Another file API conception

Some people suggested that every module should handle files by itself. I am for a central storage of file information, though. This has several advantages such as being able to get a quick overview on all files, re-use files elsewhere and so on.

My suggestions include:

• A single file handling mechanism
• Multiple versions of one file (e.g. different resolutions, formats) and a hook that lets modules handle those versions
• Revisions of one file (and if a file is changed, the above mentioned hook is fired that lets modules generate new versions from the file)
• upload.module:
  • File uploading is changed to a file selection where you can select any of the available files or choose to upload a new one.
  • The file browsing widget allows users to search for files
  • Files (not file versions!) are attached to a node; modules can handle it how they want to (generate a slideshow, use them for inline pictures, provide different audio formats, different video formats, etc.)
• Tables: files, file_revisions, file_versions and node_file for the mapping, term_file for taxonomies
• node_file has a weight column so that file uploads can be rearranged
• Provide a single location where you can manage all files, see to which nodes it's attached to and so on
• Provide a function that lets other modules query the database for specific files (mime types, versions and so on)
• Some features for the interaction with views.module
• Let the user select where to store the data by using 'protocol handlers'. That means, the user can select if he wants to store it locally in a folder, transfer the files via ftp to another (file) server, use WebServices to store them and so on.

Example for the interaction between (a made up) image module and the files API:

• User uploads file, file gets saved somewhere
• hook_file_handle is fired, image.module checks if the file is an image and creates a new file version (thumbnail) with a different size
• Modules can now rely on the fact that there is a thumbnail for each image and display that everywhere they want to
• image.module can also check if there are more file versions (e.g. with different sizes) and generate those as well
• If the file is changed (either in administer --> files or on the node's form), meaning a new revision is created, the hook is called again and the module can create a new thumbnail

Example for the interaction of img_assist.module with this system:

• Users can upload or select files to attach to the node right on the editing form
• Now they can insert the image with the right dimensions. If the user specifies any other dimension, the image is recalculated, a new file version is created

I'd love to hear some feedback on my conceptions.