public function file($server = '', $download = true)
    {
        $field = $this;

        return $this->unescape()->as(function ($path) use ($server, $download, $field) {
            $name = basename($path);

            $field->border = false;

            $size = $url = '';

            if (url()->isValidUrl($path)) {
                $url = $path;
            } elseif ($server) {
                $url = $server.$path;
            } else {
                $storage = Storage::disk(config('admin.upload.disk'));
                if ($storage->exists($path)) {
                    $url = $storage->url($path);
                    $size = ($storage->size($path) / 1000).'KB';
                }
            }

            if (!$url) {
                return '';
            }

            return <<<HTML
<ul class="mailbox-attachments clearfix">
    <li style="margin-bottom: 0;">
      <span class="mailbox-attachment-icon"><i class="fa {$field->getFileIcon($name)}"></i></span>
      <div class="mailbox-attachment-info">
        <div class="mailbox-attachment-name">
            <i class="fa fa-paperclip"></i> {$name}
            </div>
            <span class="mailbox-attachment-size">
              {$size}&nbsp;
              <a href="{$url}" class="btn btn-default btn-xs pull-right" target="_blank"><i class="fa fa-cloud-download"></i></a>
            </span>
      </div>
    </li>
  </ul>
HTML;
        });
    }