#ifndef LIGHTWEIGHT_PASS_LIT_TERRAIN_INCLUDED
#define LIGHTWEIGHT_PASS_LIT_TERRAIN_INCLUDED

#include "LWRP/ShaderLibrary/Lighting.hlsl"

struct VertexInput
{
    float4 vertex : POSITION;
    float4 tangent : TANGENT;
    float3 normal : NORMAL;
    float2 texcoord : TEXCOORD0;
    float2 texcoord1 : TEXCOORD1;
};

struct VertexOutput
{
    float4 uvSplat01                : TEXCOORD0; // xy: splat0, zw: splat1
    float4 uvSplat23                : TEXCOORD1; // xy: splat2, zw: splat3
    float4 uvControlAndLM           : TEXCOORD2; // xy: control, zw: lightmap
    half3 normal                    : TEXCOORD3;
#if _TERRAIN_NORMAL_MAP
    half3 tangent                   : TEXCOORD4;
    half3 binormal                  : TEXCOORD5;
#endif
    half4 fogFactorAndVertexLight   : TEXCOORD6; // x: fogFactor, yzw: vertex light
    float3 positionWS               : TEXCOORD7;
    float4 shadowCoord              : TEXCOORD8;
    float4 clipPos                  : SV_POSITION;
};

void InitializeInputData(VertexOutput IN, half3 normalTS, out InputData input)
{
    input = (InputData)0;

    input.positionWS = IN.positionWS;

#ifdef _TERRAIN_NORMAL_MAP
    input.normalWS = TangentToWorldNormal(normalTS, IN.tangent, IN.binormal, IN.normal);
#else
    input.normalWS = normalize(IN.normal);
#endif

    input.viewDirectionWS = SafeNormalize(GetCameraPositionWS() - IN.positionWS);
#ifdef _SHADOWS_ENABLED
    input.shadowCoord = IN.shadowCoord;
#else
    input.shadowCoord = float4(0, 0, 0, 0);
#endif
    input.fogCoord = IN.fogFactorAndVertexLight.x;
    input.vertexLighting = IN.fogFactorAndVertexLight.yzw;

#ifdef LIGHTMAP_ON
    input.bakedGI = SampleLightmap(IN.uvControlAndLM.zw, input.normalWS);
#endif
}

void SplatmapMix(VertexOutput IN, half4 defaultAlpha, out half4 splat_control, out half weight, out half4 mixedDiffuse, inout half3 mixedNormal)
{
    splat_control = SAMPLE_TEXTURE2D(_Control, sampler_Control, IN.uvControlAndLM.xy);
    weight = dot(splat_control, 1);

#if !defined(SHADER_API_MOBILE) && defined(TERRAIN_SPLAT_ADDPASS)
    clip(weight == 0.0f ? -1 : 1);
#endif

    // Normalize weights before lighting and restore weights in final modifier functions so that the overal
    // lighting result can be correctly weighted.
    splat_control /= (weight + 1e-3f);

    mixedDiffuse = 0.0f;
    mixedDiffuse += splat_control.r * SAMPLE_TEXTURE2D(_Splat0, sampler_Splat0, IN.uvSplat01.xy) * half4(1.0, 1.0, 1.0, defaultAlpha.r);
    mixedDiffuse += splat_control.g * SAMPLE_TEXTURE2D(_Splat1, sampler_Splat0, IN.uvSplat01.zw) * half4(1.0, 1.0, 1.0, defaultAlpha.g);
    mixedDiffuse += splat_control.b * SAMPLE_TEXTURE2D(_Splat2, sampler_Splat0, IN.uvSplat23.xy) * half4(1.0, 1.0, 1.0, defaultAlpha.b);
    mixedDiffuse += splat_control.a * SAMPLE_TEXTURE2D(_Splat3, sampler_Splat0, IN.uvSplat23.zw) * half4(1.0, 1.0, 1.0, defaultAlpha.a);

#ifdef _TERRAIN_NORMAL_MAP
    half4 nrm = 0.0f;
    nrm += splat_control.r * SAMPLE_TEXTURE2D(_Normal0, sampler_Normal0, IN.uvSplat01.xy);
    nrm += splat_control.g * SAMPLE_TEXTURE2D(_Normal1, sampler_Normal0, IN.uvSplat01.zw);
    nrm += splat_control.b * SAMPLE_TEXTURE2D(_Normal2, sampler_Normal0, IN.uvSplat23.xy);
    nrm += splat_control.a * SAMPLE_TEXTURE2D(_Normal3, sampler_Normal0, IN.uvSplat23.zw);
    mixedNormal = UnpackNormal(nrm);
#else
    mixedNormal = half3(0, 0, 1);
#endif
}

void SplatmapFinalColor(inout half4 color, half fogCoord)
{
    color.rgb *= color.a;
    #ifdef TERRAIN_SPLAT_ADDPASS
        ApplyFogColor(color.rgb, half3(0,0,0), fogCoord);
    #else
        ApplyFog(color.rgb, fogCoord);
    #endif
}

///////////////////////////////////////////////////////////////////////////////
//                  Vertex and Fragment functions                            //
///////////////////////////////////////////////////////////////////////////////

// Used in Standard Terrain shader
VertexOutput SplatmapVert(VertexInput v)
{
    VertexOutput o = (VertexOutput)0;

    float3 positionWS = TransformObjectToWorld(v.vertex.xyz);
    float4 clipPos = TransformWorldToHClip(positionWS);

    o.uvSplat01.xy = TRANSFORM_TEX(v.texcoord, _Splat0);
    o.uvSplat01.zw = TRANSFORM_TEX(v.texcoord, _Splat1);
    o.uvSplat23.xy = TRANSFORM_TEX(v.texcoord, _Splat2);
    o.uvSplat23.zw = TRANSFORM_TEX(v.texcoord, _Splat3);
    o.uvControlAndLM.xy = TRANSFORM_TEX(v.texcoord, _Control);
    o.uvControlAndLM.zw = v.texcoord1 * unity_LightmapST.xy + unity_LightmapST.zw;

#ifdef _TERRAIN_NORMAL_MAP
    float4 vertexTangent = float4(cross(v.normal, float3(0, 0, 1)), -1.0);
    OutputTangentToWorld(vertexTangent, v.normal, o.tangent, o.binormal, o.normal);
#else
    o.normal = TransformObjectToWorldNormal(v.normal);
#endif
    o.fogFactorAndVertexLight.x = ComputeFogFactor(clipPos.z);
    o.fogFactorAndVertexLight.yzw = VertexLighting(positionWS, o.normal);
    o.positionWS = positionWS;
    o.clipPos = clipPos;

#ifdef _SHADOWS_ENABLED
#if SHADOWS_SCREEN
    o.shadowCoord = ComputeShadowCoord(o.clipPos);
#else
    o.shadowCoord = TransformWorldToShadowCoord(positionWS);
#endif
#endif

    return o;
}

// Used in Standard Terrain shader
half4 SpatmapFragment(VertexOutput IN) : SV_TARGET
{
    half4 splat_control;
    half weight;
    half4 mixedDiffuse;
    half4 defaultSmoothness = half4(_Smoothness0, _Smoothness1, _Smoothness2, _Smoothness3);
    half3 normalTS;
    SplatmapMix(IN, defaultSmoothness, splat_control, weight, mixedDiffuse, normalTS);

    half3 albedo = mixedDiffuse.rgb;
    half smoothness = mixedDiffuse.a;
    half metallic = dot(splat_control, half4(_Metallic0, _Metallic1, _Metallic2, _Metallic3));
    half3 specular = half3(0, 0, 0);
    half alpha = weight;

    InputData inputData;
    InitializeInputData(IN, normalTS, inputData);
    half4 color = LightweightFragmentPBR(inputData, albedo, metallic, specular, smoothness, /* occlusion */ 1.0, /* emission */ half3(0, 0, 0), alpha);

    SplatmapFinalColor(color, inputData.fogCoord);

    return half4(color.rgb, 1);
}

#endif // LIGHTWEIGHT_PASS_LIT_TERRAIN_INCLUDED