Payment Flows

Transacting via Centrapay requires customer and merchant devices to negotiate the creation and fulfillment of Payment Requests. There are multiple payment “flows” a merchant integration can select from to facilitate this negotiation. Which flow is employed will depend on the capabilities of the merchant system.

Merchant-presented

When a merchant terminal has a customer-facing display it can prompt the customer to pay by showing a QR code.

Dynamic Merchant QR Code

1. Merchant terminal  creates a payment request  via Centrapay API and shows QR code on customer-facing display.
2. Customer device scans the QR code, fetches the  payment request details , and  completes payment  as normal.
3. Merchant terminal displays transaction result using the  payment request details .

Static Merchant QR Code

When a merchant terminal is neither capable of displaying nor scanning QR codes or barcodes, such as for unattended vending machines, then a static QR code can be used.

1. Customer scans QR code and initiates vending sequence via Centrapay API, with the merchant code as a parameter.
2. Merchant vending system initiates payment request via Centrapay API.
3. Customer device fetches payment request and completes payment as normal.
4. Merchant vending system optionally initiates refund via Centrapay API.

Patron-presented

When a merchant terminal is not capable of displaying a customer-facing QR code, then the payment request can be negotiated with the customer by scanning a barcode or QR code displayed on the customer’s smart device.

Dynamic Patron Barcode

1. Customer generates a short-lived  Patron Code  via Centrapay API and displays it as a barcode on their smart device
2. Merchant scans the barcode, optionally checks for support using the  Scanned Codes  endpoints for additional information on the patron, and then  creates a Payment Request  via Centrapay API with the barcode as a parameter.
3. Customer device  fetches the payment request  created with the Patron Code and completes payment as normal.

Static Patron Barcode

This is a variant on Dynamic Patron Code. If you’ve setup a long lived Centrapay Enabled Barcode then you can use these to pay on behalf of a Customer. You may need to check a Customer’s Photo ID before this goes through.

1. Customer presents a Centrapay Enabled Barcode and it is scanned by the Merchant.
2. Merchant checks the barcode for support using the  Scanned Codes  endpoints.
3. Merchant then  creates a Payment Request  using the barcode as a parameter.
4. Merchant  polls for the Payment Request  created with the barcode checking the status.
5. Merchant will have to call endpoints to  accept a Payment Condition  if there are  Payment Conditions  on the Payment Request and the condition has an awaiting-merchant status.
6. Once the status on the Payment Request is “paid” then the process is complete.

    sequenceDiagram
	participant C as Card Holder
	participant T as Terminal
	participant CP as Centrapay
	note over C: Present Barcode
	T->>C: Scan Barcode<br>(Card Number)
	T->>CP:POST /api/decode<br>{ code, scannedBy, merchantConfigId }<br> Check Barcode
	note over T: Calculate Discount
	T->>CP:POST /api/payment-requests<br>{ barcode, barcodeType, amount, lineItems }<br> Create Payment Request
	T->>CP:GET /api/payment-requests/{id}<br> Poll for status
	opt Check ID Condition
		T->>C: Check Id
		T->>CP:POST /api/payment-requests/{id}/conditions{n}/accept<br> Accept Condition
	end
	T->>CP:GET /api/payment-requests/{id}<br> Poll for status
	note over T: Display Confirmation
  

Quick Pay

Quick Pay is used to pay the payment request after it is polled for the first time, without requiring patron approval. Quick Pay can only be triggered using the patron-presented flows, and the patron barcode must be linked to an asset type that allows quick pay.

See  Asset Types  for the list of asset types that support Quick Pay.