ReindexConfirm.php

<?php

namespace Drupal\search\Form;

use Drupal\Core\Form\ConfirmFormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;

/**
 * Provides the search reindex confirmation form.
 *
 * @internal
 */
class ReindexConfirm extends ConfirmFormBase {

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'search_reindex_confirm';
  }

  /**
   * {@inheritdoc}
   */
  public function getQuestion() {
    return $this
      ->t('Are you sure you want to re-index the site?');
  }

  /**
   * {@inheritdoc}
   */
  public function getDescription() {
    return $this
      ->t("This will re-index content in the search indexes of all active search pages. Searching will continue to work, but new content won't be indexed until all existing content has been re-indexed. This action cannot be undone.");
  }

  /**
   * {@inheritdoc}
   */
  public function getConfirmText() {
    return $this
      ->t('Re-index site');
  }

  /**
   * {@inheritdoc}
   */
  public function getCancelText() {
    return $this
      ->t('Cancel');
  }

  /**
   * {@inheritdoc}
   */
  public function getCancelUrl() {
    return new Url('entity.search_page.collection');
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    if ($form['confirm']) {

      // Ask each active search page to mark itself for re-index.
      $search_page_repository = \Drupal::service('search.search_page_repository');
      foreach ($search_page_repository
        ->getIndexableSearchPages() as $entity) {
        $entity
          ->getPlugin()
          ->markForReindex();
      }
      $this
        ->messenger()
        ->addStatus($this
        ->t('All search indexes will be rebuilt.'));
      $form_state
        ->setRedirectUrl($this
        ->getCancelUrl());
    }
  }

}