feature complete. "sorry for the convenience"

modified:   app.py
	new file:   migrations/versions/1ac5a8e0f577_user_session_table.py

app.py

@@ -25,7 +25,7 @@ from flask import (
     Response,
 )
 
-from flask_socketio import SocketIO, emit, join_room
+from flask_socketio import SocketIO, emit, join_room, leave_room
 
 from flask_sqlalchemy import SQLAlchemy
 from sqlalchemy.exc import InvalidRequestError
@@ -187,6 +187,14 @@ class Room(db.Model):
         return self.active_users.split(",") if self.active_users else []
 
 
+class UserSession(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    session_id = db.Column(db.String(128), unique=True, nullable=False)
+    username = db.Column(db.String(128))
+    room_name = db.Column(db.String(128))
+    room_id = db.Column(db.Integer)
+
+
 class Message(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     username = db.Column(db.String(128), nullable=False)
@@ -442,12 +450,20 @@ def search_messages(keywords):
     return search_results_list
 
 
+# Handle user joining a room
 @socketio.on("join")
 def on_join(data):
     room_name = data["room_name"]
+    username = data["username"]
     room = get_room(room_name)
 
-    room.add_user(data["username"])
+    room.add_user(username)
+
+    # Store session data in the database
+    user_session = UserSession(
+        session_id=request.sid, username=username, room_name=room_name, room_id=room.id
+    )
+    db.session.add(user_session)
 
     # Emit the active users list to the new joiner
     emit("active_users", {"users": room.get_active_users()}, room=request.sid)
@@ -473,9 +489,6 @@ def on_join(data):
     total_token_count = 0
 
     # Send the history of messages only to the newly connected client.
-    # The reason for using `request.sid` here is to target the specific session (or client) that
-    # just connected, so only they receive the backlog of messages, rather than broadcasting
-    # this information to all clients in the room.
     for message in previous_messages:
         if not message.is_base64_image():
             total_token_count += message.token_count
@@ -494,18 +507,17 @@ def on_join(data):
         room.title = gpt_generate_room_title(previous_messages)
         db.session.add(room)
         socketio.emit("update_room_title", {"title": room.title}, room=room.name)
-        # Emit an event to update this rooms title in the sidebar for all users.
+        # Emit an event to update this room's title in the sidebar for all users.
         updated_room_data = {"id": room.id, "name": room.name, "title": room.title}
         socketio.emit("update_room_list", updated_room_data, room=None)
 
-    # commit the active user list and title to database.
+    # commit session & active user list and title to database.
     db.session.commit()
 
     # Broadcast to all clients in the room that a new user has joined.
-    # Here, `room=room` ensures the message is sent to everyone in that specific room.
     emit(
         "chat_message",
-        {"id": None, "content": f"{data['username']} has joined the room."},
+        {"id": None, "content": f"{username} has joined the room."},
         room=room.name,
     )
     emit(
@@ -518,6 +530,24 @@ def on_join(data):
     )
 
 
+# Handle user leaving a room
+@socketio.on("disconnect")
+def on_disconnect():
+    sid = request.sid
+    user_session = UserSession.query.filter_by(session_id=sid).first()
+
+    if user_session:
+        room_name = user_session.room_name
+        username = user_session.username
+        room = Room.query.filter_by(name=room_name).first()
+        room.remove_user(username)
+        leave_room(room_name)
+        emit("active_users", {"users": room.get_active_users()}, room=room_name)
+        # Remove session data from the database
+        db.session.delete(user_session)
+        db.session.commit()
+
+
 @socketio.on("chat_message")
 def handle_message(data):
     room_name = data["room_name"]