foxml.module

<?php

/**
 * @file
 * General hook implementations.
 */

/**
 * Implements hook_file_download().
 */
function foxml_file_download(string $uri) {
  /** @var \Drupal\Core\StreamWrapper\StreamWrapperManagerInterface $stream_wrapper_manager */
  $stream_wrapper_manager = \Drupal::service('stream_wrapper_manager');
  $scheme = $stream_wrapper_manager->getScheme($uri);
  if (!in_array($scheme, ['foxml', 'foxml.substream'])) {
    return NULL;
  }

  /** @var \Drupal\file\FileRepositoryInterface $file_repository */
  $file_repository = \Drupal::service('file.repository');
  $file = $file_repository->loadByUri($uri);

  if (!$file) {
    // Failed to load file entity, only grant access if the lower-level
    // permission is present.
    $user = \Drupal::currentUser();
    return $user->hasPermission('access referenced foxml') ?
      [
        'Cache-Control' => 'private',
      ] :
      -1;
  }
  else {
    $file_name = $file->getFileName();

    return [
      'Content-Disposition' => 'attachment; filename="' . $file_name . '"',
    ];
  }
}