Shader "BriarQueen/UI/Menu Selection Brush"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (0.02, 0.018, 0.015, 0.86)

        _Reveal ("Reveal", Range(0, 1)) = 1
        _RevealSoftness ("Reveal Softness", Range(0.001, 0.35)) = 0.08
        _EdgeFade ("Edge Fade", Range(0.001, 0.35)) = 0.12
        _EndFade ("End Fade", Range(0.001, 0.35)) = 0.08
        _NoiseStrength ("Noise Strength", Range(0, 1)) = 0.18
        _NoiseScale ("Noise Scale", Range(1, 80)) = 24
        _StreakStrength ("Streak Strength", Range(0, 1)) = 0.22
        _StreakScale ("Streak Scale", Range(1, 80)) = 18

        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255
        _ColorMask ("Color Mask", Float) = 15

        [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0
    }

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

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

        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]

        Pass
        {
            Name "Default"

            CGPROGRAM
            #pragma vertex Vert
            #pragma fragment Frag
            #pragma target 2.0

            #include "UnityCG.cginc"
            #include "UnityUI.cginc"

            #pragma multi_compile_local _ UNITY_UI_CLIP_RECT
            #pragma multi_compile_local _ UNITY_UI_ALPHACLIP

            struct AppData
            {
                float4 vertex : POSITION;
                float4 color : COLOR;
                float2 texcoord : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                float2 uv : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            sampler2D _MainTex;
            fixed4 _Color;
            fixed4 _TextureSampleAdd;
            float4 _ClipRect;

            float _Reveal;
            float _RevealSoftness;
            float _EdgeFade;
            float _EndFade;
            float _NoiseStrength;
            float _NoiseScale;
            float _StreakStrength;
            float _StreakScale;

            float Hash21(float2 p)
            {
                p = frac(p * float2(123.34, 345.45));
                p += dot(p, p + 34.345);
                return frac(p.x * p.y);
            }

            float ValueNoise(float2 uv)
            {
                float2 i = floor(uv);
                float2 f = frac(uv);
                float2 u = f * f * (3.0 - 2.0 * f);

                float a = Hash21(i);
                float b = Hash21(i + float2(1.0, 0.0));
                float c = Hash21(i + float2(0.0, 1.0));
                float d = Hash21(i + float2(1.0, 1.0));

                return lerp(lerp(a, b, u.x), lerp(c, d, u.x), u.y);
            }

            Varyings Vert(AppData input)
            {
                Varyings output;

                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

                output.worldPosition = input.vertex;
                output.vertex = UnityObjectToClipPos(input.vertex);
                output.uv = input.texcoord;
                output.color = input.color * _Color;

                return output;
            }

            fixed4 Frag(Varyings input) : SV_Target
            {
                fixed4 color = (tex2D(_MainTex, input.uv) + _TextureSampleAdd) * input.color;

                float reveal = saturate(_Reveal);
                float halfWidth = reveal * 0.5;
                float distFromCenter = abs(input.uv.x - 0.5);
                float revealMask = 1.0 - smoothstep(halfWidth, halfWidth + _RevealSoftness, distFromCenter);
                revealMask *= smoothstep(0.0, 0.02, reveal);

                float verticalFade = smoothstep(0.0, _EdgeFade, input.uv.y)
                    * (1.0 - smoothstep(1.0 - _EdgeFade, 1.0, input.uv.y));
                float endFade = smoothstep(0.0, _EndFade, input.uv.x)
                    * (1.0 - smoothstep(1.0 - _EndFade, 1.0, input.uv.x));

                float noise = ValueNoise(input.uv * _NoiseScale);
                float streak = ValueNoise(float2(input.uv.x * _StreakScale, input.uv.y * 3.0));
                float surface = 1.0 - (noise * _NoiseStrength) - (streak * _StreakStrength);

                color.a *= revealMask * verticalFade * endFade * saturate(surface);

                #ifdef UNITY_UI_CLIP_RECT
                color.a *= UnityGet2DClipping(input.worldPosition.xy, _ClipRect);
                #endif

                #ifdef UNITY_UI_ALPHACLIP
                clip(color.a - 0.001);
                #endif

                return color;
            }
            ENDCG
        }
    }
}