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

#include "BsRenderBeastPrerequisites.h"
#include "Renderer/BsRendererMaterial.h"
#include "Renderer/BsParamBlocks.h"
#include "Renderer/BsLight.h"

namespace bs { namespace ct
{
	struct SceneInfo;
	class RendererViewGroup;

	/** @addtogroup RenderBeast
	 *  @{
	 */

	/** Information about a single light, as seen by the lighting shader. */
	struct LightData
	{
		Vector3 position;
		float attRadius;
		Vector3 direction;
		float luminance;
		Vector3 spotAngles;
		float attRadiusSqrdInv;
		Vector3 color;
		float srcRadius;
		Vector3 shiftedLightPosition;
		float padding;
	};

	/**	Renderer information specific to a single light. */
	class RendererLight
	{
	public:
		RendererLight(Light* light);

		/** Populates the structure with light parameters. */
		void getParameters(LightData& output) const;

		/** 
		 * Populates the provided parameter block buffer with information about the light. Provided buffer's structure
		 * must match PerLightParamDef.
		 */
		void getParameters(SPtr<GpuParamBlockBuffer>& buffer) const;
		
		/** 
		 * Calculates the light position that is shifted in order to account for area spot lights. For non-spot lights
		 * this method will return normal light position. The position will be shifted back from the light direction, 
		 * magnitude of the shift depending on the source radius.
		 */
		Vector3 getShiftedLightPosition() const;

		Light* internal;
	};

	/** Container for all GBuffer textures. */
	struct GBufferTextures
	{
		SPtr<Texture> albedo;
		SPtr<Texture> normals;
		SPtr<Texture> roughMetal;
		SPtr<Texture> depth;
	};

	/** Allows you to easily bind GBuffer textures to some material. */
	class GBufferParams
	{
	public:
		GBufferParams(const SPtr<Material>& material, const SPtr<GpuParamsSet>& paramsSet);

		/** Binds the GBuffer textures to the pipeline. */
		void bind(const GBufferTextures& gbuffer);
	private:
		SPtr<Material> mMaterial;
		SPtr<GpuParamsSet> mParamsSet;

		MaterialParamTexture mGBufferA;
		MaterialParamTexture mGBufferB;
		MaterialParamTexture mGBufferC;
		MaterialParamTexture mGBufferDepth;
	};

	/** 
	 * Contains lights that are visible from a specific set of views, determined by scene information provided to 
	 * setLights().
	 */
	class VisibleLightData
	{
	public:
		VisibleLightData();

		/** 
		 * Updates the internal buffers with a new set of lights. Before calling make sure that light visibility has
		 * been calculated for the provided view group.
		 */
		void update(const SceneInfo& sceneInfo, const RendererViewGroup& viewGroup);

		/** Returns a GPU bindable buffer containing information about every light. */
		SPtr<GpuBuffer> getLightBuffer() const { return mLightBuffer; }

		/** Returns the number of directional lights in the lights buffer. */
		UINT32 getNumDirLights() const { return mNumLights[0]; }

		/** Returns the number of radial point lights in the lights buffer. */
		UINT32 getNumRadialLights() const { return mNumLights[1]; }

		/** Returns the number of spot point lights in the lights buffer. */
		UINT32 getNumSpotLights() const { return mNumLights[2]; }

		/** Returns the number of visible lights of the specified type. */
		UINT32 getNumLights(LightType type) const { return mNumLights[(UINT32)type]; }

		/** Returns the number of visible shadowed lights of the specified type. */
		UINT32 getNumShadowedLights(LightType type) const { return mNumShadowedLights[(UINT32)type]; }

		/** Returns the number of visible unshadowed lights of the specified type. */
		UINT32 getNumUnshadowedLights(LightType type) const { return mNumLights[(UINT32)type] - mNumShadowedLights[(UINT32)type]; }

		/** Returns a list of all visible lights of the specified type. */
		const Vector<const RendererLight*>& getLights(LightType type) const { return mVisibleLights[(UINT32)type]; }
	private:
		SPtr<GpuBuffer> mLightBuffer;

		UINT32 mNumLights[(UINT32)LightType::Count];
		UINT32 mNumShadowedLights[(UINT32)LightType::Count];

		// These are rebuilt every call to setLights()
		Vector<const RendererLight*> mVisibleLights[(UINT32)LightType::Count];

		// Helpers to avoid memory allocations
		Vector<LightData> mLightDataTemp;
	};

	BS_PARAM_BLOCK_BEGIN(TiledLightingParamDef)
		BS_PARAM_BLOCK_ENTRY(Vector4I, gLightCounts)
		BS_PARAM_BLOCK_ENTRY(Vector2I, gLightStrides)
		BS_PARAM_BLOCK_ENTRY(Vector2I, gFramebufferSize)
	BS_PARAM_BLOCK_END

	extern TiledLightingParamDef gTiledLightingParamDef;

	/** Shader that performs a lighting pass over data stored in the Gbuffer. */
	class TiledDeferredLightingMat : public RendererMaterial<TiledDeferredLightingMat>
	{
		RMAT_DEF("TiledDeferredLighting.bsl");

	public:
		TiledDeferredLightingMat();

		/** Binds the material for rendering, sets up parameters and executes it. */
		void execute(const RendererView& view, const VisibleLightData& lightData, const GBufferTextures& gbuffer,
			const SPtr<Texture>& lightAccumTex, const SPtr<GpuBuffer>& lightAccumBuffer, const SPtr<Texture>& msaaCoverage);

		/** Returns the material variation matching the provided parameters. */
		static TiledDeferredLightingMat* getVariation(UINT32 msaaCount);

	private:
		UINT32 mSampleCount;
		GBufferParams mGBufferParams;

		GpuParamBuffer mLightBufferParam;
		GpuParamLoadStoreTexture mOutputTextureParam;
		GpuParamBuffer mOutputBufferParam;
		GpuParamTexture mMSAACoverageTexParam;

		SPtr<GpuParamBlockBuffer> mParamBuffer;

		static const UINT32 TILE_SIZE;

		static ShaderVariation VAR_1MSAA;
		static ShaderVariation VAR_2MSAA;
		static ShaderVariation VAR_4MSAA;
		static ShaderVariation VAR_8MSAA;
	};

	BS_PARAM_BLOCK_BEGIN(FlatFramebufferToTextureParamDef)
		BS_PARAM_BLOCK_ENTRY(Vector2I, gFramebufferSize)
		BS_PARAM_BLOCK_ENTRY(INT32, gSampleCount)
	BS_PARAM_BLOCK_END

	/** Shader that copies a flattened framebuffer into a multisampled texture. */
	class FlatFramebufferToTextureMat : public RendererMaterial<FlatFramebufferToTextureMat>
	{
		RMAT_DEF("FlatFramebufferToTexture.bsl");

	public:
		FlatFramebufferToTextureMat();

		/** Binds the material for rendering, sets up parameters and executes it. */
		void execute(const SPtr<GpuBuffer>& flatFramebuffer, const SPtr<Texture>& target);
	private:
		GpuParamBuffer mInputParam;
		SPtr<GpuParamBlockBuffer> mParamBuffer;
	};

	/** @} */
}}