Multi OmniAuth Provider

multiprovider.rb

class Identity < ActiveRecord::Base
  belongs_to :user
  validates_presence_of :uid, :provider
  validates_uniqueness_of :uid, :scope => :provider
 
  def self.find_for_oauth(auth)
    find_or_create_by(uid: auth.uid, provider: auth.provider)
  end
end

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :invitable, :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable, :omniauthable


  def self.find_for_oauth(auth, signed_in_resource = nil)

    # Get the identity and user if they exist
    identity = Identity.find_for_oauth(auth)

    # If a signed_in_resource is provided it always overrides the existing user
    # to prevent the identity being locked with accidentally created accounts.
    # Note that this may leave zombie accounts (with no associated identity) which
    # can be cleaned up at a later date.
    user = signed_in_resource ? signed_in_resource : identity.user

    # Create the user if needed
    if user.nil?

      # Get the existing user by email if the provider gives us a verified email.
      # If no verified email was provided we assign a temporary email and ask the
      # user to verify it on the next step via UsersController.finish_signup
      email_is_verified = auth.info.email && (auth.info.verified || auth.extra.raw_info.email_verified)
      email = auth.info.email
      user = User.where(:email => email).first if email

      # Create the user if it's a new registration
      if user.nil?
        user = User.new(
          name: auth.extra.raw_info.name,
          email: email ? email : "#{TEMP_EMAIL_PREFIX}-#{auth.uid}-#{auth.provider}.com",
          password: Devise.friendly_token[0,20],
          unconfirmed_email: email_is_verified ? nil : email
        )

        user.save!
      end
    end

end
 
class OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def self.provides_callback_for(provider)
    class_eval %Q{
      def #{provider}
        @user = User.find_for_oauth(env["omniauth.auth"], current_user)

        if @user.persisted?
          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
 
  [:twitter, :facebook, :google_oauth2].each do |provider|
    provides_callback_for provider
  end
 
  def after_sign_in_path_for(resource)
    if resource.email_verified?
      super resource
    else
      finish_signup_path(resource)
    end
  end
end

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