Shader "Custom/UniversalLiquidSurface_DebugContact"
{
    Properties
    {
        // Tryb (zostaw 3 = River)
        [Enum(River,3)] _SurfaceType ("Surface Type", Float) = 3

        // Tekstury
        _MainTex ("Main Texture", 2D) = "white" {}
        _NormalMap ("Normal Map", 2D) = "bump" {}
        _FoamTex ("Foam Texture", 2D) = "white" {}

        // Kolory
        _ShallowColor ("Shallow Water Color (RGB+A)", Color) = (0.1, 0.9, 0.8, 0.3)
        _DeepColor ("Deep Water Color (RGB+A)", Color) = (0.0, 0.1, 0.3, 0.9)
        _RiverReflectionColor ("River Reflection Color", Color) = (0.4, 0.6, 0.9, 1)

        // Parametry kontaktu (okno tolerancji głębokości w przestrzeni kamery)
        _ContactMin ("Contact Min (eye-depth tolerance)", Float) = 0.02
        _ContactMax ("Contact Max (eye-depth tolerance)", Float) = 0.15

        // Przepływ i tilingi
        _RiverFlowSpeedX ("River Flow Speed X", Float) = 0.25
        _RiverFlowSpeedY ("River Flow Speed Y", Float) = 0.15
        _RiverMainTiling ("River Main Tiling", Float) = 1.0
        _RiverNormalTiling ("River Normal Tiling", Float) = 1.0
        _RiverFoamTiling ("River Foam Tiling", Float) = 3.0
        _RiverFoamPulseSpeed ("River Foam Pulse Speed", Float) = 2.0

        // Refleksy i piana
        _FoamStrength ("Foam Strength", Float) = 0.5
        _ReflectionStrength ("Reflection Strength", Float) = 0.5
        _RiverEdgeFoam ("River Edge Foam Strength", Float) = 0.5
    }

    SubShader
    {
        Tags { "RenderPipeline"="UniversalRenderPipeline" "RenderType"="Transparent" "Queue"="Transparent" }
        Blend SrcAlpha OneMinusSrcAlpha
        ZWrite Off

        Pass
        {
            Name "ForwardUnlit"
            Tags { "LightMode"="UniversalForward" }

            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes {
                float4 positionOS : POSITION;
                float2 uv : TEXCOORD0;
                float3 normalOS : NORMAL;
            };

            struct Varyings {
                float4 positionHCS : SV_POSITION;
                float2 uv : TEXCOORD0;
                float3 normalWS : TEXCOORD1;
                float3 viewDirWS : TEXCOORD2;
            };

            // Tekstury i samplery
            TEXTURE2D(_MainTex);      SAMPLER(sampler_MainTex);
            TEXTURE2D(_NormalMap);    SAMPLER(sampler_NormalMap);
            TEXTURE2D(_FoamTex);      SAMPLER(sampler_FoamTex);

            // Depth z URP
            TEXTURE2D(_CameraDepthTexture);
            SAMPLER(sampler_CameraDepthTexture);

            // ST
            float4 _MainTex_ST;
            float4 _NormalMap_ST;
            float4 _FoamTex_ST;

            // Parametry
            float _SurfaceType;

            float4 _ShallowColor;
            float4 _DeepColor;
            float4 _RiverReflectionColor;

            float _ContactMin;
            float _ContactMax;

            float _RiverFlowSpeedX;
            float _RiverFlowSpeedY;
            float _RiverMainTiling;
            float _RiverNormalTiling;
            float _RiverFoamTiling;
            float _RiverFoamPulseSpeed;

            float _FoamStrength;
            float _ReflectionStrength;
            float _RiverEdgeFoam;

            // Helpers
            float2 ApplyST(float2 uv, float4 st) { return uv * st.xy + st.zw; }

            float2 ComputeScreenUV(float4 positionHCS)
            {
                float2 uv = positionHCS.xy / positionHCS.w; // clip -> NDC
                uv = uv * 0.5 + 0.5;                        // -1..1 -> 0..1
                return uv;
            }

            Varyings vert (Attributes IN)
            {
                Varyings OUT;
                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
                OUT.uv = IN.uv;
                OUT.normalWS = TransformObjectToWorldNormal(IN.normalOS);
                OUT.viewDirWS = GetWorldSpaceViewDir(TransformObjectToWorld(IN.positionOS.xyz));
                return OUT;
            }

            half4 frag (Varyings IN) : SV_Target
            {
                if (_SurfaceType == 3) // River (debug pas kontaktu)
                {
                    // Przepływ UV
                    float2 uvFlow1 = ApplyST(IN.uv * _RiverMainTiling, _MainTex_ST);
                    uvFlow1.y += _Time.y * _RiverFlowSpeedY;

                    float2 uvFlow2 = ApplyST(IN.uv * _RiverMainTiling, _MainTex_ST);
                    uvFlow2.x += _Time.y * _RiverFlowSpeedX;

                    // Normal distortion
                    half4 nTex = SAMPLE_TEXTURE2D(_NormalMap, sampler_NormalMap, IN.uv * _RiverNormalTiling);
                    float2 nDistort = (nTex.xy * 2.0 - 1.0) * 0.05;
                    float2 uvDistorted = (uvFlow1 + uvFlow2) * 0.5 + nDistort;

                    // Podstawowy kolor (nieużywany w debug, ale zostawiony dla spójności)
                    half3 riverTex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, uvDistorted).rgb;

                    // Depth
                    float2 screenUV = ComputeScreenUV(IN.positionHCS);
                    float rawSceneDepth = SAMPLE_TEXTURE2D(_CameraDepthTexture, sampler_CameraDepthTexture, screenUV).r;

                    // Brak obiektu pod wodą -> czarne (brak kontaktu)
                    if (rawSceneDepth >= 0.9999)
                    {
                        return half4(0,0,0,1);
                    }

                    float sceneDepth   = LinearEyeDepth(rawSceneDepth, _ZBufferParams);
                    float surfaceDepth = LinearEyeDepth(IN.positionHCS.z / IN.positionHCS.w, _ZBufferParams);

                    // Absolutna różnica głębokości
                    float depthDelta = abs(sceneDepth - surfaceDepth);

                    // Okno tolerancji z miękkimi krawędziami (1 = kontakt, 0 = brak)
                    float contactBand = 1.0 - smoothstep(_ContactMin, _ContactMax, depthDelta);

                    // Zwracamy maskę kontaktową jako grayscale (DEBUG)
                    return half4(contactBand.xxx, 1.0);
                }

                // Fallback magenta jeśli SurfaceType != River
                return half4(1,0,1,1);
            }
            ENDHLSL
        }
    }
}