using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

/// <summary>
/// Tab键导航系统
/// 自动管理InputField之间的Tab键切换
/// </summary>
public class TabNavigationSystem : MonoBehaviour
{
    [Header("导航设置")]
    public List<Selectable> NavigationOrder = new List<Selectable>(); // 导航顺序
    public bool AutoDetectInputFields = true; // 自动检测InputField
    public bool WrapNavigation = true; // 是否循环导航
    public bool EnableShiftReverse = true; // 是否支持Shift+Tab反向导航
    
    [Header("调试")]
    public bool ShowDebugInfo = false;

    private int _currentIndex = -1;
    private EventSystem _eventSystem;

    void Start()
    {
        Initialize();
    }

    void Update()
    {
        HandleTabInput();
    }

    private void Initialize()
    {
        _eventSystem = EventSystem.current;
        
        if (AutoDetectInputFields)
        {
            AutoDetectNavigationElements();
        }
        
        // 设置初始焦点
        if (NavigationOrder.Count > 0)
        {
            SetFocus(0);
        }
        
        if (ShowDebugInfo)
        {
            Debug.Log($"TabNavigationSystem: 初始化完成，找到 {NavigationOrder.Count} 个可导航元素");
        }
    }

    /// <summary>
    /// 自动检测可导航元素
    /// </summary>
    private void AutoDetectNavigationElements()
    {
        NavigationOrder.Clear();
        
        // 查找所有InputField
        var inputFields = FindObjectsOfType<TMP_InputField>();
        foreach (var inputField in inputFields)
        {
            if (inputField.interactable && inputField.gameObject.activeInHierarchy)
            {
                NavigationOrder.Add(inputField);
            }
        }
        
        // 查找所有传统InputField
        var legacyInputFields = FindObjectsOfType<InputField>();
        foreach (var inputField in legacyInputFields)
        {
            if (inputField.interactable && inputField.gameObject.activeInHierarchy)
            {
                NavigationOrder.Add(inputField);
            }
        }
        
        // 根据层级顺序排序
        NavigationOrder.Sort((a, b) => 
        {
            // 先按Y坐标排序（从上到下）
            var posA = a.transform.position;
            var posB = b.transform.position;
            
            if (Mathf.Abs(posA.y - posB.y) > 0.1f)
            {
                return posB.y.CompareTo(posA.y); // Y坐标大的在前（上面的先）
            }
            
            // Y坐标相近时按X坐标排序（从左到右）
            return posA.x.CompareTo(posB.x);
        });
    }

    /// <summary>
    /// 处理Tab键输入
    /// </summary>
    private void HandleTabInput()
    {
        if (NavigationOrder.Count == 0) return;

        // 检查Tab键
        if (Input.GetKeyDown(KeyCode.Tab))
        {
            bool reverse = EnableShiftReverse && (Input.GetKey(KeyCode.LeftShift) || Input.GetKey(KeyCode.RightShift));
            
            if (reverse)
            {
                NavigatePrevious();
            }
            else
            {
                NavigateNext();
            }
        }
        
        // 检查Enter键（移动到下一个）
        if (Input.GetKeyDown(KeyCode.Return) || Input.GetKeyDown(KeyCode.KeypadEnter))
        {
            // 如果当前焦点是InputField，则移动到下一个
            var currentSelection = _eventSystem?.currentSelectedGameObject;
            if (currentSelection != null)
            {
                var inputField = currentSelection.GetComponent<TMP_InputField>();
                var legacyInputField = currentSelection.GetComponent<InputField>();
                
                if (inputField != null || legacyInputField != null)
                {
                    NavigateNext();
                }
            }
        }
    }

    /// <summary>
    /// 导航到下一个元素
    /// </summary>
    public void NavigateNext()
    {
        if (NavigationOrder.Count == 0) return;

        _currentIndex++;
        
        if (WrapNavigation)
        {
            _currentIndex %= NavigationOrder.Count;
        }
        else
        {
            _currentIndex = Mathf.Min(_currentIndex, NavigationOrder.Count - 1);
        }

        SetFocus(_currentIndex);
    }

    /// <summary>
    /// 导航到上一个元素
    /// </summary>
    public void NavigatePrevious()
    {
        if (NavigationOrder.Count == 0) return;

        _currentIndex--;
        
        if (WrapNavigation)
        {
            if (_currentIndex < 0)
            {
                _currentIndex = NavigationOrder.Count - 1;
            }
        }
        else
        {
            _currentIndex = Mathf.Max(_currentIndex, 0);
        }

        SetFocus(_currentIndex);
    }

    /// <summary>
    /// 设置焦点到指定索引的元素
    /// </summary>
    public void SetFocus(int index)
    {
        if (index < 0 || index >= NavigationOrder.Count) return;
        if (_eventSystem == null) return;

        var target = NavigationOrder[index];
        if (target == null || !target.interactable || !target.gameObject.activeInHierarchy)
        {
            // 跳过不可用的元素
            if (WrapNavigation)
            {
                NavigateNext();
            }
            return;
        }

        _currentIndex = index;
        
        // 设置选中
        _eventSystem.SetSelectedGameObject(target.gameObject);
        
        // 如果是InputField，激活输入
        var inputField = target.GetComponent<TMP_InputField>();
        if (inputField != null)
        {
            inputField.Select();
            inputField.ActivateInputField();
        }
        else
        {
            var legacyInputField = target.GetComponent<InputField>();
            if (legacyInputField != null)
            {
                legacyInputField.Select();
                legacyInputField.ActivateInputField();
            }
        }

        if (ShowDebugInfo)
        {
            Debug.Log($"TabNavigationSystem: 焦点切换到 {target.name} (索引: {index})");
        }
    }

    /// <summary>
    /// 手动添加导航元素
    /// </summary>
    public void AddNavigationElement(Selectable element)
    {
        if (element != null && !NavigationOrder.Contains(element))
        {
            NavigationOrder.Add(element);
        }
    }

    /// <summary>
    /// 移除导航元素
    /// </summary>
    public void RemoveNavigationElement(Selectable element)
    {
        if (NavigationOrder.Contains(element))
        {
            int index = NavigationOrder.IndexOf(element);
            NavigationOrder.Remove(element);
            
            // 调整当前索引
            if (_currentIndex >= index && _currentIndex > 0)
            {
                _currentIndex--;
            }
        }
    }

    /// <summary>
    /// 刷新导航列表
    /// </summary>
    public void RefreshNavigation()
    {
        if (AutoDetectInputFields)
        {
            AutoDetectNavigationElements();
        }
    }

    /// <summary>
    /// 获取当前焦点元素
    /// </summary>
    public Selectable GetCurrentElement()
    {
        if (_currentIndex >= 0 && _currentIndex < NavigationOrder.Count)
        {
            return NavigationOrder[_currentIndex];
        }
        return null;
    }

    /// <summary>
    /// 获取当前焦点索引
    /// </summary>
    public int GetCurrentIndex()
    {
        return _currentIndex;
    }

    /// <summary>
    /// 跳转到指定元素
    /// </summary>
    public void FocusElement(Selectable element)
    {
        int index = NavigationOrder.IndexOf(element);
        if (index >= 0)
        {
            SetFocus(index);
        }
    }
}

/// <summary>
/// Tab导航辅助组件
/// 可以附加到单独的InputField上，提供更精细的控制
/// </summary>
public class TabNavigationHelper : MonoBehaviour
{
    [Header("导航设置")]
    public Selectable NextElement; // 下一个元素
    public Selectable PreviousElement; // 上一个元素
    public bool SkipThisElement = false; // 是否跳过此元素

    private Selectable _thisSelectable;

    void Start()
    {
        _thisSelectable = GetComponent<Selectable>();
    }

    void Update()
    {
        if (SkipThisElement) return;

        // 检查是否是当前选中的元素
        if (EventSystem.current?.currentSelectedGameObject == gameObject)
        {
            if (Input.GetKeyDown(KeyCode.Tab))
            {
                bool reverse = Input.GetKey(KeyCode.LeftShift) || Input.GetKey(KeyCode.RightShift);
                
                if (reverse && PreviousElement != null)
                {
                    FocusElement(PreviousElement);
                }
                else if (!reverse && NextElement != null)
                {
                    FocusElement(NextElement);
                }
            }
        }
    }

    private void FocusElement(Selectable element)
    {
        if (element != null && element.interactable && element.gameObject.activeInHierarchy)
        {
            EventSystem.current?.SetSelectedGameObject(element.gameObject);
            
            var inputField = element.GetComponent<TMP_InputField>();
            if (inputField != null)
            {
                inputField.Select();
                inputField.ActivateInputField();
            }
            else
            {
                var legacyInputField = element.GetComponent<InputField>();
                if (legacyInputField != null)
                {
                    legacyInputField.Select();
                    legacyInputField.ActivateInputField();
                }
            }
        }
    }
}