perf(core): reduce inter-service HTTP calls from 11 to 4 per move

- Add `postMoveStatus` batch method to `RuleSet` trait (default impl composes
  individual calls; `RuleSetRestAdapter` overrides with single HTTP round-trip)
- Collapse 5 sequential rule checks in `GameEngine.executeMove` into one
  `postMoveStatus` call
- Add `POST /api/rules/post-move-status` endpoint to rule-service
- Add `exportCombined` to `IoServiceClient` and `POST /io/export/combined`
  endpoint to io-service, replacing two separate FEN/PGN HTTP calls
- Fix `statusOf` to pattern-match on `WinReason` from `ctx.result` instead
  of making a redundant `isCheckmate` HTTP call
- Remove duplicate `legalMoves` pre-validation in `GameResource.makeMove`;
  engine already validates and fires `InvalidMoveEvent`
- Add `scalafix:off` guards for pre-existing `var`/`return` usage in
  `DefaultRules` hot-path code
- Apply spotless formatting to previously unformatted files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/account/src/main/scala/de/nowchess/account/config/NativeReflectionConfig.scala

@@ -13,7 +13,6 @@ import io.quarkus.runtime.annotations.RegisterForReflection
     classOf[ChallengeStatus],
     classOf[DeclineReason],
     classOf[TimeControl],
-    
     classOf[LoginRequest],
     classOf[TokenResponse],
     classOf[PlayerInfo],
@@ -27,7 +26,6 @@ import io.quarkus.runtime.annotations.RegisterForReflection
     classOf[ChallengeStatus],
     classOf[ChallengeColor],
     classOf[DeclineReason],
-
     classOf[CorePlayerInfo],
     classOf[CoreTimeControl],
     classOf[CoreCreateGameRequest],

modules/account/src/main/scala/de/nowchess/account/repository/AccountRepository.scala

@@ -40,7 +40,4 @@ class AccountRepository:
       .headOption
 
   def findAll(): List[Account] =
-    em.createQuery("FROM Account", classOf[Account])
-      .getResultList
-      .asScala
-      .toList
+    em.createQuery("FROM Account", classOf[Account]).getResultList.asScala.toList

modules/account/src/main/scala/de/nowchess/account/service/AccountService.scala

@@ -24,10 +24,8 @@ class AccountService:
 
   @Transactional
   def register(req: RegisterRequest): Either[AccountError, Account] =
-    if accountRepository.findByUsername(req.username).isDefined then
-      Left(AccountError.UsernameTaken(req.username))
-    else if accountRepository.findByEmail(req.email).isDefined then
-      Left(AccountError.EmailAlreadyRegistered(req.email))
+    if accountRepository.findByUsername(req.username).isDefined then Left(AccountError.UsernameTaken(req.username))
+    else if accountRepository.findByEmail(req.email).isDefined then Left(AccountError.EmailAlreadyRegistered(req.email))
     else
       val account = new Account()
       account.username = req.username

modules/account/src/main/scala/de/nowchess/account/service/ChallengeService.scala

@@ -1,8 +1,21 @@
 package de.nowchess.account.service
 
-import de.nowchess.account.client.{CoreCreateGameRequest, CoreGameClient, CoreGameResponse, CorePlayerInfo, CoreTimeControl}
+import de.nowchess.account.client.{
+  CoreCreateGameRequest,
+  CoreGameClient,
+  CoreGameResponse,
+  CorePlayerInfo,
+  CoreTimeControl,
+}
 import de.nowchess.account.domain.{Challenge, ChallengeColor, ChallengeStatus, DeclineReason}
-import de.nowchess.account.dto.{ChallengeDto, ChallengeListDto, ChallengeRequest, DeclineRequest, PlayerInfo, TimeControlDto}
+import de.nowchess.account.dto.{
+  ChallengeDto,
+  ChallengeListDto,
+  ChallengeRequest,
+  DeclineRequest,
+  PlayerInfo,
+  TimeControlDto,
+}
 import de.nowchess.account.error.ChallengeError
 import de.nowchess.account.repository.{AccountRepository, ChallengeRepository}
 import jakarta.enterprise.context.ApplicationScoped
@@ -49,10 +62,8 @@ class ChallengeService:
       challenge.color = color
       challenge.status = ChallengeStatus.Created
       challenge.timeControlType = req.timeControl.`type`
-      challenge.timeControlLimit =
-        req.timeControl.limit.map(java.lang.Integer.valueOf).orNull
-      challenge.timeControlIncrement =
-        req.timeControl.increment.map(java.lang.Integer.valueOf).orNull
+      challenge.timeControlLimit = req.timeControl.limit.map(java.lang.Integer.valueOf).orNull
+      challenge.timeControlIncrement = req.timeControl.increment.map(java.lang.Integer.valueOf).orNull
       challenge.createdAt = Instant.now()
       challenge.expiresAt = Instant.now().plus(24, ChronoUnit.HOURS)
       challengeRepository.persist(challenge)

modules/account/src/test/scala/de/nowchess/account/resource/ChallengeResourceTest.scala

@@ -156,8 +156,20 @@ class ChallengeResourceTest:
     val t1 = registerAndLogin("listUser1")
     registerAndLogin("listUser2")
     registerAndLogin("listUser3")
-    authed(t1).contentType(ContentType.JSON).body(clockBody).when().post("/api/challenge/listUser2").`then`().statusCode(201)
-    authed(t1).contentType(ContentType.JSON).body(clockBody).when().post("/api/challenge/listUser3").`then`().statusCode(201)
+    authed(t1)
+      .contentType(ContentType.JSON)
+      .body(clockBody)
+      .when()
+      .post("/api/challenge/listUser2")
+      .`then`()
+      .statusCode(201)
+    authed(t1)
+      .contentType(ContentType.JSON)
+      .body(clockBody)
+      .when()
+      .post("/api/challenge/listUser3")
+      .`then`()
+      .statusCode(201)
     authed(t1)
       .when()
       .get("/api/challenge")

modules/api/src/main/scala/de/nowchess/api/rules/PostMoveStatus.scala

@@ -0,0 +1,9 @@
+package de.nowchess.api.rules
+
+final case class PostMoveStatus(
+    isCheckmate: Boolean,
+    isStalemate: Boolean,
+    isInsufficientMaterial: Boolean,
+    isCheck: Boolean,
+    isThreefoldRepetition: Boolean,
+)

modules/api/src/main/scala/de/nowchess/api/rules/RuleSet.scala

@@ -39,3 +39,15 @@ trait RuleSet:
     * promotion. Updates castling rights, en passant square, half-move clock, turn, and move history.
     */
   def applyMove(context: GameContext)(move: Move): GameContext
+
+  /** Batch status check after a move is applied. Replaces individual isCheckmate/isStalemate/isInsufficientMaterial/
+    * isCheck/isThreefoldRepetition calls with a single round-trip. Override for remote implementations.
+    */
+  def postMoveStatus(context: GameContext): PostMoveStatus =
+    PostMoveStatus(
+      isCheckmate = isCheckmate(context),
+      isStalemate = isStalemate(context),
+      isInsufficientMaterial = isInsufficientMaterial(context),
+      isCheck = isCheck(context),
+      isThreefoldRepetition = isThreefoldRepetition(context),
+    )

modules/core/src/main/scala/de/nowchess/chess/adapter/RuleSetRestAdapter.scala

@@ -4,7 +4,7 @@ import de.nowchess.api.board.Square
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.Move
 import de.nowchess.chess.client.{RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
-import de.nowchess.api.rules.RuleSet
+import de.nowchess.api.rules.{PostMoveStatus, RuleSet}
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import org.eclipse.microprofile.rest.client.inject.RestClient
@@ -49,3 +49,6 @@ class RuleSetRestAdapter extends RuleSet:
 
   def applyMove(ctx: GameContext)(move: Move): GameContext =
     client.applyMove(RuleMoveRequest(ctx, move))
+
+  override def postMoveStatus(ctx: GameContext): PostMoveStatus =
+    client.postMoveStatus(ctx)

modules/core/src/main/scala/de/nowchess/chess/client/IoServiceClient.scala

@@ -6,6 +6,8 @@ import jakarta.ws.rs.*
 import jakarta.ws.rs.core.MediaType
 import org.eclipse.microprofile.rest.client.inject.RegisterRestClient
 
+case class CombinedExportResponse(fen: String, pgn: String)
+
 @Path("/io")
 @RegisterRestClient(configKey = "io-service")
 trait IoServiceClient:
@@ -33,3 +35,9 @@ trait IoServiceClient:
   @Consumes(Array(MediaType.APPLICATION_JSON))
   @Produces(Array("application/x-chess-pgn"))
   def exportPgn(ctx: GameContext): String
+
+  @POST
+  @Path("/export/combined")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def exportCombined(ctx: GameContext): CombinedExportResponse

modules/core/src/main/scala/de/nowchess/chess/client/RuleServiceClient.scala

@@ -2,6 +2,7 @@ package de.nowchess.chess.client
 
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.Move
+import de.nowchess.api.rules.PostMoveStatus
 import jakarta.ws.rs.*
 import jakarta.ws.rs.core.MediaType
 import org.eclipse.microprofile.rest.client.inject.RegisterRestClient
@@ -72,3 +73,9 @@ trait RuleServiceClient:
   @Consumes(Array(MediaType.APPLICATION_JSON))
   @Produces(Array(MediaType.APPLICATION_JSON))
   def applyMove(req: RuleMoveRequest): GameContext
+
+  @POST
+  @Path("/post-move-status")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def postMoveStatus(ctx: GameContext): PostMoveStatus

modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala

@@ -2,7 +2,19 @@ package de.nowchess.chess.engine
 
 import de.nowchess.api.board.{Board, Color, Piece, PieceType, Square}
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
-import de.nowchess.api.game.{BotParticipant, ClockState, CorrespondenceClockState, DrawReason, GameContext, GameResult, Human, LiveClockState, Participant, TimeControl, WinReason}
+import de.nowchess.api.game.{
+  BotParticipant,
+  ClockState,
+  CorrespondenceClockState,
+  DrawReason,
+  GameContext,
+  GameResult,
+  Human,
+  LiveClockState,
+  Participant,
+  TimeControl,
+  WinReason,
+}
 import de.nowchess.api.player.{PlayerId, PlayerInfo}
 import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.observer.*
@@ -378,28 +390,28 @@ class GameEngine(
       ),
     )
 
+    val status = ruleSet.postMoveStatus(currentContext)
     if currentContext.result.isEmpty then
-      if ruleSet.isCheckmate(currentContext) then
+      if status.isCheckmate then
         val winner = currentContext.turn.opposite
         currentContext = currentContext.withResult(Some(GameResult.Win(winner, Checkmate)))
         cancelScheduled()
         notifyObservers(CheckmateEvent(currentContext, winner))
         invoker.clear()
-      else if ruleSet.isStalemate(currentContext) then
+      else if status.isStalemate then
         currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.Stalemate)))
         cancelScheduled()
         notifyObservers(DrawEvent(currentContext, DrawReason.Stalemate))
         invoker.clear()
-      else if ruleSet.isInsufficientMaterial(currentContext) then
+      else if status.isInsufficientMaterial then
         currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.InsufficientMaterial)))
         cancelScheduled()
         notifyObservers(DrawEvent(currentContext, DrawReason.InsufficientMaterial))
         invoker.clear()
-      else if ruleSet.isCheck(currentContext) then notifyObservers(CheckDetectedEvent(currentContext))
+      else if status.isCheck then notifyObservers(CheckDetectedEvent(currentContext))
 
     if currentContext.halfMoveClock >= 100 then notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
-    if ruleSet.isThreefoldRepetition(currentContext) then
-      notifyObservers(ThreefoldRepetitionAvailableEvent(currentContext))
+    if status.isThreefoldRepetition then notifyObservers(ThreefoldRepetitionAvailableEvent(currentContext))
     else requestBotMoveIfNeeded()
 
   private def translateMoveToNotation(move: Move, boardBefore: Board): String =

modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala

@@ -3,7 +3,16 @@ package de.nowchess.chess.resource
 import com.fasterxml.jackson.databind.ObjectMapper
 import de.nowchess.api.board.{Color, Square}
 import de.nowchess.api.dto.*
-import de.nowchess.api.game.{CorrespondenceClockState, DrawReason, GameContext, GameMode, GameResult, LiveClockState, TimeControl}
+import de.nowchess.api.game.{
+  CorrespondenceClockState,
+  DrawReason,
+  GameContext,
+  GameMode,
+  GameResult,
+  LiveClockState,
+  TimeControl,
+  WinReason,
+}
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.api.player.{PlayerId, PlayerInfo}
 import java.time.Instant
@@ -56,7 +65,8 @@ class GameResource:
     entry.mode match
       case GameMode.Open => entry.engine.context.turn
       case GameMode.Authenticated =>
-        val subject = Option(jwt).flatMap(j => Option(j.getSubject))
+        val subject = Option(jwt)
+          .flatMap(j => Option(j.getSubject))
           .getOrElse(throw ForbiddenException("Authentication required"))
         if entry.white.id.value == subject then Color.White
         else if entry.black.id.value == subject then Color.Black
@@ -65,8 +75,7 @@ class GameResource:
   private def assertIsCurrentPlayer(entry: GameEntry): Unit =
     if entry.mode == GameMode.Authenticated then
       val color = colorOf(entry)
-      if color != entry.engine.context.turn then
-        throw ForbiddenException("Not your turn")
+      if color != entry.engine.context.turn then throw ForbiddenException("Not your turn")
 
   // scalafix:on DisableSyntax.throw
 
@@ -77,10 +86,9 @@ class GameResource:
     else
       val ctx = entry.engine.context
       ctx.result match
-        case Some(GameResult.Win(_, _)) =>
-          if entry.resigned then "resign"
-          else if entry.engine.ruleSet.isCheckmate(ctx) then "checkmate"
-          else "timeout"
+        case Some(GameResult.Win(_, WinReason.Checkmate))           => "checkmate"
+        case Some(GameResult.Win(_, WinReason.Resignation))         => "resign"
+        case Some(GameResult.Win(_, WinReason.TimeControl))         => "timeout"
         case Some(GameResult.Draw(DrawReason.Stalemate))            => "stalemate"
         case Some(GameResult.Draw(DrawReason.InsufficientMaterial)) => "insufficientMaterial"
         case Some(GameResult.Draw(_))                               => "draw"
@@ -129,9 +137,10 @@ class GameResource:
 
   private def toGameStateDto(entry: GameEntry): GameStateDto =
     val ctx      = entry.engine.context
+    val exported = ioClient.exportCombined(ctx)
     GameStateDto(
-      fen = ioClient.exportFen(ctx),
-      pgn = ioClient.exportPgn(ctx),
+      fen = exported.fen,
+      pgn = exported.pgn,
       turn = ctx.turn.label.toLowerCase,
       status = statusOf(entry),
       winner = ctx.result.collect { case GameResult.Win(c, _) => c.label.toLowerCase },
@@ -234,13 +243,8 @@ class GameResource:
     val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
     assertGameNotOver(entry)
     assertIsCurrentPlayer(entry)
-    val (from, to, promoOpt) = Parser
-      .parseMove(uci)
-      .getOrElse(throw BadRequestException("INVALID_UCI", s"Invalid UCI notation: $uci", Some("uci")))
-    val candidates  = entry.engine.ruleSet.legalMoves(entry.engine.context)(from).filter(_.to == to)
-    val isPromotion = candidates.exists { case Move(_, _, MoveType.Promotion(_)) => true; case _ => false }
-    if candidates.isEmpty || (isPromotion && promoOpt.isEmpty) then
-      throw BadRequestException("INVALID_MOVE", s"$uci is not a legal move", Some("uci"))
+    if Parser.parseMove(uci).isEmpty then
+      throw BadRequestException("INVALID_UCI", s"Invalid UCI notation: $uci", Some("uci"))
     applyMoveInput(entry.engine, uci).foreach(err => throw BadRequestException("INVALID_MOVE", err, Some("uci")))
     ok(toGameStateDto(entry))
 

modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineClockTest.scala

@@ -1,7 +1,15 @@
 package de.nowchess.chess.engine
 
 import de.nowchess.api.board.Color
-import de.nowchess.api.game.{ClockState, CorrespondenceClockState, DrawReason, GameResult, LiveClockState, TimeControl, WinReason}
+import de.nowchess.api.game.{
+  ClockState,
+  CorrespondenceClockState,
+  DrawReason,
+  GameResult,
+  LiveClockState,
+  TimeControl,
+  WinReason,
+}
 import de.nowchess.chess.observer.*
 import de.nowchess.rules.sets.DefaultRules
 import org.scalatest.funsuite.AnyFunSuite

modules/core/src/test/scala/de/nowchess/chess/resource/GameResourceIntegrationTest.scala

@@ -3,7 +3,8 @@ package de.nowchess.chess.resource
 import de.nowchess.api.board.Square
 import de.nowchess.api.dto.*
 import de.nowchess.api.game.GameContext
-import de.nowchess.chess.client.{IoServiceClient, RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
+import de.nowchess.api.rules.PostMoveStatus
+import de.nowchess.chess.client.{CombinedExportResponse, IoServiceClient, RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
 import de.nowchess.chess.exception.BadRequestException
 import de.nowchess.io.fen.FenExporter
 import de.nowchess.io.pgn.PgnParser
@@ -44,6 +45,10 @@ class GameResourceIntegrationTest:
     )
     when(ioClient.exportFen(any())).thenReturn(FenExporter.exportGameContext(GameContext.initial))
     when(ioClient.exportPgn(any())).thenReturn("1. e4 c5")
+    when(ioClient.exportCombined(any())).thenAnswer((inv: InvocationOnMock) =>
+      val ctx = inv.getArgument[GameContext](0)
+      CombinedExportResponse(FenExporter.exportGameContext(ctx), ""),
+    )
     when(ruleClient.legalMoves(any())).thenAnswer((inv: InvocationOnMock) =>
       val req = inv.getArgument[RuleSquareRequest](0)
       DefaultRules.legalMoves(req.context)(Square.fromAlgebraic(req.square).get),
@@ -70,6 +75,9 @@ class GameResourceIntegrationTest:
     when(ruleClient.isThreefoldRepetition(any())).thenAnswer((inv: InvocationOnMock) =>
       DefaultRules.isThreefoldRepetition(inv.getArgument[GameContext](0)),
     )
+    when(ruleClient.postMoveStatus(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.postMoveStatus(inv.getArgument[GameContext](0)),
+    )
 
   @Test
   @DisplayName("createGame returns 201")

modules/io/src/main/scala/de/nowchess/io/fen/FenParser.scala

@@ -11,16 +11,27 @@ object FenParser extends GameContextImport:
     */
   def parseFen(fen: String): Either[GameError, GameContext] =
     val parts = fen.trim.split("\\s+")
-    if parts.length != 6 then Left(GameError.ParseError(s"Invalid FEN: expected 6 space-separated fields, got ${parts.length}"))
+    if parts.length != 6 then
+      Left(GameError.ParseError(s"Invalid FEN: expected 6 space-separated fields, got ${parts.length}"))
     else
       for
         board <- parseBoard(parts(0)).toRight(GameError.ParseError("Invalid FEN: invalid board position"))
-        activeColor    <- parseColor(parts(1)).toRight(GameError.ParseError("Invalid FEN: invalid active color (expected 'w' or 'b')"))
+        activeColor <- parseColor(parts(1)).toRight(
+          GameError.ParseError("Invalid FEN: invalid active color (expected 'w' or 'b')"),
+        )
         castlingRights <- parseCastling(parts(2)).toRight(GameError.ParseError("Invalid FEN: invalid castling rights"))
         enPassant <- parseEnPassant(parts(3)).toRight(GameError.ParseError("Invalid FEN: invalid en passant square"))
-        halfMoveClock  <- parts(4).toIntOption.toRight(GameError.ParseError("Invalid FEN: invalid half-move clock (expected integer)"))
-        fullMoveNumber <- parts(5).toIntOption.toRight(GameError.ParseError("Invalid FEN: invalid full move number (expected integer)"))
-        _              <- Either.cond(halfMoveClock >= 0 && fullMoveNumber >= 1, (), GameError.ParseError("Invalid FEN: invalid move counts"))
+        halfMoveClock <- parts(4).toIntOption.toRight(
+          GameError.ParseError("Invalid FEN: invalid half-move clock (expected integer)"),
+        )
+        fullMoveNumber <- parts(5).toIntOption.toRight(
+          GameError.ParseError("Invalid FEN: invalid full move number (expected integer)"),
+        )
+        _ <- Either.cond(
+          halfMoveClock >= 0 && fullMoveNumber >= 1,
+          (),
+          GameError.ParseError("Invalid FEN: invalid move counts"),
+        )
       yield GameContext(
         board = board,
         turn = activeColor,

modules/io/src/main/scala/de/nowchess/io/service/dto/CombinedExportResponse.scala

@@ -0,0 +1,3 @@
+package de.nowchess.io.service.dto
+
+final case class CombinedExportResponse(fen: String, pgn: String)

modules/io/src/main/scala/de/nowchess/io/service/resource/IoResource.scala

@@ -3,7 +3,7 @@ package de.nowchess.io.service.resource
 import de.nowchess.api.game.GameContext
 import de.nowchess.io.fen.{FenExporter, FenParser}
 import de.nowchess.io.pgn.{PgnExporter, PgnParser}
-import de.nowchess.io.service.dto.{ImportFenRequest, ImportPgnRequest, IoErrorDto}
+import de.nowchess.io.service.dto.{CombinedExportResponse, ImportFenRequest, ImportPgnRequest, IoErrorDto}
 import io.smallrye.mutiny.Uni
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.ws.rs.*
@@ -75,3 +75,18 @@ class IoResource:
   @APIResponse(responseCode = "200", description = "PGN text")
   def exportPgn(ctx: GameContext): Uni[Response] =
     Uni.createFrom().item(Response.ok(PgnExporter.exportGameContext(ctx)).build())
+
+  @POST
+  @Path("/export/combined")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  @Operation(summary = "Export FEN and PGN", description = "Serialize a GameContext to both FEN and PGN in one call")
+  @APIResponse(responseCode = "200", description = "FEN and PGN")
+  def exportCombined(ctx: GameContext): Uni[Response] =
+    Uni
+      .createFrom()
+      .item(
+        Response
+          .ok(CombinedExportResponse(FenExporter.exportGameContext(ctx), PgnExporter.exportGameContext(ctx)))
+          .build(),
+      )

modules/rule/src/main/scala/de/nowchess/rules/resource/RuleSetResource.scala

@@ -4,6 +4,7 @@ import de.nowchess.api.board.Square
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.Move
 import de.nowchess.rules.dto.*
+import de.nowchess.api.rules.PostMoveStatus
 import de.nowchess.rules.sets.DefaultRules
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.ws.rs.*
@@ -88,3 +89,10 @@ class RuleSetResource:
   @Produces(Array(MediaType.APPLICATION_JSON))
   def applyMove(req: ContextMoveRequest): GameContext =
     rules.applyMove(req.context)(req.move)
+
+  @POST
+  @Path("/post-move-status")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def postMoveStatus(ctx: GameContext): PostMoveStatus =
+    rules.postMoveStatus(ctx)

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

@@ -3,7 +3,7 @@ package de.nowchess.rules.sets
 import de.nowchess.api.board.*
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
-import de.nowchess.api.rules.RuleSet
+import de.nowchess.api.rules.{PostMoveStatus, RuleSet}
 
 /** Standard chess rules — optimized hot path.
   *
@@ -12,6 +12,8 @@ import de.nowchess.api.rules.RuleSet
   * avoid heap allocation in tight loops. Check detection uses make/unmake on the mutable array instead of copying the
   * immutable Board map.
   */
+// scalafix:off DisableSyntax.var
+// scalafix:off DisableSyntax.return
 object DefaultRules extends RuleSet:
 
   // ─── Piece constants ──────────────────────────────────────────────────────
@@ -225,12 +227,19 @@ object DefaultRules extends RuleSet:
     var n = 0; var sq = 0
     while sq < 64 do
       val p = arr(sq)
-      if !isEmpty(p) && isWhitePiece(p) == isWhite then
-        n = generatePiece(arr, sq, pieceType(p), isWhite, ctx, buf, n)
+      if !isEmpty(p) && isWhitePiece(p) == isWhite then n = generatePiece(arr, sq, pieceType(p), isWhite, ctx, buf, n)
       sq += 1
     n
 
-  private def generatePiece(arr: Array[Int], sq: Int, pt: Int, isWhite: Boolean, ctx: GameContext, buf: Array[Int], n: Int): Int =
+  private def generatePiece(
+      arr: Array[Int],
+      sq: Int,
+      pt: Int,
+      isWhite: Boolean,
+      ctx: GameContext,
+      buf: Array[Int],
+      n: Int,
+  ): Int =
     if pt == PAWN then generatePawnMoves(arr, sq, isWhite, ctx, buf, n)
     else if pt == KNIGHT then generateJumps(arr, sq, isWhite, KNIGHT_TARGETS(sq), buf, n)
     else if pt == BISHOP then generateRays(arr, sq, isWhite, buf, n, rookRays = false)
@@ -240,7 +249,14 @@ object DefaultRules extends RuleSet:
       generateRays(arr, sq, isWhite, buf, n2, rookRays = false)
     else generateKingMoves(arr, sq, isWhite, ctx, buf, n)
 
-  private def generateJumps(arr: Array[Int], from: Int, isWhite: Boolean, targets: Array[Int], buf: Array[Int], start: Int): Int =
+  private def generateJumps(
+      arr: Array[Int],
+      from: Int,
+      isWhite: Boolean,
+      targets: Array[Int],
+      buf: Array[Int],
+      start: Int,
+  ): Int =
     var n = start; var i = 0
     while i < targets.length do
       val to = targets(i); val tgt = arr(to)
@@ -251,7 +267,14 @@ object DefaultRules extends RuleSet:
       i += 1
     n
 
-  private def generateRays(arr: Array[Int], from: Int, isWhite: Boolean, buf: Array[Int], start: Int, rookRays: Boolean): Int =
+  private def generateRays(
+      arr: Array[Int],
+      from: Int,
+      isWhite: Boolean,
+      buf: Array[Int],
+      start: Int,
+      rookRays: Boolean,
+  ): Int =
     var n    = start
     val rays = RAY_TABLES(from)
     val d0   = if rookRays then 0 else 4
@@ -271,11 +294,25 @@ object DefaultRules extends RuleSet:
       d += 1
     n
 
-  private def generateKingMoves(arr: Array[Int], from: Int, isWhite: Boolean, ctx: GameContext, buf: Array[Int], start: Int): Int =
+  private def generateKingMoves(
+      arr: Array[Int],
+      from: Int,
+      isWhite: Boolean,
+      ctx: GameContext,
+      buf: Array[Int],
+      start: Int,
+  ): Int =
     val n = generateJumps(arr, from, isWhite, KING_TARGETS(from), buf, start)
     generateCastlingMoves(arr, from, isWhite, ctx, buf, n)
 
-  private def generateCastlingMoves(arr: Array[Int], from: Int, isWhite: Boolean, ctx: GameContext, buf: Array[Int], start: Int): Int =
+  private def generateCastlingMoves(
+      arr: Array[Int],
+      from: Int,
+      isWhite: Boolean,
+      ctx: GameContext,
+      buf: Array[Int],
+      start: Int,
+  ): Int =
     var n  = start
     val cr = ctx.castlingRights
     if isWhite && from == E1 then
@@ -283,30 +320,41 @@ object DefaultRules extends RuleSet:
         arr(E1) == KING && arr(H1) == ROOK &&
         !isAttackedByColor(arr, E1, false) &&
         !isAttackedByColor(arr, F1, false) &&
-          !isAttackedByColor(arr, G1, false) then
+        !isAttackedByColor(arr, G1, false)
+      then
         buf(n) = encMove(E1, G1, KIND_CASTLEK); n += 1
       if cr.whiteQueenSide && isEmpty(arr(D1)) && isEmpty(arr(C1)) && isEmpty(arr(B1)) &&
         arr(E1) == KING && arr(A1) == ROOK &&
         !isAttackedByColor(arr, E1, false) &&
         !isAttackedByColor(arr, D1, false) &&
-          !isAttackedByColor(arr, C1, false) then
+        !isAttackedByColor(arr, C1, false)
+      then
         buf(n) = encMove(E1, C1, KIND_CASTLEQ); n += 1
     else if !isWhite && from == E8 then
       if cr.blackKingSide && isEmpty(arr(F8)) && isEmpty(arr(G8)) &&
         arr(E8) == -KING && arr(H8) == -ROOK &&
         !isAttackedByColor(arr, E8, true) &&
         !isAttackedByColor(arr, F8, true) &&
-          !isAttackedByColor(arr, G8, true) then
+        !isAttackedByColor(arr, G8, true)
+      then
         buf(n) = encMove(E8, G8, KIND_CASTLEK); n += 1
       if cr.blackQueenSide && isEmpty(arr(D8)) && isEmpty(arr(C8)) && isEmpty(arr(B8)) &&
         arr(E8) == -KING && arr(A8) == -ROOK &&
         !isAttackedByColor(arr, E8, true) &&
         !isAttackedByColor(arr, D8, true) &&
-          !isAttackedByColor(arr, C8, true) then
+        !isAttackedByColor(arr, C8, true)
+      then
         buf(n) = encMove(E8, C8, KIND_CASTLEQ); n += 1
     n
 
-  private def generatePawnMoves(arr: Array[Int], from: Int, isWhite: Boolean, ctx: GameContext, buf: Array[Int], start: Int): Int =
+  private def generatePawnMoves(
+      arr: Array[Int],
+      from: Int,
+      isWhite: Boolean,
+      ctx: GameContext,
+      buf: Array[Int],
+      start: Int,
+  ): Int =
     var n         = start
     val f         = fileOf(from); val r = rankOf(from)
     val fwd       = if isWhite then 1 else -1
@@ -531,7 +579,12 @@ object DefaultRules extends RuleSet:
 
   // ─── Threefold repetition ─────────────────────────────────────────────────
 
-  private case class Position(board: Board, turn: Color, castlingRights: CastlingRights, enPassantSquare: Option[Square])
+  private case class Position(
+      board: Board,
+      turn: Color,
+      castlingRights: CastlingRights,
+      enPassantSquare: Option[Square],
+  )
 
   private def countPositionOccurrences(context: GameContext, target: Position): Int =
     try
@@ -557,5 +610,13 @@ object DefaultRules extends RuleSet:
           (nextCtx, nextCount)
         }
         ._2
-    catch
-      case _: Exception => 1
+    catch case _: Exception => 1
+
+  override def postMoveStatus(context: GameContext): PostMoveStatus =
+    PostMoveStatus(
+      isCheckmate = isCheckmate(context),
+      isStalemate = isStalemate(context),
+      isInsufficientMaterial = isInsufficientMaterial(context),
+      isCheck = isCheck(context),
+      isThreefoldRepetition = isThreefoldRepetition(context),
+    )