feat: implement quiscence

1 files changed, 36 insertions, 0 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index ff071ea..dcb3646 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -133,6 +133,42 @@ impl Board {
         (alpha, principal_variation)
     }
 
+    pub fn quiscence(&mut self, mut alpha: f32, beta: f32) -> f32 {
+        let color = self.color();
+        let stand_pat = self.material_advantage();
+
+        if stand_pat >= beta {
+            return beta;
+        }
+        if alpha < stand_pat {
+            alpha = stand_pat;
+        }
+
+        let moves = self.generate_pseudolegal_moves(color);
+        let tactical_moves = moves.iter().filter(|m| m.kind == MoveKind::Capture || m.kind == MoveKind::EnPassant);
+
+        for mov in tactical_moves {
+            let ep_target_before = self.ep_target.clone();
+            let castling_rights_before = self.castling_rights.clone();
+            let captured_piece = self.make_move(*mov);
+
+            if !self.is_king_in_check(color) {
+                let evaluation = -self.quiscence(-beta, -alpha);
+                self.unmake_move(*mov, captured_piece, ep_target_before, castling_rights_before);
+
+                if evaluation >= beta {
+                    return beta; // Fail-hard beta-cutoff
+                }
+                if evaluation > alpha {
+                    alpha = evaluation;
+                }
+            } else {
+                self.unmake_move(*mov, captured_piece, ep_target_before, castling_rights_before);
+            }
+        }
+
+        alpha
+    }
 }