#nullable disable
using System;
using System.Collections.Generic;
using Foundation;
using Microsoft.Maui.Controls.Internals;
using ObjCRuntime;
using UIKit;
using static Microsoft.Maui.Controls.Compatibility.Platform.iOS.AccessibilityExtensions;
 
namespace Microsoft.Maui.Controls.Platform.Compatibility
{
	public class ShellTableViewSource : UITableViewSource
	{
		readonly IShellContext _context;
		readonly Action<Element> _onElementSelected;
		List<List<Element>> _groups;
		Dictionary<Element, UIContainerCell> _cells;
		IShellController ShellController => _context.Shell;
 
		public ShellTableViewSource(IShellContext context, Action<Element> onElementSelected)
		{
			_context = context;
			_onElementSelected = onElementSelected;
		}
 
		public event EventHandler<UIScrollView> ScrolledEvent;
 
		public List<List<Element>> Groups
		{
			get
			{
				if (_groups == null)
				{
					_groups = ShellController.GenerateFlyoutGrouping();
 
					if (_cells != null)
					{
						foreach (var cell in _cells.Values)
							cell.Disconnect(_context.Shell);
					}
 
					_cells = new Dictionary<Element, UIContainerCell>();
				}
 
				return _groups;
			}
		}
 
		protected virtual DataTemplate DefaultItemTemplate => null;
 
		protected virtual DataTemplate DefaultMenuItemTemplate => null;
 
		internal void ReSyncCache()
		{
			var newGroups = ((IShellController)_context.Shell).GenerateFlyoutGrouping();
 
			if (newGroups == _groups)
				return;
 
			_groups = newGroups;
			if (_cells == null)
			{
				_cells = new Dictionary<Element, UIContainerCell>();
				return;
			}
 
			var oldList = _cells;
			_cells = new Dictionary<Element, UIContainerCell>();
 
			foreach (var group in newGroups)
			{
				foreach (var element in group)
				{
					UIContainerCell result;
					if (oldList.TryGetValue(element, out result))
					{
						_cells.Add(element, result);
						oldList.Remove(element);
					}
				}
			}
 
			foreach (var cell in oldList.Values)
				cell.Disconnect(_context.Shell);
		}
 
 
		public void ClearCache()
		{
			var newGroups = ((IShellController)_context.Shell).GenerateFlyoutGrouping();
 
			if (newGroups != _groups)
			{
				_groups = newGroups;
				if (_cells != null)
				{
					foreach (var cell in _cells.Values)
						cell.Disconnect(_context.Shell);
				}
				_cells = new Dictionary<Element, UIContainerCell>();
			}
		}
 
		public override nfloat GetHeightForRow(UITableView tableView, NSIndexPath indexPath)
		{
			int section = indexPath.Section;
			int row = indexPath.Row;
			var context = Groups[section][row];
 
			if (!_cells.TryGetValue(context, out var view))
				return UITableView.AutomaticDimension;
 
			if (!view.View.IsVisible)
				return 0;
 
			nfloat defaultHeight = tableView.EstimatedRowHeight == -1 ? 0 : tableView.EstimatedRowHeight;
			nfloat height = -1;
 
			if (view.View.HeightRequest >= 0)
			{
				height = (float)view.View.HeightRequest;
				(view.View as IView).Measure(tableView.Bounds.Width, view.View.HeightRequest);
				(view.View.Handler as IPlatformViewHandler)
					.PlatformView.Frame = new CoreGraphics.CGRect(0, 0, tableView.Bounds.Width, view.View.HeightRequest);
 
			}
			else
			{
				var request = (view.View as IView).Measure(tableView.Bounds.Width, double.PositiveInfinity);
 
				if (request.Height > defaultHeight)
					height = (float)request.Height;
				else
					height = defaultHeight;
			}
 
			if (height == -1)
				height = defaultHeight;
 
			return height;
		}
 
		public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
		{
			int section = indexPath.Section;
			int row = indexPath.Row;
			var context = Groups[section][row];
 
			DataTemplate template = ShellController.GetFlyoutItemDataTemplate(context);
			if (context is IMenuItemController)
			{
				if (DefaultMenuItemTemplate != null && _context.Shell.MenuItemTemplate == template)
					template = DefaultMenuItemTemplate;
			}
			else
			{
				if (DefaultItemTemplate != null && _context.Shell.ItemTemplate == template)
					template = DefaultItemTemplate;
			}
 
			var cellId = ((IDataTemplateController)template.SelectDataTemplate(context, _context.Shell)).IdString;
 
			UIContainerCell cell;
			if (!_cells.TryGetValue(context, out cell))
			{
				var view = (View)template.CreateContent(context, _context.Shell);
				cell = new UIContainerCell(cellId, view, _context.Shell, context);
			}
			else
			{
				var view = _cells[context].View;
				cell.Disconnect(keepRenderer: true);
				cell = new UIContainerCell(cellId, view, _context.Shell, context);
			}
 
			cell.SetAccessibilityProperties(context);
 
			_cells[context] = cell;
			cell.TableView = tableView;
			cell.IndexPath = indexPath;
			cell.ViewMeasureInvalidated += OnViewMeasureInvalidated;
 
			return cell;
		}
 
		void OnViewMeasureInvalidated(UIContainerCell cell)
		{
			cell.ReloadRow();
		}
 
		public override nfloat GetHeightForFooter(UITableView tableView, nint section)
		{
			if (section < Groups.Count - 1)
				return 1;
 
			return 0;
		}
 
		public override UIView GetViewForFooter(UITableView tableView, nint section)
		{
			return new SeparatorView();
		}
 
		public override nint NumberOfSections(UITableView tableView)
		{
			return Groups.Count;
		}
 
		public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
		{
			int section = indexPath.Section;
			int row = indexPath.Row;
 
			var element = Groups[section][row];
			_onElementSelected(element);
		}
 
		public override nint RowsInSection(UITableView tableview, nint section)
		{
			return Groups[(int)section].Count;
		}
 
		public override void Scrolled(UIScrollView scrollView)
		{
			ScrolledEvent?.Invoke(this, scrollView);
		}
 
		public override void WillDisplay(UITableView tableView, UITableViewCell cell, NSIndexPath indexPath)
		{
			cell.BackgroundColor = UIColor.Clear;
		}
 
		class SeparatorView : UIView
		{
			UIView _line;
 
			public SeparatorView()
			{
				_line = new UIView
				{
					BackgroundColor = Microsoft.Maui.Platform.ColorExtensions.OpaqueSeparatorColor,
					TranslatesAutoresizingMaskIntoConstraints = true,
					Alpha = 0.2f
				};
 
				Add(_line);
			}
 
			public override void LayoutSubviews()
			{
				_line.Frame = new CoreGraphics.CGRect(15, 0, Frame.Width - 30, 1);
				base.LayoutSubviews();
			}
		}
	}
}