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use crate::chessboard::castling_rights::CastlingRights;
use crate::chessboard::chessboard::BuilderConversionError;
use crate::defs::*;
use crate::{ChessBoard, ZobristHash};
use thiserror::Error;
/// The [`BoardBuilderError`] enum is the error type produced by the [`BoardBuilder`].
#[derive(Error, Debug, Copy, Clone, Eq, PartialEq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum BoardBuilderError {
#[error("tried to insert two kings of the same color")]
TwoKings,
#[error("tried to insert a pawn on its last rank")]
PawnOnLast,
#[error("tried to insert multiple pieces on the same square")]
TwoPieces,
#[error("tried to set the turn, but the turn was already set")]
TurnAlreadySet,
#[error("tried to set an already set castling right")]
CastleRightAlreadySet,
#[error("tried to set the en passant square, but it was already set")]
EnPassantAlreadySet,
}
/// The [`BoardBuilder`] struct helps construct a [`ChessBoard`].
#[derive(Clone, Eq, PartialEq, Debug)]
pub struct BoardBuilder {
pub(super) piece_map: [Option<Piece>; 64],
pub(super) piece_bbs: [BitBoard; 6],
pub(super) color_bbs: [BitBoard; 2],
pub(super) turn: Option<Color>,
pub(super) castling_rights: CastlingRights,
pub(super) en_passant_square: Option<Square>,
pub(super) hash: ZobristHash,
}
impl BoardBuilder {
/// Creates a new [`BoardBuilder`] object.
#[inline]
pub fn new() -> Self {
Self {
piece_map: [None; 64],
piece_bbs: [BitBoard::EMPTY; 6],
color_bbs: [BitBoard::EMPTY; 2],
turn: None,
castling_rights: CastlingRights::new(),
en_passant_square: None,
hash: ZobristHash::new(),
}
}
/// Adds a piece to the [`BoardBuilder`].
///
/// # Examples
/// ```
/// use rchess::{BoardBuilder, Color, Piece, PieceType, Square};
///
/// // Create a new board builder with two kings.
/// let builder = BoardBuilder::new()
/// .piece(Square::A1, Piece::WHITE_KING).unwrap()
/// .piece(Square::H8, Piece::BLACK_KING).unwrap();
/// ```
#[inline]
pub fn piece(
mut self,
square: Square,
piece: impl Into<Piece>,
) -> Result<Self, BoardBuilderError> {
let piece = piece.into();
if piece.kind == PieceType::King {
if !(self.piece_bbs[PieceType::King.index()] & self.color_bbs[piece.color.index()])
.is_empty()
{
return Err(BoardBuilderError::TwoKings);
}
} else if piece.kind == PieceType::Pawn {
match piece.color {
Color::White => {
if square.rank() == Rank::Eighth {
return Err(BoardBuilderError::PawnOnLast);
}
}
Color::Black => {
if square.rank() == Rank::First {
return Err(BoardBuilderError::PawnOnLast);
}
}
}
}
if self.piece_map[square.index()].is_some() {
return Err(BoardBuilderError::TwoPieces);
}
self.piece_map[square.index()] = Some(piece);
self.piece_bbs[piece.kind.index()] |= square.bitboard();
self.color_bbs[piece.color.index()] |= square.bitboard();
self.hash.piece(square, piece);
Ok(self)
}
/// Sets the turn of the [`BoardBuilder`].
///
/// # Examples
/// ```
/// use rchess::{BoardBuilder, Color};
///
/// // Create a board builder with the turn set to black.
/// let builder = BoardBuilder::new()
/// .turn(Color::Black).unwrap();
/// ```
#[inline]
pub fn turn(mut self, color: Color) -> Result<Self, BoardBuilderError> {
if self.turn.is_some() {
return Err(BoardBuilderError::TurnAlreadySet);
}
self.turn = Some(color);
if color == Color::Black {
self.hash.toggle_turn();
}
Ok(self)
}
/// Adds a castling right to the [`BoardBuilder`].
///
/// # Examples
/// ```
/// use rchess::{BoardBuilder, CastleSide, Color};
///
/// // Create a board builder all castling rights.
/// let builder = BoardBuilder::new()
/// .castle_right(CastleSide::Kingside, Color::White).unwrap()
/// .castle_right(CastleSide::Queenside, Color::White).unwrap()
/// .castle_right(CastleSide::Kingside, Color::Black).unwrap()
/// .castle_right(CastleSide::Queenside, Color::Black).unwrap();
/// ```
#[inline]
pub fn castle_right(
mut self,
side: CastleSide,
color: Color,
) -> Result<Self, BoardBuilderError> {
if self.castling_rights.is_set(side, color) {
return Err(BoardBuilderError::CastleRightAlreadySet);
}
self.castling_rights.set(side, color);
self.hash.castle_right(side, color);
Ok(self)
}
/// Sets the en passant square of the [`BoardBuilder`].
///
/// # Examples
/// ```
/// use rchess::{BoardBuilder,Square};
///
/// // Create a board builder with an en passant square set.
/// let builder = BoardBuilder::new()
/// .en_passant(Square::E3).unwrap();
/// ```
#[inline]
pub fn en_passant(mut self, square: Square) -> Result<Self, BoardBuilderError> {
if self.en_passant_square.is_some() {
return Err(BoardBuilderError::EnPassantAlreadySet);
}
self.en_passant_square = Some(square);
self.hash.ep(square);
Ok(self)
}
/// Converts the [`BoardBuilder`] into a [`ChessBoard`].
///
/// # Examples
/// ```no_run
/// use rchess::{BoardBuilder, Color, Piece, Square};
///
/// // Create a new chess board with two kings with black to move.
/// let builder = BoardBuilder::new()
/// .piece(Square::A1, Piece::WHITE_KING).unwrap()
/// .piece(Square::H8, Piece::BLACK_KING).unwrap()
/// .turn(Color::Black).unwrap()
/// .finish().unwrap();
/// ```
#[inline]
pub fn finish(self) -> Result<ChessBoard, BuilderConversionError> {
ChessBoard::from_builder(self)
}
}