Exploring first Bucklescript

websocket.ml

type socket
type event

type config = {
  reconnect: bool;
  debug: bool;
  timeout: int;
  interval: int
}

type callback = (socket -> config -> event -> unit) option

type callbacks = {
  on_open: callback;
  on_error: callback;
  on_close: callback;
  on_message: callback
}


(* External JS *)
external create_ws : string -> socket = "WebSocket" [@@bs.new]
external add_listener : socket -> string -> (event -> unit) -> unit =
  "addEventListener" [@@bs.send]

(* Helper functions *)
let debug_log msg =
  match msg with
  | "" -> ()
  | _ -> Js.log msg

let inject_handler f args =
  match f with
  | None -> ()
  | Some f -> let (socket, config, ev) = args in f socket config ev

let init_socket uri config callbacks =
  let { reconnect; debug; timeout; interval } = config in
  let { on_open; on_error; on_close; on_message } = callbacks in
  let socket = create_ws uri in
  let events = [ ("open", "Connected", on_open)
               ; ("error", "", on_error)
               ; ("close", "Disconnected", on_close)
               ; ("message", "Incoming", on_message)
               ] in
    events |> List.iter (fun event ->
      let (ev_name, ev_message, ev_callback) = event in
        add_listener socket ev_name ( fun ev ->
          if debug && ev_message <> "" then debug_log ev_message;
          inject_handler ev_callback (socket, config, ev)
        )
    )

let main () =
  let uri = "wss://endpoint.lol/api/services/foo/bar" in
  let config = {reconnect = true; debug = true; timeout = 3000; interval = 1} in
  let cbs = {
    on_open = None;
    on_close = None;
    on_error = None;
    on_message = Some ( fun socket conf ev -> Js.log ev )
  } in init_socket uri config cbs

let () = main ()