https://github.com/gvolpe/exchange-rates

:currency_exchange: Querying a rate-limited currency exchange API using Redis as a cache
https://github.com/gvolpe/exchange-rates

cache dhall dhall-lang exchange-rates forex haskell rate-limiter redis transient wreq

Last synced: 3 months ago
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:currency_exchange: Querying a rate-limited currency exchange API using Redis as a cache

• Host: GitHub
• URL: https://github.com/gvolpe/exchange-rates
• Owner: gvolpe
• License: apache-2.0
• Created: 2019-06-09T22:00:30.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2020-03-07T02:49:06.000Z (almost 5 years ago)
• Last Synced: 2024-10-11T23:45:41.845Z (3 months ago)
• Topics: cache, dhall, dhall-lang, exchange-rates, forex, haskell, rate-limiter, redis, transient, wreq
• Language: Haskell
• Homepage:
• Size: 187 KB
• Stars: 41
• Watchers: 4
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

        
# ![icon](icon.png) exchange-rates

[![CircleCI](https://circleci.com/gh/gvolpe/exchange-rates.svg?style=svg)](https://circleci.com/gh/gvolpe/exchange-rates)

Querying a [rate-limited foreign currency exchange API](https://free.currencyconverterapi.com/) using [Redis](https://redis.io/) as a cache.

- Number of Requests per Hour: 100 (See config file)

### Http Endpoints

#### GET /v1/currencies

Returns a list of the available currencies. Eg:

```json

["USD","EUR","GBP","AUD","CAD","PLN","ARS"]

```

#### GET /v1/rates?from=EUR&to=USD

Returns the current exchange rate, if available:

```json

{"to":"USD","from":"EUR","rate":1.139556}

```

### Run it locally

You'll need a Redis instance. The easiest way to get started is by using `docker`:

```

docker run -it --rm -p 6379:6379 redis:5.0.0

```

And then run the web server app using `cabal new-run exchange-rates`, or using Nix `nix-shell --pure shell.nix` and `cabal new-run exchange-rates`. You should see something like:

```

AppConfig {forex = ForexConfig {host = "https://free.currconv.com/api/v7", apiKey = [SECRET], keyExpiration = 1800}, redis = RedisConfig {redisHost = "127.0.0.1", redisPort = 6379}}

Started server on localhost:8080

Calling web service for: USD -> GBP

Calling web service for: USD -> EUR

Cache hit: USD -> GBP

Calling web service for: USD -> PLN

Cache hit: USD -> PLN

```

Exchange rates are cached to avoid hitting the (limited) external service many times.

### Browse the documentation

The docs are generated at compile time from the API definition. The API serves a `swagger.json` response that you can visualize in the Swagger UI:

```

docker run -p 80:8080 swaggerapi/swagger-ui

```

Go to `localhost` and enter `http://localhost:8080/swagger.json`.

![docs](docs.png)