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#ifndef NVBLASTFIXEDQUEUE_H
#define NVBLASTFIXEDQUEUE_H

#include "NvBlastAssert.h"
#include "NvBlastMemory.h"

namespace Nv
{
namespace Blast
{

/*!
FixedQueue is a queue container which is intended to be used with placement new on chunk of memory.
It'll use following memory for data layout. As follows:

// some memory
char ​*buf = new char[64 *​ 1024];

// placement new on this memory
FixedQueue<SomeClass>* arr = new (buf) FixedQueue<SomeClass>();

// you can get max requiredMemorySize by an array of 'capacity' elements count to use memory left
buf = buf + FixedQueue<SomeClass>::requiredMemorySize(capacity);

*/
template <class T>
class FixedQueue
{
public:
	explicit FixedQueue(uint32_t maxEntries) : m_num(0), m_head(0), m_tail(0), m_maxEntries(maxEntries)
	{
	}

	static size_t requiredMemorySize(uint32_t capacity)
	{
		return align16(sizeof(FixedQueue<T>)) + align16(capacity * sizeof(T));
	}

	T popFront()
	{
		NVBLAST_ASSERT(m_num>0);

		m_num--;
		T& element = data()[m_tail];
		m_tail = (m_tail+1) % (m_maxEntries);
		return element;
	}

	T front()
	{
		NVBLAST_ASSERT(m_num>0);

		return data()[m_tail];
	}

	T popBack()
	{
		NVBLAST_ASSERT(m_num>0);

		m_num--;
		m_head = (m_head-1) % (m_maxEntries);
		return data()[m_head];
	}

	T back()
	{
		NVBLAST_ASSERT(m_num>0);

		uint32_t headAccess = (m_head-1) % (m_maxEntries);
		return data()[headAccess];
	}

	bool pushBack(const T& element)
	{
		if (m_num == m_maxEntries) return false;
		data()[m_head] = element;

		m_num++;
		m_head = (m_head+1) % (m_maxEntries);

		return true;
	}

	bool empty() const
	{
		return m_num == 0;
	}

	uint32_t size() const
	{
		return m_num;
	}	


private:
	uint32_t		m_num;
	uint32_t		m_head;
	uint32_t		m_tail;
	uint32_t		m_maxEntries;

	T* data()
	{
		return (T*)((char*)this + sizeof(FixedQueue<T>));
	}

private:
	FixedQueue(const FixedQueue& that);
};

} // namespace Blast
} // namespace Nv

#endif // ifndef NVBLASTFIXEDQUEUE_H
