// SPDX-License-Identifier: (Not available for this version, you are only allowed to use this software if you have express permission from the copyright holder and agreed to the latest NiloToonURP EULA)
// Copyright (c) 2021 Kuroneko ShaderLab Limited

#pragma once

half3 BlendGenericMatCapColor(half3 dstCol, half3 srcCol, half3 srcA, uint blendMode)
{
    half3 add = dstCol + srcCol;
    half3 mul = dstCol * srcCol;
    half3 outCol = dstCol;

    if (blendMode == 0) outCol = srcCol;
    else if (blendMode == 1) outCol = add;
    else if (blendMode == 2) outCol = max(add - mul, dstCol);
    else if (blendMode == 3) outCol = mul;

    return lerp(dstCol, outCol, srcA);
}

float3 GetGenericMatCapCameraUpWS()
{
    return float3(UNITY_MATRIX_I_V[0][1], UNITY_MATRIX_I_V[1][1], UNITY_MATRIX_I_V[2][1]);
}

float3 GetGenericMatCapCameraForwardWS()
{
    return normalize(-float3(UNITY_MATRIX_I_V[0][2], UNITY_MATRIX_I_V[1][2], UNITY_MATRIX_I_V[2][2]));
}

float2 CalcGenericMatCapUV(float2 uv1, float3 normalWS, ToonLightingData lightingData, float4 mapST, float4 blendUV1, half zRotCancel, half perspective, half vrParallaxStrength)
{
    // VR stereo fix: head direction = HMD-center based (stable across eyes),
    // viewDirection = per-eye (parallax-correct). The vrParallaxStrength slider
    // lerps between "stable (0)" and "per-eye parallax (1)". Without this fix,
    // both vectors were equal and the slider had no effect.
    float3 headDirectionWS = GetMatCapHeadDirectionWS(lightingData.positionWS, lightingData.viewDirectionWS);
    float3 viewDirectionWS = lightingData.viewDirectionWS;
    float3 normalVD = normalize(lerp(headDirectionWS, viewDirectionWS, vrParallaxStrength));

    if (unity_OrthoParams.w > 0.5 || perspective < 0.5)
    {
        normalVD = GetGenericMatCapCameraForwardWS();
    }

    float3 bitangentVD = zRotCancel > 0.5 ? float3(0, 1, 0) : GetGenericMatCapCameraUpWS();
    bitangentVD = normalize(bitangentVD - normalVD * dot(bitangentVD, normalVD));
    float3 tangentVD = cross(normalVD, bitangentVD);

    float2 uvMat = float2(dot(tangentVD, normalWS), dot(bitangentVD, normalWS));
    uvMat = lerp(uvMat, saturate(uv1) * 2 - 1, blendUV1.xy);
    uvMat = uvMat * mapST.xy + mapST.zw;

    return uvMat * 0.5 + 0.5;
}

// lilToon-faithful matcap is applied as a post-light decoration on the lit color,
// not as a pre-light albedo modifier. Inner guard makes the body empty unless the
// shader keyword is on AND we are in the ForwardLit pass (matcap should not affect
// outline / shadow / depth / stencil passes).
void ApplyGenericMatCap1(inout half3 color, ToonSurfaceData surfaceData, Varyings varyings, ToonLightingData lightingData)
{
#if _GENERIC_MATCAP1 && NiloToonForwardLitPass && !_NILOTOON_FUR
    half3 normalWS = normalize(lerp(lightingData.normalWS_NoNormalMap, lightingData.normalWS, _GenericMatCap1NormalStrength));

    #if _GENERIC_MATCAP1_CUSTOM_NORMAL
    float2 bumpUv = CalcUV(GetUV(varyings), _GenericMatCap1BumpMap_ST);
    half3 customNormalTS = UnpackNormalScale(tex2D(_GenericMatCap1BumpMap, bumpUv), _GenericMatCap1BumpScale);
    normalWS = NormalizeNormalPerPixel(TransformTangentToWorld(customNormalTS, lightingData.TBN_WS));
    #endif

    float2 matCapUv = CalcGenericMatCapUV(GetUV(varyings, 1), normalWS, lightingData, _GenericMatCap1Map_ST, _GenericMatCap1BlendUV1, _GenericMatCap1ZRotCancel, _GenericMatCap1Perspective, _GenericMatCap1VRParallaxStrength);
    half4 matCapColor = _GenericMatCap1Color * tex2Dlod(_GenericMatCap1Map, float4(matCapUv, 0, _GenericMatCap1Lod));
    matCapColor.rgb = lerp(matCapColor.rgb, matCapColor.rgb * saturate(lightingData.mainLight.color), _GenericMatCap1EnableLighting);
    matCapColor.a = lerp(matCapColor.a, matCapColor.a * lightingData.averageShadowAttenuation, _GenericMatCap1ShadowMask);

    if (_GenericMatCap1ApplyTransparency > 0.5)
    {
        matCapColor.a *= surfaceData.alpha;
    }

    matCapColor.a = lightingData.facing < (_GenericMatCap1BackfaceMask - 1.0) ? 0.0 : matCapColor.a;

    float2 maskUv = CalcUV(GetUV(varyings), _GenericMatCap1Mask_ST);
    half3 matCapMask = tex2D(_GenericMatCap1Mask, maskUv).rgb;
    matCapColor.rgb = lerp(matCapColor.rgb, matCapColor.rgb * surfaceData.albedo, _GenericMatCap1MainStrength);
    color = BlendGenericMatCapColor(color, matCapColor.rgb, _GenericMatCap1Blend * matCapColor.a * matCapMask, _GenericMatCap1BlendMode);
#endif
}

void ApplyGenericMatCap2(inout half3 color, ToonSurfaceData surfaceData, Varyings varyings, ToonLightingData lightingData)
{
#if _GENERIC_MATCAP2 && NiloToonForwardLitPass && !_NILOTOON_FUR
    half3 normalWS = normalize(lerp(lightingData.normalWS_NoNormalMap, lightingData.normalWS, _GenericMatCap2NormalStrength));

    #if _GENERIC_MATCAP2_CUSTOM_NORMAL
    float2 bumpUv = CalcUV(GetUV(varyings), _GenericMatCap2BumpMap_ST);
    half3 customNormalTS = UnpackNormalScale(tex2D(_GenericMatCap2BumpMap, bumpUv), _GenericMatCap2BumpScale);
    normalWS = NormalizeNormalPerPixel(TransformTangentToWorld(customNormalTS, lightingData.TBN_WS));
    #endif

    float2 matCapUv = CalcGenericMatCapUV(GetUV(varyings, 1), normalWS, lightingData, _GenericMatCap2Map_ST, _GenericMatCap2BlendUV1, _GenericMatCap2ZRotCancel, _GenericMatCap2Perspective, _GenericMatCap2VRParallaxStrength);
    half4 matCapColor = _GenericMatCap2Color * tex2Dlod(_GenericMatCap2Map, float4(matCapUv, 0, _GenericMatCap2Lod));
    matCapColor.rgb = lerp(matCapColor.rgb, matCapColor.rgb * saturate(lightingData.mainLight.color), _GenericMatCap2EnableLighting);
    matCapColor.a = lerp(matCapColor.a, matCapColor.a * lightingData.averageShadowAttenuation, _GenericMatCap2ShadowMask);

    if (_GenericMatCap2ApplyTransparency > 0.5)
    {
        matCapColor.a *= surfaceData.alpha;
    }

    matCapColor.a = lightingData.facing < (_GenericMatCap2BackfaceMask - 1.0) ? 0.0 : matCapColor.a;

    float2 maskUv = CalcUV(GetUV(varyings), _GenericMatCap2Mask_ST);
    half3 matCapMask = tex2D(_GenericMatCap2Mask, maskUv).rgb;
    matCapColor.rgb = lerp(matCapColor.rgb, matCapColor.rgb * surfaceData.albedo, _GenericMatCap2MainStrength);
    color = BlendGenericMatCapColor(color, matCapColor.rgb, _GenericMatCap2Blend * matCapColor.a * matCapMask, _GenericMatCap2BlendMode);
#endif
}