using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;
using TMPro;
using UnityEngine.EventSystems;
using BaseGames.Core;
using BaseGames.Core.Events;
using BaseGames.Equipment;
using BaseGames.Localization;

namespace BaseGames.UI
{
    /// <summary>
    /// 护符装备面板。
    ///
    /// 布局：
    ///   顶部   — 标题 + 凹槽容量进度条（已用/总数）
    ///   左侧   — 已装备护符区域（动态格子列表）
    ///   右侧   — 已收集护符目录（可滚动，点击即装备/卸下）
    ///
    /// 数据来源：ServiceLocator 获取 EquipmentManager，读取 Collected / Equipped 列表。
    /// 反应式更新：订阅 _onEquipmentChanged VoidEventChannelSO，变更时重建两侧列表。
    ///
    /// Inspector 必填：
    ///   _notchText              — "X / Y 格子" 文本
    ///   _equippedContainer      — 已装备列表父节点
    ///   _catalogContainer       — 收藏目录列表父节点
    ///   _charmCardTemplate      — 护符卡片预制（kept inactive）
    ///   _btnClose               — 关闭按钮
    ///   _onEquipmentChanged     — EquipmentManager 广播的装备变更事件频道
    /// </summary>
    public class CharmEquipPanel : MonoBehaviour, IFocusable
    {
        // ── Inspector 字段 ────────────────────────────────────────────────────

        [Header("UI 根节点")]
        [SerializeField] private TMP_Text  _notchText;
        [SerializeField] private Image     _notchBarFill;
        [SerializeField] private Transform _equippedContainer;
        [SerializeField] private Transform _catalogContainer;
        [SerializeField] private GameObject _charmCardTemplate;   // kept inactive
        [SerializeField] private Button     _btnClose;

        [Header("Event Channels")]
        [SerializeField] private VoidEventChannelSO _onEquipmentChanged;

        // ── 私有状态 ──────────────────────────────────────────────────────────

        private IEquipmentService         _manager;
        private readonly List<GameObject>  _equippedCards = new();
        private readonly List<GameObject>  _catalogCards  = new();
        private readonly Queue<GameObject> _cardPool      = new();   // O(1) 取用归还
        private readonly CompositeDisposable _subs        = new();

        // ── 生命周期 ──────────────────────────────────────────────────────────

        private void OnEnable()
        {
            _manager = ServiceLocator.GetOrDefault<IEquipmentService>();

            if (_btnClose != null)
            {
                _btnClose.onClick.RemoveAllListeners();
                _btnClose.onClick.AddListener(OnCloseBtnClicked);
            }

            _onEquipmentChanged?.Subscribe(Rebuild).AddTo(_subs);
            Rebuild();

            // 手柄导航：面板打开时将焦点置于关闭按钮
            EventSystem.current?.SetSelectedGameObject(_btnClose?.gameObject);
        }

        private void OnDisable()
        {
            _subs.Clear();
            RecycleCards(_equippedCards);
            RecycleCards(_catalogCards);
        }

        // ── 重建 UI ───────────────────────────────────────────────────────────

        private void Rebuild()
        {
            if (_manager == null) return;

            RefreshNotchBar();
            RebuildEquippedList();
            RebuildCatalogList();
        }

        private void RefreshNotchBar()
        {
            int used  = _manager.UsedNotches;
            int total = _manager.TotalNotches;

            if (_notchText != null)
                _notchText.text = $"{used} / {total}";

            if (_notchBarFill != null)
                _notchBarFill.fillAmount = total > 0 ? (float)used / total : 0f;
        }

        private void RebuildEquippedList()
        {
            RecycleCards(_equippedCards);
            if (_equippedContainer == null) return;

            foreach (var charm in _manager.Equipped)
            {
                var card = SpawnCard(_equippedContainer, charm, isEquipped: true);
                if (card != null) _equippedCards.Add(card);
            }
        }

        private void RebuildCatalogList()
        {
            RecycleCards(_catalogCards);
            if (_catalogContainer == null) return;

            foreach (var charm in _manager.Collected)
            {
                bool isEquipped = _manager.Equipped.Contains(charm);
                var card = SpawnCard(_catalogContainer, charm, isEquipped);
                if (card != null) _catalogCards.Add(card);
            }
        }

        // ── 卡片生成 ──────────────────────────────────────────────────────────

        private GameObject SpawnCard(Transform parent, CharmSO charm, bool isEquipped)
        {
            if (_charmCardTemplate == null || parent == null) return null;

            if (!TryDequeueCard(out GameObject go))
                go = Instantiate(_charmCardTemplate);

            go.transform.SetParent(parent, worldPositionStays: false);
            go.SetActive(true);

            // 优先使用预绑定视图组件（推荐）；若 Prefab 未挂载则回落到反射查找以保证向后兼容。
            var view = go.GetComponent<CharmCardView>();
            if (view != null)
            {
                view.Bind(charm, isEquipped, OnEquipClicked, OnUnequipClicked);
            }
            else
            {
                FallbackBindByReflection(go, charm, isEquipped);
            }

            return go;
        }

        private void OnEquipClicked(CharmSO charm)
        {
            string err = _manager?.TryEquipCharm(charm);
            if (err != null) Debug.LogWarning($"[CharmEquipPanel] 装备失败: {err}");
        }

        private void OnUnequipClicked(CharmSO charm) => _manager?.UnequipCharm(charm);

        /// <summary>
        /// 兼容旧 Prefab（未挂载 <see cref="CharmCardView"/>）的反射绑定。
        /// 仅作为过渡方案；首次开发完成后建议在 Editor 中强制要求新组件。
        /// </summary>
        private void FallbackBindByReflection(GameObject go, CharmSO charm, bool isEquipped)
        {
            var images = go.GetComponentsInChildren<Image>(includeInactive: true);
            if (images.Length > 0 && charm.icon != null)
                images[0].sprite = charm.icon;

            var texts = go.GetComponentsInChildren<TMP_Text>(includeInactive: true);
            if (texts.Length > 0)
            {
                string name = LocalizationManager.Get(charm.displayNameKey, LocalizationTable.Items);
                texts[0].text = string.IsNullOrEmpty(name) || name == charm.displayNameKey
                    ? charm.charmId : name;
            }
            if (texts.Length > 1) texts[1].text = charm.notchCost.ToString();
            if (texts.Length > 2)
            {
                string desc = LocalizationManager.Get(charm.descriptionKey, LocalizationTable.Items);
                texts[2].text = string.IsNullOrEmpty(desc) || desc == charm.descriptionKey
                    ? string.Empty : desc;
            }

            var btn = go.GetComponentInChildren<Button>(includeInactive: true);
            if (btn != null)
            {
                btn.onClick.RemoveAllListeners();
                CharmSO captured = charm;
                if (!isEquipped)
                    btn.onClick.AddListener(() => OnEquipClicked(captured));
                else
                    btn.onClick.AddListener(() => OnUnequipClicked(captured));
                if (texts.Length > 3)
                    texts[3].text = isEquipped ? "✓" : string.Empty;
            }
        }

        // ── 回收 ─────────────────────────────────────────────────────────────

        /// <summary>取队列头第一个非空实例；队列为空时返回 false。</summary>
        private bool TryDequeueCard(out GameObject go)
        {
            while (_cardPool.Count > 0)
            {
                go = _cardPool.Dequeue();
                if (go != null) return true;
            }
            go = null;
            return false;
        }

        private void RecycleCards(List<GameObject> cards)
        {
            foreach (var card in cards)
            {
                if (card == null) continue;
                card.SetActive(false);
                _cardPool.Enqueue(card);
            }
            cards.Clear();
        }

        private void OnCloseBtnClicked()
        {
            var uiMgr = ServiceLocator.GetOrDefault<IUIManager>();
            if (uiMgr != null) uiMgr.CloseTopPanel();
            else gameObject.SetActive(false);
        }

        // ── IFocusable ────────────────────────────────────────────────────────

        /// <summary>面板恢复为栈顶时将焦点移回关闭按鈕。</summary>
        public void OnFocusRestored()
            => EventSystem.current?.SetSelectedGameObject(_btnClose?.gameObject);
    }
}