class PrepareModulesEntityUninstallForm

class PrepareModulesEntityUninstallForm extends ConfirmFormBase {
  
  /**
   * The entity type ID of the entities to delete.
   *
   * @var string
   */
  protected $entityTypeId;
  
  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;
  
  /**
   * Constructs a PrepareModulesEntityUninstallForm object.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
    $this->entityTypeManager = $entity_type_manager;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('entity_type.manager'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'system_prepare_modules_entity_uninstall';
  }
  
  /**
   * {@inheritdoc}
   */
  public function getQuestion() {
    $entity_type = $this->entityTypeManager
      ->getDefinition($this->entityTypeId);
    return $this->t('Are you sure you want to delete all @entity_type_plural?', [
      '@entity_type_plural' => $entity_type->getPluralLabel(),
    ]);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDescription() {
    return $this->t('This action cannot be undone.<br />Make a backup of your database if you want to be able to restore these items.');
  }
  
  /**
   * {@inheritdoc}
   */
  public function getConfirmText() {
    $entity_type = $this->entityTypeManager
      ->getDefinition($this->entityTypeId);
    return $this->t('Delete all @entity_type_plural', [
      '@entity_type_plural' => $entity_type->getPluralLabel(),
    ]);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCancelUrl() {
    return Url::fromRoute('system.modules_uninstall');
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, $entity_type_id = NULL) {
    $this->entityTypeId = $entity_type_id;
    if (!$this->entityTypeManager
      ->hasDefinition($this->entityTypeId)) {
      throw new NotFoundHttpException();
    }
    $form = parent::buildForm($form, $form_state);
    $storage = $this->entityTypeManager
      ->getStorage($entity_type_id);
    $count = $storage->getQuery()
      ->accessCheck(FALSE)
      ->count()
      ->execute();
    $accessible_count = $storage->getQuery()
      ->accessCheck(TRUE)
      ->count()
      ->execute();
    $form['entity_type_id'] = [
      '#type' => 'value',
      '#value' => $entity_type_id,
    ];
    // Display a list of the 10 entity labels, if possible.
    $entity_type = $this->entityTypeManager
      ->getDefinition($entity_type_id);
    if ($count == 0) {
      $form['total'] = [
        '#markup' => $this->t('There are 0 @entity_type_plural to delete.', [
          '@entity_type_plural' => $entity_type->getPluralLabel(),
        ]),
      ];
    }
    elseif ($accessible_count > 0 && $entity_type->hasKey('label')) {
      $recent_entity_ids = $storage->getQuery()
        ->accessCheck(TRUE)
        ->sort($entity_type->getKey('id'), 'DESC')
        ->pager(10)
        ->execute();
      $recent_entities = $storage->loadMultiple($recent_entity_ids);
      $labels = [];
      foreach ($recent_entities as $entity) {
        $labels[] = $entity->label();
      }
      if ($labels) {
        $form['recent_entity_labels'] = [
          '#theme' => 'item_list',
          '#items' => $labels,
        ];
        $more_count = $count - count($labels);
        $form['total'] = [
          '#markup' => $this->formatPlural($more_count, 'And <strong>@count</strong> more @entity_type_singular.', 'And <strong>@count</strong> more @entity_type_plural.', [
            '@entity_type_singular' => $entity_type->getSingularLabel(),
            '@entity_type_plural' => $entity_type->getPluralLabel(),
          ]),
          '#access' => (bool) $more_count,
        ];
      }
    }
    else {
      $form['total'] = [
        '#markup' => $this->formatPlural($count, 'This will delete <strong>@count</strong> @entity_type_singular.', 'This will delete <strong>@count</strong> @entity_type_plural.', [
          '@entity_type_singular' => $entity_type->getSingularLabel(),
          '@entity_type_plural' => $entity_type->getPluralLabel(),
        ]),
      ];
    }
    $form['description']['#prefix'] = '<p>';
    $form['description']['#suffix'] = '</p>';
    $form['description']['#weight'] = 5;
    // Only show the delete button if there are entities to delete.
    $form['actions']['submit']['#access'] = (bool) $count;
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $entity_type_id = $form_state->getValue('entity_type_id');
    $entity_type_plural = $this->entityTypeManager
      ->getDefinition($entity_type_id)
      ->getPluralLabel();
    $batch_builder = (new BatchBuilder())->setTitle($this->t('Deleting @entity_type_plural', [
      '@entity_type_plural' => $entity_type_plural,
    ]))
      ->setProgressMessage('')
      ->setFinishCallback([
      __CLASS__,
      'moduleBatchFinished',
    ])
      ->addOperation([
      __CLASS__,
      'deleteContentEntities',
    ], [
      $entity_type_id,
    ]);
    batch_set($batch_builder->toArray());
  }
  
  /**
   * Deletes the content entities of the specified entity type.
   *
   * @param string $entity_type_id
   *   The entity type ID from which data will be deleted.
   * @param array|\ArrayAccess $context
   *   The batch context array, passed by reference.
   *
   * @internal
   *   This batch callback is only meant to be used by this form.
   */
  public static function deleteContentEntities($entity_type_id, &$context) {
    $storage = \Drupal::entityTypeManager()->getStorage($entity_type_id);
    // Set the entity type ID in the results array so we can access it in the
    // batch finished callback.
    $context['results']['entity_type_id'] = $entity_type_id;
    if (!isset($context['sandbox']['progress'])) {
      $context['sandbox']['progress'] = 0;
      $context['sandbox']['max'] = $storage->getQuery()
        ->accessCheck(FALSE)
        ->count()
        ->execute();
    }
    $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
    $entity_ids = $storage->getQuery()
      ->accessCheck(FALSE)
      ->sort($entity_type->getKey('id'), 'ASC')
      ->range(0, 10)
      ->execute();
    if ($entities = $storage->loadMultiple($entity_ids)) {
      $storage->delete($entities);
    }
    // Sometimes deletes cause secondary deletes. For example, deleting a
    // taxonomy term can cause its children to be deleted too.
    $context['sandbox']['progress'] = $context['sandbox']['max'] - $storage->getQuery()
      ->accessCheck(FALSE)
      ->count()
      ->execute();
    // Inform the batch engine that we are not finished and provide an
    // estimation of the completion level we reached.
    if (count($entity_ids) > 0 && $context['sandbox']['progress'] != $context['sandbox']['max']) {
      $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
      $context['message'] = new TranslatableMarkup('Deleting items... Completed @percentage% (@current of @total).', [
        '@percentage' => round(100 * $context['sandbox']['progress'] / $context['sandbox']['max']),
        '@current' => $context['sandbox']['progress'],
        '@total' => $context['sandbox']['max'],
      ]);
    }
    else {
      $context['finished'] = 1;
    }
  }
  
  /**
   * Implements callback_batch_finished().
   *
   * Finishes the module batch, redirect to the uninstall page and output the
   * successful data deletion message.
   */
  public static function moduleBatchFinished($success, $results, $operations) {
    $entity_type_plural = \Drupal::entityTypeManager()->getDefinition($results['entity_type_id'])
      ->getPluralLabel();
    \Drupal::messenger()->addStatus(new TranslatableMarkup('All @entity_type_plural have been deleted.', [
      '@entity_type_plural' => $entity_type_plural,
    ]));
    return new RedirectResponse(Url::fromRoute('system.modules_uninstall')->setAbsolute()
      ->toString());
  }

}