Shader "Custom/SpriteDissolve"
{
    // 敌人死亡消隐 Shader
    // 基于噪声的溶解效果，带发光边缘
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Color ("颜色", Color) = (1, 1, 1, 1)
        
        [Header(Dissolve)]
        _DissolveAmount ("溶解进度", Range(0, 1)) = 0
        _DissolveEdgeWidth ("边缘宽度", Range(0, 0.3)) = 0.05
        _DissolveEdgeColor ("边缘颜色", Color) = (0.3, 0.6, 1, 1)
        _DissolveNoiseScale ("噪声缩放", Float) = 10
        
        // 阴影设置（保持与项目一致）
        [MaterialToggle] _CastShadow ("投射阴影", Float) = 0
    }
    SubShader
    {
        Tags
        {
            "RenderPipeline" = "UniversalPipeline"
            "Queue" = "Transparent"
            "RenderType" = "Transparent"
        }
        
        Blend SrcAlpha OneMinusSrcAlpha
        ZWrite Off
        Cull Off

        Pass
        {
            Name "SpriteDissolve"
            
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

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

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float2 uv : TEXCOORD0;
                float4 color : COLOR;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);
            
            half4 _Color;
            half _DissolveAmount;
            half _DissolveEdgeWidth;
            half4 _DissolveEdgeColor;
            float _DissolveNoiseScale;

            // 简单的哈希噪声
            float hash(float2 p)
            {
                float3 p3 = frac(float3(p.xyx) * 0.1031);
                p3 += dot(p3, p3.yzx + 33.33);
                return frac((p3.x + p3.y) * p3.z);
            }

            // 值噪声（平滑插值）
            float valueNoise(float2 p)
            {
                float2 i = floor(p);
                float2 f = frac(p);
                f = f * f * (3.0 - 2.0 * f); // smoothstep
                
                float a = hash(i);
                float b = hash(i + float2(1, 0));
                float c = hash(i + float2(0, 1));
                float d = hash(i + float2(1, 1));
                
                return lerp(lerp(a, b, f.x), lerp(c, d, f.x), f.y);
            }

            // 分形噪声（多层叠加）
            float fbm(float2 p)
            {
                float value = 0.0;
                float amplitude = 0.5;
                for (int i = 0; i < 4; i++)
                {
                    value += amplitude * valueNoise(p);
                    p *= 2.0;
                    amplitude *= 0.5;
                }
                return value;
            }

            Varyings vert(Attributes input)
            {
                Varyings output;
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                
                output.positionCS = TransformObjectToHClip(input.positionOS.xyz);
                output.uv = input.uv;
                output.color = input.color;
                return output;
            }

            half4 frag(Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                
                half4 texColor = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, input.uv);
                half4 color = texColor * _Color * input.color;
                
                // 如果 alpha 太小，直接丢弃
                if (color.a < 0.01)
                    discard;
                
                // 计算噪声
                float noise = fbm(input.uv * _DissolveNoiseScale);
                
                // 溶解判定
                float dissolveEdge = smoothstep(
                    _DissolveAmount - _DissolveEdgeWidth,
                    _DissolveAmount + _DissolveEdgeWidth,
                    noise
                );
                
                // 完全溶解区域
                if (noise < _DissolveAmount)
                    discard;
                
                // 边缘发光
                half edgeGlow = (1.0 - dissolveEdge) * step(_DissolveAmount, noise);
                color.rgb += _DissolveEdgeColor.rgb * edgeGlow * _DissolveEdgeColor.a;
                
                // 整体淡出（溶解后期整体变淡）
                color.a *= lerp(1.0, 0.3, _DissolveAmount);
                
                return color;
            }
            ENDHLSL
        }
    }
    FallBack "Sprites/Default"
}