using System.Collections;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

/// <summary>
/// Builds the environment reflection from the current Skybox in memory (renders the sky into a cubemap
/// assigned as the Custom reflection), so smooth/metallic materials reflect the sky WITHOUT a baked
/// LightingData.asset. Runs in Edit and Play mode ([ExecuteAlways]); drop it on one object per scene —
/// also works for runtime-loaded / procedural scenes.
///
/// Why a rendered cubemap and not <see cref="DynamicGI.UpdateEnvironment"/>: in this project
/// UpdateEnvironment does NOT produce a valid skybox reflection probe (a mirror stays black), so
/// <see cref="RenderSettings.reflectionIntensity"/> had nothing to scale. Rendering the sky into a
/// Custom reflection cubemap gives a real reflection that intensity can actually drive.
///
/// The skybox AMBIENT probe still comes from UpdateEnvironment — but it only convolves a non-zero probe
/// once the sky has actually been rendered this session. Straight after a domain reload / scene load /
/// play-start the sky hasn't rendered yet, so the probe is ZERO and the Environment intensity multiplier
/// has nothing to scale ("doesn't take effect" until a manual re-enable). Fix: one synchronous
/// full-screen sky render "warms" the sky right before UpdateEnvironment — deterministic, no waiting on
/// renders. (RenderToCubemap does NOT warm the ambient path; a normal Camera.Render does.)
/// </summary>
[ExecuteAlways]
[DisallowMultipleComponent]
public class SkyboxEnvironmentUpdater : MonoBehaviour
{
    [Range(0f, 4f)]
    public float environmentLightingIntensity = 1;
    
    [Header("Reflections")]

    [Tooltip("Resolution of the generated sky reflection cubemap (power of two).")]
    public int reflectionResolution = 128;

    [Tooltip("How strongly the sky reflection tints reflective/metallic surfaces. 1 = neutral; the Lighting window slider caps at 1, but higher values (via this field) over-drive the reflection for a glossier metal look. Only applied while Force Skybox Reflections is on.")]
    [Range(0f, 4f)]
    public float reflectionIntensity = 1f;
    
    [Tooltip("Optional: render THIS sky material into the reflection cubemap instead of the scene's global Skybox. Leave empty to use RenderSettings.skybox. Only affects the reflection — the visible scene skybox is unchanged.")]
    public Material reflectionSkyOverride;

    [System.NonSerialized] Cubemap _reflectionCube;

    void OnDisable()
    {
#if UNITY_EDITOR
        UnityEditor.EditorApplication.delayCall -= Apply;
#endif
        if (!_reflectionCube)
            return;

        if (RenderSettings.customReflectionTexture == _reflectionCube)
            RenderSettings.customReflectionTexture = null;

        DestroyImmediate(_reflectionCube);

        _reflectionCube = null;
    }

    void OnValidate()
    {
        if (this && isActiveAndEnabled)
            OnEnable();
        else
            OnDisable();
    }

    void OnEnable()
    {
        if (!RenderSettings.skybox && !reflectionSkyOverride)
            return;

#if UNITY_EDITOR
        if (!Application.isPlaying)
        {
            UnityEditor.EditorApplication.delayCall -= Apply;
            UnityEditor.EditorApplication.delayCall += Apply;
            return;
        }
#endif
        StartCoroutine(ApplyNextFrame());
    }

    IEnumerator ApplyNextFrame()
    {
        yield return null;
        Apply();
    }

    void Apply()
    {
        if (!this || !isActiveAndEnabled)
            return;

        if (!RenderSettings.skybox && !reflectionSkyOverride)
            return;

        RenderSettings.ambientIntensity = environmentLightingIntensity;

        var camGo = new GameObject("__SkyboxEnvCam") { hideFlags = HideFlags.HideAndDontSave };
        try
        {
            var cam = camGo.AddComponent<Camera>();
            cam.enabled = false;
            cam.cullingMask = 0;
            cam.clearFlags = CameraClearFlags.Skybox;
            cam.cameraType = CameraType.Reflection;

            var camData = camGo.AddComponent<UniversalAdditionalCameraData>();
            camData.renderPostProcessing = false;
            camData.requiresDepthTexture = false;
            camData.requiresColorTexture = false;
            camData.renderShadows = false;

            if (reflectionSkyOverride)
                camGo.AddComponent<Skybox>().material = reflectionSkyOverride;

            camGo.transform.position = transform.position;

            var rt = RenderTexture.GetTemporary(64, 64, 16);
            cam.targetTexture = rt;
            cam.Render();
            cam.targetTexture = null;
            RenderTexture.ReleaseTemporary(rt);

            EnsureReflectionCubemap();
            cam.RenderToCubemap(_reflectionCube);
        }
        finally
        {
            DestroyImmediate(camGo);
        }

        RenderSettings.defaultReflectionMode = DefaultReflectionMode.Custom;
        RenderSettings.customReflectionTexture = _reflectionCube;
        RenderSettings.reflectionIntensity = reflectionIntensity;

        RenderSettings.ambientMode = AmbientMode.Skybox;
        DynamicGI.UpdateEnvironment();
    }

    void EnsureReflectionCubemap()
    {
        int size = Mathf.Max(16, reflectionResolution);

        if (!_reflectionCube || _reflectionCube.width != size)
        {
            if (_reflectionCube)
            {
                DestroyImmediate(_reflectionCube);
            }

            _reflectionCube = new Cubemap(size, TextureFormat.RGBA32, true)
            {
                name = "SkyboxReflection (generated)"
            };
        }
    }
}