When I am integrating offsite payments in ActiveMerchant, I always need to provide an endpoint to receive payment notificaiton from gateway providers. After a couple of projects, I have come up with a best-practice to do it, and I thought this might be useful for others.
I have a PaymentNotification class solely to record notifications. This is because I want to decouple the persistence of notification from the order status change. If something goes wrong when I change Order, the notification will still be safely persisted in the database for later analysis.
As you can see, the controller action is pretty light. It only saves the notification. The notification request is setup so it contains order_id and payment method.
The interesting part is the PaymentNotification model. It has a few columns for persisting different information (mostly serialized). It is also linked to Order, for easier analysis.
process method is to check the notification's validity and trigger order status update. It is to be called separately (maybe via a scheduled job). A few kinds of custom exceptions may be raised during
process, because they are handled differently. Either way, errors will be recorded in the errors column.
Any improvement is welcomed :D