En Passant logic

src/backend/Board.java

@@ -12,12 +12,13 @@ public class Board {
 	private int[] selected = null; //for user touch
 	private ArrayList<int[]> highlighted = new ArrayList<>();
 	private ArrayList<Move> moveHistory = new ArrayList<>();
+	private int[] enPassantTarget = null;
 
 	public Board(int colNum, int lineNum) {
 		this.width = colNum;
 		this.height = lineNum;
 		this.pieces = new ArrayList<>();
-		//TODO
+	    this.enPassantTarget = null;
 	}
 	
 	public Board(Board other) {
@@ -26,6 +27,10 @@ public class Board {
 	    this.turnNumber = other.turnNumber;
 	    this.turnWhite = other.turnWhite;
 	    this.selected = other.selected != null ? new int[]{other.selected[0], other.selected[1]} : null;
+	    this.enPassantTarget = other.enPassantTarget != null
+	            ? new int[]{ other.enPassantTarget[0], other.enPassantTarget[1] }
+	            : null;
+
 
 	    this.pieces = new ArrayList<>();
 	    for (Piece p : other.pieces) {
@@ -44,29 +49,24 @@ public class Board {
 
 
 	public int getWidth() {
-		//TODO
 		return width;
 	}
 
 	public int getHeight() {
-		//TODO
 		return height;
 	}
 
 	public int getTurnNumber() {
-		//TODO
 		return turnNumber;
 	}
 
 	public boolean isTurnWhite() {
-		//TODO
 		return turnWhite;
 	}
 
 	public void setPiece(boolean isWhite, PieceType type, int x, int y) {
 		Piece piece = new Piece(isWhite, type, x, y);
 	    pieces.add(piece);
-		//TODO
 	}
 
 	public void populateBoard() {
@@ -97,12 +97,11 @@ public class Board {
 	    setPiece(false, PieceType.Bishop, 5, 7);
 	    setPiece(false, PieceType.Knight, 6, 7);
 	    setPiece(false, PieceType.Rook, 7, 7);
-		//TODO
 	}
 	
 	public void cleanBoard() {
 		pieces.clear();
-		//TODO
+	    enPassantTarget = null;
 	}
 	
 	public String toString() {
@@ -267,6 +266,12 @@ public class Board {
 	            Piece diagRight = getPieceAt(x + 1, forwardY);
 	            if (diagRight != null && diagRight.isWhite() != piece.isWhite())
 	                moves.add(new int[]{x + 1, forwardY});
+	            if (enPassantTarget != null) {
+	                int tx = enPassantTarget[0], ty = enPassantTarget[1];
+	                if (ty == forwardY && Math.abs(tx - x) == 1) {
+	                    moves.add(new int[]{ tx, ty });
+	                }
+	            }
 	            break;
 
 	        case Rook:
@@ -492,51 +497,78 @@ public void undoLastMove() {
 	
 public void playMove(Move move) {
     Piece piece = move.getPieceMoved();
-		 if (piece.getType() == PieceType.King && Math.abs(move.getToX() - move.getFromX()) == 2) {
+    int fromX = move.getFromX(), fromY = move.getFromY();
-		        int row = piece.isWhite() ? 0 : 7;
+    int toX   = move.getToX(),   toY   = move.getToY();
-		        // Kingside castling
-		        if (move.getToX() == 6) {
-		            Piece rook = getPieceAt(7, row);
-		            if (rook != null) {
-		                rook.setPosition(5, row); // rook moves to f1/f8
-		            }
-		        }
-		        // Queenside castling
-		        else if (move.getToX() == 2) {
-		            Piece rook = getPieceAt(0, row);
-		            if (rook != null) {
-		                rook.setPosition(3, row); // rook moves to d1/d8
-		            }
-		        }
-		    }
 
-		    // If a piece is captured, remove it from the board
+    // ─── castling ─────────────────────────────────────────────────────────
-		    if (move.getPieceCaptured() != null) {
+    if (piece.getType() == PieceType.King 
+        && Math.abs(toX - fromX) == 2) {
+        int row = piece.isWhite() ? 0 : 7;
+        // kingside
+        if (toX == 6) {
+            Piece rook = getPieceAt(7, row);
+            if (rook != null) rook.setPosition(5, row);
+        } 
+        // queenside
+        else {
+            Piece rook = getPieceAt(0, row);
+            if (rook != null) rook.setPosition(3, row);
+        }
+    }
+    // ─────────────────────────────────────────────────────────────────────
+
+    // ─── en passant capture ─────────────────────────────────────────────
+    if (piece.getType() == PieceType.Pawn
+        && enPassantTarget != null
+        && toX == enPassantTarget[0]
+        && toY == enPassantTarget[1]) {
+        // the pawn being captured sits on (toX, fromY)
+        Piece captured = getPieceAt(toX, fromY);
+        if (captured != null && captured.getType() == PieceType.Pawn) {
+            pieces.remove(captured);
+            move.setPieceCaptured(captured);  // so undo can restore it
+        }
+    }
+    // ─────────────────────────────────────────────────────────────────────
+
+    // ─── normal capture ─────────────────────────────────────────────────
+    else if (move.getPieceCaptured() != null) {
         pieces.remove(move.getPieceCaptured());
     }
+    // ─────────────────────────────────────────────────────────────────────
 
-		    // Update the moved piece's position
+    //  move the piece
-		    piece.setPosition(move.getToX(), move.getToY());
+    piece.setPosition(toX, toY);
 
+    // ─── pawn promotion ──────────────────────────────────────────────────
     if (piece.getType() == PieceType.Pawn) {
-		        // white promotes on y == height‐1, black on y == 0
         int promotionRank = piece.isWhite() ? height - 1 : 0;
-		        if (piece.getY() == promotionRank) {
+        if (toY == promotionRank) {
             piece.setType(PieceType.Queen);
         }
     }
+    // ─────────────────────────────────────────────────────────────────────
 
-		    // Save move in history for undo
+    // ─── update enPassantTarget ────────────────────────────────────────
+    if (piece.getType() == PieceType.Pawn
+        && Math.abs(toY - fromY) == 2) {
+        // record the square it jumped over
+        enPassantTarget = new int[]{ fromX, (fromY + toY) / 2 };
+    } else {
+        enPassantTarget = null;
+    }
+    // ─────────────────────────────────────────────────────────────────────
+
+    // record history & advance turn
     moveHistory.add(move);
-
-		    // Switch turn
     turnWhite = !turnWhite;
     turnNumber++;
 
-		    // Clear selection/highlight
+    // clear selection/highlight
     selected = null;
     highlighted.clear();
 }
+
 	public int evaluateBoard() {
 	    int score = 0;
 	    for (Piece piece : pieces) {

src/backend/Move.java

@@ -4,7 +4,7 @@ public class Move {
     private final Piece pieceMoved;
     private final int fromX, fromY;
     private final int toX, toY;
-    private final Piece pieceCaptured;
+    private Piece pieceCaptured;      // ← removed 'final' here
 
     public Move(Piece pieceMoved, int fromX, int fromY, int toX, int toY, Piece pieceCaptured) {
         this.pieceMoved     = pieceMoved;
@@ -21,4 +21,9 @@ public class Move {
     public int   getToX()           { return toX; }
     public int   getToY()           { return toY; }
     public Piece getPieceCaptured() { return pieceCaptured; }
+
+    
+    public void setPieceCaptured(Piece captured) {
+        this.pieceCaptured = captured;
+    }
 }