Added methods to allow the implementation do extension casts

Let's say you have a server where the player can pick the menu driver,
the player types !menu, selects WASD instead of XYZ, there are a couple
ways direct casting could go wrong or be undesirable:

- Overselling capabilities:
  The underlying menu does not support the extension, but the switcher advertises it
- Underselling capabilities:
  The underlying menu supports the extension, but the switcher does not advertise it
- The switcher wants to hook into a specific extension (such as controlling priority)

Author: AshleighAdams

src/CSSUniversalMenuAPI/IMenu.cs

@@ -1,3 +1,5 @@
+using System.Diagnostics.CodeAnalysis;
+
 using CounterStrikeSharp.API.Core;
 
 namespace CSSUniversalMenuAPI;
@@ -50,4 +52,28 @@ void Exit()
 			current = current.Parent;
 		} while (current is not null);
 	}
+
+	/// <summary>
+	/// Attempt to get an extension for the current menu. <br/>
+	///
+	/// This is preferred over direct casting, as it allows menus to be wrapped,
+	/// and switching the implementation at runtime for a single player.
+	/// </summary>
+	/// <typeparam name="TExtension">The extension's type.</typeparam>
+	/// <param name="extension">The dynamic casted extension.</param>
+	/// <returns>If the extension is supported, returns <c>true</c>, otherwise <c>false</c>.</returns>
+	bool TryGetExtension<TExtension>([NotNullWhen(true)] out TExtension? extension)
+		where TExtension : class
+	{
+		if (this is TExtension ext)
+		{
+			extension = ext;
+			return true;
+		}
+		else
+		{
+			extension = null;
+			return false;
+		}
+	}
 }

src/CSSUniversalMenuAPI/IMenuItem.cs

@@ -1,3 +1,5 @@
+using System.Diagnostics.CodeAnalysis;
+
 using CounterStrikeSharp.API.Core;
 
 namespace CSSUniversalMenuAPI;
@@ -26,6 +28,30 @@ public interface IMenuItem
 	/// </summary>
 	event ItemSelectedAction? Selected;
 	object? Context { get; set; }
+
+	/// <summary>
+	/// Attempt to get an extension for the current menu. <br/>
+	///
+	/// This is preferred over direct casting, as it allows menus to be wrapped,
+	/// and switching the implementation at runtime for a single player.
+	/// </summary>
+	/// <typeparam name="TExtension">The extension's type.</typeparam>
+	/// <param name="extension">The dynamic casted extension.</param>
+	/// <returns>If the extension is supported, returns <c>true</c>, otherwise <c>false</c>.</returns>
+	bool TryGetExtension<TExtension>([NotNullWhen(true)] out TExtension? extension)
+		where TExtension : class
+	{
+		if (this is TExtension ext)
+		{
+			extension = ext;
+			return true;
+		}
+		else
+		{
+			extension = null;
+			return false;
+		}
+	}
 }
 
 public delegate void ItemSelectedAction(IMenuItem menuItem);

src/UniversalMenu.Compat.CSSharp/CSSharpCompatPlugin.cs

@@ -89,7 +89,7 @@ public static bool BaseMenu_Open(BasePlugin? plugin, CCSPlayerController player,
 		newMenu.PlayerCanClose = menu.ExitButton;
 
 		var useHtml = false;
-		if (newMenu is IHtmlSupportMenuExtension htmlMenu)
+		if (newMenu.TryGetExtension<IHtmlSupportMenuExtension>(out var htmlMenu))
 			htmlMenu.UseHtml = useHtml = true;
 
 		if (useHtml)

src/UniversalMenu.Compat.MenuManagerApi/MenuManagerTranslator.cs

@@ -134,11 +134,11 @@ public void Open(CCSPlayerController player)
 		menu.Title = Title;
 		menu.PlayerCanClose = true;// ExitButton;
 
-		bool usingHtml = false;
-		if (menu is IHtmlSupportMenuExtension htmlMenu)
+		var usingHtml = false;
+		if (menu.TryGetExtension<IHtmlSupportMenuExtension>(out var htmlMenu))
 			htmlMenu.UseHtml = usingHtml = true;
 
-		if (BackAction is not null && menu is INavigateBackMenuExtension backableMenu)
+		if (BackAction is not null && menu.TryGetExtension<INavigateBackMenuExtension>(out var backableMenu))
 			backableMenu.NavigateBack = (_) => BackAction.Invoke(player);
 
 		foreach (var option in MenuOptions)

tests/ProofOfConcepts/NumberKeysMenuAPI.cs

@@ -66,8 +66,6 @@ bool IMenuAPI.IsExtensionSupported(Type extension)
 	{
 		if (extension == typeof(IMenuPriorityExtension))
 			return true;
-		if (extension == typeof(IMenuItemSubtitleExtension))
-			return true;
 		return false;
 	}
 

tests/ProofOfConcepts/Program.Admin.cs

@@ -100,7 +100,7 @@ private static void CreateAndShowMenuInternal(this IMenuAPI api, CCSPlayerContro
 	{
 		var menu = api.CreateMenu(player);
 		menu.Title = items.Title;
-		if (menu is IMenuPriorityExtension priorityExtension)
+		if (menu.TryGetExtension<IMenuPriorityExtension>(out var priorityExtension))
 			priorityExtension.Priority = 100.0;
 		menu.CreateItemsInternal(api, items, donePlayers);
 		menu.Display();
@@ -109,7 +109,7 @@ private static void CreateAndShowMenuInternal(this IMenuAPI api, IMenu parent, M
 	{
 		var menu = api.CreateMenu(parent);
 		menu.Title = items.Title;
-		if (menu is IMenuPriorityExtension priorityExtension)
+		if (menu.TryGetExtension<IMenuPriorityExtension>(out var priorityExtension))
 			priorityExtension.Priority = 100.0;
 		menu.CreateItemsInternal(api, items, donePlayers);
 		menu.Display();

tests/ProofOfConcepts/WASDMenuAPI.cs

@@ -65,8 +65,6 @@ bool IMenuAPI.IsExtensionSupported(Type extension)
 	{
 		if (extension == typeof(IMenuPriorityExtension))
 			return true;
-		if (extension == typeof(IMenuItemSubtitleExtension))
-			return true;
 		return false;
 	}