Extract the use case business logic to its own Application Service class and execute it from the main entry point

* Create the `AggregateRoot` abstract class in order to deal with recorded domain events being able to pull them out afterwards
* Refactor the `EventBus#publish` contract in order to receive a `List` of `DomainEvent`s instead of a single one. I've tried with the varargs approach in order to be able to publish one single event or a list of them, but it wouldn't match the actual contract of the `AggregateRoot#pullDomainEvents(): List<DomainEvent>` return type. So taking into account we would have to convert it to an `Array` (cost O(n)) just because of that, I think it make sense to just use `List` on the `EventBus` side and simplify the signatures at least for now 🤟

Author: JavierCane

src/main/java/tv/codely/Starter.java

@@ -1,7 +1,7 @@
 package tv.codely;
 
 import tv.codely.context.notification.module.push.application.create.SendPushToSubscribersOnVideoPublished;
-import tv.codely.context.video.module.video.domain.VideoPublished;
+import tv.codely.context.video.module.video.application.create.VideoPublisher;
 import tv.codely.shared.application.DomainEventSubscriber;
 import tv.codely.shared.domain.EventBus;
 import tv.codely.shared.infrastructure.bus.ReactorEventBus;
@@ -13,14 +13,12 @@ public static void main(String[] args) {
         final Set<DomainEventSubscriber> subscribers = Set.of(
             new SendPushToSubscribersOnVideoPublished()
         );
-
         final EventBus eventBus = new ReactorEventBus(subscribers);
+        final var videoPublisher = new VideoPublisher(eventBus);
 
-        final var videoPublished = new VideoPublished(
-            "\uD83C\uDF89 New youtube.com/CodelyTV video title",
-            "This should be the video description \uD83D\uDE42"
-        );
+        final var videoTitle = "\uD83C\uDF89 New YouTube.com/CodelyTV video title";
+        final var videoDescription = "This should be the video description \uD83D\uDE42";
 
-        eventBus.publish(videoPublished);
+        videoPublisher.publish(videoTitle, videoDescription);
     }
 }

src/main/java/tv/codely/context/video/module/video/application/create/VideoCreator.java

@@ -0,0 +1,19 @@
+package tv.codely.context.video.module.video.application.create;
+
+import tv.codely.context.video.module.video.domain.Video;
+import tv.codely.shared.domain.EventBus;
+
+public final class VideoPublisher {
+    private final EventBus eventBus;
+
+    public VideoPublisher(EventBus eventBus) {
+        this.eventBus = eventBus;
+    }
+
+    public void publish(String title, String description) {
+        final var video = Video.publish(title, description);
+
+        eventBus.publish(video.pullDomainEvents());
+    }
+
+}

src/main/java/tv/codely/context/video/module/video/application/create/VideoPublisher.java

@@ -0,0 +1,23 @@
+package tv.codely.context.video.module.video.domain;
+
+import tv.codely.shared.domain.AggregateRoot;
+
+public final class Video extends AggregateRoot {
+    private final String title;
+    private final String description;
+
+    private Video(String title, String description) {
+        this.title = title;
+        this.description = description;
+    }
+
+    public static Video publish(String title, String description) {
+        var video = new Video(title, description);
+
+        var videoCreated = new VideoPublished(title, description);
+
+        video.record(videoCreated);
+
+        return video;
+    }
+}

src/main/java/tv/codely/context/video/module/video/domain/Video.java

@@ -0,0 +1,19 @@
+package tv.codely.shared.domain;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public abstract class AggregateRoot {
+    private List<DomainEvent> recordedDomainEvents = new LinkedList<>();
+
+    final public List<DomainEvent> pullDomainEvents() {
+        final var recordedDomainEvents = this.recordedDomainEvents;
+        this.recordedDomainEvents = new LinkedList<>();
+
+        return recordedDomainEvents;
+    }
+
+    final protected void record(DomainEvent event) {
+        recordedDomainEvents.add(event);
+    }
+}

src/main/java/tv/codely/shared/domain/AggregateRoot.java

@@ -1,5 +1,7 @@
 package tv.codely.shared.domain;
 
+import java.util.List;
+
 public interface EventBus {
-    void publish(DomainEvent event);
+    void publish(final List<DomainEvent> events);
 }

src/main/java/tv/codely/shared/domain/EventBus.java

@@ -7,6 +7,8 @@
 import tv.codely.shared.application.DomainEventSubscriber;
 import tv.codely.shared.domain.DomainEvent;
 
+import java.util.Arrays;
+import java.util.List;
 import java.util.Set;
 
 import static reactor.bus.selector.Selectors.$;
@@ -21,7 +23,11 @@ public ReactorEventBus(final Set<DomainEventSubscriber> subscribers) {
     }
 
     @Override
-    public void publish(final DomainEvent event) {
+    public void publish(final List<DomainEvent> events) {
+        events.forEach(this::publish);
+    }
+
+    private void publish(final DomainEvent event) {
         Class<? extends DomainEvent> eventIdentifier = event.getClass();
         Event<DomainEvent> wrappedEvent = Event.wrap(event);