// #import "base.kl"
#load "gdi32.kl"
#load "user32.kl"

String16 :: struct;; str: *U16; len: S64
String32 :: struct;; str: *U32; len: S64
UTF32_Result :: struct
  out_str: U32
  advance: S64
  error  : S32
UTF16_Result :: struct
  out_str: [2]U16
  len    : S32
  error  : S32

utf8_to_utf32 :: (c: *U8, max_advance: S64): UTF32_Result
  result: UTF32_Result
  if (c[0] & 0b10000000) == 0
    if max_advance >= 1
      c0 := c[0]->U32
      result.out_str = c0
      result.advance = 1
    else;; result.error = 1

  elif (c[0] & 0b11100000) == 0b11000000
    if (c[1] & 0b11000000) == 0b10000000 // Continuation byte required
      if max_advance >= 2
        c0 := c[0]->U32; c1 := c[1]->U32
        result.out_str = (c0 & 0b00011111) << 6 | (c1 & 0b00111111)
        result.advance = 2
      else;; result.error = 2
    else;; result.error = 2

  elif (c[0] & 0b11110000) == 0b11100000
    if (c[1] & 0b11000000) == 0b10000000 && (c[2] & 0b11000000) == 0b10000000 // Two continuation bytes required
      if max_advance >= 3
        c0 := c[0]->U32; c1 := c[1]->U32; c2 := c[2]->U32
        result.out_str = (c0 & 0b00001111) << 12 | (c1 & 0b00111111) << 6 | (c2 & 0b00111111)
        result.advance = 3
      else;; result.error = 3
    else;; result.error = 3

  elif (c[0] & 0b11111000) == 0b11110000
    if (c[1] & 0b11000000) == 0b10000000 && (c[2] & 0b11000000) == 0b10000000 && (c[3] & 0b11000000) == 0b10000000 // Three continuation bytes required
      if max_advance >= 4
        c0 := c[0]->U32; c1 := c[1]->U32; c2 := c[2]->U32; c3 := c[3]->U32
        result.out_str = (c0 & 0b00001111) << 18 | (c1 & 0b00111111) << 12 | (c2 & 0b00111111) << 6 | (c3 & 0b00111111)
        result.advance = 4
      else;; result.error = 4
    else;; result.error = 4
  else;; result.error = 4

  return result

utf32_to_utf16 :: (codepoint: U32): UTF16_Result
  result: UTF16_Result
  if codepoint < 0x10000
    result.out_str[0] = codepoint->U16
    result.out_str[1] = 0
    result.len = 1
  elif codepoint <= 0x10FFFF
    code: U32 = (codepoint - 0x10000)
    result.out_str[0] = (0xD800 | (code >> 10))->U16
    result.out_str[1] = (0xDC00 | (code & 0x3FF))->U16
    result.len = 2
  else
    result.error = 1

  return result

// string_to_string16 :: (allocator: *Allocator, int: String): String16
//   String16 result = {exp_alloc_array(allocator, U16, (in.len*2)+1)}; // @Note(Krzosa): Should be more then enough space
//   for(S64 i = 0; i < in.len;){
//     UTF32_Result decode = utf8_to_utf32(in.str + i, in.len - i);
//     if(!decode.error){
//       i += decode.advance;
//       UTF16_Result encode = utf32_to_utf16(decode.out_str);
//       if(!encode.error){
//         for(S32 j = 0; j < encode.len; j++){
//           result.str[result.len++] = encode.out_str[j];
//         }
//       }
//       else unicode_error(question_mark16);
//     }
//     else unicode_error(question_mark16);
//   }

//   result.str[result.len] = 0;
//   return result;
// }

Vec2I :: struct;; x: S32; y: S32
Vec2  :: struct;; x: F32; y: F32
Windows_Bitmap :: struct
  size: Vec2I
  data: *U32
  hdc: HDC
  dib: HBITMAP

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          = 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


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

main :: (argc: int, argv: **char): int
  bitmap := create_bitmap({1280, 720})
  result := utf8_to_utf32(&"A"[0], 1)
  assert(result.out_str == 'A, "Invalid decode")
  result  = utf8_to_utf32(&"ć"[0], 2)
  result  = utf8_to_utf32(&"ó"[0], 2)