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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 스크롤 뷰 컴포넌트.
    /// Unity ScrollView를 래핑하여 커스텀 스타일을 적용합니다.
    /// </summary>
    /// <example>
    /// <para><b>C# 코드에서 사용:</b></para>
    /// <code>
    /// // 기본 스크롤 뷰
    /// var scrollView = new UTKScrollView();
    /// scrollView.Add(new Label("내용 1"));
    /// scrollView.Add(new Label("내용 2"));
    /// scrollView.Add(new Label("내용 3"));
    /// 
    /// // 스크롤 모드 설정
    /// var verticalScroll = new UTKScrollView(ScrollViewMode.Vertical);
    /// var horizontalScroll = new UTKScrollView(ScrollViewMode.Horizontal);
    /// </code>
    /// <para><b>UXML에서 사용:</b></para>
    /// <code>
    /// <ui:UXML xmlns:utk="UVC.UIToolkit">
    ///     <!-- 기본 스크롤 뷰 -->
    ///     <utk:UTKScrollView style="height: 200px;">
    ///         <ui:Label text="항목 1" />
    ///         <ui:Label text="항목 2" />
    ///         <ui:Label text="항목 3" />
    ///     </utk:UTKScrollView>
    ///     
    ///     <!-- 수직 스크롤만 -->
    ///     <utk:UTKScrollView mode="Vertical" />
    ///     
    ///     <!-- 수평 스크롤만 -->
    ///     <utk:UTKScrollView mode="Horizontal" />
    /// </ui:UXML>
    /// </code>
    /// </example>
    [UxmlElement]
    public partial class UTKScrollView : ScrollView, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Common/UTKScrollView";
        #endregion

        #region Fields
        private bool _disposed;
        #endregion

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

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

            SetupStyles();
            SubscribeToThemeChanges();
        }

        public UTKScrollView(ScrollViewMode mode) : this()
        {
            this.mode = mode;
        }
        #endregion

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

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

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

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

            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
        }
        #endregion
    }
}