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This repository contains the implementation of a transaction commission calculation task. See the task description below.

Previous iteration with NestJS and TypeScript: https://github.com/LinkPovilas/backend-nest-k-task

Copy .env.example and rename to .env file. For currency exchange API your need to get an API key from https://exchangerate.host/.

For convenience database is seeded with test data.

./api-test/ dir contains HTTP request example

$ docker-compose up -d
$ go run .

# run all tests within the entire code base
$ go test ./...

Create a RESTful API with an endpoint for transaction commission calculation. The API must use JSON format for requests and responses.

Request (Transaction) examples

1st example

{
  "date": "2021-01-01",
  "amount": "100.00",
  "currency": "EUR",
  "client_id": 42
}

2nd example

{
  "date": "2021-01-01",
  "amount": "200.40",
  "currency": "USD",
  "client_id": 42
}

Response (Commission) example

{
  "amount": "0.05",
  "currency": "EUR"
}

Commission response must always be in Euros. Please use a currency rates API (https://api.exchangerate.host/2021-01-01) for transactions in currency other than Euros.

The lowest commission shall be used if there are multiple rules matching.

Rule #1: Default pricing

By default the price for every transaction is 0.5% but not less than 0.05€.

Rule #2: Client with a discount

Transaction price for the client with ID of 42 is 0.05€ (unless other rules set lower commission).

Rule #3: High turnover discount

Client after reaching transaction turnover of 1000.00€ (per month) gets a discount and transaction commission is 0.03€ for the following transactions.

See below an example in CSV format of rules applied to various transactions.

client_id, date, amount, currency, commission_amount, commission_currency;
42, 2021 - 01 - 02, 2000.0, EUR, 0.05, EUR;
1, 2021 - 01 - 03, 500.0, EUR, 2.5, EUR;
1, 2021 - 01 - 04, 499.0, EUR, 2.5, EUR;
1, 2021 - 01 - 05, 100.0, EUR, 0.5, EUR;
1, 2021 - 01 - 06, 1.0, EUR, 0.03, EUR;
1, 2021 - 02 - 01, 500.0, EUR, 2.5, EUR;

Please write at least one unit and one integration test.

• You can use any language and any framework. We expect you to show knowledge of your chosen language's ecosystem (frameworks, 3rd party libraries, etc.)
• Code must follow good practices (such as SOLID, design patterns, etc.) and be easily extendable in case we need to add additional commission calculation rules in the future
• Please include README.md with instructions how to run your completed task.