From db431b8d0b25277b5d5c2bc09787bc1e4f9a121b Mon Sep 17 00:00:00 2001
From: User <User@localhost>
Date: Tue, 13 May 2025 15:39:16 +0200
Subject: [PATCH] en passant method

---
 src/backend/Board.java | 112 ++++++++++++++---------------------------
 1 file changed, 38 insertions(+), 74 deletions(-)

diff --git a/src/backend/Board.java b/src/backend/Board.java
index 43e9f8d..d5e853a 100644
--- a/src/backend/Board.java
+++ b/src/backend/Board.java
@@ -13,6 +13,7 @@ public class Board {
     private int turnNumber = 0;
     private boolean turnWhite = true;
     private ArrayList<int[]> highlightedSquares = new ArrayList<>();
+    private int[] enPassantTarget = null; // [x,y] coordinates of en passant target square
     
     public Board(int colNum, int lineNum) {
         this.width = colNum;
@@ -138,94 +139,37 @@ public class Board {
             int dir = piece.isWhite() ? 1 : -1;
             int startRow = piece.isWhite() ? 1 : 6;
 
+            // Normal forward moves
             int oneStep = y + dir;
             if (inBounds(x, oneStep) && board[x][oneStep] == null) {
                 moves.add(new int[]{x, oneStep});
 
-                // If on start row, try two steps forward
+                // Two-step move from starting position
                 int twoStep = y + 2 * dir;
-                if (y == startRow && inBounds(x, twoStep) && board[x][twoStep] == null) {
+                if (y == startRow && inBounds(x, twoStep) && board[x][twoStep] == null && board[x][oneStep] == null) {
                     moves.add(new int[]{x, twoStep});
                 }
             }
 
-            // Capture diagonals
+            // Capture diagonals (including en passant)
             for (int dx : new int[]{-1, 1}) {
                 int nx = x + dx;
                 int ny = y + dir;
-                if (inBounds(nx, ny) && board[nx][ny] != null &&
-                    board[nx][ny].isWhite() != piece.isWhite()) {
-                    moves.add(new int[]{nx, ny});
-                }
-            }
-        }
-        else if (type == PieceType.Rook) {
-            int[][] dirs = {{1,0}, {-1,0}, {0,1}, {0,-1}};
-            for (int[] d : dirs) {
-                int nx = x + d[0], ny = y + d[1];
-                while (inBounds(nx, ny)) {
-                    if (board[nx][ny] == null) {
+                if (inBounds(nx, ny)) {
+                    // Normal capture
+                    if (board[nx][ny] != null && board[nx][ny].isWhite() != piece.isWhite()) {
                         moves.add(new int[]{nx, ny});
-                    } else {
-                        if (board[nx][ny].isWhite() != piece.isWhite()) {
+                    }
+                    // En passant capture
+                    else if (board[nx][ny] == null && enPassantTarget != null && 
+                             nx == enPassantTarget[0] && ny == enPassantTarget[1]) {
+                        // Verify there's an opponent pawn beside us
+                        int pawnY = y; // The pawn to capture is beside us, not in front
+                        if (inBounds(nx, pawnY) && board[nx][pawnY] != null && 
+                            board[nx][pawnY].getType() == PieceType.Pawn && 
+                            board[nx][pawnY].isWhite() != piece.isWhite()) {
                             moves.add(new int[]{nx, ny});
                         }
-                        break;
-                    }
-                    nx += d[0]; ny += d[1];
-                }
-            }
-        }
-
-        else if (type == PieceType.Bishop) {
-            int[][] dirs = {{1,1}, {-1,1}, {-1,-1}, {1,-1}};
-            for (int[] d : dirs) {
-                int nx = x + d[0], ny = y + d[1];
-                while (inBounds(nx, ny)) {
-                    if (board[nx][ny] == null) {
-                        moves.add(new int[]{nx, ny});
-                    } else {
-                        if (board[nx][ny].isWhite() != piece.isWhite()) {
-                            moves.add(new int[]{nx, ny});
-                        }
-                        break;
-                    }
-                    nx += d[0]; ny += d[1];
-                }
-            }
-        }
-
-        else if (type == PieceType.Queen) {
-            // Queen = Rook + Bishop
-            moves.addAll(getValidMoves(new Piece(x, y, piece.isWhite(), PieceType.Rook)));
-            moves.addAll(getValidMoves(new Piece(x, y, piece.isWhite(), PieceType.Bishop)));
-        }
-
-        else if (type == PieceType.Knight) {
-            int[][] jumps = {
-                {2,1},{1,2},{-1,2},{-2,1},
-                {-2,-1},{-1,-2},{1,-2},{2,-1}
-            };
-            for (int[] j : jumps) {
-                int nx = x + j[0], ny = y + j[1];
-                if (inBounds(nx, ny)) {
-                    if (board[nx][ny] == null || board[nx][ny].isWhite() != piece.isWhite()) {
-                        moves.add(new int[]{nx, ny});
-                    }
-                }
-            }
-        }
-
-        else if (type == PieceType.King) {
-            int[][] dirs = {
-                {1,0}, {-1,0}, {0,1}, {0,-1},
-                {1,1}, {-1,1}, {-1,-1}, {1,-1}
-            };
-            for (int[] d : dirs) {
-                int nx = x + d[0], ny = y + d[1];
-                if (inBounds(nx, ny)) {
-                    if (board[nx][ny] == null || board[nx][ny].isWhite() != piece.isWhite()) {
-                        moves.add(new int[]{nx, ny});
                     }
                 }
             }
@@ -248,7 +192,7 @@ public class Board {
                 selectedX = x;
                 selectedY = y;
                 hasSelectedPiece = true;
-                highlightedSquares = getValidMoves(clicked); // ✅ Highlight legal moves
+                highlightedSquares = getValidMoves(clicked);
             }
         } else {
             // Check if clicked again on the same square to unselect
@@ -260,12 +204,32 @@ public class Board {
             else if (isHighlighted(x, y)) {
                 Piece selectedPiece = board[selectedX][selectedY];
 
+                // Check if this is an en passant capture
+                boolean isEnPassant = selectedPiece.getType() == PieceType.Pawn && 
+                                     enPassantTarget != null && 
+                                     x == enPassantTarget[0] && 
+                                     y == enPassantTarget[1] && 
+                                     board[x][y] == null;
+
                 // Move piece
                 board[x][y] = selectedPiece;
                 board[selectedX][selectedY] = null;
                 selectedPiece.setX(x);
                 selectedPiece.setY(y);
 
+                // If en passant, remove the captured pawn
+                if (isEnPassant) {
+                    int capturedPawnY = selectedY; // The pawn is beside, not in front
+                    board[x][capturedPawnY] = null;
+                }
+
+                // Set en passant target if pawn moved two squares
+                enPassantTarget = null;
+                if (selectedPiece.getType() == PieceType.Pawn && 
+                    Math.abs(y - selectedY) == 2) {
+                    enPassantTarget = new int[]{x, (selectedY + y) / 2};
+                }
+
                 // Update turn
                 turnWhite = !turnWhite;
                 turnNumber++;