<?php
namespace Acme\TestBundle\EventListener;

use eZ\Publish\Core\MVC\Symfony\Event\SignalEvent;
use eZ\Publish\Core\MVC\Symfony\MVCEvents;
use Psr\Log\LoggerInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class SignalListener implements EventSubscriberInterface
{
    /**
     * @var \Psr\Log\LoggerInterface
     */
    private $logger;

    public function __construct( LoggerInterface $logger )
    {
        $this->logger = $logger;
    }

    public function onAPISignal( SignalEvent $event )
    {
        $signal = $event->getSignal();
        // You may want to check the signal type here to react accordingly
        $this->logger->debug( 'Received Signal: ' . print_r( $signal, true ) );
    }

    public static function getSubscribedEvents()
    {
        return array(
            MVCEvents::API_SIGNAL => 'onAPISignal'
        );
    }
}