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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 모든 PropertyItem View의 기본 추상 클래스입니다.
    /// VisualElement를 상속하여 UXML/C#에서 단독 사용이 가능합니다.
    ///
    /// <para><b>주요 기능:</b></para>
    /// <list type="bullet">
    ///   <item>테마 자동 적용 (UTKThemeManager)</item>
    ///   <item>공통/개별 USS 자동 로드</item>
    ///   <item>Label + Value 레이아웃 제공</item>
    ///   <item>Data 클래스 바인딩 지원</item>
    ///   <item>단독 사용 시 UXML 속성 지원</item>
    /// </list>
    ///
    /// <para><b>관련 리소스:</b></para>
    /// <list type="bullet">
    ///   <item>Resources/UIToolkit/Property/Views/{ViewName}.uxml - 각 뷰 UXML</item>
    ///   <item>Resources/UIToolkit/Property/Views/{ViewName}Uss.uss - 각 뷰 USS</item>
    ///   <item>Resources/UIToolkit/Property/Views/UTKPropertyItemViewCommonUss.uss - 공통 USS</item>
    /// </list>
    /// </summary>
    public abstract class UTKPropertyItemViewBase : VisualElement, IDisposable
    {
        #region Constants
        protected const string UXML_BASE_PATH = "UIToolkit/Property/Views/";
        protected const string USS_BASE_PATH = "UIToolkit/Property/Views/";
        protected const string USS_COMMON_PATH = "UIToolkit/Property/Views/UTKPropertyItemViewCommonUss";

        protected const string USS_CLASS_READONLY = "utk-property-item-view--readonly";
        protected const string USS_CLASS_HIDDEN = "utk-property-item-view--hidden";
        protected const string USS_CLASS_NO_LABEL = "utk-property-item-view--no-label";
        #endregion

        #region Static Cache
        private static readonly Dictionary<string, VisualTreeAsset> _uxmlCache = new();
        private static readonly Dictionary<string, StyleSheet> _ussCache = new();
        private static StyleSheet? _commonUssCache;
        #endregion

        #region Fields
        protected bool _disposed;
        protected UTKLabel? _labelElement;
        protected VisualElement? _valueContainer;

        protected string _label = string.Empty;
        protected bool _isReadOnly = false;
        protected bool _isVisible = true;
        protected bool _showLabel = true;
        protected string? _tooltipText;
        #endregion

        #region Properties
        /// <summary>라벨 텍스트</summary>
        [UxmlAttribute("label")]
        public string Label
        {
            get => _label;
            set
            {
                _label = value;
                if (_labelElement != null)
                {
                    _labelElement.Text = value;
                }
            }
        }

        /// <summary>읽기 전용 여부</summary>
        [UxmlAttribute("is-read-only")]
        public bool IsReadOnly
        {
            get => _isReadOnly;
            set
            {
                if (_isReadOnly != value)
                {
                    _isReadOnly = value;
                    UpdateReadOnlyState();
                }
            }
        }

        /// <summary>표시 여부</summary>
        [UxmlAttribute("is-visible")]
        public bool IsVisible
        {
            get => _isVisible;
            set
            {
                if (_isVisible != value)
                {
                    _isVisible = value;
                    UpdateVisibility();
                }
            }
        }

        /// <summary>툴팁 텍스트</summary>
        [UxmlAttribute("tooltip-text")]
        public string? TooltipText
        {
            get => _tooltipText;
            set
            {
                _tooltipText = value;
                UpdateTooltip();
            }
        }

        /// <summary>라벨 표시 여부 (false면 value가 전체 너비 사용)</summary>
        [UxmlAttribute("show-label")]
        public bool ShowLabel
        {
            get => _showLabel;
            set
            {
                if (_showLabel != value)
                {
                    _showLabel = value;
                    UpdateShowLabelState();
                }
            }
        }
        #endregion

        #region Constructor
        protected UTKPropertyItemViewBase()
        {
            // 1. 테마 적용
            UTKThemeManager.Instance.ApplyThemeToElement(this);

            // 2. 공통 USS 로드
            ApplyCommonStyleSheet();

            // 3. 테마 변경 구독
            SubscribeToThemeChanges();
        }
        #endregion

        #region Abstract Methods
        /// <summary>View 타입 이름 (UXML/USS 파일명에 사용)</summary>
        protected abstract string ViewTypeName { get; }

        /// <summary>값 영역 UI 생성 (하위 클래스에서 구현)</summary>
        protected abstract void CreateValueUI(VisualElement container);

        /// <summary>UI 상태 갱신 (하위 클래스에서 구현)</summary>
        public abstract void RefreshUI();

        /// <summary>읽기 전용 상태 업데이트 (하위 클래스에서 오버라이드)</summary>
        protected abstract void OnReadOnlyStateChanged(bool isReadOnly);
        #endregion

        #region Protected Methods
        /// <summary>
        /// UXML 템플릿에서 UI를 생성합니다.
        /// </summary>
        /// <returns>성공 여부</returns>
        protected bool CreateUIFromUxml()
        {
            var asset = LoadUxmlAsset(ViewTypeName);
            if (asset == null)
            {
                return false;
            }

            var root = asset.Instantiate();
            Add(root);

            // 개별 USS 로드
            ApplyStyleSheet(ViewTypeName + "Uss");

            // 공통 요소 참조 획득
            _labelElement = this.Q<UTKLabel>("label");
            _valueContainer = this.Q<VisualElement>("value-container");

            if (_labelElement != null)
            {
                _labelElement.Text = _label;
            }

            return true;
        }

        /// <summary>
        /// 코드로 기본 UI 레이아웃을 생성합니다 (Fallback).
        /// </summary>
        protected void CreateUIFallback()
        {
            AddToClassList("utk-property-item-view");

            // 개별 USS 로드
            ApplyStyleSheet(ViewTypeName + "Uss");

            // Label
            _labelElement = new UTKLabel(_label, UTKLabel.LabelSize.Body2)
            {
                name = "label"
            };
            _labelElement.AddToClassList("utk-property-item-view__label");
            Add(_labelElement);

            // Value Container
            _valueContainer = new VisualElement { name = "value-container" };
            _valueContainer.AddToClassList("utk-property-item-view__value");
            Add(_valueContainer);

            // 하위 클래스에서 값 UI 생성
            CreateValueUI(_valueContainer);
        }

        /// <summary>읽기 전용 상태 업데이트</summary>
        protected virtual void UpdateReadOnlyState()
        {
            if (_isReadOnly)
            {
                AddToClassList(USS_CLASS_READONLY);
            }
            else
            {
                RemoveFromClassList(USS_CLASS_READONLY);
            }

            OnReadOnlyStateChanged(_isReadOnly);
        }

        /// <summary>표시 상태 업데이트</summary>
        protected virtual void UpdateVisibility()
        {
            style.display = _isVisible ? DisplayStyle.Flex : DisplayStyle.None;

            if (_isVisible)
            {
                RemoveFromClassList(USS_CLASS_HIDDEN);
            }
            else
            {
                AddToClassList(USS_CLASS_HIDDEN);
            }
        }

        /// <summary>툴팁 업데이트</summary>
        protected virtual void UpdateTooltip()
        {
            if (!string.IsNullOrEmpty(_tooltipText))
            {
                this.SetTooltip(_tooltipText);
            }
            else
            {
                this.ClearTooltip();
            }
        }

        /// <summary>라벨 표시 상태 업데이트</summary>
        protected virtual void UpdateShowLabelState()
        {
            if (_showLabel)
            {
                RemoveFromClassList(USS_CLASS_NO_LABEL);
                if (_labelElement != null)
                {
                    _labelElement.style.display = DisplayStyle.Flex;
                }
            }
            else
            {
                AddToClassList(USS_CLASS_NO_LABEL);
                if (_labelElement != null)
                {
                    _labelElement.style.display = DisplayStyle.None;
                }
            }
        }
        #endregion

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

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

        #region StyleSheet Loading
        /// <summary>공통 USS 스타일시트를 적용합니다.</summary>
        protected void ApplyCommonStyleSheet()
        {
            var commonUss = LoadCommonUssAsset();
            if (commonUss != null)
            {
                styleSheets.Add(commonUss);
            }
        }

        /// <summary>개별 USS 스타일시트를 적용합니다.</summary>
        protected void ApplyStyleSheet(string ussName)
        {
            var uss = LoadUssAsset(ussName);
            if (uss != null)
            {
                styleSheets.Add(uss);
            }
        }

        /// <summary>UXML 에셋 로드 (캐시 사용)</summary>
        protected static VisualTreeAsset? LoadUxmlAsset(string uxmlName)
        {
            string path = UXML_BASE_PATH + uxmlName;

            if (_uxmlCache.TryGetValue(path, out var cached))
            {
                return cached;
            }

            var asset = Resources.Load<VisualTreeAsset>(path);
            if (asset != null)
            {
                _uxmlCache[path] = asset;
            }

            return asset;
        }

        /// <summary>공통 USS 에셋 로드 (캐시 사용)</summary>
        protected static StyleSheet? LoadCommonUssAsset()
        {
            if (_commonUssCache != null)
            {
                return _commonUssCache;
            }

            _commonUssCache = Resources.Load<StyleSheet>(USS_COMMON_PATH);
            return _commonUssCache;
        }

        /// <summary>USS 에셋 로드 (캐시 사용)</summary>
        protected static StyleSheet? LoadUssAsset(string ussName)
        {
            string path = USS_BASE_PATH + ussName;

            if (_ussCache.TryGetValue(path, out var cached))
            {
                return cached;
            }

            var asset = Resources.Load<StyleSheet>(path);
            if (asset != null)
            {
                _ussCache[path] = asset;
            }

            return asset;
        }

        /// <summary>모든 캐시 클리어 (에디터 용도)</summary>
        public static void ClearAllCache()
        {
            _uxmlCache.Clear();
            _ussCache.Clear();
            _commonUssCache = null;
        }
        #endregion

        #region Helper Methods
        /// <summary>
        /// PropertyItem의 공통 속성을 View에 적용합니다.
        /// 하위 클래스의 Bind 메서드에서 호출하세요.
        /// </summary>
        protected void ApplyCommonProperties(IUTKPropertyItem item)
        {
            Label = item.Name;
            IsReadOnly = item.IsReadOnly;
            IsVisible = item.IsVisible;
            TooltipText = item.Tooltip;
            ShowLabel = item.ShowLabel;
        }
        #endregion

        #region IDisposable
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (_disposed) return;
            _disposed = true;

            if (disposing)
            {
                UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
                this.ClearTooltip();

                _labelElement = null;
                _valueContainer = null;
            }
        }
        #endregion
    }
}