WebSocket in Mint

WebSocket.mint

record Provider.WebSocket.Subscription {
  endpoint : Url,
  message : Function(Html.Event, Void),
  open : Function(Html.Event, Void),
  error : Function(Html.Event, Void)
}

provider Provider.WebSocket : Provider.WebSocket.Subscription {
  fun attach : Void {
    `
    (() => {
      this.subscriptions.forEach((subscription) => {
        const url = subscription.endpoint.origin + subscription.endpoint.path
        const open = this[url + "_open"] || (this[url + "_open"] = subscription.open.bind(this))
        const message = this[url + "_message"] || (this[url + "_message"] = subscription.message.bind(this))
        const error = this[url + "_error"] || (this[url + "_error"] = subscription.error.bind(this))

        var socket
        var interval = 1000 // make exponential backoff

        const socketCloseListener = (event) => {
          if (socket) { console.error("Reconnecting WebSocket") }
          socket = new WebSocket(url)
          socket.addEventListener("close", () => setTimeout(socketCloseListener, interval))
          socket.addEventListener("open", open)
          socket.addEventListener("message", message)
          socket.addEventListener("error", error)
        }

        socketCloseListener()
      })
    })()
    `
  }

  fun detach : Void {
    `
    socket.close(1000, "socket detached")
    `
  }
}