zeal/src/board.rs

use std::fmt;
use u64 as Bitboard;

use crate::attack::{
    get_bishop_attacks, get_king_attacks, get_knight_attacks, get_pawn_attacks, get_queen_attacks,
    get_rook_attacks,
};
use crate::game::State;

#[derive(Debug, PartialEq, Eq)]
pub struct Board {
    pub white_pieces: [Piece; 6],
    pub black_pieces: [Piece; 6],
    pub state: State,
}

impl Board {
    pub const fn new() -> Self {
        Self {
            white_pieces: [
                Piece::new(0xff00, Kind::Pawn, Color::White),
                Piece::new(0x42, Kind::Knight, Color::White),
                Piece::new(0x24, Kind::Bishop, Color::White),
                Piece::new(0x81, Kind::Rook, Color::White),
                Piece::new(0x8, Kind::Queen, Color::White),
                Piece::new(0x10, Kind::King, Color::White),
            ],
            black_pieces: [
                Piece::new(0xff000000000000, Kind::Pawn, Color::Black),
                Piece::new(0x4200000000000000, Kind::Knight, Color::Black),
                Piece::new(0x2400000000000000, Kind::Bishop, Color::Black),
                Piece::new(0x8100000000000000, Kind::Rook, Color::Black),
                Piece::new(0x800000000000000, Kind::Queen, Color::Black),
                Piece::new(0x1000000000000000, Kind::King, Color::Black),
            ],
            state: State::new(),
        }
    }

    pub const fn empty_board() -> Self {
        Self {
            white_pieces: [
                Piece::new(0x0, Kind::Pawn, Color::White),
                Piece::new(0x0, Kind::Knight, Color::White),
                Piece::new(0x0, Kind::Bishop, Color::White),
                Piece::new(0x0, Kind::Rook, Color::White),
                Piece::new(0x0, Kind::Queen, Color::White),
                Piece::new(0x0, Kind::King, Color::White),
            ],
            black_pieces: [
                Piece::new(0x0, Kind::Pawn, Color::Black),
                Piece::new(0x0, Kind::Knight, Color::Black),
                Piece::new(0x0, Kind::Bishop, Color::Black),
                Piece::new(0x0, Kind::Rook, Color::Black),
                Piece::new(0x0, Kind::Queen, Color::Black),
                Piece::new(0x0, Kind::King, Color::Black),
            ],
            state: State::new(),
        }
    }

    pub fn set_piece(&mut self, piece: Piece) {
        match piece.color {
            Color::Black => self.black_pieces[piece.kind.idx()].bitboard |= piece.bitboard,
            Color::White => self.white_pieces[piece.kind.idx()].bitboard |= piece.bitboard,
        };
    }

    pub fn set_state(&mut self, state: State) {
        self.state = state;
    }

    pub fn get_white_occupancies(&self) -> Bitboard {
        self.white_pieces.iter().fold(0, |acc, p| p.bitboard | acc)
    }

    pub fn get_black_occupancies(&self) -> Bitboard {
        self.black_pieces.iter().fold(0, |acc, p| p.bitboard | acc)
    }

    pub fn get_all_occupancies(&self) -> Bitboard {
        self.get_white_occupancies() | self.get_black_occupancies()
    }

    pub fn is_attacked(&self, sq: usize, opponent_color: Color) -> bool {
        let all_occupancies = self.get_all_occupancies();
        let enemy = match opponent_color {
            Color::Black => &self.black_pieces,
            Color::White => &self.white_pieces,
        };

        enemy[Kind::Pawn.idx()].bitboard & get_pawn_attacks(sq, opponent_color) != 0
            || enemy[Kind::Knight.idx()].bitboard & get_knight_attacks(sq) != 0
            || enemy[Kind::Bishop.idx()].bitboard & get_bishop_attacks(all_occupancies, sq) != 0
            || enemy[Kind::Rook.idx()].bitboard & get_rook_attacks(all_occupancies, sq) != 0
            || enemy[Kind::Queen.idx()].bitboard & get_queen_attacks(all_occupancies, sq) != 0
            || enemy[Kind::King.idx()].bitboard & get_king_attacks(sq) != 0
    }
}

impl Default for Board {
    fn default() -> Self {
        Self::new()
    }
}

impl fmt::Display for Board {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for piece in &self.white_pieces {
            writeln!(
                f,
                "Color: {:?}\nKind: {:?}\n{piece}",
                piece.color, piece.kind
            )?;
        }
        writeln!(f)?;
        for piece in &self.black_pieces {
            writeln!(
                f,
                "Color: {:?}\nKind: {:?}\n{piece}",
                piece.color, piece.kind
            )?;
        }
        writeln!(f)
    }
}

#[derive(Debug, PartialEq, Eq)]
pub struct Piece {
    pub bitboard: Bitboard,
    pub kind: Kind,
    pub color: Color,
}

impl Piece {
    pub const fn new(bitboard: Bitboard, kind: Kind, color: Color) -> Self {
        Self {
            bitboard,
            kind,
            color,
        }
    }
}

impl fmt::Display for Piece {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for rank in (0..8).rev() {
            for file in 0..8 {
                let square = 1 << (rank * 8 + file);
                let position = if square & self.bitboard != 0x0 { 1 } else { 0 };
                write!(f, "{} ", position)?;
            }
            writeln!(f)?;
        }
        writeln!(f)
    }
}

#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum Kind {
    Pawn,
    Knight,
    Bishop,
    Rook,
    Queen,
    King,
}

impl Kind {
    fn idx(&self) -> usize {
        *self as usize
    }
}

#[derive(Debug, PartialEq, Eq)]
pub enum Color {
    White,
    Black,
}

#[cfg(test)]
mod tests {
    use crate::{attack::init_attacks, fen::from_fen};

    use super::*;

    const FEN_EXAMPLE: [&str; 1] = [
        "8/6P1/4n2b/1p6/1Kp5/6n1/4b3/1k6 w - - 0 1",
    ];

    #[test]
    fn test_get_all_occupancies() -> Result<(), String> {
        let new_game = from_fen(FEN_EXAMPLE[0])?;
        assert_eq!(new_game.board.get_all_occupancies(), 0x40900206401002);

        Ok(())
    }

    #[test]
    fn test_is_attacked() -> Result<(), String> {
        let new_game = from_fen(FEN_EXAMPLE[0])?;
        init_attacks();
        assert!(new_game.board.is_attacked(54, Color::Black));

        Ok(())
    }
}