Shader "Soullies/DTM_RandomGridFloor"
{
    Properties
    {
        [HDR]_Color0("Color0", Color) = (1, 1, 1, 0)
        
        [Header(Pattern Settings)]
        _PatternSize("Pattern Size (X, Y)", Vector) = (2.0, 2.0, 0, 0)
        _GridDensity("Grid Density (Quantity Multiplier)", Float) = 1.0
        
        _TimeAngle("Time Angle (Speed)", Float) = 1.0
        
        [Header(Edge Settings)]
        _StepA("Step A", Range(0, 1)) = 0.293
        _StepB("Step B", Range(0, 1)) = 0.345

        [Header(Outer Enclosing Border)]
        [Toggle(_OUTER_BORDER_ON)] _EnableOuterBorder("Enable Outer Border", Float) = 0
        [HDR] _OuterBorderColor("Outer Border Color", Color) = (1, 1, 1, 1)
        _OuterBorderWidth("Outer Border Width", Range(0.0, 0.5)) = 0.02
        
        [Header(Render State)]
        [Enum(UnityEngine.Rendering.BlendMode)] _SrcBlend("Src Blend", Float) = 5 // SrcAlpha
        [Enum(UnityEngine.Rendering.BlendMode)] _DstBlend("Dst Blend", Float) = 10 // OneMinusSrcAlpha
        [Enum(Off, 0, On, 1)] _ZWrite("Z Write", Float) = 0
        [Enum(Front, Back, Off)] _CullMode("Cull Mode", Float) = 2 // Off
    }

    SubShader
    {
        Tags 
        { 
            "RenderPipeline" = "UniversalPipeline"
            "RenderType" = "Transparent" 
            "Queue" = "Transparent-300" 
            "UniversalMaterialType" = "Unlit"
            "IgnoreProjector" = "True"
        }

        Blend [_SrcBlend] [_DstBlend]
        ZWrite [_ZWrite]
        Cull [_CullMode]
        
        Pass
        {
            Name "ForwardOnly"
            Tags { "LightMode" = "UniversalForwardOnly" }

            HLSLPROGRAM
            // -------------------------------------
            // Target Config
            #pragma target 4.5
            #pragma prefer_hlslcc gles
            // DOTS and Instancing
            #pragma multi_compile_instancing
            #pragma multi_compile_fog
            // Feature Flags
            #pragma shader_feature_local _OUTER_BORDER_ON

            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS   : POSITION;
                float2 uv           : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 positionCS   : SV_POSITION;
                float3 positionWS   : TEXCOORD0;
                float2 uv           : TEXCOORD1;
                half   fogFactor    : TEXCOORD2;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            CBUFFER_START(UnityPerMaterial)
                half4 _Color0;
                float4 _PatternSize;
                float  _GridDensity;
                float  _TimeAngle;
                float  _StepA;
                float  _StepB;
                half4  _OuterBorderColor;
                float  _OuterBorderWidth;
            CBUFFER_END

            // -------------------------------------
            // Custom Helper Functions
            float2 VoronoiHash(float2 p)
            {
                p = float2(dot(p, float2(127.1, 311.7)), dot(p, float2(269.5, 183.3)));
                return frac(sin(p) * 43758.5453);
            }

            // Manhattan-based Voronoi optimized for Mobile URP
            float VoronoiDistance(float2 v, float t)
            {
                float2 n = floor(v);
                float2 f = frac(v);
                float minDist = 8.0;

                UNITY_UNROLL
                for (int j = -1; j <= 1; j++)
                {
                    UNITY_UNROLL
                    for (int i = -1; i <= 1; i++)
                    {
                        float2 g = float2((float)i, (float)j);
                        float2 o = VoronoiHash(n + g);
                        // Oscillating movement
                        o = sin(t + o * 6.2831853) * 0.5 + 0.5;
                        float2 r = f - g - o;
                        // Manhattan distance for rectangular frames
                        float d = 0.5 * (abs(r.x) + abs(r.y));
                        minDist = min(minDist, d);
                    }
                }
                return minDist;
            }

            // -------------------------------------
            // Vertex Shader
            Varyings vert(Attributes input)
            {
                Varyings output = (Varyings)0;
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_TRANSFER_INSTANCE_ID(input, output);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.positionCS = vertexInput.positionCS;
                output.positionWS = vertexInput.positionWS;
                output.uv         = input.uv;
                output.fogFactor  = ComputeFogFactor(vertexInput.positionCS.z);

                return output;
            }

            // -------------------------------------
            // Fragment Shader
            half4 frag(Varyings input) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(input);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);

                // ==========================================
                // 1. inner Grid Pattern Calculation
                // ==========================================
                float2 worldUV = input.positionWS.xz;

                // Density Multiplier: Higher density = smaller frames = more quantity
                float density = max(_GridDensity, 0.0001);
                float2 sizeDivisor = max(_PatternSize.xy, float2(0.0001, 0.0001)) / density;
                
                float2 scaledUV = worldUV / sizeDivisor;

                // Rotate 45 degrees
                float c = 0.707106; 
                float s = 0.707106;
                float2 rotatedUV = mul(scaledUV, float2x2(c, -s, s, c));

                // Time driven animation
                float t = _TimeAngle * _TimeParameters.x;
                
                // Voronoi mathematical noise
                float v = VoronoiDistance(rotatedUV, t);

                // Anti-aliased border mask computation
                float fw = fwidth(v);
                float edge1 = smoothstep(_StepA - fw, _StepA + fw, v);
                float edge2 = smoothstep(_StepB - fw, _StepB + fw, v);
                float gridAlphaMask = edge2 - edge1;

                half3 gridColor = _Color0.rgb;
                half  gridAlpha = gridAlphaMask * _Color0.a;

                // ==========================================
                // 2. Outer Enclosing Border
                // ==========================================
                half3 finalColor = gridColor;
                half  finalAlpha = gridAlpha;

                #if defined(_OUTER_BORDER_ON)
                    // Calculate distance to nearest UV edge
                    float2 edgeDist = min(input.uv, 1.0 - input.uv);
                    float closestEdge = min(edgeDist.x, edgeDist.y);
                    
                    // Uses fwidth for clean smoothstep transition at the edge
                    float borderfw = fwidth(closestEdge);
                    
                    // Creates a solid border with a smooth antialiased inner falloff
                    float borderMask = 1.0 - smoothstep(_OuterBorderWidth - borderfw, _OuterBorderWidth + borderfw, closestEdge);
                    
                    // Lerp grid to border
                    finalColor = lerp(gridColor, _OuterBorderColor.rgb, borderMask);
                    finalAlpha = lerp(gridAlpha, _OuterBorderColor.a, borderMask);
                #endif

                // Apply URP Fog
                finalColor = MixFog(finalColor, input.fogFactor);

                return half4(finalColor, finalAlpha);
            }
            ENDHLSL
        }
    }
    FallBack "Hidden/Universal Render Pipeline/FallbackError"
}