new startup process UI for Windows

windows/WinUI/PageSwitcher.xaml.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Data;
+using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+using System.Windows.Shapes;
+
+namespace WinUI
+{
+    /// <summary>
+    /// Interaction logic for PageSwitcher.xaml
+    /// </summary>
+    public partial class PageSwitcher : Window
+    {
+        public PageSwitcher()
+        {
+            InitializeComponent();
+            Switcher.pageSwitcher = this;
+
+            CentralAPI api = CentralAPI.Instance;
+
+            if (api.HasAccessToken())
+            {
+                Switcher.Switch(new OnboardProcess.CreateOrJoin());
+            }
+            else
+            {
+                Switcher.Switch(new OnboardProcess.RegisterOrLogIn());
+            }
+        }
+
+        public void Navigate(UserControl nextPage)
+        {
+            this.Content = nextPage;
+        }
+
+        public void Navigate(UserControl nextPage, object state)
+        {
+            this.Content = nextPage;
+            ISwitchable s = nextPage as ISwitchable;
+
+            if (s != null)
+                s.UtilizeState(state);
+            else
+                throw new ArgumentException("NextPage is not ISwitchable! "
+                  + nextPage.Name.ToString());
+        }
+    }
+}