Shader "AIBIS/KiteFocusSprite"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1, 1, 1, 1)

        [Header(Focus Blur)]
        _BlurAmount ("Blur Amount", Range(0, 1)) = 0
        _BlurSize ("Blur Size", Range(0, 0.05)) = 0.012
        [HideInInspector] _UseSoftFocus ("Use Soft Focus", Float) = 0
        _DefocusBloom ("Defocus Highlight Bloom", Range(0, 1)) = 0.32
        _HaloStrength ("Large Circle Halo", Range(0, 0.6)) = 0.22
        _ChromaticFringe ("Lens Color Fringe", Range(0, 0.6)) = 0.14
        _DefocusVeil ("Defocus White Veil", Range(0, 0.3)) = 0.055

        // Required for SpriteMask (same contract as Sprites-Default / UI.Mask)
        [HideInInspector][PerRendererData] _StencilComp ("Stencil Comparison", Float) = 8
        [HideInInspector][PerRendererData] _Stencil ("Stencil ID", Float) = 0
        [HideInInspector][PerRendererData] _StencilOp ("Stencil Operation", Float) = 0
        [HideInInspector][PerRendererData] _StencilWriteMask ("Stencil Write Mask", Float) = 255
        [HideInInspector][PerRendererData] _StencilReadMask ("Stencil Read Mask", Float) = 255
        [HideInInspector] _ColorMask ("Color Mask", Float) = 15
    }

    SubShader
    {
        Tags
        {
            "Queue" = "Transparent"
            "IgnoreProjector" = "True"
            "RenderType" = "Transparent"
            "PreviewType" = "Plane"
            "CanUseSpriteAtlas" = "True"
        }

        Cull Off
        Lighting Off
        ZWrite Off
        Blend One OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 3.0
            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float4 color : COLOR;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                float2 uv : TEXCOORD0;
            };

            sampler2D _MainTex;
            float4 _MainTex_TexelSize;
            fixed4 _Color;
            float _BlurAmount;
            float _BlurSize;
            float _UseSoftFocus;
            float _DefocusBloom;
            float _HaloStrength;
            float _ChromaticFringe;
            float _DefocusVeil;

            v2f vert(appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.color = v.color * _Color;
                o.uv = v.uv;
                return o;
            }

            half4 sampleTex(float2 uv)
            {
                // 边界外按透明，避免 saturate 夹边造成硬切
                if (uv.x < 0.0 || uv.x > 1.0 || uv.y < 0.0 || uv.y > 1.0)
                    return half4(0, 0, 0, 0);
                return tex2D(_MainTex, uv);
            }

            half4 samplePremultiplied(float2 uv)
            {
                half4 color = sampleTex(uv);
                color.rgb *= color.a;
                return color;
            }

            // 圆形光圈核：比高斯更接近真实镜头的弥散圆，且不会出现十字形拖影。
            half4 ApertureDisc(float2 uv, float radius)
            {
                half4 result = samplePremultiplied(uv) * 0.12;
                const half w = 0.044;

                // 内圈
                result += samplePremultiplied(uv + float2( 0.38,  0.00) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.38,  0.00) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.00,  0.38) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.00, -0.38) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.27,  0.27) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.27,  0.27) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.27, -0.27) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.27, -0.27) * radius) * w;

                // 外圈使用不规则角度，避免规则采样形成振铃或星芒。
                result += samplePremultiplied(uv + float2( 0.98,  0.05) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.82,  0.55) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.43,  0.90) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.16,  0.98) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.69,  0.72) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.99,  0.10) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.80, -0.58) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.36, -0.92) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.22, -0.97) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.72, -0.68) * radius) * w;
                result += samplePremultiplied(uv + float2( 0.94, -0.31) * radius) * w;
                result += samplePremultiplied(uv + float2(-0.48,  0.86) * radius) * w;
                return result;
            }

            half4 WideHalo(float2 uv, float radius)
            {
                half4 result = 0;
                result += samplePremultiplied(uv + float2( 1.00,  0.00) * radius);
                result += samplePremultiplied(uv + float2( 0.71,  0.71) * radius);
                result += samplePremultiplied(uv + float2( 0.00,  1.00) * radius);
                result += samplePremultiplied(uv + float2(-0.71,  0.71) * radius);
                result += samplePremultiplied(uv + float2(-1.00,  0.00) * radius);
                result += samplePremultiplied(uv + float2(-0.71, -0.71) * radius);
                result += samplePremultiplied(uv + float2( 0.00, -1.00) * radius);
                result += samplePremultiplied(uv + float2( 0.71, -0.71) * radius);
                return result * 0.125;
            }

            half4 SoftFocusBlur(float2 uv, float radius)
            {
                float nearRadius = radius * 0.48;
                half4 result = samplePremultiplied(uv) * 0.20;

                result += samplePremultiplied(uv + float2( nearRadius, 0)) * 0.08;
                result += samplePremultiplied(uv + float2(-nearRadius, 0)) * 0.08;
                result += samplePremultiplied(uv + float2(0,  nearRadius)) * 0.08;
                result += samplePremultiplied(uv + float2(0, -nearRadius)) * 0.08;

                result += samplePremultiplied(uv + float2( nearRadius,  nearRadius)) * 0.055;
                result += samplePremultiplied(uv + float2(-nearRadius,  nearRadius)) * 0.055;
                result += samplePremultiplied(uv + float2( nearRadius, -nearRadius)) * 0.055;
                result += samplePremultiplied(uv + float2(-nearRadius, -nearRadius)) * 0.055;

                result += samplePremultiplied(uv + float2( radius, 0)) * 0.04;
                result += samplePremultiplied(uv + float2(-radius, 0)) * 0.04;
                result += samplePremultiplied(uv + float2(0,  radius)) * 0.04;
                result += samplePremultiplied(uv + float2(0, -radius)) * 0.04;

                result += samplePremultiplied(uv + float2( radius,  radius)) * 0.025;
                result += samplePremultiplied(uv + float2(-radius,  radius)) * 0.025;
                result += samplePremultiplied(uv + float2( radius, -radius)) * 0.025;
                result += samplePremultiplied(uv + float2(-radius, -radius)) * 0.025;
                return result;
            }

            fixed4 frag(v2f i) : SV_Target
            {
                float blurAmt = saturate(_BlurAmount);
                half4 sharp = sampleTex(i.uv);

                if (blurAmt < 0.001)
                {
                    half4 col = sharp * i.color;
                    col.rgb *= col.a;
                    return col;
                }

                float2 texel = max(abs(_MainTex_TexelSize.xy), float2(1e-5, 1e-5));
                float radius = (length(texel) * 0.5 + _BlurSize) * (0.28 + blurAmt * 1.72);

                if (_UseSoftFocus > 0.5)
                {
                    half4 softBlurred = SoftFocusBlur(i.uv, radius);
                    half4 softSharp = sharp;
                    softSharp.rgb *= softSharp.a;
                    half4 softColor = lerp(softSharp, softBlurred, smoothstep(0.0, 1.0, blurAmt));
                    softColor.rgb *= i.color.rgb * i.color.a;
                    softColor.a *= i.color.a;
                    return softColor;
                }

                half4 disc = ApertureDisc(i.uv, radius);
                half4 halo = WideHalo(i.uv, radius * 1.85);
                half4 blurred = lerp(disc, halo, saturate(_HaloStrength * blurAmt));

                // 很轻的 RGB 焦平面差异，避免单纯软件模糊的塑料感。
                float2 fringe = float2(0.73, 0.41) * radius * _ChromaticFringe * blurAmt;
                half4 fringeR = samplePremultiplied(i.uv + fringe);
                half4 fringeB = samplePremultiplied(i.uv - fringe);
                blurred.r = lerp(blurred.r, fringeR.r, _ChromaticFringe * blurAmt);
                blurred.b = lerp(blurred.b, fringeB.b, _ChromaticFringe * blurAmt);

                // 参考片中的失焦会让亮部扩散并稍微泛白，但保留在物体 alpha 内。
                half luminance = dot(blurred.rgb, half3(0.2126, 0.7152, 0.0722));
                half highlight = saturate(luminance - blurred.a * 0.42);
                blurred.rgb += highlight * _DefocusBloom * blurAmt;
                blurred.rgb += blurred.a * _DefocusVeil * blurAmt;

                half4 sharpPremul = sharp;
                sharpPremul.rgb *= sharpPremul.a;
                float mixT = smoothstep(0.0, 1.0, blurAmt);
                half4 col = lerp(sharpPremul, blurred, mixT);
                col.rgb *= i.color.rgb * i.color.a;
                col.a *= i.color.a;
                return col;
            }
            ENDCG
        }
    }
}