<?php

/*

 * This file is part of the Symfony package.

 *

 * (c) Fabien Potencier <fabien@symfony.com>

 *

 * For the full copyright and license information, please view the LICENSE

 * file that was distributed with this source code.

 */

namespace Symfony\Component\EventDispatcher;

/**

 * 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 Bernhard Schussek <bschussek@gmail.com>

 *

 * @api

 */

interface EventDispatcherInterface

{

    /**

     * Dispatches an event to all registered listeners.

     *

     * @param string $eventName The name of the event to dispatch. The name of

     *                          the event is the name of the method that is

     *                          invoked on listeners.

     * @param Event $event The event to pass to the event handlers/listeners.

     *                     If not supplied, an empty Event instance is created.

     *

     * @api

     */

    function dispatch($eventName, Event $event = null);

    /**

     * Adds an event listener that listens on the specified events.

     *

     * @param string   $eventName The event to listen on

     * @param callable $listener  The listener

     * @param integer  $priority  The higher this value, the earlier an event

     *                            listener will be triggered in the chain (defaults to 0)

     *

     * @api

     */

    function addListener($eventName, $listener, $priority = 0);

    /**

     * Adds an event subscriber. The subscriber is asked for all the events he is

     * interested in and added as a listener for these events.

     *

     * @param EventSubscriberInterface $subscriber The subscriber.

     *

     * @api

     */

    function addSubscriber(EventSubscriberInterface $subscriber);

    /**

     * Removes an event listener from the specified events.

     *

     * @param string|array $eventName The event(s) to remove a listener from.

     * @param object $listener The listener object to remove.

     */

    function removeListener($eventName, $listener);

    /**

     * Removes an event subscriber.

     *

     * @param EventSubscriberInterface $subscriber The subscriber.

     */

    function removeSubscriber(EventSubscriberInterface $subscriber);

    /**

     * Gets the listeners of a specific event or all listeners.

     *

     * @param string $eventName The name of the event.

     *

     * @return array The event listeners for the specified event, or all event

     *               listeners by event name.

     */

    function getListeners($eventName = null);

    /**

     * Checks whether an event has any registered listeners.

     *

     * @param string $eventName The name of the event.

     *

     * @return Boolean TRUE if the specified event has any listeners, FALSE

     *                 otherwise.

     */

    function hasListeners($eventName = null);

}