jupyter.kernel.protocol.Enumerate.scala Maven / Gradle / Ivy

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package jupyter.kernel.protocol

import shapeless.{ :+:, ::, CNil, Coproduct, Generic, HList, HNil, Inl, Inr, Strict }

sealed abstract class Enumerate[T] {
  def apply(): Seq[T]
}

object Enumerate {
  def apply[T](implicit enum: Enumerate[T]): Enumerate[T] = enum

  private def instance[T](values: => Seq[T]): Enumerate[T] =
    new Enumerate[T] {
      def apply() = values
    }

  implicit val boolean: Enumerate[Boolean] =
    instance(Seq(true, false))

  implicit val hnil: Enumerate[HNil] =
    instance(Seq(HNil))
  implicit def hcons[H, T <: HList]
   (implicit
     head: Strict[Enumerate[H]],
     tail: Enumerate[T]
   ): Enumerate[H :: T] =
    instance {
      for {
        h <- head.value()
        t <- tail()
      } yield h :: t
    }

  implicit val cnil: Enumerate[CNil] =
    instance(Seq())
  implicit def ccons[H, T <: Coproduct]
   (implicit
     head: Strict[Enumerate[H]],
     tail: Enumerate[T]
   ): Enumerate[H :+: T] =
    instance(head.value().map(Inl(_)) ++ tail().map(Inr(_)))

  implicit def generic[F, G]
   (implicit
     gen: Generic.Aux[F, G],
     underlying: Strict[Enumerate[G]]
   ): Enumerate[F] =
    instance(underlying.value().map(gen.from))
}