create bus and subscriber

src/main/kotlin/eventDemo/shared/event/GameStateBuilder.kt

@@ -0,0 +1,71 @@
+package eventDemo.shared.event
+
+import eventDemo.libs.event.EventStream
+import eventDemo.shared.GameId
+import eventDemo.shared.entity.Card
+
+fun GameId.buildStateFromEventStream(eventStream: EventStream<GameEvent, GameId>): GameState =
+    buildStateFromEvents(
+        eventStream.readAll(this),
+    )
+
+private fun GameId.buildStateFromEvents(events: List<GameEvent>): GameState =
+    events.fold(GameState(this)) { state: GameState, event: GameEvent ->
+        when (event) {
+            is CardIsPlayedEvent -> {
+                val direction =
+                    when (event.card) {
+                        is Card.ReverseCard -> state.direction.revert()
+                        else -> state.direction
+                    }
+
+                val color =
+                    when (event.card) {
+                        is Card.ColorCard -> event.card.color
+                        else -> state.lastColor
+                    }
+
+                state.copy(
+                    lastPlayer = event.player,
+                    direction = direction,
+                    lastColor = color,
+                )
+            }
+
+            is NewPlayerEvent -> {
+                if (state.isReady) error("The game is already started")
+
+                state.copy(
+                    players = state.players + event.player,
+                )
+            }
+
+            is PlayerReadyEvent -> {
+                state.copy(
+                    readyPlayers = state.readyPlayers + event.player,
+                )
+            }
+
+            is PlayerHavePassEvent -> {
+                state.copy(
+                    lastPlayer = event.player,
+                )
+            }
+
+            is PlayerChoseColorEvent -> {
+                state.copy(
+                    lastColor = event.color,
+                )
+            }
+
+            is GameStartedEvent -> {
+                state.copy(
+                    lastColor = (event.deck.discard.first() as? Card.ColorCard)?.color,
+                    lastCard = GameState.LastCard(event.deck.discard.first(), event.firstPlayer),
+                    lastPlayer = event.firstPlayer,
+                    deck = event.deck,
+                    isStarted = true,
+                )
+            }
+        }
+    }