outwatch-test/src/main/scala/outwatchapp/util/reactive/WebWorker.scala

package outwatchapp.util.reactive

import scala.concurrent.Future

import io.circe.Decoder
import io.circe.Encoder
import io.circe.Printer
import io.circe.generic.JsonCodec
import io.circe.parser._
import io.circe.syntax._
import monix.bio.Task
import monix.execution.Ack
import monix.execution.Cancelable
import monix.reactive.Observable
import monix.reactive.Observer
import monix.reactive.OverflowStrategy
import outwatchapp.util.reactive.MonixProSubject
import org.scalajs.dom.raw.Event
import org.scalajs.dom.raw.MessageEvent
import org.scalajs.dom.{raw => sjsdr}

class WebWorkerImpl[T <: Product: Encoder: Decoder](
    worker: sjsdr.Worker,
    overflowStrategy: OverflowStrategy.Synchronous[T]
) {

//   private def parseFn(data: T) = {
//     data match {
//       case _: AnyRef => parseRef(data)
//       case s: String =>
//       case other =>
//         println(other)
//         Left(WebWorker.Error)
//     }
//   }

//   private def parseRef(data: T): Either[WebWorker.Error, T] = {
//     data match {
//       case s: String => decode[T](s).leftMap(_ => WebWorker.Error)
//       case a: Int =>
//         println(a)
//         Left(WebWorker.Error)
//       case other =>
//         println(other)
//         Left(WebWorker.Error)
//     }
//   }
//   private def parsePrimitive(data: T): Either[WebWorker.Error, T] = {
//     data match {
//       case s: String => decode[T](s).leftMap(_ => WebWorker.Error)
//       case a: Int =>
//         println(a)
//         Left(WebWorker.Error)
//       case other =>
//         println(other)
//         Left(WebWorker.Error)
//     }
//   }
// println(s"Got data $a")
//   .map(sub.onNext).left.foreach(println)

  val printer = Printer.noSpaces

  lazy val source: Task[Observable[T]] =
    Task.deferAction(implicit s =>
      for {
        obs <- Task(
          Observable
            .create[T](overflowStrategy) { sub =>
              worker.onmessage = (e: MessageEvent) =>
                e.data match {
                  case s: String =>
                    decode[T](s).map(sub.onNext).left.foreach(println)
                  case other => println(other)
                }
              worker.onerror = (e: Event) =>
                sub.onError(new Exception(s"Error in WebSocket: $e"))
              Cancelable(() => worker.terminate())
            }
            .publish
            .refCount
        )
        _ <- Task(obs.subscribe(Observer.empty))
      } yield obs
    )

  lazy val sink: Task[Observer[T]] =
    Task(
      new Observer[T] {
        override def onNext(elem: T): Future[Ack] = {
          val msg = printer.print(elem.asJson)
          worker.postMessage(msg)
          Future.successful(Ack.Continue)
        }
        override def onError(ex: Throwable): Unit = println(ex)
        override def onComplete(): Unit = ()
      }
    )

}
object WebWorker {
  sealed trait Error
  final case object Error extends Error
  // val w = new sjsdr.Worker("/worker.js").asInstanceOf[Worker]

  // type MonixWebWorker[T] = MonixProSubject[T, T]

  def apply[T <: Product: Encoder: Decoder](
      path: String,
      overflowStrategy: OverflowStrategy.Synchronous[T] =
        OverflowStrategy.DropOld(50)
  ): Task[WebWorker[T]] = for {
    worker <- Task(new sjsdr.Worker(path))
    impl = new WebWorkerImpl[T](worker, overflowStrategy)
    source <- impl.source
    sink <- impl.sink
  } yield MonixProSubject.from(sink, source)

}

@JsonCodec
case class WorkerData(data: Long)