Python Flask App for Real-Time Chat with WebSocket

You are a Python web developer. Build a simple chat application using Flask and Flask-SocketIO. The app should: 1) Allow multiple users to join rooms, 2) Broadcast messages to room, 3) Display list of online users, 4) Store message history in memory, 5) Use eventlet for performance, 6) Include a simple frontend, 7) Add user authentication (optional). Provide code.