class DeleteExpressionForm

class DeleteExpressionForm extends ConfirmFormBase {
    
    /**
     * The UUID of the expression in the rule.
     *
     * @var string
     */
    protected $uuid;
    
    /**
     * The RulesUI handler of the currently active UI.
     *
     * @var \Drupal\rules\Ui\RulesUiHandlerInterface
     */
    protected $rulesUiHandler;
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'rules_delete_expression';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, RulesUiHandlerInterface $rules_ui_handler = NULL, $uuid = NULL) {
        $this->rulesUiHandler = $rules_ui_handler;
        $this->uuid = $uuid;
        return parent::buildForm($form, $form_state);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConfirmText() {
        return $this->t('Delete');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getQuestion() {
        $rule_expression = $this->rulesUiHandler
            ->getComponent()
            ->getExpression();
        $expression_inside = $rule_expression->getExpression($this->uuid);
        if (!$expression_inside) {
            throw new NotFoundHttpException();
        }
        return $this->t('Are you sure you want to delete %title from %rule?', [
            '%title' => $expression_inside->getLabel(),
            '%rule' => $this->rulesUiHandler
                ->getComponentLabel(),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCancelUrl() {
        return $this->rulesUiHandler
            ->getBaseRouteUrl();
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $component = $this->rulesUiHandler
            ->getComponent();
        $component->getExpression()
            ->deleteExpression($this->uuid);
        $this->rulesUiHandler
            ->updateComponent($component);
        $form_state->setRedirectUrl($this->getCancelUrl());
    }

}