[board] Move position flags to a Flags struct in its own module

board/src/position/flags.rs

@@ -0,0 +1,73 @@
+// Eryn Wells <eryn@erynwells.me>
+
+use super::position::BoardSide;
+use crate::piece::Color;
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub(super) struct Flags(u8);
+
+impl Flags {
+    #[inline]
+    pub(super) fn player_has_right_to_castle_flag_offset(color: Color, side: BoardSide) -> u8 {
+        ((color as u8) << 1) + side as u8
+    }
+
+    pub(super) fn player_has_right_to_castle(&self, color: Color, side: BoardSide) -> bool {
+        (self.0 & (1 << Self::player_has_right_to_castle_flag_offset(color, side))) != 0
+    }
+
+    pub(super) fn set_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
+        self.0 |= 1 << Self::player_has_right_to_castle_flag_offset(color, side);
+    }
+
+    pub(super) fn clear_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
+        self.0 &= !(1 << Self::player_has_right_to_castle_flag_offset(color, side));
+    }
+}
+
+impl Default for Flags {
+    fn default() -> Self {
+        Flags(0b00001111)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::Color;
+
+    #[test]
+    fn castle_flags() {
+        assert_eq!(
+            Flags::player_has_right_to_castle_flag_offset(Color::White, BoardSide::King),
+            0
+        );
+        assert_eq!(
+            Flags::player_has_right_to_castle_flag_offset(Color::White, BoardSide::Queen),
+            1
+        );
+        assert_eq!(
+            Flags::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::King),
+            2
+        );
+        assert_eq!(
+            Flags::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::Queen),
+            3
+        );
+    }
+
+    #[test]
+    fn defaults() {
+        let mut flags: Flags = Default::default();
+        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::King));
+        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::Queen));
+        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::King));
+        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::Queen));
+
+        flags.clear_player_has_right_to_castle_flag(Color::White, BoardSide::Queen);
+        assert!(flags.player_has_right_to_castle(Color::White, BoardSide::King));
+        assert!(!flags.player_has_right_to_castle(Color::White, BoardSide::Queen));
+        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::King));
+        assert!(flags.player_has_right_to_castle(Color::Black, BoardSide::Queen));
+    }
+}

board/src/position/mod.rs

@@ -1,6 +1,7 @@
 // Eryn Wells <eryn@erynwells.me>
 
 mod diagram_formatter;
+mod flags;
 mod pieces;
 mod position;
 

board/src/position/position.rs

@@ -1,6 +1,6 @@
 // Eryn Wells <eryn@erynwells.me>
 
-use super::Pieces;
+use super::{flags::Flags, Pieces};
 use crate::{
     bitboard::BitBoard,
     moves::Moves,
@@ -38,7 +38,7 @@ pub struct Position {
     /// 1. white can castle queen-side
     /// 2. black can castle king-side
     /// 3. black can castle queen-side
-    flags: u8,
+    flags: Flags,
 
     /// Composite bitboards for all the pieces of a particular color.
     pieces_per_color: [BitBoard; 2],
@@ -51,7 +51,7 @@ impl Position {
     pub fn empty() -> Position {
         Position {
             color_to_move: Color::White,
-            flags: 0b00001111,
+            flags: Default::default(),
             pieces_per_color: [BitBoard::empty(); 2],
             pieces_per_type: [
                 [
@@ -96,7 +96,7 @@ impl Position {
 
         Position {
             color_to_move: Color::White,
-            flags: 0b00001111,
+            flags: Default::default(),
             pieces_per_color: [
                 white_pieces.iter().fold(BitBoard::empty(), |a, b| a | *b),
                 black_pieces.iter().fold(BitBoard::empty(), |a, b| a | *b),
@@ -119,20 +119,16 @@ impl Position {
     /// 3. In the course of castling on that side, the king must not pass
     ///    through a square that an enemy piece can see
     pub(crate) fn player_has_right_to_castle(&self, color: Color, side: BoardSide) -> bool {
-        (self.flags & (1 << Self::player_has_right_to_castle_flag_offset(color, side))) != 0
+        self.flags.player_has_right_to_castle(color, side)
     }
 
     fn set_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
-        self.flags |= 1 << Self::player_has_right_to_castle_flag_offset(color, side);
+        self.flags.set_player_has_right_to_castle_flag(color, side);
     }
 
     fn clear_player_has_right_to_castle_flag(&mut self, color: Color, side: BoardSide) {
-        self.flags &= !(1 << Self::player_has_right_to_castle_flag_offset(color, side));
+        self.flags
-    }
+            .clear_player_has_right_to_castle_flag(color, side);
-
-    #[inline]
-    fn player_has_right_to_castle_flag_offset(color: Color, side: BoardSide) -> u8 {
-        ((color as u8) << 1) + side as u8
     }
 
     pub fn place_piece(&mut self, piece: Piece, square: Square) -> Result<(), PiecePlacementError> {
@@ -277,34 +273,6 @@ mod tests {
     }
 
     #[test]
-    fn castle_flags() {
-        assert_eq!(
-            Position::player_has_right_to_castle_flag_offset(Color::White, BoardSide::King),
-            0
-        );
-        assert_eq!(
-            Position::player_has_right_to_castle_flag_offset(Color::White, BoardSide::Queen),
-            1
-        );
-        assert_eq!(
-            Position::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::King),
-            2
-        );
-        assert_eq!(
-            Position::player_has_right_to_castle_flag_offset(Color::Black, BoardSide::Queen),
-            3
-        );
 
-        let mut pos = Position::starting();
-        assert!(pos.player_has_right_to_castle(Color::White, BoardSide::King));
-        assert!(pos.player_has_right_to_castle(Color::White, BoardSide::Queen));
-        assert!(pos.player_has_right_to_castle(Color::Black, BoardSide::King));
-        assert!(pos.player_has_right_to_castle(Color::Black, BoardSide::Queen));
-
-        pos.clear_player_has_right_to_castle_flag(Color::White, BoardSide::Queen);
-        assert!(pos.player_has_right_to_castle(Color::White, BoardSide::King));
-        assert!(!pos.player_has_right_to_castle(Color::White, BoardSide::Queen));
-        assert!(pos.player_has_right_to_castle(Color::Black, BoardSide::King));
-        assert!(pos.player_has_right_to_castle(Color::Black, BoardSide::Queen));
     }
 }