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#pragma once
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#include "../TonemapCommon.ush"
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#define TOON_TONEMAPPING_TYPE_NONE     0
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#define TOON_TONEMAPPING_TYPE_ACES     1
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#define TOON_TONEMAPPING_TYPE_NAES     2
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#define TOON_TONEMAPPING_TYPE_LOG2     3
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#define TOON_TONEMAPPING_TYPE_GT       4
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// ========================== NAES Tonemap ==========================
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float3 NAESTonemap(float3 input, float MaxBrightness)
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{
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    // 按最大亮度进行缩放，防止 HDR 高光在曲线末端被错误截断
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    input = input / MaxBrightness;
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    input = (1.36 * input + 0.047) * input / ((0.93 * input + 0.56) * input + 0.14);
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    return input * MaxBrightness;
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}
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// ========================== Gran Turismo Tonemap ==========================
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float W_f(float x, float e0, float e1)
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{
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    if (x <= e0) return 0;
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    if (x >= e1) return 1;
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    float a = (x - e0) / max(e1 - e0, 0.00001);
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    return a * a * (3 - 2 * a);
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}
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float H_f(float x, float e0, float e1)
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{
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    if (x <= e0) return 0;
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    if (x >= e1) return 1;
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    return (x - e0) / max(e1 - e0, 0.00001);
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}
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float GranTurismoTonemap(float x, float MaxBrightness)
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{
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    float P = MaxBrightness;
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    float a = 1;
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    float m = 0.22;
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    float l = 0.4;
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    float c = 1.33;
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    float b = 0;
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    float l0 = (P - m) * l / a;
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    float L0 = m - m / a;
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    float L1 = m + (1 - m) / a;
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    float L_x = m + a * (x - m);
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    float T_x = m * pow(x / m, c) + b;
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    float S0 = m + l0;
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    float S1 = m + a * l0;
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    float C2 = a * P / max(P - S1, 0.00001);
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    float S_x = P - (P - S1) * exp(-(C2 * (x - S0) / P));
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    float w0_x = 1 - W_f(x, 0, m);
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    float w2_x = H_f(x, m + l0, m + l0 + 0.00001);
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    float w1_x = 1 - w0_x - w2_x;
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    return T_x * w0_x + L_x * w1_x + S_x * w2_x;
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}
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float3 GranTurismoTonemap(float3 color, float MaxBrightness)
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{
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    return float3(
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        GranTurismoTonemap(color.r, MaxBrightness),
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        GranTurismoTonemap(color.g, MaxBrightness),
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        GranTurismoTonemap(color.b, MaxBrightness)
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    );
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}
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// ========================== Log2 Tonemap ==========================
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float3 Log2Tonemap(float3 color, float MaxBrightness) {
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    color = color / MaxBrightness;
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    float3 logColor = log2(max(color, 0.0001));
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    float3 compressed = exp2(logColor * 0.33) * 1.4938 - 0.7;
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    float3 tonemapped = lerp(color, compressed, step(0.3, color));
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    return saturate(tonemapped) * MaxBrightness;
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}
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// ========================== 入口函数 ==========================
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float3 ApplyTonemapper(uint TonemapperType, float3 LinearColor, float MaxBrightness)
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{
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    if (TonemapperType == TOON_TONEMAPPING_TYPE_NONE)
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    {
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        return LinearColor;
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    }
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    else if (TonemapperType == TOON_TONEMAPPING_TYPE_NAES)
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    {
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        return NAESTonemap(LinearColor, MaxBrightness);
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    }
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    else if (TonemapperType == TOON_TONEMAPPING_TYPE_LOG2)
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    {
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        return Log2Tonemap(LinearColor, MaxBrightness);
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    }
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    else if (TonemapperType == TOON_TONEMAPPING_TYPE_GT)
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    {
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        return GranTurismoTonemap(LinearColor, MaxBrightness);
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    }
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    return FilmToneMap(LinearColor);
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}