// 第 6 步：把材质属性放进 UnityPerMaterial 常量缓冲区，让 Shader 兼容 SRP Batcher。
Shader "Cookbook/Ch03/SRPBatcher"
{
    Properties
    {
        [MainTexture] _BaseMap ("Base Map", 2D) = "white" {}
        [MainColor]   _BaseColor ("Base Color", Color) = (1, 1, 1, 1)
        _Cutoff ("Alpha Cutoff", Range(0, 1)) = 0.5
        [Enum(UnityEngine.Rendering.CullMode)] _Cull ("Cull", Float) = 2
    }

    SubShader
    {
        Tags { "RenderType"="TransparentCutout" "RenderPipeline"="UniversalPipeline" "Queue"="AlphaTest" }

        // HLSLINCLUDE 里的代码会被自动拼到本 SubShader 每个 Pass 的 HLSLPROGRAM 前面。
        // 把 CBUFFER 写在这里，所有 Pass 的 UnityPerMaterial 布局天然一致。
        HLSLINCLUDE
        #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

        CBUFFER_START(UnityPerMaterial)
            float4 _BaseMap_ST;
            half4  _BaseColor;
            half   _Cutoff;
        CBUFFER_END

        // 纹理和采样器不是“数值”，不能也不需要放进 CBUFFER
        TEXTURE2D(_BaseMap);
        SAMPLER(sampler_BaseMap);
        ENDHLSL

        Pass
        {
            Name "Unlit"
            Tags { "LightMode"="UniversalForward" }
            Cull [_Cull]

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog

            struct Attributes
            {
                float4 positionOS : POSITION;
                float2 uv         : TEXCOORD0;
                half4  color      : COLOR;
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float2 uv         : TEXCOORD0;
                half4  color      : COLOR;
                float  fogFactor  : TEXCOORD1;
            };

            Varyings vert (Attributes input)
            {
                Varyings output;
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.uv = TRANSFORM_TEX(input.uv, _BaseMap);
                output.color = input.color;
                output.fogFactor = ComputeFogFactor(output.positionCS.z);
                return output;
            }

            half4 frag (Varyings input) : SV_Target
            {
                half4 col = SAMPLE_TEXTURE2D(_BaseMap, sampler_BaseMap, input.uv) * _BaseColor * input.color;
                clip(col.a - _Cutoff);
                col.rgb = MixFog(col.rgb, input.fogFactor);
                return half4(col.rgb, 1);
            }
            ENDHLSL
        }
    }
}