A Simple Prepaid Card API

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Provides a REST API for common prepaid card operations, such as loading money onto a card and merchants authorizing payment. Built with Dropwizard. All data is stored in a PostgreSQL database.

You can play around with it on Heroku.

Getting Started

Build with Maven and then run pending database migrations. Ensure you have a PostgreSQL server running locally and a database named prepaidcard owned by a role named pg if you want the default settings to work. These details can be changed in config.yml.

$ mvn package
$ java -jar ./target/prepaid-card-1.0-SNAPSHOT.jar db migrate config.yml

You can then start the server!

$ java -jar ./target/prepaid-card-1.0-SNAPSHOT.jar server config.yml

Usage

The Goron Elder wishes to acquire a new card. He sends a POST request to /cards along the lines of:

{
  "name": "Goron Elder",
  "amount": 9999
}

During his visit to Clock Town, he stops by the Milk Bar and has some Chateau Romani for 199.95 (he gets a discount, being an elder and all). Mr. Barten sends the following POST request:

{
  "card": 1,
  "merchant": 1,
  "remaining": 199.95,
  "captured": 0
}

The Goron Elder wants to check his balance. He can do so by sending a GET request to his card ID. He should see something like:

{
  "id": 1,
  "balance": 9799.05,
  "blocked": 199.95,
  "name": "Goron Elder"
}

Mr. Barten can later capture this money by sending a PUT request to the transaction ID /cards/1/transactions/1:

{
  "amount": 199.95,
  "type": "capture"
}

If Mr. Barten gets greedy and tries to capture too much, the law will step in:

{
  "code": 400,
  "message": "Insufficient authorized amount remaining, £200.00 requested but £199.95 available"
}

Clock Town started using GBP only recently.

After a few more visits, the Goron Elder may wish to view his recent transactions. He can check his statement by sending a GET request to /statements with his card ID.

[
  {
    "merchant": "Clock Town Milk Bar",
    "amount": 199.95,
    "timestamp": 1489354320000
  },
  {
    "merchant": "Clock Town Milk Bar",
    "amount": 199.95,
    "timestamp": 1489354916000
  }
  {
    "merchant": "Clock Town Milk Bar",
    "amount": 199.95,
    "timestamp": 1489355129000
  }
  {
    "merchant": "Clock Town Milk Bar",
    "amount": 199.95,
    "timestamp": 1489355784000
  }
]

He sure is a big fan!

Future Improvements

• Actually transferring the money to the merchants