From 21a2a37e1f843684aa589c809db23df441c01edb Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Wed, 2 Jul 2025 18:30:13 -0700
Subject: [PATCH] [board] Implement Board::is_king_attacked_from_square

Calculate whether the active color's king is attacked from the provided Square.
---
 board/src/check.rs | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/board/src/check.rs b/board/src/check.rs
index 6d8ceba..e905498 100644
--- a/board/src/check.rs
+++ b/board/src/check.rs
@@ -2,19 +2,34 @@
 
 use crate::Board;
 use chessfriend_bitboard::BitBoard;
-use chessfriend_core::{Color, Piece};
+use chessfriend_core::{Color, Piece, Square};
 
 impl Board {
     /// Return whether the active color is in check.
     #[must_use]
     pub fn is_in_check(&self) -> bool {
         let color = self.active_color();
-        let king = self.king_bitboard(color);
+        let king = self.king_bitboard_active();
         let opposing_sight = self.opposing_sight(color);
         (king & opposing_sight).is_populated()
     }
 
-    fn king_bitboard(&self, color: Color) -> BitBoard {
+
+    fn is_king_attacked_from_square(&self, square: Square) -> bool {
+        let active_king = self.king_bitboard_active();
+        let sight_from_square = self.sight_piece(square);
+        (active_king & sight_from_square).is_populated()
+    }
+
+    fn king_bitboard(&self, color: Option<Color>) -> BitBoard {
+        self.king_bitboard_unwrapped(self.unwrap_color(color))
+    }
+
+    fn king_bitboard_active(&self) -> BitBoard {
+        self.king_bitboard_unwrapped(self.active_color())
+    }
+
+    fn king_bitboard_unwrapped(&self, color: Color) -> BitBoard {
         self.find_pieces(Piece::king(color))
     }
 }
@@ -22,7 +37,7 @@ impl Board {
 #[cfg(test)]
 mod tests {
     use crate::test_board;
-    use chessfriend_core::Color;
+    use chessfriend_core::Square;
 
     #[test]
     fn active_color_is_in_check() {
@@ -43,4 +58,17 @@ mod tests {
 
         assert!(!board.is_in_check());
     }
+
+    #[test]
+    fn king_is_attacked_from_square() {
+        let board = test_board!(
+            White King on D3,
+            Black Rook on H3,
+            Black Queen on F4
+        );
+
+        assert!(board.is_king_attacked_from_square(Square::H3));
+        assert!(!board.is_king_attacked_from_square(Square::F4));
+        assert!(!board.is_king_attacked_from_square(Square::A3));
+    }
 }