import { WebSocketServer } from 'ws';
import { PointerMessage } from '@mcp-pointer/shared/types';
import { config } from '../config';
import logger from '../logger';
import { sleep } from '../utils';
// WebSocket constants
const WEBSOCKET_RETRY_INTERVAL = 5000; // 5 seconds
type MessageHandler = (type: string, data: any) => void | Promise<void>;
export default class WebSocketService {
private wss: WebSocketServer | null = null;
private isLeader = false;
private port: number;
private messageHandler: MessageHandler | null = null;
constructor(port: string | number = config.websocket.port) {
const intPort = typeof port === 'string' ? parseInt(port, 10) : port;
this.port = intPort;
}
public registerMessageHandler(handler: MessageHandler): void {
this.messageHandler = handler;
}
public async start(): Promise<void> {
return this.campaignForLeadership();
}
private async campaignForLeadership(): Promise<void> {
while (!this.isLeader) {
try {
this.wss = new WebSocketServer({ port: this.port });
this.setupHandlers();
await this.waitForListening();
this.isLeader = true;
logger.info('🎯 This instance is now the LEADER (WebSocket server active)');
} catch (err) {
// Clean up failed attempt
this.stop();
const error = err as NodeJS.ErrnoException;
if (error.code === 'EADDRINUSE') {
logger.info('👥 Running as FOLLOWER (port busy, retrying in 5s...)');
await sleep(WEBSOCKET_RETRY_INTERVAL);
} else {
logger.error('Failed to start WebSocket server:', err);
throw err;
}
}
}
}
private setupHandlers(): void {
if (!this.wss) return;
this.wss.on('connection', this.handleConnection.bind(this));
}
private async waitForListening(): Promise<void> {
return new Promise<void>((resolve, reject) => {
this.wss!.on('listening', resolve);
this.wss!.on('error', reject);
});
}
private handleConnection(ws: any): void {
logger.info('👆 Browser extension connected to WebSocket server');
ws.on('message', this.handleWebSocketMessage.bind(this));
ws.on('close', this.handleWebSocketClose.bind(this));
}
private handleWebSocketMessage(data: any): void {
try {
const message: PointerMessage = JSON.parse(data.toString());
logger.info('📨 Received message from browser:', message.type);
if (this.messageHandler) {
this.messageHandler(message.type, message.data);
}
} catch (error) {
logger.error('Failed to parse message:', error);
}
}
private handleWebSocketClose(): void {
logger.info('👆 Browser extension disconnected from WebSocket server');
}
public isLeaderInstance(): boolean {
return this.isLeader;
}
public stop(): void {
if (this.wss) {
this.wss.close();
this.wss = null;
}
this.isLeader = false;
}
}
