From fcc0dc87f04403c8073ab769d3046d32342e6c2a Mon Sep 17 00:00:00 2001
From: Adam <adammegarules1@gmail.com>
Date: Tue, 18 Aug 2026 14:22:55 +0200
Subject: featuare(fen): validating king counts before accepting fen string

---
 src/board/fen.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'src/board/fen.cpp')

diff --git a/src/board/fen.cpp b/src/board/fen.cpp
index e020e78..f44719a 100644
--- a/src/board/fen.cpp
+++ b/src/board/fen.cpp
@@ -2,8 +2,10 @@
 #include "board.hpp"
 #include <cassert>
 #include <cctype>
+#include <cstdint>
 #include <cstdlib>
 #include <cstring>
+#include <iostream>
 #include <print>
 #include <string>
 #include <sys/types.h>
@@ -185,5 +187,18 @@ void setBoardFen(const std::string &fen, Game *g) {
     break;
   }
   g->enPassant = enpassant;
+
   updateBitboards(g);
+
+  int whiteKingCount = __builtin_popcountll(g->PieceBitboards[true][KING]);
+  int blackKingCount = __builtin_popcountll(g->PieceBitboards[false][KING]);
+
+  if (whiteKingCount != 1) {
+    std::cerr << "ERROR: expected exactly one white king\n";
+    exit(1);
+  }
+  if (blackKingCount != 1) {
+    std::cerr << "ERROR: expected exactly one black king\n";
+    exit(1);
+  }
 }
-- 
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