#nullable enable
using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

namespace UVC.UIToolkit
{
    /// <summary>
    /// 탭 뷰 컴포넌트.
    /// Unity TabView를 래핑하여 커스텀 스타일을 적용합니다.
    /// 여러 콘텐츠 페이지를 탭으로 전환하여 표시합니다.
    /// </summary>
    /// <remarks>
    /// <para><b>TabView(탭 뷰)란?</b></para>
    /// <para>
    /// TabView는 여러 페이지의 콘텐츠를 탭 버튼으로 전환하여 표시하는 UI 컴포넌트입니다.
    /// 같은 공간에 여러 내용을 담을 수 있어 화면 공간을 효율적으로 사용합니다.
    /// 설정 페이지, 에디터 창, 프로필 화면 등에서 널리 사용됩니다.
    /// </para>
    ///
    /// <para><b>TabView 구성:</b></para>
    /// <list type="bullet">
    /// <item><description>탭 헤더 - 탭 버튼들이 나열된 영역</description></item>
    /// <item><description>탭 콘텐츠 - 선택된 탭의 내용이 표시되는 영역</description></item>
    /// </list>
    ///
    /// <para><b>주요 속성:</b></para>
    /// <list type="bullet">
    /// <item><description><c>SelectedIndex</c> - 현재 선택된 탭 인덱스</description></item>
    /// <item><description><c>UTKTabs</c> - 탭 목록 (읽기 전용)</description></item>
    /// </list>
    ///
    /// <para><b>주요 메서드:</b></para>
    /// <list type="bullet">
    /// <item><description><c>AddUTKTab(string, VisualElement)</c> - 탭 추가</description></item>
    /// <item><description><c>AddTab(UTKTab)</c> - UTKTab 인스턴스 추가</description></item>
    /// <item><description><c>RemoveTab(UTKTab)</c> - 탭 제거</description></item>
    /// <item><description><c>ClearTabs()</c> - 모든 탭 제거</description></item>
    /// </list>
    ///
    /// <para><b>이벤트:</b></para>
    /// <list type="bullet">
    /// <item><description><c>OnTabChanged</c> - 탭이 변경될 때 (인덱스, Tab 전달)</description></item>
    /// </list>
    ///
    /// <para><b>실제 활용 예시:</b></para>
    /// <list type="bullet">
    /// <item><description>설정 창 - 일반/고급/정보 탭</description></item>
    /// <item><description>에디터 - 씬/게임/애셋 탭</description></item>
    /// <item><description>프로필 - 정보/활동/설정 탭</description></item>
    /// <item><description>문서 뷰어 - 다중 문서 탭</description></item>
    /// </list>
    /// </remarks>
    /// <example>
    /// <para><b>C# 코드에서 사용:</b></para>
    /// <code>
    /// // 탭 뷰 생성
    /// var tabView = new UTKTabView();
    /// 
    /// // 탭 추가
    /// var tab1 = tabView.AddTab("일반", UTKMaterialIcons.Settings);
    /// tab1.Add(new Label("일반 설정 내용"));
    /// 
    /// var tab2 = tabView.AddTab("고급", UTKMaterialIcons.Build);
    /// tab2.Add(new Label("고급 설정 내용"));
    /// 
    /// // 탭 변경 이벤트
    /// tabView.OnTabChanged += (index, tab) => Debug.Log($"탭 {index} 선택됨");
    /// 
    /// // 탭 선택
    /// tabView.SelectedIndex = 0;
    /// </code>
    /// <para><b>UXML에서 사용:</b></para>
    /// <code>
    /// <ui:UXML xmlns:utk="UVC.UIToolkit">
    ///     <utk:UTKTabView>
    ///         <utk:UTKTab label="일반">
    ///             <ui:Label text="일반 탭 내용" />
    ///         </utk:UTKTab>
    ///         <utk:UTKTab label="고급">
    ///             <ui:Label text="고급 탭 내용" />
    ///         </utk:UTKTab>
    ///     </utk:UTKTabView>
    /// </ui:UXML>
    /// </code>
    /// </example>
    [UxmlElement]
    public partial class UTKTabView : TabView, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Tab/UTKTabView";
        #endregion

        #region Fields
        private bool _disposed;
        private readonly List<UTKTab> _utkTabs = new();
        #endregion

        #region Events
        /// <summary>탭 변경 이벤트</summary>
        public event Action<int, Tab?>? OnTabChanged;
        #endregion

        #region Properties
        /// <summary>선택된 탭 인덱스</summary>
        public int SelectedIndex
        {
            get => selectedTabIndex;
            set => selectedTabIndex = value;
        }

        /// <summary>UTK 탭 목록</summary>
        public IReadOnlyList<UTKTab> UTKTabs => _utkTabs;
        #endregion

        #region Constructor
        public UTKTabView() : base()
        {
            UTKThemeManager.Instance.ApplyThemeToElement(this);

            var uss = Resources.Load<StyleSheet>(USS_PATH);
            if (uss != null)
            {
                styleSheets.Add(uss);
            }

            SetupStyles();
            SetupEvents();
            SubscribeToThemeChanges();
        }
        #endregion

        #region Setup
        private void SetupStyles()
        {
            AddToClassList("utk-tabview");
        }

        private void SetupEvents()
        {
            this.RegisterCallback<ChangeEvent<int>>(OnTabIndexChanged);
        }

        private void SubscribeToThemeChanges()
        {
            UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
            RegisterCallback<DetachFromPanelEvent>(_ =>
            {
                UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            });
        }

        private void OnThemeChanged(UTKTheme theme)
        {
            UTKThemeManager.Instance.ApplyThemeToElement(this);
        }
        #endregion

        #region Event Handlers
        private void OnTabIndexChanged(ChangeEvent<int> evt)
        {
            UpdateTabSelection();
            OnTabChanged?.Invoke(evt.newValue, activeTab);
        }

        private void UpdateTabSelection()
        {
            for (int i = 0; i < _utkTabs.Count; i++)
            {
                _utkTabs[i].IsSelected = (i == selectedTabIndex);
            }
        }
        #endregion

        #region Methods
        /// <summary>
        /// UTK 탭 추가
        /// </summary>
        public UTKTab AddUTKTab(string text, VisualElement? content = null)
        {
            var tab = new UTKTab(text);
            if (content != null)
            {
                tab.Add(content);
            }
            AddTab(tab);
            return tab;
        }

        /// <summary>
        /// 탭 추가
        /// </summary>
        public void AddTab(UTKTab tab)
        {
            _utkTabs.Add(tab);
            Add(tab);

            if (_utkTabs.Count == 1)
            {
                tab.IsSelected = true;
            }
        }

        /// <summary>
        /// 탭 제거
        /// </summary>
        public void RemoveTab(UTKTab tab)
        {
            int index = _utkTabs.IndexOf(tab);
            if (index < 0) return;

            _utkTabs.RemoveAt(index);
            tab.RemoveFromHierarchy();
            tab.Dispose();
        }

        /// <summary>
        /// 모든 탭 제거
        /// </summary>
        public void ClearTabs()
        {
            foreach (var tab in _utkTabs)
            {
                tab.RemoveFromHierarchy();
                tab.Dispose();
            }
            _utkTabs.Clear();
        }
        #endregion

        #region IDisposable
        public void Dispose()
        {
            if (_disposed) return;
            _disposed = true;

            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;

            foreach (var tab in _utkTabs)
            {
                tab.Dispose();
            }
            _utkTabs.Clear();

            OnTabChanged = null;
        }
        #endregion
    }
}