Shader "Custom/HueTransDNPixelArtsGBuffer"
{
  Properties
  {
    [NoScaleOffset] _DayTex ("Day Texture", 2D) = "white" {}
    [NoScaleOffset] _NightTex ("Night Texture", 2D) = "black" {}
    //[MaterialToggle] _NightTexEnabled ("Night Texture Enabled", Float) = 1
    _Transpalent ("Transpalent Color", Color) = (1,0,1,1)
    _IDColor ("Color fo source object ID", Color) = (0,0,0,0)
    _RedTransfar ("RED Transfer Color", Color) = (1,0,0,1)
    _GreenTransfar ("GREEN Transfer Color", Color) = (0,1,0,1)
    _BlueTransfar ("BLUE Transfer Color", Color) = (0,0,1,1)
  }
  SubShader
  {
    Pass
    {
      Stencil
      {
        Comp Always
        Pass Replace
        Ref 128
      }

      Tags{ "LightMode" = "Deferred" }

      CGPROGRAM
      #pragma vertex vert
      #pragma fragment frag

      #include "UnityCG.cginc"

      struct appdata
      {
        float4 vertex : POSITION;
        float3 normal : NORMAL;
        float2 uv : TEXCOORD0;
      };

      struct v2f
      {
        float4 position : SV_POSITION;
        float3 normal : NORMAL;
        float2 uv : TEXCOORD0;
      };

      struct flagout
      {
        float4 gBuffer0 : SV_TARGET0;
        float4 gBuffer1 : SV_TARGET1;
        float4 gBuffer2 : SV_TARGET2;
        float4 gBuffer3 : SV_TARGET3;
        float depth: SV_DEPTH;
      };

      fixed3 _RedTransfar;
      fixed3 _GreenTransfar;
      fixed3 _BlueTransfar;

      sampler2D _DayTex;
      float4 _DayTex_ST;
      sampler2D _NightTex;
      float4 _NightTex_ST;
      float4 _IDColor;

      float _NightTexEnabled;
      fixed3 _Transpalent;

      void vert (in appdata v, out v2f o)
      {
        o.position = UnityObjectToClipPos(v.vertex);
        o.normal = UnityObjectToWorldNormal(v.normal);
        o.uv = TRANSFORM_TEX(v.uv, _DayTex);
      }

      inline fixed4 transferColor(in fixed4 srcCol) {
        float lowest = min(srcCol.r, min(srcCol.g, srcCol.b));
        fixed3 hueCol = srcCol.rgb - lowest;
        fixed3 hilight = fixed3(lowest,lowest,lowest);

        // test srcCol if the two of r,g,b are 0.
        float d1 = (1 - hueCol.r) * (1 - hueCol.g) * (1 - hueCol.b);
        float d2 = hueCol.r + hueCol.g + hueCol.b;
        float flag = step(d1 + d2, 1);

        fixed3 rgb = lerp(
        srcCol.rgb,
        _RedTransfar * hueCol.r + _GreenTransfar * hueCol.g + _BlueTransfar * hueCol.b + hilight,
        flag );


        return fixed4(rgb,1);
      }

      void frag (in v2f i, out flagout o)
      {
        fixed4 colDay = tex2D(_DayTex, i.uv);
        colDay = transferColor(colDay);
        // stop rendering if it is transpalent color.
        fixed3 diff = abs(colDay.rgb - _Transpalent.rgb);
        if(length(diff) < 0.0001) discard;

        fixed4 colNight = tex2D(_NightTex, i.uv);
        colNight = transferColor(colNight);

        // use 25% brightness of day texture, if night texture is disabled.
        colNight = lerp(colDay * 0.25, colNight, _NightTexEnabled);

        o.gBuffer0 = colDay;
        o.gBuffer3 = colNight;
        o.gBuffer2 = float4(i.normal, 0) * 0.5 + float4(0.5, 0.5, 0.5, 0);
        o.gBuffer1 = _IDColor;
        o.depth = i.position.z;
      }
      ENDCG
    }
  }
}