outwatch-test/src/main/scala/outwatch/util/MonixWebSocket.scala

package outwatch.util

import scala.concurrent.Future

import cats.Show
import cats.effect.Sync
import monix.execution.Ack
import monix.execution.Cancelable
import monix.reactive.Observable
import monix.reactive.Observer
import monix.reactive.OverflowStrategy
import org.scalajs.dom.Event
import org.scalajs.dom.MessageEvent
import outwatch.helpers._

object MonixWS {
  // implicit def toObserver[F[_]: Sync, S: Show](
  //     socket: MonixWS[F, S]
  // ): F[Observer[S]] = socket.sink
  // implicit def toObservable[F[_]: Sync, S: Show](
  //     socket: MonixWS[F, S]
  // ): Observable[MessageEvent] = socket.source
}

class MonixWS[F[_], S](val url: String)(implicit F: Sync[F], S: Show[S]) {
  val ws = new org.scalajs.dom.WebSocket(url)

  val source: Observable[MessageEvent] =
    Observable.create[MessageEvent](OverflowStrategy.Unbounded) { sub =>
      ws.onmessage = (e: MessageEvent) => sub.onNext(e)
      ws.onerror =
        (e: Event) => sub.onError(new Exception(s"Error in WebSocket: $e"))
      Cancelable(() => ws.close())
    }

  val sink: F[Observer[S]] = {
    F.delay {
      new Observer[S] {
        override def onNext(elem: S): Future[Ack] = {
          ws.send(S.show(elem))
          Future.successful(Ack.Continue)
        }
        override def onError(ex: Throwable): Unit =
          OutwatchTracing.errorSubject.onNext(ex)
        override def onComplete(): Unit = ()
      }
    }
  }
}