class SearchPage

class SearchPage extends ConfigEntityBase implements SearchPageInterface, EntityWithPluginCollectionInterface {

  /**
   * The name (plugin ID) of the search page entity.
   *
   * @var string
   */
  protected $id;

  /**
   * The label of the search page entity.
   *
   * @var string
   */
  protected $label;

  /**
   * The configuration of the search page entity.
   *
   * @var array
   */
  protected $configuration = [];

  /**
   * The search plugin ID.
   *
   * @var string
   */
  protected $plugin;

  /**
   * The path this search page will appear upon.
   *
   * This value is appended to 'search/' when building the path.
   *
   * @var string
   */
  protected $path;

  /**
   * The weight of the search page.
   *
   * @var int
   */
  protected $weight;

  /**
   * The plugin collection that stores search plugins.
   *
   * @var \Drupal\search\Plugin\SearchPluginCollection
   */
  protected $pluginCollection;

  /**
   * {@inheritdoc}
   */
  public function getPlugin() {
    return $this
      ->getPluginCollection()
      ->get($this->plugin);
  }

  /**
   * Encapsulates the creation of the search page's LazyPluginCollection.
   *
   * @return \Drupal\Component\Plugin\LazyPluginCollection
   *   The search page's plugin collection.
   */
  protected function getPluginCollection() {
    if (!$this->pluginCollection) {
      $this->pluginCollection = new SearchPluginCollection($this
        ->searchPluginManager(), $this->plugin, $this->configuration, $this
        ->id());
    }
    return $this->pluginCollection;
  }

  /**
   * {@inheritdoc}
   */
  public function getPluginCollections() {
    return [
      'configuration' => $this
        ->getPluginCollection(),
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function setPlugin($plugin_id) {
    $this->plugin = $plugin_id;
    $this
      ->getPluginCollection()
      ->addInstanceID($plugin_id);
  }

  /**
   * {@inheritdoc}
   */
  public function isIndexable() {
    return $this
      ->status() && $this
      ->getPlugin() instanceof SearchIndexingInterface;
  }

  /**
   * {@inheritdoc}
   */
  public function isDefaultSearch() {
    return $this
      ->searchPageRepository()
      ->getDefaultSearchPage() == $this
      ->id();
  }

  /**
   * {@inheritdoc}
   */
  public function getPath() {
    return $this->path;
  }

  /**
   * {@inheritdoc}
   */
  public function getWeight() {
    return $this->weight;
  }

  /**
   * {@inheritdoc}
   */
  public function postCreate(EntityStorageInterface $storage) {
    parent::postCreate($storage);

    // @todo Use self::applyDefaultValue() once
    //   https://www.drupal.org/node/2004756 is in.
    if (!isset($this->weight)) {
      $this->weight = $this
        ->isDefaultSearch() ? -10 : 0;
    }
  }

  /**
   * {@inheritdoc}
   */
  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
    parent::postSave($storage, $update);
    $this
      ->routeBuilder()
      ->setRebuildNeeded();
  }

  /**
   * {@inheritdoc}
   */
  public static function postDelete(EntityStorageInterface $storage, array $entities) {
    parent::postDelete($storage, $entities);
    $search_page_repository = \Drupal::service('search.search_page_repository');
    if (!$search_page_repository
      ->isSearchActive()) {
      $search_page_repository
        ->clearDefaultSearchPage();
    }
  }

  /**
   * Helper callback for uasort() to sort search page entities by status, weight and label.
   */
  public static function sort(ConfigEntityInterface $a, ConfigEntityInterface $b) {

    /** @var \Drupal\search\SearchPageInterface $a */

    /** @var \Drupal\search\SearchPageInterface $b */
    $a_status = (int) $a
      ->status();
    $b_status = (int) $b
      ->status();
    if ($a_status != $b_status) {
      return $b_status <=> $a_status;
    }
    return parent::sort($a, $b);
  }

  /**
   * Wraps the route builder.
   *
   * @return \Drupal\Core\Routing\RouteBuilderInterface
   *   An object for state storage.
   */
  protected function routeBuilder() {
    return \Drupal::service('router.builder');
  }

  /**
   * Wraps the config factory.
   *
   * @return \Drupal\Core\Config\ConfigFactoryInterface
   *   A config factory object.
   */
  protected function configFactory() {
    return \Drupal::service('config.factory');
  }

  /**
   * Wraps the search page repository.
   *
   * @return \Drupal\search\SearchPageRepositoryInterface
   *   A search page repository object.
   */
  protected function searchPageRepository() {
    return \Drupal::service('search.search_page_repository');
  }

  /**
   * Wraps the search plugin manager.
   *
   * @return \Drupal\Component\Plugin\PluginManagerInterface
   *   A search plugin manager object.
   */
  protected function searchPluginManager() {
    return \Drupal::service('plugin.manager.search');
  }

}