class Callbacks

class Callbacks {
    use StringTranslationTrait;
    
    /**
     * Form element validation handler for 'name' in form_test_validate_form().
     */
    public function validateName(&$element, FormStateInterface $form_state) {
        $triggered = FALSE;
        if ($form_state->getValue('name') == 'element_validate') {
            // Alter the form element.
            $element['#value'] = '#value changed by #element_validate';
            // Alter the submitted value in $form_state.
            $form_state->setValueForElement($element, 'value changed by setValueForElement() in #element_validate');
            $triggered = TRUE;
        }
        if ($form_state->getValue('name') == 'element_validate_access') {
            $form_state->set('form_test_name', $form_state->getValue('name'));
            // Alter the form element.
            $element['#access'] = FALSE;
            $triggered = TRUE;
        }
        elseif ($form_state->has('form_test_name')) {
            // To simplify this test, just take over the element's value into $form_state.
            $form_state->setValueForElement($element, $form_state->get('form_test_name'));
            $triggered = TRUE;
        }
        if ($triggered) {
            // Output the element's value from $form_state.
            \Drupal::messenger()->addStatus($this->t('@label value: @value', [
                '@label' => $element['#title'],
                '@value' => $form_state->getValue('name'),
            ]));
            // Trigger a form validation error to see our changes.
            $form_state->setErrorByName('');
        }
    }
    
    /**
     * Create a header and options array. Helper function for callbacks.
     */
    public static function tableselectGetData() : array {
        $header = [
            'one' => t('One'),
            'two' => t('Two'),
            'three' => t('Three'),
            'four' => t('Four'),
        ];
        $options['row1'] = [
            'title' => [
                'data' => [
                    '#title' => t('row1'),
                ],
            ],
            'one' => 'row1col1',
            'two' => t('row1col2'),
            'three' => t('row1col3'),
            'four' => t('row1col4'),
        ];
        $options['row2'] = [
            'title' => [
                'data' => [
                    '#title' => t('row2'),
                ],
            ],
            'one' => 'row2col1',
            'two' => t('row2col2'),
            'three' => t('row2col3'),
            'four' => t('row2col4'),
        ];
        $options['row3'] = [
            'title' => [
                'data' => [
                    '#title' => t('row3'),
                ],
            ],
            'one' => 'row3col1',
            'two' => t('row3col2'),
            'three' => t('row3col3'),
            'four' => t('row3col4'),
        ];
        return [
            $header,
            $options,
        ];
    }
    
    /**
     * Submit callback that just lets the form rebuild.
     */
    public static function userRegisterFormRebuild(array $form, FormStateInterface $form_state) : void {
        \Drupal::messenger()->addStatus('Form rebuilt.');
        $form_state->setRebuild();
    }

}