using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace YY.Admin.Controls;

/// <summary>
/// 自定义日期时间选择器。
/// 弹出层布局：左侧 <see cref="Calendar"/> 日历 + 右侧时/分/秒 三列 <see cref="ListBox"/>，
/// 底部「此刻 / 确定」按钮，用于替代 HandyControl 默认的「圆盘表盘 + 上午下午」风格 DateTimePicker。
/// </summary>
public partial class DateTimeListPicker : UserControl
{
    public DateTimeListPicker()
    {
        InitializeComponent();
        Loaded += (_, _) => SyncDisplay();
    }

    #region 公共依赖属性

    /// <summary>选择的日期时间，双向绑定。</summary>
    public static readonly DependencyProperty SelectedDateTimeProperty =
        DependencyProperty.Register(
            nameof(SelectedDateTime), typeof(DateTime?), typeof(DateTimeListPicker),
            new FrameworkPropertyMetadata(
                null,
                FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
                OnSelectedDateTimeChanged));

    public DateTime? SelectedDateTime
    {
        get => (DateTime?)GetValue(SelectedDateTimeProperty);
        set => SetValue(SelectedDateTimeProperty, value);
    }

    /// <summary>占位符（空值时显示在 TextBox 上的提示文字）。</summary>
    public static readonly DependencyProperty PlaceholderProperty =
        DependencyProperty.Register(
            nameof(Placeholder), typeof(string), typeof(DateTimeListPicker),
            new PropertyMetadata("请选择日期时间"));

    public string Placeholder
    {
        get => (string)GetValue(PlaceholderProperty);
        set => SetValue(PlaceholderProperty, value);
    }

    /// <summary>显示格式，默认 yyyy-MM-dd HH:mm:ss。</summary>
    public static readonly DependencyProperty DateTimeFormatProperty =
        DependencyProperty.Register(
            nameof(DateTimeFormat), typeof(string), typeof(DateTimeListPicker),
            new PropertyMetadata("yyyy-MM-dd HH:mm:ss", OnDateTimeFormatChanged));

    public string DateTimeFormat
    {
        get => (string)GetValue(DateTimeFormatProperty);
        set => SetValue(DateTimeFormatProperty, value);
    }

    #endregion

    #region 内部依赖属性

    /// <summary>弹出层是否打开。</summary>
    public static readonly DependencyProperty IsDropDownOpenProperty =
        DependencyProperty.Register(
            nameof(IsDropDownOpen), typeof(bool), typeof(DateTimeListPicker),
            new PropertyMetadata(false, OnIsDropDownOpenChanged));

    public bool IsDropDownOpen
    {
        get => (bool)GetValue(IsDropDownOpenProperty);
        set => SetValue(IsDropDownOpenProperty, value);
    }

    /// <summary>TextBox 当前显示的文字。用户可手工编辑，回车/失焦时尝试解析。</summary>
    public static readonly DependencyProperty DisplayTextProperty =
        DependencyProperty.Register(
            nameof(DisplayText), typeof(string), typeof(DateTimeListPicker),
            new PropertyMetadata(string.Empty));

    public string DisplayText
    {
        get => (string)GetValue(DisplayTextProperty);
        set => SetValue(DisplayTextProperty, value);
    }

    /// <summary>弹出层内未确认的日期值。</summary>
    public static readonly DependencyProperty PendingDateProperty =
        DependencyProperty.Register(
            nameof(PendingDate), typeof(DateTime?), typeof(DateTimeListPicker),
            new PropertyMetadata(null));

    public DateTime? PendingDate
    {
        get => (DateTime?)GetValue(PendingDateProperty);
        set => SetValue(PendingDateProperty, value);
    }

    public static readonly DependencyProperty PendingHourProperty =
        DependencyProperty.Register(nameof(PendingHour), typeof(int), typeof(DateTimeListPicker), new PropertyMetadata(0));

    public int PendingHour
    {
        get => (int)GetValue(PendingHourProperty);
        set => SetValue(PendingHourProperty, value);
    }

    public static readonly DependencyProperty PendingMinuteProperty =
        DependencyProperty.Register(nameof(PendingMinute), typeof(int), typeof(DateTimeListPicker), new PropertyMetadata(0));

    public int PendingMinute
    {
        get => (int)GetValue(PendingMinuteProperty);
        set => SetValue(PendingMinuteProperty, value);
    }

    public static readonly DependencyProperty PendingSecondProperty =
        DependencyProperty.Register(nameof(PendingSecond), typeof(int), typeof(DateTimeListPicker), new PropertyMetadata(0));

    public int PendingSecond
    {
        get => (int)GetValue(PendingSecondProperty);
        set => SetValue(PendingSecondProperty, value);
    }

    #endregion

    // 注意：这三个集合必须用字段初始化器赋值，而不是放到构造函数体内。
    // 原因：XAML 中通过 {Binding Hours, ElementName=Root} 绑定到普通 CLR 只读属性，
    // 绑定在 InitializeComponent() 执行时就建立。若赋值滞后到构造函数体内，
    // 绑定第一次求值时 Hours 仍为 null，且不会再有变更通知，导致弹出层右侧三列为空。

    /// <summary>0-23 小时列表。</summary>
    public List<int> Hours { get; } = Enumerable.Range(0, 24).ToList();

    /// <summary>0-59 分钟列表。</summary>
    public List<int> Minutes { get; } = Enumerable.Range(0, 60).ToList();

    /// <summary>0-59 秒列表。</summary>
    public List<int> Seconds { get; } = Enumerable.Range(0, 60).ToList();

    private bool _suppressTextSync;

    private static void OnSelectedDateTimeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((DateTimeListPicker)d).SyncDisplay();
    }

    private static void OnDateTimeFormatChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((DateTimeListPicker)d).SyncDisplay();
    }

    private static void OnIsDropDownOpenChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var picker = (DateTimeListPicker)d;
        if ((bool)e.NewValue)
        {
            picker.SyncPendingFromSelected();
            picker.Dispatcher.BeginInvoke(new Action(picker.ScrollListBoxesToSelection),
                System.Windows.Threading.DispatcherPriority.Loaded);
        }
    }

    /// <summary>将 <see cref="SelectedDateTime"/> 同步到 TextBox 显示文本。</summary>
    private void SyncDisplay()
    {
        _suppressTextSync = true;
        try
        {
            DisplayText = SelectedDateTime.HasValue
                ? SelectedDateTime.Value.ToString(DateTimeFormat, CultureInfo.InvariantCulture)
                : string.Empty;
        }
        finally
        {
            _suppressTextSync = false;
        }
    }

    /// <summary>弹出层打开时，把当前选中值（或当前时间）拷贝到 Pending 字段。</summary>
    private void SyncPendingFromSelected()
    {
        var dt = SelectedDateTime ?? DateTime.Now;
        PendingDate = dt.Date;
        PendingHour = dt.Hour;
        PendingMinute = dt.Minute;
        PendingSecond = dt.Second;
    }

    /// <summary>将三列时间 ListBox 滚动到当前选中项。</summary>
    private void ScrollListBoxesToSelection()
    {
        PART_HourList?.ScrollIntoView(PendingHour);
        PART_MinuteList?.ScrollIntoView(PendingMinute);
        PART_SecondList?.ScrollIntoView(PendingSecond);
    }

    private void OnNowClick(object sender, RoutedEventArgs e)
    {
        var now = DateTime.Now;
        PendingDate = now.Date;
        PendingHour = now.Hour;
        PendingMinute = now.Minute;
        PendingSecond = now.Second;
        ScrollListBoxesToSelection();
    }

    private void OnConfirmClick(object sender, RoutedEventArgs e)
    {
        var date = PendingDate ?? DateTime.Today;
        SelectedDateTime = new DateTime(
            date.Year, date.Month, date.Day,
            ClampTime(PendingHour, 23),
            ClampTime(PendingMinute, 59),
            ClampTime(PendingSecond, 59));
        IsDropDownOpen = false;
    }

    private static int ClampTime(int value, int max)
    {
        if (value < 0) return 0;
        if (value > max) return max;
        return value;
    }

    private void OnTextBoxKeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            TryParseDisplayText();
            e.Handled = true;
        }
    }

    private void OnTextBoxLostFocus(object sender, RoutedEventArgs e)
    {
        TryParseDisplayText();
    }

    /// <summary>解析当前 TextBox 文本到 <see cref="SelectedDateTime"/>，失败则回滚显示。</summary>
    private void TryParseDisplayText()
    {
        if (_suppressTextSync) return;

        if (string.IsNullOrWhiteSpace(DisplayText))
        {
            SelectedDateTime = null;
            return;
        }

        if (DateTime.TryParseExact(DisplayText, DateTimeFormat, CultureInfo.InvariantCulture, DateTimeStyles.None, out var exact))
        {
            SelectedDateTime = exact;
        }
        else if (DateTime.TryParse(DisplayText, CultureInfo.CurrentCulture, DateTimeStyles.None, out var fallback))
        {
            SelectedDateTime = fallback;
        }
        else
        {
            // 输入非法，恢复为原值
            SyncDisplay();
        }
    }
}