#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/RaytracingFragInputs.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/RaytracingSampling.hlsl"
#include "Packages/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Raytracing/Shaders/Common/AtmosphericScatteringRayTracing.hlsl"

// Generic function that handles the reflection code
[shader("closesthit")]
void ClosestHitMain(inout RayIntersection rayIntersection : SV_RayPayload, AttributeData attributeData : SV_IntersectionAttributes)
{
    UNITY_XR_ASSIGN_VIEW_INDEX(DispatchRaysIndex().z);

    // The first thing that we should do is grab the intersection vertice
    IntersectionVertex currentVertex;
    GetCurrentIntersectionVertex(attributeData, currentVertex);

    // Build the Frag inputs from the intersection vertice
    FragInputs fragInput;
    BuildFragInputsFromIntersection(currentVertex, rayIntersection.incidentDirection, fragInput);

    // Compute the view vector
    float3 viewWS = -rayIntersection.incidentDirection;
    float3 pointWSPos = fragInput.positionRWS;

    // Make sure to add the additional travel distance
    float travelDistance = length(fragInput.positionRWS - rayIntersection.origin);
    rayIntersection.t = travelDistance;
    rayIntersection.cone.width += travelDistance * rayIntersection.cone.spreadAngle;

    PositionInputs posInput = GetPositionInput(rayIntersection.pixelCoord, _ScreenSize.zw, fragInput.positionRWS);

    // Build the surfacedata and builtindata
    SurfaceData surfaceData;
    BuiltinData builtinData;
    bool isVisible;
    GetSurfaceAndBuiltinData(fragInput, viewWS, posInput, surfaceData, builtinData, currentVertex, rayIntersection.cone, isVisible);

    // Compute the bsdf data
    BSDFData bsdfData = ConvertSurfaceDataToBSDFData(posInput.positionSS, surfaceData);

    // No need for SurfaceData after this line

#ifdef HAS_LIGHTLOOP
    // We do not want to use the diffuse when we compute the indirect diffuse
    if (_RayTracingDiffuseLightingOnly)
    {
        builtinData.bakeDiffuseLighting = float3(0.0, 0.0, 0.0);
        builtinData.backBakeDiffuseLighting = float3(0.0, 0.0, 0.0);
    }

    // Compute the prelight data
    PreLightData preLightData = GetPreLightData(viewWS, posInput, bsdfData);
    float3 reflected = float3(0.0, 0.0, 0.0);
    float reflectedWeight = 0.0;

    #ifdef MULTI_BOUNCE_INDIRECT
    // We only launch a ray if there is still some depth be used
    if (rayIntersection.remainingDepth < _RaytracingMaxRecursion)
    {
        // Generate the new sample (follwing values of the sequence)
        float2 theSample = float2(0.0, 0.0);
        theSample.x = GetBNDSequenceSample(rayIntersection.pixelCoord, rayIntersection.sampleIndex, rayIntersection.remainingDepth * 2);
        theSample.y = GetBNDSequenceSample(rayIntersection.pixelCoord, rayIntersection.sampleIndex, rayIntersection.remainingDepth * 2 + 1);

        float3 sampleDir;
        if (_RayTracingDiffuseLightingOnly)
        {
            sampleDir = SampleHemisphereCosine(theSample.x, theSample.y, bsdfData.normalWS);
        }
        else
        {
            sampleDir = SampleSpecularBRDF(bsdfData, theSample, viewWS);
        }

        // Create the ray descriptor for this pixel
        RayDesc rayDescriptor;
        rayDescriptor.Origin = pointWSPos + bsdfData.normalWS * _RaytracingRayBias;
        rayDescriptor.Direction = sampleDir;
        rayDescriptor.TMin = 0.0f;
        rayDescriptor.TMax = _RaytracingRayMaxLength;

        // Create and init the RayIntersection structure for this
        RayIntersection reflectedIntersection;
        reflectedIntersection.color = float3(0.0, 0.0, 0.0);
        reflectedIntersection.incidentDirection = rayDescriptor.Direction;
        reflectedIntersection.origin = rayDescriptor.Origin;
        reflectedIntersection.t = -1.0f;
        reflectedIntersection.remainingDepth = rayIntersection.remainingDepth + 1;
        reflectedIntersection.pixelCoord = rayIntersection.pixelCoord;
        reflectedIntersection.sampleIndex = rayIntersection.sampleIndex;

        // In order to achieve filtering for the textures, we need to compute the spread angle of the pixel
        reflectedIntersection.cone.spreadAngle = rayIntersection.cone.spreadAngle;
        reflectedIntersection.cone.width = rayIntersection.cone.width;

        bool launchRay = true;
        if (!_RayTracingDiffuseLightingOnly)
            launchRay = dot(sampleDir, bsdfData.normalWS) > 0.0;

        // Evaluate the ray intersection
        if (launchRay)
            TraceRay(_RaytracingAccelerationStructure
                        , RAY_FLAG_CULL_BACK_FACING_TRIANGLES
                        , _RayTracingDiffuseLightingOnly ? RAYTRACINGRENDERERFLAG_GLOBAL_ILLUMINATION : RAYTRACINGRENDERERFLAG_REFLECTION
                        , 0, 1, 0, rayDescriptor, reflectedIntersection);

        // Contribute to the pixel
        if (_RayTracingDiffuseLightingOnly)
            builtinData.bakeDiffuseLighting = reflectedIntersection.color;
        else
        {
            // Override the reflected color
            reflected = reflectedIntersection.color;
            reflectedWeight = 1.0;
        }
    }
    #endif

    // Run the lightloop
    LightLoopOutput lightLoopOutput;
    LightLoop(viewWS, posInput, preLightData, bsdfData, builtinData, reflectedWeight, 0.0, reflected,  float3(0.0, 0.0, 0.0), lightLoopOutput);

    // Alias
    float3 diffuseLighting = lightLoopOutput.diffuseLighting;
    float3 specularLighting = lightLoopOutput.specularLighting;

    // Color display for the moment
    rayIntersection.color = diffuseLighting + specularLighting;
#else
    // Given that we will be multiplying the final color by the current exposure multiplier outside of this function, we need to make sure that
    // the unlit color is not impacted by that. Thus, we multiply it by the inverse of the current exposure multiplier.
    rayIntersection.color = bsdfData.color * GetInverseCurrentExposureMultiplier() + builtinData.emissiveColor;
#endif

    // Apply fog attenuation
    ApplyFogAttenuation(WorldRayOrigin(), WorldRayDirection(), rayIntersection.t, rayIntersection.color, true);
}

// Generic function that handles the reflection code
[shader("anyhit")]
void AnyHitMain(inout RayIntersection rayIntersection : SV_RayPayload, AttributeData attributeData : SV_IntersectionAttributes)
{
#ifdef _SURFACE_TYPE_TRANSPARENT
    IgnoreHit();
#else

    UNITY_XR_ASSIGN_VIEW_INDEX(DispatchRaysIndex().z);

    // The first thing that we should do is grab the intersection vertice
    IntersectionVertex currentVertex;
    GetCurrentIntersectionVertex(attributeData, currentVertex);

    // Build the Frag inputs from the intersection vertice
    FragInputs fragInput;
    BuildFragInputsFromIntersection(currentVertex, rayIntersection.incidentDirection, fragInput);

    // Compute the view vector
    float3 viewWS = -rayIntersection.incidentDirection;

    // Compute the distance of the ray
    float travelDistance = length(fragInput.positionRWS - rayIntersection.origin);
    rayIntersection.t = travelDistance;

    PositionInputs posInput;
    posInput.positionWS = fragInput.positionRWS;
    posInput.positionSS = rayIntersection.pixelCoord;

    // Build the surfacedata and builtindata
    SurfaceData surfaceData;
    BuiltinData builtinData;
    bool isVisible;
    GetSurfaceAndBuiltinData(fragInput, viewWS, posInput, surfaceData, builtinData, currentVertex, rayIntersection.cone, isVisible);

    // If this fella should be culled, then we cull it
    if(!isVisible)
    {
        IgnoreHit();
    }
#endif
}