protected function getDefaultAddressOption($type, array $options) {
    $default_option = NULL;

    // Check if any address is a default for this type.
    foreach ($options as $option_id => $option) {
      $key = "default-{$type}";
      if (isset($option[$key]) && $option[$key]) {
        $default_option = $option_id;
        break;
      }
    }

    // Fallback to the first option.
    if (!$default_option || !isset($options[$default_option])) {
      $option_ids = array_keys($options);
      $default_option = reset($option_ids);
    }

    return $default_option;
  }