class SettingsForm

class SettingsForm extends ConfigFormBase {
  
  /**
   * The RulesUI handler of the currently active UI.
   *
   * @var \Drupal\rules\Ui\RulesUiConfigHandler
   */
  protected $rulesUiHandler;
  
  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return [
      'rules_test_ui_embed.settings',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'rules_test_ui_embed_settings';
  }
  
  /**
   * {@inheritdoc}
   */
  protected function config($name) {
    // Get the editable config from the Rules UI handlers, such that any
    // interim changes to the contained Rules component are picked up.
    $config = $this->rulesUiHandler ? $this->rulesUiHandler
      ->getConfig() : NULL;
    if ($config->getName() == $name && in_array($name, $this->getEditableConfigNames())) {
      return $config;
    }
    return parent::config($name);
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, RulesUiConfigHandler $rules_ui_handler = NULL) {
    $form = parent::buildForm($form, $form_state);
    $this->rulesUiHandler = $rules_ui_handler;
    $config = $this->config('rules_test_ui_embed.settings');
    $form['css_file'] = [
      '#type' => 'textfield',
      '#title' => $this->t('CSS file'),
      '#default_value' => $config->get('css.0.file'),
      '#required' => TRUE,
    ];
    $form['conditions'] = $this->rulesUiHandler
      ->getForm()
      ->buildForm([], $form_state);
    $form['actions']['cancel'] = [
      '#type' => 'submit',
      '#limit_validation_errors' => [
        [
          'locked',
        ],
      ],
      '#value' => $this->t('Cancel'),
      '#submit' => [
        '::cancel',
      ],
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function validateForm(array &$form, FormStateInterface $form_state) {
    parent::validateForm($form, $form_state);
    $this->rulesUiHandler
      ->getForm()
      ->validateForm($form['conditions'], $form_state);
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->rulesUiHandler
      ->getForm()
      ->submitForm($form['conditions'], $form_state);
    $this->config('rules_test_ui_embed.settings')
      ->set('css.0.file', $form_state->getValue('css_file'))
      ->save();
    // Also remove the temporarily stored component, it has been persisted now.
    $this->rulesUiHandler
      ->clearTemporaryStorage();
    parent::submitForm($form, $form_state);
  }
  
  /**
   * Form submission handler for the 'cancel' action.
   */
  public function cancel(array $form, FormStateInterface $form_state) {
    $this->rulesUiHandler
      ->clearTemporaryStorage();
    $this->messenger()
      ->addMessage($this->t('Canceled.'));
    $form_state->setRedirectUrl($this->rulesUiHandler
      ->getBaseRouteUrl());
  }

}