gnu-social/src/Core/Event.php

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<?php
// {{{ License
// This file is part of GNU social - https://www.gnu.org/software/social
//
// GNU social is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// GNU social is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with GNU social. If not, see <http://www.gnu.org/licenses/>.
// }}}
/**
* GNU social's event handler wrapper around Symfony's,
* keeping our old interface, which is more convenient and just as powerful
*
* @package GNUsocial
* @category Event
*
* @author Hugo Sales <hugo@fc.up.pt>
* @copyright 2020 Free Software Foundation, Inc http://www.fsf.org
* @license https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
*/
namespace App\Core;
use Symfony\Component\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\EventDispatcher\GenericEvent;
abstract class Event
{
/**
* Constants to be returned from event handlers, for increased clarity
*
* bool stop - Stop other handlers from processing the event
* bool next - Allow the other handlers to process the event
*/
public const stop = false;
public const next = true;
private static EventDispatcherInterface $dispatcher;
public static function setDispatcher(EventDispatcherInterface $dis): void
{
self::$dispatcher = $dis;
}
/**
* Add an event handler
*
* To run some code at a particular point in GNU social processing.
* Named events include receiving an XMPP message, adding a new notice,
* or showing part of an HTML page.
*
* The arguments to the handler vary by the event. Handlers can return
* two possible values: false means that the event has been replaced by
* the handler completely, and no default processing should be done.
* Non-false means successful handling, and that the default processing
* should succeed. (Note that this only makes sense for some events.)
*
* Handlers can also abort processing by throwing an exception; these will
* be caught by the closest code and displayed as errors.
*
* @param string $name Name of the event
* @param callable $handler Code to run
* @param int $priority Higher runs first
* @param string $ns
*
* @return void
*/
public static function addHandler(string $name,
callable $handler,
int $priority = 0,
string $ns = 'GNUsocial/'): void
{
self::$dispatcher->addListener(
$ns . $name,
function ($event, $event_name, $dispatcher) use ($handler) {
// Old style of events (preferred)
if ($event instanceof GenericEvent) {
if (call_user_func_array($handler, $event->getArguments()) == self::stop) {
$event->stopPropagation();
}
return $event;
}
// Symfony style of events
call_user_func($handler, $event, $event_name, $dispatcher);
return null;
},
$priority
);
}
/**
* Handle an event
*
* Events are any point in the code that we want to expose for admins
* or third-party developers to use.
*
* We pass in an array of arguments (including references, for stuff
* that can be changed), and each assigned handler gets run with those
* arguments. Exceptions can be thrown to indicate an error.
*
* @param string $name Name of the event that's happening
* @param array $args Arguments for handlers
* @param string $ns Namspace for the event
*
* @return bool flag saying whether to continue processing, based
* on results of handlers.
*/
public static function handle(string $name, array $args = [], string $ns = 'GNUsocial/'): bool
{
return !(self::$dispatcher->dispatch(
new GenericEvent($ns . $name, $args),
$name)->isPropagationStopped());
}
/**
* Check to see if an event handler exists
*
* Look to see if there's any handler for a given event, or narrow
* by providing the name of a specific plugin class.
*
* @param string $name Name of the event to look for
* @param string $plugin Optional name of the plugin class to look for
*
* @return bool flag saying whether such a handler exists
*/
public static function hasHandler(string $name, ?string $plugin = null): bool
{
$listeners = self::$dispatcher->getListeners($name);
if (isset($plugin)) {
foreach ($listeners as $handler) {
if (get_class($handler[0]) == $plugin) {
return true;
}
}
} else {
return !empty($listeners);
}
return false;
}
/**
* Get the array of handlers for $name
*
* @param string $name Name of event
*
* @return array
* @return array
*/
public static function getHandlers(string $name): array
{
return self::$dispatcher->getListeners($name);
}
}