#import "base.kl"
#import "os_windows.kl"
#import "kernel32.kl"
#import "gdi32.kl"
#import "user32.kl"
#import "winmm.kl"

Vec2I :: struct;; x: S64; y: S64
Vec2  :: struct;; x: F32; y: F32

Windows_Bitmap :: struct
  size: Vec2I
  data: *U32
  hdc: HDC
  dib: HBITMAP

Bitmap :: struct
  size: Vec2I
  data: *U32

create_bitmap :: (size: Vec2I, bottom_up: Bool = true): Windows_Bitmap
  result: Windows_Bitmap = {size = size}
  if bottom_up == false
    result.size.y = -result.size.y

  bminfo := BITMAPINFO{
    BITMAPINFOHEADER{
      biSize          = 40, // @todo!!! size_of(BITMAPINFOHEADER),
      biWidth         = size.x->LONG,
      biHeight        = size.y->LONG,
      biPlanes        = 1,
      biBitCount      = 32,
      biCompression   = BI_RGB,
      biXPelsPerMeter = 1,
      biYPelsPerMeter = 1,
    }
  }

  hdc := GetDC(0)
  result.dib = CreateDIBSection(hdc, &bminfo, DIB_RGB_COLORS, (&result.data)->**void, 0, 0)
  result.hdc = CreateCompatibleDC(hdc)
  return result

app_is_running := true
window_procedure :: (hwnd: HWND, msg: UINT, wparam: WPARAM, lparam: LPARAM): LRESULT
  if msg == WM_DESTROY
    PostQuitMessage(0)
    app_is_running = false
    return 0
  else;; return DefWindowProcW(hwnd, msg, wparam, lparam)

_gcvt :: #foreign (value: F64, digits: int, buffer: *char): *char
print_float :: (value: F64)
  buff: [100]char
  _gcvt(value, 10, &buff[0])
  OutputDebugStringA("\n")
  OutputDebugStringA(&buff[0])

WinMain :: (hInstance: HINSTANCE, hPrevInstance: HINSTANCE, lpCmdLine: LPSTR, nShowCmd: int): int
  if good_scheduling := false, timeBeginPeriod(1) == TIMERR_NOERROR
    good_scheduling = true

  char_info := get_type_info(5)
  assert(char_info.kind == Type_Info_Kind.CHAR)

  arena: Arena
  window_name := string_to_string16(&arena, "Have a wonderful day! 豈 更 車 賈 滑 串 句 龜 ")
  w := WNDCLASSW{
    lpfnWndProc   = window_procedure,
    hInstance     = hInstance,
    lpszClassName = window_name.str,
  }
  assert(RegisterClassW(&w) != 0)

  screen_size: Vec2I = {1280, 720}
  window := CreateWindowExW(
    dwExStyle = 0, hWndParent = 0, hMenu = 0, lpParam = 0,
    X = CW_USEDEFAULT, Y = CW_USEDEFAULT, nWidth = screen_size.x->int, nHeight = screen_size.y->int,
    lpClassName = window_name.str,
    lpWindowName = window_name.str,
    dwStyle = WS_OVERLAPPEDWINDOW,
    hInstance = hInstance
  )
  assert(window != 0)
  ShowWindow(window, nShowCmd)

  window_dc := GetDC(window)
  bitmap := create_bitmap(screen_size)

  requested_time_per_frame := 1.0 / 60.0
  frame_start_time := time()
  frame_number: S64
  total_time: F64
  for app_is_running
    msg: MSG
    for PeekMessageW(&msg, window, 0, 0, PM_REMOVE) > 0
      TranslateMessage(&msg)
      DispatchMessageW(&msg)

    for y := 0, y < bitmap.size.y, y+=1
      for x := 0, x < bitmap.size.x, x+=1
        bitmap.data[x + y*bitmap.size.x] = 0xFFFF0000

    SelectObject(bitmap.hdc, bitmap.dib)
    BitBlt(window_dc, 0, 0, (bitmap.size.x)->int, (bitmap.size.y)->int, bitmap.hdc, 0, 0, SRCCOPY)


    frame_time := time() - frame_start_time
    print_float(frame_time)
    if frame_time < requested_time_per_frame
      if good_scheduling
        time_to_sleep := (requested_time_per_frame - frame_time) * 1000
        if time_to_sleep > 0
          time_to_sleep_dword := time_to_sleep->DWORD
          // @check if time_to_sleep_dword truncates down
          Sleep(time_to_sleep_dword)

        new_frame_time := time()
        for new_frame_time < requested_time_per_frame
          new_frame_time = time() - frame_start_time

        frame_time = new_frame_time
        frame_number += 1
        total_time += frame_time