using System.Collections;
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）")]
        [SerializeField] private AudioSource[] _sfxSources;

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

        private AudioSource _activeBGMSource;
        private AudioSource _inactiveBGMSource;
        private Coroutine   _crossfadeCoroutine;
        private int         _sfxRoundRobin;

        // ── 遗留单例（已废弃；新代码请使用 ServiceLocator.Get<IAudioService>()）────────────
        [System.Obsolete("Use ServiceLocator.Get<IAudioService>() instead.")]
        public static AudioManager Instance { get; private set; }

        private void Awake()
        {
#pragma warning disable CS0618
            if (Instance != null) { Destroy(gameObject); return; }
            Instance = this;
#pragma warning restore CS0618

            _activeBGMSource   = _bgmSourceA;
            _inactiveBGMSource = _bgmSourceB;

            // ServiceLocator 注册（覆盖 GameServiceRegistrar 的 NullAudioService 兜底）
            ServiceLocator.Register<IAudioService>(this);
        }

        private void OnEnable()
        {
            if (_onPlayerDied != null)
                _onPlayerDied.OnEventRaised += HandlePlayerDied;
        }

        private void OnDisable()
        {
            if (_onPlayerDied != null)
                _onPlayerDied.OnEventRaised -= HandlePlayerDied;
        }

        // ── IAudioService string-key API（Phase 2 接入 AudioEventSO 后完整实现）─────────────
        /// <summary>
        /// 按 Addressable key 播放 BGM。Phase 2 接入 AudioEventSO 前为占位警告。
        /// </summary>
        public void PlayBGM(string key)
            => Debug.LogWarning($"[AudioManager] PlayBGM(key) 尚未接入 AudioEventSO（Phase 2）。key={key}");

        /// <summary>
        /// 按 Addressable key 播放 SFX。Phase 2 接入 AudioEventSO 前为占位警告。
        /// </summary>
        public void PlaySFX(string key)
            => Debug.LogWarning($"[AudioManager] PlaySFX(key) 尚未接入 AudioEventSO（Phase 2）。key={key}");

        // ── 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 GlobalSettings 并应用所有音量初始值。</summary>
        public void Initialize()
        {
            // TODO: 从 SettingsManager / PlayerPrefs 读取保存的音量值并应用
        }

        // ── 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();
            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)
            => PlaySFX(clip, 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 AudioSource NextSFXSource()
        {
            if (_sfxSources == null || _sfxSources.Length == 0) return _bgmSourceA;
            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;
    }
}