Create own oAuth process in Codeigniter?

I am developing an API using Codeigniter and Phils RESTserver. I need to have authentication working with oAuth but I cannot find a library that works with both Codeigniter and MongoDB.

Is it simple to create the oAuth process myself? I know it is hard to answer not knowing my level of expertise.

This is my understanding of the oAuth process.

1. User clicks on link and are redirected to the servers login form.
2. User will be asked to authorize the developers app.
3. If he does authorize it he is redirected back to the developers website.
4. On this website the code that he got from step 3 will be exchanged for an access token.
5. Developers app will now be able to access the users account on the server.

I know there are parameters to be sent along with the requests like client_id and client_secret and redirect URL. But my question is. Is it this easy to implement an oAuth server? Just create th开发者_运维知识库e classes and functions? What else are the requirements to be able to call the process a true oAuth authentication?

Thankful for all input!

Have you had a play with this?

https://github.com/alexbilbie/CodeIgniter-OAuth-2.0-Server

Alex has also written a Mongo library, so if his server doesn't support Mongo out of the box then just have a play with that. Just because your API is in Mongo though doesn't mean the api keys, tokens, etc HAVE to be in Mongo too, but they easily can be.