heaxagonal-clients-backcompat

app.kt

fun main() {
    val v1 = CatsDao.v1(ClientV1("http://catdocs.com"))
    val v2 = CatsDao.v2(ClientV2("https://api.catdocs.com"))
    val backCompat = CatsDao.backCompat(v1 = v1, v2 = v2)

    val apiFeatureFlag = FeatureFlag.static(
        treatments = mapOf("123" to "v1", "b692b290-40c4-4c0f-89ac-ed0a537e1736" to "v2"),
        default = "v2"
    )

    val dao = CatsDao.toggled(apiFeatureFlag, v1 = v1, v2 = backCompat)

    val ui = CatUi(dao)
    println(ui.renderCatHtml("123"))
    println(ui.renderCatHtml("b692b290-40c4-4c0f-89ac-ed0a537e1736"))
}

backCompatCatsDao.kt

fun CatsDao.Companion.toggled(flag: FeatureFlag, v1: CatsDao, v2: CatsDao) = CatsDao { id ->
    val treatment = flag[id]
    val dao = if (treatment == "v1") v1 else v2
    dao[id]
}

fun CatsDao.Companion.backCompat(v1: CatsDao, v2: CatsDao) = CatsDao { id ->
    v2[id] ?: v1[id]
}