How to rename a collection of uploaded files?

[cbaconnier]

I did a question on stackoverflow at first. But I'm still not getting any answer. That's why I'm asking here.

I would like to rename a collection of uploaded files, but when I use addAllMediaFromRequest() I can't retrieve information from the files.

In this example; I need to know the file extension in order to rename the file.

$files = $post->addAllMediaFromRequest();

$files->each(function (FileAdder $file) {
    $file->usingFileName(Str::random(16) . '.jpg')  // What if it's a png?
         ->toMediaCollection();
});