Gradual engagement, persistent guest user with Devise - ruby-on-rails

Question

I'm trying to set up gradual engagement in my utility app which people can use without registering e.g. notepad.cc and jsfiddle.net and I plan to create a guest user (with Devise) for the user when he 'writes' to the app.
I found this guide on the Devise wiki https://github.com/plataformatec/devise/wiki/How-To:-Create-a-guest-user which shows how to create a guest user for the duration of the browser session. What I want is for the user to continue using the same guest account in subsequent visits, until he signs up, maybe when I introduce subscription plans for more features.
How can I modify what's in the guide to make this possible?
Code in the guide linked above:
# file: app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
protect_from_forgery
# if user is logged in, return current_user, else return guest_user
def current_or_guest_user
if current_user
if session[:guest_user_id]
logging_in
guest_user.destroy
session[:guest_user_id] = nil
end
current_user
else
guest_user
end
end
# find guest_user object associated with the current session,
# creating one as needed
def guest_user
User.find(session[:guest_user_id].nil? ? session[:guest_user_id] = create_guest_user.id : session[:guest_user_id])
end
# called (once) when the user logs in, insert any code your application needs
# to hand off from guest_user to current_user.
def logging_in
end
private
def create_guest_user
u = User.create(:name => "guest", :email => "guest_#{Time.now.to_i}#{rand(99)}#email_address.com")
u.save(false)
u
end
end
And using it in the controller:
#thing.user = current_or_guest_user
#thing.save

Answer 1

After some yak-shaving I've managed to get it to work. Here's the working code:
class ApplicationController < ActionController::Base
protect_from_forgery
# if user is logged in, return current_user, else return guest_user
def current_or_guest_user
if current_user
if cookies[:uuid]
logging_in # Look at this method to see how handing over works
guest_user.destroy # Stuff have been handed over. Guest isn't needed anymore.
cookies.delete :uuid # The cookie is also irrelevant now
end
current_user
else
guest_user
end
end
# find guest_user object associated with the current session,
# creating one as needed
def guest_user
User.find_by_lazy_id(cookies[:uuid].nil? ? create_guest_user.lazy_id : cookies[:uuid])
end
# called (once) when the user logs in, insert any code your application needs
# to hand off from guest_user to current_user.
def logging_in
# What should be done here is take all that belongs to user with lazy_id matching current_user's uuid cookie... then associate them with current_user
end
private
def create_guest_user
uuid = rand(36**64).to_s(36)
temp_email = "guest_#{uuid}#email_address.com"
u = User.create(:email => temp_email, :lazy_id => uuid)
u.save(:validate => false)
cookies[:uuid] = { :value => uuid, :path => '/', :expires => 5.years.from_now }
u
end
end
I will accept another answer if you can show me a better way to do this.

Answer 2

The above solution works great.
Don't forget to setuphelper_method :current_or_guest_user to make the method accessible in views. Took me some time to figure out.