Make en_passant_square an Option<u8>

src/board.rs

@@ -121,7 +121,7 @@ impl Board {
                 pieces,
                 all_occupancies,
                 enemy_occupancies,
-                self.state,
+                self.state.get_en_passant_target_square(),
                 color,
             ),
             Kind::Knight => knight_pseudo_moves(pieces, own_occupancies),

src/fen.rs

@@ -101,7 +101,7 @@ fn castling_ability(castling: &str) -> Result<u8, FenError> {
 
 use std::collections::HashMap;
 
-fn en_passant_target_square(square: &str) -> Result<u8, FenError> {
+fn en_passant_target_square(square: &str) -> Result<Option<u8>, FenError> {
     let mut sqr = square.chars();
 
     let mut files: HashMap<char, u8> = HashMap::new();
@@ -120,14 +120,15 @@ fn en_passant_target_square(square: &str) -> Result<u8, FenError> {
 
     match sqr.next() {
         Some(file) if files.contains_key(&file) => match sqr.next() {
-            Some(rank) if ranks.contains_key(&rank) => Ok(ranks.get(&rank).expect("Invalid rank")
+            Some(rank) if ranks.contains_key(&rank) => Ok(Some(
-                * 8
+                ranks.get(&rank).expect("Invalid rank") * 8
-                + files.get(&file).expect("Invalid file")),
+                    + files.get(&file).expect("Invalid file"),
+            )),
             Some(_) | None => Err(FenError::from(
                 "Not a valid rank (3 or 6) for an en passant target square",
             )),
         },
-        Some('-') => Ok(0),
+        Some('-') => Ok(None),
         Some(_) | None => Err(FenError::from("Not a file (a..h) or dash (-) character")),
     }
 }

src/game.rs

@@ -35,7 +35,7 @@ impl Default for Game {
 pub struct State {
     side_to_move: Color,
     castling_ability: u8,
-    en_passant_target_square: u8,
+    en_passant_target_square: Option<u8>,
     halfmove_clock: u8,
     fullmove_counter: u8,
 }
@@ -45,7 +45,7 @@ impl State {
         Self {
             side_to_move: Color::White,
             castling_ability: 0b1111,
-            en_passant_target_square: 0,
+            en_passant_target_square: None,
             halfmove_clock: 0,
             fullmove_counter: 1,
         }
@@ -54,7 +54,7 @@ impl State {
     pub const fn load_state(
         side_to_move: Color,
         castling_ability: u8,
-        en_passant_target_square: u8,
+        en_passant_target_square: Option<u8>,
         halfmove_clock: u8,
         fullmove_counter: u8,
     ) -> Self {
@@ -67,7 +67,7 @@ impl State {
         }
     }
 
-    pub const fn get_en_passant_target_square(&self) -> u8 {
+    pub const fn get_en_passant_target_square(&self) -> Option<u8> {
         self.en_passant_target_square
     }
 }
@@ -78,7 +78,7 @@ impl fmt::Display for State {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         writeln!(f,
             "side_to_move: {:?}\ncastling_ability: {:b}\nen_passant_target_square: {:b}\nhalfmove_clock: {}\nfullmove_counter: {}\n",
-            self.side_to_move, self.castling_ability, 1_u64 << self.en_passant_target_square, self.halfmove_clock, self.fullmove_counter)
+            self.side_to_move, self.castling_ability, 1_u64 << self.en_passant_target_square.unwrap_or(0), self.halfmove_clock, self.fullmove_counter)
     }
 }
 

src/movegen.rs

@@ -3,7 +3,6 @@ use crate::attack::{
     get_rook_attacks,
 };
 use crate::board::Color;
-use crate::game::State;
 use u64 as Bitboard;
 
 const NOT_A_FILE: Bitboard = 0xfefefefefefefefe;
@@ -27,17 +26,25 @@ pub fn pawn_pseudo_moves(
     pawns: Bitboard,
     all_occupancies: Bitboard,
     enemy_occupancies: Bitboard,
-    state: State,
+    en_passant_square: Option<u8>,
     color: Color,
 ) -> Vec<Move> {
     let mut moves: Vec<Move> = vec![];
     match color {
         Color::White => {
             moves.extend(white_pawn_quiet_moves(pawns, all_occupancies));
-            moves.extend(white_pawn_capture_moves(pawns, enemy_occupancies, state));
+            moves.extend(white_pawn_capture_moves(
+                pawns,
+                enemy_occupancies,
+                en_passant_square,
+            ));
         }
         Color::Black => {
-            moves.extend(black_pawn_capture_moves(pawns, enemy_occupancies, state));
+            moves.extend(black_pawn_capture_moves(
+                pawns,
+                enemy_occupancies,
+                en_passant_square,
+            ));
             moves.extend(black_pawn_quiet_moves(pawns, all_occupancies));
         }
     }
@@ -91,7 +98,7 @@ fn black_pawn_quiet_moves(pawns: Bitboard, occupancies: Bitboard) -> Vec<Move> {
 fn white_pawn_capture_moves(
     pawns: Bitboard,
     enemy_occupancies: Bitboard,
-    state: State,
+    en_passant_square: Option<u8>,
 ) -> Vec<Move> {
     let mut moves: Vec<Move> = vec![];
     let mut w_pawns_capture_east = pawns & ((enemy_occupancies >> 9) & NOT_H_FILE);
@@ -110,19 +117,18 @@ fn white_pawn_capture_moves(
         w_pawns_capture_west &= w_pawns_capture_west - 1;
     }
 
-    let epts = state.get_en_passant_target_square();
+    if let Some(en_passant_square) = en_passant_square {
-    if epts != 0 {
+        let attacked_from = get_pawn_attacks(en_passant_square as usize, Color::Black);
-        let attacked_from = get_pawn_attacks(epts as usize, Color::Black);
         let result = attacked_from & pawns;
-        moves.push(Move::new(result.trailing_zeros(), epts as u32));
+        moves.push(Move::new(result.trailing_zeros(), en_passant_square as u32));
-    }
+    };
     moves
 }
 
 fn black_pawn_capture_moves(
     pawns: Bitboard,
     enemy_occupancies: Bitboard,
-    state: State,
+    en_passant_square: Option<u8>,
 ) -> Vec<Move> {
     let mut moves: Vec<Move> = vec![];
     let mut b_pawns_capture_east = pawns & ((enemy_occupancies << 7) & NOT_H_FILE);
@@ -142,12 +148,11 @@ fn black_pawn_capture_moves(
         b_pawns_capture_west &= b_pawns_capture_west - 1;
     }
 
-    let epts = state.get_en_passant_target_square();
+    if let Some(en_passant_square) = en_passant_square {
-    if epts != 0 {
+        let attacked_from = get_pawn_attacks(en_passant_square as usize, Color::White);
-        let attacked_from = get_pawn_attacks(epts as usize, Color::White);
         let result = attacked_from & pawns;
-        moves.push(Move::new(result.trailing_zeros(), epts as u32));
+        moves.push(Move::new(result.trailing_zeros(), en_passant_square as u32));
-    }
+    };
     moves
 }
 
@@ -190,7 +195,6 @@ pub fn bishop_pseudo_moves(
         bishops &= bishops - 1;
     }
     moves
-    // moves arkoudaki se agapo polu! to gataki sou
 }
 
 pub fn rook_pseudo_moves(