class HelpController

class HelpController extends ControllerBase {
  
  /**
   * The current route match.
   *
   * @var \Drupal\Core\Routing\RouteMatchInterface
   */
  protected $routeMatch;
  
  /**
   * The help section plugin manager.
   *
   * @var \Drupal\help\HelpSectionManager
   */
  protected $helpManager;
  
  /**
   * The module extension list.
   *
   * @var \Drupal\Core\Extension\ModuleExtensionList
   */
  protected $moduleExtensionList;
  
  /**
   * The module admin links service.
   *
   * @var \Drupal\system\ModuleAdminLinksHelper
   */
  protected $moduleAdminLinks;
  
  /**
   * The module permissions link service.
   *
   * @var \Drupal\user\ModulePermissionsLinkHelper
   */
  protected $modulePermissionsLinks;
  
  /**
   * Creates a new HelpController.
   *
   * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
   *   The current route match.
   * @param \Drupal\help\HelpSectionManager $help_manager
   *   The help section manager.
   * @param \Drupal\Core\Extension\ModuleExtensionList $module_extension_list
   *   The module extension list.
   * @param \Drupal\system\ModuleAdminLinksHelper|null $module_admin_links
   *   The module admin links.
   * @param \Drupal\user\ModulePermissionsLinkHelper|null $module_permissions_link
   *   The module permissions link.
   */
  public function __construct(RouteMatchInterface $route_match, HelpSectionManager $help_manager, ModuleExtensionList $module_extension_list, ?ModuleAdminLinksHelper $module_admin_links = NULL, ?ModulePermissionsLinkHelper $module_permissions_link = NULL) {
    $this->routeMatch = $route_match;
    $this->helpManager = $help_manager;
    $this->moduleExtensionList = $module_extension_list;
    if (!isset($module_admin_links)) {
      @trigger_error('Calling ' . __METHOD__ . ' without the $module_admin_tasks_helper argument is deprecated in drupal:10.2.0 and the $module_admin_tasks_helper argument will be required in drupal:11.0.0. See https://www.drupal.org/node/3038972', E_USER_DEPRECATED);
      $module_admin_links = \Drupal::service('system.module_admin_links_helper');
    }
    $this->moduleAdminLinks = $module_admin_links;
    if (!isset($module_permissions_link)) {
      @trigger_error('Calling HelpController::__construct() without the $module_permissions_link argument is deprecated in drupal:9.3.0 and the $module_permissions_link argument will be required in drupal:10.0.0. See https://www.drupal.org/node/3038972', E_USER_DEPRECATED);
      $module_permissions_link = \Drupal::service('user.module_permissions_link_helper');
    }
    $this->modulePermissionsLinks = $module_permissions_link;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('current_route_match'), $container->get('plugin.manager.help_section'), $container->get('extension.list.module'), $container->get('system.module_admin_links_helper'), $container->get('user.module_permissions_link_helper'));
  }
  
  /**
   * Prints a page listing various types of help.
   *
   * The page has sections defined by \Drupal\help\HelpSectionPluginInterface
   * plugins.
   *
   * @return array
   *   A render array for the help page.
   */
  public function helpMain() {
    $output = [];
    // We are checking permissions, so add the user.permissions cache context.
    $cacheability = new CacheableMetadata();
    $cacheability->addCacheContexts([
      'user.permissions',
    ]);
    $plugins = $this->helpManager
      ->getDefinitions();
    $cacheability->addCacheableDependency($this->helpManager);
    foreach ($plugins as $plugin_id => $plugin_definition) {
      // Check the provided permission.
      if (!empty($plugin_definition['permission']) && !$this->currentUser()
        ->hasPermission($plugin_definition['permission'])) {
        continue;
      }
      // Add the section to the page.
      /** @var \Drupal\help\HelpSectionPluginInterface $plugin */
      $plugin = $this->helpManager
        ->createInstance($plugin_id);
      $this_output = [
        '#theme' => 'help_section',
        '#title' => $plugin->getTitle(),
        '#description' => $plugin->getDescription(),
        '#empty' => $this->t('There is currently nothing in this section.'),
        '#links' => [],
        '#weight' => $plugin_definition['weight'],
      ];
      $links = $plugin->listTopics();
      if (is_array($links) && count($links)) {
        $this_output['#links'] = $links;
      }
      $cacheability->addCacheableDependency($plugin);
      $output[$plugin_id] = $this_output;
    }
    $cacheability->applyTo($output);
    return $output;
  }
  
  /**
   * Prints a page listing general help for a module.
   *
   * @param string $name
   *   A module name to display a help page for.
   *
   * @return array
   *   A render array as expected by
   *   \Drupal\Core\Render\RendererInterface::render().
   *
   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
   */
  public function helpPage($name) {
    $build = [];
    if ($this->moduleHandler()
      ->hasImplementations('help', $name)) {
      $module_name = $this->moduleExtensionList
        ->getName($name);
      $build['#title'] = $module_name;
      $info = $this->moduleExtensionList
        ->getExtensionInfo($name);
      if ($info[ExtensionLifecycle::LIFECYCLE_IDENTIFIER] === ExtensionLifecycle::EXPERIMENTAL) {
        $this->messenger()
          ->addWarning($this->t('This module is experimental. <a href=":url">Experimental modules</a> are provided for testing purposes only. Use at your own risk.', [
          ':url' => 'https://www.drupal.org/core/experimental',
        ]));
      }
      $temp = $this->moduleHandler()
        ->invoke($name, 'help', [
        "help.page.{$name}",
        $this->routeMatch,
      ]);
      if (empty($temp)) {
        $build['top'] = [
          '#markup' => $this->t('No help is available for module %module.', [
            '%module' => $module_name,
          ]),
        ];
      }
      else {
        if (!is_array($temp)) {
          $temp = [
            '#markup' => $temp,
          ];
        }
        $build['top'] = $temp;
      }
      // Only print list of administration pages if the module in question has
      // any such pages associated with it.
      $admin_tasks = $this->moduleAdminLinks
        ->getModuleAdminLinks($name);
      if ($module_permissions_link = $this->modulePermissionsLinks
        ->getModulePermissionsLink($name, $info['name'])) {
        $admin_tasks["user.admin_permissions.{$name}"] = $module_permissions_link;
      }
      if (!empty($admin_tasks)) {
        $links = [];
        foreach ($admin_tasks as $task) {
          $link['url'] = $task['url'];
          $link['title'] = $task['title'];
          $links[] = $link;
        }
        $build['links'] = [
          '#theme' => 'links__help',
          '#heading' => [
            'level' => 'h3',
            'text' => $this->t('@module administration pages', [
              '@module' => $module_name,
            ]),
          ],
          '#links' => $links,
        ];
      }
      return $build;
    }
    else {
      throw new NotFoundHttpException();
    }
  }

}