refactored message processor as per PR comments to reduce the memory allocation on the single invoker scenario

Author: t11omas

src/SlimMessageBus.Host/Consumer/MessageProcessors/MessageProcessor.cs

@@ -1,6 +1,7 @@
 namespace SlimMessageBus.Host;
 
 using System.Diagnostics;
+using System.Text.RegularExpressions;
 
 using SlimMessageBus.Host.Consumer;
 
@@ -187,56 +188,67 @@ protected Type GetMessageType(IReadOnlyDictionary<string, object> headers)
 
     protected IEnumerable<IMessageTypeConsumerInvokerSettings> TryMatchConsumerInvoker(Type messageType, IReadOnlyDictionary<string, object> messageHeaders, object transportMessage)
     {
-
-        var invokers = _singleInvoker != null ? [_singleInvoker] : _invokers;
-        var found = false;
-
 
-        foreach (var invoker in invokers.Where(x => RuntimeTypeCache.IsAssignableFrom(messageType, x.MessageType)))
-        {
-            // If either the invoker has a filter or the parent consumer has a filter evaluate it. 
-            var invFilter = invoker.Filter ?? invoker.ParentSettings.Filter;
 
-            if (invFilter != null)
+        if (_singleInvoker != null)
+        {
+            if (ApplyFilter(_singleInvoker, messageHeaders, transportMessage))
             {
-                bool matches;
-                try
+                // fallback to the first one
+                yield return _singleInvoker;
+            }
+        }
+        else
+        {
+            var found = false;
+            foreach (var invoker in _invokers.Where(x => RuntimeTypeCache.IsAssignableFrom(messageType, x.MessageType)))
+            {
+                if (ApplyFilter(invoker, messageHeaders, transportMessage))
                 {
-                    matches = invFilter(messageHeaders, transportMessage);
+                    found = true;
+                    yield return invoker;
                 }
-                catch (Exception ex)
-                {
-                    // If filter throws, treat as non-match and log 
-                    FilterException(invoker.ConsumerType.Name, Path, ex);
+            }
 
-                    matches = false;
+            if (!found)
+            {
+                if (_shouldLogWhenUnrecognizedMessageType)
+                {
+                    var consumerTypes = string.Join(",", _invokers.Select(x => x.ConsumerType.Name));
+                    LogNoConsumerTypeMatched(messageType, Path, MessageHeaders.MessageType, consumerTypes);
                 }
 
-                if (!matches)
+                if (_shouldFailWhenUnrecognizedMessageType)
                 {
-                    continue;
+                    throw new ConsumerMessageBusException($"The message on path {Path} declared {MessageHeaders.MessageType} header of type {messageType}, but none of the known consumer types {string.Join(",", _invokers.Select(x => x.ConsumerType.Name))} was able to handle that");
                 }
             }
-
-            found = true;
-            yield return invoker;
         }
+    }
+
+    private bool ApplyFilter(IMessageTypeConsumerInvokerSettings invoker,
+        IReadOnlyDictionary<string, object> messageHeaders,
+        object transportMessage)
+    {
+        // If either the invoker has a filter or the parent consumer has a filter evaluate it. 
+        var invFilter = invoker.Filter ?? invoker.ParentSettings.Filter;
 
-        if (!found)
+        if (invFilter == null)
         {
-            if (_shouldLogWhenUnrecognizedMessageType)
-            {
-                var consumerTypes = string.Join(",", _invokers.Select(x => x.ConsumerType.Name));
-                LogNoConsumerTypeMatched(messageType, Path, MessageHeaders.MessageType, consumerTypes);
-            }
+            return true;
+        }
 
-            if (_shouldFailWhenUnrecognizedMessageType)
-            {
-                throw new ConsumerMessageBusException($"The message on path {Path} declared {MessageHeaders.MessageType} header of type {messageType}, but none of the known consumer types {string.Join(",", _invokers.Select(x => x.ConsumerType.Name))} was able to handle that");
-            }
+        try
+        {
+            return invFilter(messageHeaders, transportMessage);
+        }
+        catch (Exception ex)
+        {
+            // If filter throws, treat as non-match and log 
+            FilterException(_singleInvoker.ConsumerType.Name, Path, ex);
+            return false;
         }
     }
-
     #region Logging
 
     [LoggerMessage(