Project attachments (file uploads) with custom folder structure

Hey everyone,

I would like to have the option to upload files to the project and have them uploaded in a predefined folder structure. So the user can choose when uploading a file to which folder (within that project) it belongs.

For example lets say we have project A and project B. And each of those two projects have folders offers, bills, foto, notes
I would like to be able to upload file to project A and say … aha, this file is an offer, so it should go to offers folder (of project A).
And then when i want to list all the offers (uploaded files from this directory) they would all be collected in one place.
Since at the moment uploading of files just to a project can get hella messy with many files.

What would be the best way to tackle this? Is there already some existing module i could start with or any other useful info would be appeciated.

Cheers!