YouTube/Twitch live chat backend WebSocket proxy

- YouTube chat polling via liveBroadcasts + liveChat/messages APIs
- Twitch IRC WebSocket client with IRCv3 tag parsing
- ChatManager orchestrator with token refresh, retry logic
- WebSocket endpoint at /chat/ws with JWT auth
- Added chat:read, chat:edit to Twitch OAuth scopes

src/routes/chat/websocket.ts

@@ -0,0 +1,88 @@
+import { FastifyPluginAsync } from 'fastify';
+import { verifyAccessToken } from '../../plugins/auth.js';
+import { ChatManager } from '../../services/chat-manager.service.js';
+
+interface ChatWsMessage {
+  type: 'subscribe' | 'unsubscribe' | 'send_message';
+  planId?: string;
+  destinationId?: string;
+  text?: string;
+}
+
+export function createChatRoutes(chatManager: ChatManager): FastifyPluginAsync {
+  const chatRoutes: FastifyPluginAsync = async (fastify) => {
+    fastify.get('/chat/ws', { websocket: true }, async (socket, request) => {
+      // Authenticate via query param
+      const url = new URL(request.url, `http://${request.headers.host}`);
+      const token = url.searchParams.get('token');
+
+      if (!token) {
+        socket.send(JSON.stringify({ type: 'error', error: 'Missing token' }));
+        socket.close();
+        return;
+      }
+
+      let userId: string;
+      try {
+        userId = await verifyAccessToken(token);
+      } catch {
+        socket.send(JSON.stringify({ type: 'error', error: 'Invalid or expired token' }));
+        socket.close();
+        return;
+      }
+
+      request.log.info({ userId }, 'Chat WebSocket connected');
+
+      socket.on('message', async (data: Buffer) => {
+        try {
+          const raw = data.toString();
+          request.log.info({ userId, raw }, 'Chat WS message received');
+          const msg: ChatWsMessage = JSON.parse(raw);
+
+          switch (msg.type) {
+            case 'subscribe':
+              if (msg.planId) {
+                await chatManager.startChat(msg.planId, userId, socket);
+              }
+              break;
+
+            case 'unsubscribe':
+              if (msg.planId) {
+                await chatManager.stopChat(msg.planId, userId);
+              }
+              break;
+
+            case 'send_message':
+              if (msg.planId && msg.destinationId && msg.text) {
+                await chatManager.handleSendMessage(
+                  msg.planId,
+                  userId,
+                  msg.destinationId,
+                  msg.text,
+                );
+              }
+              break;
+
+            default:
+              socket.send(JSON.stringify({ type: 'error', error: `Unknown message type: ${msg.type}` }));
+          }
+        } catch (err) {
+          request.log.error({ err }, 'Chat WebSocket message handling error');
+          socket.send(JSON.stringify({ type: 'error', error: 'Internal error' }));
+        }
+      });
+
+      socket.on('close', () => {
+        request.log.info({ userId }, 'Chat WebSocket disconnected');
+        chatManager.stopAllForSocket(socket);
+      });
+
+      socket.on('error', (err: Error) => {
+        request.log.error({ err, userId }, 'Chat WebSocket error');
+        chatManager.stopAllForSocket(socket);
+      });
+    });
+  };
+
+  return chatRoutes;
+}