acquia_cms_search-1.3.0/src/Plugin/views/area/FallbackView.php

<?php

namespace Drupal\acquia_cms_search\Plugin\views\area;

use Drupal\search_api\Plugin\views\query\SearchApiQuery;
use Drupal\search_api\SearchApiException;
use Drupal\views\Plugin\views\area\View;

/**
 * Defines a view area handler that short-circuits if the search server is up.
 *
 * This handler is only useful on Search API-based views. If the search server
 * that powers the view is available, this will not display anything. If the
 * server is down, it will display a view. If the view is not powered by Search
 * API, this handler will not display anything.
 *
 * @ViewsArea("view_fallback")
 */
final class FallbackView extends View {

  /**
   * {@inheritdoc}
   */
  public function preQuery() {
    $query = $this->view->getQuery();
    $simulate_unavailable = $this->options['simulate_unavailable'] ?? FALSE;

    if ($query instanceof SearchApiQuery && $simulate_unavailable) {
      $query->abort();
    }
    parent::preQuery();
  }

  /**
   * {@inheritdoc}
   */
  public function render($empty = FALSE) {
    if ($this->isServerAvailable()) {
      $this->isEmpty = TRUE;
      return [];
    }
    return parent::render($empty);
  }

  /**
   * Checks if the Search API server for this view is available.
   *
   * @return bool
   *   TRUE if the server is available, FALSE otherwise. If the view's query
   *   handler is not Search API's query handler, returns TRUE.
   */
  private function isServerAvailable() : bool {
    $query = $this->view->getQuery();

    if ($query instanceof SearchApiQuery) {
      if ($query->shouldAbort()) {
        return FALSE;
      }

      try {
        return $query->getIndex()
          ->getServerInstance()
          ->getBackend()
          ->isAvailable();
      }
      catch (SearchApiException $e) {
        return FALSE;
      }
    }
    return TRUE;
  }

}