A micro-blogging site like Twitter

I am looking to build a micro-blogging website. users must be able to register a unique user name in any language (even if not English), they can also log in with their any of their Social accounts (Ggl/FB/ or TWT) You can modify an existing script or write your own, I just want to make sure its fully documented for future enhancements. User should be able to add images and/or videos and/or documents to their posts. The Admin can limit the number of letters that is allowed, Admin is also able to limit the filesize to be uploaded. Users can follow users, and comment on other user posts.