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

namespace BaseGames.World.Map
{
    /// <summary>
    /// 进入新区域时在屏幕中央短暂渐显区域名称（架构 15_MapShopModule §1.6）。
    /// 挂在 HUD 根节点下，订阅 EVT_RegionChanged，执行淡入—保持—淡出动画序列。
    /// 可通过 _regionNames 配置原始 RegionId 到本地化显示名的映射；未配置时直接显示 RegionId。
    /// </summary>
    [RequireComponent(typeof(CanvasGroup))]
    public class RegionNameDisplay : MonoBehaviour
    {
        [SerializeField] private TMP_Text          _regionText;

        [Header("动画时长（秒）")]
        [SerializeField] [Range(0.1f, 2f)] private float _fadeDuration = 0.4f;
        [SerializeField] [Range(0.5f, 5f)] private float _holdDuration = 2.0f;

        [Header("区域名映射（留空则直接显示 RegionId）")]
        [SerializeField] private RegionNameEntry[] _regionNames;

        [Header("Event Channels")]
        [SerializeField] private StringEventChannelSO _onRegionChanged;

        private CanvasGroup _cg;
        private Coroutine   _showCoroutine;
        private readonly CompositeDisposable _subs = new();

        private void Awake()
        {
            _cg       = GetComponent<CanvasGroup>();
            _cg.alpha = 0f;
            gameObject.SetActive(false);
        }

        private void OnEnable()
        {
            _onRegionChanged?.Subscribe(OnRegionChanged).AddTo(_subs);
        }

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

        // ── 事件响应 ──────────────────────────────────────────────────────────

        private void OnRegionChanged(string regionId)
        {
            if (string.IsNullOrEmpty(regionId)) return;
            if (_regionText != null)
                _regionText.text = ResolveDisplayName(regionId);

            if (_showCoroutine != null) StopCoroutine(_showCoroutine);
            _showCoroutine = StartCoroutine(ShowSequence());
        }

        // ── 动画序列 ──────────────────────────────────────────────────────────

        private IEnumerator ShowSequence()
        {
            gameObject.SetActive(true);
            yield return StartCoroutine(FadeTo(1f));
            yield return new WaitForSecondsRealtime(_holdDuration);
            yield return StartCoroutine(FadeTo(0f));
            gameObject.SetActive(false);
        }

        private IEnumerator FadeTo(float target)
        {
            float start   = _cg.alpha;
            float elapsed = 0f;
            while (elapsed < _fadeDuration)
            {
                _cg.alpha = Mathf.Lerp(start, target, elapsed / _fadeDuration);
                elapsed  += Time.unscaledDeltaTime;
                yield return null;
            }
            _cg.alpha = target;
        }

        // ── 辅助方法 ──────────────────────────────────────────────────────────

        private string ResolveDisplayName(string regionId)
        {
            if (_regionNames != null)
                foreach (var e in _regionNames)
                    if (e.RegionId == regionId) return e.DisplayName;
            return regionId;
        }
    }

    [Serializable]
    public struct RegionNameEntry
    {
        public string RegionId;
        public string DisplayName;
    }
}