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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 토글 버튼 그룹 컴포넌트.
    /// Unity ToggleButtonGroup을 래핑하여 커스텀 스타일을 적용합니다.
    /// </summary>
    /// <example>
    /// <para><b>C# 코드에서 사용:</b></para>
    /// <code>
    /// // 토글 버튼 그룹 생성
    /// var group = new UTKToggleButtonGroup();
    /// group.Add(new Button { text = "왼쪽" });
    /// group.Add(new Button { text = "가운데" });
    /// group.Add(new Button { text = "오른쪽" });
    /// 
    /// // 단일 선택 모드
    /// group.allowEmptySelection = false;
    /// 
    /// // 다중 선택 모드
    /// group.isMultipleSelection = true;
    /// 
    /// // 선택 변경 이벤트
    /// group.OnSelectionChanged += (indices) => {
    ///     Debug.Log($"선택됨: {string.Join(", ", indices)}");
    /// };
    /// </code>
    /// <para><b>UXML에서 사용:</b></para>
    /// <code>
    /// <ui:UXML xmlns:utk="UVC.UIToolkit">
    ///     <utk:UTKToggleButtonGroup allow-empty-selection="false">
    ///         <ui:Button text="왼쪽" />
    ///         <ui:Button text="가운데" />
    ///         <ui:Button text="오른쪽" />
    ///     </utk:UTKToggleButtonGroup>
    /// </ui:UXML>
    /// </code>
    /// </example>
    [UxmlElement]
    public partial class UTKToggleButtonGroup : ToggleButtonGroup, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Button/UTKToggleButtonGroup";
        #endregion

        #region Fields
        private bool _disposed;
        private bool _isEnabled = true;
        #endregion

        #region Events
        /// <summary>선택 변경 이벤트</summary>
        public event Action<IEnumerable<int>>? OnSelectionChanged;
        #endregion

        #region Properties
        /// <summary>활성화 상태</summary>
        [UxmlAttribute("is-enabled")]
        public bool IsEnabled
        {
            get => _isEnabled;
            set
            {
                _isEnabled = value;
                SetEnabled(value);
                EnableInClassList("utk-toggle-group--disabled", !value);
            }
        }
        #endregion

        #region Constructor
        public UTKToggleButtonGroup() : 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-toggle-group");
        }

        private void SetupEvents()
        {
            RegisterCallback<ChangeEvent<ToggleButtonGroupState>>(OnValueChanged);
        }

        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 OnValueChanged(ChangeEvent<ToggleButtonGroupState> evt)
        {
            var state = evt.newValue;
            var buffer = new int[state.length];
            var activeOptions = state.GetActiveOptions(buffer);
            var result = new List<int>();
            foreach (var idx in activeOptions)
            {
                result.Add(idx);
            }
            OnSelectionChanged?.Invoke(result);
        }
        #endregion

        #region Methods
        /// <summary>
        /// 토글 버튼 추가
        /// </summary>
        public void AddButton(string text, string? icon = null)
        {
            var button = new Button { text = text };
            button.AddToClassList("utk-toggle-group__button");
            if (!string.IsNullOrEmpty(icon))
            {
                var iconLabel = new Label(icon);
                iconLabel.AddToClassList("utk-toggle-group__icon");
                button.Insert(0, iconLabel);
            }
            Add(button);
        }
        #endregion

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

            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            UnregisterCallback<AttachToPanelEvent>(OnAttachToPanelForTheme);
            UnregisterCallback<DetachFromPanelEvent>(OnDetachFromPanelForTheme);
            OnSelectionChanged = null;
            UnregisterCallback<ChangeEvent<ToggleButtonGroupState>>(OnValueChanged);
        }
        #endregion
    }
}