Improve concurrency

Fix GameState.currentPlayerTurn and nextPlayer
Add ItsTheTurnOfNotification
Improve test

src/main/kotlin/eventDemo/app/command/GameCommandHandler.kt

@@ -15,7 +15,6 @@ import io.github.oshai.kotlinlogging.KotlinLogging
 import io.ktor.websocket.Frame
 import kotlinx.coroutines.channels.ReceiveChannel
 import kotlinx.coroutines.channels.SendChannel
-import kotlinx.coroutines.channels.trySendBlocking
 
 /**
  * Listen [GameCommand] on [GameCommandStream], check the validity and execute an action.
@@ -33,29 +32,20 @@ class GameCommandHandler(
      */
     suspend fun handle(
         player: Player,
-        incoming: ReceiveChannel<Frame>,
+        incomingCommandChannel: ReceiveChannel<Frame>,
-        outgoing: SendChannel<Frame>,
+        outgoingErrorChannelNotification: SendChannel<Frame>,
-    ) {
+    ) = GameCommandStream(incomingCommandChannel).process { command ->
-        val commandStream = GameCommandStream(incoming)
+        if (command.payload.player.id != player.id) {
-        val playerErrorNotifier: (String) -> Unit = {
+            nack()
+        }
+
+        val playerErrorNotifier: suspend (String) -> Unit = {
             val notification = ErrorNotification(message = it)
-            logger.atInfo {
+            logger.atWarn {
                 message = "Notification send ERROR: ${notification.message}"
                 payload = mapOf("notification" to notification)
             }
-            outgoing.trySendBlocking(notification.toFrame())
+            outgoingErrorChannelNotification.send(notification.toFrame())
-        }
-        return init(player, commandStream, playerErrorNotifier)
-    }
-
-    private suspend fun init(
-        player: Player,
-        commandStream: GameCommandStream,
-        playerErrorNotifier: (String) -> Unit,
-    ) {
-        commandStream.process { command ->
-            if (command.payload.player.id != player.id) {
-                nack()
         }
 
         val gameState = gameStateRepository.get(command.payload.gameId)
@@ -68,4 +58,3 @@ class GameCommandHandler(
         }
     }
 }
-}

src/main/kotlin/eventDemo/app/command/command/ICantPlayCommand.kt

@@ -23,11 +23,15 @@ data class ICantPlayCommand(
         override val player: Player,
     ) : GameCommand.Payload
 
-    fun run(
+    suspend fun run(
         state: GameState,
-        playerErrorNotifier: (String) -> Unit,
+        playerErrorNotifier: suspend (String) -> Unit,
         eventHandler: GameEventHandler,
     ) {
+        if (state.currentPlayerTurn != payload.player) {
+            playerErrorNotifier("Its not your turn!")
+            return
+        }
         val playableCards = state.playableCards(payload.player)
         if (playableCards.isEmpty()) {
             val takenCard = state.deck.stack.first()

src/main/kotlin/eventDemo/app/command/command/IWantToJoinTheGameCommand.kt

@@ -24,9 +24,9 @@ data class IWantToJoinTheGameCommand(
         override val player: Player,
     ) : GameCommand.Payload
 
-    fun run(
+    suspend fun run(
         state: GameState,
-        playerErrorNotifier: (String) -> Unit,
+        playerErrorNotifier: suspend (String) -> Unit,
         eventHandler: GameEventHandler,
     ) {
         val logger = KotlinLogging.logger {}

src/main/kotlin/eventDemo/app/command/command/IWantToPlayCardCommand.kt

@@ -25,15 +25,19 @@ data class IWantToPlayCardCommand(
         val card: Card,
     ) : GameCommand.Payload
 
-    fun run(
+    suspend fun run(
         state: GameState,
-        playerErrorNotifier: (String) -> Unit,
+        playerErrorNotifier: suspend (String) -> Unit,
         eventHandler: GameEventHandler,
     ) {
         if (!state.isStarted) {
             playerErrorNotifier("The game is Not started")
             return
         }
+        if (state.currentPlayerTurn != payload.player) {
+            playerErrorNotifier("Its not your turn!")
+            return
+        }
 
         if (state.canBePlayThisCard(payload.player, payload.card)) {
             eventHandler.handle(

src/main/kotlin/eventDemo/app/command/command/IamReadyToPlayCommand.kt

@@ -23,9 +23,9 @@ data class IamReadyToPlayCommand(
         override val player: Player,
     ) : GameCommand.Payload
 
-    fun run(
+    suspend fun run(
         state: GameState,
-        playerErrorNotifier: (String) -> Unit,
+        playerErrorNotifier: suspend (String) -> Unit,
         eventHandler: GameEventHandler,
     ) {
         val playerExist: Boolean = state.players.contains(payload.player)

src/main/kotlin/eventDemo/app/event/event/CardIsPlayedEvent.kt

@@ -11,6 +11,7 @@ import java.util.UUID
 data class CardIsPlayedEvent(
     override val gameId: GameId,
     val card: Card,
-    val player: Player,
+    override val player: Player,
     override val eventId: UUID = UUID.randomUUID(),
-) : GameEvent
+) : GameEvent,
+    PlayerActionEvent

src/main/kotlin/eventDemo/app/event/event/PlayerActionEvent.kt

@@ -0,0 +1,7 @@
+package eventDemo.app.event.event
+
+import eventDemo.app.entity.Player
+
+sealed interface PlayerActionEvent {
+    val player: Player
+}

src/main/kotlin/eventDemo/app/event/event/PlayerChoseColorEvent.kt

@@ -10,8 +10,9 @@ import java.util.UUID
  */
 data class PlayerChoseColorEvent(
     override val gameId: GameId,
-    val player: Player,
+    override val player: Player,
     val color: Card.Color,
-) : GameEvent {
+) : GameEvent,
+    PlayerActionEvent {
     override val eventId: UUID = UUID.randomUUID()
 }

src/main/kotlin/eventDemo/app/event/event/PlayerHavePassEvent.kt

@@ -10,8 +10,9 @@ import java.util.UUID
  */
 data class PlayerHavePassEvent(
     override val gameId: GameId,
-    val player: Player,
+    override val player: Player,
     val takenCard: Card,
-) : GameEvent {
+) : GameEvent,
+    PlayerActionEvent {
     override val eventId: UUID = UUID.randomUUID()
 }

src/main/kotlin/eventDemo/app/event/projection/GameState.kt

@@ -10,9 +10,9 @@ import kotlinx.serialization.Serializable
 data class GameState(
     val gameId: GameId,
     val players: Set<Player> = emptySet(),
-    val lastPlayer: Player? = null,
+    val currentPlayerTurn: Player? = null,
-    val lastCard: LastCard? = null,
+    val cardOnCurrentStack: LastCard? = null,
-    val lastColor: Card.Color? = null,
+    val colorOnCurrentStack: Card.Color? = null,
     val direction: Direction = Direction.CLOCKWISE,
     val readyPlayers: Set<Player> = emptySet(),
     val deck: Deck = Deck(players),
@@ -42,8 +42,8 @@ data class GameState(
         return players.size == readyPlayers.size && players.all { readyPlayers.contains(it) }
     }
 
-    private val lastPlayerIndex: Int? get() {
+    private val currentPlayerIndex: Int? get() {
-        val i = players.indexOf(lastPlayer)
+        val i = players.indexOf(currentPlayerTurn)
         return if (i == -1) {
             null
         } else {
@@ -51,28 +51,42 @@ data class GameState(
         }
     }
 
-    private val nextPlayerIndex: Int get() {
+    private fun nextPlayerIndex(direction: Direction): Int {
-        if (players.size == 0) return 0
+        if (players.isEmpty()) return 0
 
-        val y =
+        return if (direction == Direction.CLOCKWISE) {
-            if (direction == Direction.CLOCKWISE) {
+            sidePlayerIndexClockwise
-                +1
         } else {
-                -1
+            sidePlayerIndexCounterClockwise
+        }
     }
 
-        return ((lastPlayerIndex ?: 0) + y) % players.size
+    fun nextPlayer(direction: Direction): Player = players.elementAt(nextPlayerIndex(direction))
+
+    private val sidePlayerIndexClockwise: Int by lazy {
+        if (players.isEmpty()) {
+            0
+        } else {
+            ((currentPlayerIndex ?: 0) + 1) % players.size
+        }
+    }
+    private val sidePlayerIndexCounterClockwise: Int by lazy {
+        if (players.isEmpty()) {
+            0
+        } else {
+            ((currentPlayerIndex ?: 0) - 1) % players.size
+        }
     }
 
-    val nextPlayer: Player? by lazy {
+    val nextPlayerTurn: Player? by lazy {
         if (players.isEmpty()) {
             null
         } else {
-            players.elementAt(nextPlayerIndex)
+            nextPlayer(direction)
         }
     }
 
-    val Player.currentIndex: Int get() = players.indexOf(this)
+    private val Player.currentIndex: Int get() = players.indexOf(this)
 
     fun Player.playerDiffIndex(nextPlayer: Player): Int =
         if (direction == Direction.CLOCKWISE) {
@@ -82,8 +96,8 @@ data class GameState(
         }.let { it % players.size }
 
     val Player.cardOnBoardIsForYou: Boolean get() {
-        if (lastCard == null) error("No card")
+        if (cardOnCurrentStack == null) error("No card")
-        return this.playerDiffIndex(lastCard.player) == 1
+        return this.playerDiffIndex(cardOnCurrentStack.player) == 1
     }
 
     fun playableCards(player: Player): List<Card> =
@@ -102,7 +116,7 @@ data class GameState(
         player: Player,
         card: Card,
     ): Boolean {
-        val cardOnBoard = lastCard?.card ?: return false
+        val cardOnBoard = cardOnCurrentStack?.card ?: return false
         return when (cardOnBoard) {
             is Card.NumericCard -> {
                 when (card) {
@@ -134,7 +148,7 @@ data class GameState(
             is Card.ChangeColorCard -> {
                 when (card) {
                     is Card.AllColorCard -> true
-                    is Card.ColorCard -> card.color == lastColor
+                    is Card.ColorCard -> card.color == colorOnCurrentStack
                 }
             }
 
@@ -156,7 +170,7 @@ data class GameState(
                 } else {
                     when (card) {
                         is Card.AllColorCard -> true
-                        is Card.ColorCard -> card.color == lastColor
+                        is Card.ColorCard -> card.color == colorOnCurrentStack
                     }
                 }
             }

src/main/kotlin/eventDemo/app/event/projection/GameStateBuilder.kt

@@ -7,18 +7,22 @@ import eventDemo.app.event.event.CardIsPlayedEvent
 import eventDemo.app.event.event.GameEvent
 import eventDemo.app.event.event.GameStartedEvent
 import eventDemo.app.event.event.NewPlayerEvent
+import eventDemo.app.event.event.PlayerActionEvent
 import eventDemo.app.event.event.PlayerChoseColorEvent
 import eventDemo.app.event.event.PlayerHavePassEvent
 import eventDemo.app.event.event.PlayerReadyEvent
 import eventDemo.app.event.event.PlayerWinEvent
+import io.github.oshai.kotlinlogging.KotlinLogging
 
 fun GameId.buildStateFromEventStream(eventStream: GameEventStream): GameState {
     val events = eventStream.readAll(this)
     if (events.isEmpty()) return GameState(this)
-    return events.buildStateFromEvents()
+    return events.buildStateFromEvents().also {
+        KotlinLogging.logger {}.warn { "state is build from scratch for game: $this " }
+    }
 }
 
-fun List<GameEvent>.buildStateFromEvents(): GameState {
+fun Collection<GameEvent>.buildStateFromEvents(): GameState {
     val gameId = this.firstOrNull()?.gameId ?: error("Cannot build GameState from an empty list")
     return fold(GameState(gameId)) { state, event ->
         state.apply(event)
@@ -27,9 +31,14 @@ fun List<GameEvent>.buildStateFromEvents(): GameState {
 
 fun GameState.apply(event: GameEvent): GameState =
     let { state ->
+        if (event is PlayerActionEvent) {
+            if (state.currentPlayerTurn != event.player) {
+                error("inconsistent player turn. currentPlayerTurn: $currentPlayerTurn | player: ${event.player}")
+            }
+        }
         when (event) {
             is CardIsPlayedEvent -> {
-                val direction =
+                val nextDirectionAfterPlay =
                     when (event.card) {
                         is Card.ReverseCard -> state.direction.revert()
                         else -> state.direction
@@ -38,14 +47,21 @@ fun GameState.apply(event: GameEvent): GameState =
                 val color =
                     when (event.card) {
                         is Card.ColorCard -> event.card.color
-                        else -> state.lastColor
+                        is Card.AllColorCard -> null
+                    }
+
+                val currentPlayerAfterThePlay =
+                    if (event.card is Card.AllColorCard) {
+                        currentPlayerTurn
+                    } else {
+                        nextPlayer(nextDirectionAfterPlay)
                     }
 
                 state.copy(
-                    lastPlayer = event.player,
+                    currentPlayerTurn = currentPlayerAfterThePlay,
-                    direction = direction,
+                    direction = nextDirectionAfterPlay,
-                    lastColor = color,
+                    colorOnCurrentStack = color,
-                    lastCard = GameState.LastCard(event.card, event.player),
+                    cardOnCurrentStack = GameState.LastCard(event.card, event.player),
                     deck = state.deck.putOneCardFromHand(event.player, event.card),
                 )
             }
@@ -59,6 +75,7 @@ fun GameState.apply(event: GameEvent): GameState =
             }
 
             is PlayerReadyEvent -> {
+                if (state.isStarted) error("The game is already started")
                 state.copy(
                     readyPlayers = state.readyPlayers + event.player,
                 )
@@ -67,22 +84,23 @@ fun GameState.apply(event: GameEvent): GameState =
             is PlayerHavePassEvent -> {
                 if (event.takenCard != state.deck.stack.first()) error("taken card is not ot top of the stack")
                 state.copy(
-                    lastPlayer = event.player,
+                    currentPlayerTurn = nextPlayerTurn,
                     deck = state.deck.takeOneCardFromStackTo(event.player),
                 )
             }
 
             is PlayerChoseColorEvent -> {
                 state.copy(
-                    lastColor = event.color,
+                    currentPlayerTurn = nextPlayerTurn,
+                    colorOnCurrentStack = event.color,
                 )
             }
 
             is GameStartedEvent -> {
                 state.copy(
-                    lastColor = (event.deck.discard.first() as? Card.ColorCard)?.color ?: state.lastColor,
+                    colorOnCurrentStack = (event.deck.discard.first() as? Card.ColorCard)?.color ?: state.colorOnCurrentStack,
-                    lastCard = GameState.LastCard(event.deck.discard.first(), event.firstPlayer),
+                    cardOnCurrentStack = GameState.LastCard(event.deck.discard.first(), event.firstPlayer),
-                    lastPlayer = event.firstPlayer,
+                    currentPlayerTurn = event.firstPlayer,
                     deck = event.deck,
                     isStarted = true,
                 )

src/main/kotlin/eventDemo/app/event/projection/GameStateRepository.kt

@@ -22,8 +22,7 @@ class GameStateRepository(
             val projection = projections[event.gameId]
             if (projection == null) {
                 event
-                    .gameId
+                    .buildStateFromEventStreamTo(eventStream)
-                    .buildStateFromEventStream(eventStream)
                     .update()
             } else {
                 projection

src/main/kotlin/eventDemo/app/eventListener/GameEventPlayerNotificationListener.kt

@@ -1,5 +1,6 @@
 package eventDemo.app.eventListener
 
+import eventDemo.app.entity.Card
 import eventDemo.app.entity.Player
 import eventDemo.app.event.GameEventBus
 import eventDemo.app.event.event.CardIsPlayedEvent
@@ -11,6 +12,8 @@ import eventDemo.app.event.event.PlayerHavePassEvent
 import eventDemo.app.event.event.PlayerReadyEvent
 import eventDemo.app.event.event.PlayerWinEvent
 import eventDemo.app.event.projection.GameStateRepository
+import eventDemo.app.notification.ItsTheTurnOfNotification
+import eventDemo.app.notification.Notification
 import eventDemo.app.notification.PlayerAsJoinTheGameNotification
 import eventDemo.app.notification.PlayerAsPlayACardNotification
 import eventDemo.app.notification.PlayerHavePassNotification
@@ -33,22 +36,45 @@ class GameEventPlayerNotificationListener(
     private val logger = KotlinLogging.logger {}
 
     fun startListening(
-        outgoing: SendChannel<Frame>,
+        outgoingNotificationChannel: SendChannel<Frame>,
         currentPlayer: Player,
     ) {
         eventBus.subscribe { event: GameEvent ->
             val currentState = gameStateRepository.getUntil(event)
-            val notification =
+
+            fun Notification.send() {
+                if (currentState.players.contains(currentPlayer)) {
+                    // Only notify players who have already joined the game.
+                    outgoingNotificationChannel.trySendBlocking(toFrame())
+                    logger.atInfo {
+                        message = "Notification for player ${currentPlayer.name} was SEND: ${this@send}"
+                        payload = mapOf("notification" to this@send, "event" to event)
+                    }
+                } else {
+                    // Rare use case, when a connexion is created with the channel,
+                    // but the player was not already join in the game
+                    logger.atWarn {
+                        message = "Notification for player ${currentPlayer.name} was SKIP, No player on the game: ${this@send}"
+                        payload = mapOf("notification" to this@send, "event" to event)
+                    }
+                }
+            }
+
+            fun sendNextTurnNotif() =
+                ItsTheTurnOfNotification(
+                    player = currentState.currentPlayerTurn ?: error("No player turn defined"),
+                ).send()
+
             when (event) {
                 is NewPlayerEvent -> {
                     if (currentPlayer != event.player) {
                         PlayerAsJoinTheGameNotification(
                             player = event.player,
-                            )
+                        ).send()
                     } else {
                         WelcomeToTheGameNotification(
                             players = currentState.players,
-                            )
+                        ).send()
                     }
                 }
 
@@ -57,9 +83,13 @@ class GameEventPlayerNotificationListener(
                         PlayerAsPlayACardNotification(
                             player = event.player,
                             card = event.card,
-                            )
+                        ).send()
-                        } else {
+                    }
-                            null
+
+                    if (event.card !is Card.AllColorCard) {
+                        ItsTheTurnOfNotification(
+                            player = currentState.currentPlayerTurn ?: error("No player turn defined"),
+                        ).send()
                     }
                 }
 
@@ -68,7 +98,9 @@ class GameEventPlayerNotificationListener(
                         hand =
                             event.deck.playersHands.getHand(currentPlayer)
                                 ?: error("You are not in the game"),
-                        )
+                    ).send()
+
+                    sendNextTurnNotif()
                 }
 
                 is PlayerChoseColorEvent -> {
@@ -76,57 +108,38 @@ class GameEventPlayerNotificationListener(
                         PlayerWasChoseTheCardColorNotification(
                             player = event.player,
                             color = event.color,
-                            )
+                        ).send()
-                        } else {
-                            null
                     }
+
+                    sendNextTurnNotif()
                 }
 
                 is PlayerHavePassEvent -> {
                     if (currentPlayer == event.player) {
                         YourNewCardNotification(
                             card = event.takenCard,
-                            )
+                        ).send()
                     } else {
                         PlayerHavePassNotification(
                             player = event.player,
-                            )
+                        ).send()
                     }
+
+                    sendNextTurnNotif()
                 }
 
                 is PlayerReadyEvent -> {
                     if (currentPlayer != event.player) {
                         PlayerWasReadyNotification(
                             player = event.player,
-                            )
+                        ).send()
-                        } else {
-                            null
                     }
                 }
 
                 is PlayerWinEvent -> {
                     PlayerWinNotification(
                         player = event.player,
-                        )
+                    ).send()
-                    }
-                }
-
-            if (notification == null) {
-                logger.atInfo {
-                    message = "Notification Ignore: $event"
-                    payload = mapOf("event" to event)
-                }
-            } else if (currentState.players.contains(currentPlayer)) {
-                // Only notify players who have already joined the game.
-                outgoing.trySendBlocking(notification.toFrame())
-                logger.atInfo {
-                    message = "Notification SEND: $notification"
-                    payload = mapOf("notification" to notification, "event" to event)
-                }
-            } else {
-                logger.atInfo {
-                    message = "Notification SKIP: $notification"
-                    payload = mapOf("notification" to notification, "event" to event)
                 }
             }
         }

src/main/kotlin/eventDemo/app/eventListener/GameEventReactionListener.kt

@@ -4,6 +4,7 @@ import eventDemo.app.event.GameEventBus
 import eventDemo.app.event.GameEventHandler
 import eventDemo.app.event.event.GameEvent
 import eventDemo.app.event.event.GameStartedEvent
+import eventDemo.app.event.event.PlayerReadyEvent
 import eventDemo.app.event.event.PlayerWinEvent
 import eventDemo.app.event.projection.GameState
 import eventDemo.app.event.projection.GameStateRepository
@@ -29,7 +30,7 @@ class GameEventReactionListener(
         }
     }
 
-    private fun sendStartGameEvent(
+    private suspend fun sendStartGameEvent(
         state: GameState,
         event: GameEvent,
     ) {
@@ -40,7 +41,7 @@ class GameEventReactionListener(
                     state.players,
                 )
             logger.atInfo {
-                message = "Event Send on reaction of: $event"
+                message = "Reaction event was Send $reactionEvent on reaction of: $event"
                 payload =
                     mapOf(
                         "event" to event,
@@ -48,6 +49,10 @@ class GameEventReactionListener(
                     )
             }
             eventHandler.handle(reactionEvent)
+        } else {
+            if (event is PlayerReadyEvent) {
+                logger.info { "All players was not ready ${state.readyPlayers}" }
+            }
         }
     }
 
@@ -63,7 +68,7 @@ class GameEventReactionListener(
                     winner,
                 )
             logger.atInfo {
-                message = "Event Send on reaction of: $event"
+                message = "Reaction event was Send $reactionEvent on reaction of: $event"
                 payload =
                     mapOf(
                         "event" to event,

src/main/kotlin/eventDemo/app/notification/ItsTheTurnOfNotification.kt

@@ -0,0 +1,13 @@
+package eventDemo.app.notification
+
+import eventDemo.app.entity.Player
+import eventDemo.shared.UUIDSerializer
+import kotlinx.serialization.Serializable
+import java.util.UUID
+
+@Serializable
+data class ItsTheTurnOfNotification(
+    @Serializable(with = UUIDSerializer::class)
+    override val id: UUID = UUID.randomUUID(),
+    val player: Player,
+) : Notification

src/main/kotlin/eventDemo/app/query/ReadTheGameState.kt

@@ -40,7 +40,7 @@ fun Route.readTheGameState(gameStateRepository: GameStateRepository) {
         get<Game.Card> { body ->
             gameStateRepository
                 .get(body.game.id)
-                .lastCard
+                .cardOnCurrentStack
                 ?.card
                 ?.let { call.respond(it) }
                 ?: call.response.status(HttpStatusCode.BadRequest)

src/main/kotlin/eventDemo/libs/command/CommandStreamChannel.kt

@@ -49,7 +49,7 @@ class CommandStreamChannel<C : Command>(
         val actionResult = runCatching { status.action(command) }
         if (actionResult.isFailure) {
             logger.atInfo {
-                message = "Error on compute the Command"
+                message = "Error on compute the Command: $command"
                 payload = mapOf("command" to command)
                 cause = actionResult.exceptionOrNull()
             }

src/main/kotlin/eventDemo/libs/event/EventBus.kt

@@ -8,6 +8,6 @@ interface EventBus<E : Event<ID>, ID : AggregateId> {
      */
     fun subscribe(
         priority: Int = 0,
-        block: (E) -> Unit,
+        block: suspend (E) -> Unit,
     )
 }

src/main/kotlin/eventDemo/libs/event/EventBusInMemory.kt

@@ -1,19 +1,23 @@
 package eventDemo.libs.event
 
+import kotlinx.coroutines.runBlocking
+
 class EventBusInMemory<E : Event<ID>, ID : AggregateId> : EventBus<E, ID> {
-    private val subscribers: MutableList<Pair<Int, (E) -> Unit>> = mutableListOf()
+    private val subscribers: MutableList<Pair<Int, suspend (E) -> Unit>> = mutableListOf()
 
     override fun publish(event: E) {
         subscribers
-            .sortedByDescending { (priority, block) -> priority }
+            .sortedByDescending { (priority, _) -> priority }
             .forEach { (_, block) ->
+                runBlocking {
                     block(event)
                 }
             }
+    }
 
     override fun subscribe(
         priority: Int,
-        block: (E) -> Unit,
+        block: suspend (E) -> Unit,
     ) {
         subscribers.add(priority to block)
     }

src/main/kotlin/eventDemo/libs/event/EventStream.kt

@@ -22,5 +22,5 @@ interface EventStream<E : Event<ID>, ID : AggregateId> {
     ): R?
 
     /** Reads all events associated with a given aggregate ID */
-    fun readAll(aggregateId: ID): List<E>
+    fun readAll(aggregateId: ID): Set<E>
 }

src/main/kotlin/eventDemo/libs/event/EventStreamInMemory.kt

@@ -1,6 +1,8 @@
 package eventDemo.libs.event
 
 import io.github.oshai.kotlinlogging.KotlinLogging
+import java.util.Queue
+import java.util.concurrent.ConcurrentLinkedQueue
 import kotlin.reflect.KClass
 
 /**
@@ -10,7 +12,7 @@ import kotlin.reflect.KClass
  */
 class EventStreamInMemory<E : Event<ID>, ID : AggregateId> : EventStream<E, ID> {
     private val logger = KotlinLogging.logger {}
-    private val events: MutableList<E> = mutableListOf()
+    private val events: Queue<E> = ConcurrentLinkedQueue()
 
     override fun publish(event: E) {
         events.add(event)
@@ -34,7 +36,7 @@ class EventStreamInMemory<E : Event<ID>, ID : AggregateId> : EventStream<E, ID>
             .filterIsInstance(eventType.java)
             .lastOrNull { it.gameId == aggregateId }
 
-    override fun readAll(aggregateId: ID): List<E> = events
+    override fun readAll(aggregateId: ID): Set<E> = events.toSet()
 }
 
 inline fun <reified R : E, E : Event<ID>, ID : AggregateId> EventStream<E, ID>.readLastOf(aggregateId: ID): R? =

src/test/kotlin/eventDemo/app/event/projection/GameStateBuilderTest.kt

@@ -69,7 +69,7 @@ class GameStateBuilderTest :
                     val event = CardIsPlayedEvent(gameId, playedCard, player1)
                     apply(event).also { state ->
                         state.gameId shouldBeEqual gameId
-                        assertNotNull(state.lastCard).card shouldBeEqual playedCard
+                        assertNotNull(state.cardOnCurrentStack).card shouldBeEqual playedCard
                         assertIs<Card.NumericCard>(playedCard).let {
                             it.number shouldBeEqual 0
                             it.color shouldBeEqual Card.Color.Red
@@ -80,7 +80,7 @@ class GameStateBuilderTest :
                     val event = CardIsPlayedEvent(gameId, playedCard, player2)
                     apply(event).also { state ->
                         state.gameId shouldBeEqual gameId
-                        assertNotNull(state.lastCard).card shouldBeEqual playedCard
+                        assertNotNull(state.cardOnCurrentStack).card shouldBeEqual playedCard
                         assertIs<Card.NumericCard>(playedCard).let {
                             it.number shouldBeEqual 7
                             it.color shouldBeEqual Card.Color.Red

src/test/kotlin/eventDemo/app/query/GameStateTest.kt

@@ -4,6 +4,7 @@ import eventDemo.app.command.GameCommandHandler
 import eventDemo.app.command.command.IWantToJoinTheGameCommand
 import eventDemo.app.command.command.IWantToPlayCardCommand
 import eventDemo.app.command.command.IamReadyToPlayCommand
+import eventDemo.app.entity.Card
 import eventDemo.app.entity.GameId
 import eventDemo.app.entity.Player
 import eventDemo.app.event.GameEventStream
@@ -12,6 +13,7 @@ import eventDemo.app.event.projection.GameState
 import eventDemo.app.event.projection.buildStateFromEventStream
 import eventDemo.app.eventListener.GameEventPlayerNotificationListener
 import eventDemo.app.eventListener.GameEventReactionListener
+import eventDemo.app.notification.ItsTheTurnOfNotification
 import eventDemo.app.notification.PlayerAsJoinTheGameNotification
 import eventDemo.app.notification.PlayerAsPlayACardNotification
 import eventDemo.app.notification.PlayerWasReadyNotification
@@ -29,6 +31,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.delay
+import kotlinx.coroutines.joinAll
 import kotlinx.coroutines.launch
 import org.koin.dsl.koinApplication
 import kotlin.test.assertIs
@@ -43,75 +46,105 @@ class GameStateTest :
             val id = GameId()
             val player1 = Player(name = "Nikola")
             val player2 = Player(name = "Einstein")
-            val channelIn1 = Channel<Frame>()
+            val channelCommand1 = Channel<Frame>(Channel.BUFFERED)
-            val channelIn2 = Channel<Frame>()
+            val channelCommand2 = Channel<Frame>(Channel.BUFFERED)
-            val channelOut1 = Channel<Frame>(Channel.BUFFERED)
+            val channelNotification1 = Channel<Frame>(Channel.BUFFERED)
-            val channelOut2 = Channel<Frame>(Channel.BUFFERED)
+            val channelNotification2 = Channel<Frame>(Channel.BUFFERED)
+
+            var playedCard1: Card? = null
+            var playedCard2: Card? = null
+
+            val player1Job =
+                launch {
+                    channelCommand1.send(IWantToJoinTheGameCommand(IWantToJoinTheGameCommand.Payload(id, player1)).toFrame())
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<WelcomeToTheGameNotification>(it).players shouldBeEqual setOf(player1)
+                    }
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<PlayerAsJoinTheGameNotification>(it).player shouldBeEqual player2
+                    }
+                    channelCommand1.send(IamReadyToPlayCommand(IamReadyToPlayCommand.Payload(id, player1)).toFrame())
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<PlayerWasReadyNotification>(it).player shouldBeEqual player2
+                    }
+                    val player1Hand =
+                        channelNotification1.receive().toNotification().let {
+                            assertIs<TheGameWasStartedNotification>(it).hand shouldHaveSize 7
+                        }
+                    playedCard1 = player1Hand.first()
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<ItsTheTurnOfNotification>(it).apply {
+                            player shouldBeEqual player1
+                        }
+                    }
+                    channelCommand1.send(IWantToPlayCardCommand(IWantToPlayCardCommand.Payload(id, player1, player1Hand.first())).toFrame())
+
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<ItsTheTurnOfNotification>(it).apply {
+                            player shouldBeEqual player2
+                        }
+                    }
+
+                    channelNotification1.receive().toNotification().let {
+                        assertIs<PlayerAsPlayACardNotification>(it).apply {
+                            player shouldBeEqual player2
+                            card shouldBeEqual assertNotNull(playedCard2)
+                        }
+                    }
+                }
+
+            val player2Job =
+                launch {
+                    delay(100)
+                    channelCommand2.send(IWantToJoinTheGameCommand(IWantToJoinTheGameCommand.Payload(id, player2)).toFrame())
+                    channelNotification2.receive().toNotification().let {
+                        assertIs<WelcomeToTheGameNotification>(it).players shouldBeEqual setOf(player1, player2)
+                    }
+                    channelNotification2.receive().toNotification().let {
+                        assertIs<PlayerWasReadyNotification>(it).player shouldBeEqual player1
+                    }
+                    channelCommand2.send(IamReadyToPlayCommand(IamReadyToPlayCommand.Payload(id, player2)).toFrame())
+                    val player2Hand =
+                        channelNotification2.receive().toNotification().let {
+                            assertIs<TheGameWasStartedNotification>(it).hand shouldHaveSize 7
+                        }
+                    channelNotification2.receive().toNotification().let {
+                        assertIs<ItsTheTurnOfNotification>(it).apply {
+                            player shouldBeEqual player1
+                        }
+                    }
+                    channelNotification2.receive().toNotification().let {
+                        assertIs<PlayerAsPlayACardNotification>(it).apply {
+                            player shouldBeEqual player1
+                            card shouldBeEqual assertNotNull(playedCard1)
+                        }
+                    }
+                    playedCard2 = player2Hand.first()
+
+                    channelNotification2.receive().toNotification().let {
+                        assertIs<ItsTheTurnOfNotification>(it).apply {
+                            player shouldBeEqual player2
+                        }
+                    }
+                    channelCommand2.send(IWantToPlayCardCommand(IWantToPlayCardCommand.Payload(id, player2, player2Hand.first())).toFrame())
+                }
 
             koinApplication { modules(appKoinModule) }.koin.apply {
                 val commandHandler by inject<GameCommandHandler>()
-                val playerNotificationListener by inject<GameEventPlayerNotificationListener>()
                 val eventStream by inject<GameEventStream>()
+                val playerNotificationListener by inject<GameEventPlayerNotificationListener>()
                 GameEventReactionListener(get(), get(), get()).init()
-                playerNotificationListener.startListening(channelOut1, player1)
+                playerNotificationListener.startListening(channelNotification1, player1)
-                playerNotificationListener.startListening(channelOut2, player2)
+                playerNotificationListener.startListening(channelNotification2, player2)
 
                 GlobalScope.launch(Dispatchers.IO) {
-                    commandHandler.handle(player1, channelIn1, channelOut1)
+                    commandHandler.handle(player1, channelCommand1, channelNotification1)
                 }
                 GlobalScope.launch(Dispatchers.IO) {
-                    commandHandler.handle(player2, channelIn2, channelOut2)
+                    commandHandler.handle(player2, channelCommand2, channelNotification2)
                 }
 
-                channelIn1.send(IWantToJoinTheGameCommand(IWantToJoinTheGameCommand.Payload(id, player1)).toFrame())
+                joinAll(player1Job, player2Job)
-                delay(50)
-                channelIn2.send(IWantToJoinTheGameCommand(IWantToJoinTheGameCommand.Payload(id, player2)).toFrame())
-                delay(50)
-                channelOut1.receive().toNotification().let {
-                    assertIs<WelcomeToTheGameNotification>(it).players shouldBeEqual setOf(player1)
-                }
-
-                channelOut2.receive().toNotification().let {
-                    assertIs<WelcomeToTheGameNotification>(it).players shouldBeEqual setOf(player1, player2)
-                }
-                channelOut1.receive().toNotification().let {
-                    assertIs<PlayerAsJoinTheGameNotification>(it).player shouldBeEqual player2
-                }
-
-                channelIn1.send(IamReadyToPlayCommand(IamReadyToPlayCommand.Payload(id, player1)).toFrame())
-                delay(50)
-                channelIn2.send(IamReadyToPlayCommand(IamReadyToPlayCommand.Payload(id, player2)).toFrame())
-                delay(50)
-
-                channelOut1.receive().toNotification().let {
-                    assertIs<PlayerWasReadyNotification>(it).player shouldBeEqual player2
-                }
-                channelOut2.receive().toNotification().let {
-                    assertIs<PlayerWasReadyNotification>(it).player shouldBeEqual player1
-                }
-
-                val player1Hand =
-                    channelOut1.receive().toNotification().let {
-                        assertIs<TheGameWasStartedNotification>(it).hand shouldHaveSize 7
-                    }
-                val player2Hand =
-                    channelOut2.receive().toNotification().let {
-                        assertIs<TheGameWasStartedNotification>(it).hand shouldHaveSize 7
-                    }
-
-                channelIn1.send(IWantToPlayCardCommand(IWantToPlayCardCommand.Payload(id, player1, player1Hand.first())).toFrame())
-                delay(50)
-                channelOut2.receive().toNotification().let {
-                    assertIs<PlayerAsPlayACardNotification>(it).player shouldBeEqual player1
-                    assertIs<PlayerAsPlayACardNotification>(it).card shouldBeEqual player1Hand.first()
-                }
-
-                channelIn2.send(IWantToPlayCardCommand(IWantToPlayCardCommand.Payload(id, player2, player2Hand.first())).toFrame())
-                delay(50)
-                channelOut1.receive().toNotification().let {
-                    assertIs<PlayerAsPlayACardNotification>(it).player shouldBeEqual player2
-                    assertIs<PlayerAsPlayACardNotification>(it).card shouldBeEqual player2Hand.first()
-                }
 
                 val state = id.buildStateFromEventStream(eventStream)
 
@@ -120,7 +153,7 @@ class GameStateTest :
                 state.players shouldBeEqual setOf(player1, player2)
                 state.readyPlayers shouldBeEqual setOf(player1, player2)
                 state.direction shouldBeEqual GameState.Direction.CLOCKWISE
-                assertNotNull(state.lastCard) shouldBeEqual GameState.LastCard(player2Hand.first(), player2)
+                assertNotNull(state.cardOnCurrentStack) shouldBeEqual GameState.LastCard(assertNotNull(playedCard2), player2)
             }
         }
     })