fix: validate help module selections

Modules/HelpModule.cs

@@ -8,6 +8,7 @@
 using Morpheus.Extensions;
 using Morpheus.Handlers;
 using Morpheus.Utilities;
+using System.Globalization;
 using System.Reflection;
 
 namespace Morpheus.Modules;
@@ -57,13 +58,36 @@ private async Task HandleHelpSelectorInteraction(SocketInteraction interaction)
         }
     }
 
+    internal static bool TryParseHelpModuleName(string moduleName, out int page, out string moduleKey)
+    {
+        page = 0;
+        moduleKey = string.Empty;
+
+        int separatorIndex = moduleName.IndexOf('_');
+        if (separatorIndex <= 0 || separatorIndex == moduleName.Length - 1)
+            return false;
+
+        if (!int.TryParse(moduleName[..separatorIndex], NumberStyles.None, CultureInfo.InvariantCulture, out page) || page < 1)
+            return false;
+
+        moduleKey = moduleName[(separatorIndex + 1)..];
+        return moduleKey.IndexOf('_') < 0;
+    }
+
     private Embed CreateModuleHelpEmbed(string moduleName, string commandPrefix)
     {
         if (helpModules.TryGetValue(commandPrefix + moduleName, out Embed? embed))
             return embed;
 
-        int page = int.Parse(moduleName.Split("_")[0]);
-        string moduleKey = moduleName.Split("_")[1];
+        if (!TryParseHelpModuleName(moduleName, out int page, out string moduleKey))
+        {
+            return new EmbedBuilder()
+            {
+                Color = Colors.Blue,
+                Title = "Unable to load help",
+                Description = "The selected help page is invalid. Please run the help command again."
+            }.Build();
+        }
         string name = moduleKey.Replace("Module", "");
 
         EmbedBuilder builder = new()

Morpheus.Tests/HelpCommandRegistrationTests.cs

@@ -6,6 +6,27 @@ namespace Morpheus.Tests;
 
 public class HelpCommandRegistrationTests
 {
+    [Theory]
+    [InlineData("2_StocksModule", 2, "StocksModule")]
+    [InlineData("10_Misc", 10, "Misc")]
+    public void TryParseHelpModuleName_ParsesPageAndModule(string input, int expectedPage, string expectedModule)
+    {
+        Assert.True(HelpModule.TryParseHelpModuleName(input, out int page, out string module));
+        Assert.Equal(expectedPage, page);
+        Assert.Equal(expectedModule, module);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("invalid")]
+    [InlineData("0_StocksModule")]
+    [InlineData("-1_StocksModule")]
+    [InlineData("2_")]
+    public void TryParseHelpModuleName_RejectsMalformedSelections(string input)
+    {
+        Assert.False(HelpModule.TryParseHelpModuleName(input, out _, out _));
+    }
+
     [Fact]
     public void HelpCommand_AcceptsMultiWordCommandNames()
     {