using System;
using System.Collections;
using UnityEngine;
using UnityEngine.Rendering.Universal;
using BaseGames.Core.Events;

namespace BaseGames.VFX
{
    /// <summary>
    /// 区域进出时平滑切换 Global Light 2D 颜色和强度。
    /// 挂在 Persistent 场景 [Lighting] GameObject 上，监听 OnRegionEntered 事件频道。
    /// </summary>
    public class RegionLightController : MonoBehaviour
    {
        [SerializeField] private Light2D                _globalLight;
        [SerializeField] private RegionLightCatalogSO   _catalog;
        [SerializeField] private StringEventChannelSO   _onRegionEntered;
        [SerializeField] private float                  _transitionDuration = 1.5f;

        private Coroutine _colorCoroutine;
        private Coroutine _intensityCoroutine;
        private readonly CompositeDisposable _subs = new();

        private void Awake()
        {
            Debug.Assert(_catalog      != null, "[RegionLightController] _catalog 未赋值，请在 Inspector 中指定 RegionLightCatalogSO。", this);
            Debug.Assert(_globalLight  != null, "[RegionLightController] _globalLight 未赋值，请在 Inspector 中绑定 Light2D。",            this);
        }

        private void OnEnable()
        {
            _onRegionEntered?.Subscribe(OnRegionEntered).AddTo(_subs);
        }

        private void OnDisable()
        {
            _subs.Clear();
        }

        private void OnRegionEntered(string regionId)
        {
            if (!_catalog.TryGet(regionId, out var config)) return;

            if (_colorCoroutine     != null) StopCoroutine(_colorCoroutine);
            if (_intensityCoroutine != null) StopCoroutine(_intensityCoroutine);

            _colorCoroutine     = StartCoroutine(TweenColor(_globalLight.color, config.Color, _transitionDuration));
            _intensityCoroutine = StartCoroutine(TweenIntensity(_globalLight.intensity, config.Intensity, _transitionDuration));
        }

        // ── Coroutine helpers ────────────────────────────────────────────────────
        private IEnumerator TweenColor(Color from, Color to, float duration)
        {
            float elapsed = 0f;
            while (elapsed < duration)
            {
                elapsed          += Time.deltaTime;
                _globalLight.color = Color.Lerp(from, to, Mathf.Clamp01(elapsed / duration));
                yield return null;
            }
            _globalLight.color  = to;
            _colorCoroutine     = null;
        }

        private IEnumerator TweenIntensity(float from, float to, float duration)
        {
            float elapsed = 0f;
            while (elapsed < duration)
            {
                elapsed               += Time.deltaTime;
                _globalLight.intensity = Mathf.Lerp(from, to, Mathf.Clamp01(elapsed / duration));
                yield return null;
            }
            _globalLight.intensity  = to;
            _intensityCoroutine     = null;
        }
    }

    // ────────────────────────────────────────────────────────────────────────────
    // RegionLightCatalogSO
    // ────────────────────────────────────────────────────────────────────────────

    /// <summary>
    /// 区域 ID → Global Light 2D 颜色 + 强度映射表。
    /// 资产路径：Assets/ScriptableObjects/VFX/VFX_RegionLightCatalog.asset
    /// </summary>
    [CreateAssetMenu(menuName = "VFX/RegionLightCatalog")]
    public class RegionLightCatalogSO : ScriptableObject
    {
        [Serializable]
        public struct RegionLightConfig
        {
            public string regionId;
            public Color  Color;
            [Range(0f, 1f)] public float Intensity;
        }

        [SerializeField] private RegionLightConfig[] _entries;

        /// <summary>根据 regionId 查找对应的灯光配置。</summary>
        public bool TryGet(string regionId, out RegionLightConfig cfg)
        {
            if (_entries != null)
            {
                foreach (var e in _entries)
                {
                    if (e.regionId == regionId) { cfg = e; return true; }
                }
            }
            cfg = default;
            return false;
        }
    }
}