Changing file name on upload

Question

I'm trying to automatically add prefixes to uploaded file names so they can later be processed by non-drupal scripts. I want to do that while the user is uploading files during creation/editing of a node.

To do that I am using hook_file_validate($field) where I check if the file is correct and then using $field->destination I define a new file name.

Surprisingly my issue lies in getting context to generate the proper file name (nid of the node,nid of the parent group, or info from other fields). When I upload a file, only part of the website is reloaded by javascript and hook_file_validate is triggered before hook_form_alter . Whene it is triggered I have no access to any data that would tell me where am I.

So far I have tried:

$_REQUEST['destination']

while defined (not a typo) when the whole form is loaded, it is undefined when the file field of the form is reloaded

$_GET['nid']

again - undefined

arg(0); arg(1); arg(2);

returns file ajax field_quest_file which is not very usefull

I can access uid but it is not enough for me to create unique file names.

Answer 1

Following on from my comment suggesting you do this in an additional submit handler something like this should work:

Add the new submit handler:

function misc_form_alter(&$form, &$form_state, $form_id) {
  if($form_id == 'YOUR_CONTENT_TYPE_node_form') {
    $form['actions']['submit']['#submit'][] = 'rename_files';
  }
}

And then in the new submit handler:

function rename_files($form, &$form_state) {

  $node = $form_state['node'];

  global $user;

  // Loop over the uploaded files. Be sure to re-name field_files to the name of 
  // your file field.
  foreach($node->field_files[LANGUAGE_NONE] as $item) {

    // Load the file object
    $file = file_load($item['fid']);

    // To set the destination first remove the filename from the stream wrapper 
    // URI.
    $destination = str_replace($file->filename, '', $file->uri);

    // Modify this line to the name of your group field.
    $group = $node->field_group[LANGUAGE_NONE][0]['value'];

    // And then append the group, uid and put the filename back on the end.
    $destination .= $group.$user->uid.$file->filename;

    // And finally rename the file.
    file_move($file, $destination);
  }

}

Answer 2

Instead of renaming the files I used a different approach and change their destination folder.

I do it from the level of hook_form_alter where I have full access to POST/GET arguments and the values in other fields of the form.

function myModule_form_alter(&$form,&$form_state,$form_id){
    switch($form_id){
        case 'nodetype_node_form':
            //prepare whatever prefix you want
            //in my case gid/uid/
            $dest_folder = _make_destination_folder($form);
            //findout which file will be added next
            //the form is rebuild each time a file is uploaded
            $delta = form['field_files'][LANGUAGE_NONE]['#file_upload_delta'];
            //instead of renaming files just change the destination folder
            form['field_files'][LANGUAGE_NONE][$delta]['#upload_location'] = 'private://'.$dest_folder;
            break;
    }
}

This way files end up in an unique, non random and predictable place before the node is even saved. A bonus of this approach is that I will have the files sorted in folders based on group and user