class EntryPoint

class EntryPoint extends ControllerBase {
    
    /**
     * The JSON:API resource type repository.
     *
     * @var \Drupal\jsonapi\ResourceType\ResourceTypeRepositoryInterface
     */
    protected $resourceTypeRepository;
    
    /**
     * The account object.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $user;
    
    /**
     * EntryPoint constructor.
     *
     * @param \Drupal\jsonapi\ResourceType\ResourceTypeRepositoryInterface $resource_type_repository
     *   The resource type repository.
     * @param \Drupal\Core\Session\AccountInterface $user
     *   The current user.
     */
    public function __construct(ResourceTypeRepositoryInterface $resource_type_repository, AccountInterface $user) {
        $this->resourceTypeRepository = $resource_type_repository;
        $this->user = $user;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('jsonapi.resource_type.repository'), $container->get('current_user'));
    }
    
    /**
     * Controller to list all the resources.
     *
     * @return \Drupal\jsonapi\ResourceResponse
     *   The response object.
     */
    public function index() {
        $cacheability = (new CacheableMetadata())->addCacheContexts([
            'user.roles:authenticated',
        ])
            ->addCacheTags([
            'jsonapi_resource_types',
        ]);
        // Only build URLs for exposed resources.
        $resources = array_filter($this->resourceTypeRepository
            ->all(), function ($resource) {
            return !$resource->isInternal();
        });
        $self_link = new Link(new CacheableMetadata(), Url::fromRoute('jsonapi.resource_list'), 'self');
        $urls = array_reduce($resources, function (LinkCollection $carry, ResourceType $resource_type) {
            if ($resource_type->isLocatable() || $resource_type->isMutable()) {
                $route_suffix = $resource_type->isLocatable() ? 'collection' : 'collection.post';
                $url = Url::fromRoute(sprintf('jsonapi.%s.%s', $resource_type->getTypeName(), $route_suffix))
                    ->setAbsolute();
                // Using a resource type name in place of a link relation type is not
                // technically valid. However, since it matches the link key, it will
                // not actually be serialized since the rel is omitted if it matches the
                // link key; because of that no client can rely on it. Once an extension
                // relation type is implemented for links to a collection, that should
                // be used instead. Unfortunately, the `collection` link relation type
                // would not be semantically correct since it would imply that the
                // entrypoint is a *member* of the link target.
                // @todo: implement an extension relation type to signal that this is a primary collection resource.
                $link_relation_type = $resource_type->getTypeName();
                return $carry->withLink($resource_type->getTypeName(), new Link(new CacheableMetadata(), $url, $link_relation_type));
            }
            return $carry;
        }, new LinkCollection([
            'self' => $self_link,
        ]));
        $meta = [];
        if ($this->user
            ->isAuthenticated()) {
            $current_user_uuid = $this->entityTypeManager()
                ->getStorage('user')
                ->load($this->user
                ->id())
                ->uuid();
            $meta['links']['me'] = [
                'meta' => [
                    'id' => $current_user_uuid,
                ],
            ];
            $cacheability->addCacheContexts([
                'user',
            ]);
            try {
                $me_url = Url::fromRoute('jsonapi.user--user.individual', [
                    'entity' => $current_user_uuid,
                ])->setAbsolute()
                    ->toString(TRUE);
                $meta['links']['me']['href'] = $me_url->getGeneratedUrl();
                // The cacheability of the `me` URL is the cacheability of that URL
                // itself and the currently authenticated user.
                $cacheability = $cacheability->merge($me_url);
            } catch (RouteNotFoundException $e) {
                // Do not add the link if the route is disabled or marked as internal.
            }
        }
        $response = new ResourceResponse(new JsonApiDocumentTopLevel(new ResourceObjectData([]), new NullIncludedData(), $urls, $meta));
        return $response->addCacheableDependency($cacheability);
    }

}