// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unlit/LightEffect"
{
    Properties
    {
        _MainTex("Base (RGB)", 2D) = "white" {}
        _Strength("Gradient Strength", Range(0,1)) = 1
        _TopColor("Top Color", Color) = (1,1,1,1)
        _BottomColor("Bottom Color", Color) = (0,0,0,0)
        _GradientEnd("Gradient End Position", Range(0,1)) = 1
        _LightPosition("Light Position", Vector) = (0.5, 1.0, 0, 0)
        _NoiseScale1("Noise Scale 1", Float) = 12.0
        _NoiseScale2("Noise Scale 2", Float) = 2.0
        _AlphaCutoff("Alpha Cutoff", Range(0,1)) = 0.0
    }

    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue"="Transparent" }
        LOD 100
        Pass
        {
            Blend SrcAlpha OneMinusSrcAlpha
            ZWrite Off

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

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

            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv : TEXCOORD0;
            };

            sampler2D _MainTex;
            float _Strength;
            float4 _TopColor;
            float4 _BottomColor;
            float _GradientEnd;
            float4 _LightPosition;
            float _NoiseScale1;
            float _NoiseScale2;
            float _AlphaCutoff;

            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
            // Perlin noise implementation
            float fade(float t) {
                return t * t * t * (t * (t * 6 - 15) + 10);
            }

            float lerp(float a, float b, float t) {
                return a + t * (b - a);
            }

            float grad(int hash, float x, float y) {
                int h = hash & 7;
                float u = h < 4 ? x : y;
                float v = h < 4 ? y : x;
                return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
            }

            int perm(int x) {
                // Simple permutation function for shader use
                return (x * 34 + 1) * x % 289;
            }

            float noise(float2 uv)
            {
                float2 p = floor(uv);
                float2 f = frac(uv);

                int X = int(p.x);
                int Y = int(p.y);

                int A = perm(X) + Y;
                int B = perm(X + 1) + Y;

                float res = lerp(
                    lerp(grad(perm(A), f.x, f.y), grad(perm(B), f.x - 1, f.y), fade(f.x)),
                    lerp(grad(perm(A + 1), f.x, f.y - 1), grad(perm(B + 1), f.x - 1, f.y - 1), fade(f.x)),
                    fade(f.y)
                );
                return res * 0.5 + 0.5; // Normalize to [0,1]
            }

            fixed4 frag(v2f i) : SV_Target
            {
                // Remap uv.y so gradient ends at _GradientEnd
                // float t = saturate(i.uv.y / max(_GradientEnd, 0.0001));
                // float2 center = float2(0.5, 1.0);
                float noiseValue = noise(i.uv*_NoiseScale1 + float2(_Time.x*1.3, _Time.y*0.2));
                float2 uvNorm = (i.uv - _LightPosition.xy + 0.1*float2(noiseValue, noiseValue));
                //uvNorm.x /= (_GradientEnd); // scale x to match circle aspect
                float dist = 1.0 - length(uvNorm);
                // dist=1.0-(pow(1.0 - dist, 2.0)); // Sharpen the edge
                float t = saturate((dist - (1.0 - _GradientEnd)) / _GradientEnd);
                

                // Apply ease (smoothstep) for non-linear gradient
                t = smoothstep(0.0, 1.0-_Strength*0.5, t);
                float n = noise(i.uv *_NoiseScale2 + _Time.yx * 0.8);
                t *= n; // Adjust 0.1 for edge softness
                t = saturate(t);
                t=1.0-pow(1.0 - t, 1.5); // Make the gradient more pronounced
                

                float4 gradColor = _BottomColor*(1.0-t)+_TopColor*t;
                // float4 texColor = tex2D(_MainTex, i.uv);
                // return lerp(float4(0.0, 0.0, 0.0, 0.0), gradColor, _Strength);
                gradColor.a*=_AlphaCutoff;

                return gradColor;
                //  return gradColor;
            }
            ENDCG
        }
    }
}