Optimize highlight name fetching

QuickLook.Plugin/QuickLook.Plugin.TextViewer/Plugin.cs

@@ -176,17 +176,17 @@ public class Plugin : IViewer
             if (s == null)
                 continue;
 
+            Debug.WriteLine(resourceName);
+
             try
             {
-                Debug.WriteLine(resourceName);
-
                 var hlm = resourceName.Contains(".Syntax.Dark.") ? _hlmDark : _hlmLight;
-                var ext = Path.GetFileNameWithoutExtension(resourceName.ToResourceDummyName());
+                var name = EmbeddedResource.GetFileNameWithoutExtension(resourceName);
                 using var reader = new XmlTextReader(s);
                 var xshd = HighlightingLoader.LoadXshd(reader);
                 var highlightingDefinition = HighlightingLoader.Load(xshd, hlm);
                 if (xshd.Extensions.Count > 0)
-                    hlm.RegisterHighlighting(ext, [.. xshd.Extensions], highlightingDefinition);
+                    hlm.RegisterHighlighting(name, [.. xshd.Extensions], highlightingDefinition);
             }
             catch (Exception e)
             {
@@ -217,34 +217,36 @@ public class Plugin : IViewer
     }
 }
 
-file static class ResourceNameHelper
+file static class EmbeddedResource
 {
-    /// <summary>
-    /// Converts a resource name (using '.' as separators) into a dummy file path
-    /// by replacing inner dots with backslashes, while preserving the file extension.
-    ///
-    /// Example:
-    /// Input:  "Resources.Images.icon.png"
-    /// Output: "Resources\Images\icon.png"
-    ///
-    /// Input:  "Assets.Sounds.music.background.mp3"
-    /// Output: "Assets\Sounds\music\background.mp3"
-    /// </summary>
-    /// <param name="resourceName">The embedded resource name (excluding the default namespace).</param>
-    /// <returns>A string representing the resource as a dummy file path.</returns>
-    public static string ToResourceDummyName(this string resourceName)
+    public static string GetFileNameWithoutExtension(string resourceName)
     {
-        if (string.IsNullOrWhiteSpace(resourceName))
-            return resourceName;
+        // Requires the embedded resource file name
+        // must have a file extension and have only one '.' character
+        int start = int.MinValue, end = int.MinValue;
 
-        int lastDotIndex = resourceName.LastIndexOf('.');
-        if (lastDotIndex <= 0) // Either no dot or dot is at the beginning
-            return resourceName;
+        for (int i = resourceName.Length - 1; i >= 0; i--)
+        {
+            if (resourceName[i] == '.')
+            {
+                if (end == int.MinValue)
+                {
+                    end = i;
+                    continue;
+                }
 
-        // Replace dots before the extension with backslashes
-        string pathWithoutExtension = resourceName.Substring(0, lastDotIndex).Replace('.', '\\');
-        string extension = resourceName.Substring(lastDotIndex);
+                if (start == int.MinValue)
+                {
+                    start = i + 1; // Exinclude '.' character
+                    break;
+                }
+            }
+        }
 
-        return pathWithoutExtension + extension;
+        if ((start != int.MinValue) && (end != int.MinValue))
+        {
+            return resourceName.Substring(start, end - start);
+        }
+        return resourceName;
     }
 }