/*
**  ClanLib SDK
**  Copyright (c) 1997-2015 The ClanLib Team
**
**  This software is provided 'as-is', without any express or implied
**  warranty.  In no event will the authors be held liable for any damages
**  arising from the use of this software.
**
**  Permission is granted to anyone to use this software for any purpose,
**  including commercial applications, and to alter it and redistribute it
**  freely, subject to the following restrictions:
**
**  1. The origin of this software must not be misrepresented; you must not
**     claim that you wrote the original software. If you use this software
**     in a product, an acknowledgment in the product documentation would be
**     appreciated but is not required.
**  2. Altered source versions must be plainly marked as such, and must not be
**     misrepresented as being the original software.
**  3. This notice may not be removed or altered from any source distribution.
**
**  Note: Some of the libraries ClanLib may link to may have additional
**  requirements or restrictions.
**
**  File Author(s):
**
**    Magnus Norddahl
*/


#pragma once

#include <memory>

namespace clan
{
/// \addtogroup clanCore_System clanCore System
/// \{

class UserDataBase
{
public:
	virtual ~UserDataBase() { }
};

template<typename T>
class UserData : public UserDataBase
{
public:
	UserData(const std::shared_ptr<T> &data) : data(data) { }
	std::shared_ptr<T> data;
};

/// \brief Helper class to store any shared_ptr as user data on an object.
class UserDataOwner
{
public:
	UserDataOwner()
	: user_data(nullptr)
	{
	}

	~UserDataOwner()
	{
		if (user_data)
		{
			user_data->~UserDataBase();
			user_data = nullptr;
		}
	}

	template<typename T>
	void set_data(const std::shared_ptr<T> &data)
	{
		if (user_data)
		{
			user_data->~UserDataBase();
			user_data = nullptr;
		}

		static_assert(sizeof(UserData<T>) <= 32, "userdata_storage is too small!");
		user_data = new(userdata_storage) UserData<T>(data);
	}
  
	template<typename T>
	std::shared_ptr<T> get_data()
	{
		UserData<T> *d = dynamic_cast<UserData<T> *>(user_data);
		if (d)
		{
			return d->data;
		}
		else
		{
			return std::shared_ptr<T>();
		}
	}
  
private:
	UserDataOwner(const UserDataOwner &that); // do not implement
	UserDataOwner &operator=(const UserDataOwner &that); // do not implement

	UserDataBase *user_data;
	char userdata_storage[32];
};

}
