feat: add castle to zobrist make_move

1 files changed, 29 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
index a920cfd..360a4e8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -49,6 +49,35 @@ long hash_after_move(Move move, int* board, long* zobrist_seed, long hash) {
   hash ^= zobrist_seed[piece * 128 + move.destination]; // Add piece to destination
   hash ^= zobrist_seed[target_piece * 128 + move.destination]; // Remove target piece from destination
 
+  if ((piece & NO_COLOR) == KING && abs(move.destination - move.origin) == 2) {
+    // CASTLE!
+    if (move.destination == 2) {
+      int rook = board[0];
+      hash ^= zobrist_seed[rook * 128 + 0]; // Rook is no longer on 0
+      hash ^= zobrist_seed[EMPTY * 128 + 0]; // Empty square on 0
+      hash ^= zobrist_seed[EMPTY * 128 + 3]; // Square 3 is not empty anymore
+      hash ^= zobrist_seed[rook * 128 + 3]; // Rook is now on 3
+    } else if (move.destination == 6) {
+      int rook = board[7];
+      hash ^= zobrist_seed[rook * 128 + 7];
+      hash ^= zobrist_seed[EMPTY * 128 + 7];
+      hash ^= zobrist_seed[EMPTY * 128 + 5];
+      hash ^= zobrist_seed[rook * 128 + 5];
+    } else if (move.destination == 114) {
+      int rook = board[112];
+      hash ^= zobrist_seed[rook * 128 + 112];
+      hash ^= zobrist_seed[EMPTY * 128 + 112];
+      hash ^= zobrist_seed[EMPTY * 128 + 115];
+      hash ^= zobrist_seed[rook * 128 + 115];
+    } else if (move.destination == 118) {
+      int rook = board[119];
+      hash ^= zobrist_seed[rook * 128 + 119];
+      hash ^= zobrist_seed[EMPTY * 128 + 119];
+      hash ^= zobrist_seed[EMPTY * 128 + 117];
+      hash ^= zobrist_seed[rook * 128 + 117];
+    }
+  }
+
   return hash;
 }