feat/view-manager (#20)

* feat(View & Controller): Added screens for game, main menu and pause menu

Added screens:
    - MainMenuView & MainMenuController.
    - GameView & GameController.
    - PauseView & PauseController.

* refactor(MainMenuController): MainMenuController constructs game

MainMenuController constructs games and allows the creation of a new game
without terminating the process:

* feat(View): Resource Manager for loading game textures

Add ResourceManager for centralized texture loading.

Implemented a singleton ResourceManager to handle loading of game textures.
Ensures each texture is loaded only once, improving performance and memory efficiency.

Includes fallback logic to return a default "missing texture" image
when a resource cannot be found.
Prevents accidental instantiation by enforcing the singleton pattern.

13 files changed, 415 insertions, 101 deletions

diff --git a/pacman/controller/src/main/java/com/gr15/pacman/controller/GameApp.java b/pacman/controller/src/main/java/com/gr15/pacman/controller/GameApp.java
index ffd4493..98a8c5e 100644
--- a/pacman/controller/src/main/java/com/gr15/pacman/controller/GameApp.java
+++ b/pacman/controller/src/main/java/com/gr15/pacman/controller/GameApp.java
@@ -1,12 +1,18 @@
 package com.gr15.pacman.controller;
 
-import java.io.InputStream;
-
 import com.gr15.pacman.model.GameState;
 import com.gr15.pacman.model.GameStateBuilder;
-import com.gr15.pacman.view.GameView;
+import com.gr15.pacman.view.ViewManager;
+import com.gr15.pacman.view.screen.GameView;
+import com.gr15.pacman.view.screen.MainMenuView;
+import com.gr15.pacman.view.screen.PauseView;
+import com.gr15.pacman.view.ViewManager.ViewKeys;
+import com.gr15.pacman.controller.screen.GameController;
+import com.gr15.pacman.controller.screen.MainMenuController;
+import com.gr15.pacman.controller.screen.PauseController;
 
 import javafx.application.Application;
+import javafx.scene.Scene;
 import javafx.stage.Stage;
 
 /**
@@ -15,9 +21,8 @@ import javafx.stage.Stage;
 public class GameApp
     extends Application {
 
-    GameController gameController;
-    GameView gameView;
-    GameState gameState;
+    private ViewManager viewManager = new ViewManager();
+    private MainMenuView mainMenuView = new MainMenuView();
 
     @Override
     public void start(Stage primaryStage) throws Exception {
@@ -25,18 +30,12 @@ public class GameApp
         primaryStage.setResizable(false);
         primaryStage.setFullScreen(true);
 
-        InputStream inputStream = this.getClass()
-            .getResourceAsStream("/testGameState.json");
-        GameState gameState = GameStateBuilder.fromJson(inputStream);
-        inputStream.close();
-        int tileWidth = gameState.getBoard().getWidth();
-        int tileHeight = gameState.getBoard().getHeight();
-        gameView = new GameView(gameState,tileWidth, tileHeight);
-        primaryStage.setScene(gameView);
-
-        gameController = new GameController(gameState, gameView);
-        gameController.startGameLoop();
+        viewManager.addView(ViewKeys.MAIN_MENU, mainMenuView);
+        viewManager.showView(ViewKeys.MAIN_MENU);
+        new MainMenuController(viewManager, mainMenuView);
 
+        Scene scene = new Scene(viewManager, 1920, 1080);
+        primaryStage.setScene(scene);
         primaryStage.show();
     }
     
diff --git a/pacman/controller/src/main/java/com/gr15/pacman/controller/GameController.java b/pacman/controller/src/main/java/com/gr15/pacman/controller/GameController.java
deleted file mode 100644
index a334576..0000000
--- a/pacman/controller/src/main/java/com/gr15/pacman/controller/GameController.java
+++ /dev/null
@@ -1,63 +0,0 @@
-package com.gr15.pacman.controller;
-
-import com.gr15.pacman.model.GameState;
-import com.gr15.pacman.model.entities.Entity.Direction;
-import com.gr15.pacman.view.GameView;
-
-import javafx.animation.AnimationTimer;
-
-/**
- * GameController
- */
-public class GameController {
-
-    private GameState gameState;
-    private GameView gameView;
-
-    private AnimationTimer gameLoop;
-    private long lastUpdate = 0;
-
-    public GameController(GameState gameState, GameView gameView) {
-        this.gameState = gameState;
-        this.gameView = gameView;
-
-        setupEventHandlers();
-        gameLoop = new AnimationTimer() {
-
-            @Override
-            public void handle(long now) {
-                if (lastUpdate == 0) {
-                    lastUpdate = now;
-                    return; /* returning early, since no time have elapsed */
-                }
-                
-                double deltaSeconds = (now - lastUpdate) / 1_000_000_000.0;
-                lastUpdate = now;
-
-                gameState.update(deltaSeconds);
-                gameView.renderGame(deltaSeconds);
-            }
-        };
-    }
-
-    private void setupEventHandlers() {
-        gameView.setOnKeyPressed(event -> {
-            switch (event.getCode()) {
-                case UP -> gameState.getPacman().setDirection(Direction.UP);
-                case DOWN -> gameState.getPacman().setDirection(Direction.DOWN);
-                case LEFT -> gameState.getPacman().setDirection(Direction.LEFT);
-                case RIGHT -> gameState.getPacman().setDirection(Direction.RIGHT);
-                default -> {}
-            }
-        });
-    }
-
-    public void startGameLoop() {
-        gameLoop.start();
-    }
-
-    public void stopGameLoop() {
-        lastUpdate = 0;
-        gameLoop.stop();
-    }
-}
diff --git a/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/GameController.java b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/GameController.java
new file mode 100644
index 0000000..0bb4e87
--- /dev/null
+++ b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/GameController.java
@@ -0,0 +1,72 @@
+package com.gr15.pacman.controller.screen;
+
+import com.gr15.pacman.model.GameState;
+import com.gr15.pacman.model.entities.Entity.Direction;
+import com.gr15.pacman.view.ViewManager;
+import com.gr15.pacman.view.screen.GameView;
+import com.gr15.pacman.view.ViewManager.ViewKeys;
+
+import javafx.animation.AnimationTimer;
+import javafx.scene.input.KeyEvent;
+
+/**
+ * GameController
+ */
+public class GameController {
+
+    private final ViewManager viewManager;
+    private final GameState gameState;
+    private final GameView gameView;
+
+    private final AnimationTimer gameLoop;
+    private long lastUpdate = 0;
+
+    public GameController(GameState gameState, GameView gameView, ViewManager viewManager) {
+        this.viewManager = viewManager;
+        this.gameState = gameState;
+        this.gameView = gameView;
+
+        gameLoop = new AnimationTimer() {
+
+            @Override
+            public void handle(long now) {
+                if (lastUpdate == 0) {
+                    lastUpdate = now;
+                    return; /* returning early, since no time have elapsed */
+                }
+                
+                double deltaSeconds = (now - lastUpdate) / 1_000_000_000.0;
+                lastUpdate = now;
+
+                gameState.update(deltaSeconds);
+                gameView.renderGame(deltaSeconds);
+            }
+        };
+    }
+
+    public void handleKeyEvent(KeyEvent event) {
+        switch (event.getCode()) {
+            case UP -> gameState.getPacman().setDirection(Direction.UP);
+            case DOWN -> gameState.getPacman().setDirection(Direction.DOWN);
+            case LEFT -> gameState.getPacman().setDirection(Direction.LEFT);
+            case RIGHT -> gameState.getPacman().setDirection(Direction.RIGHT);
+            case ESCAPE -> {
+                viewManager.showView(ViewKeys.PAUSE);
+                stopGameLoop();
+            }
+            default -> {}
+        }
+    }
+
+    public void startGameLoop() {
+        gameView.requestFocusForInput();
+        gameView.setOnKeyPressed(event -> handleKeyEvent(event));
+
+        gameLoop.start();
+    }
+
+    public void stopGameLoop() {
+        lastUpdate = 0;
+        gameLoop.stop();
+    }
+}
diff --git a/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/MainMenuController.java b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/MainMenuController.java
new file mode 100644
index 0000000..9477171
--- /dev/null
+++ b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/MainMenuController.java
@@ -0,0 +1,47 @@
+package com.gr15.pacman.controller.screen;
+
+import com.gr15.pacman.model.GameState;
+import com.gr15.pacman.model.GameStateBuilder;
+import com.gr15.pacman.view.ViewManager;
+import com.gr15.pacman.view.screen.GameView;
+import com.gr15.pacman.view.screen.MainMenuView;
+import com.gr15.pacman.view.screen.PauseView;
+import com.gr15.pacman.view.ViewManager.ViewKeys;
+
+/**
+ * MainMenuController
+ */
+public class MainMenuController {
+
+    private final ViewManager viewManager;
+    private final MainMenuView mainMenuView;
+
+    public MainMenuController(ViewManager viewManager, MainMenuView mainMenuView) {
+        this.viewManager = viewManager;
+        this.mainMenuView = mainMenuView;
+        initializeButtons();
+    }
+
+    private void initializeButtons() {
+        mainMenuView.getStartButton().setOnAction((event) -> {
+            GameState gameState = GameStateBuilder.fromJson(
+                this.getClass().getResourceAsStream("/testGameState.json"));
+            int tileWidth = gameState.getBoard().getWidth();
+            int tileHeight = gameState.getBoard().getHeight();
+            GameView gameView = new GameView(gameState, tileWidth, tileHeight);
+            PauseView pauseView = new PauseView();
+            GameController gameController = new GameController(gameState, 
+                gameView, viewManager);
+            new PauseController(pauseView, gameController, viewManager);
+            viewManager.removeView(ViewKeys.GAME_VIEW);
+            viewManager.removeView(ViewKeys.PAUSE);
+            viewManager.addView(ViewKeys.GAME_VIEW, gameView);
+            viewManager.addView(ViewKeys.PAUSE, pauseView);
+            viewManager.showView(ViewKeys.GAME_VIEW);
+            gameController.startGameLoop();
+        });
+        mainMenuView.getQuitButton().setOnAction((event) -> {
+            System.exit(0);
+        });
+    }
+}
diff --git a/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/PauseController.java b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/PauseController.java
new file mode 100644
index 0000000..88b60ea
--- /dev/null
+++ b/pacman/controller/src/main/java/com/gr15/pacman/controller/screen/PauseController.java
@@ -0,0 +1,34 @@
+package com.gr15.pacman.controller.screen;
+
+import com.gr15.pacman.view.ViewManager;
+import com.gr15.pacman.view.ViewManager.ViewKeys;
+import com.gr15.pacman.view.screen.PauseView;
+
+/**
+ * PauseController
+ */
+public class PauseController {
+
+    private final PauseView pauseView;
+    private final GameController gameController;
+    private final ViewManager viewManager;
+
+    public PauseController(PauseView pauseView, GameController gameController,
+        ViewManager viewManager) {
+        this.gameController = gameController;
+        this.pauseView = pauseView;
+        this.viewManager = viewManager;
+        initialize();
+    }
+
+    private void initialize() {
+        pauseView.getQuitButton().setOnAction((e) -> { System.exit(0); });
+        pauseView.getMainMenuButton().setOnAction((e) -> {
+            viewManager.showView(ViewKeys.MAIN_MENU);
+        });
+        pauseView.getResumeButton().setOnAction((e) -> {
+            viewManager.showView(ViewKeys.GAME_VIEW);
+            gameController.startGameLoop();
+        });
+    }
+}
diff --git a/pacman/controller/src/main/java/module-info.java b/pacman/controller/src/main/java/module-info.java
index 9df9dd5..c240f2c 100644
--- a/pacman/controller/src/main/java/module-info.java
+++ b/pacman/controller/src/main/java/module-info.java
@@ -6,5 +6,7 @@ module com.gr15.pacman.controller {
     requires javafx.graphics;
     requires com.gr15.pacman.view;
     requires com.gr15.pacman.model;
+
     exports com.gr15.pacman.controller;
+    exports com.gr15.pacman.controller.screen;
 }
diff --git a/pacman/view/src/main/java/com/gr15/pacman/view/ResourceManager.java b/pacman/view/src/main/java/com/gr15/pacman/view/ResourceManager.java
new file mode 100644
index 0000000..3e7103e
--- /dev/null
+++ b/pacman/view/src/main/java/com/gr15/pacman/view/ResourceManager.java
@@ -0,0 +1,77 @@
+package com.gr15.pacman.view;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import javafx.scene.image.Image;
+
+/**
+ * The {@code ResourceManager} class is a singleton responsible
+ * for managing {@link Image} resources used in the application.
+ * It provides caching to avoid loading the same {@link Image} multiple times,
+ * improving performance and resource efficiency.
+ *
+ * If an {@link Image} cannot be found at the specified path,
+ * a default "missing texture" {@link Image} is returned.
+ */
+
+public class ResourceManager {
+
+    /** Singleton instance of ResourceManager. */
+    private static ResourceManager instance;
+
+    /** Cache to store loaded images keyed by their file path. */
+    private Map<String, Image> resources = new HashMap<>();
+
+    /** Image to be used when the requested image is not found. */
+    private Image missingTexture = new Image(
+        this.getClass().getResourceAsStream("/gameAssets/missingTexture.png"));
+
+    /**
+     * Private constructor to prevent external instantiation
+     * and enforce singleton pattern.
+     */
+    private ResourceManager() {}
+
+    /**
+     * Returns the singleton instance of {@code ResourceManager}.
+     * If it does not exist yet, it is created.
+     *
+     * @return the singleton instance of {@code ResourceManager}.
+     */
+    public static ResourceManager getInstance() {
+        if (instance == null) {
+            instance = new ResourceManager();
+            return instance;
+        } else {
+            return instance;
+        }
+    }
+
+    /**
+     * Returns an {@link Image} corresponding to the specified resource path.
+     * If the {@link Image} has already been loaded before,
+     * it is returned from the cache. Otherwise, it is loaded
+     * and added to the cache.
+     * If loading fails (e.g., if the file does not exist),
+     * the default "missing texture" {@link Image} is returned.
+     *
+     * @param path the path to the image resource, relative to the classpath
+     * @return the loaded {@link Image},
+     * or a default image if the resource could not be found
+     */
+    public Image getTexture(String path) {
+        if (resources.containsKey(path)) {
+            return resources.get(path);
+        } else {
+            try {
+                Image texture = new Image(
+                    this.getClass().getResourceAsStream(path));
+                resources.put(path, texture);
+                return texture;
+            } catch (NullPointerException e) {
+                return missingTexture;
+            }
+        }
+    }
+}
diff --git a/pacman/view/src/main/java/com/gr15/pacman/view/ViewManager.java b/pacman/view/src/main/java/com/gr15/pacman/view/ViewManager.java
new file mode 100644
index 0000000..2f1eb3a
--- /dev/null
+++ b/pacman/view/src/main/java/com/gr15/pacman/view/ViewManager.java
@@ -0,0 +1,92 @@
+package com.gr15.pacman.view;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import javafx.geometry.Insets;
+import javafx.scene.Parent;
+import javafx.scene.layout.Background;
+import javafx.scene.layout.BackgroundFill;
+import javafx.scene.layout.CornerRadii;
+import javafx.scene.layout.StackPane;
+import javafx.scene.paint.Color;
+
+/**
+ * The {@code ViewManager} class is responsible for managing and switching between 
+ * different views in a JavaFX application. It extends {@code StackPane} and provides
+ * methods to add, remove, check for, and display views identified by an enum key.
+ */
+public class ViewManager 
+    extends StackPane {
+
+    /**
+     * Enumeration of all possible view keys used to identify different views.
+     */
+    public enum ViewKeys { MAIN_MENU, GAME_VIEW, PAUSE };
+
+    /**
+     * A map that stores views associated with their corresponding keys.
+     */
+    private Map<ViewKeys, Parent> views = new HashMap<>();
+
+    /**
+     * Constructs a new {@code ViewManager} with a black background.
+     */
+    public ViewManager() {
+        setBackground(new Background(new BackgroundFill(
+            Color.BLACK,
+            CornerRadii.EMPTY,
+            Insets.EMPTY
+        )));
+    }
+
+    /**
+     * Adds a new view to the manager.
+     *
+     * @param key  the key to identify the view.
+     * @param view the view to be added.
+     * @throws IllegalArgumentException if a view with the same key already exists.
+     */
+    public void addView(ViewKeys key, Parent view) {
+        if (views.containsKey(key)) {
+            throw new IllegalArgumentException(
+                "View with key " + key + " already exists.");
+        } else {
+            views.put(key, view);
+        }
+    }
+
+    /**
+     * Displays the view associated with the specified key.
+     *
+     * @param key the key of the view to be shown.
+     * @throws IllegalArgumentException if no view exists for the specified key.
+     */
+    public void showView(ViewKeys key) {
+        if (!views.containsKey(key)) {
+            throw new IllegalArgumentException(
+                "No view with key " + key + " exists.");
+        } else {
+            getChildren().setAll(views.get(key));
+        }
+    }
+
+    /**
+     * Checks whether a view exists for the specified key.
+     *
+     * @param key the key to check.
+     * @return {@code true} if a view with the key exists, {@code false} otherwise.
+     */
+    public boolean hasView(ViewKeys key) {
+        return views.containsKey(key);
+    }
+
+    /**
+     * Removes the view associated with the specified key.
+     *
+     * @param key the key of the view to remove.
+     */
+    public void removeView(ViewKeys key) {
+        views.remove(key);
+    }
+}
diff --git a/pacman/view/src/main/java/com/gr15/pacman/view/GameView.java b/pacman/view/src/main/java/com/gr15/pacman/view/screen/GameView.java
index d9235f6..33c4e2d 100644
--- a/pacman/view/src/main/java/com/gr15/pacman/view/GameView.java
+++ b/pacman/view/src/main/java/com/gr15/pacman/view/screen/GameView.java
@@ -1,18 +1,20 @@
-package com.gr15.pacman.view;
+package com.gr15.pacman.view.screen;
 
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import com.gr15.pacman.view.ResourceManager;
+import com.gr15.pacman.view.Sprite;
+
 import com.gr15.pacman.model.GameState;
 import com.gr15.pacman.model.Board.TileType;
 
-import javafx.scene.Scene;
+import javafx.geometry.Pos;
 import javafx.scene.canvas.Canvas;
 import javafx.scene.canvas.GraphicsContext;
 import javafx.scene.image.Image;
-import javafx.scene.layout.StackPane;
-import javafx.scene.paint.Color;
+import javafx.scene.layout.VBox;
 
 import com.gr15.pacman.model.entities.Entity;
 import com.gr15.pacman.model.entities.Items;
@@ -20,17 +22,16 @@ import com.gr15.pacman.model.entities.Items;
 /**
  * GameView
  */
-public class GameView 
-    extends Scene {
+public class GameView
+    extends VBox {
 
     /* Utils */
     private Canvas canvas;
     private GraphicsContext gc;
     private GameState gameState;
-    private StackPane root;
 
-    private float scaleX = 4.0f;
-    private float scaleY = 4.0f;
+    private float scaleX = 3.0f;
+    private float scaleY = 3.0f;
     private int tileWidth;
     private int tileHeight;
 
@@ -41,24 +42,20 @@ public class GameView
     /* UI elements */
     private Sprite pacmanSprite;
 
-    public GameView(GameState gameState, 
-        int tileWidth, int tileHeight) {
-        super(new StackPane());
-        root = (StackPane)super.getRoot();
-
+    public GameView(GameState gameState, int tileWidth, int tileHeight) {
         canvas = new Canvas(tileWidth * 16 * scaleX, tileHeight * 16 * scaleY);
         gc = canvas.getGraphicsContext2D();
-        root.getChildren().add(canvas);
+        getChildren().add(canvas);
+        setAlignment(Pos.CENTER);
 
         this.tileHeight = tileHeight;
         this.tileWidth = tileWidth;
         this.gameState = gameState;
-        this.setFill(Color.BLACK);
         
-        tileTextures.put(TileType.WALL, new Image(
-            this.getClass().getResourceAsStream("/gameAssets/wall.png")));
-        pacmanSprite = new Sprite(new Image(
-            this.getClass().getResourceAsStream("/gameAssets/pacmanRight.png")), 
+        tileTextures.put(TileType.WALL, ResourceManager.getInstance()
+            .getTexture("/gameAssets/wall.png"));
+        pacmanSprite = new Sprite(
+            ResourceManager.getInstance().getTexture("/gameAssets/pacmanRight.png"),
             gameState.getPacman().getPositionX() - 0.5, 
             gameState.getPacman().getPositionY() - 0.5, 
             16 * scaleX, 16 * scaleY);
@@ -106,8 +103,11 @@ public class GameView
                     pos.y() * 16 * scaleY,
                     texture.getWidth() * scaleX,
                     texture.getHeight() * scaleY);
-
             }
         });
     }
+
+    public void requestFocusForInput() {
+        requestFocus();
+    }
 }
diff --git a/pacman/view/src/main/java/com/gr15/pacman/view/screen/MainMenuView.java b/pacman/view/src/main/java/com/gr15/pacman/view/screen/MainMenuView.java
new file mode 100644
index 0000000..c849fb9
--- /dev/null
+++ b/pacman/view/src/main/java/com/gr15/pacman/view/screen/MainMenuView.java
@@ -0,0 +1,27 @@
+package com.gr15.pacman.view.screen;
+
+import javafx.geometry.Pos;
+import javafx.scene.control.Button;
+import javafx.scene.control.Menu;
+import javafx.scene.layout.VBox;
+
+/**
+ * MainMenuView
+ */
+public class MainMenuView
+    extends VBox {
+
+    private Button newGameButton = new Button("New Game");
+    private Button resumeButton = new Button("Resume");
+    private Button quitButton = new Button("Exit Game");
+    
+    public MainMenuView() {
+        resumeButton.setDisable(true);
+        getChildren().addAll(resumeButton, newGameButton, quitButton);
+        setAlignment(Pos.CENTER);
+    }
+
+    public Button getNewGameButton() { return this.newGameButton; }
+    public Button getResumeButton() { return this.resumeButton; }
+    public Button getQuitButton() { return this.quitButton; }
+}
diff --git a/pacman/view/src/main/java/com/gr15/pacman/view/screen/PauseView.java b/pacman/view/src/main/java/com/gr15/pacman/view/screen/PauseView.java
new file mode 100644
index 0000000..7dd46e2
--- /dev/null
+++ b/pacman/view/src/main/java/com/gr15/pacman/view/screen/PauseView.java
@@ -0,0 +1,25 @@
+package com.gr15.pacman.view.screen;
+
+import javafx.geometry.Pos;
+import javafx.scene.control.Button;
+import javafx.scene.layout.VBox;
+
+/**
+ * PauseView
+ */
+public class PauseView
+    extends VBox {
+
+    private Button resumeButton = new Button("Resume");
+    private Button mainMenuButton = new Button("Main Menu");
+    private Button quitButton = new Button("Quit");
+    
+    public PauseView() {
+        getChildren().addAll(resumeButton, mainMenuButton, quitButton);
+        setAlignment(Pos.CENTER);
+    }
+
+    public Button getResumeButton() { return this.resumeButton; }
+    public Button getMainMenuButton() { return this.mainMenuButton; }
+    public Button getQuitButton() { return this.quitButton; }
+}
diff --git a/pacman/view/src/main/java/module-info.java b/pacman/view/src/main/java/module-info.java
index f50cafa..f91361e 100644
--- a/pacman/view/src/main/java/module-info.java
+++ b/pacman/view/src/main/java/module-info.java
@@ -5,5 +5,7 @@ module com.gr15.pacman.view {
     requires javafx.controls;
     requires javafx.graphics;
     requires com.gr15.pacman.model;
+
+    exports com.gr15.pacman.view.screen;
     exports com.gr15.pacman.view;
 }
diff --git a/pacman/view/src/main/resources/gameAssets/missingTexture.png b/pacman/view/src/main/resources/gameAssets/missingTexture.png
new file mode 100644
index 0000000..7317870
--- /dev/null
+++ b/pacman/view/src/main/resources/gameAssets/missingTexture.png