feat: ensure king does not castle through check
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ba0dffab22
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16141e851c
@ -109,15 +109,15 @@ impl FromFen for BoardState {
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pc_char @ ('a'..='z' | 'A'..='Z') => {
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let pc = ColPiece::try_from(pc_char).or(bad_char!(i, c))?;
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if col > 7 {
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return Err(FenError::TooManyPieces(i));
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};
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pos.set_piece(
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Square::from_row_col(real_row, col)
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.or(Err(FenError::InternalError(i)))?,
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pc,
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);
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col += 1;
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if col > 8 {
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return Err(FenError::TooManyPieces(i));
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};
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parser_state = FenState::Piece(row, col)
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}
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number @ '1'..='9' => {
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@ -6,8 +6,6 @@ use std::str::FromStr;
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pub mod fen;
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pub mod movegen;
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use fen::FromFen;
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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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@ -485,7 +483,7 @@ impl BoardState {
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}
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fn move_piece(&mut self, src: Square, dest: Square) {
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let pc = self.del_piece(src).expect("Move source should have piece.");
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let pc = self.del_piece(src).unwrap_or_else(|_| panic!("move ({src} -> {dest}) should have piece at source"));
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self.set_piece(dest, pc);
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}
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@ -543,6 +541,8 @@ impl core::fmt::Display for BoardState {
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mod tests {
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use super::*;
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use fen::FromFen;
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#[test]
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fn test_square_casts() {
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let fail_cases = [-1, 64, 0x7FFFFFFF, 257, 256, 128, 65, -3, !0x7FFFFFFF];
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144
src/movegen.rs
144
src/movegen.rs
@ -188,6 +188,7 @@ impl Move {
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.expect("rook castling src square should be valid");
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let rook_dest = Square::from_row_col(rook_row, rook_dest_col)
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.expect("rook castling dest square should be valid");
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debug_assert!(new_pos.get_piece(rook_src).is_some(), "rook castling src square has no rook (move: {rook_src} -> {rook_dest})");
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new_pos.move_piece(rook_src, rook_dest);
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}
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debug_assert!(
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@ -306,8 +307,9 @@ impl FromUCIAlgebraic for Move {
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/// Pseudo-legal move generation.
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///
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/// "Pseudo-legal" here means that moving into check is allowed, and capturing friendly pieces is
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/// allowed. These will be filtered out in the legal move generation step.
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/// "Pseudo-legal" here means that moving into check (but not castling through check) is allowed,
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/// and capturing friendly pieces is allowed. These will be filtered out in the legal move
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/// generation step.
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pub trait PseudoMoveGen {
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fn gen_pseudo_moves(&self) -> impl IntoIterator<Item = Move>;
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}
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@ -416,41 +418,69 @@ impl PseudoMoveGen for BoardState {
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}
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for src in squares!(King) {
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move_slider(self, src, &mut ret, SliderDirection::Star, false);
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let (r, c) = src.to_row_col();
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let (r, c) = src.to_row_col_signed();
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let rights = self.pl_castle(self.turn);
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let castle_sides = [(rights.k, 2, BOARD_WIDTH - 1), (rights.q, -2, 0)];
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let castle_sides = [(rights.k, 2, BOARD_WIDTH as isize - 1), (rights.q, -2, 0)];
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for (is_allowed, move_offset, endpoint) in castle_sides {
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if !is_allowed {
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continue;
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}
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let range = if c < endpoint {
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let (rook_r, rook_c) = (r, endpoint);
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let rook_sq = Square::from_row_col_signed(rook_r, rook_c).unwrap();
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let rook_exists = self
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.get_piece(rook_sq)
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.map_or(false, |pc| pc.pc == Piece::Rook);
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if !rook_exists {
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continue;
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}
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let path_range = if c < endpoint {
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(c + 1)..endpoint
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} else {
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(endpoint + 1)..c
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};
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debug_assert_ne!(
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range.len(),
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path_range.len(),
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0,
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"c {:?}, endpoint {:?}, range {:?}",
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c,
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endpoint,
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range
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path_range
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);
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let mut range_squares = range.map(|nc| Square::from_row_col(r, nc).unwrap());
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debug_assert_ne!(range_squares.len(), 0);
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let mut path_squares =
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path_range.map(|nc| Square::from_row_col_signed(r, nc).unwrap());
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debug_assert_ne!(path_squares.len(), 0);
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// find first blocking piece
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let is_path_blocked = range_squares.find_map(|sq| self.get_piece(sq)).is_some();
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let is_path_blocked = path_squares.find_map(|sq| self.get_piece(sq)).is_some();
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if is_path_blocked {
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continue;
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}
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let nc: isize = c.try_into().unwrap();
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let dest = Square::from_row_col_signed(r.try_into().unwrap(), nc + move_offset)
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let nc: isize = c + move_offset;
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let dest = Square::from_row_col_signed(r, nc)
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.expect("Castle destination square should be valid");
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debug_assert!(c.abs_diff(nc) == 2);
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// ensure the path is not being attacked (castle through check)
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let check_range = if c < nc { c..=nc } else { nc..=c };
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debug_assert!(!check_range.is_empty());
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let is_any_checked = check_range
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.map(|nc| Square::from_row_col_signed(r, nc).unwrap())
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.map(|dest| {
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let mut board = *self;
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board.move_piece(src, dest);
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is_check(&board, self.turn)
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})
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.any(|x| x);
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if is_any_checked {
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continue;
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}
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ret.push(Move {
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src,
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dest,
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@ -711,6 +741,21 @@ mod tests {
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),
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],
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),
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// white castle test (blocked again)
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(
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"8/8/8/8/8/8/r6r/R3K1nR w KQ - 0 1",
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vec![
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// NOTE: pseudo-legal e1
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("a1", vec!["b1", "a2", "c1", "d1", "e1"], MoveType::Normal),
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("h1", vec!["g1", "h2"], MoveType::Normal),
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// NOTE: pseudo-legal d2, e2, f2, f1
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(
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"e1",
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vec!["c1", "d1", "f1", "d2", "e2", "f2"],
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MoveType::Normal,
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),
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],
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),
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// white castle test (no rights, blocked)
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(
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"8/8/8/8/8/8/r6r/R3Kn1R w K - 0 1",
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@ -997,6 +1042,52 @@ mod tests {
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),
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],
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),
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// castling through check
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(
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"8/8/8/8/8/8/6rr/4K2R w KQ - 0 1",
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vec![
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("e1", vec!["d1", "f1"], MoveType::Normal),
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("h1", vec!["g1", "f1", "h2"], MoveType::Normal),
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],
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),
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// castling through check
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(
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"8/8/8/8/8/8/5r1r/4K2R w KQ - 0 1",
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vec![
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("e1", vec!["d1"], MoveType::Normal),
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("h1", vec!["g1", "f1", "h2"], MoveType::Normal),
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],
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),
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// castling while checked
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(
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"8/8/8/8/8/8/rrrrr2r/4K2R w KQ - 0 1",
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vec![
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("e1", vec!["f1"], MoveType::Normal),
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],
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),
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// castling while checked
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(
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"8/8/8/8/8/8/r3rrrr/R3K3 w KQ - 0 1",
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vec![
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("e1", vec!["d1"], MoveType::Normal),
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],
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),
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// castling through check
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(
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"8/8/8/8/8/8/r1r5/R3K3 w KQ - 0 1",
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vec![
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("e1", vec!["d1", "f1"], MoveType::Normal),
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("a1", vec!["a2", "b1", "c1", "d1"], MoveType::Normal),
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],
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),
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// castling through check
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(
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"8/8/8/8/8/8/r2r4/R3K3 w KQ - 0 1",
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vec![
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("e1", vec!["f1"], MoveType::Normal),
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("a1", vec!["a2", "b1", "c1", "d1"], MoveType::Normal),
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],
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),
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// check test
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(
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"1bqnb1q1/3q1n2/q2p4/2bKp1q1/1r1b4/1q3n2/8/k2q2b1 w - - 0 1",
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@ -1009,9 +1100,14 @@ mod tests {
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),
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];
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for (i, (fen, expected)) in test_cases.iter().enumerate() {
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for tc in test_cases {
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eprintln!("on test {}", tc.0);
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let (board, mut expected_moves) = decondense_moves(tc);
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expected_moves.sort_unstable();
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let node = Node {
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pos: BoardState::from_fen(fen).unwrap(),
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pos: board,
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prev: None,
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};
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@ -1019,27 +1115,9 @@ mod tests {
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moves.sort_unstable();
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let moves = moves;
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let mut expected_moves = expected
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.iter()
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.map(|(src, dests, move_type)| {
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let src = src.parse::<Square>().unwrap();
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let dests = dests
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.iter()
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.map(|x| x.parse::<Square>())
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.map(|x| x.unwrap());
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dests.map(move |dest| Move {
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src,
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dest,
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move_type: *move_type,
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})
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})
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.flatten()
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.collect::<Vec<Move>>();
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expected_moves.sort_unstable();
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let expected_moves = expected_moves;
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assert_eq!(moves, expected_moves, "failed test case {i} ({fen})");
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assert_eq!(moves, expected_moves);
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}
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}
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