The hidden complexity of scaling WebSockets(composehq.com)

  const onConnect: ChannelConnection<'hello!'> = async (services, channel) => {
    // On connection (like onOpen)
    channel.send('hello') // This is checked against the input type
  }

  const onDisconnect: ChannelDisconnection = async (services, channel) => {
    // On close
    // This can't send anything since channel closed
  }

  const onMessage: ChannelMessage<'hello!' | { name: string }, 'hey'> = async (services, channel) => {
    channel.send('hey')
  }

  export const subscribeToLikes: ChannelMessage<
    { talkId: string; action: 'subscribeToLikes' },
    { action: string; likes: number }
  > = async (services, channel, { action, talkId }) => {
    const channelName = services.talks.getChannelName(talkId)
    // This is a service that implements a pubsub/eventhub interface
    await services.eventHub.subscribe(channelName, channel.channelId)
    // we return the action since the frontend can use it to route to specific listeners as well (this could be absorbed by vrameworks runtime in future)
    return { action, likes: await services.talks.getLikes(talkId) }
  }

  addChannel({
    name: 'talks',
    route: '/',
    auth: true,
    onConnect,
    onDisconnect,
    // Default message handler
    onMessage,
    // This will route the message to the correct function if a property action exists with the value subscribeToLikes (or otherwise)
    onMessageRoute: {
      action: {
        subscribeToLikes: {
          func: subscribeToLikes,
          permissions: {
            isTalkMember: [isTalkMember, isNotPresenter],
            isAdmin
          },
        },
      },
    },
  })