def clearance(puzzle: Puzzle) -> bool:
for node in puzzle.mainline[1::2][1:]:
board = node.board()
if not node.parent.board().piece_at(node.move.to_square):
piece = board.piece_at(node.move.to_square)
if piece and piece.piece_type in util.ray_piece_types:
prev = node.parent.parent
assert prev
prev_move = prev.move
assert prev_move
assert isinstance(node.parent, ChildNode)
if (not prev_move.promotion
and prev_move.to_square != node.move.from_square
and prev_move.to_square != node.move.to_square
and not node.parent.board().is_check()
and (not board.is_check()
or util.moved_piece_type(node.parent) != KING)):
if (prev_move.from_square == node.move.to_square
or prev_move.from_square in SquareSet.between(
node.move.from_square, node.move.to_square)):
if prev.parent and not prev.parent.board().piece_at(
prev_move.to_square) or util.is_in_bad_spot(
prev.board(), prev_move.to_square):
return True
return False
def skewer(puzzle: Puzzle) -> bool:
for node in puzzle.mainline[1::2][1:]:
prev = node.parent
assert isinstance(prev, ChildNode)
capture = prev.board().piece_at(node.move.to_square)
if capture and util.moved_piece_type(
node
) in util.ray_piece_types and not node.board().is_checkmate():
between = SquareSet.between(node.move.from_square,
node.move.to_square)
op_move = prev.move
assert op_move
if (op_move.to_square == node.move.to_square
or not op_move.from_square in between):
continue
if (util.king_values[util.moved_piece_type(prev)] >
util.king_values[capture.piece_type] and
util.is_in_bad_spot(prev.board(), node.move.to_square)):
return True
return False
def fork(puzzle: Puzzle) -> bool:
for node in puzzle.mainline[1::2][:-1]:
if util.moved_piece_type(node) is not KING:
board = node.board()
if util.is_in_bad_spot(board, node.move.to_square):
continue
nb = 0
for (piece, square) in util.attacked_opponent_squares(
board, node.move.to_square, puzzle.pov):
if piece.piece_type == PAWN:
continue
if (util.king_values[piece.piece_type] >
util.king_values[util.moved_piece_type(node)]
or (util.is_hanging(board, piece, square)
and square not in board.attackers(
not puzzle.pov, node.move.to_square))):
nb += 1
if nb > 1:
return True
return False