Simple event bus in native Java

plugin/src/software/aws/toolkits/eclipse/amazonq/broker/EventBroker.java

@@ -0,0 +1,82 @@
+// Copyright 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.eclipse.amazonq.broker;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Flow.Subscription;
+import java.util.concurrent.SubmissionPublisher;
+import java.util.concurrent.atomic.AtomicReference;
+
+import software.aws.toolkits.eclipse.amazonq.subscriber.Subscriber;
+
+public final class EventBroker {
+
+    private static final EventBroker INSTANCE;
+    private final Map<Class<?>, SubmissionPublisher<?>> publishers;
+
+    static {
+        INSTANCE = new EventBroker();
+    }
+
+    private EventBroker() {
+        publishers = new ConcurrentHashMap<>();
+    }
+
+    public static EventBroker getInstance() {
+        return INSTANCE;
+    }
+
+    public <T> void post(final T event) {
+        if (event == null) {
+            return;
+        }
+
+        @SuppressWarnings("unchecked")
+        SubmissionPublisher<T> publisher = (SubmissionPublisher<T>) getPublisher(event.getClass());
+        publisher.submit(event);
+    }
+
+    public <T> Subscription subscribe(final Subscriber<T> subscriber) {
+        SubmissionPublisher<T> publisher = getPublisher(subscriber.getSubscriptionEventClass());
+        AtomicReference<Subscription> subscriptionReference = new AtomicReference<>();
+
+        java.util.concurrent.Flow.Subscriber<T> subscriberWrapper = new java.util.concurrent.Flow.Subscriber<>() {
+            private java.util.concurrent.Flow.Subscription subscription;
+
+            @Override
+            public void onSubscribe(final java.util.concurrent.Flow.Subscription subscription) {
+                this.subscription = subscription;
+                subscriptionReference.set(subscription);
+                this.subscription.request(1);
+            }
+
+            @Override
+            public void onNext(final T event) {
+                subscriber.handleEvent(event);
+                this.subscription.request(1);
+            }
+
+            @Override
+            public void onError(final Throwable throwable) {
+                subscriber.handleError(throwable);
+            }
+
+            @Override
+            public void onComplete() {
+                // TODO: add if required
+            }
+        };
+
+        publisher.subscribe(subscriberWrapper);
+        return subscriptionReference.get();
+    }
+
+    @SuppressWarnings("unchecked")
+    private <T> SubmissionPublisher<T> getPublisher(final Class<T> eventType) {
+        return (SubmissionPublisher<T>) publishers.computeIfAbsent(eventType,
+                key -> new SubmissionPublisher<>());
+    }
+
+}

plugin/src/software/aws/toolkits/eclipse/amazonq/events/TestEvent.java

@@ -0,0 +1,17 @@
+// Copyright 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.eclipse.amazonq.events;
+
+public final class TestEvent {
+    private final String message;
+
+    public TestEvent(final String message) {
+        this.message = message;
+    }
+
+    public String getMessage() {
+        return message;
+    }
+
+}

plugin/src/software/aws/toolkits/eclipse/amazonq/publishers/TestPublisher.java

@@ -0,0 +1,28 @@
+// Copyright 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.eclipse.amazonq.publishers;
+
+import software.aws.toolkits.eclipse.amazonq.broker.EventBroker;
+import software.aws.toolkits.eclipse.amazonq.events.TestEvent;
+
+public final class TestPublisher {
+
+    public TestPublisher() {
+        Thread publisherThread = new Thread(() -> {
+            try {
+                Thread.sleep(5000);
+                EventBroker eventBroker = EventBroker.getInstance();
+
+                for (int i = 0; i < 10; i++) {
+                    eventBroker.post(new TestEvent("Test Event " + i));
+                }
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }, "TestPublisher-Thread");
+
+        publisherThread.start();
+    }
+
+}

plugin/src/software/aws/toolkits/eclipse/amazonq/subscriber/Subscriber.java

@@ -0,0 +1,13 @@
+// Copyright 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package software.aws.toolkits.eclipse.amazonq.subscriber;
+
+public interface Subscriber<T> {
+
+    Class<T> getSubscriptionEventClass();
+
+    void handleEvent(T event);
+    void handleError(Throwable error);
+
+}

plugin/src/software/aws/toolkits/eclipse/amazonq/views/AmazonQView.java

@@ -9,22 +9,28 @@
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.ui.part.ViewPart;
 
+import software.aws.toolkits.eclipse.amazonq.broker.EventBroker;
 import software.aws.toolkits.eclipse.amazonq.controllers.AmazonQViewController;
+import software.aws.toolkits.eclipse.amazonq.events.TestEvent;
 import software.aws.toolkits.eclipse.amazonq.lsp.auth.AuthStatusChangedListener;
 import software.aws.toolkits.eclipse.amazonq.lsp.auth.AuthStatusProvider;
 import software.aws.toolkits.eclipse.amazonq.lsp.auth.model.AuthState;
 import software.aws.toolkits.eclipse.amazonq.plugin.Activator;
+import software.aws.toolkits.eclipse.amazonq.publishers.TestPublisher;
+import software.aws.toolkits.eclipse.amazonq.subscriber.Subscriber;
 import software.aws.toolkits.eclipse.amazonq.util.ThemeDetector;
 import software.aws.toolkits.eclipse.amazonq.views.actions.AmazonQCommonActions;
 
-public abstract class AmazonQView extends ViewPart implements AuthStatusChangedListener {
+public abstract class AmazonQView extends ViewPart implements AuthStatusChangedListener, Subscriber<TestEvent> {
 
     private AmazonQViewController viewController;
     private AmazonQCommonActions amazonQCommonActions;
     private static final ThemeDetector THEME_DETECTOR = new ThemeDetector();
 
     protected AmazonQView() {
         this.viewController = new AmazonQViewController();
+        new TestPublisher();
+        EventBroker.getInstance().subscribe(this);
     }
 
     public final Browser getBrowser() {
@@ -127,4 +133,19 @@ public void dispose() {
         super.dispose();
     }
 
+    @Override
+    public final Class<TestEvent> getSubscriptionEventClass() {
+        return TestEvent.class;
+    }
+
+    @Override
+    public final void handleEvent(final TestEvent event) {
+        Activator.getLogger().info(event.getMessage());
+    }
+
+    @Override
+    public final void handleError(final Throwable error) {
+        error.printStackTrace();
+    }
+
 }