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

        _TopColor ("Top Color (White)", Color) = (1.0, 0.98, 0.95, 1.0)
        _MiddleColor ("Middle Color (Light Gold)", Color) = (1.0, 0.82, 0.4, 1.0)
        _BottomColor ("Bottom Color (Amber Gold)", Color) = (0.82, 0.5, 0.1, 1.0)
        _MidPoint ("Gradient Mid Point", Range(0.1, 0.9)) = 0.35

        _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
    }

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

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

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
            };

            fixed4 _Color;
            fixed4 _TopColor;
            fixed4 _MiddleColor;
            fixed4 _BottomColor;
            float _MidPoint;
            sampler2D _MainTex;
            float4 _MainTex_ST;
            fixed4 _TextureSampleAdd;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.worldPosition = IN.vertex;
                OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);
                OUT.texcoord = TRANSFORM_TEX(IN.texcoord, _MainTex);
                
                float y = saturate(IN.texcoord.y);
                fixed4 gradColor;
                if (y > _MidPoint)
                {
                    float t = (y - _MidPoint) / (1.0 - _MidPoint);
                    gradColor = lerp(_MiddleColor, _TopColor, t);
                }
                else
                {
                    float t = y / _MidPoint;
                    gradColor = lerp(_BottomColor, _MiddleColor, t);
                }

                OUT.color = IN.color * _Color * gradColor;
                return OUT;
            }

            fixed4 frag(v2f IN) : SV_Target
            {
                half4 color = (tex2D(_MainTex, IN.texcoord) + _TextureSampleAdd) * IN.color;
                return color;
            }
            ENDCG
        }
    }
}