class HelpTopicSection

class HelpTopicSection extends HelpSectionPluginBase implements ContainerFactoryPluginInterface, SearchableHelpInterface {
    
    /**
     * The plugin manager.
     *
     * @var \Drupal\help_topics\HelpTopicPluginManagerInterface
     */
    protected $pluginManager;
    
    /**
     * The top level help topic plugins.
     *
     * @var \Drupal\help_topics\HelpTopicPluginInterface[]
     */
    protected $topLevelPlugins;
    
    /**
     * The merged top level help topic plugins cache metadata.
     *
     * @var \Drupal\Core\Cache\CacheableMetadata
     */
    protected $cacheableMetadata;
    
    /**
     * The Renderer service to format the username and node.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * The default language object.
     *
     * @var \Drupal\Core\Language\LanguageDefault
     */
    protected $defaultLanguage;
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * The string translation service.
     *
     * @var \Drupal\Core\StringTranslation\TranslationManager
     */
    protected $translationManager;
    
    /**
     * 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_topics\HelpTopicPluginManagerInterface $plugin_manager
     *   The help topic plugin manager service.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer.
     * @param \Drupal\Core\Language\LanguageDefault $default_language
     *   The default language object.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\StringTranslation\TranslationManager $translation_manager
     *   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, HelpTopicPluginManagerInterface $plugin_manager, RendererInterface $renderer, LanguageDefault $default_language, LanguageManagerInterface $language_manager, TranslationManager $translation_manager) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->pluginManager = $plugin_manager;
        $this->renderer = $renderer;
        $this->defaultLanguage = $default_language;
        $this->languageManager = $language_manager;
        $this->translationManager = $translation_manager;
    }
    
    /**
     * {@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_topics\HelpTopicPluginInterface[]
     *   The top level help topic plugins.
     */
    protected function getPlugins() {
        if (!isset($this->topLevelPlugins)) {
            $definitions = $this->pluginManager
                ->getDefinitions();
            // Get all the top level topics and merge their list cache tags.
            foreach ($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'] = $this->renderer
                ->renderPlain($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'] = $this->renderer
                ->renderPlain($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;
    }

}