//********************************** Banshee Engine (www.banshee3d.com) **************************************************//
//**************** Copyright (c) 2016 Marko Pintera (marko.pintera@gmail.com). All rights reserved. **********************//
#pragma once

#include "BsGLPrerequisites.h"
#include "RenderAPI/BsVertexBuffer.h"
#include "BsGLVertexArrayObjectManager.h"

namespace bs { namespace ct
{
	/** @addtogroup GL
	 *  @{
	 */

	/** Wrapper around a generic OpenGL buffer. */
	class GLBuffer
	{
	public:
		/** Creates an uninitialized buffer object. You must call initialize() before using it. */
		GLBuffer();

		/** Creates and initializes the buffer object. */
		GLBuffer(GLenum target, UINT32 size, GpuBufferUsage usage);
		~GLBuffer();

		/** 
		 * Initializes the internal buffer object. Done automatically if the buffer was constructed using non-zero
		 * parameter constructor.
		 */
		void initialize(GLenum target, UINT32 size, GpuBufferUsage usage);

		/**
		 * Locks a portion of the buffer and returns pointer to the locked area. You must call unlock() when done.
		 *
		 * @param[in]	offset	Offset in bytes from which to lock the buffer.
		 * @param[in]	length	Length of the area you want to lock, in bytes.
		 * @param[in]	options	Signifies what you want to do with the returned pointer. Caller must ensure not to do 
		 *						anything he hasn't requested (for example don't try to read from the buffer unless you
		 *						requested it here).
		 */
		void* lock(UINT32 offset, UINT32 length, GpuLockOptions options);

		/**	Releases the lock on this buffer. */
		void unlock();

		/**
		 * Reads data from a portion of the buffer and copies it to the destination buffer. Caller must ensure destination 
		 * buffer is large enough.
		 *
		 * @param[in]	offset	Offset in bytes from which to copy the data.
		 * @param[in]	length	Length of the area you want to copy, in bytes.
		 * @param[in]	dest	Destination buffer large enough to store the read data.
		 */
		void readData(UINT32 offset, UINT32 length, void* dest);

		/**
		 * Writes data into a portion of the buffer from the source memory. 
		 *
		 * @param[in]	offset		Offset in bytes from which to copy the data.
		 * @param[in]	length		Length of the area you want to copy, in bytes.
		 * @param[in]	source		Source buffer containing the data to write.
		 * @param[in]	writeFlags	Optional write flags that may affect performance.
		 */
		void writeData(UINT32 offset, UINT32 length, const void* source,
			BufferWriteType writeFlags = BWT_NORMAL);

		/**
		 * Copies data from a specific portion of this buffer into a specific portion of the provided buffer.
		 *
		 * @param[in]	dstBuffer			Buffer to copy from.
		 * @param[in]	srcOffset			Offset into the source buffer to start copying from, in bytes.
		 * @param[in]	dstOffset			Offset into this buffer to start copying to, in bytes.
		 * @param[in]	length				Size of the data to copy, in bytes.
		 */
		void copyData(GLBuffer& dstBuffer, UINT32 srcOffset, UINT32 dstOffset, UINT32 length);

		/**	Returns internal OpenGL buffer ID. */
		GLuint getGLBufferId() const { return mBufferId; }

	private:
		GLenum mTarget;
		GLuint mBufferId;

		bool mZeroLocked;
	};

	/** @} */
}}