refactor: move EventHandler to libs

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

@@ -0,0 +1,46 @@
+package eventDemo.libs.event
+
+import eventDemo.libs.bus.Bus
+import io.github.oshai.kotlinlogging.withLoggingContext
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.locks.ReentrantLock
+import kotlin.concurrent.withLock
+
+/**
+ * Handle the event to dispatch it to store, bus and projections builders
+ */
+class EventHandlerImpl<E : Event<ID>, ID : AggregateId>(
+  private val eventBus: Bus<E>,
+  private val eventStore: EventStore<E, ID>,
+  private val versionBuilder: VersionBuilder,
+) : EventHandler<E, ID> {
+  private val locks: ConcurrentHashMap<ID, ReentrantLock> = ConcurrentHashMap()
+
+  /**
+   * Build Event then send it to the event store and bus.
+   */
+  override suspend fun handle(
+    aggregateId: ID,
+    buildEvent: (version: Int) -> E,
+  ): E =
+    withLoggingContext("aggregateId" to aggregateId.toString()) {
+      locks
+        // Get lock for the aggregate
+        .computeIfAbsent(aggregateId) { ReentrantLock() }
+        .withLock {
+          // Build event with the version
+          buildEvent(versionBuilder.buildNextVersion(aggregateId))
+            // then publish it to the event store
+            .also {
+              withLoggingContext("event" to it.toString()) {
+                eventStore.publish(it)
+              }
+            }
+        }.also { event ->
+          withLoggingContext("event" to event.toString()) {
+            // Publish to the bus
+            eventBus.publish(event)
+          }
+        }
+    }
+}