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

namespace BaseGames.UI
{
    /// <summary>屏幕阅读器优先级（与 WCAG / ARIA live-region 等级对齐）。</summary>
    public enum ScreenReaderPriority
    {
        /// <summary>Polite —— 当前播报结束后再播报，不打断玩家。</summary>
        Polite = 0,
        /// <summary>Assertive —— 立即打断当前播报（如战斗死亡、关键提示）。</summary>
        Assertive = 1
    }

    /// <summary>
    /// 屏幕阅读器接口（无障碍）。默认无实现；接入第三方 TTS / 平台 API（iOS VoiceOver、
    /// Android TalkBack、Steam Overlay TTS）时实现本接口并通过 ServiceLocator 注册。
    /// 设计为 string-only 接口而非富文本，避免不同 TTS 引擎对标签解析不一致。
    /// </summary>
    public interface IScreenReader
    {
        void Speak(string text, ScreenReaderPriority priority = ScreenReaderPriority.Polite);
        void StopAll();
    }

    /// <summary>
    /// 字幕管理器（架构 10_UIModule §11 无障碍补完）。
    ///
    /// 职责：与对话气泡（DialogueUI）解耦，专门承担"叙述性字幕 / 关键提示文本 / 战斗播报"。
    /// 订阅 <see cref="StringEventChannelSO"/>（推荐项目内新建 EVT_SubtitleShow）显示底部居中字幕；
    /// 若 <see cref="ServiceLocator"/> 中存在 <see cref="IScreenReader"/> 实现则同步触发 TTS。
    ///
    /// 队列策略：Polite 串行（FIFO）；Assertive 立即清空队列并显示。
    /// </summary>
    public class SubtitleManager : MonoBehaviour
    {
        [Header("UI")]
        [SerializeField] private GameObject _root;
        [SerializeField] private TMP_Text   _label;
        [SerializeField] private CanvasGroup _canvasGroup;

        [Header("时长")]
        [Tooltip("每行字幕显示时间（秒）；可被 Show(text, durationOverride) 覆盖。")]
        [SerializeField] private float _defaultDuration = 3f;
        [SerializeField] private float _fadeDuration    = 0.2f;

        [Header("事件频道（可选）")]
        [SerializeField] private StringEventChannelSO _onSubtitleShow;

        private readonly Queue<(string text, float duration, ScreenReaderPriority pri)> _queue = new();
        private Coroutine _playCo;
        private readonly CompositeDisposable _subs = new();

        private void OnEnable()
        {
            if (_root != null) _root.SetActive(false);
            if (_canvasGroup != null) _canvasGroup.alpha = 0f;
            _onSubtitleShow?.Subscribe(t => Show(t, _defaultDuration, ScreenReaderPriority.Polite)).AddTo(_subs);
        }

        private void OnDisable() => _subs.Clear();

        /// <summary>显示一行字幕；自动按优先级排队。</summary>
        public void Show(string text, float duration = -1f,
                         ScreenReaderPriority priority = ScreenReaderPriority.Polite)
        {
            if (string.IsNullOrEmpty(text)) return;
            float d = duration > 0f ? duration : _defaultDuration;

            if (priority == ScreenReaderPriority.Assertive)
            {
                _queue.Clear();
                if (_playCo != null) StopCoroutine(_playCo);
                _playCo = null;
            }
            _queue.Enqueue((text, d, priority));

            // 同步触发 TTS
            var reader = ServiceLocator.GetOrDefault<IScreenReader>(null);
            reader?.Speak(text, priority);

            if (_playCo == null) _playCo = StartCoroutine(PlayLoop());
        }

        private IEnumerator PlayLoop()
        {
            while (_queue.Count > 0)
            {
                var (text, d, _) = _queue.Dequeue();
                yield return ShowOne(text, d);
            }
            _playCo = null;
        }

        private IEnumerator ShowOne(string text, float duration)
        {
            if (_label != null) _label.text = text;
            if (_root  != null) _root.SetActive(true);

            yield return Fade(0f, 1f, _fadeDuration);
            yield return new WaitForSecondsRealtime(Mathf.Max(0f, duration - _fadeDuration * 2f));
            yield return Fade(1f, 0f, _fadeDuration);

            if (_root != null) _root.SetActive(false);
        }

        private IEnumerator Fade(float from, float to, float dur)
        {
            if (_canvasGroup == null || dur <= 0f)
            {
                if (_canvasGroup != null) _canvasGroup.alpha = to;
                yield break;
            }
            float t = 0f;
            while (t < dur)
            {
                t += Time.unscaledDeltaTime;
                _canvasGroup.alpha = Mathf.Lerp(from, to, t / dur);
                yield return null;
            }
            _canvasGroup.alpha = to;
        }
    }
}