using System;
using System.Collections.Generic;
using Xamarin.Forms.CustomAttributes;
using Xamarin.Forms.Internals;


#if UITEST
using Xamarin.Forms.Core.UITests;
using Xamarin.UITest;
using NUnit.Framework;
#endif

namespace Xamarin.Forms.Controls.Issues
{

#if UITEST
	[Category(UITestCategories.CollectionView)]
#endif

	[Preserve(AllMembers = true)]
	[Issue(IssueTracker.Github, 8647, "Crash on iOS when using DataTemplateSelector as a GroupingHeaderTemplate in a CollectionView", PlatformAffected.iOS)]
	public class Issue8647 : TestContentPage
	{
		const string ButtonId = "ButtonId";
		CollectionView _view;

		protected override void Init()
		{
			var layout = new StackLayout { Margin = 50 };
			layout.Children.Add(new Button { HorizontalOptions = LayoutOptions.Center, Text = "Fill Data", AutomationId = ButtonId, Command = new Command(_ => FillData()) });
			_view = new CollectionView
			{
				IsGrouped = true,
				GroupHeaderTemplate = new DummySelector(),
				ItemTemplate = new DataTemplate(() =>
				{
					var item = new Label();
					item.SetBinding(Label.TextProperty, nameof(Item.Value));
					return item;
				})
			};
			layout.Children.Add(_view);
			Content = layout;
		}

		void FillData()
		{
			if (_view.ItemsSource == null)
			{
				_view.ItemsSource = new List<List<Item>>
				{
					new List<Item> { "1", "2", "3" },
					new List<Item> { "4", "5" }
				};
			}
		}

		class DummySelector : DataTemplateSelector
		{
			protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
			{

				return new DataTemplate(() => new Label { Text = "GroupHeader" });
			}
		}

		class Item
		{
			public string Value { get; set; }

			public static implicit operator Item(string value) => new Item { Value = value };
		}
	}
}