#nullable disable
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Linq;
using Microsoft.Maui.Controls.Internals;
 
namespace Microsoft.Maui.Controls
{
	/// <include file="../../docs/Microsoft.Maui.Controls/GestureElement.xml" path="Type[@FullName='Microsoft.Maui.Controls.GestureElement']/Docs/*" />
	public class GestureElement : Element, ISpatialElement, IGestureRecognizers
	{
		readonly GestureRecognizerCollection _gestureRecognizers = new GestureRecognizerCollection();
		internal event NotifyCollectionChangedEventHandler GestureRecognizersCollectionChanged;
 
		/// <include file="../../docs/Microsoft.Maui.Controls/GestureElement.xml" path="//Member[@MemberName='.ctor']/Docs/*" />
		public GestureElement()
		{
			_gestureRecognizers.CollectionChanged += (sender, args) =>
			{
				void AddItems()
				{
					foreach (IElementDefinition item in args.NewItems.OfType<IElementDefinition>())
					{
						ValidateGesture(item as IGestureRecognizer);
						item.Parent = this;
					}
				}
 
				void RemoveItems()
				{
					foreach (IElementDefinition item in args.OldItems.OfType<IElementDefinition>())
						item.Parent = null;
				}
 
				switch (args.Action)
				{
					case NotifyCollectionChangedAction.Add:
						AddItems();
						break;
					case NotifyCollectionChangedAction.Remove:
						RemoveItems();
						break;
					case NotifyCollectionChangedAction.Replace:
						AddItems();
						RemoveItems();
						break;
					case NotifyCollectionChangedAction.Reset:
						foreach (IElementDefinition item in _gestureRecognizers.OfType<IElementDefinition>())
							item.Parent = this;
						break;
				}
 
				GestureRecognizersCollectionChanged?.Invoke(sender, args);
			};
		}
 
		Region ISpatialElement.Region { get; set; }
 
		/// <include file="../../docs/Microsoft.Maui.Controls/GestureElement.xml" path="//Member[@MemberName='GestureRecognizers']/Docs/*" />
		public IList<IGestureRecognizer> GestureRecognizers
		{
			get { return _gestureRecognizers; }
		}
 
		internal virtual void ValidateGesture(IGestureRecognizer gesture) { }
 
		class GestureRecognizerCollection : ObservableCollection<IGestureRecognizer>
		{
			protected override void ClearItems()
			{
				List<IGestureRecognizer> removed = new List<IGestureRecognizer>(this);
				base.ClearItems();
				base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, removed));
			}
		}
	}
}