package dev.kske.chess.board;

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

/**
 * Project: <strong>Chess</strong><br>
 * File: <strong>Pawn.java</strong><br>
 * Created: <strong>01.07.2019</strong><br>
 *
 * @since Chess v0.1-alpha
 * @author Kai S. K. Engelbart
 */
public class Pawn extends Piece {

	/**
	 * Creates pawn {@link Piece}.
	 *
	 * @param color the color of this pawn
	 * @param board the board on which this pawn will be placed
	 */
	public Pawn(Color color, Board board) {
		super(color, board);
	}

	@Override
	public boolean isValidMove(Move move) {
		boolean step = move.isVertical() && move.getyDist() == 1;
		boolean doubleStep = move.isVertical() && move.getyDist() == 2;
		boolean strafe = move.isDiagonal() && move.getxDist() == 1;
		boolean enPassant
			= strafe && move.getDest().equals(board.getLog().getEnPassant());
		if (getColor() == Color.WHITE)
			doubleStep &= move.getPos().y == 6;
		else
			doubleStep &= move.getPos().y == 1;

		return enPassant || step ^ doubleStep ^ strafe
			&& move.getySign() == (getColor() == Color.WHITE ? -1 : 1)
			&& isFreePath(move);
	}

	@Override
	protected boolean isFreePath(Move move) {
		// Two steps forward
		if (move.getyDist() == 2)
			return board.getBoardArr()[move.getPos().x][move.getDest().y
				- move.getySign()] == null && board.getDest(move) == null;
		// One step forward
		else
			if (move.getxDist() == 0)
				return board.getDest(move) == null;
			// Capture move
			else
				return board.getDest(move) != null
					&& board.getDest(move).getColor() != getColor();
	}

	@Override
	protected List<Move> getPseudolegalMoves(Position pos) {
		List<Move> moves = new ArrayList<>();
		int sign = getColor() == Color.WHITE ? -1 : 1;
		boolean pawnPromotion
			= sign == 1 && pos.y == 6 || sign == -1 && pos.y == 1;

		// Strafe left
		if (pos.x > 0)
			addMoveIfValid(
				moves,
				pos,
				new Position(pos.x - 1, pos.y + sign),
				pawnPromotion
			);

		// Strafe right
		if (pos.x < 7)
			addMoveIfValid(
				moves,
				pos,
				new Position(pos.x + 1, pos.y + sign),
				pawnPromotion
			);

		// Step forward
		if (sign == 1 && pos.y < 7 || sign == -1 && pos.y > 0)
			addMoveIfValid(
				moves,
				pos,
				new Position(pos.x, pos.y + sign),
				pawnPromotion
			);

		// Double step forward
		if (sign == 1 && pos.y == 1 || sign == -1 && pos.y == 6)
			addMoveIfValid(
				moves,
				pos,
				new Position(pos.x, pos.y + 2 * sign),
				pawnPromotion
			);

		// Add en passant move if necessary
		if (board.getLog().getEnPassant() != null) {
			Move move = new EnPassant(pos, board.getLog().getEnPassant());
			if (move.isDiagonal() && move.getxDist() == 1)
				moves.add(move);
		}
		return moves;
	}

	private void addMoveIfValid(
		List<Move> moves, Position pos, Position dest, boolean pawnPromotion
	) {
		Move move = new Move(pos, dest);
		if (isFreePath(move))
			if (pawnPromotion)
				try {
					moves.add(new PawnPromotion(pos, dest, Queen.class));
					moves.add(new PawnPromotion(pos, dest, Rook.class));
					moves.add(new PawnPromotion(pos, dest, Knight.class));
					moves.add(new PawnPromotion(pos, dest, Bishop.class));
				} catch (Exception e) {
					e.printStackTrace();
				}
			else
				moves.add(move);
	}

	@Override
	public int getValue() { return 10; }
}