open StdLabels
open Js_of_ocaml

type message = [
  | `Complete of (int * (Path.Fixed.path array))
  | `DeletePoint of (int * Path.Point.t * Path.Fixed.t)
]

exception Empty_Element

let get_point
  : Path.Fixed.path -> Gg.v2
  = function
    | Empty -> raise Empty_Element
    | Line (_, p1) -> Path.Point.get_coord p1
    | Curve bezier -> Path.Point.get_coord bezier.Path.Fixed.p1

let first_point
  : Path.Fixed.path -> Gg.v2
  = function
    | Empty -> raise Empty_Element
    | Line (p0, _) -> Path.Point.get_coord p0
    | Curve bezier -> Path.Point.get_coord bezier.Path.Fixed.p0

let assoc_point
  : Shapes.Bezier.t -> Path.Fixed.path -> Path.Fixed.path
  = fun bezier -> function
    | Empty -> raise Empty_Element
    | Line (p0, p1)
    | Curve {p0; p1; _} ->
      let p0' = Path.Point.copy p0 bezier.Shapes.Bezier.p0
      and p1' = Path.Point.copy p1 bezier.Shapes.Bezier.p1 in
      Curve
        { Path.Fixed.p0 = p0'
        ; Path.Fixed.p1 = p1'
        ; Path.Fixed.ctrl0 = bezier.Shapes.Bezier.ctrl0
        ; Path.Fixed.ctrl1 = bezier.Shapes.Bezier.ctrl1
        }

let rebuild (id, paths) =
  (* Convert all the points in list *)
  let points = List.init
      ~len:((Array.length paths) )
      ~f:(fun i -> get_point (Array.get paths i)) in
  let p0 = first_point (Array.get paths 0)in

  let points = p0::points in

  (* We process the whole curve in a single block *)
  begin match Shapes.Bspline.to_bezier points with
    | Error `InvalidPath -> ()
    | Ok beziers ->

      (* Now for each point, reassociate the same point information,
         We should have as many points as before *)
      let rebuilded = Array.map2 beziers paths ~f:assoc_point in
      Worker.post_message (`Complete (id, rebuilded))
  end

let execute (command: [> message]) =
  match command with
  | `Complete (id, paths) ->
    rebuild (id, paths)
  | `DeletePoint (id, point, path) ->
    let path = Path.Fixed.remove_point path point in
    (* TODO Handle when there are less than 4 points *)
    rebuild (id, Path.Fixed.path path)
  | any ->
    Worker.post_message (`Other any)

let () =
  Worker.set_onmessage execute