Design a service like Dropbox or Google Drive

Design a service with the following functional requirements

1. Users should be able to upload and download files

2. The files should be able to be shared with other users

3. Changes to the files should be pushed to other users with the content on their machine

4. There must be no risk of file corruption

5. Keep track of different versions of the files so they may be rolled back

6. Users should be able to edit files without an internet connection and the changes sync up when a connection becomes available