public function stateId(array $values)
    {
        $count = count($values);
        $ids = array_filter($values, 'ctype_digit');

        if ($count != count($ids)) {
            return $this->translation->text('@field has invalid value', array(
                '@field' => $this->translation->text('Condition')));
        }

        $existing = array_filter($values, function ($state_id) {
            $state = $this->state->get($state_id);
            return isset($state['state_id']);
        });

        if ($count != count($existing)) {
            return $this->translation->text('@name is unavailable', array(
                '@name' => $this->translation->text('Country state')));
        }

        return true;
    }