demo.go

// AddSubscription appends a successful subscription
func (w *Websocket) AddSubscription(cs ...ChannelSubscription) {
	w.subscriptions = append(w.subscriptions, cs...)
}

// Demos how it can be handled when only one request sent
func (b *Bitmex) Subscribe(channelsToSubscribe []stream.ChannelSubscription) error {
	var subscriber WebsocketRequest
	subscriber.Command = "subscribe"

	for i := range channelsToSubscribe {
		subscriber.Arguments = append(subscriber.Arguments,
			channelsToSubscribe[i].Channel)
	}
	
  err := b.Websocket.Conn.SendJSONMessage(subscriber)
  if err != nil {
    return err
  }
  b.Websocket.AddSubscription(channelsToSubscribe...)
  return nil
}

// Demos how it can be handled when errors can occur per generic send
func (b *Bitstamp) Subscribe(channelsToSubscribe []stream.ChannelSubscription) error {
	var errs common.Errors
	for i := range channelsToSubscribe {
		req := websocketEventRequest{
			Event: "bts:subscribe",
			Data: websocketData{
				Channel: channelsToSubscribe[i].Channel,
			},
		}
		err := b.Websocket.Conn.SendJSONMessage(req)
		if err != nil {
			errs = append(errs,  err)
			continue
		}
		b.Websocket.AddSubscription(channelsToSubscribe[i])
	}
	return errs
}

// Demo for more complicated Kraken
func (k *Kraken) Subscribe(channelsToSubscribe []stream.ChannelSubscription) error {
	var errs common.Errors
	var subs []WebsocketSubscriptionEventRequest
channels:
	for x := range channelsToSubscribe {
		for y := range subs {
			if subs[y].Subscription.Name == channelsToSubscribe[x].Channel {
				subs[y].Pairs = append(subs[y].Pairs,
					channelsToSubscribe[x].Currency.String())
				continue channels
			}
		}

		var id int64
		if common.StringDataContains(authenticatedChannels, channelsToSubscribe[x].Channel) {
			id = k.Websocket.AuthConn.GenerateMessageID(false)
		} else {
			id = k.Websocket.Conn.GenerateMessageID(false)
		}

		resp := WebsocketSubscriptionEventRequest{
			Event: krakenWsSubscribe,
			Subscription: WebsocketSubscriptionData{
				Name: channelsToSubscribe[x].Channel,
			},
			RequestID: id,
		}
		if channelsToSubscribe[x].Channel == "book" {
			// TODO: Add ability to make depth customisable
			resp.Subscription.Depth = 1000
		}
		if !channelsToSubscribe[x].Currency.IsEmpty() {
			resp.Pairs = []string{channelsToSubscribe[x].Currency.String()}
		}
		if channelsToSubscribe[x].Params != nil {
			resp.Subscription.Token = authToken
		}
		subs = append(subs, resp)
	}

	for i := range subs {
		if common.StringDataContains(authenticatedChannels, subs[i].Subscription.Name) {
			_, err := k.Websocket.AuthConn.SendMessageReturnResponse(subs[i].RequestID, subs[i])
			if err != nil {
				errs = append(errs, err)
			}
			k.Websocket.AddSubscription(channelsToSubscribe[i])
			continue
		}

		_, err := k.Websocket.Conn.SendMessageReturnResponse(subs[i].RequestID, subs[i])
		if err != nil {
			errs = append(errs, err)
		}
		k.Websocket.AddSubscription(channelsToSubscribe[i])
	}
	return errs
}