Add board.ForceSkipTurn() to skip a turn even when in check (use at o…

…wn peril)
SebLague · Jul 26, 2023 · 0d6abe1 · 0d6abe1
1 parent 779c7f8
commit 0d6abe1
Showing 1 changed file with 23 additions and 7 deletions.
diff --git a/Chess-Challenge/src/API/Board.cs b/Chess-Challenge/src/API/Board.cs
@@ -97,9 +97,10 @@ public void UndoMove(Move move)
 		}
 
 		/// <summary>
-		/// Try skip the current turn
-		/// This will fail and return false if in check
-		/// Note: skipping a turn is not allowed in the game, but it can be used as a search technique
+		/// Try skip the current turn.
+		/// This will fail and return false if in check.
+		/// Note: skipping a turn is not allowed in the game, but it can be used as a search technique.
+		/// Skipped turns can be undone with UndoSkipTurn()
 		/// </summary>
 		public bool TrySkipTurn()
 		{
@@ -113,10 +114,25 @@ public bool TrySkipTurn()
 			return true;
 		}
 
-		/// <summary>
-		/// Undo a turn that was succesfully skipped with the TrySkipTurn method
-		/// </summary>
-		public void UndoSkipTurn()
+        /// <summary>
+        /// Forcibly skips the current turn.
+		/// Unlike TrySkipTurn(), this will work even when in check, which has some dangerous side-effects if done:
+		/// 1) Generating 'legal' moves will now include the illegal capture of the king.
+		/// 2) If the skipped turn is undone, the board will now incorrectly report that the position is not check.
+        /// Note: skipping a turn is not allowed in the game, but it can be used as a search technique.
+		/// Skipped turns can be undone with UndoSkipTurn()
+        /// </summary>
+        public void ForceSkipTurn()
+        {
+            hasCachedMoves = false;
+            hasCachedCaptureMoves = false;
+            board.MakeNullMove();
+        }
+
+        /// <summary>
+        /// Undo a turn that was succesfully skipped with TrySkipTurn() or ForceSkipTurn()
+        /// </summary>
+        public void UndoSkipTurn()
 		{
 			hasCachedMoves = false;
 			hasCachedCaptureMoves = false;