Akka Streams - Combine different Sources - scala

Question

i have an object that builds different Flows, each flow has filters, that may can discard values, so the final result may contain a subset of the original source.
The code:
object RawFlowGeneratorByVehicle {
val deviceEventFilter = (de : DeviceEvent) => de.isValidPosition : Boolean
def buildSpeedFlow(vehicles : List[Vehicle]) : VEHICLERAWFLOW = {
Flow[DeviceEvent].filter(deviceEventFilter)
.groupBy(vehicles.length,de => de.getModemId)
.reduce((a, b) => if(a.getGenerationDate >= b.getGenerationDate) a else b)
.mergeSubstreams
.map(de => VehicleFlowResult(de.getModemId,"Speed",de.getSpeed))
}
def buildCountFlow(vehicles: List[Vehicle], maxSpeed : Double) : VEHICLERAWFLOW = {
Flow[DeviceEvent].filter(deviceEventFilter)
.groupBy(vehicles.length,de => de.getModemId)
.filter(de => de.getSpeed > maxSpeed)
.map(_ -> 1)
.reduce((l, r) => (l._1, l._2 + r._2))
.mergeSubstreams
.map(a => VehicleFlowResult(a._1.getModemId, "SpeedCount", a._2))
}
//...Other flows
}
After build the flows, merge them in a graph and the final result is a csv file , this is the object with the graph
object RunnableFlows {
def rawGraph(in: Source[DeviceEvent, NotUsed], flows: List[VEHICLERAWFLOW]): Source[VehicleFlowResult, NotUsed] = {
val g = Source.fromGraph(GraphDSL.create() { implicit builder: GraphDSL.Builder[NotUsed] =>
import GraphDSL.Implicits._
val bcast = builder.add(Broadcast[DeviceEvent](flows.length))
val merge = builder.add(Merge[VehicleFlowResult](flows.length))
in ~> bcast ~> flows.head ~> merge
for (curFlow <- flows.tail) {
bcast ~> curFlow ~> merge
}
SourceShape(merge.out)
})
g
}
}
the flows may have different size , so i dont know how to merge/concat/zip?, to generate a csv of the same size of rows like the vehicles list(this list dont have duplicate values),setting default values when an specific vehicle not pass the filters of the flows
The csv must be something like this
imei;name;event;value
aaa;vehicle1;Event1;100
aaa;vehicle1;Event2;100
bbb;vehicle2;DefaultEvent;defaultValue
ccc;vehicle3;Event5;89
Thanks!!