class EntityListBuilder

class EntityListBuilder extends EntityHandlerBase implements EntityListBuilderInterface, EntityHandlerInterface {
    use MessengerTrait;
    use RedirectDestinationTrait;
    
    /**
     * The entity storage class.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $storage;
    
    /**
     * The entity type ID.
     *
     * @var string
     */
    protected $entityTypeId;
    
    /**
     * Information about the entity type.
     *
     * @var \Drupal\Core\Entity\EntityTypeInterface
     */
    protected $entityType;
    
    /**
     * The number of entities to list per page, or FALSE to list all entities.
     *
     * For example, set this to FALSE if the list uses client-side filters that
     * require all entities to be listed (like the views overview).
     *
     * @var int|false
     */
    protected $limit = 50;
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        return new static($entity_type, $container->get('entity_type.manager')
            ->getStorage($entity_type->id()));
    }
    
    /**
     * Constructs a new EntityListBuilder object.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type definition.
     * @param \Drupal\Core\Entity\EntityStorageInterface $storage
     *   The entity storage class.
     */
    public function __construct(EntityTypeInterface $entity_type, EntityStorageInterface $storage) {
        $this->entityTypeId = $entity_type->id();
        $this->storage = $storage;
        $this->entityType = $entity_type;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getStorage() {
        return $this->storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public function load() {
        $entity_ids = $this->getEntityIds();
        return $this->storage
            ->loadMultiple($entity_ids);
    }
    
    /**
     * Loads entity IDs using a pager sorted by the entity id.
     *
     * @return array
     *   An array of entity IDs.
     */
    protected function getEntityIds() {
        $query = $this->getStorage()
            ->getQuery()
            ->accessCheck(TRUE)
            ->sort($this->entityType
            ->getKey('id'));
        // Only add the pager if a limit is specified.
        if ($this->limit) {
            $query->pager($this->limit);
        }
        return $query->execute();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getOperations(EntityInterface $entity) {
        $operations = $this->getDefaultOperations($entity);
        $operations += $this->moduleHandler()
            ->invokeAll('entity_operation', [
            $entity,
        ]);
        $this->moduleHandler
            ->alter('entity_operation', $operations, $entity);
        uasort($operations, '\\Drupal\\Component\\Utility\\SortArray::sortByWeightElement');
        return $operations;
    }
    
    /**
     * Gets this list's default operations.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity the operations are for.
     *
     * @return array
     *   The array structure is identical to the return value of
     *   self::getOperations().
     */
    protected function getDefaultOperations(EntityInterface $entity) {
        $operations = [];
        if ($entity->access('update') && $entity->hasLinkTemplate('edit-form')) {
            $operations['edit'] = [
                'title' => $this->t('Edit'),
                'weight' => 10,
                'url' => $this->ensureDestination($entity->toUrl('edit-form')),
            ];
        }
        if ($entity->access('delete') && $entity->hasLinkTemplate('delete-form')) {
            $operations['delete'] = [
                'title' => $this->t('Delete'),
                'weight' => 100,
                'url' => $this->ensureDestination($entity->toUrl('delete-form')),
            ];
        }
        return $operations;
    }
    
    /**
     * Builds the header row for the entity listing.
     *
     * @return array
     *   A render array structure of header strings.
     *
     * @see \Drupal\Core\Entity\EntityListBuilder::render()
     */
    public function buildHeader() {
        $row['operations'] = $this->t('Operations');
        return $row;
    }
    
    /**
     * Builds a row for an entity in the entity listing.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity for this row of the list.
     *
     * @return array
     *   A render array structure of fields for this entity.
     *
     * @see \Drupal\Core\Entity\EntityListBuilder::render()
     */
    public function buildRow(EntityInterface $entity) {
        $row['operations']['data'] = $this->buildOperations($entity);
        return $row;
    }
    
    /**
     * Builds a renderable list of operation links for the entity.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity on which the linked operations will be performed.
     *
     * @return array
     *   A renderable array of operation links.
     *
     * @see \Drupal\Core\Entity\EntityListBuilder::buildRow()
     */
    public function buildOperations(EntityInterface $entity) {
        $build = [
            '#type' => 'operations',
            '#links' => $this->getOperations($entity),
        ];
        return $build;
    }
    
    /**
     * {@inheritdoc}
     *
     * Builds the entity listing as renderable array for table.html.twig.
     *
     * @todo Add a link to add a new item to the #empty text.
     */
    public function render() {
        $build['table'] = [
            '#type' => 'table',
            '#header' => $this->buildHeader(),
            '#title' => $this->getTitle(),
            '#rows' => [],
            '#empty' => $this->t('There are no @label yet.', [
                '@label' => $this->entityType
                    ->getPluralLabel(),
            ]),
            '#cache' => [
                'contexts' => $this->entityType
                    ->getListCacheContexts(),
                'tags' => $this->entityType
                    ->getListCacheTags(),
            ],
        ];
        foreach ($this->load() as $entity) {
            if ($row = $this->buildRow($entity)) {
                $build['table']['#rows'][$entity->id()] = $row;
            }
        }
        // Only add the pager if a limit is specified.
        if ($this->limit) {
            $build['pager'] = [
                '#type' => 'pager',
            ];
        }
        return $build;
    }
    
    /**
     * Gets the title of the page.
     */
    protected function getTitle() {
    }
    
    /**
     * Ensures that a destination is present on the given URL.
     *
     * @param \Drupal\Core\Url $url
     *   The URL object to which the destination should be added.
     *
     * @return \Drupal\Core\Url
     *   The updated URL object.
     */
    protected function ensureDestination(Url $url) {
        return $url->mergeOptions([
            'query' => $this->getRedirectDestination()
                ->getAsArray(),
        ]);
    }

}