google_service.rb

require "errors"

class GoogleService
  private_class_method :new

  class << self

    def register(data_hash)
      data = AuthData.new(data_hash)
      auth = User::Google.find_by_uid(data.uid)
      if auth
        raise UserBlockedError if auth.user.blocked?
        return auth.user
      end

      if user = User.find_by_email(data.email)
        raise UserBlockedError if user.blocked?
      else
        user = UserGoogleRegistrationType.new
        user.password = SecureApp.generate_password
      end

      UserPopulator.via_google(user, data)
      user.active? ? user.save! : user.activate!

      user
    end

    def create_link(user, data_hash)
      data = AuthData.new(data_hash)
      auth = User::Google.find_by_uid(data.uid)

      raise AlreadyLinkedError if auth && auth.user == user

      if auth && auth.user != user
        raise UserBlockedError if auth.user.blocked?
        auth.destroy
        user.google.destroy if user.google
      end

      UserPopulator.via_google(user, data)
      user.save!
      true
    end
  end
end