Implement passing test for ElementPickerViewModel.

zaaReloaded2/ViewModels/ElementPickerViewModel.cs

@@ -38,19 +38,65 @@ namespace zaaReloaded2.ViewModels
         /// <summary>
         /// A two-dimensional tree 
         /// </summary>
-        public IList<CategoryViewModel> AvailableElements { get; private set; }
+        public IList<CategoryViewModel> Categories { get; private set; }
+
+        /// <summary>
+        /// Gets the currently selected element, or null if no element is selected.
+        /// </summary>
+        /// <remarks>
+        /// TODO: Raise PropertyChanged event.
+        /// </remarks>
+        public ElementViewModel Selected { get; private set; }
+
+        #endregion
+
+        #region Commands
+
+        public DelegatingCommand ChooseElementCommand
+        {
+            get
+            {
+                if (_chooseElementCommand == null)
+                {
+                    _chooseElementCommand = new DelegatingCommand(
+                        param => DoChooseElement(),
+                        param => CanChooseElement());
+                }
+                return _chooseElementCommand;
+            }
+        }
+
+        #endregion
+
+        #region Messages
+
+        /// <summary>
+        /// A message that is sent out when an element has been chosen;
+        /// the message content is the element's view model with the element
+        /// wrapped inside.
+        /// </summary>
+        public Message<ViewModelMessageContent> ElementChosenMessage
+        {
+            get
+            {
+                if (_elementChosenMessage == null)
+                {
+                    _elementChosenMessage = new Message<ViewModelMessageContent>();
+                }
+                return _elementChosenMessage;
+            }
+        }
 
         #endregion
 
         #region Constructors
 
-        public ElementPickerViewModel(SettingsViewModel caller, bool allowControlElements)
+        public ElementPickerViewModel(bool allowControlElements)
         {
-            _caller = caller;
-            AvailableElements = new List<CategoryViewModel>();
+            Categories = new List<CategoryViewModel>();
             if (allowControlElements)
             {
-                AvailableElements.Add(
+                Categories.Add(
                     new CategoryViewModel(
                         "Kontroll-Elemente",
                         new Collection<ViewModelBase>()
@@ -62,7 +108,7 @@ namespace zaaReloaded2.ViewModels
                     )
                 );
             }
-            AvailableElements.Add(
+            Categories.Add(
                 new CategoryViewModel(
                     "Ausgabe-Elemente",
                     new Collection<ViewModelBase>()
@@ -87,6 +133,7 @@ namespace zaaReloaded2.ViewModels
         {
             ControlElementViewModel vm = new ControlElementViewModel(element);
             vm.DisplayString = element.Label;
+            vm.PropertyChanged += ElementViewModel_PropertyChanged;
             return vm;
         }
 
@@ -102,6 +149,31 @@ namespace zaaReloaded2.ViewModels
             return vm;
         }
 
+        void ElementViewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
+        {
+            if (e.PropertyName == "IsSelected")
+            {
+                // Casting sender as ElementViewModel may result in Null, but this
+                // is a desired effect because category headings may be selected
+                // in a view, but are not valid ElementViewModels that we could
+                // 'choose'.
+                Selected = sender as ElementViewModel;
+            }
+        }
+
+        void DoChooseElement()
+        {
+            if (CanChooseElement())
+            {
+                ElementChosenMessage.Send(new ViewModelMessageContent(Selected));
+            }
+        }
+
+        bool CanChooseElement()
+        {
+            return Selected != null;
+        }
+
         #endregion
 
         #region Implementation ov ViewModelBase
@@ -115,7 +187,8 @@ namespace zaaReloaded2.ViewModels
 
         #region Fields
 
-        SettingsViewModel _caller;
+        DelegatingCommand _chooseElementCommand;
+        Message<ViewModelMessageContent> _elementChosenMessage;
 
         #endregion
     }