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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 토글 스위치 컴포넌트.
    /// Unity Toggle을 래핑하여 커스텀 스타일을 적용합니다.
    /// </summary>
    /// <example>
    /// <para><b>C# 코드에서 사용:</b></para>
    /// <code>
    /// // 기본 토글
    /// var toggle = new UTKToggle();
    /// toggle.label = "알림 받기";
    /// toggle.IsOn = true;
    /// toggle.OnValueChanged += (isOn) => Debug.Log($"토글: {isOn}");
    /// 
    /// // 상호작용 불가능 (읽기 전용, 프로그래밍 방식으로만 변경 가능)
    /// var readOnlyToggle = new UTKToggle("읽기 전용 토글");
    /// readOnlyToggle.IsOn = true;
    /// readOnlyToggle.IsInteractive = false; // 사용자 클릭/키보드 입력 차단
    /// readOnlyToggle.SetOn(false, true); // 프로그래밍 방식으로는 변경 가능
    /// 
    /// // IsEnabled vs IsInteractive
    /// var disabledToggle = new UTKToggle("완전 비활성화");
    /// disabledToggle.IsEnabled = false; // 시각적 비활성화 + 모든 변경 불가
    /// 
    /// var nonInteractiveToggle = new UTKToggle("상호작용 비활성화");
    /// nonInteractiveToggle.IsInteractive = false; // 사용자 입력만 차단, 시각적 활성화 유지
    /// </code>
    /// <para><b>UXML에서 사용:</b></para>
    /// <code>
    /// <ui:UXML xmlns:utk="UVC.UIToolkit">
    ///     <!-- 기본 토글 -->
    ///     <utk:UTKToggle label="다크 모드" />
    ///     
    ///     <!-- 기본값 켜짐 -->
    ///     <utk:UTKToggle label="자동 저장" value="true" />
    ///     
    ///     <!-- 비활성화 -->
    ///     <utk:UTKToggle label="프리미엄 기능" is-enabled="false" />
    ///     
    ///     <!-- 상호작용 불가능 (읽기 전용) -->
    ///     <utk:UTKToggle label="시스템 상태" value="true" is-interactive="false" />
    /// </ui:UXML>
    /// </code>
    /// </example>
    [UxmlElement]
    public partial class UTKToggle : Toggle, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Button/UTKToggle";
        #endregion

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

        #region Events
        /// <summary>상태 변경 이벤트</summary>
        public event Action<bool>? OnValueChanged;
        #endregion

        #region Properties
        /// <summary>토글 상태</summary>
        [UxmlAttribute("is-on")]
        public bool IsOn
        {
            get => value;
            set => SetOn(value, true);
        }

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

        /// <summary>
        /// 상호작용 가능 여부. false일 경우 마우스/키보드 입력을 무시하지만 프로그래밍 방식으로는 값 변경 가능.
        /// IsEnabled와 달리 시각적으로는 활성화 상태를 유지합니다.
        /// </summary>
        [UxmlAttribute("is-interactive")]
        public bool IsInteractive
        {
            get => _isInteractive;
            set
            {
                _isInteractive = value;
                UpdateInteractiveState();
                EnableInClassList("utk-toggle--non-interactive", !value);
            }
        }
        #endregion

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

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

            SetupStyles();
            SetupEvents();
            SubscribeToThemeChanges();
        }

        public UTKToggle(string label) : this()
        {
            this.label = label;
        }
        #endregion

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

        private void SetupEvents()
        {
            RegisterCallback<ChangeEvent<bool>>(OnToggleValueChanged);
            RegisterCallback<MouseDownEvent>(OnMouseDown, TrickleDown.TrickleDown);
            RegisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);
        }

        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 OnToggleValueChanged(ChangeEvent<bool> evt)
        {
            EnableInClassList("utk-toggle--on", evt.newValue);
            OnValueChanged?.Invoke(evt.newValue);
        }

        private void OnMouseDown(MouseDownEvent evt)
        {
            if (!_isInteractive)
            {
                evt.StopImmediatePropagation();
                evt.PreventDefault();
            }
        }

        private void OnKeyDown(KeyDownEvent evt)
        {
            if (!_isInteractive)
            {
                // Space나 Enter 키로 토글 변경 방지
                if (evt.keyCode == KeyCode.Space || evt.keyCode == KeyCode.Return || evt.keyCode == KeyCode.KeypadEnter)
                {
                    evt.StopImmediatePropagation();
                    evt.PreventDefault();
                }
            }
        }
        #endregion

        #region Methods
        /// <summary>
        /// 상태 설정
        /// </summary>
        public void SetOn(bool newValue, bool notify)
        {
            if (value == newValue) return;

            SetValueWithoutNotify(newValue);
            EnableInClassList("utk-toggle--on", newValue);

            if (notify)
            {
                OnValueChanged?.Invoke(newValue);
            }
        }

        /// <summary>
        /// 상호작용 상태 업데이트
        /// </summary>
        private void UpdateInteractiveState()
        {
            // IsInteractive가 false일 때 포커스 불가능하게 설정
            focusable = _isInteractive;
        }
        #endregion

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

            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            UnregisterCallback<AttachToPanelEvent>(OnAttachToPanelForTheme);
            UnregisterCallback<DetachFromPanelEvent>(OnDetachFromPanelForTheme);
            OnValueChanged = null;
            UnregisterCallback<ChangeEvent<bool>>(OnToggleValueChanged);
            UnregisterCallback<MouseDownEvent>(OnMouseDown, TrickleDown.TrickleDown);
            UnregisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);
        }
        #endregion
    }
}