class RulesAbstractPluginUI

class RulesAbstractPluginUI extends RulesPluginUI {
    
    /**
     * Overrides RulesPluginUI::form().
     *
     * Overridden to invoke the abstract plugins form alter callback and to add
     * the negation checkbox for conditions.
     */
    public function form(&$form, &$form_state, $options = array()) {
        parent::form($form, $form_state, $options);
        if ($this->element instanceof RulesCondition) {
            $form['negate'] = array(
                '#title' => t('Negate'),
                '#type' => 'checkbox',
                '#description' => t('If checked, the condition result is negated such that it returns TRUE if it evaluates to FALSE.'),
                '#default_value' => $this->element
                    ->isNegated(),
                '#weight' => 5,
            );
        }
        $this->element
            ->call('form_alter', array(
            &$form,
            &$form_state,
            $options,
        ));
    }
    
    /**
     * @param array $form
     *   The form array where to add the form.
     * @param array $form_state
     *   The current form state.
     */
    public function form_extract_values($form, &$form_state) {
        parent::form_extract_values($form, $form_state);
        $form_values = RulesPluginUI::getFormStateValues($form, $form_state);
        if ($this->element instanceof RulesCondition && isset($form_values['negate'])) {
            $this->element
                ->negate($form_values['negate']);
        }
    }
    
    /**
     * @param array $form
     *   The form array where to add the form.
     * @param array $form_state
     *   The current form state.
     */
    public function form_validate($form, &$form_state) {
        parent::form_validate($form, $form_state);
        // Validate the edited element and throw validation errors if it fails.
        try {
            $this->element
                ->integrityCheck();
        } catch (RulesIntegrityException $e) {
            form_set_error(implode('][', $e->keys), $e->getMessage());
        }
    }

}