using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Audio;
using BaseGames.Core;
using BaseGames.Core.Events;

namespace BaseGames.Audio
{
    /// <summary>
    /// 音频管理器。
    /// 职责：BGM 双 Source 交叉淡入淡出、SFX 多源轮转池、AudioMixer 快照切换、音量控制。
    /// 挂在 Persistent 场景 [AudioManager] GameObject 上。
    /// </summary>
    [DefaultExecutionOrder(-500)]
    public class AudioManager : MonoBehaviour, IAudioService
    {
        [Header("AudioMixer")]
        [SerializeField] private AudioMixer _mixer;

        [Header("BGM Sources（双 Source 交叉淡入淡出）")]
        [SerializeField] private AudioSource _bgmSourceA;
        [SerializeField] private AudioSource _bgmSourceB;

        [Header("SFX Pool（建议 6 个，均路由到 SFX MixerGroup）")]
        [Tooltip("轮转池大小：同帧触发数超过此值时最旧的音效会被打断。建议 6~8 个。")]
        [SerializeField] private AudioSource[] _sfxSources;

        [Header("Audio Config（BGM 映射）")]
        [SerializeField] private AudioConfigSO _audioConfig;

        [Header("SFX 注册表（key → AudioEventSO）")]
        [SerializeField] private AudioEventEntry[] _sfxRegistry;

        [System.Serializable]
        public struct AudioEventEntry
        {
            public string      Key;
            public AudioEventSO Event;
        }

        [Header("Event Channels - Subscribe")]
        [SerializeField] private VoidEventChannelSO _onPlayerDied;

        private AudioSource _activeBGMSource;
        private AudioSource _inactiveBGMSource;
        private Coroutine   _crossfadeCoroutine;
        private int         _sfxRoundRobin;
        private Dictionary<string, AudioEventSO> _sfxLookup;
        private readonly CompositeDisposable _subs = new();

        private void Awake()
        {
            if (ServiceLocator.GetOrDefault<IAudioService>() != null) { Destroy(gameObject); return; }

            Debug.Assert(_audioConfig != null, "[AudioManager] _audioConfig 未赋值，请在 Inspector 中指定 AudioConfigSO。", this);

            _activeBGMSource   = _bgmSourceA;
            _inactiveBGMSource = _bgmSourceB;

            ServiceLocator.Register<IAudioService>(this);
            BuildSFXLookup();
            Initialize();
        }

        private void OnEnable()
        {
            _onPlayerDied?.Subscribe(HandlePlayerDied).AddTo(_subs);
        }

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

        private void OnDestroy()
        {
            ServiceLocator.Unregister<IAudioService>(this);
        }

        // ── IAudioService string-key API ────────────────────────────────────────────
        /// <summary>按 Zone/Boss key 查 AudioConfigSO 播放 BGM。</summary>
        public void PlayBGM(string key)
        {
            var clip = _audioConfig.GetZoneBGM(key) ?? _audioConfig.GetBossBGM(key);
            if (clip == null)
            {
                Debug.LogWarning($"[AudioManager] BGM key '{key}' 在 AudioConfigSO 中未找到。");
                return;
            }
            PlayBGM(clip);
        }

        /// <summary>按 key 查 SFX 注册表播放 AudioEventSO。</summary>
        public void PlaySFX(string key)
        {
            if (_sfxLookup != null && _sfxLookup.TryGetValue(key, out var evt))
            {
                evt?.PlayOneShot(NextSFXSource());
                return;
            }
            Debug.LogWarning($"[AudioManager] SFX key '{key}' 未在注册表中找到。");
        }

        // ── 音量控制 ─────────────────────────────────────────────────────────────
        /// <summary>
        /// 将指定 Exposed Parameter 设置为 0-1 线性值（内部转换为 dB）。
        /// 唯一音量写入入口（同时满足 IAudioService.SetVolume 接口）。
        /// </summary>
        public void SetVolume(string exposedParam, float linear)
            => _mixer.SetFloat(exposedParam, LinearToDecibel(linear));

        /// <summary>读取 SettingsManager 已加载的设置数据并应用四路音量到 AudioMixer。</summary>
        public void Initialize()
        {
            var settings = ServiceLocator.GetOrDefault<ISettingsService>();
            GlobalSettingsData data = settings?.Current ?? new GlobalSettingsData();
            SetVolume(AudioMixerKeys.Master,  data.MasterVolume);
            SetVolume(AudioMixerKeys.BGM,     data.BGMVolume);
            SetVolume(AudioMixerKeys.SFX,     data.SFXVolume);
            SetVolume(AudioMixerKeys.Ambient, data.AmbientVolume);
        }

        // ── BGM ──────────────────────────────────────────────────────────────────
        /// <summary>播放 BGM，使用双 AudioSource 交叉淡入淡出。</summary>
        public void PlayBGM(AudioClip clip, float fadeOutDur = 1f, float fadeInDur = 1f)
        {
            if (clip == null) return;
            if (_crossfadeCoroutine != null) StopCoroutine(_crossfadeCoroutine);
            _crossfadeCoroutine = StartCoroutine(CrossfadeCoroutine(clip, fadeOutDur, fadeInDur));
        }

        /// <summary>停止 BGM（带淡出）。</summary>
        public void StopBGM(float fadeDuration = 1f)
        {
            if (_crossfadeCoroutine != null) StopCoroutine(_crossfadeCoroutine);
            _crossfadeCoroutine = StartCoroutine(FadeOutCoroutine(_activeBGMSource, fadeDuration));
        }

        // ── SFX ──────────────────────────────────────────────────────────────────
        /// <summary>
        /// 一次性播放 SFX，使用轮转多源池避免高密度战斗时音效相互戳断。
        /// </summary>
        public void PlaySFX(AudioClip clip, float volumeScale = 1f)
        {
            if (clip == null) return;
            var src = NextSFXSource();
            if (src == null) return;
            src.volume = volumeScale;
            src.PlayOneShot(clip);
        }

        /// <summary>2D 游戏中位置无衰减，统一委托多源池播放。</summary>
        public void PlaySFXAtPosition(AudioClip clip, Vector2 pos, float volumeScale = 1f)
        {
            if (clip == null) return;
            AudioSource.PlayClipAtPoint(clip, pos, volumeScale);
        }

        // ── 快照切换 ─────────────────────────────────────────────────────────────
        /// <summary>切换 AudioMixer 快照（如 Default / Paused / Dead / BossFight）。</summary>
        public void TransitionToSnapshot(string snapshotName, float transitionTime = 0.5f)
        {
            var snapshot = _mixer.FindSnapshot(snapshotName);
            if (snapshot != null)
                snapshot.TransitionTo(transitionTime);
            else
                Debug.LogWarning($"[AudioManager] Snapshot '{snapshotName}' not found in mixer.");
        }

        // ── 内部实现 ─────────────────────────────────────────────────────────────
        private void HandlePlayerDied()
        {
            TransitionToSnapshot("Dead", 1.5f);
        }

        private void BuildSFXLookup()
        {
            _sfxLookup = new Dictionary<string, AudioEventSO>(_sfxRegistry?.Length ?? 0);
            if (_sfxRegistry == null) return;
            foreach (var entry in _sfxRegistry)
                if (!string.IsNullOrEmpty(entry.Key) && entry.Event != null)
                    _sfxLookup[entry.Key] = entry.Event;
        }

        private AudioSource NextSFXSource()
        {
            if (_sfxSources == null || _sfxSources.Length == 0)
            {
                Debug.LogError("[AudioManager] SFX Source 池为空，请在 Inspector 中为 _sfxSources 赋值。");
                return null;
            }
            return _sfxSources[_sfxRoundRobin++ % _sfxSources.Length];
        }

        private IEnumerator CrossfadeCoroutine(AudioClip newClip, float fadeOutDur, float fadeInDur)
        {
            // 淡出当前活跃 Source
            float startVolume = _activeBGMSource.volume;
            float elapsed = 0f;
            while (elapsed < fadeOutDur)
            {
                elapsed += Time.unscaledDeltaTime;
                _activeBGMSource.volume = Mathf.Lerp(startVolume, 0f, elapsed / fadeOutDur);
                yield return null;
            }
            _activeBGMSource.Stop();
            _activeBGMSource.volume = 0f;

            // 切换到非活跃 Source 播放新曲目
            var temp = _activeBGMSource;
            _activeBGMSource   = _inactiveBGMSource;
            _inactiveBGMSource = temp;

            _activeBGMSource.clip   = newClip;
            _activeBGMSource.volume = 0f;
            _activeBGMSource.Play();

            // 淡入新 Source
            elapsed = 0f;
            while (elapsed < fadeInDur)
            {
                elapsed += Time.unscaledDeltaTime;
                _activeBGMSource.volume = Mathf.Lerp(0f, 1f, elapsed / fadeInDur);
                yield return null;
            }
            _activeBGMSource.volume = 1f;
            _crossfadeCoroutine = null;
        }

        private IEnumerator FadeOutCoroutine(AudioSource source, float duration)
        {
            float startVolume = source.volume;
            float elapsed = 0f;
            while (elapsed < duration)
            {
                elapsed += Time.unscaledDeltaTime;
                source.volume = Mathf.Lerp(startVolume, 0f, elapsed / duration);
                yield return null;
            }
            source.Stop();
            source.volume = 0f;
            _crossfadeCoroutine = null;
        }

        private static float LinearToDecibel(float linear)
            => linear > 0.0001f ? 20f * Mathf.Log10(linear) : -80f;
    }
}