Shader "BriarQueen/UI/Dissolve Blue Particles"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1, 1, 1, 1)

        _DissolveAmount ("Dissolve Amount", Range(0, 1)) = 0
        _EdgeWidth ("Edge Width", Range(0.001, 0.25)) = 0.06
        _ParticleColor ("Particle Color", Color) = (0.15, 0.65, 1, 1)
        _ParticleIntensity ("Particle Intensity", Range(0, 8)) = 2.5
        _ParticleDensity ("Particle Density", Range(0, 1)) = 0.82
        _ParticleScale ("Particle Scale", Range(10, 250)) = 95
        _ParticleDrift ("Particle Drift", Range(0, 3)) = 0.65

        _NoiseScale ("Noise Scale", Range(1, 80)) = 24
        _NoiseStrength ("Noise Strength", Range(0, 1)) = 0.55
        [Toggle] _ReverseDirection ("Reverse Direction", Float) = 0

        _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 _DissolveAmount;
            float _EdgeWidth;
            fixed4 _ParticleColor;
            float _ParticleIntensity;
            float _ParticleDensity;
            float _ParticleScale;
            float _ParticleDrift;
            float _NoiseScale;
            float _NoiseStrength;
            float _ReverseDirection;

            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);
            }

            float DissolveNoise(float2 uv)
            {
                float n = ValueNoise(uv * _NoiseScale);
                n += ValueNoise(uv * _NoiseScale * 2.13 + 17.0) * 0.5;
                n += ValueNoise(uv * _NoiseScale * 4.07 + 43.0) * 0.25;
                n /= 1.75;

                float verticalBias = lerp(uv.y, 1.0 - uv.y, step(0.5, _ReverseDirection));
                return saturate(lerp(verticalBias, n, _NoiseStrength));
            }

            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;

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

                float amount = saturate(_DissolveAmount);
                float dissolveNoise = DissolveNoise(input.uv);
                float visible = smoothstep(amount - _EdgeWidth, amount + _EdgeWidth, dissolveNoise);
                visible = amount <= 0.001 ? 1.0 : visible;
                visible = amount >= 0.999 ? 0.0 : visible;

                float edge = 1.0 - smoothstep(0.0, _EdgeWidth, abs(dissolveNoise - amount));
                edge *= step(0.001, amount) * step(amount, 0.999);

                float2 particleUv = input.uv * _ParticleScale;
                particleUv.y += _Time.y * _ParticleDrift;
                particleUv.x += sin(_Time.y + input.uv.y * 12.0) * 0.35;

                float particles = step(_ParticleDensity, Hash21(floor(particleUv)));
                particles *= edge;
                particles *= visible;

                color.rgb += _ParticleColor.rgb * particles * _ParticleIntensity;
                color.rgb = lerp(color.rgb, _ParticleColor.rgb, edge * 0.35);
                color.a *= visible;

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

                return color;
            }
            ENDCG
        }
    }
}