EventProcessor.php

<?php
/**
 * Webiny Framework (http://www.webiny.com/framework)
 *
 * @copyright Copyright Webiny LTD
 */

namespace Webiny\Component\EventManager;

use Webiny\Component\StdLib\SingletonTrait;
use Webiny\Component\StdLib\StdLibTrait;

/**
 * EventProcessor is a class that takes EventListeners and Event object and processes the event.
 * @package         Webiny\Component\EventManager
 */
class EventProcessor
{
    use StdLibTrait, SingletonTrait;

    /**
     * Process given event
     *
     * @param array|ArrayObject $eventListeners EventListeners that are subscribed to this event
     * @param Event             $event          Event data object
     *
     * @param null|string       $resultType     Type of event result to enforce (can be any class or interface name)
     *
     * @return array
     */
    public function process($eventListeners, Event $event, $resultType = null)
    {

        $eventListeners = $this->_orderByPriority($eventListeners);

        $results = [];

        /* @var $eventListener EventListener */
        foreach ($eventListeners as $eventListener) {

            $handler = $eventListener->getHandler();
            if ($this->isNull($handler)) {
                continue;
            }

            $method = $eventListener->getMethod();

            if ($this->isCallable($handler)) {
                /** @var $handler \Closure */
                $result = $handler($event);
            } else {
                $result = call_user_func_array([
                                                   $handler,
                                                   $method
                                               ], [$event]
                );
            }

            if ($this->isNull($resultType) || (!$this->isNull($resultType) && $this->isInstanceOf($result, $resultType
                    ))
            ) {
                $results[] = $result;
            }

            if ($event->isPropagationStopped()) {
                break;
            }
        }

        return $results;
    }

    /**
     * @param $eventListeners
     *
     * @return mixed
     */
    private function _orderByPriority($eventListeners)
    {
        $comparisonFunction = function ($a, $b) {
            if ($a->getPriority() == $b->getPriority()) {
                // This will keep the order of same priority listeners in the order of subscribing
                return 1;
            }

            return ($a->getPriority() > $b->getPriority()) ? -1 : 1;
        };

        return $this->arr($eventListeners)->sortUsingFunction($comparisonFunction)->val();
    }
}