test futures

package chaordic.mailmou.run.test

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.{Await, future, Future}
import scala.concurrent._
import scala.concurrent.duration._

object TestFutures { // extends App {
  type Y = () => Future[Widget]
  type K = () => Future[List[Y]]

  case class Widget(id: String)

  def cache() : K = () => future {
    println("request")

    List(
      () => Future.successful(Widget("a")),
      () => Future.successful(Widget("b"))
    )
  }
  def cats() : K = () => {
    future {
      List("catA", "catB", "catC")
    } map { categories => categories map { cat =>
      () => future {
          Widget(cat)
        }
      }
    }
  }
  def fallback() : K = () => Future.successful(List(() => Future.successful(Widget("f")), () => Future.successful(Widget("j"))))

  val candidates: List[K] = List(cache(), cats(), fallback())

  def findWidgets(candidates: List[K]) : Future[List[Widget]] = {
    val p = Promise[List[Widget]]()
    def getWidgets(list: List[Widget], candidates : List[K], x: List[Y]) : Unit = x match {
      case head :: tail if list.size < 2 => head().map( w => getWidgets(list :+ w, candidates, tail) )
      case _ => getNext(list, candidates)
    }
    def getNext(list: List[Widget], candidates : List[K]) = candidates match {
      case head :: tail if list.size < 2 => head().map(w => getWidgets(list, tail, w))
      case _ => p.success(list)
    }
    getNext(Nil, candidates)
    p.future
  }

  findWidgets(candidates).map { i =>
    println("done "+i)
  }
}