Use Case DSL

gistfile1.txt

fun main() {
    val result = GetLatestStringImpl().invoke()
    println(result.getOrNull())
}

interface GetLatestString {
    operator fun invoke(): Result<String>
}

class GetLatestStringImpl : GetLatestString {
    override operator fun invoke() = getLatestCache(
            cacheFound = {
                         // for logging purpose
            },
            cacheNotFound = {
                fetchFromInternet { result ->
                    storeToCache(result) {
                        loadFromCache()
                    }
                }
            }
        )

    private fun loadFromCache(): Result<String> {
        return runCatching {
            // "value" // result
            throw Throwable("not found")
        }
    }

    private fun storeToCache(result: String, function: () -> Result<String>): Result<String> {
        // store cache logic there
        println("$result inserted to cache")
        return function()
    }

    private fun fetchFromInternet(success:(String) -> Result<String>) : Result<String> {
        // perform network request
        val networkResult = "value"
        return success(networkResult)
    }

    private fun getLatestCache(cacheFound: (String) -> Unit, cacheNotFound: () -> Result<String>): Result<String> {
        return loadFromCache().onFailure {
            cacheNotFound()
        }.onSuccess {
            cacheFound(it)
        }
    }
}