pagination

pagination.scala

object Pagination {

  def pagedRequest[F[_], A] (
    f: Offset => F[Page[A]],
    offset: Offset
  ) : Process[F, A] = {
    Process
      .eval(f(offset))
      .flatMap { response: Page[A] =>
        Process.emitAll(response.results) ++
          response.offset.map { o =>
            pagedRequest(f, Option(o))
          }.getOrElse(Process.empty[F, A])
      }
  }
}

test.scala

class Test extends Specification with ScalaCheck {

  implicit val IdIsCatchable : Catchable[Id] = new Catchable[Id] {
    override def attempt[A](f: Id.Id[A]): Id.Id[\/[Throwable, A]] =
      \/-(f)

    override def fail[A](err: Throwable): Id.Id[A] = throw err
  }

  "pagination is flattening" >>
    prop { (is: List[List[Int]]) =>

      val f: (Offset) => Page[Int] =
        (o:Offset) => {
          val length = is.size

          val fs = is.zipWithIndex.map { case (i: List[Int], idx: Int) =>
            idx -> Page(i, if (idx < length-1) Some(idx+1) else None)
          }.toMap

          o.map(fs(_)).get
        }

      is.flatten must_== pagedRequest[Id, Int](f, Some(0)).runLog
    }.setGen(Gen.nonEmptyListOf(Gen.listOf(Gen.posNum[Int])))

}