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    <h3>Editing: EventDispatcher.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\EventDispatcher;

use Psr\EventDispatcher\StoppableEventInterface;
use Symfony\Component\EventDispatcher\Debug\WrappedListener;

/**
 * The EventDispatcherInterface is the central point of Symfony's event listener system.
 *
 * Listeners are registered on the manager and events are dispatched through the
 * manager.
 *
 * @author Guilherme Blanco &lt;guilhermeblanco@hotmail.com&gt;
 * @author Jonathan Wage &lt;jonwage@gmail.com&gt;
 * @author Roman Borschel &lt;roman@code-factory.org&gt;
 * @author Bernhard Schussek &lt;bschussek@gmail.com&gt;
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 * @author Jordi Boggiano &lt;j.boggiano@seld.be&gt;
 * @author Jordan Alliot &lt;jordan.alliot@gmail.com&gt;
 * @author Nicolas Grekas &lt;p@tchwork.com&gt;
 */
class EventDispatcher implements EventDispatcherInterface
{
    private $listeners = [];
    private $sorted = [];
    private $optimized;

    public function __construct()
    {
        if (__CLASS__ === static::class) {
            $this-&gt;optimized = [];
        }
    }

    /**
     * {@inheritdoc}
     */
    public function dispatch(object $event, ?string $eventName = null): object
    {
        $eventName = $eventName ?? \get_class($event);

        if (null !== $this-&gt;optimized) {
            $listeners = $this-&gt;optimized[$eventName] ?? (empty($this-&gt;listeners[$eventName]) ? [] : $this-&gt;optimizeListeners($eventName));
        } else {
            $listeners = $this-&gt;getListeners($eventName);
        }

        if ($listeners) {
            $this-&gt;callListeners($listeners, $eventName, $event);
        }

        return $event;
    }

    /**
     * {@inheritdoc}
     */
    public function getListeners(?string $eventName = null)
    {
        if (null !== $eventName) {
            if (empty($this-&gt;listeners[$eventName])) {
                return [];
            }

            if (!isset($this-&gt;sorted[$eventName])) {
                $this-&gt;sortListeners($eventName);
            }

            return $this-&gt;sorted[$eventName];
        }

        foreach ($this-&gt;listeners as $eventName =&gt; $eventListeners) {
            if (!isset($this-&gt;sorted[$eventName])) {
                $this-&gt;sortListeners($eventName);
            }
        }

        return array_filter($this-&gt;sorted);
    }

    /**
     * {@inheritdoc}
     */
    public function getListenerPriority(string $eventName, $listener)
    {
        if (empty($this-&gt;listeners[$eventName])) {
            return null;
        }

        if (\is_array($listener) &amp;&amp; isset($listener[0]) &amp;&amp; $listener[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($listener)) {
            $listener[0] = $listener[0]();
            $listener[1] = $listener[1] ?? '__invoke';
        }

        foreach ($this-&gt;listeners[$eventName] as $priority =&gt; &amp;$listeners) {
            foreach ($listeners as &amp;$v) {
                if ($v !== $listener &amp;&amp; \is_array($v) &amp;&amp; isset($v[0]) &amp;&amp; $v[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($v)) {
                    $v[0] = $v[0]();
                    $v[1] = $v[1] ?? '__invoke';
                }
                if ($v === $listener || ($listener instanceof \Closure &amp;&amp; $v == $listener)) {
                    return $priority;
                }
            }
        }

        return null;
    }

    /**
     * {@inheritdoc}
     */
    public function hasListeners(?string $eventName = null)
    {
        if (null !== $eventName) {
            return !empty($this-&gt;listeners[$eventName]);
        }

        foreach ($this-&gt;listeners as $eventListeners) {
            if ($eventListeners) {
                return true;
            }
        }

        return false;
    }

    /**
     * {@inheritdoc}
     */
    public function addListener(string $eventName, $listener, int $priority = 0)
    {
        $this-&gt;listeners[$eventName][$priority][] = $listener;
        unset($this-&gt;sorted[$eventName], $this-&gt;optimized[$eventName]);
    }

    /**
     * {@inheritdoc}
     */
    public function removeListener(string $eventName, $listener)
    {
        if (empty($this-&gt;listeners[$eventName])) {
            return;
        }

        if (\is_array($listener) &amp;&amp; isset($listener[0]) &amp;&amp; $listener[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($listener)) {
            $listener[0] = $listener[0]();
            $listener[1] = $listener[1] ?? '__invoke';
        }

        foreach ($this-&gt;listeners[$eventName] as $priority =&gt; &amp;$listeners) {
            foreach ($listeners as $k =&gt; &amp;$v) {
                if ($v !== $listener &amp;&amp; \is_array($v) &amp;&amp; isset($v[0]) &amp;&amp; $v[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($v)) {
                    $v[0] = $v[0]();
                    $v[1] = $v[1] ?? '__invoke';
                }
                if ($v === $listener || ($listener instanceof \Closure &amp;&amp; $v == $listener)) {
                    unset($listeners[$k], $this-&gt;sorted[$eventName], $this-&gt;optimized[$eventName]);
                }
            }

            if (!$listeners) {
                unset($this-&gt;listeners[$eventName][$priority]);
            }
        }
    }

    /**
     * {@inheritdoc}
     */
    public function addSubscriber(EventSubscriberInterface $subscriber)
    {
        foreach ($subscriber-&gt;getSubscribedEvents() as $eventName =&gt; $params) {
            if (\is_string($params)) {
                $this-&gt;addListener($eventName, [$subscriber, $params]);
            } elseif (\is_string($params[0])) {
                $this-&gt;addListener($eventName, [$subscriber, $params[0]], $params[1] ?? 0);
            } else {
                foreach ($params as $listener) {
                    $this-&gt;addListener($eventName, [$subscriber, $listener[0]], $listener[1] ?? 0);
                }
            }
        }
    }

    /**
     * {@inheritdoc}
     */
    public function removeSubscriber(EventSubscriberInterface $subscriber)
    {
        foreach ($subscriber-&gt;getSubscribedEvents() as $eventName =&gt; $params) {
            if (\is_array($params) &amp;&amp; \is_array($params[0])) {
                foreach ($params as $listener) {
                    $this-&gt;removeListener($eventName, [$subscriber, $listener[0]]);
                }
            } else {
                $this-&gt;removeListener($eventName, [$subscriber, \is_string($params) ? $params : $params[0]]);
            }
        }
    }

    /**
     * Triggers the listeners of an event.
     *
     * This method can be overridden to add functionality that is executed
     * for each listener.
     *
     * @param callable[] $listeners The event listeners
     * @param string     $eventName The name of the event to dispatch
     * @param object     $event     The event object to pass to the event handlers/listeners
     */
    protected function callListeners(iterable $listeners, string $eventName, object $event)
    {
        $stoppable = $event instanceof StoppableEventInterface;

        foreach ($listeners as $listener) {
            if ($stoppable &amp;&amp; $event-&gt;isPropagationStopped()) {
                break;
            }
            $listener($event, $eventName, $this);
        }
    }

    /**
     * Sorts the internal list of listeners for the given event by priority.
     */
    private function sortListeners(string $eventName)
    {
        krsort($this-&gt;listeners[$eventName]);
        $this-&gt;sorted[$eventName] = [];

        foreach ($this-&gt;listeners[$eventName] as &amp;$listeners) {
            foreach ($listeners as $k =&gt; &amp;$listener) {
                if (\is_array($listener) &amp;&amp; isset($listener[0]) &amp;&amp; $listener[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($listener)) {
                    $listener[0] = $listener[0]();
                    $listener[1] = $listener[1] ?? '__invoke';
                }
                $this-&gt;sorted[$eventName][] = $listener;
            }
        }
    }

    /**
     * Optimizes the internal list of listeners for the given event by priority.
     */
    private function optimizeListeners(string $eventName): array
    {
        krsort($this-&gt;listeners[$eventName]);
        $this-&gt;optimized[$eventName] = [];

        foreach ($this-&gt;listeners[$eventName] as &amp;$listeners) {
            foreach ($listeners as &amp;$listener) {
                $closure = &amp;$this-&gt;optimized[$eventName][];
                if (\is_array($listener) &amp;&amp; isset($listener[0]) &amp;&amp; $listener[0] instanceof \Closure &amp;&amp; 2 &gt;= \count($listener)) {
                    $closure = static function (...$args) use (&amp;$listener, &amp;$closure) {
                        if ($listener[0] instanceof \Closure) {
                            $listener[0] = $listener[0]();
                            $listener[1] = $listener[1] ?? '__invoke';
                        }
                        ($closure = \Closure::fromCallable($listener))(...$args);
                    };
                } else {
                    $closure = $listener instanceof \Closure || $listener instanceof WrappedListener ? $listener : \Closure::fromCallable($listener);
                }
            }
        }

        return $this-&gt;optimized[$eventName];
    }
}
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