#ifndef BLUR_INCLUDED
#define BLUR_INCLUDED

// Declare the texture only when the required macros exist.
#if defined(TEXTURE2D_X) && defined(SAMPLE_TEXTURE2D_X)
#define BLUR_TEXTURE_AVAILABLE 1
    TEXTURE2D_X(_CameraOpaqueTexture);
    SAMPLER(sampler_CameraOpaqueTexture);
#else
#define BLUR_TEXTURE_AVAILABLE 0
#endif

void Gaussian_float(float2 UV, float Blur, float Quality, out float3 Color)
{
#if defined(SHADERGRAPH_PREVIEW) || !BLUR_TEXTURE_AVAILABLE
    Color = float3(0.5, 0.5, 0.5);
#else
    float2 screenUV = saturate(UV);
    float radius = saturate(Blur) * 0.04;
    float2 stepUV = radius * float2(
        _ScreenParams.y / _ScreenParams.x,
        1.0
    );

    // LOW: 9 samples
    // MEDIUM: 25 samples
    // HIGH: 49 samples
    int extent = (int)clamp(floor(Quality + 0.5), 0.0, 2.0) + 1;

    float sigma = max(0.8, extent * 0.65);
    float invTwoSigmaSq = 0.5 / (sigma * sigma);

    float3 sum = 0.0;
    float totalWeight = 0.0;

    [loop]
    for (int y = -extent; y <= extent; ++y)
    {
        [loop]
        for (int x = -extent; x <= extent; ++x)
        {
            float2 offset = float2(x, y);

            float weight = exp2(
                -dot(offset, offset)
                * invTwoSigmaSq
                * 1.44269504089
            );

            float2 sampleUV = saturate(
                screenUV + offset * stepUV / extent
            );

            float3 sampleColor = SAMPLE_TEXTURE2D_X(
                _CameraOpaqueTexture,
                sampler_CameraOpaqueTexture,
                sampleUV
            ).rgb;

            sum += sampleColor * weight;
            totalWeight += weight;
        }
    }

    Color = sum / max(totalWeight, 1e-5);
#endif
}

void Gaussian_half(half2 UV, half Blur, half Quality, out half3 Color)
{
    float3 result;
    Gaussian_float(
        (float2) UV,
        (float) Blur,
        (float) Quality,
        result
    );
    Color = (half3) result;
}

#endif