Multiple improvements in authentication functionality

frontend/lib/backend.dart

@@ -6,26 +6,46 @@ import 'dart:async'; // Import for handling Completers
 class Backend {
   static WebSocket? _socket;
   static String? _url;
-  static String? _username;
   static Map<int, Completer> _pendingActions = {};
   static Map<int, StreamController<Map<String, dynamic>>> _chatControllers = {};
   static int _nextNonce = 0; // Tracking nonce for each action
   static StreamController<Map<String, dynamic>> _packetStreamController = StreamController.broadcast();
+  
+  // Authentication
+  static ({String username, String password})? _credentials;
+  static Completer? _loginCompleter;
+  static Completer? _credentialsCompleter;
 
   static void setup(String url) {
     _url = url;
     connect();
   }
 
-  static void auth(String username, String password) {
+  static Future<void> auth(String username, String password) {
     _socket!.send(json.encode({'username': username, 'password': password}));
-    _username = username;
+    _credentials = (username: username, password: password);
+    if (_credentialsCompleter != null) {
+      _credentialsCompleter!.complete(_credentials);
+      _credentialsCompleter = null;
+    }
+    _loginCompleter = Completer();
+    return _loginCompleter!.future;
   }
 
   static void connect() {
     _socket = WebSocket(_url!);
     _socket!.onOpen.listen((event) {
       print('Connected to the WebSocket server');
+      print('Logging in...');
+      if (_credentials != null) {
+        _socket!.send(json.encode({'username': _credentials!.username, 'password': _credentials!.password}));
+      } else {
+        _credentialsCompleter = Completer();
+        _credentialsCompleter!.future.then((credentials) {
+          _socket!.send(json.encode({'username': credentials.username, 'password': credentials.password}));
+        });
+      }
+      _loginCompleter?.complete();
     });
     _socket!.onError.listen((event) {
       print('Error: $event');
@@ -40,6 +60,11 @@ class Backend {
     });
   }
 
+  static void disconnect() {
+    _socket?.close();
+    _loginCompleter = null;
+  }
+
   static void _reconnect() {
     Future.delayed(Duration(seconds: 5), () {
       connect();