// TJP COPYRIGHT HEADER

/**
 * legal header 
 *
 * ============================================================================
 * TJP	10/11/01		Got rid of the constructed singleton, it was essentially
 *		a pointer!
 *
 * @author	Timothy Prepscius
 * @created 3/../01
 */

#pragma once

#include "ThreadSafeSingleton.h"
#include "../threads/Monitor.h"

namespace timprepscius {
namespace core {

/**
 * a Singleton container, whose contained instance is constructed on its
 * first request
 *
 * T defines the class pointer type
 * X defines the allocation class type
 */

template<class T>
class ThreadSafeSingletonNoConstruct : public Monitor<T>
{
	public:
		typedef Monitor<T> Super;
		typedef typename Super::Writer Accessor;

	protected:
		// only called by reader/writer after lock
		virtual T *access() const
		{
			return this->object;
		}

	public:
		ThreadSafeSingletonNoConstruct () :
			Super(NULL)
		{
		}
	
		virtual ~ThreadSafeSingletonNoConstruct()
		{
			deleteInstance();
		}
	
		virtual void setInstance (T *instance)
		{
			Accessor w(*this);
			{
				this->object = instance;
			}
		}

		void deleteInstance()
		{
			Accessor w(*this);

			if (this->object)
				delete this->object;

			this->object = NULL;
		}
} ;

template<class T, class X=T>
class ThreadSafeSingleton : public ThreadSafeSingletonNoConstruct<T>
{
	public:
		typedef ThreadSafeSingletonNoConstruct<T> Super;
		typedef typename Super::Writer Accessor;

	protected:
		// only called by reader/writer after lock
		virtual T *access() const
		{
			if (!this->object)
			{
				const_cast<ThreadSafeSingleton<T> *>(this)->setInstance(new T());
			}
			
			return this->object;
		}

	public:
		virtual ~ThreadSafeSingleton()
		{
			Super::deleteInstance();
		}
		
		virtual void setInstance (T *instance)
		{
			Accessor a(*this);
			
			if (this->object)
				delete this->object;
		
			this->object = instance;
		}
} ;

} // namespace utilities 
} // namespace