class OptionsAllowedValues

class OptionsAllowedValues {
    
    /**
     * Implements callback_allowed_values_function().
     *
     * @see options_allowed_values()
     */
    public static function simpleValues(FieldStorageDefinitionInterface $definition, ?FieldableEntityInterface $entity = NULL) : array {
        return [
            'Group 1' => [
                0 => 'Zero',
            ],
            1 => 'One',
            'Group 2' => [
                2 => 'Some <script>dangerous</script> & unescaped <strong>markup</strong>',
            ],
            'More <script>dangerous</script> markup' => [
                3 => 'Three',
            ],
        ];
    }
    
    /**
     * Implements callback_allowed_values_function().
     *
     * @todo This function violates the recommendation in options_allowed_values()
     *   to return a list of all possible values in any context when $items is
     *   NULL. Since this is not yet used for testing Views integration, that is
     *   alright for now. Fix this in https://www.drupal.org/node/2012130.
     *
     * @see options_allowed_values()
     */
    public static function dynamicValues(FieldStorageDefinitionInterface $definition, ?FieldableEntityInterface $entity = NULL, &$cacheable = NULL) : array {
        $values = [];
        if (isset($entity)) {
            $cacheable = FALSE;
            $values = [
                $entity->label(),
                $entity->toUrl()
                    ->toString(),
                $entity->uuid(),
                $entity->bundle(),
            ];
        }
        // We need the values of the entity as keys.
        return array_combine($values, $values);
    }

}