHaveBeenCalledWith(
+          'Another streaming request is already in progress. Please stop it before starting a new one.',
+          'OK'
+        );
+        expect(mockStreamChatService.startAudioChat).toHaveBeenCalledTimes(1);
+      });
+
+      it('should prevent starting video while already recording', () => {
+        component.startVideoRecording();
+        expect(component.isVideoRecording).toBe(true);
+
+        component.startVideoRecording();
+
+        expect(mockSnackBar.open).toHaveBeenCalledWith(
+          'Another streaming request is already in progress. Please stop it before starting a new one.',
+          'OK'
+        );
+        expect(mockStreamChatService.startVideoChat).toHaveBeenCalledTimes(1);
+      });
+    });
+
+    describe('when stopping video recording without videoContainer', () => {
+      it('should still cleanup sessionHasUsedBidi', () => {
+        component.startVideoRecording();
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(true);
+
+        spyOn(component, 'chatPanel').and.returnValue({
+          videoContainer: undefined
+        } as any);
+
+        component.stopVideoRecording();
+
+        expect(component.sessionHasUsedBidi.has(component.sessionId)).toBe(false);
+        expect(component.isVideoRecording).toBe(false);
       });
     });
   });

src/app/components/chat/chat.component.ts

@@ -113,7 +113,7 @@ class CustomPaginatorIntl extends MatPaginatorIntl {
 }
 
 const BIDI_STREAMING_RESTART_WARNING =
-    'Restarting bidirectional streaming is not currently supported. Please refresh the page or start a new session.';
+    'Another streaming request is already in progress. Please stop it before starting a new one.';
 
 @Component({
   selector: 'app-chat',
@@ -213,7 +213,6 @@ export class ChatComponent implements OnInit, AfterViewInit, OnDestroy {
   private readonly isModelThinkingSubject = new BehaviorSubject(false);
   protected readonly canEditSession = signal(true);
 
-  // TODO: Remove this once backend supports restarting bidi streaming.
   sessionHasUsedBidi = new Set<string>();
 
   eventData = new Map<string, any>();
@@ -1018,11 +1017,14 @@ export class ChatComponent implements OnInit, AfterViewInit, OnDestroy {
              {role: 'bot', text: 'Speaking...'},
     ]);
     this.sessionHasUsedBidi.add(this.sessionId);
+    this.changeDetectorRef.detectChanges();
   }
 
   stopAudioRecording() {
     this.streamChatService.stopAudioChat();
     this.isAudioRecording = false;
+    this.sessionHasUsedBidi.delete(this.sessionId);
+    this.changeDetectorRef.detectChanges();
   }
 
   toggleVideoRecording() {
@@ -1049,15 +1051,17 @@ export class ChatComponent implements OnInit, AfterViewInit, OnDestroy {
     this.messages.update(
         messages => [...messages, {role: 'user', text: 'Speaking...'}]);
     this.sessionHasUsedBidi.add(this.sessionId);
+    this.changeDetectorRef.detectChanges();
   }
 
   stopVideoRecording() {
     const videoContainer = this.chatPanel()?.videoContainer;
-    if (!videoContainer) {
-      return;
+    if (videoContainer) {
+      this.streamChatService.stopVideoChat(videoContainer);
     }
-    this.streamChatService.stopVideoChat(videoContainer);
     this.isVideoRecording = false;
+    this.sessionHasUsedBidi.delete(this.sessionId);
+    this.changeDetectorRef.detectChanges();
   }
 
   private getAsyncFunctionsFromParts(

src/app/core/services/stream-chat.service.spec.ts

@@ -263,4 +263,64 @@ describe('StreamChatService', () => {
          expect(mockWebSocketService.sendMessage).toHaveBeenCalledTimes(2);
        }));
   });
+
+  describe('restart audio chat', () => {
+    it('should allow restarting audio chat after stopping', async () => {
+         mockAudioRecordingService.getCombinedAudioBuffer.and.returnValue(
+             Uint8Array.of());
+
+         await service.startAudioChat({
+           appName: 'fake-app-name',
+           userId: 'fake-user-id',
+           sessionId: 'fake-session-id'
+         });
+         expect(mockWebSocketService.connect).toHaveBeenCalledTimes(1);
+         expect(mockAudioRecordingService.startRecording).toHaveBeenCalledTimes(1);
+
+         service.stopAudioChat();
+         expect(mockAudioRecordingService.stopRecording).toHaveBeenCalledTimes(1);
+         expect(mockWebSocketService.closeConnection).toHaveBeenCalledTimes(1);
+
+         await service.startAudioChat({
+           appName: 'fake-app-name',
+           userId: 'fake-user-id',
+           sessionId: 'fake-session-id'
+         });
+         expect(mockWebSocketService.connect).toHaveBeenCalledTimes(2);
+         expect(mockAudioRecordingService.startRecording).toHaveBeenCalledTimes(2);
+       });
+  });
+
+  describe('restart video chat', () => {
+    it('should allow restarting video chat after stopping', async () => {
+         mockAudioRecordingService.getCombinedAudioBuffer.and.returnValue(
+             Uint8Array.of());
+         mockVideoService.getCapturedFrame.and.resolveTo(Uint8Array.of());
+
+         await service.startVideoChat({
+           appName: 'fake-app-name',
+           userId: 'fake-user-id',
+           sessionId: 'fake-session-id',
+           videoContainer
+         });
+         expect(mockWebSocketService.connect).toHaveBeenCalledTimes(1);
+         expect(mockAudioRecordingService.startRecording).toHaveBeenCalledTimes(1);
+         expect(mockVideoService.startRecording).toHaveBeenCalledTimes(1);
+
+         service.stopVideoChat(videoContainer);
+         expect(mockAudioRecordingService.stopRecording).toHaveBeenCalledTimes(1);
+         expect(mockVideoService.stopRecording).toHaveBeenCalledTimes(1);
+         expect(mockWebSocketService.closeConnection).toHaveBeenCalledTimes(1);
+
+         await service.startVideoChat({
+           appName: 'fake-app-name',
+           userId: 'fake-user-id',
+           sessionId: 'fake-session-id',
+           videoContainer
+         });
+         expect(mockWebSocketService.connect).toHaveBeenCalledTimes(2);
+         expect(mockAudioRecordingService.startRecording).toHaveBeenCalledTimes(2);
+         expect(mockVideoService.startRecording).toHaveBeenCalledTimes(2);
+       });
+  });
 });

src/app/core/services/websocket.service.spec.ts

@@ -55,4 +55,33 @@ describe('WebSocketService', () => {
       expect(service.urlSafeBase64ToBase64('abcd')).toEqual('abcd');
     });
   });
+
+  describe('connection restart', () => {
+    it('should reset audio buffer when reconnecting', () => {
+      service.connect('ws://test1');
+
+      (service as any).audioBuffer = [new Uint8Array([1, 2, 3])];
+
+      service.connect('ws://test2');
+      expect((service as any).audioBuffer).toEqual([]);
+    });
+
+    it('should close previous connection when reconnecting', () => {
+      service.connect('ws://test1');
+      const firstSocket = (service as any).socket$;
+      spyOn(firstSocket, 'complete');
+
+      service.connect('ws://test2');
+      expect(firstSocket.complete).toHaveBeenCalled();
+    });
+
+    it('should clear audio interval when closing connection', () => {
+      service.connect('ws://test');
+      const intervalId = (service as any).audioIntervalId;
+      expect(intervalId).not.toBeNull();
+
+      service.closeConnection();
+      expect((service as any).audioIntervalId).toBeNull();
+    });
+  });
 });

src/app/core/services/websocket.service.ts

@@ -38,6 +38,12 @@ export class WebSocketService implements WebSocketServiceInterface {
   private closeReasonSubject = new Subject<string>();
 
   connect(serverUrl: string) {
+    // Clean up previous connection if exists
+    this.closeConnection();
+
+    // Reset audio buffer for new connection
+    this.audioBuffer = [];
+
     this.socket$ = new WebSocketSubject({
       url: serverUrl,
       serializer: (msg) => JSON.stringify(msg),