Happy_seed omniauth with devise

form_user.rb

class FormUser < User
  attr_accessor :current_password

  validates_presence_of     :email, if: :email_required?
  validates_uniqueness_of   :email, allow_blank: true, if: :email_changed?
  validates_format_of       :email, with: Devise.email_regexp, allow_blank: true, if: :email_changed?

  validates_presence_of     :password, if: :password_required?
  validates_confirmation_of :password, if: :password_required?
  validates_length_of       :password, within: Devise.password_length, allow_blank: true


  def password_required?
    return false if email.blank?
    !persisted? || !password.nil? || !password_confirmation.nil?
  end

  def email_required?
    true
  end
end

identity.rb

class Identity < ActiveRecord::Base
  belongs_to :user
  
  validates_presence_of     :uid, :provider
  validates_uniqueness_of   :uid, :scope => :provider
  validates_uniqueness_of   :handler



  def self.find_for_oauth(auth)
    identity = find_by(provider: auth.provider, uid: auth.uid)
    unless auth.info.email.nil?
      identity = create(uid: auth.uid, provider: auth.provider) if identity.nil?
      identity.oauth_token  = auth.credentials.token
      identity.oauth_expires_at = Time.at(auth.credentials.expires_at)
      identity.name = auth.info.name
      identity.email = auth.info.email    
      #identity.handler = auth.extra.raw_info.first_name.downcase
      identity.image = auth.info.image
      identity.age = Identity.year - Date.strptime(auth.extra.raw_info.birthday,'%m/%d/%Y').year.to_i
      identity.birth_day = auth.extra.raw_info.birthday
      identity.save
      identity
    end
  end



  private
  def self.year
    Date.today.year.to_i
  end


end

omniauth_callbacks_controller.rb

class OmniauthCallbacksController < Devise::OmniauthCallbacksController  
  def facebook
    generic_callback('facebook')
  end

  # Other providers goes here.
  #
  # def twitter
  #   generic_callback('twitter')
  # end

  def generic_callback(provider)
    @identity = Identity.find_for_oauth env["omniauth.auth"]
    @user = @identity.user || current_user
    
    if @user.nil?
      @user = User.create(email: @identity.email || "")
      @identity.update_attribute(:user_id, @user.id)
    end
    
    if @user.email.blank? && @identity.email
      @user.update_attribute(:email, @identity.email)
    end
    
    if @user.persisted?
      @identity.update_attribute(:user_id, @user.id)
      @user = FormUser.find(@user.id)
      session[:user_id] = @user.id
      sign_in_and_redirect @user, event: :authentication
      set_flash_message(:notice, :success, kind: provider.capitalize) if is_navigational_format?
    else
      session["devise.#{provider}_data"] = env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

registrations_controller.rb

class RegistrationsController < Devise::RegistrationsController
  def update_resource(resource, params)
    if resource.encrypted_password.blank? # || params[:password].blank?
      resource.email = params[:email] if params[:email]
      if !params[:password].blank? && params[:password] == params[:password_confirmation]
        logger.info "updating password"
        resource.password = params[:password]
        resource.save
      end
      if resource.valid?
        resource.update_without_password(params)
      end
    else
      resource.update_with_password(params)
    end
  end


  def destroy
    @user = current_user
    @identity = @user.identity
    if @identity.destroy && @user.destroy 
        redirect_to root_url, notice: "User deleted :("
    end
  end
end

routes.rb

Rails.application.routes.draw do
  devise_for :users, class_name: 'FormUser', :controllers => { omniauth_callbacks: "omniauth_callbacks", registrations: "registrations"} 
  

  root to: 'home#index'
end

user.rb

class User < ActiveRecord::Base
  devise :omniauthable, :database_authenticatable,
      :recoverable, :rememberable, :trackable

  # Change to (has_many :identities) for adding multible providers.
  has_one :identity



  def facebook
    identities.where(:provider => "facebook").first
  end
  def facebook_client
    @facebook_client ||= Facebook.client(access_token: facebook.access_token)
  end
end