class MenuLinkDefaultForm

class MenuLinkDefaultForm implements MenuLinkFormInterface, ContainerInjectionInterface {
    use StringTranslationTrait;
    
    /**
     * The edited menu link.
     *
     * @var \Drupal\Core\Menu\MenuLinkInterface
     */
    protected $menuLink;
    
    /**
     * The menu link manager.
     *
     * @var \Drupal\Core\Menu\MenuLinkManagerInterface
     */
    protected $menuLinkManager;
    
    /**
     * The parent form selector service.
     *
     * @var \Drupal\Core\Menu\MenuParentFormSelectorInterface
     */
    protected $menuParentSelector;
    
    /**
     * The module handler service.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * Constructs a new \Drupal\Core\Menu\Form\MenuLinkDefaultForm.
     *
     * @param \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager
     *   The menu link manager.
     * @param \Drupal\Core\Menu\MenuParentFormSelectorInterface $menu_parent_selector
     *   The menu parent form selector service.
     * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
     *   The string translation.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler;
     */
    public function __construct(MenuLinkManagerInterface $menu_link_manager, MenuParentFormSelectorInterface $menu_parent_selector, TranslationInterface $string_translation, ModuleHandlerInterface $module_handler) {
        $this->menuLinkManager = $menu_link_manager;
        $this->menuParentSelector = $menu_parent_selector;
        $this->stringTranslation = $string_translation;
        $this->moduleHandler = $module_handler;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('plugin.manager.menu.link'), $container->get('menu.parent_form_selector'), $container->get('string_translation'), $container->get('module_handler'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function setMenuLinkInstance(MenuLinkInterface $menu_link) {
        $this->menuLink = $menu_link;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
        $form['#title'] = $this->t('Edit menu link %title', [
            '%title' => $this->menuLink
                ->getTitle(),
        ]);
        $provider = $this->menuLink
            ->getProvider();
        $form['info'] = [
            '#type' => 'item',
            '#title' => $this->t('This link is provided by the @name module. The title and path cannot be edited.', [
                '@name' => $this->moduleHandler
                    ->getName($provider),
            ]),
        ];
        $form['id'] = [
            '#type' => 'value',
            '#value' => $this->menuLink
                ->getPluginId(),
        ];
        $link = [
            '#type' => 'link',
            '#title' => $this->menuLink
                ->getTitle(),
            '#url' => $this->menuLink
                ->getUrlObject(),
        ];
        $form['path'] = [
            'link' => $link,
            '#type' => 'item',
            '#title' => $this->t('Link'),
        ];
        $form['enabled'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Enable menu link'),
            '#description' => $this->t('Menu links that are not enabled will not be listed in any menu.'),
            '#default_value' => $this->menuLink
                ->isEnabled(),
        ];
        $form['expanded'] = [
            '#type' => 'checkbox',
            '#title' => t('Show as expanded'),
            '#description' => $this->t('If selected and this menu link has children, the menu will always appear expanded. This option may be overridden for the entire menu tree when placing a menu block.'),
            '#default_value' => $this->menuLink
                ->isExpanded(),
        ];
        $menu_parent = $this->menuLink
            ->getMenuName() . ':' . $this->menuLink
            ->getParent();
        $form['menu_parent'] = $this->menuParentSelector
            ->parentSelectElement($menu_parent, $this->menuLink
            ->getPluginId());
        $form['menu_parent']['#title'] = $this->t('Parent link');
        $form['menu_parent']['#description'] = $this->t('The maximum depth for a link and all its children is fixed. Some menu links may not be available as parents if selecting them would exceed this limit.');
        $form['menu_parent']['#attributes']['class'][] = 'menu-title-select';
        $delta = max(abs($this->menuLink
            ->getWeight()), 50);
        $form['weight'] = [
            '#type' => 'number',
            '#min' => -$delta,
            '#max' => $delta,
            '#default_value' => $this->menuLink
                ->getWeight(),
            '#title' => $this->t('Weight'),
            '#description' => $this->t('Link weight among links in the same menu at the same depth. In the menu, the links with high weight will sink and links with a low weight will be positioned nearer the top.'),
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function extractFormValues(array &$form, FormStateInterface $form_state) {
        // Start from the complete, original, definition.
        $new_definition = $this->menuLink
            ->getPluginDefinition();
        // Since the ID may not be present in the definition used to construct the
        // plugin, add it here so it's available to any consumers of this method.
        $new_definition['id'] = $form_state->getValue('id');
        $new_definition['enabled'] = $form_state->getValue('enabled') ? 1 : 0;
        $new_definition['weight'] = (int) $form_state->getValue('weight');
        $new_definition['expanded'] = $form_state->getValue('expanded') ? 1 : 0;
        list($menu_name, $parent) = explode(':', $form_state->getValue('menu_parent'), 2);
        if (!empty($menu_name)) {
            $new_definition['menu_name'] = $menu_name;
        }
        if (isset($parent)) {
            $new_definition['parent'] = $parent;
        }
        return $new_definition;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
        $new_definition = $this->extractFormValues($form, $form_state);
        return $this->menuLinkManager
            ->updateDefinition($this->menuLink
            ->getPluginId(), $new_definition);
    }

}