require 'alien'

WS_OVERLAPPED       = 0x00000000
WS_CAPTION          = 0x00C00000
WS_SYSMENU          = 0x00080000
WS_THICKFRAME       = 0x00040000
WS_MINIMIZEBOX      = 0x00020000
WS_MAXIMIZEBOX      = 0x00010000 
WS_OVERLAPPEDWINDOW = WS_OVERLAPPED + WS_CAPTION + WS_SYSMENU + WS_THICKFRAME + WS_MINIMIZEBOX + WS_MAXIMIZEBOX

WM_DESTROY    = 0x0002
WM_SIZE       = 0x0005
WM_CLOSE      = 0x0010
WM_PAINT      = 0x000F

CW_USEDEFAULT = 0x80000000
SW_SHOWNORMAL = 1

BLACK_BRUSH   = 4
COLOR_WINDOW  = 5

POINTAPI = alien.defstruct{
    {"x", "long"};
    {"y", "long"};
}

MSG = alien.defstruct{
    {"hwnd", "pointer"};
    {"message", "uint"};
    {"wParam", "pointer"};
    {"lParam", "pointer"};
    {"time", "ulong"};
    {"x", "long"};
    {"y", "long"};
}

WNDCLASSEX = alien.defstruct{
    {"cbSize", "uint"};
    {"style", "uint"};
    {"lpfnWndProc", "callback"};
    {"cbClsExtra", "int"};
    {"cbWndExtra", "int"};
    {"hInstance", "pointer"};
    {"hIcon", "pointer"};
    {"hCursor", "pointer"};
    {"hbrBackground", "pointer"};
    {"lpszMenuName", "string"};
    {"lpszClassName", "string"};
    {"hIconSm", "pointer"};
}

RECT = alien.defstruct{
    {"Left", "long"};
    {"Top", "long"};
    {"Right", "long"};
    {"Bottom", "long"};
}

PAINTSTRUCT = alien.defstruct{
  {"hdc", "uint"};
  {"fErase", "int"};
  {"rcPaint_left", "long"};
  {"rcPaint_top", "long"};
  {"rcPaint_right", "long"};
  {"rcPaint_bottom", "long"};
  {"fRestore", "int"};
  {"fIncUpdate", "int"};
  --[[ {"rgbReserved", "byte[32]"}; ]]
}
PAINTSTRUCT.size = PAINTSTRUCT.size + 32

RegisterClassEx  = alien.user32.RegisterClassExA; RegisterClassEx:types{ ret = "ushort", abi = "stdcall"; "pointer" }
DestroyWindow    = alien.user32.DestroyWindow;    DestroyWindow:types{ ret = "int", abi = "stdcall"; "pointer" }
PostQuitMessage  = alien.user32.PostQuitMessage;  PostQuitMessage:types{ ret = "void", abi = "stdcall"; "int" }
DefWindowProc    = alien.user32.DefWindowProcA;   DefWindowProc:types{ ret = "long", abi = "stdcall"; "pointer", "uint", "uint", "long" }
GetMessage       = alien.user32.GetMessageA;      GetMessage:types{ ret = "int", abi = "stdcall"; "pointer", "pointer", "uint", "uint" }
TranslateMessage = alien.user32.TranslateMessage; TranslateMessage:types{ ret = "int", abi = "stdcall"; "pointer" }
DispatchMessage  = alien.user32.DispatchMessageA; DispatchMessage:types{ ret = "int", abi = "stdcall"; "pointer" }
CreateWindowEx   = alien.user32.CreateWindowExA;  CreateWindowEx:types{ ret = "pointer", abi = "stdcall"; "ulong", "string", "string", "ulong", "int", "int", "int", "int", "pointer", "pointer", "pointer" }
ShowWindow       = alien.user32.ShowWindow;       ShowWindow:types{ ret = "int", abi = "stdcall"; "pointer", "int" }
UpdateWindow     = alien.user32.UpdateWindow;     UpdateWindow:types{ ret = "int", abi = "stdcall"; "pointer" }
BeginPaint       = alien.user32.BeginPaint;       BeginPaint:types{ ret = "pointer", abi = "stdcall"; "pointer", "pointer" }
EndPaint         = alien.user32.EndPaint;         EndPaint:types{ ret = "int", abi = "stdcall"; "long", "pointer" }
TextOut          = alien.gdi32.TextOutA;          TextOut:types{ ret = "int", abi = "stdcall"; "pointer", "int", "int", "string", "int" }
GetStockObject   = alien.gdi32.GetStockObject;    GetStockObject:types{ ret = "pointer", abi = "stdcall"; "int" }

CLASS_NAME = "helloWindow"
WINDOW_NAME = "Hello, World"

function WndProc(hwnd, uMsg, wParam, lParam)
    ps = PAINTSTRUCT:new()
    strMessage = string.format("Hello, Win32 GUI(Lua) World!")
    if (uMsg == WM_DESTROY) then
        PostQuitMessage(0)
    elseif (uMsg == WM_PAINT) then
        hdc = BeginPaint( hwnd, ps() )
        TextOut( hdc, 0, 0, strMessage, string.len(strMessage) )
        EndPaint( hwnd, ps() )
    else
        return DefWindowProc(hwnd, uMsg, wParam, lParam)
    end
    return nil
end

function WinMain()
    wcex = WNDCLASSEX:new()
    wcex.cbSize        = WNDCLASSEX.size
    wcex.style         = 0
    wcex.lpfnWndProc   = alien.callback(WndProc, { ret = "long", abi = "stdcall"; "pointer", "uint", "uint", "long" })
    wcex.cbClsExtra    = 0
    wcex.cbWndExtra    = 0
    wcex.hInstance     = nil
    wcex.hIcon         = nil
    wcex.hCursor       = nil
    wcex.hbrBackground = GetStockObject(COLOR_WINDOW+1)
    wcex.lpszMenuName  = nil
    wcex.lpszClassName = CLASS_NAME
    wcex.hIconSm       = nil

    RegisterClassEx(wcex())

    hwnd = CreateWindowEx(
        0,
        CLASS_NAME,
        WINDOW_NAME,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        640,
        480,
        nil,
        nil,
        nil)

    ShowWindow(hwnd, SW_SHOWNORMAL)
    UpdateWindow(hwnd)

    msg = MSG:new()
    msg_ptr = msg()

    while (GetMessage(msg_ptr, nil, 0, 0) ~= 0) do
        TranslateMessage(msg_ptr)
        DispatchMessage(msg_ptr)
    end
end

function main()
    WinMain()
end

main()