class HelpController

class HelpController extends ControllerBase {
    
    /**
     * Creates a new HelpController.
     *
     * @param \Drupal\Core\Routing\RouteMatchInterface $routeMatch
     *   The current route match.
     * @param \Drupal\help\HelpSectionManager $helpManager
     *   The help section manager.
     * @param \Drupal\Core\Extension\ModuleExtensionList $moduleExtensionList
     *   The module extension list.
     * @param \Drupal\system\ModuleAdminLinksHelper $moduleAdminLinks
     *   The module admin links.
     * @param \Drupal\user\ModulePermissionsLinkHelper $modulePermissionsLinks
     *   The module permissions link.
     */
    public function __construct(RouteMatchInterface $routeMatch, HelpSectionManager $helpManager, ModuleExtensionList $moduleExtensionList, ModuleAdminLinksHelper $moduleAdminLinks, ModulePermissionsLinkHelper $modulePermissionsLinks) {
    }
    
    /**
     * {@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();
        }
    }

}