chess/src/main/java/dev/kske/chess/board/Piece.java

package dev.kske.chess.board;

import java.util.Iterator;
import java.util.List;
import java.util.Objects;

/**
 * Represents a piece on a board with a color.<br>
 * <br>
 * Project: <strong>Chess</strong><br>
 * File: <strong>Piece.java</strong><br>
 * Created: <strong>01.07.2019</strong><br>
 *
 * @since Chess v0.1-alpha
 * @author Kai S. K. Engelbart
 */
public abstract class Piece implements Cloneable {

	private final Color color;
	protected Board board;

	/**
	 * Initializes a piece.
	 *
	 * @param color the color of this piece
	 * @param board the board on which this piece is placed
	 */
	public Piece(Color color, Board board) {
		this.color = color;
		this.board = board;
	}

	/**
	 * Generated a list of legal moves this piece can make.
	 *
	 * @param pos the position of this piece
	 * @return a list of legal moves this piece can make
	 */
	public List<Move> getMoves(Position pos) {
		List<Move> moves = getPseudolegalMoves(pos);
		for (Iterator<Move> iterator = moves.iterator(); iterator.hasNext();) {
			Move move = iterator.next();
			board.move(move);
			if (board.checkCheck(getColor()))
				iterator.remove();
			board.revert();
		}
		return moves;
	}

	/**
	 * Generates a list of pseudo legal moves this piece can make.
	 *
	 * @param pos the position of this piece
	 * @return a list of pseudo legal moves this piece can make
	 */
	protected abstract List<Move> getPseudolegalMoves(Position pos);

	/**
	 * Checks, if a given move is valid.
	 *
	 * @param move the move to check
	 * @return {@code true} if the move is valid
	 */
	public abstract boolean isValidMove(Move move);

	/**
	 * Checks, if the squares between the position and the destination of a move
	 * are
	 * free.
	 *
	 * @param move The move to check
	 * @return {@true} if the path is free
	 */
	protected boolean isFreePath(Move move) {
		for (
			int i = move.getPos().x + move.getxSign(), j
				= move.getPos().y + move.getySign();
			i != move.getDest().x
				|| j != move.getDest().y;
			i += move.getxSign(), j += move.getySign()
		)
			if (board.getBoardArr()[i][j] != null)
				return false;
		return checkDestination(move);
	}

	/**
	 * Checks if the destination of a move is empty or a piece from the opposing
	 * team
	 *
	 * @param move The move to check
	 * @return {@code false} if the move's destination is from the same team
	 */
	protected final boolean checkDestination(Move move) {
		return board.getDest(move) == null
			|| board.getDest(move).getColor() != getColor();
	}

	@Override
	public Object clone() {
		Piece piece = null;
		try {
			piece = (Piece) super.clone();
		} catch (CloneNotSupportedException ex) {
			ex.printStackTrace();
		}
		return piece;
	}

	@Override
	public String toString() {
		return String.format("%s[color=%s]", getClass().getSimpleName(), color);
	}

	@Override
	public int hashCode() {
		return Objects.hash(color);
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Piece other = (Piece) obj;
		return color == other.color;
	}

	/**
	 * @return the standard value of this {@link Piece} that can be used for
	 *         board
	 *         evaluation
	 */
	public abstract int getValue();

	/**
	 * @return The first character of this {@link Piece} in algebraic notation
	 *         and
	 *         lower case
	 */
	public char firstChar() {
		return Character.toLowerCase(getClass().getSimpleName().charAt(0));
	}

	/**
	 * @param firstChar the first character of a piece's name
	 * @return the class of the piece associated with that character or
	 *         {@code null}
	 *         if no piece is associated with the given character
	 */
	public static Class<? extends Piece> fromFirstChar(char firstChar) {
		switch (Character.toLowerCase(firstChar)) {
			case 'k':
				return King.class;
			case 'q':
				return Queen.class;
			case 'r':
				return Rook.class;
			case 'n':
				return Knight.class;
			case 'b':
				return Bishop.class;
			case 'p':
				return Pawn.class;
			default:
				return null;
		}
	}

	/**
	 * @return the {@link Color} of this {@link Piece}
	 */
	public Color getColor() { return color; }

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

		/**
		 * Represents the color of the white pieces on a board.
		 */
		WHITE,

		/**
		 * Represents the color of the black pieces on a board.
		 */
		BLACK;

		/**
		 * @param c the first character of a color's name
		 * @return {@code WHITE} if the character is {@code w} or {@code W},
		 *         else
		 *         {@code BLACK}
		 */
		public static Color fromFirstChar(char c) {
			return Character.toLowerCase(c) == 'w' ? WHITE : BLACK;
		}

		/**
		 * @return the first character (lower case) of this color
		 */
		public char firstChar() {
			return this == WHITE ? 'w' : 'b';
		}

		/**
		 * @return the opposite of this color
		 */
		public Color opposite() {
			return this == WHITE ? BLACK : WHITE;
		}
	}
}