chessfriend/board/src/castle/rights.rs

use super::Castle;
use chessfriend_core::Color;
use std::fmt;

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

impl Rights {
    /// Returns `true` if the player has the right to castle on the given side
    /// of the board.
    ///
    /// A player retains the right to castle on a particular side of the board
    /// as long as they have not moved their king, or the rook on that side of
    /// the board.
    pub fn player_has_right_to_castle(self, color: Color, castle: Castle) -> bool {
        (self.0 & (1 << Self::_player_has_right_to_castle_flag_offset(color, castle))) != 0
    }

    pub fn set_player_has_right_to_castle_flag(&mut self, color: Color, castle: Castle) {
        self.0 |= 1 << Self::_player_has_right_to_castle_flag_offset(color, castle);
    }

    pub fn clear_player_has_right_to_castle_flag(&mut self, color: Color, castle: Castle) {
        self.0 &= !(1 << Self::_player_has_right_to_castle_flag_offset(color, castle));
    }

    pub fn clear_all(&mut self) {
        self.0 &= 0b1111_1100;
    }

    fn _player_has_right_to_castle_flag_offset(color: Color, castle: Castle) -> usize {
        ((color as usize) << 1) & castle as usize
    }
}

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

impl Default for Rights {
    fn default() -> Self {
        Self(0b0000_1111)
    }
}

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

    #[test]
    fn castling_rights() {
        assert_eq!(
            Rights::_player_has_right_to_castle_flag_offset(Color::White, Castle::KingSide),
            0
        );
        assert_eq!(
            Rights::_player_has_right_to_castle_flag_offset(Color::White, Castle::QueenSide),
            1
        );
        assert_eq!(
            Rights::_player_has_right_to_castle_flag_offset(Color::Black, Castle::KingSide),
            2
        );
        assert_eq!(
            Rights::_player_has_right_to_castle_flag_offset(Color::Black, Castle::QueenSide),
            3
        );
    }

    #[test]
    fn default_rights() {
        let mut rights = Rights::default();
        assert!(rights.player_has_right_to_castle(Color::White, Castle::KingSide));
        assert!(rights.player_has_right_to_castle(Color::White, Castle::QueenSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::KingSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::QueenSide));

        rights.clear_player_has_right_to_castle_flag(Color::White, Castle::QueenSide);
        assert!(rights.player_has_right_to_castle(Color::White, Castle::KingSide));
        assert!(!rights.player_has_right_to_castle(Color::White, Castle::QueenSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::KingSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::QueenSide));

        rights.set_player_has_right_to_castle_flag(Color::White, Castle::QueenSide);
        assert!(rights.player_has_right_to_castle(Color::White, Castle::KingSide));
        assert!(rights.player_has_right_to_castle(Color::White, Castle::QueenSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::KingSide));
        assert!(rights.player_has_right_to_castle(Color::Black, Castle::QueenSide));
    }
}