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());
    }

}