Facebook Intergration

Someone else may be able to point you at the perfect gem for this, but I can tell you that I've worked on a similar problem and it wasn't much work to roll our own, based on the oauth2 gem.

Here's a sketch of the code/flow I use.

1) User clicks on 'Connect to Facebook' and this sends you to an action like this

def to_facebook
    options = {
      :redirect_uri => facebook_callback_url,
      :scope => "email,publish_stream" # whatever you want to do
    }
    client = OAuth2::Client.new(FACEBOOK_API_KEY, FACEBOOK_API_SECRET, :site => FACEBOOK_API_SITE)

    redirect_to client.web_server.authorize_url(options)
end

2) User goes over to facebook and gives you all the access you want, then facebook calls the callback you specified facebook_callback_url which should take you to an action like this:

def facebook_callback
    client = OAuth2::Client.new(FACEBOOK_API_KEY, FACEBOOK_API_SECRET, :site => FACEBOOK_API_SITE)
    access_token = client.web_server.get_access_token(params[:code], :redirect_uri => facebook_callback_url)

    do_my_custom_user_association(access_token)
end

Then you can specify whatever you want in do_my_custom_user_association, you should have a current_user available from authlogic if someone is logged in, so you can redirect to a flow that lets the logged in user select if they want to merge into their current account or a different one. If there's no current user, you can send them to a create account flow, with some facebook data attached.

Note that this is just a sketch, there are error cases to handle (e.g. facebook_callback will be hit with the param error_reason if the get_acccess_token fails) and I'm not recommending you do all the oauth2 interaction right in your controller, but the basic idea is there.