/**
* Wrapper for file_get_file_references().
*
* @param \Drupal\file\FileInterface $file
* The file object for which to get references.
*
* @return array
* A multidimensional array. The keys are field_name, entity_type,
* entity_id and the value is an entity referencing this file.
*
* @see file_get_file_references()
*/
protected function getFileReferences(FileInterface $file)
{
return file_get_file_references($file, NULL, EntityStorageInterface::FIELD_LOAD_REVISION, NULL);
}
/**
* Define access control for the preview page.
*
* Deny users access to the preview page unless they have permission to edit
* an entity (any entity) that references the current image being previewed or
* if they've provide a valid token as a query string. The later is needed so
* preview will work when creating a new entity that has not yet been saved.
*
* @param \Drupal\Core\Session\AccountInterface $account
* The current user.
* @param int $fid
* The file id for the image being previewed from the URL.
*
* @return AccessResult
* An AccessResult object defining if permission is granted or not.
*/
public function access(AccountInterface $account, $fid) {
$access = AccessResult::forbidden();
// @todo: I should be able to use "magic args" to load the file directly.
$file = File::load($fid);
$image = \Drupal::service('image.factory')->get($file->getFileUri());
if (!$image->isValid()) {
throw new InvalidArgumentException('The file with id = $fid is not an image.');
}
// Check if there was a valid token provided in with the HTTP request so
// that preview is available on a "create entity" form.
if ($this->validTokenProvided()) {
$access = AccessResult::allowed();;
}
// If access has not yet been granted and the file module is enabled, check
// if there is an entity that references this file which the current user
// has access to edit.
if (function_exists('file_get_file_references') && !$access->isAllowed()) {
$references = file_get_file_references($file, NULL, EntityStorageInterface::FIELD_LOAD_REVISION, '');
foreach ($references as $field_name => $data) {
foreach (array_keys($data) as $entity_type_id) {
if ($account->hasPermission($entity_type_id . ".edit")) {
$access = AccessResult::allowed();
break;
}
}
}
}
return $access;
}