port from perforce

intromat/NodeNetworkToolkit/BreadcrumbBar/BreadcrumbBarViewModel.cs

@@ -0,0 +1,76 @@
+using System.Linq;
+using System.Reactive;
+using System.Reactive.Linq;
+using DynamicData;
+using ReactiveUI;
+
+namespace NodeNetwork.Toolkit.BreadcrumbBar
+{
+    /// <summary>
+    /// Viewmodel for a single element of the BreadcrumbBar.
+    /// </summary>
+    public class BreadcrumbViewModel : ReactiveObject
+    {
+        #region Name
+        /// <summary>
+        /// Displayed name of the crumb.
+        /// </summary>
+        public string Name
+        {
+            get => _name;
+            set => this.RaiseAndSetIfChanged(ref _name, value);
+        }
+        private string _name = "";
+        #endregion
+    }
+
+    /// <summary>
+    /// ViewModel for the BreadcrumbBar.
+    /// This UI element displays a path as a list of path elements (crumbs), allowing navigation by selection of path elements.
+    /// </summary>
+    public class BreadcrumbBarViewModel : ReactiveObject
+    {
+        static BreadcrumbBarViewModel()
+        {
+            NNViewRegistrar.AddRegistration(() => new BreadcrumbBarView(), typeof(IViewFor<BreadcrumbBarViewModel>));
+        }
+
+        /// <summary>
+        /// The path that is currently displayed in the bar.
+        /// Add or remove elements to modify the path.
+        /// </summary>
+        public ISourceList<BreadcrumbViewModel> ActivePath { get; } = new SourceList<BreadcrumbViewModel>();
+
+        #region ActiveElement
+        /// <summary>
+        /// The deepest element of the currect path. (Last element of ActivePath)
+        /// </summary>
+        public BreadcrumbViewModel ActiveItem => _activeItem.Value;
+        private readonly ObservableAsPropertyHelper<BreadcrumbViewModel> _activeItem;
+        #endregion
+
+        /// <summary>
+        /// Navigate to the subpath represented by the selected crumb which is passed as a parameter.
+        /// Only this crumb and its ancestors are kept, the rest of the path is removed.
+        /// </summary>
+        public ReactiveCommand<BreadcrumbViewModel, Unit> SelectCrumb { get; }
+
+        public BreadcrumbBarViewModel()
+        {
+            SelectCrumb = ReactiveCommand.Create((BreadcrumbViewModel crumb) =>
+            {
+                ActivePath.Edit(l =>
+                {
+                    int index = l.IndexOf(crumb);
+                    for (int i = l.Count - 1; i > index; i--)
+                    {
+                        l.RemoveAt(i);
+                    }
+                });
+            });
+
+            ActivePath.Connect().Select(_ => ActivePath.Count > 0 ? ActivePath.Items.ElementAt(ActivePath.Count - 1) : null)
+                .ToProperty(this, vm => vm.ActiveItem, out _activeItem);
+        }
+    }
+}