Fetches exchange rate from the European Central Bank https://exchangeratesapi.io

ExchangeRates.kt

import com.google.gson.Gson
import com.google.gson.JsonObject

enum class CurrencySymbol {
    EUR, CAD, HKD, ISK, PHP, DKK, HUF, CZK, AUD, RON, SEK,
    IDR, INR, BRL, RUB, HRK, JPY, THB, CHF, SGD, PLN, BGN,
    TRY, CNY, NOK, NZD, ZAR, USD, MXN, ILS, GBP, KRW, MYR
}

/**
 * Fetches exchange rate from the European Central Bank https://exchangeratesapi.io
 * @param base base currency
 * @param currency target currency
 * @return The exchange rate
 */
fun getRate(base: CurrencySymbol, currency: CurrencySymbol): Double? {
    return try {
        val url = "https://api.exchangeratesapi.io/latest?base=$base&symbols=$currency"
        val json = java.net.URL(url).readText()
        val jsonObject = Gson().fromJson<JsonObject>(json, JsonObject::class.java)
        jsonObject["rates"].asJsonObject[currency.name].asDouble
    } catch (e: Exception) {
        null
    }
}