using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Threading;

namespace OrderSupportTicket.Behaviors;

/// <summary>
/// 仅承载视图交互：列表点击命令、消息列表滚动到底部。
/// </summary>
public static class ListBoxInteractionBehavior
{
    public static readonly DependencyProperty SelectedItemCommandProperty =
        DependencyProperty.RegisterAttached(
            "SelectedItemCommand",
            typeof(ICommand),
            typeof(ListBoxInteractionBehavior),
            new PropertyMetadata(null, OnSelectedItemCommandChanged));

    public static readonly DependencyProperty ScrollVersionProperty =
        DependencyProperty.RegisterAttached(
            "ScrollVersion",
            typeof(int),
            typeof(ListBoxInteractionBehavior),
            new PropertyMetadata(0, OnScrollVersionChanged));

    public static void SetSelectedItemCommand(DependencyObject element, ICommand value)
    {
        element.SetValue(SelectedItemCommandProperty, value);
    }

    public static ICommand GetSelectedItemCommand(DependencyObject element)
    {
        return (ICommand)element.GetValue(SelectedItemCommandProperty);
    }

    public static void SetScrollVersion(DependencyObject element, int value)
    {
        element.SetValue(ScrollVersionProperty, value);
    }

    public static int GetScrollVersion(DependencyObject element)
    {
        return (int)element.GetValue(ScrollVersionProperty);
    }

    private static void OnSelectedItemCommandChanged(
        DependencyObject d,
        DependencyPropertyChangedEventArgs e)
    {
        if (!(d is ListBox listBox))
            return;

        listBox.PreviewMouseLeftButtonUp -= OnPreviewMouseLeftButtonUp;
        listBox.PreviewKeyUp -= OnPreviewKeyUp;
        if (e.NewValue is ICommand)
        {
            listBox.PreviewMouseLeftButtonUp += OnPreviewMouseLeftButtonUp;
            listBox.PreviewKeyUp += OnPreviewKeyUp;
        }
    }

    private static void OnPreviewMouseLeftButtonUp(
        object sender,
        MouseButtonEventArgs e)
    {
        ExecuteForSelectedItem(sender as ListBox);
    }

    private static void OnPreviewKeyUp(object sender, KeyEventArgs e)
    {
        if (e.Key != Key.Enter && e.Key != Key.Space)
            return;
        ExecuteForSelectedItem(sender as ListBox);
    }

    private static void ExecuteForSelectedItem(ListBox listBox)
    {
        if (listBox == null || listBox.SelectedItem == null)
            return;
        var command = GetSelectedItemCommand(listBox);
        if (command != null && command.CanExecute(listBox.SelectedItem))
            command.Execute(listBox.SelectedItem);
    }

    private static void OnScrollVersionChanged(
        DependencyObject d,
        DependencyPropertyChangedEventArgs e)
    {
        if (!(d is ListBox listBox))
            return;

        listBox.Dispatcher.BeginInvoke(
            new Action(() =>
            {
                var scrollViewer = FindVisualChild<ScrollViewer>(listBox);
                if (scrollViewer != null)
                    scrollViewer.ScrollToEnd();
            }),
            DispatcherPriority.Background);
    }

    private static T FindVisualChild<T>(DependencyObject parent)
        where T : DependencyObject
    {
        if (parent == null)
            return null;
        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
        {
            var child = VisualTreeHelper.GetChild(parent, i);
            if (child is T match)
                return match;
            var nested = FindVisualChild<T>(child);
            if (nested != null)
                return nested;
        }
        return null;
    }
}