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use smallvec::SmallVec;
use crate::{moves::{Move, MoveKind}, board::{color::Color, piece::Piece, CastlingSide}, bitboard::BitboardFns, square::Square};
use super::Board;
pub type MoveList = SmallVec<[Move; 128]>;
impl Board {
pub fn generate_pseudolegal_moves(&self) -> MoveList {
let mut result = MoveList::new();
result.append(&mut self.generate_moves_core(true));
result.append(&mut self.generate_moves_core(false));
result
}
pub fn generate_moves_core(&self, tactical_only: bool) -> MoveList {
let color = self.color();
let player_pieces = self.pieces_by_color(color);
let mut moves = MoveList::new();
let empty = self.empty();
let targets = if tactical_only {
self.color_occupancy(color.flip()) ^ match color {
// Exclude opponent king because we can't capture it
Color::White => self.piece_sets[Piece::KingBlack as usize],
Color::Black => self.piece_sets[Piece::King as usize],
}
} else {
empty
};
let kind = if tactical_only {
MoveKind::Capture
} else {
MoveKind::Quiet
};
for (piece_id, piece) in player_pieces.iter().enumerate() {
for source in piece.serialize() {
let piece_type = Piece::from(piece_id);
let move_targets = match piece_type {
Piece::Bishop => self.attacks.bishop(self.occupancy, source),
Piece::Rook => self.attacks.rook(self.occupancy, source),
Piece::Queen => self.attacks.queen(self.occupancy, source),
Piece::Knight => self.attacks.knight[source as usize],
Piece::King => self.attacks.king[source as usize],
Piece::Pawn => if tactical_only {
self.attacks.pawn[color as usize][source as usize]
} else {
self.attacks.pawn_pushes[color as usize][source as usize]
},
_ => panic!("Incorrect piece type"),
};
// Generalized attack/move pattern for all pieces
for target in (move_targets & targets).serialize() {
moves.push(Move { source, target, kind });
// Promotions
if piece_type == Piece::Pawn {
if target.rank() == 7 {
for promo_type in [Piece::Bishop, Piece::Knight, Piece::Rook, Piece::Queen] {
moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
}
} else if target.rank() == 0 {
for promo_type in [Piece::BishopBlack, Piece::KnightBlack, Piece::RookBlack, Piece::QueenBlack] {
moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
}
}
}
}
// En Passant
if piece_type == Piece::Pawn && tactical_only {
for target in (move_targets & self.ep_bitboard()).serialize() {
moves.push(Move { source, target, kind: MoveKind::EnPassant });
}
}
}
}
if !tactical_only {
// Double Pushes
// Make sure no blocking piece is standing in front of the pawns
// that are potential double-push sources
let able_to_double_push_mask = match color {
Color::White => empty >> 8,
Color::Black => empty << 8,
};
for source in (player_pieces[Piece::Pawn as usize] & able_to_double_push_mask).serialize() {
for target in (self.attacks.pawn_double_pushes[color as usize][source as usize] & empty).serialize() {
moves.push(Move { source, target, kind: MoveKind::DoublePush });
};
}
// Castling
let king_home_position = match color {
Color::White => Square::E1,
Color::Black => Square::E8,
};
if player_pieces[Piece::King as usize].bitscan() == king_home_position {
for rook_square in player_pieces[Piece::Rook as usize]
.serialize()
.filter(|rook_square| rook_square.rank() == king_home_position.rank())
{
match rook_square.file() {
0 => {
let all_empty = [
king_home_position.west_one(),
king_home_position.west_one().west_one(),
king_home_position.west_one().west_one().west_one(),
].iter().all(|square| empty & square.to_bitboard() > 0);
let any_checks = [
king_home_position,
king_home_position.west_one(),
king_home_position.west_one().west_one(),
].iter().any(|square| self.is_square_attacked(*square, color.flip()));
if all_empty && !any_checks && self.castling_rights[color as usize][CastlingSide::Queen as usize] {
moves.push(Move {
source: king_home_position,
target: king_home_position.west_one().west_one(),
kind: MoveKind::Castle,
})
}
},
7 => {
let all_empty = [
king_home_position.east_one(),
king_home_position.east_one().east_one(),
].iter().all(|square| empty & square.to_bitboard() > 0);
let any_checks = [
king_home_position,
king_home_position.east_one(),
king_home_position.east_one().east_one(),
].iter().any(|square| self.is_square_attacked(*square, color.flip()));
if all_empty && !any_checks && self.castling_rights[color as usize][CastlingSide::King as usize] {
moves.push(Move {
source: king_home_position,
target: king_home_position.east_one().east_one(),
kind: MoveKind::Castle,
})
}
},
_ => {},
}
}
}
}
moves
}
}
#[cfg(test)]
mod tests {
use crate::board::{Board, io::IO};
use super::*;
#[test]
fn generate_pseudolegal_moves_starting_position() {
let mut board = Board::new();
let moves = board.generate_pseudolegal_moves();
let black_moves = board.generate_pseudolegal_moves();
assert_eq!(moves.len(), 20);
assert_eq!(black_moves.len(), 20);
for mov in moves {
mov.print();
}
}
#[test]
fn moved_king_castle() {
let fen = String::from("4k2r/ppp1n3/8/4R1Pp/5P2/q1P5/P1P1BP2/1K1R4 b - - 2 22");
let mut board = Board::from_FEN(fen);
// Shuffle kings around, returning to the same position
board.make_move(Move { source: Square::E8, target: Square::F8, kind: MoveKind::Quiet });
board.make_move(Move { source: Square::B1, target: Square::A1, kind: MoveKind::Quiet });
board.make_move(Move { source: Square::F8, target: Square::E8, kind: MoveKind::Quiet });
board.make_move(Move { source: Square::A1, target: Square::B1, kind: MoveKind::Quiet });
board.print();
let moves = board.generate_pseudolegal_moves();
let castle = moves.iter().find(|m| **m == Move { source: Square::E8, target: Square::G8, kind: MoveKind::Castle });
println!("{:?}", board.castling_rights);
assert!(castle.is_none(), "Castle should not be allowed after king has moved");
}
}
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