#include <Windows.h>
#include <GL/glcorearb.h>
#include <GL/wgl.h>
#include <GL/wglext.h>
#include <sstream>

PFNWGLGETPROCADDRESSPROC wglGetProcAddressDYN;
PFNWGLCREATECONTEXTPROC wglCreateContextDYN;
PFNWGLMAKECURRENTPROC wglMakeCurrentDYN;
PFNSWAPBUFFERSPROC wglSwapBuffersDYN;
PFNWGLDELETECONTEXTPROC wglDeleteContextDYN;

PFNWGLGETEXTENSIONSSTRINGARBPROC wglGetExtensionsStringARB;
PFNWGLCHOOSEPIXELFORMATARBPROC wglChoosePixelFormatARB;
PFNWGLCREATECONTEXTATTRIBSARBPROC wglCreateContextAttribsARB;

//=============================================================================
template< typename T >
void GetProc( HMODULE mod, PFNWGLGETPROCADDRESSPROC wglProcAddress, const char* name, T* out )
{
    *out = nullptr;
    if( wglProcAddress )
        *out = reinterpret_cast< T >( wglProcAddress( name ) );
    if( !*out )
        *out = reinterpret_cast< T >( GetProcAddress( mod, name ) );
}

//=============================================================================
void GetExtensionFunctions( const HINSTANCE instance )
{
    const LPCSTR name = TEXT("dummy-window");
    WNDCLASS wndclass;
    ZeroMemory( &wndclass, sizeof( wndclass ) );
    wndclass.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
    wndclass.lpfnWndProc = DefWindowProc;
    wndclass.hInstance = instance;
    wndclass.lpszClassName = name;
    RegisterClass( &wndclass );

    const HWND wnd = CreateWindow( name, "", WS_DISABLED, 0, 0, 1, 1, NULL, NULL, instance, NULL );
    const HDC dc = GetDC( wnd );
        
    PIXELFORMATDESCRIPTOR pfd;
    ZeroMemory( &pfd, sizeof( pfd ) );
    pfd.nSize = sizeof( pfd );
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 24;
    pfd.iLayerType = PFD_MAIN_PLANE;
    const int iPixelFormat = ChoosePixelFormat( dc, &pfd );
    SetPixelFormat( dc, iPixelFormat, NULL );

    const HMODULE mod = LoadLibrary( TEXT("opengl32.dll") );

    GetProc( mod, NULL, "wglGetProcAddress", &wglGetProcAddressDYN );
    GetProc( mod, NULL, "wglCreateContext", &wglCreateContextDYN );
    GetProc( mod, NULL, "wglMakeCurrent", &wglMakeCurrentDYN );
    GetProc( mod, NULL, "wglSwapBuffers", &wglSwapBuffersDYN );
    GetProc( mod, NULL, "wglDeleteContext", &wglDeleteContextDYN );

    const HGLRC rc = wglCreateContextDYN( dc );
    wglMakeCurrentDYN( dc, rc );

    GetProc( mod, wglGetProcAddressDYN, "wglGetExtensionsStringARB", &wglGetExtensionsStringARB );
    GetProc( mod, wglGetProcAddressDYN, "wglChoosePixelFormatARB", &wglChoosePixelFormatARB );
    GetProc( mod, wglGetProcAddressDYN, "wglCreateContextAttribsARB", &wglCreateContextAttribsARB );

    FreeLibrary( mod );

    wglMakeCurrentDYN( dc, NULL );
    wglDeleteContextDYN( rc );
    ReleaseDC( wnd, dc );
    DestroyWindow( wnd );
    UnregisterClass( name, instance );
}

//=============================================================================
int WINAPI WinMain( HINSTANCE instance, HINSTANCE prvInstance, PSTR cmdLine, int cmdShow )
{
    GetExtensionFunctions( instance );

    const LPCSTR name = TEXT("OpenGLWindow");
    WNDCLASS wndclass;
    ZeroMemory( &wndclass, sizeof( wndclass ) );
    wndclass.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
    wndclass.lpfnWndProc = DefWindowProc;
    wndclass.hInstance = instance;
    wndclass.lpszClassName = name;
    RegisterClass( &wndclass );

    const HWND wnd = CreateWindow( name, "", WS_OVERLAPPEDWINDOW, 0, 0, 1, 1, NULL, NULL, instance, NULL );
    const HDC dc = GetDC( wnd );
        
    int format = 0;
    UINT numFormats = 0;
    int pixel_attributes[] =
    {
        WGL_SUPPORT_OPENGL_ARB, TRUE,
        WGL_DOUBLE_BUFFER_ARB, TRUE,
    #if 1
        WGL_SWAP_METHOD_ARB, WGL_SWAP_UNDEFINED_ARB,
    #else
        WGL_SWAP_METHOD_ARB, WGL_SWAP_COPY_ARB,
    #endif
        0
    };
    wglChoosePixelFormatARB( dc, pixel_attributes, NULL, 1, &format, &numFormats );

    std::stringstream ss;
    ss << "numFormats: " << numFormats << std::endl;
    MessageBox( wnd, ss.str().c_str(), "Message", MB_OK ); 

    ReleaseDC( wnd, dc );
    DestroyWindow( wnd );
    UnregisterClass( name, instance );
    return 0;
}