class BlockContentAccessControlHandler

class BlockContentAccessControlHandler extends EntityAccessControlHandler implements EntityHandlerInterface {
    
    /**
     * The event dispatcher.
     *
     * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface
     */
    protected $eventDispatcher;
    
    /**
     * BlockContentAccessControlHandler constructor.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type.
     * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher
     *   The event dispatcher.
     */
    public function __construct(EntityTypeInterface $entity_type, EventDispatcherInterface $dispatcher) {
        parent::__construct($entity_type);
        $this->eventDispatcher = $dispatcher;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        return new static($entity_type, $container->get('event_dispatcher'));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
        if ($operation === 'view') {
            $access = AccessResult::allowedIf($entity->isPublished())
                ->orIf(AccessResult::allowedIfHasPermission($account, 'administer blocks'));
        }
        else {
            $access = parent::checkAccess($entity, $operation, $account);
        }
        // Add the entity as a cacheable dependency because access will at least be
        // determined by whether the block is reusable.
        $access->addCacheableDependency($entity);
        
        /** @var \Drupal\block_content\BlockContentInterface $entity */
        if ($entity->isReusable() === FALSE) {
            if (!$entity instanceof DependentAccessInterface) {
                throw new \LogicException("Non-reusable block entities must implement \\Drupal\\block_content\\Access\\DependentAccessInterface for access control.");
            }
            $dependency = $entity->getAccessDependency();
            if (empty($dependency)) {
                // If an access dependency has not been set let modules set one.
                $event = new BlockContentGetDependencyEvent($entity);
                $this->eventDispatcher
                    ->dispatch(BlockContentEvents::BLOCK_CONTENT_GET_DEPENDENCY, $event);
                $dependency = $event->getAccessDependency();
                if (empty($dependency)) {
                    return AccessResult::forbidden("Non-reusable blocks must set an access dependency for access control.");
                }
            }
            
            /** @var \Drupal\Core\Entity\EntityInterface $dependency */
            $access = $access->andIf($dependency->access($operation, $account, TRUE));
        }
        return $access;
    }

}