Feat: add offline mode to prevent errors when trying to send requests to not connected server

src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/network/ClientService.java

@@ -26,6 +26,7 @@ public class ClientService {
     private final Socket socket;
 
     private final ExecutorService executor;
+    private final boolean offlineMode;
 
     public static ArrayList<String> response;
     private final AtomicInteger idGenerator;
@@ -42,6 +43,7 @@ public class ClientService {
 
         this.idGenerator = new AtomicInteger(0);
 
+        this.offlineMode = false;
         try {
             socket = new Socket(ip, port);
             clienttcptransport = new TcpTransport(socket);
@@ -52,6 +54,27 @@ public class ClientService {
         executor = Executors.newSingleThreadExecutor();
     }
 
+    /**
+     * Constructs a ClientService in offline mode. No network connection will be
+     * attempted and calls to processCommand will throw a RuntimeException.
+     *
+     * @param offline true to create an offline (no-network) client service
+     */
+    public ClientService(boolean offline) {
+        this.idGenerator = new AtomicInteger(0);
+        this.offlineMode = offline;
+        this.socket = null;
+        this.clienttcptransport = null;
+        this.executor = Executors.newSingleThreadExecutor();
+    }
+
+    /**
+     * Returns true if this ClientService is running in offline mode (no network).
+     */
+    public boolean isOffline() {
+        return offlineMode;
+    }
+
     /**
      * Sends a command to the server and waits for the response. The command is
      * sent using the TcpTransport, and the response is read in a loop until a
@@ -62,6 +85,9 @@ public class ClientService {
      * @return The response from the server as a string.
      */
     protected String processCommand(String message) {
+        if (offlineMode) {
+            throw new RuntimeException("ClientService is offline: cannot process command");
+        }
         AtomicReference<String> response = new AtomicReference<>();
         sendRequest(() -> {
             try {
@@ -135,8 +161,12 @@ public class ClientService {
     public void closeSocket() {
         try {
             executor.shutdown();
+            if (clienttcptransport != null) {
                 clienttcptransport.close();
+            }
+            if (socket != null) {
                 socket.close();
+            }
         } catch (IOException j) {
             System.out.println(j);
         }

src/main/java/ch/unibas/dmi/dbis/cs108/casono/client/ui/lobbyui/CasinomainuiController.java

@@ -3,6 +3,9 @@ package ch.unibas.dmi.dbis.cs108.casono.client.ui.lobbyui;
 import javafx.application.Platform;
 import javafx.fxml.FXML;
 import javafx.scene.control.Button;
+import javafx.scene.control.TextField;
+import javafx.scene.control.Alert;
+import javafx.scene.control.Alert.AlertType;
 import javafx.scene.control.Label;
 import javafx.scene.image.Image;
 import javafx.scene.image.ImageView;
@@ -12,6 +15,7 @@ import javafx.scene.shape.Rectangle;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import ch.unibas.dmi.dbis.cs108.casono.client.network.ClientService;
+import ch.unibas.dmi.dbis.cs108.casono.client.network.LobbyClient;
 
 /**
  * Controller for the Casono main UI lobby. Handles UI initialization and user
@@ -20,17 +24,29 @@ import ch.unibas.dmi.dbis.cs108.casono.client.network.ClientService;
 public class CasinomainuiController {
     private static final Logger LOGGER = LogManager.getLogger(CasinomainuiController.class);
 
-    @FXML private AnchorPane rootPane;
+    @FXML
-    @FXML private Label titleLabel;
+    private AnchorPane rootPane;
-    @FXML private Label subtitleLabel;
+    @FXML
-    @FXML private ImageView logoView;
+    private Label titleLabel;
-    @FXML private Rectangle greenBox;
+    @FXML
-    @FXML private Button exitbutton;
+    private Label subtitleLabel;
-    @FXML private VBox casinoTable;
+    @FXML
+    private ImageView logoView;
+    @FXML
+    private Rectangle greenBox;
+    @FXML
+    private Button exitbutton;
+    @FXML
+    private VBox casinoTable;
+    @FXML
+    private TextField usernameField;
+    @FXML
+    private Button loginButton;
 
     private LobbyButtonTranslationManager translationManager;
     private LobbyButtonGridManager gridManager;
     private int nextButtonId = 1;
+    private LobbyClient lobbyClient;
 
     /** Default constructor for dependency injection by FXMLLoader. */
     public CasinomainuiController() {
@@ -47,8 +63,60 @@ public class CasinomainuiController {
         translationManager = LobbyButtonTranslationManager.getInstance();
         String host = System.getProperty("casono.server.host");
         int port = Integer.parseInt(System.getProperty("casono.server.port"));
-        ClientService clientService = new ClientService(host, port);
+        ClientService clientService;
+        try {
+            clientService = new ClientService(host, port);
+        } catch (RuntimeException e) {
+            LOGGER.warn("Could not connect to server {}:{} — starting in offline mode: {}", host, port, e.getMessage());
+            clientService = new ClientService(true); // offline mode
+        }
         gridManager = new LobbyButtonGridManager(new javafx.scene.layout.GridPane(), translationManager, clientService);
+        // LobbyClient will use the provided ClientService; in offline mode calls will
+        // fail with RuntimeException
+        lobbyClient = new LobbyClient(clientService);
+        casinoTable.getChildren().clear();
+        casinoTable.getChildren().add(gridManager.getGridPane());
+        gridManager.renderLobbyButtons();
+    }
+
+    /**
+     * Handles the login button action. Validates input and calls
+     * LobbyClient.login().
+     */
+    @FXML
+    public void handleLoginButton() {
+        String username = usernameField.getText();
+        if (username == null || username.isBlank()) {
+            showAlert("Please enter a username.");
+            return;
+        }
+        // Only allow alphanumeric, _ and -
+        if (!username.matches("[a-zA-Z0-9_-]+")) {
+            showAlert("Only letters, numbers, '_' and '-' are allowed!");
+            return;
+        }
+        if (lobbyClient.getClientService().isOffline()) {
+            showAlert("Offline mode: cannot send login to server.");
+            return;
+        }
+        try {
+            lobbyClient.login(username);
+            showAlert("Login sent: " + username);
+        } catch (RuntimeException e) {
+            LOGGER.error("Login failed: {}", e.getMessage());
+            showAlert("Login failed: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Shows an alert dialog with the given message.
+     */
+    private void showAlert(String message) {
+        Alert alert = new Alert(AlertType.INFORMATION);
+        alert.setTitle("Info");
+        alert.setHeaderText(null);
+        alert.setContentText(message);
+        alert.showAndWait();
         casinoTable.getChildren().clear();
         casinoTable.getChildren().add(gridManager.getGridPane());
         gridManager.renderLobbyButtons();
@@ -69,6 +137,14 @@ public class CasinomainuiController {
         }
         int buttonId = nextButtonId++;
         try {
+            String username = usernameField != null ? usernameField.getText() : "<unknown>";
+            LOGGER.info("Creating lobby for user: {}", username);
+            // avoid attempting to create a lobby when offline
+            if (lobbyClient.getClientService().isOffline()) {
+                LOGGER.warn("Cannot create lobby while offline");
+                showAlert("Offline mode: cannot create lobby.");
+                return;
+            }
             int lobbyId = gridManager.createLobby();
             translationManager.addLobbyButton(buttonId, lobbyId);
             LOGGER.info("ButtonID: {}, LobbyID: {}", buttonId, lobbyId);