Fixed checkmate detection, simplified event handling

src/dev/kske/chess/board/Board.java

@@ -7,9 +7,6 @@ import java.util.Map;
 
 import dev.kske.chess.board.Piece.Color;
 import dev.kske.chess.board.Piece.Type;
-import dev.kske.chess.event.GameEvent;
-import dev.kske.chess.event.GameEvent.GameEventType;
-import dev.kske.chess.event.GameEventListener;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -22,12 +19,9 @@ public class Board {
 	private Piece[][]				boardArr;
 	private Map<Color, Position>	kingPos;
 
-	private List<GameEventListener> gameEventListeners;
-
 	public Board() {
 		boardArr			= new Piece[8][8];
 		kingPos				= new HashMap<>();
-		gameEventListeners	= new ArrayList<>();
 		initializeDefaultPositions();
 	}
 
@@ -53,11 +47,6 @@ public class Board {
 				return false;
 			}
 
-			// Detect check and stalemate on the opposite team
-			Color			oppositeColor	= piece.getColor().opposite();
-			GameEventType	eventType		= getGameEventType(oppositeColor);
-			if (eventType != GameEventType.NONE) notifyListeners(new GameEvent(this, eventType, oppositeColor));
-
 			return true;
 		}
 	}
@@ -114,6 +103,12 @@ public class Board {
 		return get(pos).getMoves(pos);
 	}
 
+	/**
+	 * Checks, if the king is in check.
+	 * 
+	 * @param color The color of the king to check
+	 * @return {@code true}, if the king is in check
+	 */
 	public boolean checkCheck(Color color) {
 		for (int i = 0; i < 8; i++)
 			for (int j = 0; j < 8; j++) {
@@ -125,10 +120,31 @@ public class Board {
 		return false;
 	}
 
-	public GameEventType getGameEventType(Color color) {
+	/**
+	 * Checks, if the king is in checkmate.
+	 * This requires the king to already be in check!
+	 * 
+	 * @param color The color of the king to check
+	 * @return {@code true}, if the king is in checkmate
+	 */
+	public boolean checkCheckmate(Color color) {
+		// Return false immediately if the king can move
+		if (!getMoves(kingPos.get(color)).isEmpty()) return false;
+		else {
+			for (Move move : getMoves(color)) {
+				Piece	capturePiece	= move(move);
+				boolean	check			= checkCheck(color);
+				revert(move, capturePiece);
+				if (!check) return false;
+			}
+			return true;
+		}
+	}
+
+	public GameState getGameEventType(Color color) {
 		return checkCheck(color)
-				? getMoves(kingPos.get(color)).isEmpty() ? GameEventType.CHECKMATE : GameEventType.CHECK
+				? checkCheckmate(color) ? GameState.CHECKMATE : GameState.CHECK
-				: getMoves(color).isEmpty() ? GameEventType.STALEMATE : GameEventType.NONE;
+				: getMoves(color).isEmpty() ? GameState.STALEMATE : GameState.NORMAL;
 	}
 
 	/**
@@ -161,14 +177,6 @@ public class Board {
 		return score;
 	}
 
-	public void registerGameEventListener(GameEventListener listener) {
-		gameEventListeners.add(listener);
-	}
-
-	private void notifyListeners(GameEvent evt) {
-		gameEventListeners.forEach(listener -> listener.onGameEvent(evt));
-	}
-
 	/**
 	 * Initialized the board array with the default chess pieces and positions.
 	 */

src/dev/kske/chess/board/GameState.java

@@ -0,0 +1,11 @@
+package dev.kske.chess.board;
+
+/**
+ * Project: <strong>Chess</strong><br>
+ * File: <strong>GameState.java</strong><br>
+ * Created: <strong>07.07.2019</strong><br>
+ * Author: <strong>Kai S. K. Engelbart</strong>
+ */
+public enum GameState {
+	CHECK, CHECKMATE, STALEMATE, NORMAL;
+}

src/dev/kske/chess/event/GameEvent.java

@@ -1,38 +0,0 @@
-package dev.kske.chess.event;
-
-import java.util.EventObject;
-
-import dev.kske.chess.board.Board;
-import dev.kske.chess.board.Piece.Color;
-
-/**
- * Project: <strong>Chess</strong><br>
- * File: <strong>GameEvent.java</strong><br>
- * Created: <strong>03.07.2019</strong><br>
- * Author: <strong>Kai S. K. Engelbart</strong>
- */
-public class GameEvent extends EventObject {
-
-	private static final long serialVersionUID = -6783035746521826589L;
-
-	private final Board			source;
-	private final GameEventType	eventType;
-	private final Color			color;
-
-	public GameEvent(Board source, GameEventType eventType, Color color) {
-		super(source);
-		this.source		= source;
-		this.eventType	= eventType;
-		this.color		= color;
-	}
-
-	public Board getSource() { return source; }
-
-	public GameEventType getEventType() { return eventType; }
-
-	public Color getColor() { return color; }
-
-	public static enum GameEventType {
-		CHECK, CHECKMATE, STALEMATE, NONE;
-	}
-}

src/dev/kske/chess/event/GameEventListener.java

@@ -1,12 +0,0 @@
-package dev.kske.chess.event;
-
-/**
- * Project: <strong>Chess</strong><br>
- * File: <strong>GameEventListener.java</strong><br>
- * Created: <strong>03.07.2019</strong><br>
- * Author: <strong>Kai S. K. Engelbart</strong>
- */
-public interface GameEventListener {
-
-	void onGameEvent(GameEvent evt);
-}

src/dev/kske/chess/game/AIPlayer.java

@@ -14,6 +14,7 @@ import dev.kske.chess.board.Piece.Color;
 public class AIPlayer extends Player {
 
 	private Move bestMove;
+	private int		count;
 
 	public AIPlayer(Board board, Color color) {
 		super(board, color);
@@ -21,19 +22,22 @@ public class AIPlayer extends Player {
 
 	@Override
 	public void requestMove() {
+		count = 0;
 		findBestMove(board, color, 0);
+		System.out.println("Moved processes: " + count);
 		game.onMove(this, bestMove);
 	}
 
 	private int findBestMove(Board board, Color color, int depth) {
 		int bestValue = Integer.MIN_VALUE;
 		for (Move move : board.getMoves(color)) {
+			++count;
 			Piece	capturePiece	= board.move(move);
 			int		teamValue		= board.evaluate(color);
 			int		enemyValue		= board.evaluate(color.opposite());
 			int		valueChange		= teamValue - enemyValue;
 
-			if (depth < 4) valueChange -= findBestMove(board, color.opposite(), depth + 1);
+			if (depth <= 3 && valueChange >= 0) valueChange -= findBestMove(board, color.opposite(), depth + 1);
 
 			if (valueChange > bestValue) {
 				bestValue = valueChange;

src/dev/kske/chess/game/Game.java

@@ -3,6 +3,7 @@ package dev.kske.chess.game;
 import java.util.Map;
 
 import dev.kske.chess.board.Board;
+import dev.kske.chess.board.GameState;
 import dev.kske.chess.board.Move;
 import dev.kske.chess.board.Piece.Color;
 import dev.kske.chess.ui.BoardPanel;
@@ -36,7 +37,18 @@ public class Game {
 		if (board.getPos(move).getColor() == player.color && board.attemptMove(move)) {
 			System.out.printf("%s: %s%n", player.color, move);
 			boardPanel.repaint();
-			players.get(player.color.opposite()).requestMove();
+
+			GameState eventType = board.getGameEventType(board.getDest(move).getColor().opposite());
+			switch (eventType) {
+				case CHECKMATE:
+				case STALEMATE:
+					System.out.printf("%s in %s!%n", player.color, eventType);
+					break;
+				case CHECK:
+					System.out.printf("%s in check!%n", player.color);
+				default:
+					players.get(player.color.opposite()).requestMove();
+			}
 		} else {
 			System.out.printf("%s: Illegal move!%n", player.getColor());
 			player.requestMove();

src/dev/kske/chess/ui/BoardPanel.java

@@ -8,13 +8,10 @@ import java.awt.event.ComponentEvent;
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.swing.JOptionPane;
 import javax.swing.JPanel;
 
 import dev.kske.chess.board.Board;
 import dev.kske.chess.board.Move;
-import dev.kske.chess.event.GameEvent;
-import dev.kske.chess.event.GameEventListener;
 
 /**
  * Project: <strong>Chess</strong><br>
@@ -26,7 +23,7 @@ import dev.kske.chess.event.GameEventListener;
  * this must be added to a parent component that allows the child to decide the
  * size.
  */
-public class BoardPanel extends JPanel implements GameEventListener {
+public class BoardPanel extends JPanel {
 
 	private static final long serialVersionUID = 6771148331334310216L;
 
@@ -90,18 +87,6 @@ public class BoardPanel extends JPanel implements GameEventListener {
 		}
 	}
 
-	@Override
-	public void onGameEvent(GameEvent evt) {
-		switch (evt.getEventType()) {
-			case CHECK:
-				JOptionPane.showMessageDialog(this, evt.getColor().toString() + " in check!");
-				break;
-			case CHECKMATE:
-				JOptionPane.showMessageDialog(this, evt.getColor().toString() + " in checkmate!");
-				break;
-		}
-	}
-
 	/**
 	 * Displays move destinations on the board.
 	 * 
@@ -142,10 +127,5 @@ public class BoardPanel extends JPanel implements GameEventListener {
 
 	public Board getBoard() { return board; }
 
-	public void setBoard(Board board) {
+	public void setBoard(Board board) { this.board = board; }
-		this.board = board;
-
-		// Register this BoardPanel as a GameEventListener to the board
-		board.registerGameEventListener(this);
-	}
 }

src/dev/kske/chess/ui/GameModeDialog.java

@@ -49,8 +49,7 @@ public class GameModeDialog extends JDialog {
 			Map<Color, Player> players = new HashMap<>();
 			players.put(Color.WHITE, new NaturalPlayer(boardPanel.getBoard(), Color.WHITE, boardPanel));
 			players.put(Color.BLACK, new AIPlayer(boardPanel.getBoard(), Color.BLACK));
-			new Game(players, boardPanel.getBoard(), boardPanel).start();
+			startGame(players, boardPanel);
-			dispose();
 		});
 		getContentPane().add(btnAI);
 
@@ -59,9 +58,13 @@ public class GameModeDialog extends JDialog {
 			Map<Color, Player> players = new HashMap<>();
 			players.put(Color.WHITE, new AIPlayer(boardPanel.getBoard(), Color.WHITE));
 			players.put(Color.BLACK, new AIPlayer(boardPanel.getBoard(), Color.BLACK));
-			new Game(players, boardPanel.getBoard(), boardPanel).start();
+			startGame(players, boardPanel);
-			dispose();
 		});
 		getContentPane().add(btnAI2);
 	}
+
+	private void startGame(Map<Color, Player> players, BoardPanel boardPanel) {
+		new Game(players, boardPanel.getBoard(), boardPanel).start();
+		dispose();
+	}
 }