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

#include "BsGLPrerequisites.h"
#include "RenderAPI/BsHardwareBuffer.h"
#include "Image/BsPixelUtil.h"

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

	class GLTextureBuffer;

	/**
	 * Represents a hardware buffer that stores a single pixel surface. This may be a 1D, 2D or 3D surface, but unlike a 
	 * texture it consists only of a single surface (no mip maps, cube map faces or similar).
	 */
	class GLPixelBuffer
	{
	public:
		/**
		 * Constructs a new pixel buffer with the provided settings.
		 *
		 * @param[in]	width			Width of the pixel buffer in pixels.
		 * @param[in]	height			Height of the pixel buffer in pixels.
		 * @param[in]	depth			Depth of the pixel buffer in pixels (number of 2D slices).
		 * @param[in]	format			Format of each pixel in the buffer.
		 * @param[in]	usage			Usage signaling the render system how we plan on using the buffer.
		 */
		GLPixelBuffer(UINT32 width, UINT32 height, UINT32 depth, PixelFormat format, GpuBufferUsage usage);
		virtual ~GLPixelBuffer();

		/**	Returns width of the surface in pixels. */
        UINT32 getWidth() const { return mWidth; }

		/**	Returns height of the surface in pixels. */
        UINT32 getHeight() const { return mHeight; }

		/**	Returns depth of the surface in pixels. */
        UINT32 getDepth() const { return mDepth; }

		/**	Returns format of the pixels in the surface. */
        PixelFormat getFormat() const { return mFormat; }

		/**
		 * Locks a certain region of the pixel buffer for reading and returns a pointer to the locked region.
		 *
		 * @param[in]	lockBox		Region of the surface to lock.
		 * @param[in]	options		Lock options that hint the hardware on what you intend to do with the locked data.
		 *
		 * @note	Returned object is only valid while the lock is active.
		 */
		const PixelData& lock(const PixelVolume& lockBox, GpuLockOptions options);
		
		/**
		 * 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);

		/**
		 * Locks the entire buffer and returns pointer to the locked area. You must call unlock() when done.
		 *
		 * @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(GpuLockOptions options)
        {
            return lock(0, mSizeInBytes, options);
        }

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

		/**
		 * Upload some pixel data to the buffer.
		 *
		 * @param[in]	data	Data to upload.
		 * @param[in]	dest	Coordinates to which to upload the data.
		 */
		virtual void upload(const PixelData& data, const PixelVolume& dest);

		/**
		 * Reads data from the pixel buffer into the provided object. Caller must ensure the data object is of adequate
		 * size.
		 */
		virtual void download(const PixelData& data);

		/**
		 * Binds the buffers to a frame buffer object at the specified attachment point.
		 *
		 * @param[in]	attachment	Attachment point index in the range [0, BS_MAX_MULTIPLE_RENDER_TARGETS).
		 * @param[in]	zoffset		Depth slice to bind, in the case of a 3D texture.
		 * @param[in]	allLayers	Should all layers of the texture be bound, or just one (zoffset is ignored if true).
		 */
		virtual void bindToFramebuffer(GLenum attachment, UINT32 zoffset, bool allLayers);

		/**
		 * Blits the contents of the provided buffer into this pixel buffer. Data is bilinearily interpolated in case buffer
		 * sizes don't match.
		 */
		virtual void blitFromTexture(GLTextureBuffer* src);

		/**
		 * Blits contents of a sub-region of the provided buffer into a sub-region of this pixel buffer. Data is bilinearily
		 * interpolated in case source and destination sizes don't match.
		 */
		virtual void blitFromTexture(GLTextureBuffer* src, const PixelVolume& srcBox, const PixelVolume& dstBox);

	protected:  
		/**	Allocates an internal buffer on the CPU, the size of the hardware buffer. */
		void allocateBuffer();

		/**	Deallocates the internal CPU buffer. */
		void freeBuffer();

	protected:
		UINT32 mSizeInBytes;
		GpuBufferUsage mUsage;
		bool mIsLocked;

		UINT32 mWidth, mHeight, mDepth;
		PixelFormat mFormat;

		PixelData mCurrentLock;
		PixelVolume mLockedBox;

		PixelData mBuffer;
		GpuLockOptions mCurrentLockOptions;
	};

	/**	Pixel buffer specialization that represents a single surface in a texture. */
    class GLTextureBuffer : public GLPixelBuffer
	{
    public:
		/**
		 * Constructs a new texture buffer from a specific surface in the provided texture.
		 *
		 * @param[in]	target				OpenGL type of the texture to retrieve the surface from.
		 * @param[in]	id					OpenGL handle to the texture to retrieve the surface from.
		 * @param[in]	face				Face index of the texture in the case of cube textures or texture arrays.
		 * @param[in]	level				Mip level of the texture.
		 * @param[in]	usage				Usage signaling the render system how we plan on using the buffer.
		 * @param[in]	format				Format of each pixel in the buffer.
		 * @param[in]	multisampleCount	Number of samples the parent texture was created with.
		 */
		GLTextureBuffer(GLenum target, GLuint id, GLint face, 
			GLint level, GpuBufferUsage usage, PixelFormat format, UINT32 multisampleCount);
        ~GLTextureBuffer();
        
		/** @copydoc GLPixelBuffer::bindToFramebuffer */
        void bindToFramebuffer(GLenum attachment, UINT32 zoffset, bool allLayers) override;

		/** @copydoc GLPixelBuffer::upload */
		void upload(const PixelData &data, const PixelVolume &dest) override;

		/** @copydoc GLPixelBuffer::download */
		void download(const PixelData &data) override;
  
		/** @copydoc GLPixelBuffer::blitFromTexture */
		void blitFromTexture(GLTextureBuffer *src, const PixelVolume &srcBox, const PixelVolume &dstBox) override;

        /**
         * Populate texture buffer with the data in the currently attached frame buffer.
		 *
		 * @param[in]	zoffset		3D slice of the texture to copy to. 0 if texture is not 3D.
         */
        void copyFromFramebuffer(UINT32 zoffset);

    protected:
		GLenum mTarget;
		GLenum mFaceTarget;
		GLuint mTextureID;
		GLint mFace;
		GLint mLevel;
		UINT32 mMultisampleCount;
    };

	/** @} */
}}