chessfriend/board/src/position/flags.rs

// Eryn Wells <eryn@erynwells.me>

use super::position::BoardSide;
use crate::piece::Color;
use std::fmt;

#[derive(Clone, Copy, Eq, Hash, PartialEq)]
pub(super) struct Flags(u8);

impl Flags {
    #[inline]
    pub(super) fn player_has_right_to_castle_flag_offset(color: Color, side: BoardSide) -> u8 {
        ((color as u8) << 1) + side as u8
    }

    pub(super) fn player_has_right_to_castle(&self, color: Color, side: BoardSide) -> bool {
        (self.0 & (1 << Self::player_has_right_to_castle_flag_offset(color, side))) != 0
    }

    pub(super) fn set_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
        self.0 |= 1 << Self::player_has_right_to_castle_flag_offset(color, side);
    }

    pub(super) fn clear_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
        self.0 &= !(1 << Self::player_has_right_to_castle_flag_offset(color, side));
    }
}

impl fmt::Debug for Flags {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Flags({:08b})", self.0)
    }
}

impl Default for Flags {
    fn default() -> Self {
        Flags(0b00001111)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::piece::Color;

    #[test]
    fn castle_flags() {
        assert_eq!(
            Flags::player_has_right_to_castle_flag_offset(Color::White, BoardSide::King),
            0
        );
        assert_eq!(
            Flags::player_has_right_to_castle_flag_offset(Color::White, BoardSide::Queen),
            1
        );
        assert_eq!(
            Flags::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::King),
            2
        );
        assert_eq!(
            Flags::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::Queen),
            3
        );
    }

    #[test]
    fn defaults() {
        let mut flags: Flags = Default::default();
        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::King));
        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::Queen));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::King));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::Queen));

        flags.clear_player_has_right_to_castle_flag(Color::White, BoardSide::Queen);
        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::King));
        assert!(!flags.player_has_right_to_castle(Color::White, BoardSide::Queen));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::King));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::Queen));

        flags.set_player_has_right_to_castle_flag(Color::White, BoardSide::Queen);
        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::King));
        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::Queen));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::King));
        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::Queen));
    }
}