refactor: separately store pawn double pushes

1 files changed, 13 insertions, 8 deletions

diff --git a/src/board.rs b/src/board.rs
index 625711e..24bdefa 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -144,7 +144,8 @@ impl Board {
     pub fn generate_moves(&self, color: Color) -> Vec<Move> {
         let mut moves = Vec::with_capacity(1024);
         let opponent_occupancy = self.color_occupancy(Color::from(1 - color as u8));
-        let available_targets = opponent_occupancy | self.empty();
+        let empty = self.empty();
+        let available_targets = opponent_occupancy | empty;
         for (piece_type, piece) in self.pieces_by_color(color).iter().enumerate() {
             match PieceType::from(piece_type) {
                 PieceType::Pawn => {
@@ -152,14 +153,18 @@ impl Board {
                         for target in serialize_bitboard(self.attacks.pawn[color as usize][source as usize] & opponent_occupancy) {
                             moves.push(Move { source, target });
                         };
-                    }
-                    for source in serialize_bitboard(*piece) {
                         for target in serialize_bitboard(self.attacks.pawn_pushes[color as usize][source as usize] & available_targets) {
-                            // Exclude double pushes in a monkey way
-                            // TODO: properly rewrite this storing a separate bitboard for double pushes
-                            if !((source as u8 / 8 == 1) && (target as u8 / 8 == 3) && (self.occupancy & (1 << (source as u8 + 8)) > 0)) {
-                                moves.push(Move { source, target });
-                            }
+                            moves.push(Move { source, target });
+                        };
+                    }
+
+                    let able_to_double_push_mask = match color {
+                        Color::White => empty >> 8,
+                        Color::Black => empty << 8,
+                    };
+                    for source in serialize_bitboard(*piece & able_to_double_push_mask) {
+                        for target in serialize_bitboard(self.attacks.pawn_double_pushes[color as usize][source as usize] & available_targets) {
+                            moves.push(Move { source, target });
                         };
                     }
                 }