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()
            ->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' => $entity_type->getPluralLabel(),
                ]),
            ];
        }
        elseif ($entity_type->hasKey('label')) {
            $recent_entity_ids = $storage->getQuery()
                ->sort($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 = [
            'title' => t('Deleting @entity_type_plural', [
                '@entity_type_plural' => $entity_type_plural,
            ]),
            'operations' => [
                [
                    [
                        __CLASS__,
                        'deleteContentEntities',
                    ],
                    [
                        $entity_type_id,
                    ],
                ],
            ],
            'finished' => [
                __CLASS__,
                'moduleBatchFinished',
            ],
            'progress_message' => '',
        ];
        batch_set($batch);
    }
    
    /**
     * 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()
                ->count()
                ->execute();
        }
        $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
        $entity_ids = $storage->getQuery()
            ->sort($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'] - $storage->getQuery()
            ->count()
            ->execute();
        // Inform the batch engine that we are not finished and provide an
        // estimation of the completion level we reached.
        if (count($entity_ids) > 0 && $context['sandbox']['progress'] != $context['sandbox']['max']) {
            $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
            $context['message'] = t('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(t('All @entity_type_plural have been deleted.', [
            '@entity_type_plural' => $entity_type_plural,
        ]));
        return new RedirectResponse(Url::fromRoute('system.modules_uninstall')->setAbsolute()
            ->toString());
    }

}