class HelpTopicSection

class HelpTopicSection extends HelpSectionPluginBase implements ContainerFactoryPluginInterface, SearchableHelpInterface {
  
  /**
   * The top level help topic plugins.
   *
   * @var \Drupal\help\HelpTopicPluginInterface[]
   */
  protected $topLevelPlugins;
  
  /**
   * The merged top level help topic plugins cache metadata.
   *
   * @var \Drupal\Core\Cache\CacheableMetadata
   */
  protected $cacheableMetadata;
  
  /**
   * Constructs a HelpTopicSection object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin ID for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\help\HelpTopicPluginManagerInterface $pluginManager
   *   The help topic plugin manager service.
   * @param \Drupal\Core\Render\RendererInterface $renderer
   *   The renderer.
   * @param \Drupal\Core\Language\LanguageDefault $defaultLanguage
   *   The default language object.
   * @param \Drupal\Core\Language\LanguageManagerInterface $languageManager
   *   The language manager.
   * @param \Drupal\Core\StringTranslation\TranslationManager $translationManager
   *   The translation manager. We are using a method that doesn't exist on an
   *   interface, so require this class.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, protected HelpTopicPluginManagerInterface $pluginManager, protected RendererInterface $renderer, protected LanguageDefault $defaultLanguage, protected LanguageManagerInterface $languageManager, protected TranslationManager $translationManager) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container->get('plugin.manager.help_topic'), $container->get('renderer'), $container->get('language.default'), $container->get('language_manager'), $container->get('string_translation'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheTags() {
    return $this->getCacheMetadata()
      ->getCacheTags();
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheContexts() {
    return $this->getCacheMetadata()
      ->getCacheContexts();
  }
  
  /**
   * {@inheritdoc}
   */
  public function getCacheMaxAge() {
    return $this->getCacheMetadata()
      ->getCacheMaxAge();
  }
  
  /**
   * {@inheritdoc}
   */
  public function listTopics() {
    // Map the top level help topic plugins to a list of topic links.
    return array_map(function (HelpTopicPluginInterface $topic) {
      return $topic->toLink();
    }, $this->getPlugins());
  }
  
  /**
   * Gets the top level help topic plugins.
   *
   * @return \Drupal\help\HelpTopicPluginInterface[]
   *   The top level help topic plugins.
   */
  protected function getPlugins() {
    if (!isset($this->topLevelPlugins)) {
      $definitions = $this->pluginManager
        ->getDefinitions();
      $this->topLevelPlugins = [];
      // Get all the top level topics and merge their list cache tags.
      foreach ($definitions as $definition) {
        if ($definition['top_level']) {
          $this->topLevelPlugins[$definition['id']] = $this->pluginManager
            ->createInstance($definition['id']);
        }
      }
      // Sort the top level topics by label and, if the labels match, then by
      // plugin ID.
      usort($this->topLevelPlugins, function (HelpTopicPluginInterface $a, HelpTopicPluginInterface $b) {
        $a_label = (string) $a->getLabel();
        $b_label = (string) $b->getLabel();
        if ($a_label === $b_label) {
          return $a->getPluginId() <=> $b->getPluginId();
        }
        return strnatcasecmp($a_label, $b_label);
      });
    }
    return $this->topLevelPlugins;
  }
  
  /**
   * {@inheritdoc}
   */
  public function listSearchableTopics() {
    $definitions = $this->pluginManager
      ->getDefinitions();
    return array_column($definitions, 'id');
  }
  
  /**
   * {@inheritdoc}
   */
  public function renderTopicForSearch($topic_id, LanguageInterface $language) {
    $plugin = $this->pluginManager
      ->createInstance($topic_id);
    if (!$plugin) {
      return [];
    }
    // We are rendering this topic for search indexing or search results,
    // possibly in a different language than the current language. The topic
    // title and body come from translatable things in the Twig template, so we
    // need to set the default language to the desired language, render them,
    // then restore the default language so we do not affect other cron
    // processes. Also, just in case there is an exception, wrap the whole
    // thing in a try/finally block, and reset the language in the finally part.
    $old_language = $this->defaultLanguage
      ->get();
    try {
      if ($old_language->getId() !== $language->getId()) {
        $this->defaultLanguage
          ->set($language);
        $this->translationManager
          ->setDefaultLangcode($language->getId());
        $this->languageManager
          ->reset();
      }
      $topic = [];
      // Render the title in this language.
      $title_build = [
        'title' => [
          '#type' => '#markup',
          '#markup' => $plugin->getLabel(),
        ],
      ];
      $topic['title'] = $this->renderer
        ->renderInIsolation($title_build);
      $cacheable_metadata = CacheableMetadata::createFromRenderArray($title_build);
      // Render the body in this language. For this, we need to set up a render
      // context, because the Twig plugins that provide the body assumes one
      // is present.
      $context = new RenderContext();
      $build = [
        'body' => $this->renderer
          ->executeInRenderContext($context, [
          $plugin,
          'getBody',
        ]),
      ];
      $topic['text'] = $this->renderer
        ->renderInIsolation($build);
      $cacheable_metadata->addCacheableDependency(CacheableMetadata::createFromRenderArray($build));
      $cacheable_metadata->addCacheableDependency($plugin);
      if (!$context->isEmpty()) {
        $cacheable_metadata->addCacheableDependency($context->pop());
      }
      // Add the other information.
      $topic['url'] = $plugin->toUrl();
      $topic['cacheable_metadata'] = $cacheable_metadata;
    } finally {
      // Restore the original language.
      if ($old_language->getId() !== $language->getId()) {
        $this->defaultLanguage
          ->set($old_language);
        $this->translationManager
          ->setDefaultLangcode($old_language->getId());
        $this->languageManager
          ->reset();
      }
    }
    return $topic;
  }
  
  /**
   * Gets the merged CacheableMetadata for all the top level help topic plugins.
   *
   * @return \Drupal\Core\Cache\CacheableMetadata
   *   The merged CacheableMetadata for all the top level help topic plugins.
   */
  protected function getCacheMetadata() {
    if (!isset($this->cacheableMetadata)) {
      $this->cacheableMetadata = new CacheableMetadata();
      foreach ($this->getPlugins() as $plugin) {
        $this->cacheableMetadata
          ->addCacheableDependency($plugin);
      }
    }
    return $this->cacheableMetadata;
  }

}