using System;
using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// UI面板类型，用于确定面板的层级和行为
/// </summary>
public enum UIPanelType
{
    Base,        // 基础面板（主界面等）
    Normal,      // 普通面板（功能面板）
    Popup,       // 弹出面板（用户管理等）
    Dialog,      // 对话框（确认弹窗等）
    System       // 系统面板（警报覆盖等），最高优先级
}

/// <summary>
/// UI面板信息
/// </summary>
public class UIPanelInfo
{
    public BasePanel Panel { get; set; }
    public UIPanelType Type { get; set; }
    public int Layer { get; set; }
    public bool IsModal { get; set; }  // 是否为模态面板
    public string PanelName { get; set; }
    
    public UIPanelInfo(BasePanel panel, UIPanelType type, bool isModal = false)
    {
        Panel = panel;
        Type = type;
        IsModal = isModal;
        PanelName = panel.GetType().Name;
    }
}

/// <summary>
/// 增强版UI管理器
/// 使用栈管理面板导航，支持层级管理和优雅的返回逻辑
/// </summary>
public class EnhancedUIManager : MonoBehaviour
{
    #region 单例
    private static EnhancedUIManager _instance;
    public static EnhancedUIManager Instance
    {
        get
        {
            if (_instance == null)
            {
                var go = new GameObject("EnhancedUIManager");
                _instance = go.AddComponent<EnhancedUIManager>();
                DontDestroyOnLoad(go);
            }
            return _instance;
        }
    }
    #endregion

    #region 字段和属性
    [Header("UI容器")]
    public Transform CanvasRoot;
    public Transform BaseLayer;      // 基础层（主界面）
    public Transform NormalLayer;    // 普通层（功能面板）
    public Transform PopupLayer;     // 弹窗层（用户管理）
    public Transform DialogLayer;    // 对话框层（确认弹窗）
    public Transform SystemLayer;    // 系统层（警报覆盖）

    // 面板管理
    private Dictionary<string, UIPanelInfo> _allPanels = new Dictionary<string, UIPanelInfo>();
    private Stack<UIPanelInfo> _navigationStack = new Stack<UIPanelInfo>();
    private List<UIPanelInfo> _activeDialogs = new List<UIPanelInfo>();
    private UIPanelInfo _currentBasePanel;

    // 层级管理
    private readonly Dictionary<UIPanelType, int> _baseLayerValues = new Dictionary<UIPanelType, int>
    {
        { UIPanelType.Base, 0 },
        { UIPanelType.Normal, 100 },
        { UIPanelType.Popup, 200 },
        { UIPanelType.Dialog, 300 },
        { UIPanelType.System, 400 }
    };

    private int _nextLayerIncrement = 0;
    #endregion

    #region 初始化
    void Awake()
    {
        if (_instance == null)
        {
            _instance = this;
            DontDestroyOnLoad(gameObject);
            InitializeLayers();
        }
        else if (_instance != this)
        {
            Destroy(gameObject);
        }
    }

    private void InitializeLayers()
    {
        // 查找或创建Canvas
        if (CanvasRoot == null)
        {
            var canvas = FindObjectOfType<Canvas>();
            if (canvas == null)
            {
                var canvasGO = new GameObject("Canvas");
                canvas = canvasGO.AddComponent<Canvas>();
                canvas.renderMode = RenderMode.ScreenSpaceOverlay;
                canvasGO.AddComponent<UnityEngine.UI.CanvasScaler>();
                canvasGO.AddComponent<UnityEngine.UI.GraphicRaycaster>();
            }
            CanvasRoot = canvas.transform;
        }

        // 创建层级
        BaseLayer = CreateLayer("BaseLayer", 0);
        NormalLayer = CreateLayer("NormalLayer", 100);
        PopupLayer = CreateLayer("PopupLayer", 200);
        DialogLayer = CreateLayer("DialogLayer", 300);
        SystemLayer = CreateLayer("SystemLayer", 400);
    }

    private Transform CreateLayer(string layerName, int sortingOrder)
    {
        var layerGO = new GameObject(layerName);
        layerGO.transform.SetParent(CanvasRoot, false);
        
        var canvas = layerGO.AddComponent<Canvas>();
        canvas.overrideSorting = true;
        canvas.sortingOrder = sortingOrder;
        
        layerGO.AddComponent<UnityEngine.UI.GraphicRaycaster>();
        
        // 设置为全屏
        var rectTransform = layerGO.GetComponent<RectTransform>();
        rectTransform.anchorMin = Vector2.zero;
        rectTransform.anchorMax = Vector2.one;
        rectTransform.sizeDelta = Vector2.zero;
        rectTransform.anchoredPosition = Vector2.zero;
        
        return layerGO.transform;
    }
    #endregion

    #region 面板显示
    /// <summary>
    /// 显示面板
    /// </summary>
    public T ShowPanel<T>(UIPanelType panelType = UIPanelType.Normal, bool isModal = false, bool isFade = true) where T : BasePanel
    {
        string panelName = typeof(T).Name;
        
        // 检查是否已存在
        if (_allPanels.ContainsKey(panelName))
        {
            BringPanelToFront(_allPanels[panelName]);
            return _allPanels[panelName].Panel as T;
        }

        // 创建新面板
        var panelGO = Instantiate(Resources.Load<GameObject>("UI/" + panelName));
        if (panelGO == null)
        {
            Debug.LogError($"Failed to load UI prefab: {panelName}");
            return null;
        }

        var panel = panelGO.GetComponent<T>();
        if (panel == null)
        {
            Debug.LogError($"Panel {panelName} does not have component {typeof(T)}");
            Destroy(panelGO);
            return null;
        }

        // 设置层级
        Transform targetLayer = GetTargetLayer(panelType);
        panelGO.transform.SetParent(targetLayer, false);

        // 创建面板信息
        var panelInfo = new UIPanelInfo(panel, panelType, isModal);
        panelInfo.Layer = _baseLayerValues[panelType] + _nextLayerIncrement++;
        
        // 设置Canvas层级
        SetPanelLayer(panelGO, panelInfo.Layer);

        // 注册面板
        _allPanels[panelName] = panelInfo;

        // 处理导航逻辑
        HandlePanelNavigation(panelInfo);

        // 显示面板
        panel.ShowMe(isFade);
        
        // Debug.Log($"Showed panel {panelName} at layer {panelInfo.Layer}");
        return panel;
    }

    private Transform GetTargetLayer(UIPanelType panelType)
    {
        return panelType switch
        {
            UIPanelType.Base => BaseLayer,
            UIPanelType.Normal => NormalLayer,
            UIPanelType.Popup => PopupLayer,
            UIPanelType.Dialog => DialogLayer,
            UIPanelType.System => SystemLayer,
            _ => NormalLayer
        };
    }

    private void SetPanelLayer(GameObject panelGO, int layer)
    {
        var canvas = panelGO.GetComponent<Canvas>();
        if (canvas == null)
        {
            canvas = panelGO.AddComponent<Canvas>();
            panelGO.AddComponent<UnityEngine.UI.GraphicRaycaster>();
        }
        canvas.overrideSorting = true;
        canvas.sortingOrder = layer;
    }

    private void HandlePanelNavigation(UIPanelInfo panelInfo)
    {
        switch (panelInfo.Type)
        {
            case UIPanelType.Base:
                // 基础面板，清空导航栈
                ClearNavigationStack();
                _currentBasePanel = panelInfo;
                break;
                
            case UIPanelType.Normal:
            case UIPanelType.Popup:
                // 普通面板，加入导航栈
                _navigationStack.Push(panelInfo);
                break;
                
            case UIPanelType.Dialog:
                // 对话框，加入对话框列表
                _activeDialogs.Add(panelInfo);
                break;
                
            case UIPanelType.System:
                // 系统面板，不影响导航
                break;
        }
    }
    #endregion

    #region 面板关闭
    /// <summary>
    /// 关闭面板
    /// </summary>
    public void HidePanel<T>(bool isFade = true) where T : BasePanel
    {
        string panelName = typeof(T).Name;
        if (_allPanels.ContainsKey(panelName))
        {
            HidePanel(_allPanels[panelName], isFade);
        }
    }

    private void HidePanel(UIPanelInfo panelInfo, bool isFade = true)
    {
        if (panelInfo?.Panel == null) return;

        // 从导航管理中移除
        RemoveFromNavigation(panelInfo);

        // 隐藏面板
        if (isFade)
        {
            panelInfo.Panel.HideMe(true, () => {
                DestroyPanel(panelInfo);
            });
        }
        else
        {
            DestroyPanel(panelInfo);
        }

        // Debug.Log($"Hid panel {panelInfo.PanelName}");
    }

    private void RemoveFromNavigation(UIPanelInfo panelInfo)
    {
        // 从对话框列表移除
        _activeDialogs.Remove(panelInfo);

        // 从导航栈移除
        if (_navigationStack.Contains(panelInfo))
        {
            var tempStack = new Stack<UIPanelInfo>();
            while (_navigationStack.Count > 0)
            {
                var item = _navigationStack.Pop();
                if (item != panelInfo)
                {
                    tempStack.Push(item);
                }
            }
            while (tempStack.Count > 0)
            {
                _navigationStack.Push(tempStack.Pop());
            }
        }

        // 如果是基础面板
        if (panelInfo == _currentBasePanel)
        {
            _currentBasePanel = null;
        }
    }

    private void DestroyPanel(UIPanelInfo panelInfo)
    {
        if (panelInfo?.Panel != null)
        {
            Destroy(panelInfo.Panel.gameObject);
            _allPanels.Remove(panelInfo.PanelName);
        }
    }
    #endregion

    #region 导航功能
    /// <summary>
    /// 返回到主界面
    /// </summary>
    public void ReturnToHome()
    {
        // 关闭所有非基础面板
        var panelsToClose = new List<UIPanelInfo>();
        
        foreach (var panel in _allPanels.Values)
        {
            if (panel.Type != UIPanelType.Base)
            {
                panelsToClose.Add(panel);
            }
        }

        foreach (var panel in panelsToClose)
        {
            HidePanel(panel, false);
        }

        // 清空导航栈
        ClearNavigationStack();

        Debug.Log("Returned to home");
    }

    /// <summary>
    /// 返回上一个面板
    /// </summary>
    public bool GoBack()
    {
        // 优先关闭对话框
        if (_activeDialogs.Count > 0)
        {
            var lastDialog = _activeDialogs[_activeDialogs.Count - 1];
            HidePanel(lastDialog, true);
            return true;
        }

        // 然后处理导航栈
        if (_navigationStack.Count > 0)
        {
            var currentPanel = _navigationStack.Pop();
            HidePanel(currentPanel, true);
            return true;
        }

        return false;
    }

    /// <summary>
    /// 关闭所有对话框
    /// </summary>
    public void CloseAllDialogs()
    {
        var dialogsToClose = new List<UIPanelInfo>(_activeDialogs);
        foreach (var dialog in dialogsToClose)
        {
            HidePanel(dialog, false);
        }
    }

    private void ClearNavigationStack()
    {
        _navigationStack.Clear();
    }

    private void BringPanelToFront(UIPanelInfo panelInfo)
    {
        if (panelInfo?.Panel == null) return;

        panelInfo.Layer = _baseLayerValues[panelInfo.Type] + _nextLayerIncrement++;
        SetPanelLayer(panelInfo.Panel.gameObject, panelInfo.Layer);
        
        // 重新显示
        if (!panelInfo.Panel.gameObject.activeInHierarchy)
        {
            panelInfo.Panel.ShowMe(true);
        }
    }
    #endregion

    #region 实用功能
    /// <summary>
    /// 获取面板
    /// </summary>
    public T GetPanel<T>() where T : BasePanel
    {
        string panelName = typeof(T).Name;
        if (_allPanels.ContainsKey(panelName))
        {
            return _allPanels[panelName].Panel as T;
        }
        return null;
    }

    /// <summary>
    /// 检查面板是否显示
    /// </summary>
    public bool IsPanelShowing<T>() where T : BasePanel
    {
        return GetPanel<T>() != null;
    }

    /// <summary>
    /// 获取当前活动面板数量
    /// </summary>
    public int GetActivePanelCount()
    {
        return _allPanels.Count;
    }

    /// <summary>
    /// 获取导航栈深度
    /// </summary>
    public int GetNavigationDepth()
    {
        return _navigationStack.Count;
    }

    /// <summary>
    /// 调试信息
    /// </summary>
    public void PrintDebugInfo()
    {
        Debug.Log($"=== UI Manager Debug Info ===");
        Debug.Log($"Active Panels: {_allPanels.Count}");
        Debug.Log($"Navigation Stack Depth: {_navigationStack.Count}");
        Debug.Log($"Active Dialogs: {_activeDialogs.Count}");
        
        foreach (var panel in _allPanels.Values)
        {
            Debug.Log($"Panel: {panel.PanelName}, Type: {panel.Type}, Layer: {panel.Layer}");
        }
    }
    #endregion

    #region Unity事件
    void Update()
    {
        // 处理返回键
        if (Input.GetKeyDown(KeyCode.Escape))
        {
            if (!GoBack())
            {
                // 如果无法返回，可以考虑退出应用或显示退出确认
                Debug.Log("Cannot go back further");
            }
        }
    }
    #endregion
}