implemented full FEN parser
todo: fix bugs
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c3439bdd46
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cccf41e7b0
@ -1,11 +1,8 @@
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use chess_inator::Position;
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fn main() {
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let fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR ";
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let fen = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1";
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let board = Position::from_fen(fen.into()).unwrap();
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println!("{}", board);
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let fen = "rnbqkbnr/pp1ppppp/8/2p5/4P3/5N2/PPPP1PPP/RNBQKB1R ";
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let board = Position::from_fen(fen.into()).unwrap();
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print!("{}", board);
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println!("{:#?}", board);
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}
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177
src/lib.rs
177
src/lib.rs
@ -4,9 +4,9 @@ const BOARD_WIDTH: usize = 8;
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const BOARD_HEIGHT: usize = 8;
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const N_SQUARES: usize = BOARD_WIDTH * BOARD_HEIGHT;
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#[derive(Debug, Copy, Clone)]
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#[derive(Debug, Copy, Clone, Default)]
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enum Color {
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#[default]
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White,
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Black,
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}
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@ -36,10 +36,17 @@ impl TryFrom<char> for ColPiece {
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type Error = PieceErr;
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fn try_from(value: char) -> Result<Self, Self::Error> {
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let col = if value.is_ascii_uppercase() { Color::White } else { Color::Black };
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let col = if value.is_ascii_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 mut lower = value;
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lower.make_ascii_lowercase();
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Ok(ColPiece {pc: Piece::try_from(lower)?, col})
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Ok(ColPiece {
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pc: Piece::try_from(lower)?,
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col,
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})
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}
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}
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@ -210,10 +217,27 @@ pub enum FenError {
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TooManyRows(usize),
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/// Too little rows.
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NotEnoughRows(usize),
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/// Parser refuses to keep parsing move counter because it is too big.
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TooManyMoves,
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/// Error in the parser.
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InternalError(usize),
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}
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/// Castling rights for one player
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#[derive(Debug)]
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pub struct CastlingRights {
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/// Kingside
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k: bool,
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/// Queenside
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q: bool,
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}
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impl Default for CastlingRights {
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fn default() -> Self {
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CastlingRights { k: true, q: true }
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}
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}
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/// Game state.
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///
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/// Default is empty.
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@ -224,6 +248,25 @@ pub struct Position {
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/// Mailbox (array) board. Location -> piece.
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mail: Mailbox,
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/// En-passant square.
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///
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/// (If a pawn moves twice, this is one square in front of the start position.)
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ep_square: Option<Index>,
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/// Castling rights (white)
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white_castle: CastlingRights,
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/// Castling rights (black)
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black_castle: CastlingRights,
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/// Plies since last irreversible (capture, pawn) move
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half_moves: usize,
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/// Full move counter (incremented after each black turn)
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full_moves: usize,
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/// Whose turn it is
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turn: Color,
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}
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impl Position {
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@ -257,9 +300,10 @@ impl Position {
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//! Parse FEN string into position.
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/// Parser state machine.
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///
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/// Space characters are considered part of the preceding state.
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#[derive(Clone, Copy)]
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enum FenState {
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/// Parses space characters between arguments, and jumps to next state.
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Space,
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/// Accepts pieces in a row, or a slash, and stores row and column (0-indexed)
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Piece(usize, usize),
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/// Player whose turn it is
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@ -267,23 +311,49 @@ impl Position {
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/// Castling ability
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Castle,
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/// En passant square, letter part
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EnPassantRow,
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EnPassantFile,
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/// En passant square, digit part
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EnPassantCol,
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/// Half-move counter for 50-move draw rule. Resets after capture/pawn move.
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EnPassantRank,
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/// Half-move counter for 50-move draw rule
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HalfMove,
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/// Full-move counter, incremented after each Black move
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/// Full-move counter
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FullMove,
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/// Final state.
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Stop,
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}
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/// Maximum amount of moves in the counter to parse before giving up
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const MAX_MOVES: usize = 999_999;
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let mut pos = Position::default();
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let mut parser_state = FenState::Piece(0, 0);
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let mut next_state = FenState::Space;
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/// Create parse error at a given index
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macro_rules! bad_char {
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($idx:ident) => {
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Err(FenError::BadChar($idx))
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};
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}
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/// Parse a space character, then jump to the given state
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macro_rules! parse_space_and_goto {
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($next:expr) => {
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parser_state = FenState::Space;
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next_state = $next;
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};
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}
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for (i, c) in fen.chars().enumerate() {
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match parser_state {
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FenState::Space => {
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match c {
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' ' => {
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parser_state = next_state;
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}
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_ => return bad_char!(i),
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};
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}
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FenState::Piece(mut row, mut col) => {
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// FEN stores rows differently from our bitboard
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let real_row = BOARD_HEIGHT - 1 - row;
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@ -300,7 +370,7 @@ impl Position {
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parser_state = FenState::Piece(row, col)
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}
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pc_char @ ('b'..='r' | 'B'..='R') => {
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let pc = ColPiece::try_from(pc_char).or(Err(FenError::BadChar(i)))?;
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let pc = ColPiece::try_from(pc_char).or(bad_char!(i))?;
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pos.set_piece(
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Index::from_row_col(real_row, col)
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@ -321,7 +391,7 @@ impl Position {
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};
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parser_state = FenState::Piece(row, col);
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} else {
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return Err(FenError::BadChar(i));
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return bad_char!(i);
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}
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}
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' ' => {
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@ -330,34 +400,83 @@ impl Position {
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} else if col < BOARD_WIDTH {
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return Err(FenError::NotEnoughPieces(i));
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}
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parser_state = FenState::Stop
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parser_state = FenState::Side
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}
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_ => return Err(FenError::BadChar(i)),
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_ => return bad_char!(i),
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};
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}
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FenState::Side => {
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todo!()
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match c {
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'w' => pos.turn = Color::White,
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'b' => pos.turn = Color::Black,
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_ => return bad_char!(i),
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}
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parse_space_and_goto!(FenState::Castle);
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}
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FenState::Castle => {
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todo!()
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FenState::Castle => match c {
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'Q' => pos.white_castle.q = true,
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'q' => pos.black_castle.q = true,
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'K' => pos.white_castle.k = true,
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'k' => pos.black_castle.k = true,
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' ' => parser_state = FenState::EnPassantRank,
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'-' => {
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parse_space_and_goto!(FenState::EnPassantRank);
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}
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_ => return bad_char!(i),
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},
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FenState::EnPassantRank => {
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match c {
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'-' => {
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parse_space_and_goto!(FenState::HalfMove);
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}
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'a'..='h' => {
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// TODO: fix this
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pos.ep_square = Some(Index((c as usize - 'a' as usize) * 8));
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parser_state = FenState::EnPassantFile;
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}
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_ => return bad_char!(i),
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};
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}
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FenState::EnPassantRow => {
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todo!()
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}
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FenState::EnPassantCol => {
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todo!()
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FenState::EnPassantFile => {
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if let Some(digit) = c.to_digit(10) {
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pos.ep_square = Some(Index(
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usize::from(pos.ep_square.unwrap_or(Index(0))) + digit as usize,
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));
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} else {
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return bad_char!(i);
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}
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parse_space_and_goto!(FenState::HalfMove);
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}
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FenState::HalfMove => {
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todo!()
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if let Some(digit) = c.to_digit(10) {
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if pos.half_moves > MAX_MOVES {
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return Err(FenError::TooManyMoves);
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}
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pos.half_moves *= 10;
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pos.half_moves += digit as usize;
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} else if c == ' ' {
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parser_state = FenState::FullMove;
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} else {
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return bad_char!(i);
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}
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}
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FenState::FullMove => {
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todo!()
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if let Some(digit) = c.to_digit(10) {
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if pos.half_moves > MAX_MOVES {
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return Err(FenError::TooManyMoves);
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}
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pos.full_moves *= 10;
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pos.full_moves += digit as usize;
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} else {
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return bad_char!(i);
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}
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}
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FenState::Stop => return Err(FenError::ExtraChar(i)),
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}
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}
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if matches!(parser_state, FenState::Stop) {
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// parser is always ready to receive another full move digit,
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// so there is no real "stop" state
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if matches!(parser_state, FenState::FullMove) {
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Ok(pos)
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} else {
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Err(FenError::MissingFields)
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@ -375,7 +494,7 @@ impl core::fmt::Display for Position {
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str.push(ColPiece::opt_to_char(pc));
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}
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str += "\n";
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};
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}
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write!(f, "{}", str)
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}
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}
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