use chessfriend_core::Color;

#[derive(Default)]
pub enum AdvanceHalfMove {
    Reset,
    #[default]
    Advance,
}

#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub struct Clock {
    /// The player who's turn it is to move.
    pub(crate) active_color: Color,

    /// The number of completed turns. A turn finishes when every player has moved.
    pub(crate) full_move_number: u16,

    /// The number of moves by all players since the last pawn advance or capture.
    pub(crate) half_move_number: u16,
}

impl Clock {
    #[must_use]
    pub fn active_color(&self) -> Color {
        self.active_color
    }

    #[must_use]
    pub fn full_move_number(&self) -> u16 {
        self.full_move_number
    }

    #[must_use]
    pub fn half_move_number(&self) -> u16 {
        self.half_move_number
    }

    pub fn advance(&mut self, advance_half_move: &AdvanceHalfMove) {
        let next_color = self.active_color.next();

        match self.active_color {
            Color::Black => self.full_move_number += 1,
            Color::White => {}
        }

        self.half_move_number = match advance_half_move {
            AdvanceHalfMove::Reset => 0,
            AdvanceHalfMove::Advance => self.half_move_number + 1,
        };

        self.active_color = next_color;
    }
}

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

    #[test]
    fn default_state() {
        let clock = Clock::default();
        assert_eq!(clock.active_color, Color::White);
        assert_eq!(clock.half_move_number, 0);
        assert_eq!(clock.full_move_number, 0);
    }

    #[test]
    fn advance() {
        let mut clock = Clock::default();

        clock.advance(&AdvanceHalfMove::default());
        assert_eq!(clock.active_color, Color::Black);
        assert_eq!(clock.half_move_number, 1);
        assert_eq!(clock.full_move_number, 0);

        clock.advance(&AdvanceHalfMove::default());
        assert_eq!(clock.active_color, Color::White);
        assert_eq!(clock.half_move_number, 2);
        assert_eq!(clock.full_move_number, 1);

        clock.advance(&AdvanceHalfMove::default());
        assert_eq!(clock.active_color, Color::Black);
        assert_eq!(clock.half_move_number, 3);
        assert_eq!(clock.full_move_number, 1);

        // The half move clock resets after a capture or pawn push.
        clock.advance(&AdvanceHalfMove::Reset);
        assert_eq!(clock.active_color, Color::White);
        assert_eq!(clock.half_move_number, 0);
        assert_eq!(clock.full_move_number, 2);
    }
}