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

namespace BaseGames.VFX
{
    /// <summary>
    /// 后处理 Volume 分区管理器，挂在 Persistent 场景 [PostProcess] GameObject 上。
    /// 通过 Coroutine 平滑 blend Weight，监听游戏状态/Boss/死亡/胜利事件。
    /// 注意：水下后处理由 UnderwaterPostProcessingController（World.Liquid）独立负责，此组件不处理。
    /// </summary>
    public class PostProcessManager : MonoBehaviour
    {
        [Header("Volume 引用（Persistent 场景内）")]
        [SerializeField] private Volume _bossArenaVolume;
        [SerializeField] private Volume _deathVolume;
        [SerializeField] private Volume _victoryVolume;

        [Header("事件频道")]
        [SerializeField] private VoidEventChannelSO _onBossFightStarted;
        [SerializeField] private VoidEventChannelSO _onBossFightEnded;
        [SerializeField] private VoidEventChannelSO _onPlayerDied;
        [SerializeField] private VoidEventChannelSO _onPlayerRespawned;
        [SerializeField] private VoidEventChannelSO _onBossDefeated;

        [SerializeField] private float _blendDuration = 0.4f;

        private Volume[] _managedVolumes;
        private Coroutine _blendCoroutine;
        /// <summary>调用 BlendCoroutine / ResetAllCoroutine 时复用的起始权重缓存，避免每次分配新数组。</summary>
        private float[] _startWeights;
        private readonly CompositeDisposable _subs = new();

        private void Awake()
        {
            _managedVolumes = new[] { _bossArenaVolume, _deathVolume, _victoryVolume };
            _startWeights   = new float[_managedVolumes.Length];
        }

        private void OnEnable()
        {
            _onBossFightStarted?.Subscribe(HandleBossFightStarted).AddTo(_subs);
            _onBossFightEnded?.Subscribe(HandleBossFightEnded).AddTo(_subs);
            _onPlayerDied?.Subscribe(HandlePlayerDied).AddTo(_subs);
            _onPlayerRespawned?.Subscribe(HandlePlayerRespawned).AddTo(_subs);
            _onBossDefeated?.Subscribe(HandleBossDefeated).AddTo(_subs);
        }

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

        // ── 事件处理 ────────────────────────────────────────────────────────────
        private void HandleBossFightStarted() => BlendTo(_bossArenaVolume);
        private void HandleBossFightEnded()   => ResetAll();
        private void HandlePlayerDied()       => BlendTo(_deathVolume);
        private void HandlePlayerRespawned()  => ResetAll();
        private void HandleBossDefeated()     => BlendTo(_victoryVolume);

        // ── 混合逻辑 ─────────────────────────────────────────────────────────────

        /// <summary>将目标 Volume 权重渐变为 1，其他管理中的 Volume 渐变为 0。</summary>
        private void BlendTo(Volume target)
        {
            if (_blendCoroutine != null)
                StopCoroutine(_blendCoroutine);
            _blendCoroutine = StartCoroutine(BlendCoroutine(target, 1f));
        }

        /// <summary>所有受管 Volume 权重渐变回 0（恢复默认后处理）。</summary>
        private void ResetAll()
        {
            if (_blendCoroutine != null)
                StopCoroutine(_blendCoroutine);
            _blendCoroutine = StartCoroutine(ResetAllCoroutine());
        }

        private IEnumerator BlendCoroutine(Volume target, float targetWeight)
        {
            float elapsed   = 0f;
            for (int i = 0; i < _managedVolumes.Length; i++)
                _startWeights[i] = _managedVolumes[i] != null ? _managedVolumes[i].weight : 0f;

            while (elapsed < _blendDuration)
            {
                elapsed += Time.unscaledDeltaTime;
                float t  = Mathf.Clamp01(elapsed / _blendDuration);

                for (int i = 0; i < _managedVolumes.Length; i++)
                {
                    if (_managedVolumes[i] == null) continue;
                    float dest = _managedVolumes[i] == target ? targetWeight : 0f;
                    _managedVolumes[i].weight = Mathf.Lerp(_startWeights[i], dest, t);
                }

                yield return null;
            }

            // 确保精确收敛
            for (int i = 0; i < _managedVolumes.Length; i++)
            {
                if (_managedVolumes[i] == null) continue;
                _managedVolumes[i].weight = _managedVolumes[i] == target ? targetWeight : 0f;
            }
            _blendCoroutine = null;
        }

        private IEnumerator ResetAllCoroutine()
        {
            float elapsed    = 0f;
            for (int i = 0; i < _managedVolumes.Length; i++)
                _startWeights[i] = _managedVolumes[i] != null ? _managedVolumes[i].weight : 0f;

            while (elapsed < _blendDuration)
            {
                elapsed += Time.unscaledDeltaTime;
                float t  = Mathf.Clamp01(elapsed / _blendDuration);
                for (int i = 0; i < _managedVolumes.Length; i++)
                {
                    if (_managedVolumes[i] == null) continue;
                    _managedVolumes[i].weight = Mathf.Lerp(_startWeights[i], 0f, t);
                }
                yield return null;
            }
            for (int i = 0; i < _managedVolumes.Length; i++)
            {
                if (_managedVolumes[i] != null)
                    _managedVolumes[i].weight = 0f;
            }
            _blendCoroutine = null;
        }
    }
}