let tile_size = 40

let width = 835

let height = 635

let canvas = Jv.get Jv.global "canvas"

let context = Jv.call canvas "getContext" [| Jv.of_string "2d" |]

let init_bg () =
  Jv.set canvas "width" (Jv.of_int width);
  Jv.set canvas "height" (Jv.of_int height);
  Jv.set context "fillStyle" (Jv.of_string "#FF1188");
  Jv.call context "fillRect"
    [| Jv.of_int 0; Jv.of_int 0; Jv.of_int width; Jv.of_int height |]

let window = Jv.get Jv.global "window"

let () =
  let (_ : Jv.t) =
    Jv.call window "addEventListener" [| Jv.of_string "load"; Jv.repr init_bg |]
  in
  ()

let tiles_per_w = width / tile_size

let tiles_per_h = height / tile_size

let orig_x = (width - (tiles_per_w * tile_size)) / 2

let orig_y = (height - (tiles_per_h * tile_size)) / 2

let grass = Jv.get Jv.global "grass"

let draw_background () =
  for x = 0 to tiles_per_w - 1 do
    for y = 0 to tiles_per_h - 1 do
      let (_ : Jv.t) =
        Jv.call context "drawImage"
          [| grass
           ; Jv.of_int (orig_x + (x * tile_size))
           ; Jv.of_int (orig_y + (y * tile_size))
          |]
      in
      ()
    done
  done

let () =
  let (_ : Jv.t) =
    Jv.call window "addEventListener"
      [| Jv.of_string "load"; Jv.repr draw_background |]
  in
  ()