Merge pull request #7 from Nyholm/predefined

Added a middleware to only publish predefined messages

doc/publishing_messages.md

@@ -5,9 +5,12 @@ currentMenu: publishing_messages
 # Publishing messages
 
 When a `Message` should not be handled by the message bus (i.e. command or event bus) immediately (i.e. synchronously),
-it can be *published* to be handled by some other process. This library comes with two strategies for publishing
-messages: either a message will always *also* be published, or it will only be published when the message bus isn't able
-to handle it because there is no handler defined for it.
+it can be *published* to be handled by some other process. This library comes with three strategies for publishing
+messages:
+
+1. A message will always *also* be published.
+2. A message will only be published when the message bus isn't able to handle it because there is no handler defined for it.
+3. A message will be published only if its name exists in a predefined list.
 
 ## Strategy 1: Always publish messages
 
@@ -78,4 +81,35 @@ Possibly some other process knows how to handle it.
 
 If no command handler was found and the command is published, this will be logged using the provided `$logger`.
 
+## Strategy 3: Only publish predefined messages
+
+This strategy is useful when you know what messages you want to publish. 
+
+```php
+use SimpleBus\Message\Bus\Middleware\MessageBusSupportingMiddleware;
+use SimpleBus\Asynchronous\MessageBus\AlwaysPublishesMessages;
+use SimpleBus\Asynchronous\Publisher\Publisher;
+use SimpleBus\Message\Message;
+use SimpleBus\Message\Name\MessageNameResolver;
+
+// $eventBus is an instance of MessageBusSupportingMiddleware
+$eventBus = ...;
+
+// $publisher is an instance of Publisher
+$publisher = ...;
+
+// $messageNameResolver is an instance of MessageNameResolver
+$messageNameResolver = ...;
+
+// The list of names will depend on what MessageNameResolver you are using. 
+$names = ['My\\Event', 'My\\Other\\Event'];
+
+$eventBus->appendMiddleware(new PublishesPredefinedMessages($publisher, $messageNameResolver, $names));
+
+// $event is an object
+$event = ...;
+
+$eventBus->handle($event);
+```
+
 *Continue reading about [consuming messages](consuming_messages.md)*

src/MessageBus/PublishesPredefinedMessages.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace SimpleBus\Asynchronous\MessageBus;
+
+use SimpleBus\Asynchronous\Publisher\Publisher;
+use SimpleBus\Message\Bus\Middleware\MessageBusMiddleware;
+use SimpleBus\Message\Name\MessageNameResolver;
+
+class PublishesPredefinedMessages implements MessageBusMiddleware
+{
+    /**
+     * @var \SimpleBus\Asynchronous\Publisher\Publisher
+     */
+    private $publisher;
+
+    /**
+     * @var MessageNameResolver
+     */
+    private $messageNameResolver;
+
+    /**
+     * @var array names
+     */
+    private $names;
+
+    /**
+     * @param Publisher $publisher
+     * @param MessageNameResolver $messageNameResolver
+     * @param array $names an array with names on messages to be published.
+     */
+    public function __construct(Publisher $publisher, MessageNameResolver $messageNameResolver, array $names)
+    {
+        $this->publisher = $publisher;
+        $this->messageNameResolver = $messageNameResolver;
+        $this->names = $names;
+    }
+
+    /**
+     * Handle a message by publishing it to a queue (always), then calling the next middleware
+     *
+     * {@inheritdoc}
+     */
+    public function handle($message, callable $next)
+    {
+        $name = $this->messageNameResolver->resolve($message);
+        if (in_array($name, $this->names)) {
+            $this->publisher->publish($message);
+        }
+
+        $next($message);
+    }
+}

tests/MessageBus/PublishesPredefinedMessagesTest.php

@@ -0,0 +1,93 @@
+<?php
+
+namespace SimpleBus\Asynchronous\Tests\MessageBus;
+
+use SimpleBus\Asynchronous\MessageBus\PublishesPredefinedMessages;
+use SimpleBus\Asynchronous\Publisher\Publisher;
+use SimpleBus\Message\CallableResolver\Exception\UndefinedCallable;
+use SimpleBus\Message\Name\MessageNameResolver;
+
+class PublishesPredefinedMessagesTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @test
+     */
+    public function it_calls_the_next_middleware_and_when_the_message_is_handled_it_does_not_publish_it()
+    {
+        $message = $this->dummyMessage();
+
+        $nextCallableCalled = false;
+        $alwaysSucceedingNextCallable = function ($actualMessage) use ($message, &$nextCallableCalled) {
+            $nextCallableCalled = true;
+            $this->assertSame($message, $actualMessage);
+        };
+
+        $publisher = $this->mockPublisher();
+        $publisher
+            ->expects($this->never())
+            ->method('publish');
+
+        $nameResolver = $this->mockNameResolver();
+        $nameResolver->method('resolve')
+            ->willReturn('foo');
+
+        $middleware = new PublishesPredefinedMessages($publisher, $nameResolver, ['baz', 'bar']);
+
+        $middleware->handle($message, $alwaysSucceedingNextCallable);
+
+        $this->assertTrue($nextCallableCalled);
+    }
+
+    /**
+     * @test
+     */
+    public function it_calls_the_next_middleware_and_when_the_message_has_no_handler_it_publishes_it()
+    {
+        $message = $this->dummyMessage();
+
+        $nextCallableCalled = false;
+        $alwaysSucceedingNextCallable = function ($actualMessage) use ($message, &$nextCallableCalled) {
+            $nextCallableCalled = true;
+            $this->assertSame($message, $actualMessage);
+        };
+
+        $publisher = $this->mockPublisher();
+        $publisher
+            ->expects($this->once())
+            ->method('publish')
+            ->with($this->identicalTo($message));
+
+        $nameResolver = $this->mockNameResolver();
+        $nameResolver->method('resolve')
+            ->willReturn('foo');
+
+        $middleware = new PublishesPredefinedMessages($publisher, $nameResolver, ['baz', 'foo', 'bar']);
+
+        $middleware->handle($message, $alwaysSucceedingNextCallable);
+
+        $this->assertTrue($nextCallableCalled);
+    }
+
+    /**
+     * @return \PHPUnit_Framework_MockObject_MockObject|Publisher
+     */
+    private function mockPublisher()
+    {
+        return $this->getMock('SimpleBus\Asynchronous\Publisher\Publisher');
+    }
+    /**
+     * @return \PHPUnit_Framework_MockObject_MockObject|MessageNameResolver
+     */
+    private function mockNameResolver()
+    {
+        return $this->getMock('SimpleBus\Message\Name\MessageNameResolver');
+    }
+
+    /**
+     * @return \PHPUnit_Framework_MockObject_MockObject|object
+     */
+    private function dummyMessage()
+    {
+        return new \stdClass();
+    }
+}