gistfile1.rb

Rails.configuration.middleware.use Warden::Manager do |config|
  config.failure_app = SessionsController
  config.default_strategies :facebook
end

Warden::Manager.serialize_into_session do |user|
  user.id.to_s
end

Warden::Manager.serialize_from_session do |id|
  User.first( :conditions => { :id => id } )
end

Warden::Manager.before_failure do |env, opts|
  request = env[ "action_controller.rescue.request" ] ||= ActionController::Request.new( env )
  env[ 'action_dispatch.request.path_parameters' ][ :action ] = "unauthenticated"
end

Warden::Strategies.add :facebook do
  def valid?
    request.cookies && request.cookies[ "fb_access_token" ]
  end

  def authenticate!
    u = User.first :conditions => { :fb_access_token => request.cookies[ "fb_access_token" ] }
    u.nil? ? fail! : success!( u )
  end
end