#ifndef __SINGLETON_H
#define __SINGLETON_H

#include "ScopedPtr.hpp"
#include "NonCopyable.hpp"
#include "UtilExportable.hpp"
#include "Noreturn.hpp"

#include <cstdlib>
#include <stdexcept>

#define DECLARE_SINGLETON( T ) \
	friend class Singleton< T >; \
	friend class scopedPtr< T >;

#define DEFINE_SINGLETON( T ) \
	template class Singleton< T >;
	
template< class T >
class Singleton : private noncopyable
{
	public:
		static UTIL_DLL_VISIBLE T& instance( )
		{
			if( destroyed ) {
				onDeadReference( );
			}
			
			if( t == 0 ) {
				create( );
			}
			
			return *t;
		}
	
	protected:
		Singleton( )
		{
		}
		
		virtual ~Singleton( )
		{
			destroyed = true;
		}
				
	private:
		static void create( )
		{
			t.reset( new T );
		}
		
		static void onDeadReference( ) CRAWLER_NORETURN
		{
			throw std::runtime_error( "singleton has already been destroyed!" );
		}
	
		static scopedPtr<T> t;
		static bool destroyed;
};

template< class T > scopedPtr<T> Singleton<T>::t( 0 );
template< class T > bool Singleton<T>::destroyed( false );

#endif