feat: NCS-37 Add initial API structure and DTOs for NowChess application

modules/core/src/main/scala/de/nowchess/chess/config/JacksonConfig.scala

@@ -0,0 +1,11 @@
+package de.nowchess.chess.config
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+import io.quarkus.jackson.ObjectMapperCustomizer
+import jakarta.inject.Singleton
+
+@Singleton
+class JacksonConfig extends ObjectMapperCustomizer:
+  def customize(mapper: ObjectMapper): Unit =
+    mapper.registerModule(DefaultScalaModule)

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

@@ -258,6 +258,22 @@ class GameEngine(
     notifyObservers(BoardResetEvent(currentContext))
   }
 
+  /** Resign the game on behalf of the side to move. */
+  def resign(): Unit = synchronized {
+    if currentContext.result.isEmpty then
+      val winner = currentContext.turn.opposite
+      currentContext = currentContext.withResult(Some(GameResult.Win(winner)))
+      invoker.clear()
+  }
+
+  /** Apply a draw result directly (for agreement, fifty-move claim, etc.). */
+  def applyDraw(reason: DrawReason): Unit = synchronized {
+    if currentContext.result.isEmpty then
+      currentContext = currentContext.withResult(Some(GameResult.Draw(reason)))
+      invoker.clear()
+      notifyObservers(DrawEvent(currentContext, reason))
+  }
+
   /** Kick off play when the side to move is a bot (e.g. bot-vs-bot from initial position). */
   def startGame(): Unit = synchronized(requestBotMoveIfNeeded())
 

modules/core/src/main/scala/de/nowchess/chess/exception/ApiException.scala

@@ -0,0 +1,13 @@
+package de.nowchess.chess.exception
+
+class ApiException(
+    val status: Int,
+    val code: String,
+    message: String,
+    val field: Option[String] = None,
+) extends RuntimeException(message)
+
+class GameNotFoundException(gameId: String) extends ApiException(404, "GAME_NOT_FOUND", s"Game $gameId not found")
+
+class BadRequestException(code: String, message: String, field: Option[String] = None)
+    extends ApiException(400, code, message, field)

modules/core/src/main/scala/de/nowchess/chess/exception/ApiExceptionMapper.scala

@@ -0,0 +1,14 @@
+package de.nowchess.chess.exception
+
+import de.nowchess.api.dto.ApiErrorDto
+import jakarta.ws.rs.core.{MediaType, Response}
+import jakarta.ws.rs.ext.{ExceptionMapper, Provider}
+
+@Provider
+class ApiExceptionMapper extends ExceptionMapper[ApiException]:
+  def toResponse(ex: ApiException): Response =
+    Response
+      .status(ex.status)
+      .entity(ApiErrorDto(ex.code, ex.getMessage, ex.field))
+      .`type`(MediaType.APPLICATION_JSON)
+      .build()

modules/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala

@@ -0,0 +1,14 @@
+package de.nowchess.chess.registry
+
+import de.nowchess.api.board.Color
+import de.nowchess.api.player.PlayerInfo
+import de.nowchess.chess.engine.GameEngine
+
+final case class GameEntry(
+    gameId: String,
+    engine: GameEngine,
+    white: PlayerInfo,
+    black: PlayerInfo,
+    drawOfferedBy: Option[Color] = None,
+    resigned: Boolean = false,
+)

modules/core/src/main/scala/de/nowchess/chess/registry/GameRegistry.scala

@@ -0,0 +1,7 @@
+package de.nowchess.chess.registry
+
+trait GameRegistry:
+  def store(entry: GameEntry): Unit
+  def get(gameId: String): Option[GameEntry]
+  def update(entry: GameEntry): Unit
+  def generateId(): String

modules/core/src/main/scala/de/nowchess/chess/registry/GameRegistryImpl.scala

@@ -0,0 +1,22 @@
+package de.nowchess.chess.registry
+
+import jakarta.enterprise.context.ApplicationScoped
+import java.util.concurrent.ConcurrentHashMap
+import scala.util.Random
+
+@ApplicationScoped
+class GameRegistryImpl extends GameRegistry:
+  private val games = ConcurrentHashMap[String, GameEntry]()
+
+  def store(entry: GameEntry): Unit =
+    games.put(entry.gameId, entry)
+
+  def get(gameId: String): Option[GameEntry] =
+    Option(games.get(gameId))
+
+  def update(entry: GameEntry): Unit =
+    games.put(entry.gameId, entry)
+
+  def generateId(): String =
+    val chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+    Iterator.continually(Random.nextInt(chars.length)).map(chars).take(8).mkString

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

@@ -0,0 +1,306 @@
+package de.nowchess.chess.resource
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import de.nowchess.api.board.Square
+import de.nowchess.api.dto.*
+import de.nowchess.api.game.{DrawReason, GameContext, GameResult}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.chess.controller.Parser
+import de.nowchess.chess.engine.GameEngine
+import de.nowchess.chess.exception.{BadRequestException, GameNotFoundException}
+import de.nowchess.chess.observer.*
+import de.nowchess.chess.registry.{GameEntry, GameRegistry}
+import de.nowchess.io.fen.{FenExporter, FenParser}
+import de.nowchess.io.pgn.{PgnExporter, PgnParser}
+import io.smallrye.mutiny.Multi
+import jakarta.enterprise.context.ApplicationScoped
+import jakarta.inject.Inject
+import jakarta.ws.rs.*
+import jakarta.ws.rs.core.{MediaType, Response}
+
+import java.util.concurrent.atomic.AtomicReference
+
+@Path("/api/board/game")
+@ApplicationScoped
+class GameResource(@Inject val registry: GameRegistry, @Inject val objectMapper: ObjectMapper):
+
+  private val DefaultWhite = PlayerInfo(PlayerId("p1"), "Player 1")
+  private val DefaultBlack = PlayerInfo(PlayerId("p2"), "Player 2")
+
+  // ── mapping ──────────────────────────────────────────────────────────────
+
+  private def statusOf(entry: GameEntry): String =
+    if entry.drawOfferedBy.isDefined then "drawOffered"
+    else
+      val ctx = entry.engine.context
+      ctx.result match
+        case Some(GameResult.Win(_)) =>
+          if entry.resigned then "resign" else "checkmate"
+        case Some(GameResult.Draw(DrawReason.Stalemate))            => "stalemate"
+        case Some(GameResult.Draw(DrawReason.InsufficientMaterial)) => "insufficientMaterial"
+        case Some(GameResult.Draw(_))                               => "draw"
+        case None =>
+          if ctx.halfMoveClock >= 100 then "fiftyMoveAvailable"
+          else if entry.engine.ruleSet.isCheck(ctx) then "check"
+          else "started"
+
+  private def moveToUci(move: Move): String =
+    val base = s"${move.from}${move.to}"
+    move.moveType match
+      case MoveType.Promotion(PromotionPiece.Queen)  => s"${base}q"
+      case MoveType.Promotion(PromotionPiece.Rook)   => s"${base}r"
+      case MoveType.Promotion(PromotionPiece.Bishop) => s"${base}b"
+      case MoveType.Promotion(PromotionPiece.Knight) => s"${base}n"
+      case _                                         => base
+
+  private def toLegalMoveDto(move: Move): LegalMoveDto =
+    val (moveTypeStr, promotionStr) = move.moveType match
+      case MoveType.Normal(false)                    => ("normal", None)
+      case MoveType.Normal(true)                     => ("capture", None)
+      case MoveType.CastleKingside                   => ("castleKingside", None)
+      case MoveType.CastleQueenside                  => ("castleQueenside", None)
+      case MoveType.EnPassant                        => ("enPassant", None)
+      case MoveType.Promotion(PromotionPiece.Queen)  => ("promotion", Some("queen"))
+      case MoveType.Promotion(PromotionPiece.Rook)   => ("promotion", Some("rook"))
+      case MoveType.Promotion(PromotionPiece.Bishop) => ("promotion", Some("bishop"))
+      case MoveType.Promotion(PromotionPiece.Knight) => ("promotion", Some("knight"))
+    LegalMoveDto(move.from.toString, move.to.toString, moveToUci(move), moveTypeStr, promotionStr)
+
+  private def toPlayerDto(info: PlayerInfo): PlayerInfoDto =
+    PlayerInfoDto(info.id.value, info.displayName)
+
+  private def toGameStateDto(entry: GameEntry): GameStateDto =
+    val ctx = entry.engine.context
+    GameStateDto(
+      fen = FenExporter.exportGameContext(ctx),
+      pgn = PgnExporter.exportGame(
+        Map(
+          "Event"  -> "NowChess game",
+          "White"  -> entry.white.displayName,
+          "Black"  -> entry.black.displayName,
+          "Result" -> "*",
+        ),
+        ctx.moves,
+      ),
+      turn = ctx.turn.label.toLowerCase,
+      status = statusOf(entry),
+      winner = ctx.result.collect { case GameResult.Win(c) => c.label.toLowerCase },
+      moves = ctx.moves.map(moveToUci),
+      undoAvailable = entry.engine.canUndo,
+      redoAvailable = entry.engine.canRedo,
+    )
+
+  private def toGameFullDto(entry: GameEntry): GameFullDto =
+    GameFullDto(entry.gameId, toPlayerDto(entry.white), toPlayerDto(entry.black), toGameStateDto(entry))
+
+  private def playerInfoFrom(dto: Option[PlayerInfoDto], default: PlayerInfo): PlayerInfo =
+    dto.fold(default)(d => PlayerInfo(PlayerId(d.id), d.displayName))
+
+  private def newEntry(ctx: GameContext, white: PlayerInfo, black: PlayerInfo): GameEntry =
+    GameEntry(registry.generateId(), GameEngine(initialContext = ctx), white, black)
+
+  private def applyMoveInput(engine: GameEngine, uci: String): Option[String] =
+    val error = new AtomicReference[Option[String]](None)
+    val obs = new Observer:
+      def onGameEvent(e: GameEvent): Unit = e match
+        case InvalidMoveEvent(_, reason) => error.set(Some(reason))
+        case _                           => ()
+    engine.subscribe(obs)
+    engine.processUserInput(uci)
+    engine.unsubscribe(obs)
+    error.get()
+
+  // ── response helpers ─────────────────────────────────────────────────────
+
+  private def ok(body: AnyRef): Response      = Response.ok(body).build()
+  private def created(body: AnyRef): Response = Response.status(Response.Status.CREATED).entity(body).build()
+
+  // ── endpoints ────────────────────────────────────────────────────────────
+  // scalafix:off DisableSyntax.throw
+
+  @POST
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def createGame(body: CreateGameRequestDto): Response =
+    val req   = Option(body).getOrElse(CreateGameRequestDto(None, None))
+    val white = playerInfoFrom(req.white, DefaultWhite)
+    val black = playerInfoFrom(req.black, DefaultBlack)
+    val entry = newEntry(GameContext.initial, white, black)
+    registry.store(entry)
+    created(toGameFullDto(entry))
+
+  @GET
+  @Path("/{gameId}")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def getGame(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    ok(toGameFullDto(entry))
+
+  @GET
+  @Path("/{gameId}/stream")
+  @Produces(Array("application/x-ndjson"))
+  def streamGame(@PathParam("gameId") gameId: String): Multi[String] =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    Multi
+      .createFrom()
+      .emitter[String] { emitter =>
+        emitter.emit(objectMapper.writeValueAsString(GameFullEventDto(toGameFullDto(entry))) + "\n")
+        val obs = new Observer:
+          def onGameEvent(event: GameEvent): Unit =
+            registry.get(gameId).foreach { updated =>
+              emitter.emit(
+                objectMapper.writeValueAsString(GameStateEventDto(toGameStateDto(updated))) + "\n",
+              )
+            }
+        entry.engine.subscribe(obs)
+        emitter.onTermination(() => entry.engine.unsubscribe(obs))
+      }
+
+  @POST
+  @Path("/{gameId}/resign")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def resignGame(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    if entry.engine.context.result.isDefined then throw BadRequestException("GAME_OVER", "Game is already over")
+    entry.engine.resign()
+    registry.update(entry.copy(resigned = true))
+    ok(OkResponseDto())
+
+  @POST
+  @Path("/{gameId}/move/{uci}")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def makeMove(@PathParam("gameId") gameId: String, @PathParam("uci") uci: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    if entry.engine.context.result.isDefined then throw BadRequestException("GAME_OVER", "Game is already over")
+    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"))
+    applyMoveInput(entry.engine, uci).foreach(err => throw BadRequestException("INVALID_MOVE", err, Some("uci")))
+    ok(toGameStateDto(entry))
+
+  @GET
+  @Path("/{gameId}/moves")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def getLegalMoves(
+      @PathParam("gameId") gameId: String,
+      @QueryParam("square") square: String,
+  ): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    val ctx   = entry.engine.context
+    val moves =
+      if Option(square).isEmpty || square.isEmpty then entry.engine.ruleSet.allLegalMoves(ctx)
+      else
+        val sq = Square
+          .fromAlgebraic(square)
+          .getOrElse(throw BadRequestException("INVALID_SQUARE", s"Invalid square: $square", Some("square")))
+        entry.engine.ruleSet.legalMoves(ctx)(sq)
+    ok(LegalMovesResponseDto(moves.map(toLegalMoveDto)))
+
+  @POST
+  @Path("/{gameId}/undo")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def undoMove(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    if !entry.engine.canUndo then throw BadRequestException("NO_UNDO", "No moves to undo")
+    entry.engine.undo()
+    ok(toGameStateDto(entry))
+
+  @POST
+  @Path("/{gameId}/redo")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def redoMove(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    if !entry.engine.canRedo then throw BadRequestException("NO_REDO", "No moves to redo")
+    entry.engine.redo()
+    ok(toGameStateDto(entry))
+
+  @POST
+  @Path("/{gameId}/draw/{action}")
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def drawAction(
+      @PathParam("gameId") gameId: String,
+      @PathParam("action") action: String,
+  ): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    if entry.engine.context.result.isDefined then throw BadRequestException("GAME_OVER", "Game is already over")
+    action match
+      case "offer" =>
+        registry.update(entry.copy(drawOfferedBy = Some(entry.engine.context.turn)))
+        ok(OkResponseDto())
+      case "accept" =>
+        entry.drawOfferedBy match
+          case None =>
+            throw BadRequestException("NO_DRAW_OFFER", "No draw offer to accept")
+          case Some(offerer) if offerer == entry.engine.context.turn =>
+            throw BadRequestException("CANNOT_ACCEPT_OWN_OFFER", "Cannot accept your own draw offer")
+          case _ =>
+            entry.engine.applyDraw(DrawReason.Agreement)
+            registry.update(entry.copy(drawOfferedBy = None))
+            ok(OkResponseDto())
+      case "decline" =>
+        if entry.drawOfferedBy.isEmpty then throw BadRequestException("NO_DRAW_OFFER", "No draw offer to decline")
+        registry.update(entry.copy(drawOfferedBy = None))
+        ok(OkResponseDto())
+      case "claim" =>
+        if entry.engine.context.halfMoveClock < 100 then
+          throw BadRequestException("CLAIM_NOT_AVAILABLE", "Fifty-move rule draw is not available")
+        entry.engine.applyDraw(DrawReason.FiftyMoveRule)
+        ok(OkResponseDto())
+      case _ =>
+        throw BadRequestException("INVALID_ACTION", s"Unknown draw action: $action", Some("action"))
+
+  @POST
+  @Path("/import/fen")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def importFen(body: ImportFenRequestDto): Response =
+    val ctx = FenParser.parseFen(body.fen) match
+      case Left(err)  => throw BadRequestException("INVALID_FEN", err, Some("fen"))
+      case Right(ctx) => ctx
+    val white = playerInfoFrom(body.white, DefaultWhite)
+    val black = playerInfoFrom(body.black, DefaultBlack)
+    val entry = newEntry(ctx, white, black)
+    registry.store(entry)
+    created(toGameFullDto(entry))
+
+  @POST
+  @Path("/import/pgn")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def importPgn(body: ImportPgnRequestDto): Response =
+    val engine = GameEngine()
+    engine.loadGame(PgnParser, body.pgn) match
+      case Left(err) => throw BadRequestException("INVALID_PGN", err, Some("pgn"))
+      case Right(_)  => ()
+    val entry = GameEntry(registry.generateId(), engine, DefaultWhite, DefaultBlack)
+    registry.store(entry)
+    created(toGameFullDto(entry))
+
+  @GET
+  @Path("/{gameId}/export/fen")
+  @Produces(Array(MediaType.TEXT_PLAIN))
+  def exportFen(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    ok(FenExporter.exportGameContext(entry.engine.context))
+
+  @GET
+  @Path("/{gameId}/export/pgn")
+  @Produces(Array("application/x-chess-pgn"))
+  def exportPgn(@PathParam("gameId") gameId: String): Response =
+    val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
+    val pgn = PgnExporter.exportGame(
+      Map(
+        "Event"  -> "NowChess game",
+        "White"  -> entry.white.displayName,
+        "Black"  -> entry.black.displayName,
+        "Result" -> "*",
+      ),
+      entry.engine.context.moves,
+    )
+    ok(pgn)
+  // scalafix:on DisableSyntax.throw