rules: rework castling rules
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42
src/rules.rs
42
src/rules.rs
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@ -39,7 +39,14 @@ pub const CASTLING_BL_MASK: u8 = 0b00001100;
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pub const CASTLING_K_MASK: u8 = 0b00000101;
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pub const CASTLING_Q_MASK: u8 = 0b00001010;
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pub const CASTLING_MASK: u8 = 0b00001111;
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pub const CASTLING_SIDES: [(i8, u8); 2] = [(5i8, CASTLING_K_MASK), (3i8, CASTLING_Q_MASK)];
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/// Castling sides parameters.
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///
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/// For both sides, the 3-uple contains files that should be empty
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/// and not attacked, an optional file that should be empty for
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/// queen-side, and the castling side-mask.
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pub const CASTLING_SIDES: [([i8; 2], Option<i8>, u8); 2] =
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[([5i8, 6i8], None, CASTLING_K_MASK), ([3i8, 2i8], Some(1i8), CASTLING_Q_MASK)];
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pub const START_WH_K_POS: Pos = pos("e1");
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pub const START_BL_K_POS: Pos = pos("e8");
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@ -447,24 +454,39 @@ fn get_king_moves(
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};
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// Check for castling if the king is on its castling rank (R1)
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// and is not in check (R4)
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// and is not in check (R4).
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if
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*r == castling_rank &&
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!is_attacked(board, game_state, at)
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{
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// Check for both castling sides.
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for (through_f, castling_side_mask) in CASTLING_SIDES.iter() {
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for (path_files, opt_empty_file, castling_side_mask) in CASTLING_SIDES.iter() {
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// Check for castling availability for this color and side.
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if (game_state.castling & castling_color_mask & castling_side_mask) != 0 {
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// R3, R5, R6: check that files on the way are empty and not attacked.
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let p = (*through_f, castling_rank);
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if is_empty(board, &p) && !is_illegal(board, game_state, &(*at, p, None)) {
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let castle = CASTLING_K_MASK & castling_color_mask;
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let m = get_castle_move(castle);
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if can_register(commit, board, game_state, &m) {
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moves.push(m);
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// Check that squares in the king's path are empty and not attacked (R3.1, R5, R6).
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let mut path_is_clear = true;
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for path_f in path_files {
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let p = (*path_f, castling_rank);
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if !is_empty(board, &p) || is_illegal(board, game_state, &(*at, p, None)) {
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path_is_clear = false;
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break;
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}
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}
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if !path_is_clear {
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continue;
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}
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// Check that rook jumps over an empty square on queen-side (R3.2).
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if let Some(rook_path_f) = opt_empty_file {
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let p = (*rook_path_f, castling_rank);
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if !is_empty(board, &p) {
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continue;
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}
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}
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let castle = castling_side_mask & castling_color_mask;
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let m = get_castle_move(castle);
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if can_register(commit, board, game_state, &m) {
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moves.push(m);
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}
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}
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}
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}
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