typealias Namespace = String

sealed class RuntimeProperties(val ns: Namespace, val properties: Properties)
class FooProperties(properties: Properties) : RuntimeProperties("foo", properties) {
    val url  by PropertyResolver.String
    val user by PropertyResolver.String
    val pass by PropertyResolver.String
}

class BarProperties(properties: Properties) : RuntimeProperties("bar", properties) {
    val maximum: Int by PropertyResolver(Int::class)
}

class PropertyResolver<T : Any>(x: KClass<T>) : ReadOnlyProperty<RuntimeProperties, T> {
    companion object {
        val String = PropertyResolver(String::class)
    }

    override operator fun getValue(thisRef: RuntimeProperties, property: KProperty<*>): T = with(thisRef) {
        val key = "${ns}.${property.name}"
        val raw = properties.getOrElse(key) {
            error("$key is not set among ${properties.propertyNames()}")
        }!!.toString()

        val type = property.returnType.jvmErasure
        return when (type) {
            Int::class -> parseInt(raw)
            Long::class -> parseLong(raw)
            String::class -> raw

            else -> error("$type cannot be handled")
        } as T
    }
}