3DChess/app/src/main/java/chess/model/ChessBoard.java

package chess.model;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

import chess.model.pieces.King;
import chess.model.visitor.PawnIdentifier;
import chess.model.visitor.PiecePathChecker;

public class ChessBoard {
	public static class Cell {
		private Piece piece;

		public Cell() {
			this.piece = null;
		}

		public Piece getPiece() {
			return piece;
		}

		public void setPiece(Piece piece) {
			this.piece = piece;
		}

	}

	private final Cell[][] cells;
	private Move lastVirtualMove;
	private Move lastMove;
	private Piece lastEjectedPiece;

	private List<Move> cachedAllowedMoves = null;

	private final Coordinate kingPos[];

	public ChessBoard() {
		this.cells = new Cell[Coordinate.VALUE_MAX][Coordinate.VALUE_MAX];
		for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
			for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
				this.cells[i][j] = new Cell();
			}
		}
		this.lastVirtualMove = null;
		this.lastMove = null;
		this.lastEjectedPiece = null;
		this.kingPos = new Coordinate[Color.values().length];
	}

	public void applyMove(Move move) {
		assert move.isValid() : "Invalid move !";
		Piece deadPiece = pieceAt(move.getDeadPieceCoords());
		if (deadPiece != null) {
			this.lastEjectedPiece = deadPiece;
		} else {
			this.lastEjectedPiece = null;
		}
		Piece movingPiece = pieceAt(move.getStart());
		pieceLeaves(move.getDeadPieceCoords());
		pieceLeaves(move.getStart());
		pieceComes(movingPiece, move.getFinish());
		movingPiece.move();
		this.lastVirtualMove = move;
	}

	public void undoLastMove() {
		assert this.lastVirtualMove != null : "Can't undo at the beginning!";

		undoMove(this.lastVirtualMove, this.lastEjectedPiece);
	}

	public void undoMove(Move move, Piece deadPiece) {
		Piece movingPiece = pieceAt(move.getFinish());
		pieceComes(movingPiece, move.getStart());
		pieceLeaves(move.getFinish());
		pieceComes(deadPiece, move.getDeadPieceCoords());
		assert movingPiece != null;
		movingPiece.unMove();
	}

	public boolean isCellEmpty(Coordinate coordinate) {
		return pieceAt(coordinate) == null;
	}

	public Piece pieceAt(Coordinate coordinate) {
		if (!coordinate.isValid())
			return null;
		return cellAt(coordinate).getPiece();
	}

	public void clearBoard() {
		for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
			for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
				pieceLeaves(new Coordinate(i, j));
			}
		}
	}

	private Cell cellAt(Coordinate coordinate) {
		return this.cells[coordinate.getX()][coordinate.getY()];
	}

	public void pieceComes(Piece piece, Coordinate coordinate) {
		cellAt(coordinate).setPiece(piece);
		if (piece instanceof King)
			this.kingPos[piece.getColor().ordinal()] = coordinate;
	}

	public void pieceLeaves(Coordinate coordinate) {
		cellAt(coordinate).setPiece(null);
	}

	public Coordinate findKing(Color color) {
		// KingIdentifier kingIdentifier = new KingIdentifier(color);
		// for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
		// 	for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
		// 		Coordinate coordinate = new Coordinate(i, j);
		// 		Piece piece = pieceAt(coordinate);
		// 		if (kingIdentifier.isKing(piece)) {
		// 			return coordinate;
		// 		}
		// 	}
		// }
		// assert false : "No king found ?!";
		// return null;
		return kingPos[color.ordinal()];
	}

	public boolean isKingInCheck(Color color) {
		Coordinate kingPos = findKing(color);
		assert kingPos.isValid() : "King position is invalid!";

		for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
			for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
				Coordinate attackCoords = new Coordinate(i, j);
				Piece attackPiece = pieceAt(attackCoords);
				if (attackPiece == null || attackPiece.getColor() == color)
					continue;

				PiecePathChecker checker = new PiecePathChecker(this, new Move(attackCoords, kingPos));
				if (checker.isValid())
					return true;
			}
		}
		return false;
	}

	public boolean hasAllowedMoves(Color player) {
		return !getAllowedMoves(player).isEmpty();
	}

	public List<Move> getAllowedMoves(Color player) {
		if (this.cachedAllowedMoves != null) {
			return this.cachedAllowedMoves;
		}

		List<Move> result = new ArrayList<>();

		for (int x = 0; x < Coordinate.VALUE_MAX; x++) {
			for (int y = 0; y < Coordinate.VALUE_MAX; y++) {

				Coordinate start = new Coordinate(x, y);

				Piece piece = pieceAt(start);
				if (piece == null || piece.getColor() != player)
					continue;

				for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
					for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
						Coordinate destination = new Coordinate(i, j);
						Move move = new Move(start, destination);

						Piece destPiece = pieceAt(destination);

						if (destPiece != null && destPiece.getColor() == player)
							continue;

						PiecePathChecker piecePathChecker = new PiecePathChecker(this,
								move);
						if (!piecePathChecker.isValid())
							continue;

						applyMove(move);
						if (!isKingInCheck(player))
							result.add(move);
						undoLastMove();
					}
				}
			}
		}
		this.cachedAllowedMoves = result;
		return result;
	}

	public List<Coordinate> getAllowedMoves(Coordinate pieceCoords) {
		Piece piece = pieceAt(pieceCoords);
		if (piece == null)
			return null;

		Color player = piece.getColor();

		List<Coordinate> result = new ArrayList<>();

		for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
			for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
				Coordinate destination = new Coordinate(i, j);
				Move move = new Move(pieceCoords, destination);

				PiecePathChecker piecePathChecker = new PiecePathChecker(this,
						move);
				if (!piecePathChecker.isValid())
					continue;

				applyMove(move);
				if (!isKingInCheck(player))
					result.add(destination);
				undoLastMove();
			}
		}
		return result;
	}

	private boolean canCastle(Color color, int rookX, Direction kingDirection) {
		if (isKingInCheck(color))
			return false;

		int colorLine = color == Color.White ? 7 : 0;

		Coordinate kingCoords = new Coordinate(4, colorLine);
		Coordinate rookCoords = new Coordinate(rookX, colorLine);
		Piece king = pieceAt(kingCoords);
		Piece rook = pieceAt(rookCoords);

		if (king == null || rook == null || king.hasMoved() || rook.hasMoved())
			return false;

		for (int step = 1; step <= 2; step++) {
			Coordinate dest = Coordinate.fromIndex(kingCoords.toIndex() + step * kingDirection.getIndexOffset());
			Piece obstacle = pieceAt(dest);
			if (obstacle != null)
				return false;

			applyMove(new Move(kingCoords, dest));
			if (isKingInCheck(color)) {
				undoLastMove();
				return false;
			}
			undoLastMove();
		}

		Coordinate rookObstacleCoords = Coordinate.fromIndex(rookCoords.toIndex() - kingDirection.getIndexOffset());
		Piece obstacle = pieceAt(rookObstacleCoords);

		return obstacle == null;
	}

	public boolean canSmallCastle(Color color) {
		return canCastle(color, 7, Direction.Right);
	}

	public boolean canBigCastle(Color color) {
		return canCastle(color, 0, Direction.Left);
	}

	public boolean pawnShouldBePromoted() {
		return pawnPromotePosition() != null;
	}

	/**
	 * 
	 * @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;
		PawnIdentifier identifier = new PawnIdentifier(color);

		for (int x = 0; x < Coordinate.VALUE_MAX; x++) {
			Coordinate pieceCoords = new Coordinate(x, enemyLineY);
			Piece piece = pieceAt(pieceCoords);

			if (identifier.isPawn(piece))
				return pieceCoords;

		}

		return null;
	}

	@Override
	public int hashCode() {
		int result = 0;
		for (int i = 0; i < Coordinate.VALUE_MAX; i++) {
			for (int j = 0; j < Coordinate.VALUE_MAX; j++) {
				Piece piece = pieceAt(new Coordinate(i, j));
				if (piece == null)
					continue;
				result = Objects.hash(result, piece.getColor(), new Coordinate(i, j), piece);
			}
		}
		return result;
	}

	public Move getLastMove() {
		return this.lastMove;
	}

	public void setLastMove(Move lastMove) {
		this.lastMove = lastMove;
		this.cachedAllowedMoves = null;
	}

	@Override
	public boolean equals(Object obj) {
		if (obj instanceof ChessBoard board)
			return board.hashCode() == this.hashCode();
		return false;
	}

}