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use anyhow::Context;
use crate::bitboard::BitBoard;
use crate::game::pieces::{Color, Pieces};
use crate::game::position::Position;
use crate::game::{Board, BoardSide};
pub const DEFAULT_FEN: &str = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
impl Board {
pub fn from_fen(fen: &str) -> anyhow::Result<Self> {
if fen == "startpos" {
return Self::from_fen(DEFAULT_FEN);
}
let mut fen_split = fen.split_whitespace();
let piece_placement = fen_split.next().with_context(|| "no piece placement")?;
let ranks: Vec<&str> = piece_placement.split('/').collect();
if ranks.len() != 8 {
return Err(anyhow::Error::msg("piece placement does not have 8 ranks"));
}
let mut pieces = Vec::with_capacity(64);
for (rank, rank_pieces) in ranks.into_iter().enumerate() {
let rank = (7 - rank) as u8;
let mut file: u8 = 0;
for piece in rank_pieces.chars() {
if let Some(skip) = piece.to_digit(10) {
file += skip as u8;
} else {
let color = if piece.is_uppercase() {
Color::White
} else {
Color::Black
};
let piece = match piece.to_lowercase().next() {
Some('p') => Pieces::Pawn(color, (file, rank).into()),
Some('r') => Pieces::Rook(color, (file, rank).into()),
Some('n') => Pieces::Knight(color, (file, rank).into()),
Some('b') => Pieces::Bishop(color, (file, rank).into()),
Some('q') => Pieces::Queen(color, (file, rank).into()),
Some('k') => Pieces::King(color, (file, rank).into()),
_ => return Err(anyhow::Error::msg("invalid piece descriptor")),
};
pieces.push(piece);
file += 1;
}
}
if file != 8 {
return Err(anyhow::Error::msg("incomplete rank pieces"));
}
}
let active_color = if fen_split.next().with_context(|| "no active color")? == "w" {
Color::White
} else {
Color::Black
};
let castling_availability = fen_split
.next()
.with_context(|| "no castling availability")?;
let white_queenside_castle = castling_availability.contains('Q');
let white_kingside_castle = castling_availability.contains('K');
let black_queenside_castle = castling_availability.contains('q');
let black_kingside_castle = castling_availability.contains('k');
let en_passant_target = fen_split
.next()
.with_context(|| "no en passant target square")?;
let en_passant_target: Option<(Position, Color)> = match en_passant_target {
"-" => None,
p => {
let pos =
Position::from_notation(p).with_context(|| "invalid en passant target")?;
let color = if pos.rank_y == 2 {
Color::White
} else if pos.rank_y == 5 {
Color::Black
} else {
return Err(anyhow::Error::msg("impossible en passant target"));
};
Some((pos, color))
}
};
let half_move_clock = fen_split.next().with_context(|| "no half-move clock")?;
let full_move_clock = fen_split.next().with_context(|| "no full-move clock")?;
let white = BoardSide::new(Color::White, |side| {
for piece in pieces.iter().filter(|p| p.is_white()) {
match piece {
Pieces::Pawn(_, position) => side.pawns |= BitBoard::from(*position),
Pieces::Rook(_, position) => side.rooks |= BitBoard::from(*position),
Pieces::Knight(_, position) => side.knights |= BitBoard::from(*position),
Pieces::Bishop(_, position) => side.bishops |= BitBoard::from(*position),
Pieces::Queen(_, position) => side.queens |= BitBoard::from(*position),
Pieces::King(_, position) => side.king |= BitBoard::from(*position),
}
}
if white_queenside_castle {
side.unmoved_rooks |= BitBoard::from_position("a1".into());
}
if white_kingside_castle {
side.unmoved_rooks |= BitBoard::from_position("h1".into());
}
if let Some((pos, color)) = en_passant_target {
if color == Color::White {
side.en_passant_target |= BitBoard::from(pos.forwards(color, 1));
}
}
});
let black = BoardSide::new(Color::Black, |side| {
for piece in pieces.iter().filter(|p| p.is_black()) {
match piece {
Pieces::Pawn(_, position) => side.pawns |= BitBoard::from(*position),
Pieces::Rook(_, position) => side.rooks |= BitBoard::from(*position),
Pieces::Knight(_, position) => side.knights |= BitBoard::from(*position),
Pieces::Bishop(_, position) => side.bishops |= BitBoard::from(*position),
Pieces::Queen(_, position) => side.queens |= BitBoard::from(*position),
Pieces::King(_, position) => side.king |= BitBoard::from(*position),
}
}
if black_queenside_castle {
side.unmoved_rooks |= BitBoard::from_position("a8".into());
}
if black_kingside_castle {
side.unmoved_rooks |= BitBoard::from_position("h8".into());
}
if let Some((pos, color)) = en_passant_target {
if color == Color::Black {
side.en_passant_target |= BitBoard::from(pos.forwards(color, 1));
}
}
});
Ok(Self { white, black })
}
pub fn to_fen(&self) -> String {
unimplemented!()
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_default_fen() {
let parsed = Board::from_fen(DEFAULT_FEN).expect("failed to parse FEN");
assert_eq!(parsed, Board::default());
}
}