using GongSolutions.Wpf.DragDrop;
using GongSolutions.Wpf.DragDrop.Utilities;
using System.Collections.Generic;
using System.ComponentModel;
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Markup;
using System.Linq;
using System.Collections;
using WPFProject.Models;

namespace WPFProject.Utils
{
    public class DdDropHandler : DefaultDropHandler
    {
        public bool CanConvert(IDropInfo dropInfo)
        {
            bool InterfaceFilter(Type t, object o) => (t.IsGenericType && t.GetGenericTypeDefinition() == typeof(IEnumerable<>));
            Type[] enumerableInterfaces = dropInfo.TargetCollection.GetType().FindInterfaces(InterfaceFilter, null);
            var enumerableTypes = from i in enumerableInterfaces
                                  select i.GetGenericArguments().Single();

            if (enumerableTypes.Any())
            {
                Type dataType = TypeUtilities.GetCommonBaseClass(ExtractData(dropInfo.Data));
                return dataType == typeof(FuncModel) && enumerableTypes.Any(t => t==typeof(Step));
            }

            return false;
        }

        public Step ConvertFunc2Step(FuncModel func) {
            return new Step
            {
                Name = func.Name
            };
        }



        public override void DragOver(IDropInfo dropInfo)
        {
            if (CanAcceptData(dropInfo))
            {
                base.DragOver(dropInfo);
            }
            else if (CanConvert(dropInfo))
            {
                // 固定Copy
                dropInfo.Effects = DragDropEffects.Copy;
                var isTreeViewItem = dropInfo.InsertPosition.HasFlag(RelativeInsertPosition.TargetItemCenter) && dropInfo.VisualTargetItem is TreeViewItem;
                dropInfo.DropTargetAdorner = isTreeViewItem ? DropTargetAdorners.Highlight : DropTargetAdorners.Insert;
            }
        }

        public override void Drop(IDropInfo dropInfo)
        {
            if (CanAcceptData(dropInfo))
            {
                base.Drop(dropInfo);
            }
            else if (CanConvert(dropInfo))
            {
                int insertIndex = GetInsertIndex(dropInfo);
                var destinationList = dropInfo.TargetCollection.TryGetList();
                var data = ExtractData(dropInfo.Data).OfType<object>().ToList();

                if (destinationList != null)
                {
                    var objects2Insert = new List<object>();

                    foreach (var o in data)
                    {
                        var obj2Insert = ConvertFunc2Step(o as FuncModel);

                        objects2Insert.Add(obj2Insert);

                        destinationList.Insert(insertIndex++, obj2Insert);
                        // 下方对象如果实现了 IDragItemSource 接口，会在这里调用 ItemDropped 方法，算是后置处理
                        if (obj2Insert is IDragItemSource dragItemSource)
                        {
                            dragItemSource.ItemDropped(dropInfo);
                        }
                    }

                    SelectDroppedItems(dropInfo, objects2Insert);
                }
            }
            
        }

    }
}