Shader "Unlit/NewUnlitTerrainShader"
{
    Properties
    {
        _MainTex ("Texture Array", 2DArray) = "white" {}
        _TexNo ("TexNo", 2D) = "white" {}
        _MaskNo ("MaskNo", 2D) = "black" {}
        _MaskTex ("Mask", 2DArray) = "black" {}
        _BorderColor ("BorderColor", Color) = (1,1,1,1)
        _BorderWidth ("BorderWidth", Range(0,0.1)) = 0.05
        _MapSize ("Map Size", Vector) = (256,256,0,0)
        _TileSize ("Tile Size", Vector) = (1,1,0,0)
    }
    SubShader
    {
        Tags
        {
            "RenderType"="Opaque"
        }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0; // 用于采样 _TexNo 与 _MaskNo
                float2 uv2 : TEXCOORD1; // 用于采样纹理数组 _MainTex 与 _MaskTex
                float4 vertex : SV_POSITION;
            };

            UNITY_DECLARE_TEX2DARRAY(_MainTex);
            sampler2D _TexNo;
            sampler2D _MaskNo;
            UNITY_DECLARE_TEX2DARRAY(_MaskTex);

            float4 _TexNo_TexelSize;
            float4 _BorderColor;
            float _BorderWidth;
            float4 _MapSize; // 整个地图的宽高（X: Width, Y: Height）
            float4 _TileSize; // 每个瓦块的尺寸（默认 1x1）

            v2f vert(appdata v)
            {
                v2f o;
                float4 worldPos = mul(unity_ObjectToWorld, v.vertex);
                // 整体 UV：以整个地图为基准归一化
                o.uv = worldPos.xz / _MapSize.xy;
                // 局部 tile 内 UV：取 worldPos.xz 除以瓦块尺寸后的小数部分
                o.uv2 = frac(worldPos.xz / _TileSize.xy);
                o.vertex = UnityObjectToClipPos(v.vertex);
                return o;
            }

            // 根据遮罩与纹理编号混合采样
            float4 Blend(float4 color, float2 uv, float mask, int layer)
            {
                float4 col2 = UNITY_SAMPLE_TEX2DARRAY(_MainTex, float3(uv, layer));
                int idx = round(mask * 16);
                float4 maskTexCol = UNITY_SAMPLE_TEX2DARRAY(_MaskTex, float3(uv, idx));
                return lerp(color, col2, maskTexCol);
            }

            int GetTexNo(float f)
            {
                float idx = f * 64;
                return round(idx);
            }

            fixed4 frag(v2f i) : SV_Target
            {
                // 微调 uv（模拟原来的偏移）
                float2 uv = i.uv + float2(0, _TexNo_TexelSize.y);
                float4 texNo = tex2D(_TexNo, uv);
                int layer1 = GetTexNo(texNo.r);
                int layer2 = GetTexNo(texNo.g);
                int layer3 = GetTexNo(texNo.b);
                int layer4 = GetTexNo(texNo.a);

                float4 maskNo = tex2D(_MaskNo, uv);

                float4 col = UNITY_SAMPLE_TEX2DARRAY(_MainTex, float3(i.uv2, layer1));
                // if (layer2 > 0)
                //     col = Blend(col, i.uv2, maskNo.g, layer2);
                // if (layer3 > 0)
                //     col = Blend(col, i.uv2, maskNo.b, layer3);
                // if (layer4 > 0)
                //     col = Blend(col, i.uv2, maskNo.a, layer4);

                // // 显示边框，当局部 UV 靠近边缘时显示边框颜色
                // if (i.uv2.x < _BorderWidth || i.uv2.y < _BorderWidth || i.uv2.x > 1 - _BorderWidth || i.uv2.y > 1 -
                //     _BorderWidth)
                // {
                //     col = _BorderColor;
                // }
                return col;
            }
            ENDCG
        }
    }
}