Facebook - Twitter authentication - information merge - facebook

Question

I'm building a service which can be used anonymously, however the user has the ability to share content on his\her Facebook and\or Twitter profiles. Upon authorizing the applications I wish to store basic information about the users and link it to the content they are sharing.
Usually services require authentication prior to usage, which solves this problem, however in my case authentication comes at the very last stage and it's split into 4 paths:
[Facebook + Twitter]
[Facebook alone]
[Twitter alone]
[Nothing]
However doing the above will create redundant data in the database i.e. I will have the Facebook information and Twitter information in separate tables with no linkage between them and no relation to the post.
What's the best approach to prevent this? The solution is on the data modeling level? Or on the code level? Or both?
Has this been done before?
I have created a flow chart of how the merging of account data can be done, however this process might create overhead on the database level as it will require searching for entries using the very long FacebookID \ TwitterID.
If extra information is required please state it in a comment.
Thank you

Answer 1

The way I would handle this is to separate the concept of user identity from the concept of authentication used by your application. For example, at the data model level, have Users table store basic user information and have Authentications table that stores user credentials/tokens associated with a particular Authentication Provider.
At the code level, if you are planning to stick with third-party authentication, I would recommend looking into building a layer that can shield your application from having to deal directly with various OAuth providers.
In Ruby/Rails world, this is accomplished by a combination of Devise that manages user identities (it also allows to have built-in username/password authentication, but it does not sound like you are interested in that) and OmniAuth that delivers authentication against multiple providers.
An example application incorporating both is available here: Devise + OmniAuth.
Finally, RailsCast on the subject is here: OmniAuth Part 1
I realize that you may not be working in Ruby/Rails, but these materials may provide you with inspiration for the architecture you are trying to achieve.