118 lines
3.3 KiB
Rust
118 lines
3.3 KiB
Rust
use crate::board::{CastleRights, Color, File, InvalidError, Piece, Rank, Square};
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/// A trait to mark items that can be converted from a FEN input.
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pub trait FromFen: Sized {
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type Err;
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fn from_fen(s: &str) -> Result<Self, Self::Err>;
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}
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/// A singular type for all errors that could happen during FEN parsing.
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#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
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pub enum FenError {
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/// Invalid FEN input.
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InvalidFen,
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/// Invalid chess position.
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InvalidPosition(InvalidError),
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}
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impl std::fmt::Display for FenError {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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match self {
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Self::InvalidFen => write!(f, "Invalid FEN input"),
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Self::InvalidPosition(err) => write!(f, "Invalid chess position: {}", err),
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}
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}
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}
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impl std::error::Error for FenError {}
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/// Allow converting a [InvalidError] into [FenError], for use with the '?' operator.
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impl From<InvalidError> for FenError {
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fn from(err: InvalidError) -> Self {
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Self::InvalidPosition(err)
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}
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}
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/// Convert the castling rights segment of a FEN string to an array of [CastleRights].
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impl FromFen for [CastleRights; 2] {
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type Err = FenError;
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fn from_fen(s: &str) -> Result<Self, Self::Err> {
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if s.len() > 4 {
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return Err(FenError::InvalidFen);
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}
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let mut res = [CastleRights::NoSide; 2];
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if s == "-" {
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return Ok(res);
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}
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for b in s.chars() {
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let color = if b.is_uppercase() {
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Color::White
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} else {
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Color::Black
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};
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let rights = &mut res[color.index()];
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match b {
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'k' | 'K' => *rights = rights.with_king_side(),
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'q' | 'Q' => *rights = rights.with_queen_side(),
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_ => return Err(FenError::InvalidFen),
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}
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}
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Ok(res)
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}
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}
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/// Convert a side to move segment of a FEN string to a [Color].
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impl FromFen for Color {
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type Err = FenError;
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fn from_fen(s: &str) -> Result<Self, Self::Err> {
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let res = match s {
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"w" => Color::White,
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"b" => Color::Black,
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_ => return Err(FenError::InvalidFen),
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};
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Ok(res)
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}
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}
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/// Convert an en-passant target square segment of a FEN string to an optional [Square].
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impl FromFen for Option<Square> {
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type Err = FenError;
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fn from_fen(s: &str) -> Result<Self, Self::Err> {
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let res = match s.as_bytes() {
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[b'-'] => None,
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[file @ b'a'..=b'h', rank @ b'1'..=b'8'] => Some(Square::new(
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File::from_index((file - b'a') as usize),
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Rank::from_index((rank - b'1') as usize),
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)),
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_ => return Err(FenError::InvalidFen),
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};
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Ok(res)
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}
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}
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/// Convert a piece in FEN notation to a [Piece].
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impl FromFen for Piece {
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type Err = FenError;
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fn from_fen(s: &str) -> Result<Self, Self::Err> {
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let res = match s {
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"p" | "P" => Self::Pawn,
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"n" | "N" => Self::Knight,
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"b" | "B" => Self::Bishop,
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"r" | "R" => Self::Rook,
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"q" | "Q" => Self::Queen,
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"k" | "K" => Self::King,
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_ => return Err(FenError::InvalidFen),
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};
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Ok(res)
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}
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}
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