Currency converter API and CLI client

Its better to use NoSQL database instead of postgres

But i've used Postgres because it was in position requirements:)

Run

There are Docker containers in the project. If you want to create it and run following command:

docker-compose up --build -d

To prepare database you need to apply migrations with:

docker-compose exec app /vent/bin/python manage.py migrate

To fill data in database you can use this command:

docker-compose exec app /vent/bin/python manage.py update_rates

This command create currencies if there are no them in database. And then it replaces all exchange rates with actual.

Makefile

There is makefile available in the project. So you can run project with make.

Admin panel

There is admin panel available in the project. To access admin panel you need to have superuser account. It can be created with the following command:

docker-compose exec app /venv/bin/python manage.py createsuperuser

Documentation

There is documentation available in the project. You can access it with link in the admin or with the following link:

/admin/doc/models/

Data update

Exchange rates change very quick. So good currency converter should update rates At least once per day.

Now there are two update providers in this project:

• RatesAPI
• ExchangeRatesAPI

They are free and have only 35 currencies with exchange rates. By default is used RatesAPI. You can change it in currency_converter/settings.py.

EXCHANGE_RATE_PROVIDER = 'ratesapi'

Also you can add your own exchange rate provider in these steps:

1. Implement method for RateProvider class located in api/rate_provider.py The name of the method must be protected(with underscore) _method_name. It must take currency code for which it will give the rates. Output is dict of rates. Where keys are 3-character length currency codes. And values are floats or integers with current exchange rates.
2. Register the method in RateProvider.ACTIVE_PROVIDERS. Put the name of the method without underscore.

Actualize Rates

To actualize rates on production - use cron and choose your update frequency

docker-compose exec app /vent/bin/python manage.py update_rates

Examples

If there is some error API returns json object with error key:

/currency_converter?amount=100&input_currency=$$

{"error": {"input_currency": ["Incorrect currency"]}}

In case if currency code is used with more then one currencies there will be error:

{"error": {"input_currency": ["Selected symbol is used to define multiple currencies. Use currency code instead"]}}

CLI

./currency_converter.py --amount 100.0 --input_currency EUR --output_currency CZK
{   
    "input": {
        "amount": 100.0,
        "currency": "EUR"
    },
    "output": {
        "CZK": 2707.36, 
    }
}

./currency_converter.py --amount 0.9 --input_currency ¥ --output_currency AUD
{   
    "input": {
        "amount": 0.9,
        "currency": "CNY"
    },
    "output": {
        "AUD": 0.20, 
    }
}

./currency_converter.py --amount 10.92 --input_currency £ 
{
    "input": {
        "amount": 10.92,
        "currency": "GBP"
    },
    "output": {
        "EUR": 14.95,
        "USD": 17.05,
        "CZK": 404.82,
        .
        .
        .
    }
}

API

GET /currency_converter?amount=0.9&input_currency=¥&output_currency=AUD HTTP/1.1
{   
    "input": {
        "amount": 0.9,
        "currency": "CNY"
    },
    "output": {
        "AUD": 0.20, 
    }
}

GET /currency_converter?amount=10.92&input_currency=£ HTTP/1.1
{
    "input": {
        "amount": 10.92,
        "currency": "GBP"
    },
    "output": {
        "EUR": 14.95,
        "USD": 17.05,
        "CZK": 404.82,
        .
        .
        .
    }
}