ReverseContainer.php

<?php

namespace Drupal\Component\DependencyInjection;

use Symfony\Component\DependencyInjection\Container as SymfonyContainer;
use Symfony\Component\DependencyInjection\ContainerInterface as SymfonyContainerInterface;

/**
 * Retrieves service IDs from the container for public services.
 *
 * Heavily inspired by \Symfony\Component\DependencyInjection\ReverseContainer.
 */
final class ReverseContainer {
    
    /**
     * The service container.
     *
     * @var \Drupal\Component\DependencyInjection\Container|\Symfony\Component\DependencyInjection\Container
     */
    private $serviceContainer;
    
    /**
     * A closure on the container that can search for services.
     *
     * @var \Closure
     */
    private $getServiceId;
    
    /**
     * A static map of services to a hash.
     *
     * @var array
     */
    private static $recordedServices = [];
    
    /**
     * Constructs a ReverseContainer object.
     *
     * @param \Drupal\Component\DependencyInjection\Container|\Symfony\Component\DependencyInjection\Container $serviceContainer
     *   The service container.
     */
    public function __construct($serviceContainer) {
        if (!($serviceContainer instanceof Container || $serviceContainer instanceof SymfonyContainer)) {
            throw new \InvalidArgumentException('The container must be an instance of \\Drupal\\Component\\DependencyInjection\\Container or \\Symfony\\Component\\DependencyInjection\\Container');
        }
        $this->serviceContainer = $serviceContainer;
        $this->getServiceId = \Closure::bind(function ($service) : ?string {
            return array_search($service, $this->services, TRUE) ?: NULL;
        }, $serviceContainer, $serviceContainer);
    }
    
    /**
     * Returns the ID of the passed object when it exists as a service.
     *
     * To be reversible, services need to be public.
     *
     * @param object $service
     *   The service to find the ID for.
     */
    public function getId($service) : ?string {
        if ($this->serviceContainer === $service || $service instanceof SymfonyContainerInterface) {
            return 'service_container';
        }
        $hash = $this->generateServiceIdHash($service);
        $id = self::$recordedServices[$hash] ?? ($this->getServiceId)($service);
        if ($id !== NULL && $this->serviceContainer
            ->has($id)) {
            self::$recordedServices[$hash] = $id;
            return $id;
        }
        return NULL;
    }
    
    /**
     * Records a map of the container's services.
     *
     * This method is used so that stale services can be serialized after a
     * container has been re-initialized.
     */
    public function recordContainer() : void {
        $service_recorder = \Closure::bind(function () : array {
            return array_filter($this->services, 'is_object');
        }, $this->serviceContainer, $this->serviceContainer);
        self::$recordedServices = array_merge(self::$recordedServices, array_flip(array_map([
            $this,
            'generateServiceIdHash',
        ], $service_recorder())));
    }
    
    /**
     * Generates an identifier for a service based on the object class and hash.
     *
     * @param object $object
     *   The object to generate an identifier for.
     *
     * @return string
     *   The object's class and hash concatenated together.
     */
    private function generateServiceIdHash(object $object) : string {
        // Include class name as an additional namespace for the hash since
        // spl_object_hash's return can be recycled. This still is not a 100%
        // guarantee to be unique but makes collisions incredibly difficult and even
        // then the interface would be preserved.
        // @see https://php.net/spl_object_hash#refsect1-function.spl-object-hash-notes
        return get_class($object) . spl_object_hash($object);
    }

}