Rails + Devise + Facebook Login API + iOS Facebook SDK | Controller

omniauth_controller.rb

class Api::V1::OmniauthController < ApplicationController
  skip_before_filter :verify_authenticity_token, :if => Proc.new { |c| c.request.format == 'application/json' }
  before_filter :authenticate_user!, :except => [:create, :failure]

  def new
  end

  def create
    params[:access_token] = decrypt(params[:access_token])
    auth_access_token =  params[:access_token]

    @graph = Koala::Facebook::API.new(auth_access_token, ENV['FB_APP_SECRET'])
    profile = @graph.get_object('me')

    @auth = Authentication.find_by_provider_and_uid(params[:provider], profile['id'])

    if @auth

      user = User.find_for_database_authentication :email => profile['email']
      return invalid_login_attempt unless user

      sign_in(:user, user)
      render :status => 200,
             :json => { :success => true,
                        :info => "You've logged in.",
                        :data => { :user_email => encrypt(user.email),
                                   :auth_token => encrypt(user.authentication_token) } }
    else

      user = User.find_for_database_authentication :email => profile['email']

      unless user
        user = User.new :email => profile['email']
        user.generate_password!
      end

      user.authentications.build :provider => params[:provider], :uid => profile['id']
      user.save

      sign_in(:user, user)

      render :status => 200,
             :json => { :success => true,
                        :info => "You've signed up.",
                        :data => { :user_email => encrypt(user.email.to_s),
                                   :auth_token => encrypt(user.authentication_token.to_s) } }
    end

  end

  protected

  def invalid_login_attempt
    render :status => 401,
           :json   => { :success => false,
                        :message => 'Error with your login or password'}

  end

  def failure
    render :status => 401,
           :json   => { :success => false,
                        :info => 'Login Failed',
                        :data => {} }
  end

end