replExaple.scala

object SimulationCLI extends App {

  type CommandAction = (Seq[String], ElevatorControlSystemAPI) => Option[ElevatorControlSystemAPI]

  val commands: Map[String, CommandAction] =
    Map(
      "state" -> { (args, ecs) =>
        ecs.status.toSeq.sortBy(_._1) foreach {
          case (elevatorId, ElevatorState(movement, floor)) =>
            val movementStr = movement map {
              case Up => "/\\"
              case Down => "\\/"
            } getOrElse "--"
            println(s"$floor $movementStr <- $elevatorId")
        }
        Some(ecs)
      },
      "quit" -> { (_, _) => None },
      "step" -> { (_, ecs) =>
        println("Executed one simulation step")
        Some(ecs.step)
      },
      "pickup" -> { (args, ecs) =>
        if(args.size != 2 ||
          args(0).exists(c => !('0' to '9').contains(c) && c != '-') ||
          !Set("up", "down").contains(args(1).trim.toLowerCase)
        ) {
          println(s"Invalid pickup request: $args")
        } else {
          val floor = args(0).toInt
          val direction = if(args(1) == "up") Up else Down
          val pickupPromise = ecs.passengerCommand(PickUp(floor, direction))
          pickupPromise.onSuccess { case rq => println("Completed task: " + rq) } {
            scala.concurrent.ExecutionContext.Implicits.global
          }
          println(s"Registered pick up request to $floor $direction")
        }
        Some(ecs)
      }
    )

  val invalidCommand: CommandAction = {
    (_, ecs) =>
      println("INVALID COMMAND")
      Some(ecs)
  }

  def repl(currentSystem: ElevatorControlSystemAPI): Unit = {
    print("> ")
    val Array(command, arguments @ _*) = readLine.split(' ').map(_.trim)
    val newSystem = commands.getOrElse(command, invalidCommand)(arguments, currentSystem)
    //Not using map in order to make a tail recursive call
    if(newSystem.isDefined) repl(newSystem.get)
  }

  repl(ElevatorControlSystem())

}