Add FEN board parsing
Unfortunately, given that I *don't* want to expose all the `ChessBoard` fields to the rest of the crate, this implementation will have to live alongside its module instead of inside `crate::fen`...
This commit is contained in:
parent
3cd2601f07
commit
c1419f0e44
|
@ -1,3 +1,5 @@
|
||||||
|
use crate::fen::{FenError, FromFen};
|
||||||
|
|
||||||
use super::{Bitboard, CastleRights, Color, File, Move, Piece, Rank, Square};
|
use super::{Bitboard, CastleRights, Color, File, Move, Piece, Rank, Square};
|
||||||
|
|
||||||
/// Represent an on-going chess game.
|
/// Represent an on-going chess game.
|
||||||
|
@ -303,8 +305,103 @@ impl Default for ChessBoard {
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
/// Return a [ChessBoard] from the given FEN string.
|
||||||
|
impl FromFen for ChessBoard {
|
||||||
|
type Err = FenError;
|
||||||
|
|
||||||
|
fn from_fen(s: &str) -> Result<Self, Self::Err> {
|
||||||
|
let mut split = s.split_ascii_whitespace();
|
||||||
|
|
||||||
|
let piece_placement = split.next().ok_or(FenError::InvalidFen)?;
|
||||||
|
let side_to_move = split.next().ok_or(FenError::InvalidFen)?;
|
||||||
|
let castling_rights = split.next().ok_or(FenError::InvalidFen)?;
|
||||||
|
let en_passant_square = split.next().ok_or(FenError::InvalidFen)?;
|
||||||
|
let half_move_clock = split.next().ok_or(FenError::InvalidFen)?;
|
||||||
|
let full_move_counter = split.next().ok_or(FenError::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(|_| FenError::InvalidFen)?;
|
||||||
|
let full_move_counter = full_move_counter
|
||||||
|
.parse::<u32>()
|
||||||
|
.map_err(|_| FenError::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(FenError::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(FenError::InvalidFen);
|
||||||
|
}
|
||||||
|
}
|
||||||
|
// We haven't read exactly 8 ranks
|
||||||
|
if rank != 0 {
|
||||||
|
return Err(FenError::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(FenError::InvalidPosition);
|
||||||
|
}
|
||||||
|
|
||||||
|
Ok(res)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
#[cfg(test)]
|
#[cfg(test)]
|
||||||
mod test {
|
mod test {
|
||||||
|
use crate::board::MoveBuilder;
|
||||||
|
|
||||||
use super::*;
|
use super::*;
|
||||||
|
|
||||||
#[test]
|
#[test]
|
||||||
|
@ -516,4 +613,76 @@ mod test {
|
||||||
};
|
};
|
||||||
assert!(!position.is_valid());
|
assert!(!position.is_valid());
|
||||||
}
|
}
|
||||||
|
|
||||||
|
#[test]
|
||||||
|
fn fen_default_position() {
|
||||||
|
let default_position = ChessBoard::default();
|
||||||
|
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::default();
|
||||||
|
position.do_move(
|
||||||
|
MoveBuilder {
|
||||||
|
piece: Piece::Pawn,
|
||||||
|
start: Square::E2,
|
||||||
|
destination: Square::E4,
|
||||||
|
capture: None,
|
||||||
|
promotion: None,
|
||||||
|
en_passant: false,
|
||||||
|
double_step: true,
|
||||||
|
castling: false,
|
||||||
|
}
|
||||||
|
.into(),
|
||||||
|
);
|
||||||
|
assert_eq!(
|
||||||
|
ChessBoard::from_fen("rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1")
|
||||||
|
.unwrap(),
|
||||||
|
position
|
||||||
|
);
|
||||||
|
// And now c5
|
||||||
|
position.do_move(
|
||||||
|
MoveBuilder {
|
||||||
|
piece: Piece::Pawn,
|
||||||
|
start: Square::C7,
|
||||||
|
destination: Square::C5,
|
||||||
|
capture: None,
|
||||||
|
promotion: None,
|
||||||
|
en_passant: false,
|
||||||
|
double_step: true,
|
||||||
|
castling: false,
|
||||||
|
}
|
||||||
|
.into(),
|
||||||
|
);
|
||||||
|
assert_eq!(
|
||||||
|
ChessBoard::from_fen("rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq c6 0 2")
|
||||||
|
.unwrap(),
|
||||||
|
position
|
||||||
|
);
|
||||||
|
// Finally, Nf3
|
||||||
|
position.do_move(
|
||||||
|
MoveBuilder {
|
||||||
|
piece: Piece::Knight,
|
||||||
|
start: Square::G1,
|
||||||
|
destination: Square::F3,
|
||||||
|
capture: None,
|
||||||
|
promotion: None,
|
||||||
|
en_passant: false,
|
||||||
|
double_step: false,
|
||||||
|
castling: false,
|
||||||
|
}
|
||||||
|
.into(),
|
||||||
|
);
|
||||||
|
assert_eq!(
|
||||||
|
ChessBoard::from_fen("rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2 ")
|
||||||
|
.unwrap(),
|
||||||
|
position
|
||||||
|
);
|
||||||
|
}
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in a new issue