open Js_of_ocaml
open Js_of_ocaml_lwt

(** Event generated once the library has created the svg image *)
let (generated_svg_event:(Dom_svg.svgElement Js.t * Js.js_string Js.t) Dom.Event.typ)
  = Dom_html.Event.make "generated_svg"

(* Save the generated image *)
let on_result_png image = begin
  let a = Dom_html.createA Dom_html.document in
  a##.href := image##.src;
  Js.Unsafe.set a (Js.string "download") (Js.string "output.png");
  Dom.appendChild Dom_html.document##.body a;
  a##click;
  Dom.removeChild Dom_html.document##.body a
end

let on_result_svg
  : Dom_html.element Js.t -> (Dom.node Js.t) -> unit
  = fun svg_display image -> begin
      let childNodes = svg_display##.childNodes in
      for i = 0 to childNodes##.length do
        Js.Opt.iter (childNodes##item i) (fun elem -> ignore @@ svg_display##removeChild elem)
      done;
      Dom.appendChild svg_display image;
      ()
    end

(** Message send by the worker *)
type message = Process.t
type worker = (Js.js_string Js.t, message) Worker.worker Js.t

let change_event (worker:worker) input _ev _ = begin
  let text: Js.js_string Js.t = input##.value in

  (* Send the content to the worker *)
  let () = worker##postMessage text in
  Lwt.return_unit
end

class type _Dom_parser = object
  method parseFromString: Js.js_string Js.t -> Js.js_string Js.t -> Dom_html.document Js.t Js.meth
end

let dom_parser = (Js.Unsafe.global##._DOMParser)
let dom_parser = new%js dom_parser

let load () =

  (* The URL is be relative with the page location. If the worker is called
     from diffenent location, it becomes mandatory to declare the URL as
     absolute. *)
  let (worker:worker) = Worker.create "/resources/viz.js/worker.js" in

  worker##.onmessage := Dom.handler (fun (event: message Worker.messageEvent Js.t) ->
      let gv, image = event##.data in
      let image = dom_parser##parseFromString image "image/svg+xml" in
      let image = image##.documentElement in

      let _ = Dispatch.call generated_svg_event (image, gv) in
      Js._true);

  let svg_display = Dom_html.getElementById_exn "svg"
  and output_button = Dom_html.getElementById_exn "png_output"
  and dot_button = Dom_html.getElementById_exn "dot_output"
  and editor = Dom_html.getElementById_exn "editor" in

  ignore @@ Dispatch.register generated_svg_event (fun (image, input) ->

      on_result_svg svg_display (image :> Dom.node Js.t);

      (* Download the dot file *)
      dot_button##.onclick := Dom_html.handler (fun _ev ->
          let _ = Elements.Transfert.send
              ~mime_type:(Jstr.v "text/plain")
              ~filename:(Jstr.v "output.dot")
              (Obj.magic input) in
          Js._false
        );

      (* Convert the svg in png *)
      output_button##.onclick := Dom_html.handler (fun _->
          (*download image*)
          CanvasTool.generate_png image (fun image ->
              let _ =
                Elements.Transfert.send_raw
                  ~filename:(Jstr.v "output.png")
                  (Obj.magic image) in
              ()
            );
          Js._false
        );
    );

  Js.Opt.iter (Dom_html.CoerceTo.textarea editor) (fun input ->
      Lwt_js_events.async (fun () -> (Lwt_js_events.limited_loop Lwt_js_events.change ~elapsed_time:0.1 editor (change_event worker input) ));
      Lwt_js_events.async (fun () -> (Lwt_js_events.limited_loop  Lwt_js_events.input ~elapsed_time:0.1 editor (change_event worker input) ));
      (* Run the first generation *)
      Lwt.ignore_result (change_event worker input () ());
    );

  (** Handle the separation window *)
  Option.iter
    (fun button ->
       let _ = Dom_events.listen button Dom_html.Event.click (fun _ _ ->

           let opt_window2 = Dom_html.window##open_
               (Js.string "")
               (Js.string "_image")
               Js.Opt.empty in

           Js.Opt.iter opt_window2 (fun window2 ->

               let callback
                 : Dom_svg.svgElement Js.t * Js.js_string Js.t -> unit
                 = fun (image, _gv)  -> begin
                     let node2 = image##cloneNode Js._true in
                     let () = on_result_svg window2##.document##.body
                         (node2 :> Dom.node Js.t) in
                     ()
                   end in
               let handler = Dispatch.register generated_svg_event callback in

               (* Remove the update event when the window is closed *)
               window2##.onunload := Dom_html.handler (fun _ev ->
                   Dispatch.remove generated_svg_event handler;
                   Js._false
                 );

               (* Copy the current display to the new window *)
               let childNodes = svg_display##.childNodes in
               for i = 0 to childNodes##.length do
                 Js.Opt.iter
                   (childNodes##item i)
                   (fun elem ->
                      Dom.appendChild window2##.document##.body (elem##cloneNode Js._true)
                   )
               done;
             );

           false
         ) in
       ()
    )
    (Dom_html.getElementById_opt "btn_window");
  Lwt.return Js._false

let _ = Lwt.bind (Lwt_js_events.onload ()) (fun _ -> load())

let _ =
  Js.export "generator"
    (object%js
      method load = load ()
    end)