chessfriend/core/src/pieces.rs

// Eryn Wells <eryn@erynwells.me>

use crate::{errors::TryFromCharError, try_from_string, Color, Square};
use std::{array, fmt, slice};

trait _Shape {
    fn symbol(&self) -> char;
    fn index(&self) -> usize;
}

macro_rules! shape {
    ($name:ident, $index:expr, $symbol:expr) => {
        struct $name;

        impl _Shape for $name {
            fn symbol(&self) -> char {
                $symbol
            }

            fn index(&self) -> usize {
                $index
            }
        }
    };
}

shape!(Pawn, 0, 'P');
shape!(Knight, 1, 'K');
shape!(Bishop, 2, 'B');
shape!(Rook, 3, 'R');
shape!(Queen, 4, 'Q');
shape!(King, 5, 'K');

#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum Shape {
    Pawn = 0,
    Knight = 1,
    Bishop = 2,
    Rook = 3,
    Queen = 4,
    King = 5,
}

impl Shape {
    /// Number of piece shapes
    pub const NUM: usize = 6;

    /// A slice of all piece shapes
    pub const ALL: [Shape; Self::NUM] = [
        Shape::Pawn,
        Shape::Knight,
        Shape::Bishop,
        Shape::Rook,
        Shape::Queen,
        Shape::King,
    ];

    pub fn iter() -> slice::Iter<'static, Self> {
        Shape::ALL.iter()
    }

    pub fn into_iter() -> array::IntoIter<Self, { Self::NUM }> {
        Shape::ALL.into_iter()
    }

    /// An iterator over the shapes that a pawn can promote to
    pub fn promotable() -> slice::Iter<'static, Shape> {
        const PROMOTABLE_SHAPES: [Shape; 4] =
            [Shape::Queen, Shape::Rook, Shape::Bishop, Shape::Knight];

        PROMOTABLE_SHAPES.iter()
    }

    const fn to_ascii(self) -> char {
        match self {
            Shape::Pawn => 'P',
            Shape::Knight => 'N',
            Shape::Bishop => 'B',
            Shape::Rook => 'R',
            Shape::Queen => 'Q',
            Shape::King => 'K',
        }
    }
}

impl TryFrom<char> for Shape {
    type Error = TryFromCharError;

    fn try_from(value: char) -> Result<Self, Self::Error> {
        match value {
            'P' | 'p' => Ok(Shape::Pawn),
            'N' | 'n' => Ok(Shape::Knight),
            'B' | 'b' => Ok(Shape::Bishop),
            'R' | 'r' => Ok(Shape::Rook),
            'Q' | 'q' => Ok(Shape::Queen),
            'K' | 'k' => Ok(Shape::King),
            _ => Err(TryFromCharError),
        }
    }
}

try_from_string!(Shape);

impl From<&Shape> for char {
    fn from(shape: &Shape) -> char {
        char::from(*shape)
    }
}

impl From<Shape> for char {
    fn from(shape: Shape) -> char {
        shape.to_ascii()
    }
}

impl fmt::Display for Shape {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let self_char: char = self.into();
        write!(f, "{self_char}")
    }
}

#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct Piece {
    pub color: Color,
    pub shape: Shape,
}

macro_rules! piece_constructor {
    ($func_name:ident, $type:tt) => {
        #[must_use]
        pub fn $func_name(color: Color) -> Piece {
            Piece {
                color,
                shape: Shape::$type,
            }
        }
    };
}

macro_rules! is_shape {
    ($func_name:ident, $shape:ident) => {
        #[must_use]
        pub fn $func_name(&self) -> bool {
            self.shape == Shape::$shape
        }
    };
}

impl Piece {
    #[must_use]
    pub fn new(color: Color, shape: Shape) -> Piece {
        Piece { color, shape }
    }

    piece_constructor!(pawn, Pawn);
    piece_constructor!(knight, Knight);
    piece_constructor!(bishop, Bishop);
    piece_constructor!(rook, Rook);
    piece_constructor!(queen, Queen);
    piece_constructor!(king, King);

    is_shape!(is_pawn, Pawn);
    is_shape!(is_knight, Knight);
    is_shape!(is_bishop, Bishop);
    is_shape!(is_rook, Rook);
    is_shape!(is_queen, Queen);
    is_shape!(is_king, King);

    #[must_use]
    pub fn to_ascii(self) -> char {
        let ch = self.shape.to_ascii();
        match self.color {
            Color::White => ch,
            Color::Black => ch.to_ascii_lowercase(),
        }
    }

    #[must_use]
    fn to_unicode(self) -> char {
        match (self.color, self.shape) {
            (Color::Black, Shape::Pawn) => '♟',
            (Color::Black, Shape::Knight) => '♞',
            (Color::Black, Shape::Bishop) => '♝',
            (Color::Black, Shape::Rook) => '♜',
            (Color::Black, Shape::Queen) => '♛',
            (Color::Black, Shape::King) => '♚',
            (Color::White, Shape::Pawn) => '♙',
            (Color::White, Shape::Knight) => '♘',
            (Color::White, Shape::Bishop) => '♗',
            (Color::White, Shape::Rook) => '♖',
            (Color::White, Shape::Queen) => '♕',
            (Color::White, Shape::King) => '♔',
        }
    }
}

impl fmt::Display for Piece {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.to_unicode())
    }
}

impl From<PlacedPiece> for Piece {
    fn from(value: PlacedPiece) -> Self {
        value.piece
    }
}

impl From<&PlacedPiece> for Piece {
    fn from(value: &PlacedPiece) -> Self {
        value.piece
    }
}

#[deprecated]
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct PlacedPiece {
    pub piece: Piece,
    pub square: Square,
}

macro_rules! is_shape {
    ($func_name:ident, $shape:ident) => {
        #[must_use]
        pub fn $func_name(&self) -> bool {
            self.piece().shape == Shape::$shape
        }
    };
}

impl PlacedPiece {
    #[must_use]
    pub const fn new(piece: Piece, square: Square) -> PlacedPiece {
        PlacedPiece { piece, square }
    }

    /// The [Piece] itself
    #[inline]
    #[must_use]
    pub fn piece(&self) -> Piece {
        self.piece
    }

    is_shape!(is_pawn, Pawn);
    is_shape!(is_knight, Knight);
    is_shape!(is_bishop, Bishop);
    is_shape!(is_rook, Rook);
    is_shape!(is_queen, Queen);
    is_shape!(is_king, King);

    #[must_use]
    pub fn is_kingside_rook(&self) -> bool {
        self.is_rook()
            && match self.piece.color {
                Color::White => self.square == Square::H1,
                Color::Black => self.square == Square::H8,
            }
    }

    #[must_use]
    pub fn is_queenside_rook(&self) -> bool {
        self.is_rook()
            && match self.piece.color {
                Color::White => self.square == Square::A1,
                Color::Black => self.square == Square::A8,
            }
    }
}

impl fmt::Display for PlacedPiece {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}{}", self.piece, self.square)
    }
}

impl From<(&Square, &Piece)> for PlacedPiece {
    fn from(value: (&Square, &Piece)) -> Self {
        PlacedPiece::new(*value.1, *value.0)
    }
}

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

    #[test]
    fn shape_try_from() {
        assert_eq!(Shape::try_from('p'), Ok(Shape::Pawn));
        assert_eq!(Shape::try_from("p"), Ok(Shape::Pawn));
    }

    #[test]
    fn shape_into_char() {
        assert_eq!(<Shape as Into<char>>::into(Shape::Pawn), 'P');
    }
}