#nullable enable
using System;
using UnityEngine;
using UnityEngine.UIElements;
using UVC.UI.Commands;

namespace UVC.UIToolkit
{
    /// <summary>
    /// 앱 최소화 버튼 컴포넌트.
    /// 클릭 시 <see cref="MinimizeApplicationCommand"/>를 실행합니다.
    /// 고정 크기: width=45, height=32.
    /// </summary>
    /// <example>
    /// <para><b>C# 코드에서 사용:</b></para>
    /// <code>
    /// var btn = new UTKMinimizeAppButton();
    /// container.Add(btn);
    ///
    /// // 비활성화
    /// btn.IsEnabled = false;
    /// </code>
    /// <para><b>UXML에서 사용:</b></para>
    /// <code>
    /// <ui:UXML xmlns:utk="UVC.UIToolkit">
    ///     <utk:UTKMinimizeAppButton />
    ///     <utk:UTKMinimizeAppButton is-enabled="false" />
    /// </ui:UXML>
    /// </code>
    /// </example>
    [UxmlElement]
    public partial class UTKMinimizeAppButton : VisualElement, IDisposable
    {
        #region Constants
        private const string UXML_PATH = "UIToolkit/Button/UTKMinimizeAppButton";
        private const string USS_PATH = "UIToolkit/Button/UTKMinimizeAppButtonUss";
        private const int ICON_SIZE = 18;
        #endregion

        #region Fields
        private bool _disposed;
        private bool _isEnabled = true;
        private Label? _materialIconLabel;
        private readonly MinimizeApplicationCommand _command = new();
        #endregion

        #region Properties
        /// <summary>활성화 상태. false이면 시각적 비활성화 + 클릭 무시.</summary>
        [UxmlAttribute("is-enabled")]
        public bool IsEnabled
        {
            get => _isEnabled;
            set
            {
                _isEnabled = value;
                SetEnabled(value);
                EnableInClassList("utk-minimize-app-btn--disabled", !value);
            }
        }
        #endregion

        #region Constructor
        public UTKMinimizeAppButton()
        {
            UTKThemeManager.Instance.ApplyThemeToElement(this);

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

            CreateUI();
            SetupEvents();
            SubscribeToThemeChanges();
        }
        #endregion

        #region Setup
        private void CreateUI()
        {
            AddToClassList("utk-minimize-app-btn");
            focusable = true;
            pickingMode = PickingMode.Position;

            var asset = Resources.Load<VisualTreeAsset>(UXML_PATH);
            if (asset != null)
            {
                var root = asset.Instantiate();
                _materialIconLabel = root.Q<Label>("material-icon");
                Add(root);
            }
            else
            {
                CreateUIFallback();
            }

            ApplyIcon();
        }

        private void CreateUIFallback()
        {
            _materialIconLabel = new Label
            {
                name = "material-icon",
                pickingMode = PickingMode.Ignore
            };
            _materialIconLabel.AddToClassList("utk-minimize-app-btn__material-icon");
            Add(_materialIconLabel);
        }

        private void ApplyIcon()
        {
            if (_materialIconLabel == null) return;
            // Material Icon: remove (최소화 아이콘)
            string iconChar = UTKMaterialIcons.GetIcon("remove");
            if (iconChar == string.Empty)
            {
                iconChar = UTKMaterialIcons.Remove;
            }
            _materialIconLabel.text = iconChar;
            UTKMaterialIcons.ApplyIconStyle(_materialIconLabel, ICON_SIZE);
            _materialIconLabel.style.display = DisplayStyle.Flex;
        }

        private void SetupEvents()
        {
            RegisterCallback<ClickEvent>(OnClick);
            RegisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);
            RegisterCallback<AttachToPanelEvent>(OnAttachToPanel);
            RegisterCallback<DetachFromPanelEvent>(OnDetachFromPanel);
        }

        private void SubscribeToThemeChanges()
        {
            UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
        }

        private void OnAttachToPanel(AttachToPanelEvent evt)
        {
            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
            UTKThemeManager.Instance.ApplyThemeToElement(this);
        }

        private void OnDetachFromPanel(DetachFromPanelEvent evt)
        {
            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
        }

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

        #region Event Handlers
        private void OnClick(ClickEvent evt)
        {
            if (!_isEnabled) return;
            _command.Execute();
            evt.StopPropagation();
        }

        private void OnKeyDown(KeyDownEvent evt)
        {
            if (!_isEnabled) return;
            if (evt.keyCode == KeyCode.Space || evt.keyCode == KeyCode.Return || evt.keyCode == KeyCode.KeypadEnter)
            {
                _command.Execute();
                evt.StopPropagation();
            }
        }
        #endregion

        #region IDisposable
        /// <summary>이벤트 콜백 및 테마 구독을 해제합니다.</summary>
        public void Dispose()
        {
            if (_disposed) return;
            _disposed = true;

            UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            UnregisterCallback<ClickEvent>(OnClick);
            UnregisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);
            UnregisterCallback<AttachToPanelEvent>(OnAttachToPanel);
            UnregisterCallback<DetachFromPanelEvent>(OnDetachFromPanel);
        }
        #endregion
    }
}