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Add FEN board parsing

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This commit is contained in:
Bruno BELANYI 2022-07-28 21:38:50 +02:00
parent fb0e289fa0
commit 0cefb05017
1 changed files with 197 additions and 0 deletions
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197
src/board/chess_board.rs
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@ -272,9 +272,103 @@ impl ChessBoard {
}
}
/// Return a [ChessBoard] from the given FEN string.
impl FromFen for ChessBoard {
type Err = Error;
fn from_fen(s: &str) -> Result<Self, Self::Err> {
let mut split = s.split_ascii_whitespace();
let piece_placement = split.next().ok_or(Error::InvalidFen)?;
let side_to_move = split.next().ok_or(Error::InvalidFen)?;
let castling_rights = split.next().ok_or(Error::InvalidFen)?;
let en_passant_square = split.next().ok_or(Error::InvalidFen)?;
let half_move_clock = split.next().ok_or(Error::InvalidFen)?;
let full_move_counter = split.next().ok_or(Error::InvalidFen)?;
let castle_rights = <[CastleRights; 2]>::from_fen(castling_rights)?;
let side = Color::from_fen(side_to_move)?;
let en_passant = Option::<Square>::from_fen(en_passant_square)?;
let half_move_clock = half_move_clock
.parse::<u8>()
.map_err(|_| Error::InvalidFen)?;
let full_move_counter = full_move_counter
.parse::<u32>()
.map_err(|_| Error::InvalidFen)?;
let total_plies = (full_move_counter - 1) * 2 + if side == Color::White { 0 } else { 1 };
let (piece_occupancy, color_occupancy, combined_occupancy) = {
let (mut pieces, mut colors, mut combined) =
([Bitboard::EMPTY; 6], [Bitboard::EMPTY; 2], Bitboard::EMPTY);
let mut rank: usize = 8;
for rank_str in piece_placement.split('/') {
rank -= 1;
let mut file: usize = 0;
for c in rank_str.chars() {
let color = if c.is_uppercase() {
Color::White
} else {
Color::Black
};
let piece = match c {
digit @ '1'..='8' => {
// Unwrap is fine since this arm is only matched by digits
file += digit.to_digit(10).unwrap() as usize;
continue;
}
_ => Piece::from_fen(&c.to_string())?,
};
let (piece_board, color_board) =
(&mut pieces[piece.index()], &mut colors[color.index()]);
// Only need to worry about underflow since those are `usize` values.
if file >= 8 || rank >= 8 {
return Err(Error::InvalidFen);
};
let square = Square::new(File::from_index(file), Rank::from_index(rank));
*piece_board |= square;
*color_board |= square;
combined |= square;
file += 1;
}
// We haven't read exactly 8 files.
if file != 8 {
return Err(Error::InvalidFen);
}
}
// We haven't read exactly 8 ranks
if rank != 0 {
return Err(Error::InvalidFen);
}
(pieces, colors, combined)
};
let res = Self {
piece_occupancy,
color_occupancy,
combined_occupancy,
castle_rights,
en_passant,
half_move_clock,
total_plies,
side,
};
if !res.is_valid() {
return Err(Error::InvalidPosition);
}
Ok(res)
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::board::MoveBuilder;
#[test]
fn valid() {
@ -513,4 +607,107 @@ mod test {
};
assert!(!position.is_valid());
}
#[test]
fn fen_default_position() {
let default_position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Square::D1 | Square::D8,
// Rook
Square::A1 | Square::A8 | Square::H1 | Square::H8,
// Bishop
Square::C1 | Square::C8 | Square::F1 | Square::F8,
// Knight
Square::B1 | Square::B8 | Square::G1 | Square::G8,
// Pawn
Rank::Second.into_bitboard() | Rank::Seventh.into_bitboard(),
],
color_occupancy: [
Rank::First.into_bitboard() | Rank::Second.into_bitboard(),
Rank::Seventh.into_bitboard() | Rank::Eighth.into_bitboard(),
],
combined_occupancy: Rank::First.into_bitboard()
| Rank::Second.into_bitboard()
| Rank::Seventh.into_bitboard()
| Rank::Eighth.into_bitboard(),
castle_rights: [CastleRights::BothSides; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert_eq!(
ChessBoard::from_fen("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1")
.unwrap(),
default_position
);
}
#[test]
fn fen_en_passant() {
// Start from default position
let mut position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Square::D1 | Square::D8,
// Rook
Square::A1 | Square::A8 | Square::H1 | Square::H8,
// Bishop
Square::C1 | Square::C8 | Square::F1 | Square::F8,
// Knight
Square::B1 | Square::B8 | Square::G1 | Square::G8,
// Pawn
Rank::Second.into_bitboard() | Rank::Seventh.into_bitboard(),
],
color_occupancy: [
Rank::First.into_bitboard() | Rank::Second.into_bitboard(),
Rank::Seventh.into_bitboard() | Rank::Eighth.into_bitboard(),
],
combined_occupancy: Rank::First.into_bitboard()
| Rank::Second.into_bitboard()
| Rank::Seventh.into_bitboard()
| Rank::Eighth.into_bitboard(),
castle_rights: [CastleRights::BothSides; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
// Modify it to account for e4 move
position.xor(Color::White, Piece::Pawn, Square::E2 | Square::E4);
position.en_passant = Some(Square::E3);
position.total_plies = 1;
position.side = Color::Black;
assert_eq!(
ChessBoard::from_fen("rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1")
.unwrap(),
position
);
// And now c5
position.xor(Color::Black, Piece::Pawn, Square::C5 | Square::C7);
position.en_passant = Some(Square::C6);
position.total_plies = 2;
position.side = Color::White;
assert_eq!(
ChessBoard::from_fen("rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq c6 0 2")
.unwrap(),
position
);
// Finally, Nf3
position.xor(Color::White, Piece::Knight, Square::G1 | Square::F3);
position.en_passant = None;
position.total_plies = 3;
position.half_move_clock = 1;
position.side = Color::Black;
assert_eq!(
ChessBoard::from_fen("rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2 ")
.unwrap(),
position
);
}
}