feat: implement promotions

1 files changed, 70 insertions, 24 deletions

diff --git a/src/board/mod.rs b/src/board/mod.rs
index d8166c3..cce2ca7 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -246,8 +246,8 @@ impl Board {
         let available_targets = opponent_occupancy | empty;
         let player_pieces = self.pieces_by_color(color);
 
-        for (piece_type, piece) in player_pieces.iter().enumerate() {
-            match PieceType::from(piece_type) {
+        for (piece_id, piece) in player_pieces.iter().enumerate() {
+            match PieceType::from(piece_id) {
                 PieceType::Pawn => {
                     for source in serialize_bitboard(*piece) {
                         let ep_bitboard = match self.ep_target {
@@ -256,12 +256,30 @@ impl Board {
                         };
                         for target in serialize_bitboard(self.attacks.pawn[color as usize][source as usize] & opponent_occupancy) {
                             moves.push(Move { source, target, kind: MoveKind::Capture });
+                            if (target.rank() == 7) {
+                                for promo_type in [PieceType::Bishop, PieceType::Knight, PieceType::Rook, PieceType::Queen] {
+                                    moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
+                                }
+                            } else if (target.rank() == 0) {
+                                for promo_type in [PieceType::BishopBlack, PieceType::KnightBlack, PieceType::RookBlack, PieceType::QueenBlack] {
+                                    moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
+                                }
+                            }
                         };
                         for target in serialize_bitboard(self.attacks.pawn[color as usize][source as usize] & ep_bitboard) {
                             moves.push(Move { source, target, kind: MoveKind::EnPassant });
                         }
                         for target in serialize_bitboard(self.attacks.pawn_pushes[color as usize][source as usize] & empty) {
                             moves.push(Move { source, target, kind: MoveKind::Quiet });
+                            if (target.rank() == 7) {
+                                for promo_type in [PieceType::Bishop, PieceType::Knight, PieceType::Rook, PieceType::Queen] {
+                                    moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
+                                }
+                            } else if (target.rank() == 0) {
+                                for promo_type in [PieceType::BishopBlack, PieceType::KnightBlack, PieceType::RookBlack, PieceType::QueenBlack] {
+                                    moves.push(Move { source, target, kind: MoveKind::Promotion(promo_type)})
+                                }
+                            }
                         };
                     }
 
@@ -529,13 +547,27 @@ impl Board {
         let source_piece = match self.piece_by_square(mov.source) {
             Some(source_piece) => {
                 let source_id = source_piece as usize;
-                self.pieces[source_id] ^= move_source_bb;
-                self.occupancy            ^= move_source_bb;
-                self.hash                 ^= self.zobrist_seed[source_id * 64 + mov.source as usize];
+                match mov.kind {
+                    MoveKind::Promotion(promotion_piece) => {
+                        let promo_id = promotion_piece as usize;
+                        self.pieces[source_id]    ^= move_source_bb;
+                        self.occupancy            ^= move_source_bb;
+                        self.hash                 ^= self.zobrist_seed[source_id * 64 + mov.source as usize];
+
+                        self.pieces[promo_id]     |= move_target_bb;
+                        self.occupancy            |= move_target_bb;
+                        self.hash                 ^= self.zobrist_seed[promo_id * 64 + mov.target as usize];
+                    },
+                    _ => {
+                        self.pieces[source_id]    ^= move_source_bb;
+                        self.occupancy            ^= move_source_bb;
+                        self.hash                 ^= self.zobrist_seed[source_id * 64 + mov.source as usize];
 
-                self.pieces[source_id] |= move_target_bb;
-                self.occupancy            |= move_target_bb;
-                self.hash                 ^= self.zobrist_seed[source_id * 64 + mov.target as usize];
+                        self.pieces[source_id]    |= move_target_bb;
+                        self.occupancy            |= move_target_bb;
+                        self.hash                 ^= self.zobrist_seed[source_id * 64 + mov.target as usize];
+                    }
+                }
                 PieceType::from(source_piece)
             },
             None => {
@@ -595,11 +627,11 @@ impl Board {
             PieceType::Rook => {
                 match mov.source.file() {
                     0 => {
-                        self.castling_rights[Color::from_piece(source_piece) as usize][CastlingSide::Queen as usize] = false;
+                        self.castling_rights[source_color][CastlingSide::Queen as usize] = false;
                         self.hash ^= self.zobrist_seed[64 * 12 + source_color * 2 + CastlingSide::Queen as usize];
                     }
                     7 => {
-                        self.castling_rights[Color::from_piece(source_piece) as usize][CastlingSide::King as usize] = false;
+                        self.castling_rights[source_color][CastlingSide::King as usize] = false;
                         self.hash ^= self.zobrist_seed[64 * 12 + source_color * 2 + CastlingSide::King as usize];
                     }
                     _ => {},
@@ -627,20 +659,34 @@ impl Board {
         let move_target_bb = mov.target.to_bitboard();
 
         // Move a piece from target square back to source square
-        match self.pieces
-            .iter()
-            .enumerate()
-            .find(|(piece_type, bitboard)| *bitboard & mov.target.to_bitboard() > 0)
-            {
-                Some((source_piece, _)) => {
-                    self.pieces[source_piece] ^= move_target_bb;
-                    self.occupancy            ^= move_target_bb;
-
-                    self.pieces[source_piece] |= move_source_bb;
-                    self.occupancy            |= move_source_bb;
-                },
-                None => panic!("Trying to unmake move which was not made: no piece was found on target square"),
-            };
+        match self.piece_by_square(mov.target) {
+            Some(source_piece) => {
+                match mov.kind {
+                    MoveKind::Promotion(promotion_piece) => {
+                        let promo_id = promotion_piece as usize;
+                        self.pieces[promo_id]  ^= move_target_bb;
+                        self.occupancy         ^= move_target_bb;
+
+                        let source_id = match Color::from_piece(promotion_piece) {
+                            Color::White => PieceType::Pawn,
+                            Color::Black => PieceType::PawnBlack,
+                        } as usize;
+
+                        self.pieces[source_id] |= move_source_bb;
+                        self.occupancy         |= move_source_bb;
+                    }
+                    _ => {
+                        let source_id = source_piece as usize;
+                        self.pieces[source_id] ^= move_target_bb;
+                        self.occupancy         ^= move_target_bb;
+
+                        self.pieces[source_id] |= move_source_bb;
+                        self.occupancy         |= move_source_bb;
+                    }
+                }
+            },
+            None => panic!("Trying to unmake move which was not made: no piece was found on target square"),
+        };
 
         // If unmaking castle, also return rook to its place
         if mov.kind == MoveKind::Castle {