class User < ApplicationRecord
 # Include default devise modules. Others available are:
 # :confirmable, :lockable, :timeoutable and :omniauthable
 devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :trackable, :validatable,
     :omniauthable, omniauth_providers: [:facebook]

      def self.from_omniauth(auth)
        where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
        user.email = auth.info.email
        user.provider = auth.provider
        user.uid = auth.uid
        user.password = Devise.friendly_token[0,20]
        end
      end
    end

config.omniauth :facebook, ENV['FACEBOOK_APP_ID'], ENV['FACEBOOK_APP_SECRET'],
      scope: 'email, public_profile', info_fields: 'email, first_name, last_name'

Rails.application.routes.draw do

      devise_for :users, controllers: {omniauth_callbacks: 'users/omniauth_callbacks' }

    authenticated :user do
        root 'home#index', as: 'authenticated_root'
      end

      devise_scope :user do
        root 'devise/sessions#new'
      end

    end

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController

      def facebook
        @user = User.from_omniauth(request.env["omniauth.auth"])
        sign_in_and_redirect @user
      end
    end