Make new fn's to update the State struct

src/game.rs

@@ -71,6 +71,46 @@ impl State {
         self.en_passant_target_square
     }
 
+    pub fn set_castling_ability(&mut self, color: Color, castle: Castle) {
+        match color {
+            Color::White => self.castling_ability[0] = castle,
+            Color::Black => self.castling_ability[1] = castle,
+        }
+    }
+
+    pub fn update_castling_state(&mut self, square: u8, color: Color) {
+        if square == 0 || square == 7 {
+            match (color, self.get_castling_ability(color)) {
+                (_, Castle::Both) => self.set_castling_ability(color, Castle::Long),
+                (_, Castle::Short) => self.set_castling_ability(color, Castle::None),
+                _ => (),
+            }
+        }
+
+        if square == 56 || square == 63 {
+            match (color, self.get_castling_ability(color)) {
+                (_, Castle::Both) => self.set_castling_ability(color, Castle::Short),
+                (_, Castle::Short) => self.set_castling_ability(color, Castle::None),
+                _ => (),
+            }
+        }
+
+        if square == 4 || square == 60 {
+            self.set_castling_ability(color, Castle::None)
+        }
+    }
+
+    pub fn next_turn(&mut self) {
+        self.side_to_move = match self.side_to_move {
+            Color::White => Color::Black,
+            Color::Black => Color::White,
+        }
+    }
+
+    pub fn set_en_passant_target_square(&mut self, sq: Option<u8>) {
+        self.en_passant_target_square = sq;
+    }
+
     pub const fn get_castling_ability(&self, color: Color) -> Castle {
         match color {
             Color::White => self.castling_ability[0],