client & server: added error handling for lobby connection issues

server_tcp.py

@@ -6,6 +6,8 @@ import ssl
 import asyncio
 from websockets.asyncio.server import serve
 
+MAX_LOBBY_CLIENT_COUNT = 6
+
 # Generates a 6-character code from the letters A-Z
 def generate_code() -> str:
     result = ""
@@ -42,7 +44,15 @@ class LobbyManager:
         print(f"Created lobby {lobby_id}")
 
     # Joins a client to an existing lobby
-    async def join_lobby(self, lobby_id, client_id, client_name, websocket) -> None:
+    async def join_lobby(self, lobby_id, client_id, client_name, websocket) -> str:
+        if not self.lobby_id_exists(lobby_id):
+            # Cannot join; lobby does not exist
+            return "lobby_not_found"  
+
+        if self.get_lobby_player_count(lobby_id) >= MAX_LOBBY_CLIENT_COUNT:
+            # Lobby full! Cannot join
+            return "lobby_full"  
+        
         # Add client to lobby
         self.active_lobbies[lobby_id].connected_clients[client_id] = Client(
             client_id,
@@ -61,6 +71,8 @@ class LobbyManager:
                 "connected_client_names": self.get_lobby_client_names(lobby_id),
             })
         )
+
+        return "ok"
     
     # Removes a client from a lobby
     async def leave_lobby(self, lobby_id, client_id) -> None:
@@ -201,7 +213,9 @@ async def process_input(message: str, websocket) -> None:
             new_client_id,
         )
 
-        # Join requesting client to new lobby
+        # Join requesting client to new lobby.
+        # No error handling here, since lobby was just created, so it
+        # must exist and be empty
         await lobby_manager.join_lobby(
             new_lobby_id,
             new_client_id,
@@ -226,28 +240,51 @@ async def process_input(message: str, websocket) -> None:
     # Join client to existing lobby
     elif data_object["response"] == "join_lobby":
         lobby_id = data_object["lobby_id"]
-        new_client_id = lobby_manager.get_unique_client_id(lobby_id)
+        client_id = lobby_manager.get_unique_client_id(lobby_id)
+        client_name = data_object["client_name"]
 
         # Join client to lobby
-        await lobby_manager.join_lobby(
+        response = await lobby_manager.join_lobby(
             lobby_id,
-            new_client_id,
-            data_object["client_name"],
+            client_id,
+            client_name,
             websocket,
         )
 
-        # Send success confirmation
-        await lobby_manager.send_message(
-            lobby_id,
-            new_client_id,
-            json.dumps({
-                "response": "join_lobby",
-                "status": "ok",
-                "client_id": new_client_id,
-            }),
-        )
+        match response:
+            case "lobby_not_found":
+                await websocket.send(
+                    json.dumps({
+                        "response": "join_lobby_response",
+                        "status": "lobby_not_found",
+                    })
+                )
+                
+                print(f"Client {client_name} could not connect; lobby {lobby_id} does not exist")
+            
+            case "lobby_full":
+                await websocket.send(
+                    json.dumps({
+                        "response": "join_lobby_response",
+                        "status": "lobby_full",
+                    })
+                )
 
-        print(f"Client {new_client_id} joined lobby {lobby_id}")
+                print(f"Client {client_name} could not connect; lobby {lobby_id} is full")
+            
+            case "ok":
+                # Send success confirmation
+                await lobby_manager.send_message(
+                    lobby_id,
+                    client_id,
+                    json.dumps({
+                        "response": "join_lobby_response",
+                        "status": "ok",
+                        "client_id": client_id,
+                    }),
+                )
+
+                print(f"Client {client_id} joined lobby {lobby_id}")
 
     # Disconnect client from lobby
     elif data_object["response"] == "leave_lobby":