Payment Gateway Golang Example

In our simplified model of a prepaid card the card holds a balance in GBP and users can make transactions in GBP. To be able to use the card the user must first load some money onto the card. This increases the available balance on the card. When a user goes and makes a transaction using the card, the merchant (e.g your local independent coffee shop) sends the card an Authorization request to check if the user loaded enough money on the account to pay for their coffee.

If the user has loaded enough, the Authorization request is approved and the amount the merchant requested is earmarked (or blocked). The merchant at a later point in the future can decide to Capture ​the transaction at which point we send the merchant the money. At any point the user should be able to see how much he loaded onto the card, the current available balance, and the current amount that is blocked on there (waiting to be captured).

The merchant can decide to only capture part of the amount or capture the amount multiple times. In this model, the merchant can’t capture more than we initially authorized him to. The merchant can decide to reverse the whole or part of the initial Authorization at which point they can no longer capture the full amount (only the amount that is still authorized). The merchant can Refund ​the user after they capture the funds. They can’t refund the user more than they captured. The user can then use the refunded amount to buy more coffee.

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Prerequisites

What things you need to install the software and how to install them

https://golang.org/doc/install

Installing

A step by step series of examples that tell you how to get a development env running

Download the GO Project

https://github.com/angelospillos/gateway.git

Place the gateway folder in the MAIN GoPath src to look like

go/src/gateway/main.go

Then use the following command to run it

go run *.go

Running the tests

Do to time constrains there are no automated tests for this system but you can use the following endpoints to test the system

Accounts Create

It will generate a random Account.

Endpoint

GET http://127.0.0.1:8000/v1/accounts/create

Response

{
    "id": "4666336021280850",
    "available": 0,
    "blocked": 0,
    "deposited": 0,
    "withdrawn": 0,
    "currency": "GBP",
    "card_name": "Mr Payment",
    "card_type": "VISA",
    "card_number": 4666336021280850,
    "card_expiry_month": 2,
    "card_expiry_year": 23,
    "card_security_code": 547,
    "statement": null,
    "creation_time": "2018-07-02T00:31:04.673878069+03:00"
}

Accounts Deposit

Use the the Id of an Account to deposit.

Request

 {
 	"id" : "4666336021280850",
 	"amount":1000
 }

Endpoint

POST http://127.0.0.1:8000/v1/accounts/deposit

Response

{
    "account_id": "4666336021280850",
    "status": "0",
    "description": "Approved"
}

Accounts Detail

Details of the Current Account

Request

{
	"id" : "4666677990633308"
}

Endpoint

http://127.0.0.1:8000/v1/accounts/detail

Response

{
    "id": "",
    "available": 0,
    "blocked": 0,
    "deposited": 0,
    "withdrawn": 0,
    "currency": "",
    "card_name": "",
    "card_type": "",
    "card_number": 0,
    "card_expiry_month": 0,
    "card_expiry_year": 0,
    "card_security_code": 0,
    "statement": null,
    "creation_time": "0001-01-01T00:00:00Z"
}

Accounts Statement

A list of all payments involved with the current Account

Request

{
	"id" : "4666744292130045"
}

Endpoint

http://127.0.0.1:8000/v1/accounts/statement

Response

{
    "statement": [{}]
}

Payments Authorization

Authorization is the first point of entry to start working with payment operations. Once an authorization is successful you can execute successive operations.

Headers

From 4666557263649072
Content-Type application/json

Request

{
	"orderId" : "123",
	"amount":900,
	"currency":"GBP",
	"card_name":"Mr Payment",
	"card_number":4666677990633308,
	"card_expiry_month": 10,
	"card_expiry_year" : 19,
	"card_security_code" : 916
}

Endpoint

POST http://127.0.0.1:8000/v1/payments/authorization

Response

{
    "referenceId": "9da2df89-f0e4-406d-ac0d-d7670607e306",
    "status": "0",
    "description": "Approved"
}

Successive Requests

Headers

From 4666557263649072 // Account Id to get the money
Content-Type application/json

Example Request

{
	"orderId" : "123",
	"amount":50
}

Endpoint

http://127.0.0.1:8000/v1/payments/capture/{authorization_id}
http://127.0.0.1:8000/v1/payments/reversal/{authorization_id}
http://127.0.0.1:8000/v1/payments/refund/{capture_id}

Example Response

{
    "referenceId": "ee1a3371-1781-4de9-bf7c-f72394c811ba",
    "status": "0",
    "description": "Approved"
}

Deployment

To Deploy this on a live system follow http://www.blog.labouardy.com/deploying-go-app-to-aws-ec2/

Built With

• Golang - The Go Programming Language.
• MUX - A powerful URL router and dispatcher for golang.
• BoltDb - An embedded key/value database for Go.

Versioning

For the versions available, see the tags on this repository.

Authors

• Angelos Pillos - (https://www.angelospillos.com)

See also the list of contributors who participated in this project.

License

This project is licensed under the GNU Affero General Public License v3.0 - see the LICENSE.md file for details

Acknowledgments

• Special thanks for the inspiration to Curve (https://www.imaginecurve.com/)