#nullable enable
using System;
using UnityEngine;
using UnityEngine.UIElements;
using UVC.UIToolkit.Common;

namespace UVC.UIToolkit.Input
{
    /// <summary>
    /// 숫자 입력 필드에 위/아래 스테퍼 버튼이 붙은 컴포넌트
    /// TextInput 오른쪽에 위, 아래 버튼이 세로로 배치됨
    /// 마우스 호버 상태에서 휠로 값 조절 가능
    /// </summary>
    [UxmlElement]
    public partial class UTKNumberStepper : VisualElement
    {
        #region Constants
        private const string USS_PATH = "UIToolkit/Input/UTKNumberStepper";
        #endregion

        #region UXML Attributes
        [UxmlAttribute]
        public int Value
        {
            get => _value;
            set => SetValue(value);
        }

        [UxmlAttribute]
        public int MinValue
        {
            get => _minValue;
            set
            {
                _minValue = value;
                ClampValue();
            }
        }

        [UxmlAttribute]
        public int MaxValue
        {
            get => _maxValue;
            set
            {
                _maxValue = value;
                ClampValue();
            }
        }

        [UxmlAttribute]
        public int Step
        {
            get => _step;
            set => _step = Math.Max(1, value);
        }

        [UxmlAttribute]
        public bool WrapAround
        {
            get => _wrapAround;
            set => _wrapAround = value;
        }
        #endregion

        #region Fields
        private int _value;
        private int _minValue = int.MinValue;
        private int _maxValue = int.MaxValue;
        private int _step = 1;
        private bool _wrapAround;
        private bool _isUpdating;
        private bool _isHovered;

        private TextField? _textField;
        private Button? _upButton;
        private Button? _downButton;
        #endregion

        #region Events
        /// <summary>값이 변경될 때 발생</summary>
        public event Action<int>? OnValueChanged;

        /// <summary>Tab 키가 눌렸을 때 발생 (다음 요소로 포커스 이동용)</summary>
        public event Action? OnTabPressed;

        /// <summary>Shift+Tab 키가 눌렸을 때 발생 (이전 요소로 포커스 이동용)</summary>
        public event Action? OnShiftTabPressed;
        #endregion

        #region Constructor
        public UTKNumberStepper()
        {
            UTKThemeManager.Instance.ApplyThemeToElement(this);
            LoadStyleSheet();
            CreateUI();
            SetupEvents();
            SubscribeToThemeChanges();
        }

        public UTKNumberStepper(int minValue, int maxValue, int initialValue = 0, int step = 1)
        {
            _minValue = minValue;
            _maxValue = maxValue;
            _step = Math.Max(1, step);
            _value = Mathf.Clamp(initialValue, minValue, maxValue);

            UTKThemeManager.Instance.ApplyThemeToElement(this);
            LoadStyleSheet();
            CreateUI();
            SetupEvents();
            SubscribeToThemeChanges();
            UpdateDisplay();
        }

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

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

            // 패널에서 분리될 때 이벤트 구독 해제
            RegisterCallback<DetachFromPanelEvent>(_ =>
            {
                UTKThemeManager.Instance.OnThemeChanged -= OnThemeChanged;
            });
        }

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

        #region Public Methods
        public void SetValue(int newValue, bool notify = true)
        {
            int clampedValue = ClampValueInternal(newValue);
            if (_value != clampedValue)
            {
                _value = clampedValue;
                UpdateDisplay();
                if (notify)
                {
                    OnValueChanged?.Invoke(_value);
                }
            }
        }

        public void Increment()
        {
            if (_wrapAround && _value + _step > _maxValue)
            {
                SetValue(_minValue);
            }
            else
            {
                SetValue(_value + _step);
            }
        }

        public void Decrement()
        {
            if (_wrapAround && _value - _step < _minValue)
            {
                SetValue(_maxValue);
            }
            else
            {
                SetValue(_value - _step);
            }
        }

        public void SetRange(int min, int max)
        {
            _minValue = min;
            _maxValue = max;
            ClampValue();
        }

        /// <summary>텍스트 필드에 포커스를 설정합니다.</summary>
        public new void Focus()
        {
            _textField?.Focus();
        }
        #endregion

        #region Private Methods - UI Creation
        private void CreateUI()
        {
            AddToClassList("utk-number-stepper");

            // Text Field
            _textField = new TextField { name = "stepper-input" };
            _textField.AddToClassList("utk-number-stepper__input");

            // TextField 내부 input 스타일링
            _textField.RegisterCallback<AttachToPanelEvent>(_ =>
            {
                var input = _textField.Q<VisualElement>("unity-text-input");
                if (input != null)
                {
                    input.AddToClassList("utk-number-stepper__text-input");
                }
            });

            Add(_textField);

            // Button Container (위/아래 버튼을 세로로 배치)
            var buttonContainer = new VisualElement { name = "stepper-buttons" };
            buttonContainer.AddToClassList("utk-number-stepper__buttons");

            // Up Button
            _upButton = new Button { name = "stepper-up", text = UTKMaterialIcons.KeyboardArrowUp };
            _upButton.AddToClassList("utk-number-stepper__btn");
            _upButton.AddToClassList("utk-number-stepper__btn--up");
            UTKMaterialIcons.ApplyIconStyle(_upButton, 14);
            buttonContainer.Add(_upButton);

            // Down Button
            _downButton = new Button { name = "stepper-down", text = UTKMaterialIcons.KeyboardArrowDown };
            _downButton.AddToClassList("utk-number-stepper__btn");
            _downButton.AddToClassList("utk-number-stepper__btn--down");
            UTKMaterialIcons.ApplyIconStyle(_downButton, 14);
            buttonContainer.Add(_downButton);

            Add(buttonContainer);

            UpdateDisplay();
        }

        private void SetupEvents()
        {
            _upButton?.RegisterCallback<ClickEvent>(_ => Increment());
            _downButton?.RegisterCallback<ClickEvent>(_ => Decrement());

            _textField?.RegisterValueChangedCallback(evt =>
            {
                if (_isUpdating) return;

                if (int.TryParse(evt.newValue, out int parsed))
                {
                    SetValue(parsed);
                }
                else
                {
                    // 유효하지 않은 입력이면 이전 값으로 복원
                    UpdateDisplay();
                }
            });

            // 키보드 이벤트 (위/아래 화살표)
            _textField?.RegisterCallback<KeyDownEvent>(evt =>
            {
                if (evt.keyCode == KeyCode.UpArrow)
                {
                    Increment();
                    evt.StopPropagation();
                }
                else if (evt.keyCode == KeyCode.DownArrow)
                {
                    Decrement();
                    evt.StopPropagation();
                }
            });

            // Tab 키 이벤트 - TrickleDown으로 먼저 캡처
            _textField?.RegisterCallback<KeyDownEvent>(evt =>
            {
                if (evt.keyCode == KeyCode.Tab)
                {
                    if (evt.shiftKey && OnShiftTabPressed != null)
                    {
                        // Shift+Tab: 이전 요소로 이동
                        OnShiftTabPressed.Invoke();
                        evt.StopImmediatePropagation();
                    }
                    else if (!evt.shiftKey && OnTabPressed != null)
                    {
                        // Tab: 다음 요소로 이동
                        OnTabPressed.Invoke();
                        evt.StopImmediatePropagation();
                    }
                }
            }, TrickleDown.TrickleDown);

            // 마우스 호버 상태 추적
            RegisterCallback<MouseEnterEvent>(_ => _isHovered = true);
            RegisterCallback<MouseLeaveEvent>(_ => _isHovered = false);

            // 마우스 휠 이벤트 (호버 상태에서만)
            RegisterCallback<WheelEvent>(evt =>
            {
                if (!_isHovered) return;

                if (evt.delta.y < 0)
                {
                    Increment();
                }
                else if (evt.delta.y > 0)
                {
                    Decrement();
                }
                evt.StopPropagation();
            });
        }
        #endregion

        #region Private Methods - Logic
        private void UpdateDisplay()
        {
            if (_textField == null) return;

            _isUpdating = true;
            _textField.value = _value.ToString();
            _isUpdating = false;
        }

        private void ClampValue()
        {
            SetValue(_value, notify: false);
        }

        private int ClampValueInternal(int value)
        {
            return Mathf.Clamp(value, _minValue, _maxValue);
        }
        #endregion
    }
}