diff --git a/src/movegen/mod.rs b/src/movegen/mod.rs index 9f4f280..746011d 100644 --- a/src/movegen/mod.rs +++ b/src/movegen/mod.rs @@ -2,4 +2,5 @@ mod bishop; mod king; mod knight; +mod pawn; mod rook; diff --git a/src/movegen/pawn.rs b/src/movegen/pawn.rs new file mode 100644 index 0000000..53551c5 --- /dev/null +++ b/src/movegen/pawn.rs @@ -0,0 +1,139 @@ +use crate::board::{Bitboard, Color, Direction, Rank, Square}; + +/// Compute a pawn's movement given its color, and a set of blockers that cannot be moved past. +#[allow(unused)] +pub fn pawn_moves(color: Color, square: Square, blockers: Bitboard) -> Bitboard { + if (square.rank() == Rank::First) || (square.rank() == Rank::Eighth) { + return Bitboard::EMPTY; + } + + let dir = color.forward_direction(); + + let first_push = dir.move_board(square.into_bitboard()); + let second_push = if square.rank() == color.second_rank() { + Square::new(square.file(), color.fourth_rank()).into_bitboard() + } else { + Bitboard::EMPTY + }; + + if (first_push & blockers).is_empty() { + first_push | second_push + } else { + Bitboard::EMPTY + } +} + +/// Computes the set of squares a pawn can capture, given its color. +#[allow(unused)] +pub fn pawn_captures(color: Color, square: Square) -> Bitboard { + if (square.rank() == Rank::First) || (square.rank() == Rank::Eighth) { + return Bitboard::EMPTY; + } + + let dir = color.forward_direction(); + + let advanced = dir.move_board(square.into_bitboard()); + + let attack_west = Direction::West.move_board(advanced); + let attack_east = Direction::East.move_board(advanced); + + attack_west | attack_east +} + +/// Computes the set of squares that can capture this one *en-passant*. +#[allow(unused)] +pub fn en_passant_origins(square: Square) -> Bitboard { + let board = square.into_bitboard(); + + let origin_west = Direction::West.move_board(board); + let origin_east = Direction::East.move_board(board); + + origin_west | origin_east +} + +#[cfg(test)] +mod test { + use super::*; + + #[test] + fn moves() { + assert_eq!( + pawn_moves(Color::White, Square::A2, Bitboard::EMPTY), + Square::A3 | Square::A4 + ); + assert_eq!( + pawn_moves(Color::Black, Square::A7, Bitboard::EMPTY), + Square::A5 | Square::A6 + ); + assert_eq!( + pawn_moves(Color::Black, Square::A2, Bitboard::EMPTY), + Square::A1.into_bitboard() + ); + assert_eq!( + pawn_moves(Color::White, Square::A7, Bitboard::EMPTY), + Square::A8.into_bitboard() + ); + } + + #[test] + fn captures() { + assert_eq!( + pawn_captures(Color::White, Square::A2), + Square::B3.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::White, Square::B2), + Square::A3 | Square::C3 + ); + assert_eq!( + pawn_captures(Color::White, Square::H2), + Square::G3.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::Black, Square::A2), + Square::B1.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::Black, Square::B2), + Square::A1 | Square::C1 + ); + assert_eq!( + pawn_captures(Color::Black, Square::H2), + Square::G1.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::White, Square::A7), + Square::B8.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::White, Square::B7), + Square::A8 | Square::C8 + ); + assert_eq!( + pawn_captures(Color::Black, Square::H7), + Square::G6.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::Black, Square::A7), + Square::B6.into_bitboard() + ); + assert_eq!( + pawn_captures(Color::Black, Square::B7), + Square::A6 | Square::C6 + ); + assert_eq!( + pawn_captures(Color::Black, Square::H7), + Square::G6.into_bitboard() + ); + } + + #[test] + fn en_passant() { + assert_eq!(en_passant_origins(Square::A4), Square::B4.into_bitboard()); + assert_eq!(en_passant_origins(Square::A5), Square::B5.into_bitboard()); + assert_eq!(en_passant_origins(Square::B4), Square::A4 | Square::C4); + assert_eq!(en_passant_origins(Square::B5), Square::A5 | Square::C5); + assert_eq!(en_passant_origins(Square::H4), Square::G4.into_bitboard()); + assert_eq!(en_passant_origins(Square::H5), Square::G5.into_bitboard()); + } +}