// BVLE Voxels - Bilateral AO Blur Compute Shader (Phase 6.3)
// Separable bilateral blur: preserves edges using depth + normal comparison.
// Run twice: horizontal (direction=0) then vertical (direction=1).

#include "voxelCommon.hlsli"

// Input AO (raw or partially blurred)
Texture2D<float> aoInput : register(t0);

// Depth + normals for edge-stopping
Texture2D<float>  depthTexture  : register(t1);
Texture2D<float4> normalTexture : register(t2);

// Output blurred AO
RWTexture2D<float> aoOutput : register(u0);

struct BlurPush {
    uint width;
    uint height;
    uint direction; // 0 = horizontal, 1 = vertical
    uint radius;    // blur kernel radius (e.g. 4 = 9x1 kernel)
    float depthThreshold;  // edge-stopping depth sensitivity
    float normalThreshold; // edge-stopping normal sensitivity (dot product)
    uint pad[6];
};
[[vk::push_constant]] ConstantBuffer<BlurPush> push : register(b999);

[RootSignature(VOXEL_ROOTSIG)]
[numthreads(8, 8, 1)]
void main(uint3 DTid : SV_DispatchThreadID) {
    if (DTid.x >= push.width || DTid.y >= push.height) return;

    float centerAO    = aoInput[DTid.xy];
    float centerDepth = depthTexture[DTid.xy];
    float3 centerN    = normalTexture[DTid.xy].xyz;

    // Skip sky pixels
    if (centerDepth == 0.0) {
        aoOutput[DTid.xy] = 1.0;
        return;
    }

    // Gaussian-ish weights (sigma ≈ radius/2)
    float totalWeight = 1.0;
    float totalAO     = centerAO;

    int2 step = (push.direction == 0) ? int2(1, 0) : int2(0, 1);
    int r = (int)push.radius;

    for (int i = -r; i <= r; i++) {
        if (i == 0) continue;

        int2 coord = int2(DTid.xy) + step * i;
        if (coord.x < 0 || coord.x >= (int)push.width ||
            coord.y < 0 || coord.y >= (int)push.height)
            continue;

        float sampleAO    = aoInput[coord];
        float sampleDepth = depthTexture[coord];
        float3 sampleN    = normalTexture[coord].xyz;

        // Skip sky
        if (sampleDepth == 0.0) continue;

        // Edge-stopping: depth difference
        float depthDiff = abs(centerDepth - sampleDepth);
        float depthWeight = exp(-depthDiff * depthDiff / (push.depthThreshold * push.depthThreshold));

        // Edge-stopping: normal difference
        float normalDot = max(0.0, dot(centerN, sampleN));
        float normalWeight = (normalDot > push.normalThreshold) ? normalDot : 0.0;

        // Spatial weight (Gaussian falloff)
        float dist = float(abs(i)) / float(r + 1);
        float spatialWeight = exp(-dist * dist * 2.0);

        float w = spatialWeight * depthWeight * normalWeight;
        totalWeight += w;
        totalAO     += sampleAO * w;
    }

    aoOutput[DTid.xy] = totalAO / totalWeight;
}