chessfriend/moves/src/builder.rs

// Eryn Wells <eryn@erynwells.me>

use crate::{castle, Move};
use chessfriend_core::{PlacedPiece, Square};

pub trait Style {}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct Builder<S: Style> {
    style: S,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct Null;

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct Push {
    from: Option<Square>,
    to: Option<Square>,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct Capture {
    push: Push,
    capture: Option<Square>,
}

pub struct Castle {
    castle: castle::Castle,
}

impl Style for Null {}
impl Style for Push {}
impl Style for Capture {}
impl Style for Castle {}

impl Builder<Null> {
    pub fn new() -> Self {
        Self { style: Null }
    }

    pub fn piece(piece: &PlacedPiece) -> Builder<Push> {
        Builder {
            style: Push {
                from: Some(piece.square()),
                to: None,
            },
        }
    }

    pub fn castling(castle: castle::Castle) -> Builder<Castle> {
        Builder {
            style: Castle { castle },
        }
    }

    pub fn build(&self) -> Move {
        Move(0)
    }
}

impl Builder<Push> {
    pub fn from(mut self, square: Square) -> Self {
        self.style.from = Some(square);
        self
    }

    pub fn to(mut self, square: Square) -> Self {
        self.style.to = Some(square);
        self
    }

    pub fn capturing(self, square: Square) -> Builder<Capture> {
        Builder {
            style: Capture {
                push: self.style,
                capture: Some(square),
            },
        }
    }

    pub fn capturing_piece(self, piece: PlacedPiece) -> Builder<Capture> {
        Builder {
            style: Capture {
                push: self.style,
                capture: Some(piece.square()),
            },
        }
    }
}

impl Builder<Castle> {
    pub fn build(&self) -> Move {
        Move(self.style.into_bits())
    }
}

impl Castle {
    fn into_bits(&self) -> u16 {
        match self.castle {
            castle::Castle::KingSide => 0b10,
            castle::Castle::QueenSide => 0b11,
        }
    }
}