shu-yusa/paidy-forex

Paidy Forex

Prerequisites

• JDK (verified with JDK 17)
• Apache Maven

Build and test the application

To build and run unit tests, run the following command in the root folder

mvn verify

To run the application, run the following commands

docker compose up -d  # This runs the paidyinc/one-frame container
./run.sh  # This runs application on port 80. To use a different port, config.properties needs to be modified.

To get an exchange rate, run the following command (or open the url with a web browser)

curl "http://127.0.0.1/rate?from=USD&to=JPY"

An example of the output looks like

{"rate":0.71,"from":"USD","to":"JPY"}

API Specification

The following is the more formal API specification.

• Endpoint: http://127.0.0.1/rate
• HTTP Method: GET

Parameter	Type	Required	Description
from	string	yes	Source currency code. Supported currency codes are AUD, CAD, CHF, EUR, GBP, NZD, JPY, SGD, USD.
to	string	yes	Target currency code. Supported currency codes are AUD, CAD, CHF, EUR, GBP, NZD, JPY, SGD, USD.

Successful Response

• Response headers
  • Content-Type: application/json
• Response body

Parameter	Type	Description
from	string	Source currency code.
to	string	Target currency code.
rate	number	Exchange rate of the given currency pair.

Example of response

HTTP/1.1 200 OK
Date: Fri, 01 Apr 2022 13:33:20 GMT
Content-type: application/json
Content-length: 38

{"rate":0.29,"from":"USD","to":"JPY"}

Error Response

When either or both of from or to parameters are missing, the application returns 400 response. Here is an example response when to parameter is missing.

HTTP/1.1 400 Bad Request
Date: Fri, 01 Apr 2022 13:39:26 GMT
Content-type: application/json
Content-length: 73

{"message":"Parameters are invalid","errors":{"to":"Required parameter"}}

The following is a response example when an unsupported currency code is queried.

HTTP/1.1 400 Bad Request
Date: Fri, 01 Apr 2022 15:57:09 GMT
Content-type: application/json
Content-length: 80

{"message":"Parameters are invalid","errors":{"to":"Unsupported currency code"}}

The following is a response example when an exchange rate for a same currency is queried.

HTTP/1.1 400 Bad Request
Date: Fri, 01 Apr 2022 15:57:09 GMT
Content-type: application/json
Content-length: 95

{"message":"Parameters are invalid","errors":{"to":"Different currencies should be specified"}}

When one-frame API is unavailable (when the container is not running or reached the rate limit), the application returns 503 response. Here is the response example.

HTTP/1.1 503 Service Unavailable
Date: Fri, 01 Apr 2022 13:45:32 GMT
Content-type: application/json
Content-length: 48

{"message":"Service is temporarily unavailable"}

paidy-forex's Issues

Reusable data caching

To make the caching reusable to different use cases in the future, the following refactoring can be considered.

• Define a generic interface QueryService
• Extract caching logic as a decorator

Use logger instead of printing to std output

Replace System.out.println with a logger