feat(backcore): Quarkus compatible with GUI/TUI

Added quarkus backcore run functionality so that it launches the TUI, GUI, Quarkus via modules: backcore:run

modules/backcore/build.gradle.kts

@@ -34,6 +34,7 @@ dependencies {
     implementation(project(":modules:core"))
     implementation(project(":modules:io"))
     implementation(project(":modules:rule"))
+    implementation(project(":modules:ui"))
 
     implementation(enforcedPlatform("${quarkusPlatformGroupId}:${quarkusPlatformArtifactId}:${quarkusPlatformVersion}"))
     implementation("io.quarkus:quarkus-rest")
@@ -90,7 +91,11 @@ tasks.jacocoTestReport {
     dependsOn(tasks.test)
     executionData.setFrom(layout.buildDirectory.file("jacoco-quarkus.exec"))
     sourceDirectories.setFrom(files("src/main/scala"))
-    classDirectories.setFrom(files(layout.buildDirectory.dir("classes/scala/main")))
+    classDirectories.setFrom(
+        files(layout.buildDirectory.dir("classes/scala/main")).asFileTree.matching {
+            exclude("**/AppMain*.class", "**/AppMain\$*.class")
+        }
+    )
     reports {
         xml.required.set(true)
         xml.outputLocation.set(

modules/backcore/src/main/scala/de/nowchess/backcore/AppMain.scala

@@ -0,0 +1,17 @@
+package de.nowchess.backcore
+
+import de.nowchess.backcore.game.{GameEngineHolder, GameId}
+import de.nowchess.ui.gui.ChessGUILauncher
+import de.nowchess.ui.terminal.TerminalUI
+import io.quarkus.runtime.annotations.QuarkusMain
+import io.quarkus.runtime.{Quarkus, QuarkusApplication}
+
+@QuarkusMain
+class AppMain extends QuarkusApplication:
+  override def run(args: String*): Int =
+    val engine = GameEngineHolder.engine
+    println(s"REST API -> http://localhost:8080/api/board/game/${GameEngineHolder.gameId}")
+    ChessGUILauncher.launch(engine)
+    new TerminalUI(engine).start()
+    Quarkus.asyncExit()
+    0

modules/backcore/src/main/scala/de/nowchess/backcore/game/GameEngineHolder.scala

@@ -0,0 +1,28 @@
+package de.nowchess.backcore.game
+
+import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.chess.engine.GameEngine
+
+import java.util.concurrent.atomic.AtomicReference
+
+/** Singleton holder that bridges an externally-created GameEngine into the CDI context.
+  *
+  * All fields are `val` wrapping an AtomicReference. Set engine / white / black before starting Quarkus. In
+  * standalone-server or test mode the defaults are used; GameService is created lazily (on first request), so the
+  * values are already set by the time CDI constructs it.
+  */
+object GameEngineHolder:
+  private val engineRef = new AtomicReference[GameEngine](new GameEngine())
+  private val whiteRef  = new AtomicReference[PlayerInfo](PlayerInfo(PlayerId("white"), "White"))
+  private val blackRef  = new AtomicReference[PlayerInfo](PlayerInfo(PlayerId("black"), "Black"))
+
+  val gameId: String = GameId.generate()
+
+  def engine: GameEngine            = engineRef.get()
+  def engine_=(e: GameEngine): Unit = engineRef.set(e)
+
+  def white: PlayerInfo            = whiteRef.get()
+  def white_=(p: PlayerInfo): Unit = whiteRef.set(p)
+
+  def black: PlayerInfo            = blackRef.get()
+  def black_=(p: PlayerInfo): Unit = blackRef.set(p)

modules/backcore/src/main/scala/de/nowchess/backcore/game/GameMapper.scala

@@ -3,6 +3,7 @@ package de.nowchess.backcore.game
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.module.scala.DefaultScalaModule
 import de.nowchess.api.board.Color
+import de.nowchess.api.game.{DrawReason, GameResult as ApiGameResult}
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.backcore.dto.*
 import de.nowchess.io.fen.FenExporter
@@ -12,54 +13,53 @@ import de.nowchess.rules.sets.DefaultRules
 object GameMapper:
   private val mapper = new ObjectMapper().registerModule(DefaultScalaModule)
 
-  def toGameFullJson(session: GameSession): String =
-    mapper.writeValueAsString(toGameFull(session))
+  def toGameFullJson(snapshot: GameSnapshot): String =
+    mapper.writeValueAsString(toGameFull(snapshot))
 
-  def toGameFull(session: GameSession): GameFullResponse =
+  def toGameFull(snapshot: GameSnapshot): GameFullResponse =
     GameFullResponse(
-      gameId = session.gameId,
-      white = toPlayerInfo(session.white),
-      black = toPlayerInfo(session.black),
-      state = toGameState(session),
+      gameId = snapshot.gameId,
+      white = toPlayerInfo(snapshot.white),
+      black = toPlayerInfo(snapshot.black),
+      state = toGameState(snapshot),
     )
 
-  def toGameState(session: GameSession): GameStateResponse =
-    val (status, winner) = computeStatus(session)
+  def toGameState(snapshot: GameSnapshot): GameStateResponse =
+    val (status, winner) = computeStatus(snapshot)
     GameStateResponse(
-      fen = FenExporter.exportGameContext(session.context),
-      pgn = buildPgn(session.context.moves),
-      turn = if session.context.turn == Color.White then "white" else "black",
+      fen = FenExporter.exportGameContext(snapshot.context),
+      pgn = buildPgn(snapshot.context.moves),
+      turn = if snapshot.context.turn == Color.White then "white" else "black",
       status = status,
       winner = winner,
-      moves = session.context.moves.map(moveToUci),
-      undoAvailable = session.invoker.canUndo,
-      redoAvailable = session.invoker.canRedo,
+      moves = snapshot.context.moves.map(moveToUci),
+      undoAvailable = snapshot.canUndo,
+      redoAvailable = snapshot.canRedo,
     )
 
   private def toPlayerInfo(p: de.nowchess.api.player.PlayerInfo): PlayerInfoDto =
     PlayerInfoDto(id = p.id.value, displayName = p.displayName)
 
-  private def computeStatus(session: GameSession): (String, Option[String]) =
-    session.result match
-      case Some(GameResult.Checkmate(winner)) =>
-        val w = if winner == Color.White then "white" else "black"
-        ("checkmate", Some(w))
-      case Some(GameResult.Stalemate) =>
-        ("stalemate", None)
+  private def colorStr(c: Color): String = if c == Color.White then "white" else "black"
+
+  private def computeStatus(snapshot: GameSnapshot): (String, Option[String]) =
+    snapshot.externalResult match
       case Some(GameResult.Resign(winner)) =>
-        val w = if winner == Color.White then "white" else "black"
-        ("resign", Some(w))
+        ("resign", Some(colorStr(winner)))
       case Some(GameResult.AgreedDraw) | Some(GameResult.FiftyMoveDraw) =>
         ("draw", None)
-      case Some(GameResult.InsufficientMaterial) =>
-        ("insufficientMaterial", None)
-      case None =>
-        computeLiveStatus(session)
+      case _ =>
+        snapshot.context.result match
+          case Some(ApiGameResult.Win(winner))                           => ("checkmate", Some(colorStr(winner)))
+          case Some(ApiGameResult.Draw(DrawReason.Stalemate))            => ("stalemate", None)
+          case Some(ApiGameResult.Draw(DrawReason.InsufficientMaterial)) => ("insufficientMaterial", None)
+          case Some(ApiGameResult.Draw(_))                               => ("draw", None)
+          case None                                                      => computeLiveStatus(snapshot)
 
-  private def computeLiveStatus(session: GameSession): (String, Option[String]) =
-    val ctx = session.context
+  private def computeLiveStatus(snapshot: GameSnapshot): (String, Option[String]) =
+    val ctx = snapshot.context
     if DefaultRules.isCheck(ctx) then ("check", None)
-    else if session.drawOfferedBy.isDefined then ("drawOffered", None)
+    else if snapshot.drawOfferedBy.isDefined then ("drawOffered", None)
     else if DefaultRules.isFiftyMoveRule(ctx) then ("fiftyMoveAvailable", None)
     else ("started", None)
 
@@ -76,5 +76,4 @@ object GameMapper:
       case _ => base
 
   private def buildPgn(moves: List[Move]): String =
-    // Use PgnExporter with no headers to get move-text only (SAN notation)
     PgnExporter.exportGame(Map.empty, moves)

modules/backcore/src/main/scala/de/nowchess/backcore/game/GameService.scala

@@ -0,0 +1,175 @@
+package de.nowchess.backcore.game
+
+import de.nowchess.api.board.{Color, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.backcore.dto.{CreateGameRequest, ImportFenRequest, PlayerInfoDto}
+import de.nowchess.io.fen.{FenExporter, FenParser}
+import de.nowchess.io.pgn.{PgnExporter, PgnParser}
+import de.nowchess.rules.sets.DefaultRules
+import jakarta.enterprise.context.ApplicationScoped
+
+private case class ServiceState(
+    drawOfferedBy: Option[Color] = None,
+    externalResult: Option[GameResult] = None,
+)
+
+@ApplicationScoped
+class GameService:
+  private val engine = GameEngineHolder.engine
+  @SuppressWarnings(Array("DisableSyntax.var"))
+  private var state: ServiceState = ServiceState()
+
+  def isKnownId(id: String): Boolean = id == GameEngineHolder.gameId
+
+  def getSnapshot: GameSnapshot = synchronized:
+    GameSnapshot(
+      gameId = GameEngineHolder.gameId,
+      white = GameEngineHolder.white,
+      black = GameEngineHolder.black,
+      context = engine.context,
+      drawOfferedBy = state.drawOfferedBy,
+      externalResult = state.externalResult,
+      canUndo = engine.canUndo,
+      canRedo = engine.canRedo,
+    )
+
+  def reset(req: CreateGameRequest): GameSnapshot = synchronized:
+    engine.reset()
+    state = ServiceState()
+    GameEngineHolder.white = toPlayerInfo(req.white, "white", "White")
+    GameEngineHolder.black = toPlayerInfo(req.black, "black", "Black")
+    getSnapshot
+
+  def applyMove(uci: String): Either[String, GameSnapshot] = synchronized:
+    if hasEnded then Left("Game is already over")
+    else
+      parseUci(uci) match
+        case None => Left(s"Invalid UCI notation: $uci")
+        case Some((from, to, promotion)) =>
+          val candidates = engine.ruleSet.legalMoves(engine.context)(from)
+          findMatchingMove(candidates, to, promotion) match
+            case None => Left(s"$uci is not a legal move")
+            case Some(move) =>
+              engine.processUserInput(s"$from$to")
+              promotion.foreach(engine.completePromotion)
+              Right(getSnapshot)
+
+  def legalMoves(square: Option[Square]): List[Move] = synchronized:
+    val ctx = engine.context
+    square match
+      case Some(sq) => engine.ruleSet.legalMoves(ctx)(sq)
+      case None     => engine.ruleSet.allLegalMoves(ctx)
+
+  def undo(): Either[String, GameSnapshot] = synchronized:
+    if !engine.canUndo then Left("No moves to undo")
+    else
+      engine.undo()
+      state = state.copy(externalResult = None, drawOfferedBy = None)
+      Right(getSnapshot)
+
+  def redo(): Either[String, GameSnapshot] = synchronized:
+    if !engine.canRedo then Left("No moves to redo")
+    else
+      engine.redo()
+      Right(getSnapshot)
+
+  def resign(): Either[String, GameSnapshot] = synchronized:
+    if hasEnded then Left("Game is already over")
+    else
+      val winner = engine.context.turn.opposite
+      state = state.copy(externalResult = Some(GameResult.Resign(winner)))
+      Right(getSnapshot)
+
+  def drawAction(action: String): Either[String, GameSnapshot] = synchronized:
+    if hasEnded then Left("Game is already over")
+    else
+      action match
+        case "offer" =>
+          state = state.copy(drawOfferedBy = Some(engine.context.turn))
+          Right(getSnapshot)
+        case "accept" =>
+          state.drawOfferedBy match
+            case None => Left("No draw offer to accept")
+            case Some(offerer) if offerer == engine.context.turn =>
+              Left("Cannot accept your own draw offer")
+            case Some(_) =>
+              state = state.copy(externalResult = Some(GameResult.AgreedDraw), drawOfferedBy = None)
+              Right(getSnapshot)
+        case "decline" =>
+          state.drawOfferedBy match
+            case None => Left("No draw offer to decline")
+            case Some(_) =>
+              state = state.copy(drawOfferedBy = None)
+              Right(getSnapshot)
+        case "claim" =>
+          if DefaultRules.isFiftyMoveRule(engine.context) then
+            state = state.copy(externalResult = Some(GameResult.FiftyMoveDraw))
+            Right(getSnapshot)
+          else Left("Fifty-move rule has not been triggered")
+        case other => Left(s"Unknown draw action: $other")
+
+  def importFen(req: ImportFenRequest): Either[String, GameSnapshot] = synchronized:
+    FenParser.parseFen(req.fen) match
+      case Left(err) => Left(err)
+      case Right(ctx) =>
+        engine.loadPosition(ctx)
+        state = ServiceState()
+        GameEngineHolder.white = toPlayerInfo(req.white, "white", "White")
+        GameEngineHolder.black = toPlayerInfo(req.black, "black", "Black")
+        Right(getSnapshot)
+
+  def importPgn(pgn: String): Either[String, GameSnapshot] = synchronized:
+    engine.loadGame(PgnParser, pgn) match
+      case Left(err) => Left(err)
+      case Right(_) =>
+        state = ServiceState()
+        Right(getSnapshot)
+
+  def exportFen(): String = FenExporter.exportGameContext(engine.context)
+
+  def exportPgn(): String = PgnExporter.exportGameContext(engine.context)
+
+  private def hasEnded: Boolean =
+    state.externalResult.isDefined || engine.context.result.isDefined
+
+  private def toPlayerInfo(dto: Option[PlayerInfoDto], defaultId: String, defaultName: String): PlayerInfo =
+    dto.fold(PlayerInfo(PlayerId(defaultId), defaultName))(d => PlayerInfo(PlayerId(d.id), d.displayName))
+
+  private def parseUci(uci: String): Option[(Square, Square, Option[PromotionPiece])] =
+    if uci.length < 4 || uci.length > 5 then None
+    else
+      for
+        from <- Square.fromAlgebraic(uci.substring(0, 2))
+        to   <- Square.fromAlgebraic(uci.substring(2, 4))
+      yield
+        val promotion = if uci.length == 5 then parsePromotionChar(uci.charAt(4)) else None
+        (from, to, promotion)
+
+  private def parsePromotionChar(c: Char): Option[PromotionPiece] =
+    c match
+      case 'q' => Some(PromotionPiece.Queen)
+      case 'r' => Some(PromotionPiece.Rook)
+      case 'b' => Some(PromotionPiece.Bishop)
+      case 'n' => Some(PromotionPiece.Knight)
+      case _   => None
+
+  private def findMatchingMove(
+      candidates: List[Move],
+      to: Square,
+      promotion: Option[PromotionPiece],
+  ): Option[Move] =
+    candidates.filter(_.to == to) match
+      case Nil => None
+      case moves =>
+        promotion match
+          case Some(pp) => moves.find(_.moveType == MoveType.Promotion(pp))
+          case None =>
+            moves
+              .find(m =>
+                m.moveType match
+                  case _: MoveType.Promotion => false
+                  case _                     => true,
+              )
+              .orElse(moves.headOption)

modules/backcore/src/main/scala/de/nowchess/backcore/game/GameSnapshot.scala

@@ -3,14 +3,14 @@ package de.nowchess.backcore.game
 import de.nowchess.api.board.Color
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.player.PlayerInfo
-import de.nowchess.chess.command.CommandInvoker
 
-case class GameSession(
+case class GameSnapshot(
     gameId: String,
     white: PlayerInfo,
     black: PlayerInfo,
     context: GameContext,
-    invoker: CommandInvoker,
     drawOfferedBy: Option[Color] = None,
-    result: Option[GameResult] = None,
+    externalResult: Option[GameResult] = None,
+    canUndo: Boolean = false,
+    canRedo: Boolean = false,
 )

modules/backcore/src/main/scala/de/nowchess/backcore/game/GameStore.scala

@@ -1,260 +0,0 @@
-package de.nowchess.backcore.game
-
-import de.nowchess.api.board.{Color, Square}
-import de.nowchess.api.game.GameContext
-import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
-import de.nowchess.api.player.{PlayerId, PlayerInfo}
-import de.nowchess.backcore.dto.{CreateGameRequest, ImportFenRequest, PlayerInfoDto}
-import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
-import de.nowchess.io.fen.FenParser
-import de.nowchess.io.pgn.PgnParser
-import de.nowchess.rules.sets.DefaultRules
-import jakarta.enterprise.context.ApplicationScoped
-
-import scala.collection.mutable
-
-@ApplicationScoped
-class GameStore:
-  private val games: mutable.Map[String, GameSession] = mutable.Map.empty
-
-  // ─── Create / Get ────────────────────────────────────────────────
-
-  def create(req: CreateGameRequest): GameSession = synchronized:
-    val id      = generateId()
-    val session = newSession(id, req.white, req.black, GameContext.initial)
-    games(id) = session
-    session
-
-  def get(id: String): Option[GameSession] = synchronized:
-    games.get(id)
-
-  // ─── Move-making ─────────────────────────────────────────────────
-
-  def applyMove(id: String, uci: String): Either[String, GameSession] = synchronized:
-    withSession(id): session =>
-      if session.result.isDefined then Left("Game is already over")
-      else
-        parseUci(uci) match
-          case None => Left(s"Invalid UCI notation: $uci")
-          case Some((from, to, promotion)) =>
-            val legalCandidates = DefaultRules.legalMoves(session.context)(from)
-            findMatchingMove(legalCandidates, to, promotion) match
-              case None => Left(s"$uci is not a legal move")
-              case Some(move) =>
-                val nextCtx = DefaultRules.applyMove(session.context)(move)
-                val prevCtx = session.context
-                val cmd = MoveCommand(
-                  from = move.from,
-                  to = move.to,
-                  moveResult = Some(MoveResult.Successful(nextCtx, prevCtx.board.pieceAt(move.to))),
-                  previousContext = Some(prevCtx),
-                )
-                session.invoker.execute(cmd)
-                val result  = detectGameOver(nextCtx)
-                val updated = session.copy(context = nextCtx, result = result)
-                games(id) = updated
-                Right(updated)
-
-  def legalMoves(id: String, square: Option[Square]): Either[String, List[Move]] = synchronized:
-    withSession(id): session =>
-      val moves = square match
-        case Some(sq) => DefaultRules.legalMoves(session.context)(sq)
-        case None     => DefaultRules.allLegalMoves(session.context)
-      Right(moves)
-
-  // ─── Undo / Redo ─────────────────────────────────────────────────
-
-  def undo(id: String): Either[String, GameSession] = synchronized:
-    withSession(id): session =>
-      if !session.invoker.canUndo then Left("No moves to undo")
-      else
-        val idx = session.invoker.getCurrentIndex
-        session.invoker.history(idx) match
-          case cmd: MoveCommand =>
-            cmd.previousContext match
-              case None => Left("Cannot undo: no previous context stored")
-              case Some(prevCtx) =>
-                session.invoker.undo()
-                val updated = session.copy(context = prevCtx, result = None, drawOfferedBy = None)
-                games(id) = updated
-                Right(updated)
-          case _ => Left("Cannot undo this command type")
-
-  def redo(id: String): Either[String, GameSession] = synchronized:
-    withSession(id): session =>
-      if !session.invoker.canRedo then Left("No moves to redo")
-      else
-        val idx = session.invoker.getCurrentIndex + 1
-        session.invoker.history(idx) match
-          case cmd: MoveCommand =>
-            cmd.moveResult match
-              case Some(MoveResult.Successful(nextCtx, _)) =>
-                session.invoker.redo()
-                val result  = detectGameOver(nextCtx)
-                val updated = session.copy(context = nextCtx, result = result)
-                games(id) = updated
-                Right(updated)
-              case _ => Left("Cannot redo: move result not available")
-          case _ => Left("Cannot redo this command type")
-
-  // ─── Resign ──────────────────────────────────────────────────────
-
-  def resign(id: String): Either[String, GameSession] = synchronized:
-    withSession(id): session =>
-      if session.result.isDefined then Left("Game is already over")
-      else
-        val winner  = session.context.turn.opposite
-        val updated = session.copy(result = Some(GameResult.Resign(winner)))
-        games(id) = updated
-        Right(updated)
-
-  // ─── Draw actions ────────────────────────────────────────────────
-
-  def drawAction(id: String, action: String): Either[String, GameSession] = synchronized:
-    withSession(id): session =>
-      if session.result.isDefined then Left("Game is already over")
-      else
-        action match
-          case "offer" =>
-            val updated = session.copy(drawOfferedBy = Some(session.context.turn))
-            games(id) = updated
-            Right(updated)
-          case "accept" =>
-            session.drawOfferedBy match
-              case None => Left("No draw offer to accept")
-              case Some(offerer) if offerer == session.context.turn =>
-                Left("Cannot accept your own draw offer")
-              case Some(_) =>
-                val updated = session.copy(result = Some(GameResult.AgreedDraw), drawOfferedBy = None)
-                games(id) = updated
-                Right(updated)
-          case "decline" =>
-            session.drawOfferedBy match
-              case None => Left("No draw offer to decline")
-              case Some(_) =>
-                val updated = session.copy(drawOfferedBy = None)
-                games(id) = updated
-                Right(updated)
-          case "claim" =>
-            if DefaultRules.isFiftyMoveRule(session.context) then
-              val updated = session.copy(result = Some(GameResult.FiftyMoveDraw))
-              games(id) = updated
-              Right(updated)
-            else Left("Fifty-move rule has not been triggered")
-          case other => Left(s"Unknown draw action: $other")
-
-  // ─── Import ──────────────────────────────────────────────────────
-
-  def importFen(req: ImportFenRequest): Either[String, GameSession] = synchronized:
-    FenParser.parseFen(req.fen) match
-      case Left(err) => Left(err)
-      case Right(ctx) =>
-        val id      = generateId()
-        val session = newSession(id, req.white, req.black, ctx)
-        games(id) = session
-        Right(session)
-
-  def importPgn(pgn: String, white: Option[PlayerInfoDto], black: Option[PlayerInfoDto]): Either[String, GameSession] =
-    synchronized:
-      PgnParser.validatePgn(pgn) match
-        case Left(err) => Left(err)
-        case Right(game) =>
-          val id      = generateId()
-          val session = newSession(id, white, black, GameContext.initial)
-          replayIntoSession(session, game.moves, GameContext.initial) match
-            case Left(err) => Left(err)
-            case Right(s) =>
-              games(id) = s
-              Right(s)
-
-  // ─── Private helpers ─────────────────────────────────────────────
-
-  private def withSession[A](id: String)(f: GameSession => Either[String, A]): Either[String, A] =
-    games.get(id) match
-      case None          => Left(s"Game $id not found")
-      case Some(session) => f(session)
-
-  private def generateId(): String =
-    var id = GameId.generate()
-    while games.contains(id) do id = GameId.generate()
-    id
-
-  private def newSession(
-      id: String,
-      white: Option[PlayerInfoDto],
-      black: Option[PlayerInfoDto],
-      ctx: GameContext,
-  ): GameSession =
-    GameSession(
-      gameId = id,
-      white = toPlayerInfo(white, "white", "White"),
-      black = toPlayerInfo(black, "black", "Black"),
-      context = ctx,
-      invoker = new CommandInvoker(),
-    )
-
-  private def toPlayerInfo(dto: Option[PlayerInfoDto], defaultId: String, defaultName: String): PlayerInfo =
-    dto.fold(PlayerInfo(PlayerId(defaultId), defaultName))(d => PlayerInfo(PlayerId(d.id), d.displayName))
-
-  private def parseUci(uci: String): Option[(Square, Square, Option[PromotionPiece])] =
-    if uci.length < 4 || uci.length > 5 then None
-    else
-      for
-        from <- Square.fromAlgebraic(uci.substring(0, 2))
-        to   <- Square.fromAlgebraic(uci.substring(2, 4))
-      yield
-        val promotion = if uci.length == 5 then parsePromotionChar(uci.charAt(4)) else None
-        (from, to, promotion)
-
-  private def parsePromotionChar(c: Char): Option[PromotionPiece] =
-    c match
-      case 'q' => Some(PromotionPiece.Queen)
-      case 'r' => Some(PromotionPiece.Rook)
-      case 'b' => Some(PromotionPiece.Bishop)
-      case 'n' => Some(PromotionPiece.Knight)
-      case _   => None
-
-  private def findMatchingMove(
-      candidates: List[Move],
-      to: Square,
-      promotion: Option[PromotionPiece],
-  ): Option[Move] =
-    candidates.filter(_.to == to) match
-      case Nil => None
-      case moves =>
-        promotion match
-          case Some(pp) => moves.find(_.moveType == MoveType.Promotion(pp))
-          case None =>
-            moves
-              .find(m => !m.moveType.isInstanceOf[MoveType.Promotion])
-              .orElse(moves.headOption)
-
-  private def detectGameOver(ctx: GameContext): Option[GameResult] =
-    if DefaultRules.isCheckmate(ctx) then Some(GameResult.Checkmate(ctx.turn.opposite))
-    else if DefaultRules.isStalemate(ctx) then Some(GameResult.Stalemate)
-    else if DefaultRules.isInsufficientMaterial(ctx) then Some(GameResult.InsufficientMaterial)
-    else None
-
-  private def replayIntoSession(
-      session: GameSession,
-      moves: List[Move],
-      startCtx: GameContext,
-  ): Either[String, GameSession] =
-    moves.foldLeft[Either[String, GameSession]](Right(session)):
-      case (Left(err), _) => Left(err)
-      case (Right(s), move) =>
-        val legal = DefaultRules.legalMoves(s.context)(move.from)
-        legal
-          .find(m => m.from == move.from && m.to == move.to && m.moveType == move.moveType)
-          .orElse(legal.find(m => m.from == move.from && m.to == move.to)) match
-          case None => Left(s"Illegal move in PGN: $move")
-          case Some(legalMove) =>
-            val nextCtx = DefaultRules.applyMove(s.context)(legalMove)
-            val cmd = MoveCommand(
-              from = legalMove.from,
-              to = legalMove.to,
-              moveResult = Some(MoveResult.Successful(nextCtx, s.context.board.pieceAt(legalMove.to))),
-              previousContext = Some(s.context),
-            )
-            s.invoker.execute(cmd)
-            Right(s.copy(context = nextCtx))

modules/backcore/src/main/scala/de/nowchess/backcore/resource/GameResource.scala

@@ -1,7 +1,7 @@
 package de.nowchess.backcore.resource
 
 import de.nowchess.backcore.dto.*
-import de.nowchess.backcore.game.{GameMapper, GameStore}
+import de.nowchess.backcore.game.{GameMapper, GameService}
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import jakarta.ws.rs.*
@@ -10,50 +10,47 @@ import jakarta.ws.rs.core.{MediaType, Response}
 @Path("/api/board/game")
 @Produces(Array(MediaType.APPLICATION_JSON))
 @ApplicationScoped
-class GameResource @Inject() (store: GameStore):
+class GameResource @Inject() (service: GameService):
 
   @POST
   @Consumes(Array(MediaType.APPLICATION_JSON))
   def createGame(req: CreateGameRequest): Response =
-    val session = store.create(Option(req).getOrElse(CreateGameRequest()))
-    Response.status(201).entity(GameMapper.toGameFull(session)).build()
+    val snapshot = service.reset(Option(req).getOrElse(CreateGameRequest()))
+    Response.status(201).entity(GameMapper.toGameFull(snapshot)).build()
 
   @GET
   @Path("/{gameId}")
   def getGame(@PathParam("gameId") gameId: String): Response =
-    store.get(gameId) match
-      case Some(session) => Response.ok(GameMapper.toGameFull(session)).build()
-      case None =>
-        Response
-          .status(404)
-          .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
-          .build()
+    if !service.isKnownId(gameId) then
+      Response
+        .status(404)
+        .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
+        .build()
+    else Response.ok(GameMapper.toGameFull(service.getSnapshot)).build()
 
   @GET
   @Path("/{gameId}/stream")
   @Produces(Array("application/x-ndjson"))
   def streamGame(@PathParam("gameId") gameId: String): Response =
-    store.get(gameId) match
-      case None =>
-        Response
-          .status(404)
-          .`type`(MediaType.APPLICATION_JSON)
-          .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
-          .build()
-      case Some(session) =>
-        // Simplified: return a single-line NDJSON snapshot of the current game state
-        val event = s"""{"type":"gameFull","game":${GameMapper.toGameFullJson(session)}}"""
-        Response.ok(event + "\n").build()
+    if !service.isKnownId(gameId) then
+      Response
+        .status(404)
+        .`type`(MediaType.APPLICATION_JSON)
+        .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
+        .build()
+    else
+      val event = s"""{"type":"gameFull","game":${GameMapper.toGameFullJson(service.getSnapshot)}}"""
+      Response.ok(event + "\n").build()
 
   @POST
   @Path("/{gameId}/resign")
   def resignGame(@PathParam("gameId") gameId: String): Response =
-    store.resign(gameId) match
-      case Right(_) => Response.ok(OkResponse()).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("RESIGN_ERROR", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      service.resign() match
+        case Right(_)  => Response.ok(OkResponse()).build()
+        case Left(err) => Response.status(400).entity(ApiErrorResponse("RESIGN_ERROR", err)).build()
 
   @POST
   @Path("/{gameId}/draw/{action}")
@@ -61,39 +58,33 @@ class GameResource @Inject() (store: GameStore):
       @PathParam("gameId") gameId: String,
       @PathParam("action") action: String,
   ): Response =
-    store.drawAction(gameId, action) match
-      case Right(_) => Response.ok(OkResponse()).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("DRAW_ERROR", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      service.drawAction(action) match
+        case Right(_)  => Response.ok(OkResponse()).build()
+        case Left(err) => Response.status(400).entity(ApiErrorResponse("DRAW_ERROR", err)).build()
 
   @GET
   @Path("/{gameId}/export/fen")
   @Produces(Array(MediaType.TEXT_PLAIN))
   def exportFen(@PathParam("gameId") gameId: String): Response =
-    store.get(gameId) match
-      case None =>
-        Response
-          .status(404)
-          .`type`(MediaType.APPLICATION_JSON)
-          .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
-          .build()
-      case Some(session) =>
-        import de.nowchess.io.fen.FenExporter
-        Response.ok(FenExporter.exportGameContext(session.context)).build()
+    if !service.isKnownId(gameId) then
+      Response
+        .status(404)
+        .`type`(MediaType.APPLICATION_JSON)
+        .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
+        .build()
+    else Response.ok(service.exportFen()).build()
 
   @GET
   @Path("/{gameId}/export/pgn")
   @Produces(Array("application/x-chess-pgn"))
   def exportPgn(@PathParam("gameId") gameId: String): Response =
-    store.get(gameId) match
-      case None =>
-        Response
-          .status(404)
-          .`type`(MediaType.APPLICATION_JSON)
-          .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
-          .build()
-      case Some(session) =>
-        import de.nowchess.io.pgn.PgnExporter
-        Response.ok(PgnExporter.exportGameContext(session.context)).build()
+    if !service.isKnownId(gameId) then
+      Response
+        .status(404)
+        .`type`(MediaType.APPLICATION_JSON)
+        .entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found"))
+        .build()
+    else Response.ok(service.exportPgn()).build()

modules/backcore/src/main/scala/de/nowchess/backcore/resource/ImportResource.scala

@@ -1,7 +1,7 @@
 package de.nowchess.backcore.resource
 
 import de.nowchess.backcore.dto.{ApiErrorResponse, ImportFenRequest, ImportPgnRequest}
-import de.nowchess.backcore.game.{GameMapper, GameStore}
+import de.nowchess.backcore.game.{GameMapper, GameService}
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import jakarta.ws.rs.*
@@ -11,19 +11,19 @@ import jakarta.ws.rs.core.{MediaType, Response}
 @Produces(Array(MediaType.APPLICATION_JSON))
 @Consumes(Array(MediaType.APPLICATION_JSON))
 @ApplicationScoped
-class ImportResource @Inject() (store: GameStore):
+class ImportResource @Inject() (service: GameService):
 
   @POST
   @Path("/fen")
   def importFen(req: ImportFenRequest): Response =
-    store.importFen(Option(req).getOrElse(ImportFenRequest())) match
-      case Right(session) => Response.status(201).entity(GameMapper.toGameFull(session)).build()
-      case Left(err)      => Response.status(400).entity(ApiErrorResponse("INVALID_FEN", err)).build()
+    service.importFen(Option(req).getOrElse(ImportFenRequest())) match
+      case Right(snap) => Response.status(201).entity(GameMapper.toGameFull(snap)).build()
+      case Left(err)   => Response.status(400).entity(ApiErrorResponse("INVALID_FEN", err)).build()
 
   @POST
   @Path("/pgn")
   def importPgn(req: ImportPgnRequest): Response =
     val body = Option(req).getOrElse(ImportPgnRequest())
-    store.importPgn(body.pgn, None, None) match
-      case Right(session) => Response.status(201).entity(GameMapper.toGameFull(session)).build()
-      case Left(err)      => Response.status(400).entity(ApiErrorResponse("INVALID_PGN", err)).build()
+    service.importPgn(body.pgn) match
+      case Right(snap) => Response.status(201).entity(GameMapper.toGameFull(snap)).build()
+      case Left(err)   => Response.status(400).entity(ApiErrorResponse("INVALID_PGN", err)).build()

modules/backcore/src/main/scala/de/nowchess/backcore/resource/MoveResource.scala

@@ -3,7 +3,7 @@ package de.nowchess.backcore.resource
 import de.nowchess.api.board.Square
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.backcore.dto.*
-import de.nowchess.backcore.game.{GameMapper, GameStore}
+import de.nowchess.backcore.game.{GameMapper, GameService}
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import jakarta.ws.rs.*
@@ -12,7 +12,7 @@ import jakarta.ws.rs.core.{MediaType, Response}
 @Path("/api/board/game")
 @Produces(Array(MediaType.APPLICATION_JSON))
 @ApplicationScoped
-class MoveResource @Inject() (store: GameStore):
+class MoveResource @Inject() (service: GameService):
 
   @POST
   @Path("/{gameId}/move/{uci}")
@@ -20,12 +20,12 @@ class MoveResource @Inject() (store: GameStore):
       @PathParam("gameId") gameId: String,
       @PathParam("uci") uci: String,
   ): Response =
-    store.applyMove(gameId, uci) match
-      case Right(session) => Response.ok(GameMapper.toGameState(session)).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("INVALID_MOVE", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      service.applyMove(uci) match
+        case Right(snap) => Response.ok(GameMapper.toGameState(snap)).build()
+        case Left(err)   => Response.status(400).entity(ApiErrorResponse("INVALID_MOVE", err)).build()
 
   @GET
   @Path("/{gameId}/moves")
@@ -33,35 +33,33 @@ class MoveResource @Inject() (store: GameStore):
       @PathParam("gameId") gameId: String,
       @QueryParam("square") squareParam: String,
   ): Response =
-    val square = Option(squareParam).flatMap(Square.fromAlgebraic)
-    store.legalMoves(gameId, square) match
-      case Right(moves) =>
-        val dtos = moves.map(toLegalMoveDto)
-        Response.ok(LegalMovesResponse(dtos)).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("ERROR", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      val square = Option(squareParam).flatMap(Square.fromAlgebraic)
+      val moves  = service.legalMoves(square)
+      val dtos   = moves.map(toLegalMoveDto)
+      Response.ok(LegalMovesResponse(dtos)).build()
 
   @POST
   @Path("/{gameId}/undo")
   def undoMove(@PathParam("gameId") gameId: String): Response =
-    store.undo(gameId) match
-      case Right(session) => Response.ok(GameMapper.toGameState(session)).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("UNDO_NOT_AVAILABLE", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      service.undo() match
+        case Right(snap) => Response.ok(GameMapper.toGameState(snap)).build()
+        case Left(err)   => Response.status(400).entity(ApiErrorResponse("UNDO_NOT_AVAILABLE", err)).build()
 
   @POST
   @Path("/{gameId}/redo")
   def redoMove(@PathParam("gameId") gameId: String): Response =
-    store.redo(gameId) match
-      case Right(session) => Response.ok(GameMapper.toGameState(session)).build()
-      case Left(err) if err.contains("not found") =>
-        Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", err)).build()
-      case Left(err) =>
-        Response.status(400).entity(ApiErrorResponse("REDO_NOT_AVAILABLE", err)).build()
+    if !service.isKnownId(gameId) then
+      Response.status(404).entity(ApiErrorResponse("GAME_NOT_FOUND", s"Game $gameId not found")).build()
+    else
+      service.redo() match
+        case Right(snap) => Response.ok(GameMapper.toGameState(snap)).build()
+        case Left(err)   => Response.status(400).entity(ApiErrorResponse("REDO_NOT_AVAILABLE", err)).build()
 
   private def toLegalMoveDto(move: Move): LegalMoveDto =
     val uci = GameMapper.moveToUci(move)

modules/backcore/src/test/scala/de/nowchess/backcore/game/GameMapperTest.scala

@@ -0,0 +1,181 @@
+package de.nowchess.backcore.game
+
+import de.nowchess.api.board.{Color, File, Rank, Square}
+import de.nowchess.api.game.{DrawReason, GameContext, GameResult as ApiGameResult}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+class GameMapperTest:
+
+  private val white = PlayerInfo(PlayerId("white"), "White")
+  private val black = PlayerInfo(PlayerId("black"), "Black")
+
+  private def snap(
+      ctx: GameContext = GameContext.initial,
+      externalResult: Option[GameResult] = None,
+      drawOfferedBy: Option[Color] = None,
+      canUndo: Boolean = false,
+      canRedo: Boolean = false,
+  ): GameSnapshot =
+    GameSnapshot(
+      gameId = "testId1",
+      white = white,
+      black = black,
+      context = ctx,
+      drawOfferedBy = drawOfferedBy,
+      externalResult = externalResult,
+      canUndo = canUndo,
+      canRedo = canRedo,
+    )
+
+  @Test
+  def resignWhiteReturnsResignWithWhiteWinner(): Unit =
+    val state = GameMapper.toGameState(snap(externalResult = Some(GameResult.Resign(Color.White))))
+    assertEquals("resign", state.status)
+    assertEquals(Some("white"), state.winner)
+
+  @Test
+  def resignBlackReturnsResignWithBlackWinner(): Unit =
+    val state = GameMapper.toGameState(snap(externalResult = Some(GameResult.Resign(Color.Black))))
+    assertEquals("resign", state.status)
+    assertEquals(Some("black"), state.winner)
+
+  @Test
+  def agreedDrawReturnsDrawNoWinner(): Unit =
+    val state = GameMapper.toGameState(snap(externalResult = Some(GameResult.AgreedDraw)))
+    assertEquals("draw", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def fiftyMoveDrawReturnsDrawNoWinner(): Unit =
+    val state = GameMapper.toGameState(snap(externalResult = Some(GameResult.FiftyMoveDraw)))
+    assertEquals("draw", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def contextWinWhiteReturnsCheckmate(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Win(Color.White)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("checkmate", state.status)
+    assertEquals(Some("white"), state.winner)
+
+  @Test
+  def contextWinBlackReturnsCheckmate(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Win(Color.Black)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("checkmate", state.status)
+    assertEquals(Some("black"), state.winner)
+
+  @Test
+  def contextDrawStalemateReturnsStalemate(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Draw(DrawReason.Stalemate)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("stalemate", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def contextDrawInsufficientMaterialReturnsInsufficientMaterial(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Draw(DrawReason.InsufficientMaterial)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("insufficientMaterial", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def contextDrawFiftyMoveRuleReturnsDraw(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Draw(DrawReason.FiftyMoveRule)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("draw", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def contextDrawAgreementReturnsDraw(): Unit =
+    val ctx   = GameContext.initial.withResult(Some(ApiGameResult.Draw(DrawReason.Agreement)))
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("draw", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def liveDrawOfferedBySetReturnsDrawOffered(): Unit =
+    val state = GameMapper.toGameState(snap(drawOfferedBy = Some(Color.White)))
+    assertEquals("drawOffered", state.status)
+
+  @Test
+  def liveFiftyMoveClockGe100ReturnsFiftyMoveAvailable(): Unit =
+    val ctx   = GameContext.initial.withHalfMoveClock(100)
+    val state = GameMapper.toGameState(snap(ctx = ctx))
+    assertEquals("fiftyMoveAvailable", state.status)
+
+  @Test
+  def liveNormalPositionReturnsStarted(): Unit =
+    val state = GameMapper.toGameState(snap())
+    assertEquals("started", state.status)
+    assertEquals(None, state.winner)
+
+  @Test
+  def canUndoReflectedInToGameState(): Unit =
+    val state = GameMapper.toGameState(snap(canUndo = true, canRedo = false))
+    assertTrue(state.undoAvailable)
+    assertFalse(state.redoAvailable)
+
+  @Test
+  def canRedoReflectedInToGameState(): Unit =
+    val state = GameMapper.toGameState(snap(canUndo = false, canRedo = true))
+    assertFalse(state.undoAvailable)
+    assertTrue(state.redoAvailable)
+
+  @Test
+  def moveToUciNormalQuiet(): Unit =
+    val sq   = Square(File.E, Rank.R2)
+    val sq2  = Square(File.E, Rank.R4)
+    val move = Move(sq, sq2, MoveType.Normal(false))
+    assertEquals("e2e4", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciNormalCapture(): Unit =
+    val move = Move(Square(File.D, Rank.R4), Square(File.E, Rank.R5), MoveType.Normal(true))
+    assertEquals("d4e5", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciCastleKingside(): Unit =
+    val move = Move(Square(File.E, Rank.R1), Square(File.G, Rank.R1), MoveType.CastleKingside)
+    assertEquals("e1g1", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciCastleQueenside(): Unit =
+    val move = Move(Square(File.E, Rank.R1), Square(File.C, Rank.R1), MoveType.CastleQueenside)
+    assertEquals("e1c1", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciEnPassant(): Unit =
+    val move = Move(Square(File.E, Rank.R5), Square(File.D, Rank.R6), MoveType.EnPassant)
+    assertEquals("e5d6", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciPromotionQueen(): Unit =
+    val move = Move(Square(File.E, Rank.R7), Square(File.E, Rank.R8), MoveType.Promotion(PromotionPiece.Queen))
+    assertEquals("e7e8q", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciPromotionRook(): Unit =
+    val move = Move(Square(File.E, Rank.R7), Square(File.E, Rank.R8), MoveType.Promotion(PromotionPiece.Rook))
+    assertEquals("e7e8r", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciPromotionBishop(): Unit =
+    val move = Move(Square(File.E, Rank.R7), Square(File.E, Rank.R8), MoveType.Promotion(PromotionPiece.Bishop))
+    assertEquals("e7e8b", GameMapper.moveToUci(move))
+
+  @Test
+  def moveToUciPromotionKnight(): Unit =
+    val move = Move(Square(File.E, Rank.R7), Square(File.E, Rank.R8), MoveType.Promotion(PromotionPiece.Knight))
+    assertEquals("e7e8n", GameMapper.moveToUci(move))
+
+  @Test
+  def toGameFullPopulatesAllFields(): Unit =
+    val full = GameMapper.toGameFull(snap())
+    assertEquals("testId1", full.gameId)
+    assertEquals("white", full.white.id)
+    assertEquals("black", full.black.id)
+    assertNotNull(full.state)

modules/backcore/src/test/scala/de/nowchess/backcore/game/GameServiceTest.scala

@@ -0,0 +1,245 @@
+package de.nowchess.backcore.game
+
+import de.nowchess.api.board.{Color, File, Rank, Square}
+import de.nowchess.backcore.dto.{CreateGameRequest, ImportFenRequest, PlayerInfoDto}
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.{BeforeEach, Test}
+
+class GameServiceTest:
+
+  private val promotionFen = "8/4P3/8/8/8/8/8/4K2k w - - 0 1"
+
+  private def freshService(): GameService =
+    val svc = new GameService()
+    svc.reset(CreateGameRequest())
+    svc
+
+  @Test
+  def resetClearsStateAndReturnsSnapshot(): Unit =
+    val svc = freshService()
+    svc.resign()
+    val snap = svc.reset(CreateGameRequest())
+    assertEquals(GameEngineHolder.gameId, snap.gameId)
+    assertEquals(None, snap.externalResult)
+    assertEquals(None, snap.drawOfferedBy)
+
+  @Test
+  def resetWithPlayersUpdatesHolderInfo(): Unit =
+    val svc = freshService()
+    val req = CreateGameRequest(
+      white = Some(PlayerInfoDto("p1", "Alice")),
+      black = Some(PlayerInfoDto("p2", "Bob")),
+    )
+    val snap = svc.reset(req)
+    assertEquals("Alice", snap.white.displayName)
+    assertEquals("Bob", snap.black.displayName)
+
+  @Test
+  def applyMoveInvalidUciReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.applyMove("zzzz")
+    assertTrue(result.isLeft)
+
+  @Test
+  def applyMoveIllegalMoveReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.applyMove("e2e5")
+    assertTrue(result.isLeft)
+
+  @Test
+  def applyMoveValidMoveReturnsRightWithUpdatedContext(): Unit =
+    val svc    = freshService()
+    val result = svc.applyMove("e2e4")
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertEquals(Color.Black, snap.context.turn)
+
+  @Test
+  def applyMoveWhenGameOverReturnsLeft(): Unit =
+    val svc = freshService()
+    svc.resign()
+    val result = svc.applyMove("e2e4")
+    assertTrue(result.isLeft)
+    assertTrue(result.left.getOrElse("").contains("Game is already over"))
+
+  @Test
+  def legalMovesNoneReturnsNonEmptyListAtStart(): Unit =
+    val svc   = freshService()
+    val moves = svc.legalMoves(None)
+    assertFalse(moves.isEmpty)
+
+  @Test
+  def legalMovesForE2ReturnsE2e3AndE2e4(): Unit =
+    val svc   = freshService()
+    val e2    = Square(File.E, Rank.R2)
+    val moves = svc.legalMoves(Some(e2))
+    val ucis  = moves.map(m => s"${m.from}${m.to}")
+    assertTrue(ucis.contains("e2e3"), s"Expected e2e3 in $ucis")
+    assertTrue(ucis.contains("e2e4"), s"Expected e2e4 in $ucis")
+
+  @Test
+  def undoWithNoHistoryReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.undo()
+    assertTrue(result.isLeft)
+
+  @Test
+  def undoAfterMoveReverts(): Unit =
+    val svc = freshService()
+    svc.applyMove("e2e4")
+    val result = svc.undo()
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertEquals(Color.White, snap.context.turn)
+
+  @Test
+  def redoWithNoRedoStackReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.redo()
+    assertTrue(result.isLeft)
+
+  @Test
+  def redoAfterUndoReturnsRight(): Unit =
+    val svc = freshService()
+    svc.applyMove("e2e4")
+    svc.undo()
+    val result = svc.redo()
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertEquals(Color.Black, snap.context.turn)
+
+  @Test
+  def resignNormalReturnsRight(): Unit =
+    val svc    = freshService()
+    val result = svc.resign()
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertTrue(snap.externalResult.isDefined)
+    snap.externalResult match
+      case Some(GameResult.Resign(_)) => ()
+      case other                      => fail(s"Expected Resign but got $other")
+
+  @Test
+  def resignWhenAlreadyResignedReturnsLeft(): Unit =
+    val svc = freshService()
+    svc.resign()
+    val result = svc.resign()
+    assertTrue(result.isLeft)
+
+  @Test
+  def drawActionOfferSetsDrawOfferedBy(): Unit =
+    val svc    = freshService()
+    val result = svc.drawAction("offer")
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertTrue(snap.drawOfferedBy.isDefined)
+
+  @Test
+  def drawActionAcceptWithNoOfferReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.drawAction("accept")
+    assertTrue(result.isLeft)
+
+  @Test
+  def drawActionAcceptOwnOfferReturnsLeft(): Unit =
+    val svc = freshService()
+    svc.drawAction("offer")
+    val result = svc.drawAction("accept")
+    assertTrue(result.isLeft)
+    assertTrue(result.left.getOrElse("").contains("Cannot accept your own draw offer"))
+
+  @Test
+  def drawActionAcceptOpponentAcceptsReturnsAgreedDraw(): Unit =
+    val svc = freshService()
+    svc.drawAction("offer")
+    svc.applyMove("e2e4")
+    val result = svc.drawAction("accept")
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertEquals(Some(GameResult.AgreedDraw), snap.externalResult)
+
+  @Test
+  def drawActionDeclineWithNoOfferReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.drawAction("decline")
+    assertTrue(result.isLeft)
+
+  @Test
+  def drawActionDeclineAfterOfferClearsOffer(): Unit =
+    val svc = freshService()
+    svc.drawAction("offer")
+    val result = svc.drawAction("decline")
+    assertTrue(result.isRight)
+    val snap = result.getOrElse(fail("Expected Right"))
+    assertEquals(None, snap.drawOfferedBy)
+
+  @Test
+  def drawActionClaimWhenFiftyMoveNotTriggeredReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.drawAction("claim")
+    assertTrue(result.isLeft)
+
+  @Test
+  def drawActionUnknownReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.drawAction("unknown")
+    assertTrue(result.isLeft)
+
+  @Test
+  def importFenValidReturnsRight(): Unit =
+    val svc    = freshService()
+    val result = svc.importFen(ImportFenRequest(fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"))
+    assertTrue(result.isRight)
+
+  @Test
+  def importFenInvalidReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.importFen(ImportFenRequest(fen = "not-a-fen"))
+    assertTrue(result.isLeft)
+
+  @Test
+  def importPgnValidReturnsRight(): Unit =
+    val svc    = freshService()
+    val result = svc.importPgn("1. e4 e5 2. Nf3 Nc6 *")
+    assertTrue(result.isRight)
+
+  @Test
+  def importPgnInvalidReturnsLeft(): Unit =
+    val svc    = freshService()
+    val result = svc.importPgn("1. z9 *")
+    assertTrue(result.isLeft)
+
+  @Test
+  def exportFenReturnsNonEmptyString(): Unit =
+    val svc = freshService()
+    val fen = svc.exportFen()
+    assertFalse(fen.isEmpty)
+
+  @Test
+  def exportPgnReturnsString(): Unit =
+    val svc = freshService()
+    val pgn = svc.exportPgn()
+    assertNotNull(pgn)
+
+  @Test
+  def isKnownIdTrueForHolderGameId(): Unit =
+    val svc = freshService()
+    assertTrue(svc.isKnownId(GameEngineHolder.gameId))
+
+  @Test
+  def isKnownIdFalseForOtherId(): Unit =
+    val svc = freshService()
+    assertFalse(svc.isKnownId("XXXXXXXX"))
+
+  @Test
+  def applyMovePromotionQueenProducesQueen(): Unit =
+    val svc = freshService()
+    svc.importFen(ImportFenRequest(fen = promotionFen))
+    val result = svc.applyMove("e7e8q")
+    assertTrue(result.isRight, s"Expected Right but got $result")
+    val snap = result.getOrElse(fail("Expected Right"))
+    val e8   = Square(File.E, Rank.R8)
+    snap.context.board.pieceAt(e8) match
+      case Some(piece) =>
+        assertEquals(de.nowchess.api.board.PieceType.Queen, piece.pieceType)
+      case None => fail("Expected queen on e8")

modules/ui/build.gradle.kts

@@ -90,6 +90,14 @@ dependencies {
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }
 
+configurations.scoverage {
+    resolutionStrategy.eachDependency {
+        if (requested.group == "org.scoverage" && requested.name.startsWith("scalac-scoverage-plugin_")) {
+            useTarget("${requested.group}:scalac-scoverage-plugin_2.13.16:2.3.0")
+        }
+    }
+}
+
 tasks.test {
     useJUnitPlatform {
         includeEngines("scalatest")

modules/ui/src/main/scala/de/nowchess/ui/Main.scala

@@ -1,20 +1,15 @@
 package de.nowchess.ui
 
 import de.nowchess.chess.engine.GameEngine
-import de.nowchess.ui.terminal.TerminalUI
 import de.nowchess.ui.gui.ChessGUILauncher
+import de.nowchess.ui.terminal.TerminalUI
 
 /** Application entry point - starts both GUI and Terminal UI for the chess game. Both views subscribe to the same
   * GameEngine via Observer pattern.
   */
 object Main:
   def main(args: Array[String]): Unit =
-    // Create the core game engine (single source of truth)
     val engine = new GameEngine()
-
-    // Launch ScalaFX GUI in separate thread
     ChessGUILauncher.launch(engine)
-
-    // Create and start the terminal UI (blocks on main thread)
     val tui = new TerminalUI(engine)
     tui.start()