Example of a port and an adapter

ExchangeRateApiClient.kt

// in Domain Module
data class ExchangeRateDto(val rate: BigDecimal, val currency: Currency)

interface ExchangeRateApiClientPort {
	fun getRate(source: Currency, target: Currency): ExchangeRateDto
}

// in Infrastructure Module
class ExchangeRateApiClientAdapter : ExchangeRateApiClientPort {
	override fun getRate(source: Currency, target: Currency): ExchangeRateDto {
		val rate = MonetaryConversions
			.getConversion(source.toString())
			.getExchangeRate(moneta.Money.of(1, target.toString()))
		return ExchangeRateDto(
			rate.factor.numberValueExact(BigDecimal::class.java),
			Currency.valueOf(rate.currency.currencyCode)
		)
	}
}