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

namespace UVC.UIToolkit
{
    /// <summary>
    /// 커스텀 버튼 컴포넌트.
    /// 텍스트와 아이콘을 동시에 표시하거나, 아이콘만 표시할 수 있습니다.
    /// 배경 색상, 외곽선 굵기 등을 설정할 수 있습니다.
    /// </summary>
    [UxmlElement]
    public partial class UTKButton : VisualElement, IDisposable
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Button/UTKButton";
        #endregion

        #region Fields
        private bool _disposed;
        private Label? _iconLabel;
        private Label? _textLabel;

        private string _text = "";
        private string _icon = "";
        private ButtonVariant _variant = ButtonVariant.Normal;
        private ButtonSize _size = ButtonSize.Medium;
        private Color? _backgroundColor;
        private int _borderWidth = -1;
        private bool _iconOnly;
        private bool _isEnabled = true;
        #endregion

        #region Events
        /// <summary>버튼 클릭 이벤트</summary>
        public event Action? OnClicked;
        #endregion

        #region Properties
        /// <summary>버튼 텍스트</summary>
        [UxmlAttribute]
        public string Text
        {
            get => _text;
            set
            {
                _text = value;
                UpdateContent();
            }
        }

        /// <summary>아이콘 (유니코드 문자 또는 텍스트)</summary>
        [UxmlAttribute]
        public string Icon
        {
            get => _icon;
            set
            {
                _icon = value;
                UpdateContent();
            }
        }

        /// <summary>버튼 스타일 변형</summary>
        [UxmlAttribute]
        public ButtonVariant Variant
        {
            get => _variant;
            set
            {
                _variant = value;
                UpdateVariant();
            }
        }

        /// <summary>버튼 크기</summary>
        [UxmlAttribute]
        public ButtonSize Size
        {
            get => _size;
            set
            {
                _size = value;
                UpdateSize();
            }
        }

        /// <summary>커스텀 배경 색상 (null이면 기본 스타일 사용)</summary>
        public Color? BackgroundColor
        {
            get => _backgroundColor;
            set
            {
                _backgroundColor = value;
                UpdateCustomStyles();
            }
        }

        /// <summary>외곽선 굵기 (-1이면 기본값 사용)</summary>
        [UxmlAttribute]
        public int BorderWidth
        {
            get => _borderWidth;
            set
            {
                _borderWidth = value;
                UpdateCustomStyles();
            }
        }

        /// <summary>아이콘만 표시 모드</summary>
        [UxmlAttribute]
        public bool IconOnly
        {
            get => _iconOnly;
            set
            {
                _iconOnly = value;
                UpdateContent();
            }
        }

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

        #region Enums
        public enum ButtonVariant
        {
            Normal,
            Primary,
            Secondary,
            Ghost,
            Danger,
            OutlineNormal,
            OutlinePrimary,
            OutlineDanger
        }

        public enum ButtonSize
        {
            Small,
            Medium,
            Large
        }
        #endregion

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

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

            CreateUI();
            SetupEvents();
            SubscribeToThemeChanges();
        }

        public UTKButton(string text, string icon = "", ButtonVariant variant = ButtonVariant.Normal) : this()
        {
            _text = text;
            _icon = icon;
            _variant = variant;
            UpdateContent();
            UpdateVariant();
        }
        #endregion

        #region UI Creation
        private void CreateUI()
        {
            AddToClassList("utk-button");
            focusable = true;

            _iconLabel = new Label
            {
                name = "icon",
                pickingMode = PickingMode.Ignore
            };
            _iconLabel.AddToClassList("utk-button__icon");
            Add(_iconLabel);

            _textLabel = new Label
            {
                name = "text",
                pickingMode = PickingMode.Ignore
            };
            _textLabel.AddToClassList("utk-button__text");
            Add(_textLabel);

            UpdateContent();
            UpdateVariant();
            UpdateSize();
        }

        private void SetupEvents()
        {
            RegisterCallback<ClickEvent>(OnClick);
            RegisterCallback<KeyDownEvent>(OnKeyDown);
        }

        private void SubscribeToThemeChanges()
        {
            UTKThemeManager.Instance.OnThemeChanged += OnThemeChanged;
            RegisterCallback<DetachFromPanelEvent>(_ =>
            {
                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;
            OnClicked?.Invoke();
            evt.StopPropagation();
        }

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

        #region Update Methods
        private void UpdateContent()
        {
            bool hasIcon = !string.IsNullOrEmpty(_icon);
            bool hasText = !string.IsNullOrEmpty(_text);

            if (_iconLabel != null)
            {
                _iconLabel.text = _icon;
                _iconLabel.style.display = hasIcon ? DisplayStyle.Flex : DisplayStyle.None;
            }

            if (_textLabel != null)
            {
                _textLabel.text = _text;
                _textLabel.style.display = (_iconOnly || !hasText) ? DisplayStyle.None : DisplayStyle.Flex;
            }

            EnableInClassList("utk-button--icon-only", _iconOnly || (hasIcon && !hasText));
            EnableInClassList("utk-button--has-icon", hasIcon && hasText && !_iconOnly);
        }

        private void UpdateVariant()
        {
            RemoveFromClassList("utk-button--normal");
            RemoveFromClassList("utk-button--primary");
            RemoveFromClassList("utk-button--secondary");
            RemoveFromClassList("utk-button--ghost");
            RemoveFromClassList("utk-button--danger");
            RemoveFromClassList("utk-button--outline-normal");
            RemoveFromClassList("utk-button--outline-primary");
            RemoveFromClassList("utk-button--outline-danger");

            var variantClass = _variant switch
            {
                ButtonVariant.Primary => "utk-button--primary",
                ButtonVariant.Secondary => "utk-button--secondary",
                ButtonVariant.Ghost => "utk-button--ghost",
                ButtonVariant.Danger => "utk-button--danger",
                ButtonVariant.OutlineNormal => "utk-button--outline-normal",
                ButtonVariant.OutlinePrimary => "utk-button--outline-primary",
                ButtonVariant.OutlineDanger => "utk-button--outline-danger",
                _ => "utk-button--normal"
            };
            AddToClassList(variantClass);
        }

        private void UpdateSize()
        {
            RemoveFromClassList("utk-button--small");
            RemoveFromClassList("utk-button--medium");
            RemoveFromClassList("utk-button--large");

            var sizeClass = _size switch
            {
                ButtonSize.Small => "utk-button--small",
                ButtonSize.Large => "utk-button--large",
                _ => "utk-button--medium"
            };
            AddToClassList(sizeClass);
        }

        private void UpdateCustomStyles()
        {
            if (_backgroundColor.HasValue)
            {
                style.backgroundColor = _backgroundColor.Value;
            }
            else
            {
                style.backgroundColor = StyleKeyword.Null;
            }

            if (_borderWidth >= 0)
            {
                style.borderTopWidth = _borderWidth;
                style.borderBottomWidth = _borderWidth;
                style.borderLeftWidth = _borderWidth;
                style.borderRightWidth = _borderWidth;
            }
            else
            {
                style.borderTopWidth = StyleKeyword.Null;
                style.borderBottomWidth = StyleKeyword.Null;
                style.borderLeftWidth = StyleKeyword.Null;
                style.borderRightWidth = StyleKeyword.Null;
            }
        }
        #endregion

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

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