refactor: split Board module into submodules

1 files changed, 28 insertions, 403 deletions

diff --git a/src/board/mod.rs b/src/board/mod.rs
index 5317cc2..e6a6446 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,7 +1,9 @@
 use crate::{bitboard::{Bitboard, BitboardFns}, moves::{Move, MoveKind}, attacks::Attacks, square::Square, board::io::IO};
 
-use self::{ttable::{TranspositionTable, TTABLE_SIZE}, zobrist::{ZobristSeed, Zobrist}};
+use self::{ttable::{TranspositionTable, TTABLE_SIZE}, zobrist::{ZobristSeed, Zobrist}, piece::Piece, color::Color};
 pub mod io;
+pub mod color;
+pub mod piece;
 mod zobrist;
 mod engine;
 mod ttable;
@@ -32,45 +34,6 @@ pub struct Board {
     attacks: Attacks,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, num_enum::FromPrimitive)]
-#[repr(usize)]
-pub enum PieceType {
-    #[default]
-    Pawn,
-    Knight,
-    Bishop,
-    Rook,
-    Queen,
-    King,
-    PawnBlack,
-    KnightBlack,
-    BishopBlack,
-    RookBlack,
-    QueenBlack,
-    KingBlack,
-}
-
-impl PieceType {
-    pub fn without_color(&self) -> Self {
-        let index = *self as usize;
-        Self::from(index % 6)
-    }
-    // Return the price of the peice
-    pub fn static_eval(&self) -> f32 {
-        match self.without_color() {
-            PieceType::Pawn => 1.0,
-            PieceType::Bishop => 3.3,
-            PieceType::Knight => 3.2,
-            PieceType::Rook => 5.0,
-            PieceType::Queen => 9.0,
-            PieceType::King => 0.,
-            _ => panic!("Piece should be without color"),
-        }
-    }
-}
-
-
-
 impl Board {
     pub fn new() -> Self {
         let default_fen = String::from("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1");
@@ -101,303 +64,18 @@ impl Board {
         self.pieces_by_color(color).iter().fold(0, |acc, bitboard| acc | bitboard)
     }
 
-
-
-    fn ep_bitboard(&self) -> Bitboard {
-        let color = self.color();
-        match self.ep_target {
-            Some(square) => {
-                let rank = square.rank();
-                if (rank == 2 && color == Color::Black) || (rank == 5 && color == Color::White) {
-                    square.to_bitboard()
-                } else {
-                    0
-                }
-            }
-            None => 0,
-        }
-    }
-
-    pub fn generate_pseudolegal_moves(&self) -> Vec<Move> {
-        let mut result = Vec::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) -> Vec<Move> {
-        let color = self.color();
-        let player_pieces = self.pieces_by_color(color);
-        let mut moves = Vec::with_capacity(256);
-        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[PieceType::KingBlack as usize],
-                Color::Black => self.piece_sets[PieceType::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 = PieceType::from(piece_id);
-                let move_targets = match piece_type {
-                    PieceType::Bishop => self.attacks.bishop(self.occupancy, source),
-                    PieceType::Rook => self.attacks.rook(self.occupancy, source),
-                    PieceType::Queen => self.attacks.queen(self.occupancy, source),
-                    PieceType::Knight => self.attacks.knight[source as usize],
-                    PieceType::King => self.attacks.king[source as usize],
-                    PieceType::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 == PieceType::Pawn {
-                        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)})
-                            }
-                        }
-                    }
-                }
-
-                // En Passant
-                if piece_type == PieceType::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[PieceType::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[PieceType::King as usize].bitscan() == king_home_position {
-                for rook_square in player_pieces[PieceType::Rook as usize]
-                    .serialize()
-                    .iter()
-                    .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,
-                                })
-                            }
-                        },
-                        _ => {},
-                    }
-                }
-            }
-        }
-        return moves
-    }
-
-    /// Count pseudo-legal moves without actually generating them
-    /// Also exclude all moves that put a piece under attack of a pawn - so called safe mobility
-    pub fn mobility(&self, color: Color) -> f32 {
-        let mut mobility = 0.;
-        let opponent_occupancy = self.color_occupancy(color.flip());
-        let player_pieces = self.pieces_by_color(color);
-
-        let opponent_pawns = match color {
-            Color::Black => self.piece_sets[PieceType::Pawn as usize],
-            Color::White => self.piece_sets[PieceType::PawnBlack as usize],
-        };
-
-        let pawn_attacked_squares = opponent_pawns.serialize().iter().fold(0u64, |acc, square| {
-            acc | self.attacks.pawn[color.flip() as usize][*square as usize]
-        });
-
-        // Exclude squares controlled by enemy pawns from mobility
-        let empty = self.empty() & !pawn_attacked_squares;
-
-        for (piece_type, piece) in player_pieces.iter().enumerate() {
-            match PieceType::from(piece_type) {
-                PieceType::Pawn => {
-                    for source in piece.serialize() {
-                        let ep_bitboard = match self.ep_target {
-                            Some(square) => {
-                                let rank = square.rank();
-                                if (rank == 2 && color == Color::Black) || (rank == 5 && color == Color::White) {
-                                    square.to_bitboard()
-                                } else {
-                                    0
-                                }
-                            }
-                            None => 0,
-                        };
-                        mobility += (self.attacks.pawn[color as usize][source as usize] & (opponent_occupancy | ep_bitboard)).pop_count() as f32;
-                        mobility += (self.attacks.pawn_pushes[color as usize][source as usize] & empty).pop_count() as f32;
-                    }
-                    let able_to_double_push_mask = match color {
-                        Color::White => empty >> 8,
-                        Color::Black => empty << 8,
-                    };
-                    for source in (*piece & able_to_double_push_mask).serialize() {
-                        mobility += (self.attacks.pawn_double_pushes[color as usize][source as usize] & empty).pop_count() as f32;
-                    }
-                }
-                PieceType::King => {
-                    for source in piece.serialize() {
-                        mobility += (self.attacks.king[source as usize] & (empty | opponent_occupancy)).pop_count() as f32;
-
-                        // Castling
-                        let king_home_position = match color {
-                            Color::White => Square::E1,
-                            Color::Black => Square::E8,
-                        };
-                        if *piece == king_home_position.to_bitboard() {
-                            for rook_square in player_pieces[PieceType::Rook as usize]
-                                .serialize()
-                                .iter()
-                                .filter(|rook_square| rook_square.rank() == king_home_position.rank())
-                                {
-                                    match rook_square.file() {
-                                        0 => {
-                                            let castle_line = [
-                                                king_home_position.west_one(),
-                                                king_home_position.west_one().west_one(),
-                                            ];
-
-                                            let all_empty = castle_line.iter().all(|square| empty & square.to_bitboard() > 0);
-                                            let any_checks = castle_line.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] {
-                                                mobility += 1.;
-                                            }
-                                        },
-                                        7 => {
-                                            let castle_line = [
-                                                king_home_position.east_one(),
-                                                king_home_position.east_one().east_one(),
-                                            ];
-
-                                            let all_empty = castle_line.iter().all(|square| empty & square.to_bitboard() > 0);
-                                            let any_checks = castle_line.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] {
-                                                mobility += 1.;
-                                            }
-                                        },
-                                        _ => {},
-                                    }
-                                }
-                        }
-                    }
-                }
-                PieceType::Knight => {
-                    for source in piece.serialize() {
-                        mobility += (self.attacks.knight[source as usize] & (empty | opponent_occupancy)).pop_count() as f32;
-                    }
-                }
-                PieceType::Bishop => {
-                    for source in piece.serialize() {
-                        mobility += (self.attacks.bishop(self.occupancy, source) & (empty | opponent_occupancy)).pop_count() as f32;
-                    }
-                }
-                PieceType::Rook => {
-                    for source in piece.serialize() {
-                        mobility += (self.attacks.rook(self.occupancy, source) & (empty | opponent_occupancy)).pop_count() as f32;
-                    }
-                }
-                PieceType::Queen => {
-                    // Do not account queen in mobility
-                }
-                incorrect_type => panic!("Incorrect piece type: {:?}", incorrect_type),
-            }
-        }
-
-        mobility
-    }
-
-    fn piece_by_square(&self, square: Square) -> Option<PieceType> {
+    fn piece_by_square(&self, square: Square) -> Option<Piece> {
         let square_bb = square.to_bitboard();
         self.piece_sets
             .iter()
             .enumerate()
             .find(|(_, bitboard)| *bitboard & square_bb > 0)
-            .and_then(|(pt, _)| Some(PieceType::from(pt)))
+            .and_then(|(pt, _)| Some(Piece::from(pt)))
     }
 
     /// *Blindlessly* apply a move without any validation
     /// Legality test should still be performed
-    pub fn make_move(&mut self, mov: Move) -> Option<PieceType> {
+    pub fn make_move(&mut self, mov: Move) -> Option<Piece> {
         let move_source_bb = mov.source.to_bitboard();
         let move_target_bb = mov.target.to_bitboard();
 
@@ -452,7 +130,7 @@ impl Board {
                         self.zobrist_toggle_piece(source_piece, mov.target);
                     }
                 }
-                PieceType::from(source_piece)
+                Piece::from(source_piece)
             },
             None => {
                 self.print();
@@ -502,13 +180,13 @@ impl Board {
         // Withdraw castling rights when moving rooks or king
         let source_color = Color::from_piece(source_piece);
         match source_piece.without_color() {
-            PieceType::King => {
+            Piece::King => {
                 self.castling_rights[source_color as usize][CastlingSide::King as usize] = false;
                 self.castling_rights[source_color as usize][CastlingSide::Queen as usize] = false;
                 self.zobrist_toggle_castling_right(source_color, CastlingSide::King);
                 self.zobrist_toggle_castling_right(source_color, CastlingSide::Queen);
             },
-            PieceType::Rook => {
+            Piece::Rook => {
                 match mov.source.file() {
                     0 => {
                         self.castling_rights[source_color as usize][CastlingSide::Queen as usize] = false;
@@ -534,7 +212,7 @@ impl Board {
     pub fn unmake_move(
         &mut self,
         mov: Move,
-        captured_piece: Option<PieceType>,
+        captured_piece: Option<Piece>,
         previous_ep_target: Option<Square>,
         previous_castling_rights: [[bool; 2]; 2],
         previous_hash: u64,
@@ -552,8 +230,8 @@ impl Board {
                         self.occupancy         ^= move_target_bb;
 
                         let source_id = match Color::from_piece(promotion_piece) {
-                            Color::White => PieceType::Pawn,
-                            Color::Black => PieceType::PawnBlack,
+                            Color::White => Piece::Pawn,
+                            Color::Black => Piece::PawnBlack,
                         } as usize;
 
                         self.piece_sets[source_id] |= move_source_bb;
@@ -626,33 +304,33 @@ impl Board {
 
     fn is_square_attacked(&self, square: Square, attacker_color: Color) -> bool {
         for (piece_type, piece) in self.pieces_by_color(attacker_color).iter().enumerate() {
-            match PieceType::from(piece_type) {
-                PieceType::Queen => {
+            match Piece::from(piece_type) {
+                Piece::Queen => {
                     if self.attacks.queen(self.occupancy, square) & piece > 0 {
                         return true
                     }
                 }
-                PieceType::Knight => {
+                Piece::Knight => {
                     if self.attacks.knight[square as usize] & piece > 0 {
                         return true
                     }
                 }
-                PieceType::Bishop => {
+                Piece::Bishop => {
                     if self.attacks.bishop(self.occupancy, square) & piece > 0 {
                         return true
                     }
                 }
-                PieceType::Rook => {
+                Piece::Rook => {
                     if self.attacks.rook(self.occupancy, square) & piece > 0 {
                         return true
                     }
                 }
-                PieceType::Pawn => {
+                Piece::Pawn => {
                     if self.attacks.pawn[attacker_color.flip() as usize][square as usize] & piece > 0 {
                         return true
                     }
                 }
-                PieceType::King => {
+                Piece::King => {
                     if self.attacks.king[square as usize] & piece > 0 {
                         return true
                     }
@@ -665,8 +343,8 @@ impl Board {
 
     fn is_king_in_check(&self, color: Color) -> bool {
         let king_bb = match color {
-            Color::White => self.piece_sets[PieceType::King as usize],
-            Color::Black => self.piece_sets[PieceType::KingBlack as usize],
+            Color::White => self.piece_sets[Piece::King as usize],
+            Color::Black => self.piece_sets[Piece::KingBlack as usize],
         };
         let square = king_bb.bitscan();
         self.is_square_attacked(square, color.flip())
@@ -674,33 +352,10 @@ impl Board {
 }
 
 
-#[derive(Debug, Clone, Copy, PartialEq, num_enum::FromPrimitive)]
-#[repr(u8)]
-pub enum Color {
-    #[default]
-    White,
-    Black,
-}
-impl Color {
-    pub fn flip(&self) -> Self {
-        match self {
-            Self::White => Self::Black,
-            Self::Black => Self::White,
-        }
-    }
-    pub fn from_piece(piece: PieceType) -> Self {
-        if (piece as u8) < 6 {
-            Self::White
-        } else {
-            Self::Black
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::{bitboard::BitboardFns, square::Square, board::zobrist::Zobrist};
+    use crate::{square::Square, board::zobrist::Zobrist};
 
     #[test]
     fn square_enum() {
@@ -710,36 +365,6 @@ mod tests {
     }
 
     #[test]
-    fn new_from_default_fen() {
-        let board = Board::new();
-
-        board.print();
-        board.empty().print("Empty squares");
-
-        assert_eq!(board.piece_sets[PieceType::Pawn as usize].pop_count(), 8);
-        assert_eq!(board.piece_sets[PieceType::Knight as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::Bishop as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::Rook as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::Queen as usize].pop_count(), 1);
-        assert_eq!(board.piece_sets[PieceType::King as usize].pop_count(), 1);
-
-        assert_eq!(board.piece_sets[PieceType::PawnBlack as usize].pop_count(), 8);
-        assert_eq!(board.piece_sets[PieceType::KnightBlack as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::BishopBlack as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::RookBlack as usize].pop_count(), 2);
-        assert_eq!(board.piece_sets[PieceType::QueenBlack as usize].pop_count(), 1);
-        assert_eq!(board.piece_sets[PieceType::KingBlack as usize].pop_count(), 1);
-
-        assert_eq!(board.piece_sets[PieceType::King as usize].bitscan(), Square::E1);
-        assert_eq!(board.piece_sets[PieceType::QueenBlack as usize].bitscan(), Square::D8);
-
-        assert_eq!(board.occupancy.pop_count(), 32);
-        assert_eq!(board.empty().pop_count(), 32);
-        assert_eq!(board.color_occupancy(Color::White).pop_count(), 16);
-        assert_eq!(board.color_occupancy(Color::Black).pop_count(), 16);
-    }
-
-    #[test]
     fn generate_pseudolegal_moves_starting_position() {
         let mut board = Board::new();
         let moves = board.generate_pseudolegal_moves();
@@ -785,23 +410,23 @@ mod tests {
         board.compute_hash();
         assert_eq!(hash, board.hash, "Hash should be correctly updated after move");
 
-        assert!(board.piece_sets[PieceType::PawnBlack as usize] & Square::F7.to_bitboard() == 0);
-        assert!(board.piece_sets[PieceType::PawnBlack as usize] & Square::F5.to_bitboard() > 0);
+        assert!(board.piece_sets[Piece::PawnBlack as usize] & Square::F7.to_bitboard() == 0);
+        assert!(board.piece_sets[Piece::PawnBlack as usize] & Square::F5.to_bitboard() > 0);
         assert!(board.ply == 1);
 
         let white_move = Move { source: Square::D2, target: Square::A5, kind: MoveKind::Capture };
         println!("\n{:?}", white_move);
 
         match board.make_move(white_move) {
-            Some(captured) => assert!(captured == PieceType::PawnBlack),
+            Some(captured) => assert!(captured == Piece::PawnBlack),
             None => panic!("A piece should be captured"),
         };
 
         board.print();
 
-        assert!(board.piece_sets[PieceType::PawnBlack as usize] & Square::A5.to_bitboard() == 0, "Target piece should be captured");
-        assert!(board.piece_sets[PieceType::Queen as usize] & Square::D2.to_bitboard() == 0);
-        assert!(board.piece_sets[PieceType::Queen as usize] & Square::A5.to_bitboard() > 0);
+        assert!(board.piece_sets[Piece::PawnBlack as usize] & Square::A5.to_bitboard() == 0, "Target piece should be captured");
+        assert!(board.piece_sets[Piece::Queen as usize] & Square::D2.to_bitboard() == 0);
+        assert!(board.piece_sets[Piece::Queen as usize] & Square::A5.to_bitboard() > 0);
         assert_ne!(board.occupancy, initial_board.occupancy, "Occupancy should change after make_move");
         assert!(board.ply == 2);
     }