class OptionsHooks

class OptionsHooks {
    
    /**
     * Implements hook_help().
     */
    public function help($route_name, RouteMatchInterface $route_match) {
        switch ($route_name) {
            case 'help.page.options':
                $output = '';
                $output .= '<h2>' . t('About') . '</h2>';
                $output .= '<p>' . t('The Options module allows you to create fields where data values are selected from a fixed list of options. Usually these items are entered through a select list, checkboxes, or radio buttons. See the <a href=":field">Field module help</a> and the <a href=":field_ui">Field UI help</a> pages for general information on fields and how to create and manage them. For more information, see the <a href=":options_do">online documentation for the Options module</a>.', [
                    ':field' => Url::fromRoute('help.page', [
                        'name' => 'field',
                    ])->toString(),
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                    ':options_do' => 'https://www.drupal.org/documentation/modules/options',
                ]) . '</p>';
                $output .= '<h2>' . t('Uses') . '</h2>';
                $output .= '<dl>';
                $output .= '<dt>' . t('Managing and displaying list fields') . '</dt>';
                $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the list fields can be configured separately. See the <a href=":field_ui">Field UI help</a> for more information on how to manage fields and their display.', [
                    ':field_ui' => \Drupal::moduleHandler()->moduleExists('field_ui') ? Url::fromRoute('help.page', [
                        'name' => 'field_ui',
                    ])->toString() : '#',
                ]) . '</dd>';
                $output .= '<dt>' . t('Defining option keys and labels') . '</dt>';
                $output .= '<dd>' . t('When you define the list options you can define a key and a label for each option in the list. The label will be shown to the users while the key gets stored in the database.') . '</dd>';
                $output .= '<dt>' . t('Choosing list field type') . '</dt>';
                $output .= '<dd>' . t('There are three types of list fields, which store different types of data: <em>float</em>, <em>integer</em> or, <em>text</em>. The <em>float</em> type allows storing approximate decimal values. The <em>integer</em> type allows storing whole numbers, such as years (for example, 2012) or values (for example, 1, 2, 5, 305). The <em>text</em> list field type allows storing text values. No matter which type of list field you choose, you can define whatever labels you wish for data entry.') . '</dd>';
                $output .= '</dl>';
                return $output;
        }
    }
    
    /**
     * Implements hook_ENTITY_TYPE_update() for 'field_storage_config'.
     */
    public function fieldStorageConfigUpdate(FieldStorageConfigInterface $field_storage) {
        drupal_static_reset('options_allowed_values');
    }
    
    /**
     * Implements hook_ENTITY_TYPE_delete() for 'field_storage_config'.
     */
    public function fieldStorageConfigDelete(FieldStorageConfigInterface $field_storage) {
        drupal_static_reset('options_allowed_values');
    }
    
    /**
     * Implements hook_field_storage_config_update_forbid().
     */
    public function fieldStorageConfigUpdateForbid(FieldStorageConfigInterface $field_storage, FieldStorageConfigInterface $prior_field_storage) {
        if ($field_storage->getTypeProvider() == 'options' && $field_storage->hasData()) {
            // Forbid any update that removes allowed values with actual data.
            $allowed_values = $field_storage->getSetting('allowed_values');
            $prior_allowed_values = $prior_field_storage->getSetting('allowed_values');
            $lost_keys = array_keys(array_diff_key($prior_allowed_values, $allowed_values));
            if (_options_values_in_use($field_storage->getTargetEntityTypeId(), $field_storage->getName(), $lost_keys)) {
                throw new FieldStorageDefinitionUpdateForbiddenException("A list field '{$field_storage->getName()}' with existing data cannot have its keys changed.");
            }
        }
    }

}