simple-state-machine-3.kt

fun List<Transition<State, State>>.fold(initial: State.RequestReceived): State.ResponseValidated {
  var currentState: State = initial
  forEach {
    currentState = it.invoke(currentState)
  }
  if (currentState is State.ResponseValidated) {
    return currentState as State.ResponseValidated
  } else {
    throw IllegalStateException("currentState is not of State.ResponseValidated type")
  }
}