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

namespace BaseGames.UI
{
    /// <summary>
    /// 面板 ID 枚举。新增面板时只需在此添加值并在 Inspector 的 _panels 数组中注册，
    /// 无需修改 UIManager 的其他代码，满足开闭原则。
    /// </summary>
    public enum PanelId
    {
        Pause,
        Settings,
        Map,
        Shop,
        CharmPanel,
        SpellSelect,
    }

    [DefaultExecutionOrder(+50)]
    public class UIManager : MonoBehaviour, IUIManager
    {
        // ── 状态驱动根节点（不进入面板栈，仅根据 GameState 显示/隐藏）────────
        [Header("状态驱动根节点（非面板栈）")]
        [SerializeField] private GameObject _hudRoot;
        [SerializeField] private GameObject _deathScreenRoot;

        // ── 面板栈注册表 ──────────────────────────────────────────────────────
        [Header("面板栈注册表（Inspector 配置，可运行时扩展）")]
        [Tooltip("将 PanelId 与对应的根 GameObject 绑定。" +
                 "新增面板只需在此添加一行，无需修改 UIManager 代码。")]
        [SerializeField] private PanelRegistration[] _panels;

        [Header("Event Channels")]
        [SerializeField] private GameStateEventChannelSO _onGameStateChanged;
        [SerializeField] private VoidEventChannelSO      _onPauseRequested;
        [SerializeField] private VoidEventChannelSO      _onFastTravelOpen;
        [SerializeField] private StringEventChannelSO    _onShopOpen;
        [SerializeField] private VoidEventChannelSO      _onMapOpen;
        [SerializeField] private VoidEventChannelSO      _onCharmPanelOpen;
        [SerializeField] private VoidEventChannelSO      _onSpellSelectOpen;

        // ── 面板栈结构 ────────────────────────────────────────────────────────
        private readonly Stack<GameObject>           _panelStack    = new();
        /// <summary>O(1) 成员判断，与 _panelStack 保持同步，替代 Stack.Contains O(n)。</summary>
        private readonly HashSet<GameObject>         _openPanelSet  = new();
        private readonly Dictionary<PanelId, GameObject> _panelRegistry = new();
        private readonly CompositeDisposable         _subs          = new();

        // ── 序列化辅助结构 ────────────────────────────────────────────────────
        [System.Serializable]
        private struct PanelRegistration
        {
            [Tooltip("面板标识符（与代码中的 PanelId 枚举对应）。")]
            public PanelId    id;
            [Tooltip("该面板的根 GameObject（通常是 Canvas 的直接子节点）。")]
            public GameObject root;
        }

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

        private void Awake()
        {
            if (_panels != null)
                foreach (var p in _panels)
                    if (p.root != null) _panelRegistry[p.id] = p.root;
        }

        private void OnEnable()
        {
            ServiceLocator.Register<IUIManager>(this);
            _onGameStateChanged?.Subscribe(HandleGameStateChanged).AddTo(_subs);
            _onPauseRequested?.Subscribe(TogglePause).AddTo(_subs);
            _onFastTravelOpen?.Subscribe(OpenMap).AddTo(_subs);
            _onShopOpen?.Subscribe(OpenShop).AddTo(_subs);
            _onMapOpen?.Subscribe(OpenMap).AddTo(_subs);
            _onCharmPanelOpen?.Subscribe(OpenCharmPanel).AddTo(_subs);
            _onSpellSelectOpen?.Subscribe(OpenSpellSelect).AddTo(_subs);
        }

        private void OnDisable()
        {
            ServiceLocator.Unregister<IUIManager>(this);
            _subs.Clear();
        }

        // ── 面板注册（运行时动态扩展入口）────────────────────────────────────

        /// <summary>
        /// 运行时注册或覆盖面板绑定（如场景加载后动态添加的面板）。
        /// Inspector 中已配置的面板无需调用此方法。
        /// </summary>
        public void RegisterPanel(PanelId id, GameObject root)
        {
            if (root != null) _panelRegistry[id] = root;
        }

        // ── 状态响应 ──────────────────────────────────────────────────────────

        private void HandleGameStateChanged(GameStateId state)
        {
            bool showHud = state == GameStates.Gameplay || state == GameStates.BossFight;
            if (_hudRoot != null) _hudRoot.SetActive(showHud);

            if (state == GameStates.Dead)
            {
                if (_deathScreenRoot != null) _deathScreenRoot.SetActive(true);
            }
            else
            {
                if (_deathScreenRoot != null) _deathScreenRoot.SetActive(false);

                if (state == GameStates.Cutscene)
                    if (_hudRoot != null) _hudRoot.SetActive(false);
            }
        }

        // ── 面板栈 API ────────────────────────────────────────────────────────

        /// <summary>通过 ID 打开已注册的面板。</summary>
        public void OpenPanel(PanelId id)
        {
            if (_panelRegistry.TryGetValue(id, out var panel))
                OpenPanel(panel);
        }

        /// <summary>打开指定 GameObject 面板并压栈；已在栈中则忽略（O(1) 判断）。</summary>
        public void OpenPanel(GameObject panel)
        {
            if (panel == null) return;
            if (!_openPanelSet.Add(panel)) return;   // HashSet.Add 返回 false = 已存在
            if (_panelStack.Count > 0) _panelStack.Peek().SetActive(false);
            panel.SetActive(true);
            _panelStack.Push(panel);
        }

        /// <summary>关闭栈顶面板并恢复上一层（如有）；上一层若实现 IFocusable 则自动恢复焦点。</summary>
        public void CloseTopPanel()
        {
            if (_panelStack.Count == 0) return;
            var top = _panelStack.Pop();
            _openPanelSet.Remove(top);
            top.SetActive(false);
            if (_panelStack.Count > 0)
            {
                var restored = _panelStack.Peek();
                restored.SetActive(true);
                restored.GetComponent<IFocusable>()?.OnFocusRestored();
            }
        }

        // ── 快捷事件回调 ──────────────────────────────────────────────────────

        private void TogglePause()
        {
            if (_panelRegistry.TryGetValue(PanelId.Pause, out var pausePanel)
                && _panelStack.Count > 0 && _panelStack.Peek() == pausePanel)
                CloseTopPanel();
            else
                OpenPanel(PanelId.Pause);
        }
        private void OpenShop(string _)    => OpenPanel(PanelId.Shop);
        private void OpenMap()             => OpenPanel(PanelId.Map);
        private void OpenCharmPanel()      => OpenPanel(PanelId.CharmPanel);
        private void OpenSpellSelect()     => OpenPanel(PanelId.SpellSelect);

        // ── 编辑器工具 (不入构建) ──────────────────────────────────────────────────

        /// <summary>验证面板注册表是否完整、无重复、无空引用。</summary>
        [ContextMenu("验证面板注册表")]
        private void EditorValidateRegistry()
        {
            if (_panels == null || _panels.Length == 0)
            {
                Debug.LogWarning("[UIManager] 面板注册表为空！", this);
                return;
            }

            var seen = new System.Collections.Generic.HashSet<PanelId>();
            bool ok  = true;
            foreach (var p in _panels)
            {
                if (p.root == null)
                {
                    Debug.LogWarning($"[UIManager] PanelId.{p.id} 的 GameObject 引用为 null！", this);
                    ok = false;
                }
                if (!seen.Add(p.id))
                {
                    Debug.LogError($"[UIManager] PanelId.{p.id} 重复注册！", this);
                    ok = false;
                }
            }
            if (ok)
                Debug.Log($"[UIManager] 验证通过 ✔  已注册 {_panels.Length} 个面板。", this);
        }

#if UNITY_EDITOR
        /// <summary>仅供 UIManagerEditor 实时可视化面板栈（由栈顶到栈底顺序）。</summary>
        public GameObject[] EditorGetPanelSnapshot() => _panelStack.ToArray();
#endif

        [ContextMenu("测试：打开 Pause 面板")]
        private void EditorOpenPause()       => OpenPanel(PanelId.Pause);

        [ContextMenu("测试：打开 Map 面板")]
        private void EditorOpenMap()         => OpenPanel(PanelId.Map);

        [ContextMenu("测试：打开 Shop 面板")]
        private void EditorOpenShop()        => OpenPanel(PanelId.Shop);

        [ContextMenu("测试：关闭栈顶面板")]
        private void EditorCloseTop()        => CloseTopPanel();
    }
}