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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 멀티 컬럼 트리 뷰 컴포넌트.
    /// Unity MultiColumnTreeView를 래핑하여 커스텀 스타일을 적용합니다.
    /// </summary>
    [UxmlElement]
    public partial class UTKMultiColumnTreeView : MultiColumnTreeView, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/List/UTKMultiColumnTreeView";
        #endregion

        #region Fields
        private bool _disposed;
        #endregion

        #region Events
        /// <summary>아이템 선택 이벤트</summary>
        public event Action<int>? OnItemSelected;
        /// <summary>아이템 더블클릭 이벤트</summary>
        public event Action<int>? OnItemDoubleClicked;
        #endregion

        #region Constructor
        public UTKMultiColumnTreeView() : 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-multicolumn-treeview");
        }

        private void SetupEvents()
        {
            selectionChanged += OnSelectionChanged;
            itemsChosen += OnItemsChosen;
        }

        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);
        }
        #endregion

        #region Event Handlers
        private void OnSelectionChanged(IEnumerable<object> items)
        {
            OnItemSelected?.Invoke(selectedIndex);
        }

        private void OnItemsChosen(IEnumerable<object> items)
        {
            OnItemDoubleClicked?.Invoke(selectedIndex);
        }
        #endregion

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

            selectionChanged -= OnSelectionChanged;
            itemsChosen -= OnItemsChosen;
            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            UnregisterCallback<AttachToPanelEvent>(OnAttachToPanelForTheme);
            UnregisterCallback<DetachFromPanelEvent>(OnDetachFromPanelForTheme);
            OnItemSelected = null;
            OnItemDoubleClicked = null;
        }
        #endregion
    }
}