<?php

/**
 * @file
 * Contains \Drupal\Core\Entity\EntityListBuilder.
 */

namespace Drupal\Core\Entity;

use Drupal\Core\Extension\ModuleHandlerInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Component\Utility\SafeMarkup;

/**
 * Defines a generic implementation to build a listing of entities.
 *
 * @ingroup entity_api
 */
class EntityListBuilder extends EntityHandlerBase implements EntityListBuilderInterface, EntityHandlerInterface {

  /**
   * 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.
   *
   * @var int
   */
  protected $limit = 50;

  /**
   * {@inheritdoc}
   */
  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
    return new static(
      $entity_type,
      $container->get('entity.manager')->getStorage($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();
    $keys = $this->entityType->getKeys();
    return $query
      ->sort($keys['id'])
      ->pager($this->limit)
      ->execute();
  }

  /**
   * Returns the escaped label of an entity.
   *
   * @param \Drupal\Core\Entity\EntityInterface $entity
   *   The entity being listed.
   *
   * @return string
   *   The escaped entity label.
   */
  protected function getLabel(EntityInterface $entity) {
    return SafeMarkup::checkPlain($entity->label());
  }

  /**
   * {@inheritdoc}
   */
  public function getOperations(EntityInterface $entity) {
    $operations = $this->getDefaultOperations($entity);
    $operations += $this->moduleHandler()->invokeAll('entity_operation', array($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) {
    $operations = array();
    if ($entity->access('update') && $entity->hasLinkTemplate('edit-form')) {
      $operations['edit'] = array(
        'title' => $this->t('Edit'),
        'weight' => 10,
        'url' => $entity->urlInfo('edit-form'),
      );
    }
    if ($entity->access('delete') && $entity->hasLinkTemplate('delete-form')) {
      $operations['delete'] = array(
        'title' => $this->t('Delete'),
        'weight' => 100,
        'url' => $entity->urlInfo('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 = array(
      '#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'] = array(
      '#type' => 'table',
      '#header' => $this->buildHeader(),
      '#title' => $this->getTitle(),
      '#rows' => array(),
      '#empty' => $this->t('There is no @label yet.', array('@label' => $this->entityType->getLabel())),
      '#cache' => [
        'contexts' => $this->entityType->getListCacheContexts(),
      ],
    );
    foreach ($this->load() as $entity) {
      if ($row = $this->buildRow($entity)) {
        $build['table']['#rows'][$entity->id()] = $row;
      }
    }
    $build['pager'] = array(
      '#type' => 'pager',
    );
    return $build;
  }

  /**
   * Returns the title of the page.
   *
   * @return string
   *   A string title of the page.
   */
  protected function getTitle() {
    return;
  }

}