fix: Making the event queue overridable (#473)

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Fixes #<issue_number_goes_here> 🦕

Signed-off-by: Emmanuel Hugonnet <[email protected]>

Author: ehsavoie

client/base/src/main/java/io/a2a/client/MessageEvent.java

@@ -21,6 +21,19 @@ public MessageEvent(Message message) {
     public Message getMessage() {
         return message;
     }
-}
-
 
+    @Override
+    public String toString() {
+        String messageAsString = "{"
+                + "role=" + message.getRole()
+                + ", parts=" + message.getParts()
+                + ", messageId=" + message.getMessageId()
+                + ", contextId=" + message.getContextId()
+                + ", taskId=" + message.getTaskId()
+                + ", metadata=" + message.getMetadata()
+                + ", kind=" + message.getKind()
+                + ", referenceTaskIds=" + message.getReferenceTaskIds()
+                + ", extensions=" + message.getExtensions() + '}';
+        return "MessageEvent{" + "message=" + messageAsString + '}';
+    }
+}

server-common/src/main/java/io/a2a/server/events/EventQueue.java

@@ -96,7 +96,7 @@ public int getQueueSize() {
 
     public abstract void awaitQueuePollerStart() throws InterruptedException ;
 
-    abstract void signalQueuePollerStarted();
+    public abstract void signalQueuePollerStarted();
 
     public void enqueueEvent(Event event) {
         enqueueItem(new LocalEventQueueItem(event));
@@ -119,7 +119,7 @@ public void enqueueItem(EventQueueItem item) {
         LOGGER.debug("Enqueued event {} {}", event instanceof Throwable ? event.toString() : event, this);
     }
 
-    abstract EventQueue tap();
+    public abstract EventQueue tap();
 
     /**
      * Dequeues an EventQueueItem from the queue.
@@ -265,7 +265,7 @@ static class MainQueue extends EventQueue {
                     taskId, onCloseCallbacks.size(), taskStateProvider != null);
         }
 
-        EventQueue tap() {
+        public EventQueue tap() {
             ChildQueue child = new ChildQueue(this);
             children.add(child);
             return child;
@@ -310,7 +310,7 @@ public void awaitQueuePollerStart() throws InterruptedException {
         }
 
         @Override
-        void signalQueuePollerStarted() {
+        public void signalQueuePollerStarted() {
             if (pollingStarted.get()) {
                 return;
             }
@@ -415,7 +415,7 @@ private void internalEnqueueItem(EventQueueItem item) {
         }
 
         @Override
-        EventQueue tap() {
+        public EventQueue tap() {
             throw new IllegalStateException("Can only tap the main queue");
         }
 
@@ -425,7 +425,7 @@ public void awaitQueuePollerStart() throws InterruptedException {
         }
 
         @Override
-        void signalQueuePollerStarted() {
+        public void signalQueuePollerStarted() {
             parent.signalQueuePollerStarted();
         }