namespace Vanara.PInvoke
{
	/// <summary>Enumerator with zero copy access using ref.</summary>
	/// <typeparam name="T">The structure type.</typeparam>
	public unsafe ref struct RefEnumerator<T> where T : unmanaged
	{
		private T* _arrayPtr, basePtr;
		private int _index;

		/// <summary>Create RefEnumerator.</summary>
		/// <param name="arrayPtr">Pointer to unmanaged array</param>
		/// <param name="count">Number of elements in the <paramref name="arrayPtr"/></param>
		public RefEnumerator(T* arrayPtr, int count)
		{
			_arrayPtr = basePtr = arrayPtr;
			Count = count;
			_index = -1;
		}

		/// <summary>Gets the number of elements available.</summary>
		/// <value>The number of elements available.</value>
		public int Count { get; private set; }

		/// <summary>Return current element.</summary>
		public ref T Current => ref *_arrayPtr;

		/// <summary>Gets the <typeparamref name="T"/> at the specified index.</summary>
		/// <value>The <typeparamref name="T"/>.</value>
		/// <param name="index">The index.</param>
		/// <returns>A reference to <typeparamref name="T"/>.</returns>
		public ref T this[int index] => ref _arrayPtr[index];

		/// <summary>Move to next element.</summary>
		public bool MoveNext()
		{
			int index = _index + 1;
			if (index < Count)
			{
				_index = index;
				_arrayPtr++;
				return true;
			}
			return false;
		}

		/// <summary>Resets this iterator.</summary>
		public void Reset()
		{
			_arrayPtr = basePtr;
			_index = -1;
		}
	}
}