better undo

app/src/main/java/chess/model/ChessBoard.java

@@ -57,19 +57,14 @@ public class ChessBoard {
 	public void undoLastMove() {
 		assert this.lastMove != null: "Can't undo at the beginning!";
 
-		Move move = this.lastMove;
+		undoMove(this.lastMove, this.lastEjectedPiece);
+	}
 
+	public void undoMove(Move move, Piece deadPiece) {
 		Piece movingPiece = pieceAt(move.getFinish());
 		pieceComes(movingPiece, move.getStart());
-		pieceLeaves(move.getFinish());
+		pieceComes(deadPiece, move.getFinish());
 		movingPiece.unMove();
-
-		if (this.lastEjectedPiece == null)
-			return;
-
-		Piece piece = this.lastEjectedPiece;
-
-		pieceComes(piece, move.getFinish());
 	}
 
 	public boolean isCellEmpty(Coordinate coordinate) {

app/src/main/java/chess/model/Game.java

@@ -30,23 +30,6 @@ public class Game {
 		playerTurn = Color.getEnemy(playerTurn);
 	}
 
-	public boolean checkPromotion(Coordinate pieceCoords) {
-
-		Piece piece = getBoard().pieceAt(pieceCoords);
-
-		if (piece == null || !(piece instanceof Pawn))
-			return false;
-
-		int destY = pieceCoords.getY();
-
-		int enemyLine = piece.getColor() == Color.White ? 0 : 7;
-
-		if (destY != enemyLine)
-			return false;
-
-		return true;
-	}
-
 	public GameStatus checkGameStatus() {
 		final Color enemy = Color.getEnemy(getPlayerTurn());
 
@@ -63,20 +46,38 @@ public class Game {
 	}
 
 	public boolean pawnShouldBePromoted() {
-		if (pawnShouldBePromoted(Color.White))
-			return true;
-		return pawnShouldBePromoted(Color.Black);
+		return pawnPromotePosition() != null;
 	}
 
-	private boolean pawnShouldBePromoted(Color color) {
+	/**
+	 * 
+	 * @return Null if there is no pawn to promote
+	 */
+	public Coordinate pawnPromotePosition() {
+		Coordinate piecePos = pawnPromotePosition(Color.White);
+		if (piecePos != null)
+			return piecePos;
+		return pawnPromotePosition(Color.Black);
+	}
+
+	/**
+	 * 
+	 * @return Null if there is no pawn to promote
+	 */
+	private Coordinate pawnPromotePosition(Color color) {
 		int enemyLineY = color == Color.White ? 0 : 7;
 
 		for (int x = 0; x < Coordinate.VALUE_MAX; x++) {
-			if (checkPromotion(new Coordinate(x, enemyLineY)))
-				return true;
+			Coordinate pieceCoords = new Coordinate(x, enemyLineY);
+			Piece piece = getBoard().pieceAt(pieceCoords);
+
+			if (piece == null || !(piece instanceof Pawn) || piece.getColor() != color)
+				continue;
+
+			return pieceCoords;
 		}
 
-		return false;
+		return null;
 	}
 
 }

app/src/main/java/chess/model/Piece.java

@@ -4,12 +4,10 @@ public abstract class Piece {
 
 	private final Color color;
 	private int moved;
-	private int ejectedMoveNumber;
 
 	public Piece(Color color) {
 		this.color = color;
 		this.moved = 0;
-		this.ejectedMoveNumber = -1;
 	}
 
 	public void move() {
@@ -28,18 +26,6 @@ public abstract class Piece {
 		this.moved--;
 	}
 
-	public boolean isEjected() {
-		return this.ejectedMoveNumber != -1;
-	}
-
-	public int getEjectedMoveNumber() {
-		return ejectedMoveNumber;
-	}
-
-	public void eject(int moveNumber) {
-		this.ejectedMoveNumber = moveNumber;
-	}
-
 	public abstract <T> T accept(PieceVisitor<T> visitor);
 
 }