// **************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under *
// * GNU General Public License: http://www.gnu.org/licenses/gpl.html       *
// * Copyright (C) ZenJu (zenju AT gmx DOT de) - All Rights Reserved        *
// **************************************************************************

#ifndef SMART_COM_PTR_H
#define SMART_COM_PTR_H

#include <algorithm>
#include "win.h" //includes "windows.h" -> always include before other headers that also might include "windows.h"!
#include <Objbase.h>

namespace zen
{
/*
ComPtr: RAII class handling COM objects

Example:
--------
    ComPtr<IUPnPDeviceFinder> devFinder;
	if (FAILED(::CoCreateInstance(CLSID_UPnPDeviceFinder,
                          nullptr,
                          CLSCTX_ALL,
                          IID_PPV_ARGS(devFinder.init()))))
					  return -1;

	ComPtr<IEnumUnknown> devEnum = com_dynamic_cast<IEnumUnknown>(devColl);
	if (!devEnum)
		return -1;
*/

template <class T>
class ComPtr
{
public:
    ComPtr() : ptr(nullptr) {}

    ComPtr(const ComPtr&  other) : ptr(other.ptr) { if (ptr) ptr->AddRef(); }
    ComPtr(      ComPtr&& other) : ptr(other.ptr) { other.ptr = nullptr; }

    ~ComPtr() { if (ptr) ptr->Release(); }

    ComPtr& operator=(ComPtr other) { swap(other); return *this; } //unifying assignment: no need for r-value reference assignment!

    void swap(ComPtr& rhs) { std::swap(ptr, rhs.ptr); } //throw()

    T** init() //get pointer for use with ::CoCreateInstance()
    {
        ComPtr<T>().swap(*this);
        return &ptr;
    }

    T* get() const { return ptr; }

    T* operator->() const { return ptr; }
    T& operator* () const { return *ptr; }

    T* release() //throw()
    {
        T* tmp = ptr;
        ptr = nullptr;
        return tmp;
    }

private:
    T* ptr;

    struct ConversionToBool { int dummy; };
public:
    //use member pointer as implicit conversion to bool (C++ Templates - Vandevoorde/Josuttis; chapter 20)
    operator int ConversionToBool::* () const { return ptr != nullptr ? &ConversionToBool::dummy : nullptr; }
};


template <class S, class T>
ComPtr<S> com_dynamic_cast(const ComPtr<T>& other); //throw()






















//################# implementation #############################

//we cannot specialize std::swap() for a class template and are not allowed to overload it => offer swap in own namespace
template <class T> inline
void swap(zen::ComPtr<T>& lhs, zen::ComPtr<T>& rhs)
{
    lhs.swap(rhs);
}


template <class S, class T> inline
ComPtr<S> com_dynamic_cast(const ComPtr<T>& other) //throw()
{
    ComPtr<S> outPtr;
    if (other)
        other->QueryInterface(IID_PPV_ARGS(outPtr.init()));
    return outPtr;
}
}

#endif //SMART_COM_PTR_H