merge existing account when fb login

user.rb

def self.find_for_facebook_oauth(auth, signed_in_resource=nil)
  user = User.where(:provider => auth.provider, :uid => auth.uid).first
  if user
    return user
  else
    registered_user = User.where(:email => auth.info.email).first
    if registered_user
      registered_user.update_attributes(:provider => auth.provider, :uid => auth.uid, picture: (URI.parse(auth.info.image.split("?")[0] << "?width=200&height=200") if auth.info.image?) )
      return registered_user
    else
      user = User.create( name:auth.extra.raw_info.name,
                          provider:auth.provider,
                          uid:auth.uid,
                          email:auth.info.email,
                          password:Devise.friendly_token[0,20],
                          picture: (URI.parse(auth.info.image.split("?")[0] << "?width=200&height=200") if auth.info.image?)
                        )
    end
  end
end