chessfriend/moves/src/castle.rs

// Eryn Wells <eryn@erynwells.me>

use chessfriend_bitboard::BitBoard;
use chessfriend_core::Square;

#[repr(u8)]
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum Castle {
    KingSide = 0,
    QueenSide = 1,
}

pub(crate) struct CastlingParameters {
    /// Origin squares of the king and rook.
    origin_squares: Squares,

    /// Target or destination squares for the king and rook.
    target_squares: Squares,

    /// The set of squares that must be clear of any pieces in order to perform this castle.
    clear_squares: BitBoard,

    /// The set of squares that must not be attacked in order to perform this castle.
    check_squares: BitBoard,
}

#[derive(Debug)]
pub(crate) struct Squares {
    pub king: Square,
    pub rook: Square,
}

impl Castle {
    pub const ALL: [Castle; 2] = [Castle::KingSide, Castle::QueenSide];

    /// Parameters for each castling move, organized by color and board-side.
    const PARAMETERS: [[CastlingParameters; 2]; 2] = [
        [
            CastlingParameters {
                origin_squares: Squares {
                    king: Square::E1,
                    rook: Square::H1,
                },
                target_squares: Squares {
                    king: Square::G1,
                    rook: Square::F1,
                },
                clear_squares: BitBoard::new(0b01100000),
                check_squares: BitBoard::new(0b01110000),
            },
            CastlingParameters {
                origin_squares: Squares {
                    king: Square::E1,
                    rook: Square::A1,
                },
                target_squares: Squares {
                    king: Square::C1,
                    rook: Square::D1,
                },
                clear_squares: BitBoard::new(0b00001110),
                check_squares: BitBoard::new(0b00011100),
            },
        ],
        [
            CastlingParameters {
                origin_squares: Squares {
                    king: Square::E8,
                    rook: Square::H8,
                },
                target_squares: Squares {
                    king: Square::G8,
                    rook: Square::F8,
                },
                clear_squares: BitBoard::new(0b01100000 << 8 * 7),
                check_squares: BitBoard::new(0b01110000 << 8 * 7),
            },
            CastlingParameters {
                origin_squares: Squares {
                    king: Square::E8,
                    rook: Square::A8,
                },
                target_squares: Squares {
                    king: Square::C8,
                    rook: Square::D8,
                },
                clear_squares: BitBoard::new(0b00001110 << 8 * 7),
                check_squares: BitBoard::new(0b00011100 << 8 * 7),
            },
        ],
    ];
}