wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Repo;

use InvalidArgumentException;
use Wikibase\Lib\Store\EntityStoreWatcher;

/**
 * Dispatches a notification to a set of watchers.
 *
 * @todo should go into MediaWiki core.
 *
 * @license GPL-2.0-or-later
 * @author Daniel Kinzler
 */
class GenericEventDispatcher {

    /**
     * @var array<int,EntityStoreWatcher>
     */
    private $watchers = [];

    /**
     * @var int
     */
    private $key = 0;

    /**
     * @var class-string
     */
    private $interface;

    /**
     * @param class-string $interface the interface watchers must implement
     */
    public function __construct( $interface ) {
        $this->interface = $interface;
    }

    /**
     * Registers a watcher. The watcher will be called whenever
     * the dispatch() method is called, until the watcher is unregistered.
     *
     * @param EntityStoreWatcher $listener
     *
     * @throws InvalidArgumentException
     * @return int The listener key, for removing the listener later.
     */
    public function registerWatcher( $listener ) {
        if ( !is_subclass_of( $listener, $this->interface ) ) {
            throw new InvalidArgumentException( '$listener must implement ' . $this->interface );
        }

        $key = ++$this->key;
        $this->watchers[ $key ] = $listener;
        return $key;
    }

    /**
     * Unregisters a watcher using its registration key. The watcher will no longer
     * be called by dispatch().
     *
     * @param int $key A watcher key as returned by registerWatcher().
     *
     * @throws InvalidArgumentException
     */
    public function unregisterWatcher( $key ) {
        if ( is_object( $key ) || is_array( $key ) ) {
            throw new InvalidArgumentException( '$key must be a primitive value' );
        }

        if ( isset( $this->watchers[$key] ) ) {
            unset( $this->watchers[$key] );
        }
    }

    /**
     * Dispatches a notification to all registered watchers.
     *
     * @param string $event the name of the event, that is,
     *        the name of the method to call on the watchers.
     * @param mixed ...$args Any extra parameters are passed to the watcher method.
     *
     * @throws InvalidArgumentException
     */
    public function dispatch( $event, ...$args ) {
        if ( !is_string( $event ) ) {
            throw new InvalidArgumentException( '$event must be a string' );
        }

        foreach ( $this->watchers as $watcher ) {
            $watcher->$event( ...$args );
        }
    }

}