let () = Random.self_init ()

module Map = struct
  type background =
    | Grass
    | Water
    | Black

  let width = 1000

  let height = 1000

  let player_pos = ref (20, 3)

  let m =
    Array.init width (fun _x ->
        Array.init height (fun _y ->
            if Random.int 1000 <= 42 then Water else Grass ) )

  let get_tile_kind ~x ~y = try m.(x).(y) with Invalid_argument _ -> Black
end

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 papy_bottom = Jv.get Jv.global "papy_bottom"

let water = Jv.get Jv.global "water"

let draw_map () =
  let player_x, player_y = !Map.player_pos in
  Format.printf "player_x = %d@\nplayer_y = %d@\n" player_x player_y;
  for x = 0 to tiles_per_w - 1 do
    let mapx = x + player_x - (tiles_per_w / 2) in
    for y = 0 to tiles_per_h - 1 do
      let mapy = y + player_y - (tiles_per_h / 2) in
      let img =
        match Map.get_tile_kind ~x:mapx ~y:mapy with
        | Grass -> grass
        | Water -> water
        | Black -> water
      in
      let (_ : Jv.t) =
        Jv.call context "drawImage"
          [| img
           ; Jv.of_int (orig_x + (x * tile_size))
           ; Jv.of_int (orig_y + (y * tile_size))
          |]
      in
      ()
    done
  done;
  let (_ : Jv.t) =
    Jv.call context "drawImage"
      [| papy_bottom; Jv.of_int (width / 2); Jv.of_int (height / 2) |]
  in
  ()

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

let kb_handler e =
  let x, y = !Map.player_pos in
  let x, y =
    match Jv.to_string @@ Jv.get e "key" with
    | "z" -> (x, y - 1)
    | "q" -> (x - 1, y)
    | "s" -> (x, y + 1)
    | "d" -> (x + 1, y)
    | _s -> (x, y)
  in
  let x = max 0 x in
  let x = min (Map.width - 1) x in
  let y = max 0 y in
  let y = min (Map.height - 1) y in
  Map.player_pos := (x, y);
  draw_map ()

let bind_keys () =
  Jv.call window "addEventListener"
    [| Jv.of_string "keydown"; Jv.repr kb_handler |]

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

(*
  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
  ()

let draw_papy () =
  let (_ : Jv.t) =
    Jv.call context "drawImage"
      [| papy_bottom
       ; Jv.of_int ((width / 2) - (tile_size / 2))
       ; Jv.of_int ((height / 2) - (tile_size / 2))
      |]
  in
  ()

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

*)