From c5949fb01e4a68b5e27a96ee48ca8f850abfa524 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Mon, 18 Jul 2022 13:35:31 +0200
Subject: [PATCH] Add 'CastleRights::without_{king,queen}_side'

---
 src/board/castle_rights.rs | 59 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/src/board/castle_rights.rs b/src/board/castle_rights.rs
index 10a602e..9663bc0 100644
--- a/src/board/castle_rights.rs
+++ b/src/board/castle_rights.rs
@@ -43,6 +43,25 @@ impl CastleRights {
     pub fn has_queen_side(self) -> bool {
         (self.index() & 2) != 0
     }
+
+    /// Remove king-side castling rights.
+    #[inline(always)]
+    pub fn without_king_side(self) -> Self {
+        self.remove(Self::KingSide)
+    }
+
+    /// Remove queen-side castling rights.
+    #[inline(always)]
+    pub fn without_queen_side(self) -> Self {
+        self.remove(Self::QueenSide)
+    }
+
+    /// Remove some [CastleRights], and return the resulting [CastleRights].
+    #[inline(always)]
+    pub fn remove(self, to_remove: CastleRights) -> Self {
+        // SAFETY: we know the value is in-bounds
+        unsafe { Self::from_index_unchecked(self.index() & !to_remove.index()) }
+    }
 }
 
 #[cfg(test)]
@@ -80,4 +99,44 @@ mod test {
         assert!(CastleRights::QueenSide.has_queen_side());
         assert!(CastleRights::BothSides.has_queen_side());
     }
+
+    #[test]
+    fn without_king_side() {
+        assert_eq!(
+            CastleRights::NoSide.without_king_side(),
+            CastleRights::NoSide
+        );
+        assert_eq!(
+            CastleRights::KingSide.without_king_side(),
+            CastleRights::NoSide
+        );
+        assert_eq!(
+            CastleRights::QueenSide.without_king_side(),
+            CastleRights::QueenSide
+        );
+        assert_eq!(
+            CastleRights::BothSides.without_king_side(),
+            CastleRights::QueenSide
+        );
+    }
+
+    #[test]
+    fn without_queen_side() {
+        assert_eq!(
+            CastleRights::NoSide.without_queen_side(),
+            CastleRights::NoSide
+        );
+        assert_eq!(
+            CastleRights::QueenSide.without_queen_side(),
+            CastleRights::NoSide
+        );
+        assert_eq!(
+            CastleRights::KingSide.without_queen_side(),
+            CastleRights::KingSide
+        );
+        assert_eq!(
+            CastleRights::BothSides.without_queen_side(),
+            CastleRights::KingSide
+        );
+    }
 }