Illustrate fundamental structure on which Akka reactive stream switch could be implemented

BroadcastFilterMerge.scala

package conditionals

import scala.collection.immutable.Seq
import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.stream.scaladsl.Source
import scala.concurrent.Future
import akka.stream.scaladsl.Sink
import akka.stream.scaladsl.FlowGraph
import akka.stream.scaladsl.Broadcast
import akka.stream.scaladsl.Merge
import akka.stream.scaladsl.Flow
import akka.stream.FlowShape

/**
 * Prints 3 and 6
 */
object BroadcastFilterMerge extends App {
  implicit val system = ActorSystem("Sys")
  import system.dispatcher
  implicit val materializer = ActorMaterializer()

  val g = FlowGraph.partial() { implicit builder: FlowGraph.Builder[Unit] =>

    val broadcast = builder.add(Broadcast[Int](2))
    val merge = builder.add(Merge[Int](2))

    val f1 = Flow[Int].filter { _ == 3 }
    val f2 = Flow[Int].filter { _ == 6 }

    builder.addEdge(broadcast.out(0), f1, merge.in(0))
    builder.addEdge(broadcast.out(1), f2, merge.in(1))

    FlowShape[Int, Int](broadcast.in, merge.out)
  }

  val in = Source(1 to 10)

  val r = in
    .via(g)
    .runForeach(println)

  r.onComplete {
    case x @ _ => system.shutdown
  }

}