/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2011 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_UTILS_HPP
#define MAPNIK_UTILS_HPP

// boost
#ifdef MAPNIK_THREADSAFE
#include <boost/thread/mutex.hpp>
#endif

// stl
#include <stdexcept>
#include <cstdlib>
#include <limits>
#include <ctime>
#include <algorithm>
#include <cmath>

namespace mapnik
{
#ifdef MAPNIK_THREADSAFE
using boost::mutex;
#endif

template <typename T>
class CreateUsingNew
{
public:
    static T* create()
    {
        return new T;
    }
    static void destroy(T* obj)
    {
        delete obj;
    }
};

template <typename T>
class CreateStatic
{
private:
    union MaxAlign
    {
        char t_[sizeof(T)];
        short int shortInt_;
        int int_;
        long int longInt_;
        float float_;
        double double_;
        long double longDouble_;
        struct Test;
        int Test::* pMember_;
        int (Test::*pMemberFn_)(int);
    };

public:

    static T* create()
    {
        static MaxAlign staticMemory;
        return new(&staticMemory) T;
    }
#ifdef __SUNPRO_CC
    // Sun C++ Compiler doesn't handle `volatile` keyword same as GCC.
    static void destroy(T* obj)
#else
    static void destroy(volatile T* obj)
#endif
    {
        obj->~T();
    }
};

template <typename T,
          template <typename U> class CreatePolicy=CreateStatic> class singleton
{
#ifdef __SUNPRO_CC
    /* Sun's C++ compiler will issue the following errors if CreatePolicy<T> is used:
       Error: A class template name was expected instead of mapnik::CreatePolicy<mapnik::T>
       Error: A "friend" declaration must specify a class or function.
    */
    friend class CreatePolicy;
#else
    friend class CreatePolicy<T>;
#endif
    static T* pInstance_;
    static bool destroyed_;
    singleton(const singleton &rhs);
    singleton& operator=(const singleton&);

    static void onDeadReference()
    {
        throw std::runtime_error("dead reference!");
    }

    static void DestroySingleton()
    {
        CreatePolicy<T>::destroy(pInstance_);
        pInstance_ = 0;
        destroyed_ = true;
    }

protected:
#ifdef MAPNIK_THREADSAFE
    static mutex mutex_;
#endif
    singleton() {}
public:
    static T& instance()
    {
        if (! pInstance_)
        {
#ifdef MAPNIK_THREADSAFE
            mutex::scoped_lock lock(mutex_);
#endif
            if (! pInstance_)
            {
                if (destroyed_)
                {
                    destroyed_ = false;
                    onDeadReference();
                }
                else
                {
                    pInstance_ = CreatePolicy<T>::create();

                    // register destruction
                    std::atexit(&DestroySingleton);
                }
            }
        }
        return *pInstance_;
    }
};
#ifdef MAPNIK_THREADSAFE
template <typename T,
          template <typename U> class CreatePolicy> mutex singleton<T,CreatePolicy>::mutex_;
#endif

template <typename T,
          template <typename U> class CreatePolicy> T* singleton<T,CreatePolicy>::pInstance_=0;
template <typename T,
          template <typename U> class CreatePolicy> bool singleton<T,CreatePolicy>::destroyed_=false;

}

#endif // MAPNIK_UTILS_HPP