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Add 'ChessBoard::is_valid'

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Bruno BELANYI 2022-07-28 21:37:47 +02:00
parent ddcef6f9c0
commit 3cd2601f07
1 changed files with 302 additions and 0 deletions
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302
src/board/chess_board.rs
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@ -178,6 +178,93 @@ impl ChessBoard {
self.total_plies -= 1;
self.side = !self.side;
}
/// Return true if the current state of the board looks valid, false if something is definitely
/// wrong.
pub fn is_valid(&self) -> bool {
// Don't overlap pieces.
for piece in Piece::iter() {
#[allow(clippy::collapsible_if)]
for other in Piece::iter() {
if piece != other {
if !(self.piece_occupancy(piece) & self.piece_occupancy(other)).is_empty() {
return false;
}
}
}
}
// Don't overlap colors.
if !(self.color_occupancy(Color::White) & self.color_occupancy(Color::Black)).is_empty() {
return false;
}
// Calculate the union of all pieces.
let combined =
Piece::iter().fold(Bitboard::EMPTY, |board, p| board | self.piece_occupancy(p));
// Ensure that the pre-computed version is accurate.
if combined != self.combined_occupancy() {
return false;
}
// Ensure that all pieces belong to a color, and no color has pieces that don't exist.
if combined != (self.color_occupancy(Color::White) | self.color_occupancy(Color::Black)) {
return false;
}
// Have exactly one king of each color.
for color in Color::iter() {
if (self.piece_occupancy(Piece::King) & self.color_occupancy(color)).count() != 1 {
return false;
}
}
// Verify that rooks and kings that are allowed to castle have not been moved.
for color in Color::iter() {
let castle_rights = self.castle_rights(color);
// Nothing to check if there are no castlings allowed.
if castle_rights == CastleRights::NoSide {
continue;
}
let actual_rooks = self.piece_occupancy(Piece::Rook) & self.color_occupancy(color);
let expected_rooks = castle_rights.unmoved_rooks(color);
// We must check the intersection, in case there are more than 2 rooks on the board.
if (expected_rooks & actual_rooks) != expected_rooks {
return false;
}
let actual_king = self.piece_occupancy(Piece::King) & self.color_occupancy(color);
let expected_king = Square::new(File::E, color.first_rank());
// We have checked that there is exactly one king, no need for intersecting the sets.
if actual_king != expected_king.into_bitboard() {
return false;
}
}
// The current en-passant target square must be empty, right behind an opponent's pawn.
if let Some(square) = self.en_passant() {
if !(self.combined_occupancy() & square).is_empty() {
return false;
}
let opponent_pawns =
self.piece_occupancy(Piece::Pawn) & self.color_occupancy(!self.current_player());
let double_pushed_pawn = self
.current_player()
.backward_direction()
.move_board(square.into_bitboard());
if (opponent_pawns & double_pushed_pawn).is_empty() {
return false;
}
}
// FIXME: check for opponent being in check.
// FIXME: check for kings touching.
true
}
}
/// Use the starting position as a default value, corresponding to the
@ -215,3 +302,218 @@ impl Default for ChessBoard {
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn valid() {
let default_position = ChessBoard::default();
assert!(default_position.is_valid());
}
#[test]
fn invalid_overlapping_pieces() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Square::E1 | Square::E8,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1.into_bitboard(), Square::E8.into_bitboard()],
combined_occupancy: Square::E1 | Square::E8,
castle_rights: [CastleRights::NoSide; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_overlapping_colors() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Bitboard::EMPTY,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1 | Square::E8, Square::E1 | Square::E8],
combined_occupancy: Square::E1 | Square::E8,
castle_rights: [CastleRights::NoSide; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_combined_does_not_equal_pieces() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Bitboard::EMPTY,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1.into_bitboard(), Square::E8.into_bitboard()],
combined_occupancy: Square::E1.into_bitboard(),
castle_rights: [CastleRights::NoSide; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_combined_does_not_equal_colors() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Bitboard::EMPTY,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1 | Square::H1, Square::E8 | Square::H8],
combined_occupancy: Square::E1 | Square::E8,
castle_rights: [CastleRights::NoSide; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_multiple_kings() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E2 | Square::E7 | Square::E8,
// Queen
Bitboard::EMPTY,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1 | Square::E2, Square::E7 | Square::E8],
combined_occupancy: Square::E1 | Square::E2 | Square::E7 | Square::E8,
castle_rights: [CastleRights::NoSide; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_castling_rights_no_rooks() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E1 | Square::E8,
// Queen
Bitboard::EMPTY,
// Rook
Bitboard::EMPTY,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [Square::E1.into_bitboard(), Square::E8.into_bitboard()],
combined_occupancy: Square::E1 | Square::E8,
castle_rights: [CastleRights::BothSides; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
#[test]
fn invalid_castling_rights_moved_king() {
let position = ChessBoard {
piece_occupancy: [
// King
Square::E2 | Square::E7,
// Queen
Bitboard::EMPTY,
// Rook
Square::A1 | Square::A8 | Square::H1 | Square::H8,
// Bishop
Bitboard::EMPTY,
// Knight
Bitboard::EMPTY,
// Pawn
Bitboard::EMPTY,
],
color_occupancy: [
Square::A1 | Square::E2 | Square::H1,
Square::A8 | Square::E7 | Square::H8,
],
combined_occupancy: Square::A1
| Square::A8
| Square::E1
| Square::E8
| Square::H1
| Square::H8,
castle_rights: [CastleRights::BothSides; 2],
en_passant: None,
half_move_clock: 0,
total_plies: 0,
side: Color::White,
};
assert!(!position.is_valid());
}
}