using Microsoft.Xaml.Behaviors;
using SamplePre.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

namespace SamplePreSystem.UI.Behaviors
{
    public class TreeViewDragBehavior :Behavior<TreeView>
    {

        // 拖拽起始点（用于判断是否是有效拖拽）
        private Point _dragStartPoint;

        protected override void OnAttached()
        {

            //记录鼠标按下时的坐标
            AssociatedObject.PreviewMouseLeftButtonDown += AssociatedObject_PreviewMouseLeftButtonDown;

            //处理TreeView的鼠标移动事件，触发拖拽
            AssociatedObject.PreviewMouseMove += AssociatedObject_PreviewMouseMove;
        }

        /// <summary>
        /// 处理TreeView的鼠标移动事件，触发拖拽
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        /// <exception cref="NotImplementedException"></exception>
        private void AssociatedObject_PreviewMouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            // 获取当前鼠标位置
            Point currentPoint = e.GetPosition(null);
            // 计算鼠标移动的距离（过滤掉微小移动，避免误触发拖拽）
            Vector dragVector = _dragStartPoint - currentPoint;

            // 如果鼠标左键按下，且移动距离超过阈值（系统默认的拖拽阈值），则开始拖拽
            if (e.LeftButton == MouseButtonState.Pressed &&
                (Math.Abs(dragVector.X) > SystemParameters.MinimumHorizontalDragDistance ||
                 Math.Abs(dragVector.Y) > SystemParameters.MinimumVerticalDragDistance))
            {
                // 获取当前鼠标下的TreeViewItem
                var treeViewItem = FindVisualParent<TreeViewItem>(e.OriginalSource as DependencyObject);
                if (treeViewItem != null && treeViewItem.DataContext is TreeListItem dragItem)
                {
                    // 开始拖拽，设置拖拽数据和拖拽效果
                    DragDrop.DoDragDrop(treeViewItem, dragItem, DragDropEffects.Copy);
                }
            }
        }

        /// <summary>
        /// 查找可视化树中的父级控件（通用方法）
        /// </summary>
        private T FindVisualParent<T>(DependencyObject child) where T : DependencyObject
        {
            DependencyObject parentObject = VisualTreeHelper.GetParent(child);
            if (parentObject == null) return null;

            if (parentObject is T parent)
                return parent;
            else
                return FindVisualParent<T>(parentObject);
        }



        private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            // 记录鼠标按下时的坐标
            _dragStartPoint = e.GetPosition(null);
        }




    }
}