CmdPal: Add support for commands with parameters

doc/devdocs/modules/cmdpal/command-pal-anatomy/command-palette-anatomy.md

@@ -60,7 +60,7 @@ A markdown page is a page inside of command palette that displays markdown conte
 
 ```csharp
  interface IMarkdownPage requires IPage {
-     String[] Bodies(); // TODO! should this be an IBody, so we can make it observable?
+     String[] Bodies(); 
      IDetails Details();
      IContextItem[] Commands { get; };
  }

doc/devdocs/modules/cmdpal/initial-sdk-spec/DraftB.cs

@@ -0,0 +1,121 @@
+
+class MyPrefixCommandProvider : ICommandProvider
+{
+    private PeopleDynamicListPage _peopleCommand; // com.contoso.people
+    private CommandsListPage _commandsCommand; // com.contoso.commands
+    private AddFileCommand _addFileCommand; // com.contoso.addFile
+
+    private PrefixSearchPage _prefixSearchPage;
+
+    public MyPrefixCommandProvider()
+    {
+        _prefixSearchPage = new PrefixSearchPage();
+
+        var tokenPickedHandler = _prefixSearchPage.HandleTokenPicked;
+
+        _peopleCommand = new PeopleDynamicListPage(tokenPickedHandler);
+        _commandsCommand = new CommandsListPage(tokenPickedHandler);
+        _addFileCommand = new AddFileCommand(tokenPickedHandler);
+    }
+
+    public ICommandItem[] GetTopLevelCommands()
+    {
+        return new ICommandItem[] { _prefixSearchPage };
+    }
+
+    public ICommand GetCommand(String id)
+    {
+        if (id == "com.contoso.people")
+        {
+            return _peopleCommand;
+        }
+        else if (id == "com.contoso.commands")
+        {
+            return _commandsCommand;
+        }
+        else if (id == "com.contoso.addFile")
+        {
+            return _addFileCommand;
+        }
+        return null;
+    }
+}
+
+class PrefixSearchPage : ListPage, IPrefixProvider
+{
+    public IDictionary<String, String> PrefixCommands => new Dictionary<String, String>
+    {
+        { "@", "com.contoso.people" },
+        { "/", "com.contoso.commands" },
+        { "+", "com.contoso.addFile" },
+    };
+
+    public event Windows.Foundation.TypedEventHandler<Object, ITokenPickedEventArgs> TokenAdded;
+
+    public PrefixSearchPage()
+    {
+        // Initialize the page...
+    }
+
+    public void SendQuery(ISearchUpdateArgs args)
+    {
+        // Handle the search update, possibly updating the list of items based on the new search text
+        var searchText = args.NewSearchText;
+        var properties = args.GetProperties();
+        var tokens = properties.TryLookup<object>("tokens") as ITokenPositions[];
+
+        // Here you could use these tokens to update the commands in our own search results
+        // Or just save them, and plumb them into the InvokableCommand the user eventually picks
+    }
+
+    public void HandleTokenPicked(object sender, ITokenPickedEventArgs args)
+    {
+        // Handle the token picked event, e.g., log it or update UI
+        var token = args.Token;
+        var text = token.DisplayText;
+        // Do something with the picked token
+    }
+
+    // Other ListPage members...
+}
+
+public class PeopleDynamicListPage : DynamicListPage
+{
+    private Windows.Foundation.TypedEventHandler<Object, ITokenPickedEventArgs> _tokenPicked;
+
+    public PeopleDynamicListPage(TypedEventHandler<Object, ITokenPickedEventArgs> onTokenPicked)
+    {
+        _tokenPicked = onTokenPicked;
+    }
+
+    public override IListItem[] GetItems()
+    {
+        // Return the list of people items
+        return new IListItem[]
+        {
+            new PersonSuggestionItem("Alice", _tokenPicked),
+            new PersonSuggestionItem("Bob", _tokenPicked),
+            new PersonSuggestionItem("Charlie", _tokenPicked)
+        };
+    }
+
+    // Other DynamicListPage members...
+}
+public class PersonSuggestionItem : SuggestionListItem { /* ... */ }
+public class SuggestionListItem : SuggestionListItem
+{
+    private Windows.Foundation.TypedEventHandler<Object, ITokenPickedEventArgs> _tokenPicked;
+    private object _tokenValue;
+
+    public SuggestionListItem(object token, TypedEventHandler<Object, ITokenPickedEventArgs> onTokenPicked)
+    {
+        _tokenValue = token;
+        _tokenPicked = onTokenPicked;
+    }
+
+    public override ICommandResult Invoke()
+    {
+        _tokenPicked?.Invoke(this, new TokenPickedEventArgs(_tokenValue));
+        return CommandResult.KeepOpen;
+    }
+}