#nullable enable
using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;
using UVC.Locale;
using UVC.UIToolkit.Input;

namespace UVC.UIToolkit.Modal
{
    /// <summary>
    /// UIToolkit 기반 날짜/시간 피커 모달
    /// 캘린더 그리드 + 시간 선택 지원
    /// </summary>
    [UxmlElement]
    public partial class UTKDatePicker : VisualElement, IDisposable
    {
        #region Enums
        public enum PickerMode
        {
            DateOnly,
            DateAndTime
        }
        #endregion

        #region Constants
        private const string UXML_PATH = "UIToolkit/Modal/UTKDatePicker";
        private const string USS_PATH = "UIToolkit/Modal/UTKDatePicker";
        private const int DAYS_IN_GRID = 42; // 6 rows x 7 columns
        private static readonly string[] DAY_NAME_KEYS = { "day_sun", "day_mon", "day_tue", "day_wed", "day_thu", "day_fri", "day_sat" };
        #endregion

        #region Fields
        private bool _disposed;
        private PickerMode _mode;
        private DateTime _selectedDate = DateTime.Today;
        private DateTime _displayMonth = new DateTime(DateTime.Today.Year, DateTime.Today.Month, 1);

        private UTKModalBlocker? _blocker;
        private readonly List<Button> _dayButtons = new();

        // UI 요소
        private Label? _titleLabel;
        private Button? _closeButton;
        private Label? _yearMonthLabel;
        private Button? _prevYearButton;
        private Button? _prevMonthButton;
        private Button? _nextMonthButton;
        private Button? _nextYearButton;
        private VisualElement? _dayNamesRow;
        private VisualElement? _timeRow;
        private UTKNumberStepper? _hourStepper;
        private UTKNumberStepper? _minuteStepper;
        private Button? _cancelButton;
        private Button? _confirmButton;
        #endregion

        #region Events
        /// <summary>날짜가 선택되었을 때 발생</summary>
        public event Action<DateTime>? OnDateSelected;

        /// <summary>피커가 닫힐 때 발생</summary>
        public event Action? OnClosed;
        #endregion

        #region Constructor
        public UTKDatePicker()
        {
            // 테마 스타일시트 적용
            UTKThemeManager.Instance.ApplyThemeToElement(this);

            // 컴포넌트 스타일시트 로드
            var styleSheet = Resources.Load<StyleSheet>(USS_PATH);
            if (styleSheet != null)
            {
                styleSheets.Add(styleSheet);
            }

            var visualTree = Resources.Load<VisualTreeAsset>(UXML_PATH);
            if (visualTree != null)
            {
                visualTree.CloneTree(this);
            }
            else
            {
                CreateUI();
            }

            QueryElements();
            SetupEvents();
            SubscribeToThemeChanges();

            // 캘린더 초기화
            UpdateCalendar();
        }

        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 Static Factory
        /// <summary>
        /// 날짜 피커를 표시합니다.
        /// </summary>
        public static UTKDatePicker Show(
            VisualElement parent,
            DateTime initialDate,
            PickerMode mode = PickerMode.DateOnly,
            string title = "Select Date")
        {
            var picker = new UTKDatePicker();
            picker._mode = mode;
            picker._selectedDate = initialDate;
            picker._displayMonth = new DateTime(initialDate.Year, initialDate.Month, 1);

            // 블로커 추가
            picker._blocker = UTKModalBlocker.Show(parent, 0.5f, false);
            picker._blocker.OnBlockerClicked += picker.Close;

            // 피커 추가
            parent.Add(picker);

            // UI 초기화
            picker.SetTitle(title);
            picker.SetTimeVisible(mode == PickerMode.DateAndTime);
            picker.UpdateTimeFields();
            picker.UpdateCalendar();
            picker.CenterOnScreen();

            return picker;
        }
        #endregion

        #region Public Methods
        public void SetDate(DateTime date)
        {
            _selectedDate = date;
            _displayMonth = new DateTime(date.Year, date.Month, 1);
            UpdateTimeFields();
            UpdateCalendar();
        }

        public DateTime GetDate()
        {
            if (_mode == PickerMode.DateAndTime)
            {
                int hour = _hourStepper?.Value ?? 0;
                int minute = _minuteStepper?.Value ?? 0;
                return new DateTime(
                    _selectedDate.Year,
                    _selectedDate.Month,
                    _selectedDate.Day,
                    hour,
                    minute,
                    0
                );
            }
            return _selectedDate.Date;
        }

        public void PreviousYear() => NavigateMonth(-12);
        public void NextYear() => NavigateMonth(12);
        public void PreviousMonth() => NavigateMonth(-1);
        public void NextMonth() => NavigateMonth(1);

        public void Close()
        {
            OnClosed?.Invoke();
            _blocker?.Hide();
            RemoveFromHierarchy();
            Dispose();
        }
        #endregion

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

            // Header
            var header = new VisualElement { name = "header" };
            header.AddToClassList("utk-date-picker__header");

            _titleLabel = new Label("Select Date") { name = "title" };
            _titleLabel.AddToClassList("utk-date-picker__title");

            _closeButton = new Button { name = "close-btn", text = "\u2715" };  // X
            _closeButton.AddToClassList("utk-date-picker__close-btn");

            header.Add(_titleLabel);
            header.Add(_closeButton);
            Add(header);

            // Navigation
            var navRow = new VisualElement { name = "nav-row" };
            navRow.AddToClassList("utk-date-picker__nav-row");

            var leftNav = new VisualElement();
            leftNav.AddToClassList("utk-date-picker__nav-group");

            _prevYearButton = CreateNavButton("prev-year", "\u00AB");  // <<
            _prevYearButton.AddToClassList("utk-date-picker__nav-btn--prev-year");

            _prevMonthButton = CreateNavButton("prev-month", "\u2039"); // <

            leftNav.Add(_prevYearButton);
            leftNav.Add(_prevMonthButton);

            _yearMonthLabel = new Label { name = "year-month" };
            _yearMonthLabel.AddToClassList("utk-date-picker__year-month-label");

            var rightNav = new VisualElement();
            rightNav.AddToClassList("utk-date-picker__nav-group");

            _nextMonthButton = CreateNavButton("next-month", "\u203A"); // >

            _nextYearButton = CreateNavButton("next-year", "\u00BB");  // >>
            _nextYearButton.AddToClassList("utk-date-picker__nav-btn--next-year");

            rightNav.Add(_nextMonthButton);
            rightNav.Add(_nextYearButton);

            navRow.Add(leftNav);
            navRow.Add(_yearMonthLabel);
            navRow.Add(rightNav);
            Add(navRow);

            // Day names row
            _dayNamesRow = new VisualElement { name = "day-names" };
            _dayNamesRow.AddToClassList("utk-date-picker__day-names");

            for (int i = 0; i < DAY_NAME_KEYS.Length; i++)
            {
                var dayText = LocalizationManager.Instance.GetString(DAY_NAME_KEYS[i]);
                var label = new Label(dayText) { name = $"day-name-{i}" };
                label.AddToClassList("utk-date-picker__day-name");

                // 요일별 색상 클래스 (0=일요일, 6=토요일)
                if (i == 0) label.AddToClassList("utk-date-picker__day-name--sunday");
                else if (i == 6) label.AddToClassList("utk-date-picker__day-name--saturday");

                _dayNamesRow.Add(label);
            }
            Add(_dayNamesRow);

            // Calendar grid - 6 rows
            for (int row = 0; row < 6; row++)
            {
                var rowContainer = new VisualElement { name = $"calendar-row-{row}" };
                rowContainer.AddToClassList("utk-date-picker__calendar-row");

                for (int col = 0; col < 7; col++)
                {
                    var dayButton = new Button { name = $"day-{row * 7 + col}" };
                    dayButton.AddToClassList("utk-date-picker__day-btn");

                    int index = row * 7 + col;
                    dayButton.clicked += () => OnDayClicked(index);

                    _dayButtons.Add(dayButton);
                    rowContainer.Add(dayButton);
                }
                Add(rowContainer);
            }

            // Time row (optional)
            _timeRow = new VisualElement { name = "time-row" };
            _timeRow.AddToClassList("utk-date-picker__time-row");

            var timeLabel = new Label("시간:");
            timeLabel.AddToClassList("utk-date-picker__time-label");

            _hourStepper = new UTKNumberStepper(0, 23, 0, 1) { name = "hour-stepper" };
            _hourStepper.AddToClassList("utk-date-picker__time-stepper");
            _hourStepper.WrapAround = true;

            var colonLabel = new Label(":");
            colonLabel.AddToClassList("utk-date-picker__time-separator");

            _minuteStepper = new UTKNumberStepper(0, 59, 0, 1) { name = "minute-stepper" };
            _minuteStepper.AddToClassList("utk-date-picker__time-stepper");
            _minuteStepper.WrapAround = true;

            // Tab 키로 시간 <-> 분 이동
            _hourStepper.OnTabPressed += () => _minuteStepper?.Focus();
            _minuteStepper.OnShiftTabPressed += () => _hourStepper?.Focus();

            _timeRow.Add(timeLabel);
            _timeRow.Add(_hourStepper);
            _timeRow.Add(colonLabel);
            _timeRow.Add(_minuteStepper);
            Add(_timeRow);

            // Buttons
            var buttonRow = new VisualElement { name = "button-row" };
            buttonRow.AddToClassList("utk-date-picker__button-row");

            _cancelButton = new Button { name = "cancel-btn", text = "Cancel" };
            _cancelButton.AddToClassList("utk-date-picker__cancel-btn");

            _confirmButton = new Button { name = "confirm-btn", text = "OK" };
            _confirmButton.AddToClassList("utk-date-picker__confirm-btn");

            buttonRow.Add(_cancelButton);
            buttonRow.Add(_confirmButton);
            Add(buttonRow);
        }

        private Button CreateNavButton(string name, string text)
        {
            var btn = new Button { name = name, text = text };
            btn.AddToClassList("utk-date-picker__nav-btn");
            return btn;
        }

        private void QueryElements()
        {
            _titleLabel ??= this.Q<Label>("title");
            _closeButton ??= this.Q<Button>("close-btn");
            _yearMonthLabel ??= this.Q<Label>("year-month");
            _prevYearButton ??= this.Q<Button>("prev-year");
            _prevMonthButton ??= this.Q<Button>("prev-month");
            _nextMonthButton ??= this.Q<Button>("next-month");
            _nextYearButton ??= this.Q<Button>("next-year");
            _dayNamesRow ??= this.Q<VisualElement>("day-names");
            _timeRow ??= this.Q<VisualElement>("time-row");
            _hourStepper ??= this.Q<UTKNumberStepper>("hour-stepper");
            _minuteStepper ??= this.Q<UTKNumberStepper>("minute-stepper");
            _cancelButton ??= this.Q<Button>("cancel-btn");
            _confirmButton ??= this.Q<Button>("confirm-btn");

            // Day buttons 쿼리
            if (_dayButtons.Count == 0)
            {
                for (int i = 0; i < DAYS_IN_GRID; i++)
                {
                    var btn = this.Q<Button>($"day-{i}");
                    if (btn != null)
                    {
                        _dayButtons.Add(btn);
                        int index = i;
                        btn.clicked += () => OnDayClicked(index);
                    }
                }
            }
        }

        private void SetupEvents()
        {
            _closeButton?.RegisterCallback<ClickEvent>(_ => Close());
            _cancelButton?.RegisterCallback<ClickEvent>(_ => Close());
            _confirmButton?.RegisterCallback<ClickEvent>(_ => Confirm());

            _prevYearButton?.RegisterCallback<ClickEvent>(_ => PreviousYear());
            _prevMonthButton?.RegisterCallback<ClickEvent>(_ => PreviousMonth());
            _nextMonthButton?.RegisterCallback<ClickEvent>(_ => NextMonth());
            _nextYearButton?.RegisterCallback<ClickEvent>(_ => NextYear());

            // 언어 변경 이벤트 구독
            LocalizationManager.Instance.OnLanguageChanged += OnLanguageChanged;
        }

        private void OnLanguageChanged(string newLanguage)
        {
            UpdateDayNameLabels();
        }

        private void UpdateDayNameLabels()
        {
            if (_dayNamesRow == null) return;

            for (int i = 0; i < DAY_NAME_KEYS.Length; i++)
            {
                var label = _dayNamesRow.Q<Label>($"day-name-{i}");
                if (label != null)
                {
                    label.text = LocalizationManager.Instance.GetString(DAY_NAME_KEYS[i]);
                }
            }
        }
        #endregion

        #region Private Methods - Logic
        private void NavigateMonth(int months)
        {
            _displayMonth = _displayMonth.AddMonths(months);
            UpdateCalendar();
        }

        private void UpdateCalendar()
        {
            if (_yearMonthLabel != null)
            {
                _yearMonthLabel.text = $"{_displayMonth.Year}년 {_displayMonth.Month:D2}월";
            }

            // 첫째 날의 요일
            DateTime firstDay = new DateTime(_displayMonth.Year, _displayMonth.Month, 1);
            int startDayOfWeek = (int)firstDay.DayOfWeek; // 0=Sunday

            // 해당 월의 일 수
            int daysInMonth = DateTime.DaysInMonth(_displayMonth.Year, _displayMonth.Month);

            DateTime today = DateTime.Today;

            for (int i = 0; i < DAYS_IN_GRID; i++)
            {
                var btn = _dayButtons[i];

                // 동적 클래스 초기화
                btn.RemoveFromClassList("utk-date-picker__day-btn--sunday");
                btn.RemoveFromClassList("utk-date-picker__day-btn--saturday");
                btn.RemoveFromClassList("utk-date-picker__day-btn--today");
                btn.RemoveFromClassList("utk-date-picker__day-btn--selected");
                btn.RemoveFromClassList("utk-date-picker__day-btn--other-month");

                int dayNumber = i - startDayOfWeek + 1;

                if (dayNumber < 1 || dayNumber > daysInMonth)
                {
                    // 이번 달이 아닌 날
                    btn.text = "";
                    btn.SetEnabled(false);
                    btn.AddToClassList("utk-date-picker__day-btn--other-month");
                }
                else
                {
                    btn.text = dayNumber.ToString();
                    btn.SetEnabled(true);

                    DateTime currentDate = new DateTime(_displayMonth.Year, _displayMonth.Month, dayNumber);
                    DayOfWeek dow = currentDate.DayOfWeek;

                    // 선택된 날짜인지 확인
                    bool isSelected = currentDate.Date == _selectedDate.Date;

                    // 오늘인지 확인
                    bool isToday = currentDate.Date == today;

                    // 선택 상태 클래스
                    if (isSelected)
                    {
                        btn.AddToClassList("utk-date-picker__day-btn--selected");
                    }

                    // 오늘 클래스 (선택되지 않은 경우에만)
                    if (isToday && !isSelected)
                    {
                        btn.AddToClassList("utk-date-picker__day-btn--today");
                    }

                    // 요일별 클래스 (선택되지 않은 경우에만)
                    if (!isSelected)
                    {
                        if (dow == DayOfWeek.Sunday)
                        {
                            btn.AddToClassList("utk-date-picker__day-btn--sunday");
                        }
                        else if (dow == DayOfWeek.Saturday)
                        {
                            btn.AddToClassList("utk-date-picker__day-btn--saturday");
                        }
                    }
                }
            }
        }

        private void OnDayClicked(int index)
        {
            // 첫째 날의 요일
            DateTime firstDay = new DateTime(_displayMonth.Year, _displayMonth.Month, 1);
            int startDayOfWeek = (int)firstDay.DayOfWeek;

            int dayNumber = index - startDayOfWeek + 1;
            int daysInMonth = DateTime.DaysInMonth(_displayMonth.Year, _displayMonth.Month);

            if (dayNumber >= 1 && dayNumber <= daysInMonth)
            {
                // 시간 유지
                int hour = _hourStepper?.Value ?? _selectedDate.Hour;
                int minute = _minuteStepper?.Value ?? _selectedDate.Minute;

                _selectedDate = new DateTime(
                    _displayMonth.Year,
                    _displayMonth.Month,
                    dayNumber,
                    hour,
                    minute,
                    0
                );

                UpdateCalendar();
            }
        }

        private void Confirm()
        {
            OnDateSelected?.Invoke(GetDate());
            Close();
        }

        private void SetTitle(string title)
        {
            if (_titleLabel != null)
                _titleLabel.text = title;
        }

        private void SetTimeVisible(bool visible)
        {
            if (_timeRow != null)
                _timeRow.style.display = visible ? DisplayStyle.Flex : DisplayStyle.None;
        }

        private void UpdateTimeFields()
        {
            if (_hourStepper != null)
                _hourStepper.SetValue(_selectedDate.Hour, notify: false);

            if (_minuteStepper != null)
                _minuteStepper.SetValue(_selectedDate.Minute, notify: false);
        }

        private void CenterOnScreen()
        {
            schedule.Execute(() =>
            {
                var parent = this.parent;
                if (parent == null) return;

                float parentWidth = parent.resolvedStyle.width;
                float parentHeight = parent.resolvedStyle.height;
                float selfWidth = resolvedStyle.width;
                float selfHeight = resolvedStyle.height;

                style.left = (parentWidth - selfWidth) / 2;
                style.top = (parentHeight - selfHeight) / 2;
            });
        }
        #endregion

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

            // 언어 변경 이벤트 구독 해제
            LocalizationManager.Instance.OnLanguageChanged -= OnLanguageChanged;

            _dayButtons.Clear();

            OnDateSelected = null;
            OnClosed = null;

            _blocker = null;
        }
        #endregion
    }
}