add quick tour for async event dispatcher.

Author: makasim

docs/async_event_dispatcher/quick_tour.md

@@ -0,0 +1,112 @@
+# Async event dispatcher (Symfony)
+
+The doc shows how you can setup async event dispatching in plain PHP. 
+If you are looking for the ways to use it in Symfony application [read this post instead](../bundle/async_events.md)
+ 
+* [Installation](#installation)
+* [Configuration](#configuration)
+* [Dispatch event](#dispatch-event)
+* [Process async events](#process-async-events)
+
+## Installation
+
+You need the async dispatcher library and a one of [the supported transports](../transport)
+
+```bash
+$ composer require enqueue/async-event-dispatcher enqueue/fs
+```
+
+## Configuration
+
+```php
+<?php
+
+// config.php
+
+use Enqueue\AsyncEventDispatcher\AsyncListener;
+use Enqueue\AsyncEventDispatcher\AsyncProcessor;
+use Enqueue\AsyncEventDispatcher\PhpSerializerEventTransformer;
+use Enqueue\AsyncEventDispatcher\AsyncEventDispatcher;
+use Enqueue\AsyncEventDispatcher\SimpleRegistry;
+use Enqueue\Fs\FsConnectionFactory;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+require_once __DIR__.'/vendor/autoload.php';
+
+// it could be any other enqueue/psr-queue compatible context.
+$context = (new FsConnectionFactory('file://'.__DIR__.'/queues'))->createContext();
+$eventQueue = $context->createQueue('symfony_events');
+
+$registry = new SimpleRegistry(
+    ['the_event' => 'default'], 
+    ['default' => new PhpSerializerEventTransformer($context, true)]
+);
+
+$asyncListener = new AsyncListener($context, $registry, $eventQueue);
+
+$dispatcher = new EventDispatcher();
+
+// the listener sends even as a message through MQ
+$dispatcher->addListener('the_event', $asyncListener);
+
+$asyncDispatcher = new AsyncEventDispatcher($dispatcher, $asyncListener);
+
+// the listener is executed on consumer side.
+$asyncDispatcher->addListener('the_event', function() {
+});
+
+$asyncProcessor = new AsyncProcessor($registry, $asyncDispatcher);
+```
+
+## Dispatch event
+
+```php
+<?php
+
+// send.php
+
+use Symfony\Component\EventDispatcher\GenericEvent;
+
+require_once __DIR__.'/vendor/autoload.php';
+
+include __DIR__.'/config.php';
+
+$dispatcher->dispatch('the_event', new GenericEvent('theSubject'));
+```
+
+## Process async events
+
+```php
+<?php
+
+// consume.php
+
+use Enqueue\Psr\PsrProcessor;
+
+require_once __DIR__.'/vendor/autoload.php';
+include __DIR__.'/config.php';
+
+$consumer = $context->createConsumer($eventQueue);
+
+while (true) {
+    if ($message = $consumer->receive(5000)) {
+        $result = $asyncProcessor->process($message, $context);
+
+        switch ((string) $result) {
+            case PsrProcessor::ACK:
+                $consumer->acknowledge($message);
+                break;
+            case PsrProcessor::REJECT:
+                $consumer->reject($message);
+                break;
+            case PsrProcessor::REQUEUE:
+                $consumer->reject($message, true);
+                break;
+            default:
+                throw new \LogicException('Result is not supported');
+        }
+    }
+}
+```
+
+[back to index](../index.md)

docs/index.md

@@ -34,6 +34,8 @@
     - [Production settings](bundle/production_settings.md)
     - [Debuging](bundle/debuging.md)
     - [Functional testing](bundle/functional_testing.md)
+* Async event dispatcher  (Symfony)
+    - [Quick tour](async_event_dispatcher/quick_tour.md)
 * Magento
     - [Quick tour](magento/quick_tour.md)
     - [Cli commands](magento/cli_commands.md) 

pkg/async-event-dispatcher/AsyncListener.php

@@ -40,6 +40,11 @@ public function __construct(PsrContext $context, Registry $registry, $eventQueue
         $this->eventQueue = $eventQueue instanceof PsrQueue ? $eventQueue : $context->createQueue($eventQueue);
     }
 
+    public function __invoke(Event $event, $eventName)
+    {
+        $this->onEvent($event, $eventName);
+    }
+
     public function resetSyncMode()
     {
         $this->syncMode = [];
@@ -67,7 +72,7 @@ public function isSyncMode($eventName)
      * @param Event  $event
      * @param string $eventName
      */
-    public function onEvent(Event $event = null, $eventName)
+    public function onEvent(Event $event, $eventName)
     {
         if (false == isset($this->syncMode[$eventName])) {
             $transformerName = $this->registry->getTransformerNameForEvent($eventName);