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>
 * Author: <strong>Kai S. K. Engelbart</strong>
 */
public class Pawn extends Piece {

	public Pawn(Color color, Board board) {
		super(color, board);
	}

	@Override
	public boolean isValidMove(Move move) {
		boolean	step		= move.isVertical() && move.yDist == 1;
		boolean	doubleStep	= move.isVertical() && move.yDist == 2;
		boolean	strafe		= move.isDiagonal() && move.xDist == 1;
		boolean	enPassant	= false;
		if (getColor() == Color.WHITE) doubleStep &= move.pos.y == 6;
		else doubleStep &= move.pos.y == 1;

		// Mark move as pawn promotion if necessary
		if (move.ySign == 1 && move.pos.y == 6 || move.ySign == -1 && move.pos.y == 1)
			move.type = Move.Type.PAWN_PROMOTION;

		// Mark the move as en passant if necessary
		if (strafe && move.dest.equals(board.getEnPassantSquare())) {
			enPassant	= true;
			move.type	= Move.Type.EN_PASSANT;
		}

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

	@Override
	protected boolean isFreePath(Move move) {
		// Two steps forward
		if (move.yDist == 2)
			return board.getBoardArr()[move.pos.x][move.dest.y - move.ySign] == null && board.getDest(move) == null;
		// One step forward
		else if (move.xDist == 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;

		// Strafe left
		if (pos.x > 0) {
			Move move = new Move(pos, new Position(pos.x - 1, pos.y + sign));
			if (isFreePath(move)) moves.add(move);
		}

		// Strafe right
		if (pos.x < 7) {
			Move move = new Move(pos, new Position(pos.x + 1, pos.y + sign));
			if (isFreePath(move)) moves.add(move);
		}

		// Step forward
		if (sign == 1 && pos.y < 7 || sign == -1 && pos.y > 0) {
			Move move = new Move(pos, new Position(pos.x, pos.y + sign));
			if (isFreePath(move)) moves.add(move);
		}

		// Double step forward
		if (sign == 1 && pos.y == 1 || sign == -1 && pos.y == 6) {
			Move move = new Move(pos, new Position(pos.x, pos.y + 2 * sign));
			if (isFreePath(move)) moves.add(move);
		}

		// Mark moves as pawn promotion if necessary
		if (sign == 1 && pos.y == 6 || sign == -1 && pos.y == 1)
			moves.parallelStream().forEach(m -> m.type = Move.Type.PAWN_PROMOTION);

		// Add en passant move if necessary
		if (board.getEnPassantSquare() != null) {
			Move move = new Move(pos, board.getEnPassantSquare(), Move.Type.EN_PASSANT);
			if (move.isDiagonal() && move.xDist == 1) moves.add(move);
		}

		return moves;
	}

	@Override
	public Type getType() { return Type.PAWN; }
}