Lets explore the Payments app architecture in detail. Our code is available at Github.
- Payment Flow
- Refund Flow
- Auth Flow
The Payment Flow is broken up into three phases.
Phase One - Shopify notifies the payment's app backend of a payment that needs to be made. We will respond with a url that the customer can checkout from.
Phase Two - The customer requests a payment transaction from the backend.
Phase Three - We discover a completed transaction, notify Shopify it's been completed, and send the customer back to Shopify.
The Refund Flow is broken up into three phases.
Phase One - The merchant initates a refund for a customer. Shopify notifies us of the refund that needs to be proccessed.
Phase Two - The merchant starts the process of completing a pending refund on our merchant-ui.
Phase Three - We discover a completed transaction. Figure out what refund it's for and notify Shopify it's been completed.
Concepts We Use
Single Use Accounts
A Single Use Account is an account with 0 data that we add on to transactions. They serve as a solution to a few problems we face when building on chain payment that integrate with web2 commerce platforms. You can view the instruction that handles this here.
Indexing Refrence Keys
We add refrence keys onto transactions for look ups later. Small data < 32 bytes can be made into a public key that only serves as a way to look up the transaction later. We can create keys for things like merchants, payments, and refunds. This will serve as a way to determinstically find transactions if we run into database issues. You can view the instruction that handles this here.