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

/*==============================================================================
	TraceRayInlineMetal.ush: Metal-specific inline ray tracing functionality,
	such as utility functions for accessing triangle indices and vertices.
==============================================================================*/

#pragma once

#include "/Engine/Shared/RayTracingDefinitions.h"
#include "/Engine/Private/RayTracing/RayTracingCommon.ush"

#if COMPILER_DXC && COMPILER_METAL && PLATFORM_SUPPORTS_INLINE_RAY_TRACING

#define PLATFORM_SUPPORTS_INLINE_RAY_TRACING_TRIANGLE_ATTRIBUTES 0

// Counterpart of FHitGroupSystemRootConstants.
// TODO: Need to retrieve geometry (VBs/IBs for BLAS).
struct FMetalRayTracingGeometryParameters
{
	uint Config;
	uint IndexBufferOffsetInBytes;
	uint FirstPrimitive;
	uint UserData;
};

// Create a generic alias for the Metal-specific metadata type
#define FRayTracingSceneMetadataRecord FMetalRayTracingGeometryParameters

uint GetInlineRayTracingHitGroupFirstPrimitive(
	StructuredBuffer<FRayTracingSceneMetadataRecord> RayTracingSceneMetadata,
	uint InstanceContributionToHitGroupIndex,
	uint MultiplierForGeometryContributionToHitGroupIndex,
	uint GeometryIndex)
{
	uint RecordIndex = InstanceContributionToHitGroupIndex / MultiplierForGeometryContributionToHitGroupIndex + GeometryIndex;
	FRayTracingSceneMetadataRecord Params = RayTracingSceneMetadata[RecordIndex];

	return Params.FirstPrimitive;
}

// TODO: Need to retrieve VBs/IBs to fetch the position.
FTriangleBaseAttributes LoadInlineRayTracingTriangleAttributes(
	StructuredBuffer<FRayTracingSceneMetadataRecord> RayTracingSceneMetadata,
	uint InstanceContributionToHitGroupIndex,
	uint MultiplierForGeometryContributionToHitGroupIndex,
	uint GeometryIndex,
	uint PrimitiveIndex)
{
	FTriangleBaseAttributes Result = (FTriangleBaseAttributes)0;
	return Result;
}
#endif // COMPILER_DXC && COMPILER_METAL && PLATFORM_SUPPORTS_INLINE_RAY_TRACING