import scala.language.higherKinds
import scalaz._
import Scalaz._
import iteratee._
import iteratee.Input._
import iteratee.Iteratee._
import scalaz.std.iterable._

object Run extends App {
  // sample using State monad

  def sampleI[A](k: Int): Iteratee[A, Vector[A]] =
    sampleI[A](k, 0, Vector())

  private def sampleI[A](k: Int, n: Int, sample: Vector[A]):
                  Iteratee[A, Vector[A]] =
    cont[A, Id, Vector[A]]((c: Input[A]) => c match {
        case Element(x) =>
          sampleI(k, n + 1, algorithmR(k, n + 1, sample, x))
        case _          =>
          done(sample, Empty[A])
      })

  val rand = new scala.util.Random()

  def algorithmR[A](k: Int, n: Int, sample: Vector[A], x: A): Vector[A] = {
    if (sample.size < k) {
      sample :+ x // must keep first k elements
    } else {
      val r = rand.nextInt(n) + 1 // for simplicity, rand is global/stateful
      if (r <= k)
        sample.updated(r - 1, x) // sample is 0-index
      else
        sample
    }
  }

  {
    print((sampleI(10) &=
           EnumeratorT.enumStream((Short.MinValue to Short.MaxValue).toStream)
          ).run)
  }
}