#ifndef __LIGHTING_INC
#define __LIGHTING_INC

#include "UnityCG.cginc"
#include "AutoLight.cginc"
#include "UnityPBSLighting.cginc"
#include "UnityLightingCommon.cginc"
#include "UnityStandardCoreMinimal.cginc"

#include "burley.cginc"
#include "data.cginc"
#include "features.cginc"
#include "filamented.cginc"
#include "interpolators.cginc"
#include "LightVolumes.cginc"
#include "glitter.cginc"
#include "poi.cginc"

float3 getDirectLightDirection(v2f i) {
#if defined(POINT) || defined(POINT_COOKIE) || defined(SPOT)
	return normalize((_WorldSpaceLightPos0 - i.worldPos).xyz);
#else
	return _WorldSpaceLightPos0;
#endif
}

float getShadowAttenuation(v2f i)
{
  UNITY_LIGHT_ATTENUATION(attenuation, i, i.worldPos);
	return attenuation;
}

float4 getDirectLightColorIntensity() {
	// Properly separate light color from intensity like filamented
	if (_LightColor0.w <= 0) return float4(0, 0, 0, 0);
	return float4(_LightColor0.xyz, _LightColor0.w);
}

float3 getIndirectSpecular(v2f i, float perceptual_roughness, float3 view_dir, float3 reflect_dir, float3 indirect_diffuse) {
  UnityGIInput data = InitialiseUnityGIInput(i.worldPos, view_dir);
  float3 env_refl = UnityGI_prefilteredRadiance(data, perceptual_roughness, reflect_dir);

  return env_refl;
}

float3 getAverageSHDirection(float3 L1r, float3 L1g, float3 L1b, float3 fallback_dir) {
  float3 raw_dir = L1r + L1g + L1b;
  float raw_dir_len = length(raw_dir);
  if (abs(raw_dir_len) < 1e-3) {
    return fallback_dir;
  }
  return raw_dir / raw_dir_len;
}

// Geomerics SH evaluation
// https://community.arm.com/cfs-file/__key/telligent-evolution-components-attachments/01-2066-00-00-00-01-27-70/Simplifying_2D00_Spherical_2D00_Harmonics_2D00_for_2D00_Lighting.pdf
float shEvaluateDiffuseL1Geomerics(float L0, float3 L1, float3 n) {
  // average energy
  float R0 = max(L0, 0);

  // avg direction of incoming light
  float3 R1 = 0.5f * L1;

  // directional brightness
  float lenR1 = length(R1);

  // linear angle between normal and direction 0-1
  float q = dot(normalize(R1), n) * 0.5 + 0.5;
  q = saturate(q);

  // power for q
  // lerps from 1 (linear) to 3 (cubic) based on directionality
  float p = 1.0f + 2.0f * lenR1 / R0;

  // dynamic range constant
  // should vary between 4 (highly directional) and 0 (ambient)
  float a = (1.0f - lenR1 / R0) / (1.0f + lenR1 / R0);

  return R0 * (a + (1.0f - a) * (p + 1.0f) * pow(q, p));
}

float3 yumSH9(float4 n, float3 worldPos, inout LightIndirect light) {
  [branch]
  if (_UdonLightVolumeEnabled) {
    LightVolumeSH(worldPos, light.L00, light.L01r, light.L01g, light.L01b);
    return light.L00 + float3(
        dot(light.L01r, n.xyz),
        dot(light.L01g, n.xyz),
        dot(light.L01b, n.xyz));
  }

  // Unity gives us the first three bands (L0-L2) of SH coefficients as follows:
  //   unity_SHA*.w:   L0 coefficients
  //   unity_SHA*.xyz: L1 coefficients
  //   unity_SHB*:     first four of the L2 coefficients
  //   unity_SHC:      last L2 coefficient

  // Equation 13 from "An Efficient Representation for Irradiance Environment
  // Maps" by Ramamoorthi and Hanrahan. Normalization constants have been
  // premultiplied by Unity into the coefficient buffers.
  //
  // L0+L1: dot4 per channel (n.w=1 picks up the L0 term from SHA*.w)
  // L2: four quadratic terms packed into vB via swizzle multiply, plus L22
  float3 L0 = float3(unity_SHAr.w, unity_SHAg.w, unity_SHAb.w);
  float3 L1 = float3(dot(unity_SHAr, n.xyz), dot(unity_SHAg, n.xyz), dot(unity_SHAb, n.xyz));
  float4 vB = n.xyzz * n.yzzx;
  float3 L2 = float3(dot(unity_SHBr, vB), dot(unity_SHBg, vB), dot(unity_SHBb, vB))
            + unity_SHC * (n.x * n.x - n.y * n.y);

#if defined(_WRAPPED_LIGHTING)
  // Original coefficients: 1, 2/3, 1/4.
  // Wrapped coefficients: 1, (2-w)/3, ((1-w)^2)/4.

  // Setting w=0, the l1 band is:
  //   (2-w)/3 = 2/3
  //   2-w = 2
  //   1-w/2 = 1
  float wrap_amount = _Wrapped_Lighting_Amount;
  float l1_wrap = 1.0f - wrap_amount * 0.75f;
  L1 *= l1_wrap;

  // The l2 band is:
  //   ((1-w)^2)/4 = 1/4
  //   (1-w)^2 = 1
  float l2_wrap = (1.0f-wrap_amount);
  l2_wrap *= l2_wrap;
  L2 *= l2_wrap;
#else
  float l1_wrap = 1.0f;
#endif  // _WRAPPED_LIGHTING

  light.L00 = L0;
  light.L01r = unity_SHAr.xyz;
  light.L01g = unity_SHAg.xyz;
  light.L01b = unity_SHAb.xyz;

  return L0 + L1 + L2;
}

float4 getIndirectDiffuse(v2f i, Pbr pbr, inout LightData light) {
  float4 diffuse = 0;

#if defined(FORWARD_BASE_PASS) || defined(OUTLINES_PASS)
#if defined(_BENT_NORMALS)
  diffuse.xyz += max(0, yumSH9(float4(pbr.bent_normal, 1.0), i.worldPos, light.indirect));
#else
  diffuse.xyz += max(0, yumSH9(float4(i.normal, 1.0), i.worldPos, light.indirect));
#endif
#endif

#if defined(_SHADOWS) || defined(_SSFD)
  float3 dom_dir = getAverageSHDirection(
      light.indirect.L01r,
      light.indirect.L01g,
      light.indirect.L01b,
      light.direct.dir);
  light.indirect.diffuse_dominant_dir = dom_dir;
#endif

#if defined(_SHADOWS)
  float light_amount = dot(dom_dir, pbr.normal);
  float3 shadow_color = lerp(
    _Shadow_0_Color.rgb,
    1,
    smoothstep(_Shadow_0_Threshold - _Shadow_0_Blur, _Shadow_0_Threshold + _Shadow_0_Blur, light_amount));

#if defined(_SHADOW_1)
  shadow_color = lerp(
    _Shadow_1_Color.rgb,
    shadow_color,
    smoothstep(_Shadow_1_Threshold - _Shadow_1_Blur, _Shadow_1_Threshold + _Shadow_1_Blur, light_amount));
#endif  // _SHADOW_1

  diffuse.xyz *= shadow_color;
#endif  // _SHADOWS

  return diffuse;
}

float getAO(v2f i) {
  float ao = 1;
#if defined(_BURLEY_TILING) && defined(_BURLEY_TILING_AMBIENT_OCCLUSION)
  ao = saturate(lerp(
      1.0,
      burley_sample_scalar(
          _Burley_Tiling_Ambient_Occlusion_Map,
          _Burley_Tiling_Ambient_Occlusion_Map_LUT),
      _OcclusionStrength));
#elif defined(_AMBIENT_OCCLUSION)
  ao = saturate(lerp(1.0, _OcclusionMap.Sample(bilinear_repeat_s, i.uv01.xy).r, _OcclusionStrength));
#endif
  return ao;
}

float getSpecularAO(v2f i, Pbr pbr, LightData data, float3 reflect_dir) {
  float ao_vis = 1.0;
#if defined(_AMBIENT_OCCLUSION)
  ao_vis = data.common.ao;
#endif

  // Exposure occlusion: derive specular AO from diffuse irradiance magnitude.
  // When IBL diffuse goes dark, attenuate specular to avoid implausible
  // reflections. Based on filamented's IrradianceToExposureOcclusion.
  float exposure_ao = saturate(length(data.indirect.diffuse) / _Exposure_Occlusion);
  ao_vis *= exposure_ao;

#if defined(_BENT_NORMALS)
  float3 spec_ao_normal = pbr.bent_normal;
#else
  float3 spec_ao_normal = pbr.normal;
#endif
  float spec_ao = computeSpecularAO(data.common.NoV, ao_vis, pbr.roughness, spec_ao_normal, -data.indirect.dir);
#if defined(_BENT_NORMALS)
  spec_ao = saturate(lerp(1.0, spec_ao, _Bent_Normals_Strength));
#endif

  return spec_ao;
}

void GetLighting(v2f i, Pbr pbr, out LightData data) {
	data = (LightData) 0;
  data.common.ao = 1.0f;
  data.common.spec_ao = 1.0f;

	float3 view_dir = normalize(i.eyeVec.xyz);

	data.common.V = -view_dir;
	data.common.N = pbr.normal;
  data.common.NoV = max(1e-4, dot(pbr.normal, data.common.V));
  data.common.ao = getAO(i);
#if defined(_CLEARCOAT)
  data.common.NoV_cc = max(1e-4, dot(pbr.cc_normal, data.common.V));
#endif

	// Direct lighting
	data.direct.dir = getDirectLightDirection(i);
	data.direct.H = normalize(data.common.V + data.direct.dir);
#if defined(_WRAPPED_LIGHTING)
  data.direct.NoL = max(1e-4, wrapNoL(saturate(dot(pbr.normal, data.direct.dir)), _Wrapped_Lighting_Amount));
#else
	data.direct.NoL = max(1e-4, dot(pbr.normal, data.direct.dir));
#endif
	data.direct.NoH = max(1e-4, dot(pbr.normal, data.direct.H));
  data.direct.LoH = max(1e-4, dot(data.direct.dir, data.direct.H));
#if defined(_CLEARCOAT)
  data.direct.NoH_cc = max(1e-4, dot(pbr.cc_normal, data.direct.H));
  data.direct.NoL_cc = max(1e-4, dot(pbr.cc_normal, data.direct.dir));
#endif
  float direct_LoV = dot(data.direct.dir, data.common.V);
  data.direct.LoV = max(1e-4, direct_LoV);
  data.direct.double_LoV = max(1e-4, 2.0f * direct_LoV * direct_LoV - 1.0f);

	float4 lightColorIntensity = getDirectLightColorIntensity();
	data.direct.color = lightColorIntensity.rgb * (lightColorIntensity.w * getShadowAttenuation(i));

	// Indirect lighting
  float3 reflect_dir = reflect(-data.common.V, pbr.normal);
  float3 dominant_dir = getSpecularDominantDirection(pbr.normal, reflect_dir, pbr.roughness);

  data.indirect.dir = normalize(dominant_dir);
	data.indirect.H = normalize(data.common.V + data.indirect.dir);
	data.indirect.NoL = max(1e-4, dot(pbr.normal, data.indirect.dir));
	data.indirect.NoH = max(1e-4, dot(pbr.normal, data.indirect.H));
#if defined(_CLEARCOAT)
  float3 cc_reflect_dir = reflect(-data.common.V, pbr.cc_normal);
  float3 cc_dominant_dir = getSpecularDominantDirection(pbr.cc_normal, cc_reflect_dir, pbr.cc_roughness);
  float3 dir_cc = normalize(cc_dominant_dir);
  float3 H_cc = normalize(data.common.V + dir_cc);
#endif
  data.indirect.LoH = max(1e-4, dot(data.indirect.dir, data.indirect.H));
  float indirect_LoV = dot(data.indirect.dir, data.common.V);
  data.indirect.LoV = max(1e-4, indirect_LoV);
  data.indirect.double_LoV = max(1e-4, 2.0f * indirect_LoV * indirect_LoV - 1.0f);

	data.indirect.diffuse = getIndirectDiffuse(i, pbr, data);
	data.indirect.specular = getIndirectSpecular(i, pbr.roughness_perceptual, view_dir, data.indirect.dir, data.indirect.diffuse);
#if defined(_GLITTER)
  float3 glitter_indirect_dir = getAverageSHDirection(
      data.indirect.L01r,
      data.indirect.L01g,
      data.indirect.L01b,
      data.indirect.dir);
#if defined(_GLITTER_BASE_ROUGHNESS_OVERRIDE)
  float glitter_roughness = _Glitter_Base_Roughness_Override;
#else
  float glitter_roughness = pbr.roughness;
#endif
  data.glitter = GetGlitterLighting(
      _Glitter_Amount, _Glitter_Roughness, _Glitter_Angular_Cells,
      _Glitter_Filter_Size, UV_SCOFF(i, _Glitter_Mask_ST, _Glitter_UV_Channel), pbr.tbn, glitter_roughness, pbr.normal,
      data.common.V, data.direct.H, glitter_indirect_dir);
#endif

  data.common.spec_ao = getSpecularAO(i, pbr, data, reflect_dir);

#if defined(_CLEARCOAT)
  data.indirect.specular_cc = getIndirectSpecular(i, pbr.cc_roughness_perceptual, view_dir, dir_cc, data.indirect.diffuse);
#if defined(_CLEARCOAT_MASK)
  float cc_mask = _Clearcoat_Mask.Sample(bilinear_clamp_s, i.uv01.xy).r;
  data.indirect.specular_cc *= cc_mask;
#endif
#endif

#if defined(_BRIGHTNESS_CLAMP)
  float3 tmpHSV = RGBtoHSV(data.direct.color);
  tmpHSV[2] = clamp(tmpHSV[2], _Brightness_Clamp_Min, _Brightness_Clamp_Max);
  data.direct.color = HSVtoRGB(tmpHSV);

  tmpHSV = RGBtoHSV(data.indirect.diffuse);
  tmpHSV[2] = clamp(tmpHSV[2], _Brightness_Clamp_Min, _Brightness_Clamp_Max);
  data.indirect.diffuse = HSVtoRGB(tmpHSV);

  // No minimum for specular lighting. It would look awful.
  tmpHSV = RGBtoHSV(data.indirect.specular);
  tmpHSV[2] = clamp(tmpHSV[2], 0, _Brightness_Clamp_Max);
  data.indirect.specular = HSVtoRGB(tmpHSV);

#if defined(_GLITTER)
  tmpHSV = RGBtoHSV(data.indirect.L00);
  tmpHSV[2] = clamp(tmpHSV[2], 0, _Brightness_Clamp_Max);
  data.indirect.L00 = HSVtoRGB(tmpHSV);
#endif

#if defined(_CLEARCOAT)
  tmpHSV = RGBtoHSV(data.indirect.specular_cc);
  tmpHSV[2] = clamp(tmpHSV[2], 0, _Brightness_Clamp_Max);
  data.indirect.specular_cc = HSVtoRGB(tmpHSV);
#endif
#endif
}

#endif  // __LIGHTING_INC