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/services/twitch-chat.service.ts

@@ -0,0 +1,172 @@
+import { EventEmitter } from 'events';
+import { WebSocket } from 'ws';
+
+export interface TwitchChatMessage {
+  id: string;
+  authorName: string;
+  text: string;
+  timestamp: number;
+  isModerator: boolean;
+  isBroadcaster: boolean;
+  color: string;
+  badges: string;
+}
+
+export class TwitchChatClient extends EventEmitter {
+  private ws: WebSocket | null = null;
+  private channel: string;
+  private token: string;
+  private nick: string;
+  private connected = false;
+  private pingTimer: ReturnType<typeof setInterval> | null = null;
+
+  constructor(channel: string, token: string, nick: string) {
+    super();
+    this.channel = channel.toLowerCase();
+    this.token = token;
+    this.nick = nick.toLowerCase();
+  }
+
+  connect(): void {
+    if (this.ws) return;
+
+    this.ws = new WebSocket('wss://irc-ws.chat.twitch.tv:443');
+
+    this.ws.on('open', () => {
+      if (!this.ws) return;
+      // Request capabilities
+      this.ws.send('CAP REQ :twitch.tv/tags twitch.tv/commands');
+      // Authenticate
+      this.ws.send(`PASS oauth:${this.token}`);
+      this.ws.send(`NICK ${this.nick}`);
+      // Join channel
+      this.ws.send(`JOIN #${this.channel}`);
+    });
+
+    this.ws.on('message', (data: Buffer) => {
+      const raw = data.toString();
+      const lines = raw.split('\r\n').filter(Boolean);
+      for (const line of lines) {
+        this.handleLine(line);
+      }
+    });
+
+    this.ws.on('close', () => {
+      this.connected = false;
+      this.cleanup();
+      this.emit('disconnected');
+    });
+
+    this.ws.on('error', (err: Error) => {
+      this.emit('error', err);
+    });
+
+    // Keep-alive: send PING every 4 minutes
+    this.pingTimer = setInterval(() => {
+      if (this.ws && this.ws.readyState === WebSocket.OPEN) {
+        this.ws.send('PING :tmi.twitch.tv');
+      }
+    }, 240_000);
+  }
+
+  sendMessage(text: string): void {
+    if (!this.ws || this.ws.readyState !== WebSocket.OPEN) return;
+    this.ws.send(`PRIVMSG #${this.channel} :${text}`);
+  }
+
+  disconnect(): void {
+    this.cleanup();
+    if (this.ws) {
+      this.ws.close();
+      this.ws = null;
+    }
+  }
+
+  private cleanup(): void {
+    if (this.pingTimer) {
+      clearInterval(this.pingTimer);
+      this.pingTimer = null;
+    }
+  }
+
+  private handleLine(line: string): void {
+    // Handle PING
+    if (line.startsWith('PING')) {
+      this.ws?.send('PONG :tmi.twitch.tv');
+      return;
+    }
+
+    // Handle successful join / connection
+    if (line.includes('366') || line.includes(':End of /NAMES list')) {
+      if (!this.connected) {
+        this.connected = true;
+        this.emit('connected');
+      }
+      return;
+    }
+
+    // Handle auth failure
+    if (line.includes('NOTICE') && line.includes('Login authentication failed')) {
+      this.emit('error', new Error('missing_scopes'));
+      this.disconnect();
+      return;
+    }
+
+    // Parse PRIVMSG with IRCv3 tags
+    if (line.includes('PRIVMSG')) {
+      const msg = this.parsePrivmsg(line);
+      if (msg) {
+        this.emit('message', msg);
+      }
+    }
+  }
+
+  private parsePrivmsg(line: string): TwitchChatMessage | null {
+    // Format: @tags :user!user@user.tmi.twitch.tv PRIVMSG #channel :message
+    let tags: Record<string, string> = {};
+
+    let rest = line;
+    if (rest.startsWith('@')) {
+      const spaceIdx = rest.indexOf(' ');
+      if (spaceIdx === -1) return null;
+      const tagStr = rest.substring(1, spaceIdx);
+      rest = rest.substring(spaceIdx + 1);
+
+      for (const part of tagStr.split(';')) {
+        const eq = part.indexOf('=');
+        if (eq !== -1) {
+          tags[part.substring(0, eq)] = part.substring(eq + 1);
+        }
+      }
+    }
+
+    // Find message text after "PRIVMSG #channel :"
+    const privmsgIdx = rest.indexOf('PRIVMSG');
+    if (privmsgIdx === -1) return null;
+    const afterPrivmsg = rest.substring(privmsgIdx);
+    const colonIdx = afterPrivmsg.indexOf(' :');
+    if (colonIdx === -1) return null;
+    const text = afterPrivmsg.substring(colonIdx + 2);
+
+    const displayName = tags['display-name'] || this.extractNick(rest);
+    const timestamp = tags['tmi-sent-ts'] ? parseInt(tags['tmi-sent-ts'], 10) : Date.now();
+    const badges = tags['badges'] || '';
+
+    return {
+      id: tags['id'] || `twitch-${Date.now()}-${Math.random().toString(36).substring(2, 8)}`,
+      authorName: displayName,
+      text,
+      timestamp,
+      isModerator: badges.includes('moderator') || tags['mod'] === '1',
+      isBroadcaster: badges.includes('broadcaster'),
+      color: tags['color'] || '',
+      badges,
+    };
+  }
+
+  private extractNick(line: string): string {
+    // :nick!nick@nick.tmi.twitch.tv PRIVMSG ...
+    const match = line.match(/^:(\w+)!/);
+    return match ? match[1] : 'unknown';
+  }
+}