Socket.io Server

import { Server, Socket } from "socket.io";
import jwt from "jsonwebtoken";
import type { Server as HTTPServer } from "http";

interface JwtPayloadOptions {
  id: string;
  email: string;
  name: string;
}

export interface AuthenticatedSocket extends Socket {
  user?: JwtPayloadOptions;
}

interface InitSocketOptions {
  /** The HTTP server instance to attach socket.io to */
  server: HTTPServer;
  /**
   * Allowed CORS origins
   * @default "*"
   */
  allowedOrigins?: string | string[];
  /**
   * Allowed HTTP methods for CORS
   * @default ["GET", "POST"]
   */
  allowedMethods?: string[];
  /** Allowed headers for CORS */
  allowedHeaders?: string[];
  /**
   * Whether to validate JWT token on connection handshake
   * @default true
   */
  validateToken?: boolean;
}

export function initializeSocket({
  server,
  allowedOrigins = "*",
  allowedMethods = ["GET", "POST"],
  allowedHeaders,
  validateToken = true,
}: InitSocketOptions): Server {
  const io = new Server(server, {
    cors: {
      origin: allowedOrigins,
      methods: allowedMethods,
      allowedHeaders,
      credentials: true,
    },
  });

  io.use((socket: AuthenticatedSocket, next) => {
    console.log(
      `[${new Date().toISOString()}] Socket connected: ${socket.id}, ` +
        `IP: ${socket.handshake.address}, ` +
        `Transport: ${socket.conn.transport}`
    );

    // If validation is disabled, skip auth check
    if (!validateToken) return next();

    const token = socket.handshake.query.token as string;
    if (!token) return next(new Error("Authentication error"));

    try {
      const secret: jwt.Secret = process.env.JWT_ACCESS_SECRET!;
      const decoded = jwt.verify(token, secret) as JwtPayloadOptions;
      socket.user = decoded;
      next();
    } catch (err) {
      console.error("JWT verification failed:", err);
      next(new Error("Authentication error"));
    }
  });

  return io;
}