EnglewoodLAB/Assets/Scripts/UVC/UIToolkit/UTKThemeManager.cs

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

namespace UVC.UIToolkit
{
    /// <summary>
    /// UIToolkit 테마 관리자.
    /// 런타임에서 Light/Dark 테마 전환을 지원하며, 모든 UTK 컴포넌트에 일관된 스타일을 적용합니다.
    /// </summary>
    /// <remarks>
    /// <para><b>테마 매니저란?</b></para>
    /// <para>
    /// UTKThemeManager는 애플리케이션 전체의 UI 테마(색상, 스타일)를 중앙에서 관리합니다.
    /// 싱글톤 패턴으로 구현되어 어디서든 <c>UTKThemeManager.Instance</c>로 접근 가능합니다.
    /// </para>
    ///
    /// <para><b>스타일시트 로드 순서:</b></para>
    /// <list type="number">
    /// <item><description>UTKVariables.uss - 레이아웃 변수 (spacing, radius, font-size)</description></item>
    /// <item><description>UTKThemeDark/Light.uss - 테마별 색상 변수</description></item>
    /// <item><description>UTKComponents.uss - 공통 컴포넌트 스타일</description></item>
    /// <item><description>UTKDefaultStyle.uss - Unity 기본 요소 오버라이드 (선택)</description></item>
    /// </list>
    ///
    /// <para><b>주요 기능:</b></para>
    /// <list type="bullet">
    /// <item><description><c>RegisterRoot()</c> - UIDocument 루트에 테마 등록</description></item>
    /// <item><description><c>SetTheme()</c> - 테마 변경 (Dark/Light)</description></item>
    /// <item><description><c>ToggleTheme()</c> - 테마 토글</description></item>
    /// <item><description><c>ApplyThemeToElement()</c> - 개별 요소에 테마 적용</description></item>
    /// <item><description><c>OnThemeChanged</c> - 테마 변경 이벤트 구독</description></item>
    /// </list>
    ///
    /// <para><b>사용 시점:</b></para>
    /// <list type="bullet">
    /// <item><description>UIDocument 초기화 시 <c>RegisterRoot()</c> 호출</description></item>
    /// <item><description>UTK 컴포넌트 내부에서 자동으로 <c>ApplyThemeToElement()</c> 호출</description></item>
    /// <item><description>설정 화면에서 테마 전환 버튼 클릭 시 <c>ToggleTheme()</c> 호출</description></item>
    /// </list>
    /// </remarks>
    /// <example>
    /// <para><b>기본 사용법 - UIDocument에 테마 등록:</b></para>
    /// <code>
    /// public class MyUIController : MonoBehaviour
    /// {
    ///     [SerializeField] private UIDocument _uiDocument;
    ///
    ///     void Start()
    ///     {
    ///         // UIDocument 루트에 테마 스타일시트 등록
    ///         var root = _uiDocument.rootVisualElement;
    ///         UTKThemeManager.Instance.RegisterRoot(root);
    ///     }
    ///
    ///     void OnDestroy()
    ///     {
    ///         // 정리 (선택사항)
    ///         var root = _uiDocument.rootVisualElement;
    ///         UTKThemeManager.Instance.UnregisterRoot(root);
    ///     }
    /// }
    /// </code>
    ///
    /// <para><b>테마 전환:</b></para>
    /// <code>
    /// // 특정 테마로 변경
    /// UTKThemeManager.Instance.SetTheme(UTKTheme.Light);
    ///
    /// // 토글 (Dark ↔ Light)
    /// UTKThemeManager.Instance.ToggleTheme();
    ///
    /// // 현재 테마 확인
    /// if (UTKThemeManager.Instance.IsDarkTheme)
    /// {
    ///     Debug.Log("다크 테마 사용 중");
    /// }
    /// </code>
    ///
    /// <para><b>테마 변경 이벤트 구독:</b></para>
    /// <code>
    /// void OnEnable()
    /// {
    ///     UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
    /// }
    ///
    /// void OnDisable()
    /// {
    ///     UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
    /// }
    ///
    /// private void OnThemeChanged(UTKTheme newTheme)
    /// {
    ///     Debug.Log($"테마 변경됨: {newTheme}");
    ///     // 테마에 따른 추가 로직 (아이콘 변경 등)
    /// }
    /// </code>
    ///
    /// <para><b>커스텀 스타일 값 가져오기:</b></para>
    /// <code>
    /// // USS 변수에서 색상 값 읽기
    /// var primaryColor = new CustomStyleProperty<Color>("--color-btn-primary");
    /// var color = UTKThemeManager.GetColor(myElement, primaryColor, Color.blue);
    ///
    /// // USS 변수에서 float 값 읽기
    /// var spacing = new CustomStyleProperty<float>("--space-m");
    /// var value = UTKThemeManager.GetFloat(myElement, spacing, 8f);
    /// </code>
    ///
    /// <para><b>UTK 컴포넌트에서 사용 (내부 구현):</b></para>
    /// <code>
    /// [UxmlElement]
    /// public partial class MyCustomComponent : VisualElement, IDisposable
    /// {
    ///     private bool _disposed;
    ///
    ///     public MyCustomComponent()
    ///     {
    ///         // 컴포넌트에 테마 스타일 적용
    ///         UTKThemeManager.Instance.ApplyThemeToElement(this);
    ///
    ///         // 테마 변경 구독 (Attach/Detach 쌍으로 관리)
    ///         SubscribeToThemeChanges();
    ///     }
    ///
    ///     private void SubscribeToThemeChanges()
    ///     {
    ///         UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
    ///         RegisterCallback<AttachToPanelEvent>(OnAttachToPanelForTheme);
    ///         RegisterCallback<DetachFromPanelEvent>(OnDetachFromPanelForTheme);
    ///     }
    ///
    ///     private void OnAttachToPanelForTheme(AttachToPanelEvent evt)
    ///     {
    ///         UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
    ///         UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
    ///         UTKThemeManager.Instance.ApplyThemeToElement(this);
    ///     }
    ///
    ///     private void OnDetachFromPanelForTheme(DetachFromPanelEvent evt)
    ///     {
    ///         UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
    ///     }
    ///
    ///     private void OnThemeChanged(UTKTheme theme)
    ///     {
    ///         UTKThemeManager.Instance.ApplyThemeToElement(this);
    ///     }
    ///
    ///     public void Dispose()
    ///     {
    ///         if (_disposed) return;
    ///         _disposed = true;
    ///         UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
    ///         UnregisterCallback<AttachToPanelEvent>(OnAttachToPanelForTheme);
    ///         UnregisterCallback<DetachFromPanelEvent>(OnDetachFromPanelForTheme);
    ///     }
    /// }
    /// </code>
    ///
    /// <para><b>테마 전환 버튼 구현:</b></para>
    /// <code>
    /// var themeToggle = new UTKButton("테마 전환", UTKButtonVariant.Secondary);
    /// themeToggle.clicked += () =>
    /// {
    ///     UTKThemeManager.Instance.ToggleTheme();
    ///     var icon = UTKThemeManager.Instance.IsDarkTheme
    ///         ? UTKMaterialIcons.DarkMode
    ///         : UTKMaterialIcons.LightMode;
    ///     themeToggle.SetMaterialIcon(icon);
    /// };
    /// </code>
    /// </example>
    public class UTKThemeManager
    {
        #region Singleton
        private static UTKThemeManager? _instance;
        public static UTKThemeManager Instance => _instance ??= new UTKThemeManager();

        private UTKThemeManager()
        {
            LoadStyleSheets();
        }
        #endregion

        #region Constants
        private const string VARIABLES_PATH = "UIToolkit/Style/UTKVariables";
        private const string THEME_DARK_PATH = "UIToolkit/Style/UTKThemeDark";
        private const string THEME_LIGHT_PATH = "UIToolkit/Style/UTKThemeLight";
        private const string COMPONENTS_PATH = "UIToolkit/Style/UTKComponents";
        private const string DEFAULT_STYLE_PATH = "UIToolkit/Style/UTKDefaultStyle";
        #endregion

        #region Fields
        private StyleSheet? _variablesSheet;
        private StyleSheet? _themeDarkSheet;
        private StyleSheet? _themeLightSheet;
        private StyleSheet? _componentsSheet;
        private StyleSheet? _defaultStyleSheet;

        private readonly HashSet<VisualElement> _registeredRoots = new();
        private UTKTheme _currentTheme = UTKTheme.Dark;
        #endregion

        #region Properties
        /// <summary>현재 적용된 테마</summary>
        public UTKTheme CurrentTheme => _currentTheme;

        /// <summary>다크 테마 여부</summary>
        public bool IsDarkTheme => _currentTheme == UTKTheme.Dark;
        #endregion

        #region Events
        /// <summary>테마 변경 이벤트</summary>
        public event Action<UTKTheme>? OnThemeChanged;
        #endregion

        #region Initialization
        private void LoadStyleSheets()
        {
            _variablesSheet = Resources.Load<StyleSheet>(VARIABLES_PATH);
            _themeDarkSheet = Resources.Load<StyleSheet>(THEME_DARK_PATH);
            _themeLightSheet = Resources.Load<StyleSheet>(THEME_LIGHT_PATH);
            _componentsSheet = Resources.Load<StyleSheet>(COMPONENTS_PATH);
            _defaultStyleSheet = Resources.Load<StyleSheet>(DEFAULT_STYLE_PATH);
        }
        #endregion

        #region Public Methods
        /// <summary>
        /// VisualElement 루트에 테마 스타일시트를 등록합니다.
        /// UIDocument의 rootVisualElement나 커스텀 VisualElement를 전달하세요.
        /// </summary>
        /// <param name="root">스타일시트를 적용할 VisualElement</param>
        /// <param name="includeDefaultStyle">UTKDefaultStyle.uss 포함 여부 (Unity 기본 요소 스타일)</param>
        public void RegisterRoot(VisualElement root, bool includeDefaultStyle = true)
        {
            if (root == null || _registeredRoots.Contains(root))
                return;

            _registeredRoots.Add(root);
            ApplyThemeToRoot(root, includeDefaultStyle);
        }

        /// <summary>
        /// 등록된 루트에서 스타일시트를 제거합니다.
        /// </summary>
        /// <param name="root">제거할 VisualElement</param>
        public void UnregisterRoot(VisualElement root)
        {
            if (root == null)
                return;

            _registeredRoots.Remove(root);
            RemoveThemeFromRoot(root);
        }

        /// <summary>
        /// 테마를 전환합니다.
        /// </summary>
        /// <param name="theme">적용할 테마</param>
        public void SetTheme(UTKTheme theme)
        {
            if (_currentTheme == theme)
                return;

            _currentTheme = theme;

            // 모든 등록된 루트에 테마 적용
            foreach (var root in _registeredRoots)
            {
                ApplyThemeToRoot(root, true);
            }

            OnThemeChanged?.Invoke(_currentTheme);
        }

        /// <summary>
        /// 테마를 토글합니다 (Dark ↔ Light).
        /// </summary>
        public void ToggleTheme()
        {
            SetTheme(_currentTheme == UTKTheme.Dark ? UTKTheme.Light : UTKTheme.Dark);
        }

        /// <summary>
        /// 스타일시트만 반환합니다 (수동 적용용).
        /// </summary>
        /// <returns>현재 테마에 해당하는 스타일시트 배열</returns>
        public StyleSheet?[] GetStyleSheets(bool includeDefaultStyle = true)
        {
            var currentThemeSheet = _currentTheme == UTKTheme.Dark ? _themeDarkSheet : _themeLightSheet;

            if (includeDefaultStyle)
            {
                return new[] { _variablesSheet, currentThemeSheet, _componentsSheet, _defaultStyleSheet };
            }
            else
            {
                return new[] { _variablesSheet, currentThemeSheet, _componentsSheet };
            }
        }

        /// <summary>
        /// 특정 컴포넌트에 필요한 스타일시트만 추가합니다.
        /// 이미 루트에 등록된 경우 호출할 필요 없음.
        /// </summary>
        /// <param name="element">스타일을 적용할 요소</param>
        public void ApplyThemeToElement(VisualElement element)
        {
            if (element == null)
                return;

            var currentThemeSheet = _currentTheme == UTKTheme.Dark ? _themeDarkSheet : _themeLightSheet;
            var otherThemeSheet = _currentTheme == UTKTheme.Dark ? _themeLightSheet : _themeDarkSheet;

            // 이전 테마 제거
            if (otherThemeSheet != null && element.styleSheets.Contains(otherThemeSheet))
                element.styleSheets.Remove(otherThemeSheet);

            // 현재 테마가 이미 있다면 제거 후 다시 추가 (순서 보장)
            if (currentThemeSheet != null && element.styleSheets.Contains(currentThemeSheet))
                element.styleSheets.Remove(currentThemeSheet);

            if (_variablesSheet != null && !element.styleSheets.Contains(_variablesSheet))
                element.styleSheets.Add(_variablesSheet);

            // 현재 테마 적용
            if (currentThemeSheet != null)
                element.styleSheets.Add(currentThemeSheet);

            if (_componentsSheet != null && !element.styleSheets.Contains(_componentsSheet))
                element.styleSheets.Add(_componentsSheet);
        }
        #endregion

        #region Private Methods
        private void ApplyThemeToRoot(VisualElement root, bool includeDefaultStyle)
        {
            var currentThemeSheet = _currentTheme == UTKTheme.Dark ? _themeDarkSheet : _themeLightSheet;
            var otherThemeSheet = _currentTheme == UTKTheme.Dark ? _themeLightSheet : _themeDarkSheet;

            // 이전 테마 제거
            if (otherThemeSheet != null && root.styleSheets.Contains(otherThemeSheet))
                root.styleSheets.Remove(otherThemeSheet);

            // Variables 추가 (없는 경우에만)
            if (_variablesSheet != null && !root.styleSheets.Contains(_variablesSheet))
                root.styleSheets.Add(_variablesSheet);
            else
                Debug.Log($"[UTKThemeManager] Variables 스킵 - null: {_variablesSheet == null}, contains: {_variablesSheet != null && root.styleSheets.Contains(_variablesSheet)}");

            // 현재 테마 추가 (없는 경우에만)
            if (currentThemeSheet != null && !root.styleSheets.Contains(currentThemeSheet))
                root.styleSheets.Add(currentThemeSheet);

            // Components 추가 (없는 경우에만)
            if (_componentsSheet != null && !root.styleSheets.Contains(_componentsSheet))
                root.styleSheets.Add(_componentsSheet);
            else
                Debug.Log($"[UTKThemeManager] Components 스킵 - null: {_componentsSheet == null}, contains: {_componentsSheet != null && root.styleSheets.Contains(_componentsSheet)}");

            // DefaultStyle 추가 (없는 경우에만)
            if (includeDefaultStyle && _defaultStyleSheet != null && !root.styleSheets.Contains(_defaultStyleSheet))
                root.styleSheets.Add(_defaultStyleSheet);
            else
                Debug.Log($"[UTKThemeManager] DefaultStyle 스킵 - null: {_defaultStyleSheet == null}, includeDefaultStyle: {includeDefaultStyle}, contains: {_defaultStyleSheet != null && root.styleSheets.Contains(_defaultStyleSheet)}");

            Debug.Log($"[UTKThemeManager] ApplyThemeToRoot 완료 - styleSheets.count(after): {root.styleSheets.count}");
            
        }

        private void RemoveThemeFromRoot(VisualElement root)
        {
            if (_variablesSheet != null && root.styleSheets.Contains(_variablesSheet))
                root.styleSheets.Remove(_variablesSheet);
            if (_themeDarkSheet != null && root.styleSheets.Contains(_themeDarkSheet))
                root.styleSheets.Remove(_themeDarkSheet);
            if (_themeLightSheet != null && root.styleSheets.Contains(_themeLightSheet))
                root.styleSheets.Remove(_themeLightSheet);
            if (_componentsSheet != null && root.styleSheets.Contains(_componentsSheet))
                root.styleSheets.Remove(_componentsSheet);
            if (_defaultStyleSheet != null && root.styleSheets.Contains(_defaultStyleSheet))
                root.styleSheets.Remove(_defaultStyleSheet);
        }
        #endregion

        #region Static Helpers
        /// <summary>
        /// 현재 테마의 변수 값을 가져옵니다.
        /// VisualElement가 패널에 연결된 후에만 동작합니다.
        /// </summary>
        public static Color GetColor(VisualElement element, CustomStyleProperty<Color> property, Color fallback)
        {
            if (element?.customStyle == null)
                return fallback;

            return element.customStyle.TryGetValue(property, out var color) ? color : fallback;
        }

        /// <summary>
        /// 현재 테마의 float 값을 가져옵니다.
        /// </summary>
        public static float GetFloat(VisualElement element, CustomStyleProperty<float> property, float fallback)
        {
            if (element?.customStyle == null)
                return fallback;

            return element.customStyle.TryGetValue(property, out var value) ? value : fallback;
        }

        /// <summary>
        /// 현재 테마의 int 값을 가져옵니다.
        /// </summary>
        public static int GetInt(VisualElement element, CustomStyleProperty<int> property, int fallback)
        {
            if (element?.customStyle == null)
                return fallback;

            return element.customStyle.TryGetValue(property, out var value) ? value : fallback;
        }
        #endregion
    }

    /// <summary>
    /// 지원하는 테마 종류.
    /// </summary>
    /// <remarks>
    /// <para>각 테마는 해당 USS 파일의 색상 변수를 사용합니다:</para>
    /// <list type="bullet">
    /// <item><description><c>Dark</c> - UTKThemeDark.uss (어두운 배경, 밝은 텍스트)</description></item>
    /// <item><description><c>Light</c> - UTKThemeLight.uss (밝은 배경, 어두운 텍스트)</description></item>
    /// </list>
    /// </remarks>
    public enum UTKTheme
    {
        /// <summary>다크 테마 (기본값)</summary>
        Dark,
        /// <summary>라이트 테마</summary>
        Light
    }
}