module Repr = Layer.CanvaPrinter

type t = Point.t

type 'a repr =
  { back: ('a Repr.t -> 'a Repr.t)
  ; path: ('a Repr.t)
  ; last_point : Point.t option
  }

let create_path
  : unit -> 'a repr
  = fun () ->
    { back = Repr.close
    ; path = Repr.create ()
    ; last_point = None
    }

(* Start a new path. *)
let start
  : Point.t -> 'a repr -> 'a repr
  = fun t {back; path; _} ->
    let path = Repr.move_to (Point.get_coord t) path in
    let line' = Repr.line_to (Point.get_coord' t) in
    { back = (fun p -> back @@ line' p)
    ; path
    ; last_point = Some t
    }

let line_to
  : Point.t -> Point.t -> 'a repr -> 'a repr
  = fun _ t {back; path; _} ->
    let line' = Repr.line_to (Point.get_coord' t) in
    { back = (fun t -> back @@ line' t)
    ; path = Repr.line_to (Point.get_coord t) path
    ; last_point = Some t
    }

let quadratic_to
  : Point.t -> Gg.v2 -> Gg.v2 -> Point.t -> 'a repr -> 'a repr
  = fun p0 ctrl0 ctrl1 p1 t ->

    let ctrl0' = Point.copy p1 ctrl0
    and ctrl1' = Point.copy p1 ctrl1 in

    let line' path =
      Repr.quadratic_to
        (Point.get_coord' @@ ctrl1')
        (Point.get_coord' ctrl0')
        (Point.get_coord' p0) path in

    let path = Repr.quadratic_to
        (Point.get_coord ctrl0')
        (Point.get_coord ctrl1')
        (Point.get_coord p1)
        t.path in
    { back = (fun p -> t.back @@ line' p)
    ; path
    ; last_point = Some p1
    }

let stop
  : 'a repr -> 'a repr
  = fun {back; path; last_point} ->

    let path =
      match last_point with
      | Some point -> Repr.line_to (Point.get_coord' point) path
      | None -> path in

    { back = (fun x -> x)
    ; path = back path
    ; last_point = None }

let get
  : 'a repr -> 'a Repr.t
  = fun {back; path; _} ->
    back path