package java2scala.homeworks.funcs

trait ChurchBool {
  def cif[A](ifTrue: => A)(ifFalse: => A): A

  def toBool: Boolean = cif(true)(false)

  def unary_! : ChurchBool             = new ChurchBool.Not(this)

  def &&(that: ChurchBool): ChurchBool = new ChurchBool.And(this, that)
  def ||(that: ChurchBool): ChurchBool = new ChurchBool.Or(this, that)
}

object ChurchBool {
  def apply(x: Boolean): ChurchBool = if (x) True else False

  val True: ChurchBool = new ChurchBool {
    override def cif[A](ifTrue: => A)(ifFalse: => A): A = ifTrue
  }

  val False: ChurchBool = new ChurchBool {
    override def cif[A](ifTrue: => A)(ifFalse: => A): A = ifFalse
  }

  class Not private[ChurchBool] (bool: ChurchBool) extends ChurchBool {
    override def cif[A](ifTrue: => A)(ifFalse: => A): A = bool.cif(ifFalse)(ifTrue)
  }

  class And private[ChurchBool] (left: ChurchBool, right: ChurchBool) extends ChurchBool {
    override def cif[A](ifTrue: => A)(ifFalse: => A): A = left.cif(right.cif(ifTrue)(ifFalse))(ifFalse)
  }

  class Or private[ChurchBool] (left: ChurchBool, right: ChurchBool) extends ChurchBool {
    override def cif[A](ifTrue: => A)(ifFalse: => A): A = left.cif(ifTrue)(right.cif(ifTrue)(ifFalse))
  }
}