figure out how socketio works

backend/src/app.py

@@ -3,7 +3,7 @@ from typing import Any
 import dotenv
 from flask import Flask, Response, jsonify, request
 from flask_cors import CORS
-from flask_socketio import SocketIO, emit
+from flask_socketio import SocketIO, emit, join_room, leave_room
 
 from .connect import get_connection
 from .qrcode_gen import generate_qr
@@ -17,9 +17,10 @@ dotenv.load_dotenv()
 
 app = Flask(__name__)
 app.config["SECRET_KEY"] = "your_secret_key"
-socketio = SocketIO(app)
+socketio = SocketIO(app, cors_allowed_origins="*", path="/ws")
 CORS(app)
 
+
 db_conn = get_connection()
 state = State(app, socketio, db_conn.cursor())
 init_db(state.db)
@@ -54,6 +55,30 @@ def ws_broadcast(event: str, *, room_id: int | None = None, data: Any) -> None:
     emit(event, final, broadcast=True, namespace="/")
 
 
+@socketio.on("connect")
+def handle_connection():
+    print("somebody connected to socket.io", flush=True)
+
+
+@socketio.on("disconnect")
+def handle_disconnection():
+    print("somebody disconnected from socket.io", flush=True)
+
+
+@socketio.on("join_room")
+def on_join(data):
+    room = data["id"]
+    join_room(room)
+    print(f"somebody joined {room=}", flush=True)
+
+
+@socketio.on("leave_room")
+def on_leave(data):
+    room = data["id"]
+    leave_room(room)
+    print(f"somebody left {room=}", flush=True)
+
+
 @app.get("/api/join")
 def join():
     room_id = request.args.get("room")