// Copyright Epic Games, Inc. All Rights Reserved.

#include "/Engine/Shared/MaterialCacheDefinitions.h"
#include "/Engine/Private/Common.ush"
#include "/Engine/Private/Nanite/NaniteShadeCommon.ush"
#include "/Engine/Private/MortonCode.ush"
#include "/Engine/Public/RootConstants.ush"
#include "/Engine/Private/MaterialCache/MaterialCacheABuffer.ush"

#define SceneTexturesStruct MaterialCachePass.SceneTextures 
#define EyeAdaptationStruct MaterialCachePass

#include "/Engine/Generated/Material.ush"
#include "/Engine/Generated/VertexFactory.ush"
#include "/Engine/Generated/UniformBuffers/MaterialCachePass.ush"
#include "/Engine/Private/MaterialCache/MaterialCacheShadeCommon.ush"

COMPILER_ALLOW_CS_DERIVATIVES

Buffer<uint> PageIndirections;

FMaterialCacheABuffer ShadeAttributes(in FPackedNaniteView PackedView, uint2 VisBufferPixelPos, uint ViewIndex)
{
	ResolvedView = ResolveView();

	FVertexFactoryInterpolantsVSToPS Interpolants = (FVertexFactoryInterpolantsVSToPS)0;
	Interpolants.PixelPos  = VisBufferPixelPos;
	Interpolants.ViewIndex = ViewIndex;

	FNaniteView NaniteView = UnpackNaniteView(PackedView);
	PatchViewState(NaniteView, ResolvedView);

	float4 SvPosition                    = float4(VisBufferPixelPos + 0.5f.xx, 0.0f, 1.0f);
	const float4 ScreenPosition          = SvPositionToResolvedScreenPosition(SvPosition);
	const float3 TranslatedWorldPosition = SvPositionToResolvedTranslatedWorld(SvPosition);

	FMaterialPixelParameters MaterialParameters = GetMaterialPixelParameters(NaniteView, Interpolants, SvPosition);

	FPixelMaterialInputs PixelMaterialInputs;
	CalcMaterialParametersEx(MaterialParameters, PixelMaterialInputs, SvPosition, ScreenPosition, true, TranslatedWorldPosition, TranslatedWorldPosition);

	return GetMaterialABuffer(MaterialParameters, PixelMaterialInputs);
}

[numthreads(64, 1, 1)]
void Main(uint3 DTid : SV_DispatchThreadID)
{
	const uint PageIndex     = PageIndirections[GetRootConstant0() + DTid.y];
	const uint ShadingBin	 = GetRootConstant1();
	const uint MeshPassIndex = GetRootConstant2();

	const EMaterialCacheFlag    Flags      = (EMaterialCacheFlag)GetRootConstant1();
	const FPackedNaniteView     PackedView = NaniteShading.InViews[PageIndex];
	const FMaterialCacheBinData BinData    = NaniteShading.ShadingBinData.Load<FMaterialCacheBinData>(sizeof(FMaterialCacheBinData) * PageIndex);
	
	// Tile width guaranteed to be power of two, Morton is fine
	const uint2 PagePixelPos      = MortonDecode(DTid.x);
	const uint2 VisBufferPixelPos = PackedView.ViewRect.xy + PagePixelPos;
	
	uint DepthInt = 0;
	uint VisibleClusterIndex = 0;
	uint TriIndex = 0;
	UnpackVisPixel(NaniteShading.VisBuffer64[VisBufferPixelPos], DepthInt, VisibleClusterIndex, TriIndex);
	
	if (VisibleClusterIndex == 0xFFFFFFFF)
	{
		return;
	}
	
	FVisibleCluster    VisibleCluster = GetVisibleCluster(VisibleClusterIndex);
	FInstanceSceneData InstanceData   = GetInstanceSceneDataUnchecked(VisibleCluster);
	FCluster           ClusterData    = GetCluster(VisibleCluster.PageIndex, VisibleCluster.ClusterIndex);

	const uint PixelShadingBin = GetMaterialShadingBin(ClusterData, InstanceData.PrimitiveId, MeshPassIndex, TriIndex);
	if (PixelShadingBin != ShadingBin)
	{
		return;
	}
	
	// Shader against the current layer
	FMaterialCacheABuffer Top = ShadeAttributes(PackedView, VisBufferPixelPos, PageIndex);
	if (Top.Clipped)
	{
		return;
	}

	StoreMaterialABufferPixel(Top, Flags, BinData.ABufferPhysicalPosition, PagePixelPos);
}