object timeunits extends App {
  // sealed trait + N * case (class|object) == ADT

  sealed trait Timeunit
  case class Millis (x: Long) extends Timeunit
  case class Seconds(x: Long) extends Timeunit
  case class Minutes(x: Long) extends Timeunit
  case class Hours  (x: Long) extends Timeunit

  implicit class DotComposition[R, T1](f: T1 => R) {
    def ∘[A](g: A => T1) = f compose g
  }

  def inMillis  = identity(_: Long)
  def inSeconds = inMillis  ∘ ((_: Long) * 1000)
  def inMinutes = inSeconds ∘ ((_: Long) * 60)
  def inHours   = inMinutes ∘ ((_: Long) * 60)

  def toMillis = (_: Timeunit) match {
    case Millis(x)  => inMillis(x)
    case Seconds(x) => inSeconds(x)
    case Minutes(x) => inMinutes(x)
    case Hours(x)   => inHours(x)
  }

  // reaalselt kasutuses
  implicit class LongWithTimeunits(x: Long) {
    def millis  = Millis(x);  def milli  = millis
    def seconds = Seconds(x); def second = seconds
    def minutes = Minutes(x); def minute = minutes
    def hours   = Hours(x);   def hour   = hours
  }

  def sleep1(t: Timeunit) = Thread.sleep(toMillis(t))
  sleep1(2.seconds)

  // üks võimalik vaste Haskelli versioonile
  def sleep2(t: Long, unit: Long => Timeunit) = Thread.sleep(toMillis(unit(t)))
  sleep2(500, Millis)
}