chessfriend/board/src/move_generator/queen.rs

// Eryn Wells <eryn@erynwells.me>

use super::{move_generator_declaration, MoveGeneratorInternal, MoveSet};
use crate::{
    piece::{Color, Piece, PlacedPiece},
    MoveBuilder, Position,
};
use chessfriend_bitboard::BitBoard;
use chessfriend_core::Direction;

move_generator_declaration!(ClassicalMoveGenerator);

impl<'pos> MoveGeneratorInternal for ClassicalMoveGenerator<'pos> {
    fn piece(color: Color) -> Piece {
        Piece::queen(color)
    }

    fn move_set_for_piece(position: &Position, placed_piece: PlacedPiece) -> MoveSet {
        let piece = placed_piece.piece();
        let color = piece.color();
        let square = placed_piece.square();

        let blockers = position.occupied_squares();
        let empty_squares = !blockers;
        let friendly_pieces = position.bitboard_for_color(color);
        let opposing_pieces = position.bitboard_for_color(color.other());

        let mut all_moves = BitBoard::empty();

        macro_rules! update_moves_with_ray {
            ($direction:ident, $occupied_squares:tt) => {
                let ray = BitBoard::ray(square, Direction::$direction);
                if let Some(first_occupied_square) =
                    BitBoard::$occupied_squares(&(ray & blockers)).next()
                {
                    let remainder = BitBoard::ray(first_occupied_square, Direction::$direction);
                    let attack_ray = ray & !remainder;
                    all_moves |= attack_ray;
                } else {
                    all_moves |= ray;
                }
            };
        }

        update_moves_with_ray!(NorthWest, occupied_squares_trailing);
        update_moves_with_ray!(North, occupied_squares_trailing);
        update_moves_with_ray!(NorthEast, occupied_squares_trailing);
        update_moves_with_ray!(East, occupied_squares_trailing);
        update_moves_with_ray!(SouthEast, occupied_squares);
        update_moves_with_ray!(South, occupied_squares);
        update_moves_with_ray!(SouthWest, occupied_squares);
        update_moves_with_ray!(West, occupied_squares);

        let quiet_moves_bb = all_moves & (empty_squares | !friendly_pieces);
        let capture_moves_bb = all_moves & opposing_pieces;

        let map_to_move = |sq| MoveBuilder::new(*piece, square, sq).build();
        let quiet_moves = quiet_moves_bb.occupied_squares().map(map_to_move);
        let capture_moves = capture_moves_bb.occupied_squares().map(map_to_move);

        MoveSet::new(placed_piece)
            .quiet_moves(quiet_moves_bb, quiet_moves)
            .capture_moves(capture_moves_bb, capture_moves)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{piece, position, position::DiagramFormatter, Color};
    use chessfriend_bitboard::{bitboard, BitBoard};

    #[test]
    fn classical_single_queen_bitboard() {
        let pos = position![White Queen on B2];

        let generator = ClassicalMoveGenerator::new(&pos, Color::White);
        let bitboard = generator.bitboard();
        let expected = bitboard![
            A2, C2, D2, E2, F2, G2, H2, // Rank
            B1, B3, B4, B5, B6, B7, B8, // File
            A1, C3, D4, E5, F6, G7, H8, // Diagonal
            C1, A3 // Anti-diagonal
        ];

        assert_eq!(
            bitboard, expected,
            "actual:\n{}\nexpected:\n{}",
            bitboard, expected
        );
    }

    /// Test that a rook can move up to, but not onto, a friendly piece.
    #[test]
    fn classical_single_queen_with_same_color_blocker_bitboard() {
        let pos = position![
            White Queen on A1,
            White Knight on E1,
        ];

        println!("{}", DiagramFormatter::new(&pos));

        let generator = ClassicalMoveGenerator::new(&pos, Color::White);
        let bitboard = generator.bitboard();
        let expected = BitBoard::new(
            0b10000001_01000001_00100001_00010001_00001001_00000101_00000011_00001110,
        );

        assert_eq!(
            bitboard, expected,
            "actual:\n{}\nexpected:\n{}",
            bitboard, expected
        );
    }

    /// Test that a rook can move up to, and then capture, an enemy piece.
    #[test]
    fn classical_single_queen_with_opposing_color_blocker_bitboard() {
        let pos = position![
            White Queen on B2,
            Black Knight on E5,
        ];
        println!("{}", DiagramFormatter::new(&pos));

        let generator = ClassicalMoveGenerator::new(&pos, Color::White);

        assert_eq!(
            generator.bitboard(),
            bitboard![
                A2, C2, D2, E2, F2, G2, H2, // Rank
                B1, B3, B4, B5, B6, B7, B8, // File
                A1, C3, D4, E5, // Diagonal
                C1, A3 // Anti-diagonal
            ]
        );
    }

    #[test]
    fn classical_single_queen_in_center() {
        let pos = position![White Queen on D3];
        println!("{}", DiagramFormatter::new(&pos));

        let generator = ClassicalMoveGenerator::new(&pos, Color::White);

        assert_eq!(
            generator.bitboard(),
            bitboard![
                A3, B3, C3, E3, F3, G3, H3, // Rank
                D1, D2, D4, D5, D6, D7, D8, // File
                B1, C2, E4, F5, G6, H7, // Diagonal
                F1, E2, C4, B5, A6, // Anti-diagonal
            ]
        );
    }
}