WebSocketConnection.scala

import cats.effect._
import monix.eval.TaskLike
import monix.execution.Ack.Continue
import monix.execution.{Ack, Cancelable}
import monix.reactive.OverflowStrategy.Unbounded
import monix.reactive._
import mycelium.client.raw.{ReconnectingWebSocket, ReconnectingWebsocketOptions}
import org.scalajs.dom._

import scala.concurrent.Future
import scala.scalajs.js.UndefOr
import scala.scalajs.js.typedarray._

object WebSocketTypes {
  sealed trait WebSocketEvent
  case class Open(event: Event)           extends WebSocketEvent
  case class Close(event: CloseEvent)     extends WebSocketEvent
  case class Message(event: MessageEvent) extends WebSocketEvent
  case class Error(event: Event)          extends WebSocketEvent

  trait WebSocketData {
    def sendData(webSocket: WebSocket)
  }

  implicit class dataString(data: String) extends WebSocketData {
    def sendData(webSocket: WebSocket) = webSocket.send(data)
  }

  implicit class dataBlob(data: Blob) extends WebSocketData {
    def sendData(webSocket: WebSocket) = webSocket.send(data)
  }

  implicit class dataArrayBuffer(data: ArrayBuffer) extends WebSocketData {
    def sendData(webSocket: WebSocket) = webSocket.send(data)
  }
}

class WebSocketConnection(webSocket: WebSocket) {
  import WebSocketTypes._

  def observable: Observable[WebSocketEvent] =
    Observable.create(Unbounded) { observer =>
      webSocket.onopen    = (event: Event)        => observer.onNext(Open(event))
      webSocket.onclose   = (event: CloseEvent)   => observer.onNext(Close(event))
      webSocket.onmessage = (event: MessageEvent) => observer.onNext(Message(event))
      webSocket.onerror   = (event: Event)        => observer.onNext(Error(event))

      Cancelable.empty
    }

  def observer[F[_]: Sync]: F[Observer[WebSocketData]] =
    Sync[F].delay {
      new Observer[WebSocketData] {
        override def onNext(data: WebSocketData): Future[Ack] = {
          data.sendData(webSocket)
          Continue
        }
        override def onError(ex: Throwable) = throw ex
        override def onComplete() = ()
      }
    }
}

object WebSocketConnection {
  def openReconnectingWebSocket[F[_]: Sync](
    url: String
  ): Resource[F, ReconnectingWebSocket] =
    Resource.make {
      Sync[F].delay(new ReconnectingWebSocket(url))
    } { in =>
      Sync[F].delay(in.close())
    }

  def openWebSocket[F[_]: Sync](
    url: String
  ): Resource[F, WebSocket] =
    Resource.make {
      Sync[F].delay(new WebSocket(url))
    } { in =>
      Sync[F].delay(in.close())
    }

  def apply[F[_]: Sync](
    resource: Resource[F, WebSocket]
  ): Resource[F, WebSocketConnection] = resource.evalMap { webSocket =>
    Sync[F].delay(new WebSocketConnection(webSocket))
  }
}