oAuth

Here is the scenario, Need to use Facebook oAuth login for users to register or login. Then after that user has been verified and logged in this also need to authenticate my own rest api. Is this possible with your plugin?

The OAuth client just grants you an authorization to access the Facebook (or other) API with the user permission.

What you can do is to use the class so you can call Facebook API to get his name and email address. That should be a starting point for you to create user records in your system, eventually asking him for a password.

Later you can let the user authenticate with his Facebook account using this OAuth class or let him login with his username or email and password.

If you take a look at the PHP Classes login system, it already works like that.

Take a look at the Facebook examples with this class to see how you can get the authorization to call Facebook API and get the user account details like name and email.