promotion with the undo !

src/backend/CheckManager.java

@@ -0,0 +1,50 @@
+package backend;
+
+import java.util.ArrayList;
+
+public class CheckManager {
+    private Board board;
+
+
+    public CheckManager(Board board) {
+        this.board = board;
+    }
+
+    // Check if the king of a given color is in check
+    public boolean isKingInCheck(boolean isWhite) {
+        int[] kingPosition = board.findKingPosition(isWhite); // You must implement this
+        for (Piece piece : board.getPieces()) {
+            if (piece.isWhite() != isWhite) {
+                ArrayList<int[]> enemyMoves = board.computeLegalMoves(piece); // you already have this?
+                for (int[] move : enemyMoves) {
+                    if (move[0] == kingPosition[0] && move[1] == kingPosition[1]) {
+                        return true;
+                    }
+                }
+            }
+        }
+        return false;
+    }
+
+    // Filter out illegal moves (those that leave king in check)
+    public ArrayList<int[]> getLegalMovesFiltered(boolean isWhite) {
+        ArrayList<int[]> allMoves = board.getAllMoves(isWhite); // You must write this or adapt it
+        ArrayList<int[]> legalMoves = new ArrayList<>();
+
+        for (int[] move : allMoves) {
+      //      board.makeMove(move); // Simulate move
+            boolean inCheck = isKingInCheck(isWhite);
+      //      board.undoMove();     // Undo move
+            if (!inCheck) {
+                legalMoves.add(move);
+            }
+        }
+
+        return legalMoves;
+    }
+
+    public boolean isCheckmate(boolean isWhite) {
+        if (!isKingInCheck(isWhite)) return false;
+        return getLegalMovesFiltered(isWhite).isEmpty();
+    }
+}

src/backend/Move.java

@@ -24,6 +24,7 @@ public class Move {
     public boolean isWhite() { return isWhite; }
     public PieceType getType() { return type; }
     public Piece getCapturedPiece() { return capturedPiece; }
+
 }