using System.Collections.Specialized;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Threading;

namespace Main.Test;

/// <summary>带默认样式、行号和行选择勾选框的 DataGrid。</summary>
public class StyledDataGrid : DataGrid
{
    public static readonly RoutedUICommand ToggleSelectAllCommand = new("全选或取消全选", nameof(ToggleSelectAllCommand), typeof(StyledDataGrid));
    private static readonly DependencyPropertyKey AreAllRowsSelectedPropertyKey = DependencyProperty.RegisterReadOnly(
        nameof(AreAllRowsSelected), typeof(bool?), typeof(StyledDataGrid), new PropertyMetadata(false));
    public static readonly DependencyProperty AreAllRowsSelectedProperty = AreAllRowsSelectedPropertyKey.DependencyProperty;
    /// <summary>全部选中为 true，部分选中为 null，未选中为 false。</summary>
    public bool? AreAllRowsSelected => (bool?)GetValue(AreAllRowsSelectedProperty);
    public static readonly DependencyProperty SelectedRowBackgroundProperty = DependencyProperty.Register(
        nameof(SelectedRowBackground), typeof(Brush), typeof(StyledDataGrid),
        new PropertyMetadata(new SolidColorBrush(Color.FromRgb(75, 178, 255))));
    public static readonly DependencyProperty SelectedRowForegroundProperty = DependencyProperty.Register(
        nameof(SelectedRowForeground), typeof(Brush), typeof(StyledDataGrid), new PropertyMetadata(Brushes.White));
    public static readonly DependencyProperty ShowCheckBoxProperty = DependencyProperty.Register(
        nameof(ShowCheckBox), typeof(bool), typeof(StyledDataGrid), new PropertyMetadata(false, HeaderOptionsChanged));
    public static readonly DependencyProperty ShowRowNumberProperty = DependencyProperty.Register(
        nameof(ShowRowNumber), typeof(bool), typeof(StyledDataGrid), new PropertyMetadata(false, HeaderOptionsChanged));

    public Brush SelectedRowBackground { get => (Brush)GetValue(SelectedRowBackgroundProperty); set => SetValue(SelectedRowBackgroundProperty, value); }
    public Brush SelectedRowForeground { get => (Brush)GetValue(SelectedRowForegroundProperty); set => SetValue(SelectedRowForegroundProperty, value); }
    /// <summary>勾选状态与行 IsSelected 同步，可通过 SelectedItems 获取。</summary>
    public bool ShowCheckBox { get => (bool)GetValue(ShowCheckBoxProperty); set => SetValue(ShowCheckBoxProperty, value); }
    public bool ShowRowNumber { get => (bool)GetValue(ShowRowNumberProperty); set => SetValue(ShowRowNumberProperty, value); }

    static StyledDataGrid()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(StyledDataGrid), new FrameworkPropertyMetadata(typeof(StyledDataGrid)));
    }

    public StyledDataGrid()
    {
        CommandBindings.Add(new CommandBinding(ToggleSelectAllCommand, (_, e) =>
        {
            if (AreAllRowsSelected == true) UnselectAll();
            else SelectAll();
            e.Handled = true;
        }, (_, e) =>
        {
            e.CanExecute = SelectionMode == DataGridSelectionMode.Extended &&
                SelectionUnit != DataGridSelectionUnit.Cell && SelectableItemCount > 0;
            e.Handled = true;
        }));
        LoadingRow += (_, e) => UpdateRowNumber(e.Row);
        ItemContainerGenerator.ItemsChanged += (_, _) => QueueHeaderUpdate();
        Loaded += (_, _) => QueueHeaderUpdate();
    }

    private static void HeaderOptionsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        => ((StyledDataGrid)d).QueueHeaderUpdate();

    protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
    {
        base.OnItemsChanged(e);
        QueueHeaderUpdate();
        UpdateSelectAllState();
    }

    private int SelectableItemCount => Items.Count - (Items.Contains(System.Windows.Data.CollectionView.NewItemPlaceholder) ? 1 : 0);

    protected override void OnSelectionChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectionChanged(e);
        UpdateSelectAllState();
    }

    private void UpdateSelectAllState()
    {
        SetValue(AreAllRowsSelectedPropertyKey, SelectedItems.Count == 0 ? false :
            SelectedItems.Count == SelectableItemCount ? true : (bool?)null);
        CommandManager.InvalidateRequerySuggested();
    }

    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        base.OnPropertyChanged(e);
        if (e.Property == FontSizeProperty || e.Property == FontFamilyProperty ||
            e.Property == FontStyleProperty || e.Property == FontWeightProperty || e.Property == FontStretchProperty)
            QueueHeaderUpdate();
    }

    private bool headerUpdatePending;
    private void QueueHeaderUpdate()
    {
        if (headerUpdatePending) return;
        headerUpdatePending = true;
        Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() =>
        {
            headerUpdatePending = false;
            // 使用最宽数字估算所有行号，避免虚拟化滚动时行头宽度跳变。
            var digits = Math.Max(1, Items.Count.ToString(CultureInfo.InvariantCulture).Length);
            var numberWidth = 0d;
            if (ShowRowNumber)
                for (var digit = '0'; digit <= '9'; digit++)
                {
                    var text = new FormattedText(new string(digit, digits), CultureInfo.CurrentCulture,
                        FlowDirection, new Typeface(FontFamily, FontStyle, FontWeight, FontStretch),
                        FontSize, Foreground ?? Brushes.Black, VisualTreeHelper.GetDpi(this).PixelsPerDip);
                    numberWidth = Math.Max(numberWidth, Math.Ceiling(text.WidthIncludingTrailingWhitespace) + 16);
                }
            SetCurrentValue(RowHeaderWidthProperty, numberWidth + (ShowCheckBox ? 32 : 0) +
                (ShowRowNumber && ShowCheckBox ? 1 : 0) + (ShowRowNumber || ShowCheckBox ? 1 : 0));
            foreach (var row in GetRealizedRows(this)) UpdateRowNumber(row);
        }));
    }

    private void UpdateRowNumber(DataGridRow row)
        => row.SetCurrentValue(DataGridRow.HeaderProperty, ShowRowNumber ? (row.GetIndex() + 1).ToString(CultureInfo.CurrentCulture) : null);

    private IEnumerable<DataGridRow> GetRealizedRows(DependencyObject parent)
    {
        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
        {
            var child = VisualTreeHelper.GetChild(parent, i);
            if (child is DataGridRow row && ItemsControl.ItemsControlFromItemContainer(row) == this) yield return row;
            else if (child is not DataGrid)
                foreach (var descendant in GetRealizedRows(child)) yield return descendant;
        }
    }
}