Shader "GAME/StylizedSky"
{
    Properties
    {
        [Header(Sky Gradient   Day)][Space]
        [HDR] _DayZenith("Day Zenith", Color) = (0.18,0.42,0.78,1)
        [HDR] _DayHorizon("Day Horizon", Color) = (0.62,0.78,0.92,1)

        [Header(Sky Gradient   Night)][Space]
        [HDR] _NightZenith("Night Zenith", Color) = (0.01,0.02,0.06,1)
        [HDR] _NightHorizon("Night Horizon", Color) = (0.04,0.06,0.12,1)

        [Header(Twilight)][Space]
        [HDR] _TwilightColor("Twilight Tint (dawn/dusk)", Color) = (0.95,0.45,0.25,1)
        _HorizonSharpness("Horizon Sharpness", Range(0.2,6)) = 2.2

        [Header(Sun)][Space]
        [HDR] _SunColor("Sun Color", Color) = (1.0,0.95,0.85,1)
        _SunSize("Sun Size", Range(0.0005,0.2)) = 0.03
        [HDR] _SunGlowColor("Sun Glow Color", Color) = (1.0,0.7,0.4,1)
        _SunGlowSize("Sun Glow Falloff", Range(1,512)) = 64
        _SunGlowStrength("Sun Glow Strength", Range(0,4)) = 1.0

        [Header(Clouds)][Space]
        [HDR] _CloudColor("Cloud Color (lit)", Color) = (1.0,0.98,0.95,1)
        [HDR] _CloudShadowColor("Cloud Color (shadow)", Color) = (0.55,0.6,0.72,1)
        _CloudCoverage("Cloud Coverage", Range(0,1)) = 0.5
        _CloudSoftness("Cloud Edge Softness", Range(0.01,0.6)) = 0.2
        _CloudScale("Cloud Scale", Range(0.2,4)) = 1.2
        _CloudSpeed("Cloud Speed", Range(0,0.2)) = 0.01
        _CloudWindDir("Cloud Wind Dir (xy)", Vector) = (1,0.3,0,0)

        [Header(Stars)][Space]
        _StarDensity("Star Density", Range(0,0.2)) = 0.04
        _StarTwinkleSpeed("Star Twinkle Speed", Range(0,8)) = 2.0

        [Header(Shooting Stars)][Space]
        [HDR] _ShootingStarColor("Shooting Star Color", Color) = (1,1,0.9,1)
        _ShootingStarRate("Shooting Star Rate", Range(0.01,0.5)) = 0.06

        [Header(Exposure)][Space]
        _Exposure("Exposure", Range(0,4)) = 1.0
    }

    SubShader
    {
        Tags
        {
            "RenderType" = "Background"
            "Queue" = "Background"
            "PreviewType" = "Skybox"
            "RenderPipeline" = "UniversalPipeline"
        }

        // =================================================================================
        //  Skybox (rendu par RenderSettings.skybox via le pass DrawSkybox d'URP)
        // =================================================================================
        Pass
        {
            Name "StylizedSky"
            Cull Off
            ZWrite Off
            ZTest LEqual

            HLSLPROGRAM
            #pragma target 3.0
            #pragma vertex SkyVertex
            #pragma fragment SkyFragment

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

            CBUFFER_START(UnityPerMaterial)
                half4 _DayZenith;
                half4 _DayHorizon;
                half4 _NightZenith;
                half4 _NightHorizon;
                half4 _TwilightColor;
                float _HorizonSharpness;

                half4 _SunColor;
                float _SunSize;
                half4 _SunGlowColor;
                float _SunGlowSize;
                float _SunGlowStrength;

                half4 _CloudColor;
                half4 _CloudShadowColor;
                float _CloudCoverage;
                float _CloudSoftness;
                float _CloudScale;
                float _CloudSpeed;
                float4 _CloudWindDir;

                float _StarDensity;
                float _StarTwinkleSpeed;

                half4 _ShootingStarColor;
                float _ShootingStarRate;

                float _Exposure;
            CBUFFER_END

            struct Attributes
            {
                float4 positionOS : POSITION;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct Varyings
            {
                float4 positionCS : SV_POSITION;
                float3 viewDirOS  : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
            };

            // La skybox est dessinée autour de la caméra : la position objet du mesh est
            // directement la direction de vue. On la transmet brute et on la normalise au fragment.
            Varyings SkyVertex(Attributes IN)
            {
                Varyings OUT = (Varyings)0;
                UNITY_SETUP_INSTANCE_ID(IN);
                UNITY_TRANSFER_INSTANCE_ID(IN, OUT);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);

                OUT.positionCS = TransformObjectToHClip(IN.positionOS.xyz);
                OUT.viewDirOS = IN.positionOS.xyz;
                return OUT;
            }

            // Compose le ciel dans l'ordre fond -> nuages -> soleil -> étoiles -> filantes.
            // Toute l'animation lit _SkyTime (synchronisé) et tout dépend de _SunDirection /
            // _TimeOfDay (synchronisés), donc le rendu est identique sur tous les clients.
            half4 SkyFragment(Varyings IN) : SV_Target
            {
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(IN);

                float3 viewDir = normalize(IN.viewDirOS);

                float3 col = SkyGradient(viewDir,
                    _DayZenith.rgb, _DayHorizon.rgb,
                    _NightZenith.rgb, _NightHorizon.rgb,
                    _TwilightColor.rgb, _HorizonSharpness);

                col += SunGlow(viewDir, _SunGlowColor.rgb, _SunGlowSize, _SunGlowStrength);

                float4 clouds = Clouds(viewDir, _SkyTime * _CloudSpeed,
                    _CloudColor.rgb, _CloudShadowColor.rgb,
                    _CloudCoverage, _CloudSoftness, _CloudScale, _CloudWindDir.xy);
                col = col * (1.0 - clouds.a) + clouds.rgb;

                col += SunDisk(viewDir, _SunColor.rgb, _SunSize) * (1.0 - clouds.a);

                col += Stars(viewDir, _StarDensity, _StarTwinkleSpeed, _SkyTime) * (1.0 - clouds.a);
                col += ShootingStars(viewDir, _SkyTime, _ShootingStarColor.rgb, _ShootingStarRate) * (1.0 - clouds.a);

                col *= _Exposure;
                return half4(col, 1.0);
            }
            ENDHLSL
        }
    }

    Fallback Off
}