feat: Implement threefold repetition detection and update game rules

modules/rule/CHANGELOG.md

@@ -44,3 +44,14 @@
 ### Bug Fixes
 
 * NCS-32 Queenside Castle doesn't care about pieces in the way ([#23](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/23)) ([fe8e3c0](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fe8e3c05397f433bfa34d1999e9738c82790adf7))
+##  (2026-04-16)
+
+### Features
+
+* NCS-13 Implement Threefold Repetition ([#31](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/31)) ([767d305](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/767d3051a76c266050b6335774d66e2db2273c16))
+* NCS-14 implemented insufficient moves rule ([#30](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/30)) ([b0399a4](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/b0399a4e489950083066c9538df9a84dcc7a4613))
+* NCS-25 Add linters to keep quality up ([#27](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/27)) ([fd4e67d](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fd4e67d4f782a7e955822d90cb909d0a81676fb2))
+
+### Bug Fixes
+
+* NCS-32 Queenside Castle doesn't care about pieces in the way ([#23](https://git.janis-eccarius.de/NowChess/NowChessSystems/issues/23)) ([fe8e3c0](https://git.janis-eccarius.de/NowChess/NowChessSystems/commit/fe8e3c05397f433bfa34d1999e9738c82790adf7))

modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala

@@ -458,18 +458,11 @@ object DefaultRules extends RuleSet:
   private def squareColor(sq: Square): Int = (sq.file.ordinal + sq.rank.ordinal) % 2
 
   private def insufficientMaterial(board: Board): Boolean =
-    val nonKings = board.pieces.toList.filter(_._2.pieceType != PieceType.King)
+    val nonKings = board.pieces.toList.filter { case (_, p) => p.pieceType != PieceType.King }
     nonKings match
-      case Nil => true
+      case Nil                                                                                => true
       case List((_, p)) if p.pieceType == PieceType.Bishop || p.pieceType == PieceType.Knight => true
-      case List((sq1, p1), (sq2, p2))
-          if p1.pieceType == PieceType.Bishop && p2.pieceType == PieceType.Bishop
-            && p1.color != p2.color
-            && squareColor(sq1) == squareColor(sq2) =>
-        true
-      case bishops
-          if bishops.forall(_._2.pieceType == PieceType.Bishop)
-            && bishops.map(_._2.color).distinct.size == 1
-            && bishops.map(e => squareColor(e._1)).distinct.size == 1 =>
-        true
+      case bishops if bishops.forall { case (_, p) => p.pieceType == PieceType.Bishop }       =>
+        // All non-king pieces are bishops: draw only if they all share the same square color
+        bishops.map { case (sq, _) => squareColor(sq) }.distinct.sizeIs == 1
       case _ => false

modules/rule/src/test/scala/de/nowchess/rule/DefaultRulesTest.scala

@@ -29,15 +29,10 @@ class DefaultRulesTest extends AnyFunSuite with Matchers:
 
   test("pawn can capture diagonally"):
     // FEN: white pawn e4, black pawn d5
-    val fen     = "8/8/8/3p4/4P3/8/8/8 w - - 0 1"
-    val context = FenParser.parseFen(fen).fold(_ => fail(), identity)
-    val moves   = rules.allLegalMoves(context)
-    val captures = moves.filter { m =>
-      m.from == Square(File.E, Rank.R4) && (m.moveType match
-        case _: MoveType.Normal => true
-        case _                  => false
-      )
-    }
+    val fen      = "8/8/8/3p4/4P3/8/8/8 w - - 0 1"
+    val context  = FenParser.parseFen(fen).fold(_ => fail(), identity)
+    val moves    = rules.allLegalMoves(context)
+    val captures = moves.filter(m => m.from == Square(File.E, Rank.R4) && (m.moveType match { case _: MoveType.Normal => true; case _ => false }))
     captures.exists(m => m.to == Square(File.D, Rank.R5)) shouldBe true
 
   test("pawn cannot move backward"):

modules/rule/versions.env

@@ -1,3 +1,3 @@
 MAJOR=0
-MINOR=2
+MINOR=3
 PATCH=0