[Mac] Improve search/arrange

This does a number of things:

 - We now auto-expand categories when searching
 - We now remember & restore open categories from searching and switching arrange
modes.
 - Order & Grouping are now cached rather than running every cell.
 - Order & Grouping are now a view on the existing list of properties, using the
same view models.

1 files changed, 56 insertions, 10 deletions

diff --git a/Xamarin.PropertyEditing.Mac/PropertyTableDataSource.cs b/Xamarin.PropertyEditing.Mac/PropertyTableDataSource.cs
index 8b01f2c..f46220b 100644
--- a/Xamarin.PropertyEditing.Mac/PropertyTableDataSource.cs
+++ b/Xamarin.PropertyEditing.Mac/PropertyTableDataSource.cs
@@ -3,34 +3,80 @@ using System.Collections.Generic;
 using System.Linq;
 using AppKit;
 using Foundation;
-using Xamarin.PropertyEditing.Mac.ViewModels;
 using Xamarin.PropertyEditing.ViewModels;
 
 namespace Xamarin.PropertyEditing.Mac
 {
-	public class PropertyTableDataSource : NSOutlineViewDataSource
+	internal class PropertyTableDataSource
+		: NSOutlineViewDataSource
 	{
-		internal MacPanelViewModel ViewModel { get; private set; }
-		public ICollection<object> SelectedItems => ViewModel.SelectedObjects;
-
-		internal PropertyTableDataSource (MacPanelViewModel viewModel)
+		internal PropertyTableDataSource (PanelViewModel panelVm)
 		{
-			ViewModel = viewModel;
+			if (panelVm == null)
+				throw new ArgumentNullException (nameof (panelVm));
+
+			this.vm = panelVm;
 		}
 
+		public PanelViewModel DataContext => this.vm;
+
 		public override nint GetChildrenCount (NSOutlineView outlineView, NSObject item)
 		{
-			return ViewModel.GetChildrenCount (item);
+			if (this.vm.ArrangedProperties.Count == 0)
+				return 0;
+
+			if (this.vm.ArrangeMode == PropertyArrangeMode.Name)
+				return this.vm.ArrangedProperties[0].Count;
+
+			if (item == null)
+				return this.vm.ArrangedProperties.Count;
+			else
+				return ((IGroupingList<string, PropertyViewModel>)((NSObjectFacade)item).Target).Count;
 		}
 
 		public override NSObject GetChild (NSOutlineView outlineView, nint childIndex, NSObject item)
 		{
-			return ViewModel.GetChildObject ((int)childIndex, item);
+			object element;
+			if (this.vm.ArrangeMode == PropertyArrangeMode.Name) {
+				element = (this.vm.ArrangedProperties[0][(int)childIndex]);
+			} else {
+				if (item == null)
+					element = this.vm.ArrangedProperties[(int)childIndex];
+				else {
+					element = ((IGroupingList<string, PropertyViewModel>)((NSObjectFacade)item).Target)[(int)childIndex];
+				}
+			}
+
+			return GetFacade (element);
 		}
 
 		public override bool ItemExpandable (NSOutlineView outlineView, NSObject item)
 		{
-			return ViewModel.ItemExpandable (item);
+			if (this.vm.ArrangeMode == PropertyArrangeMode.Name)
+				return false;
+
+			return ((NSObjectFacade)item).Target is IGroupingList<string, PropertyViewModel>;
 		}
+
+		public NSObject GetFacade (object element)
+		{
+			NSObject facade;
+			if (element is IGrouping<string, PropertyViewModel>) {
+				if (!this.groupFacades.TryGetValue (element, out facade)) {
+					this.groupFacades[element] = facade = new NSObjectFacade (element);
+				}
+			} else
+				facade = new NSObjectFacade (element);
+
+			return facade;
+		}
+
+		public bool TryGetFacade (object element, out NSObject facade)
+		{
+			return this.groupFacades.TryGetValue (element, out facade);
+		}
+
+		private readonly PanelViewModel vm;
+		private readonly Dictionary<object, NSObject> groupFacades = new Dictionary<object, NSObject> ();
 	}
 }