some preliminary work to move decision engine to use the visitor pattern.

NzbDrone.Core/DecisionEngine/Specifications/AllowedReleaseGroupSpecification.cs

@@ -0,0 +1,50 @@
+using System;
+using NLog;
+using NzbDrone.Core.Configuration;
+using NzbDrone.Core.Model;
+
+namespace NzbDrone.Core.DecisionEngine.Specifications
+{
+    public class AllowedReleaseGroupSpecification : IFetchableSpecification
+    {
+        private readonly IConfigService _configService;
+        private readonly Logger _logger;
+
+        public AllowedReleaseGroupSpecification(IConfigService configService, Logger logger)
+        {
+            _configService = configService;
+            _logger = logger;
+        }
+
+
+        public string RejectionReason
+        {
+            get
+            {
+                return "Release group is blacklisted.";
+            }
+        }
+
+        public virtual bool IsSatisfiedBy(EpisodeParseResult subject)
+        {
+            _logger.Trace("Beginning release group check for: {0}", subject);
+
+            var allowed = _configService.AllowedReleaseGroups;
+
+            if (string.IsNullOrWhiteSpace(allowed))
+                return true;
+
+            foreach (var group in allowed.Trim(',', ' ').Split(','))
+            {
+                if (subject.ReleaseGroup.Equals(group.Trim(' '), StringComparison.CurrentCultureIgnoreCase))
+                {
+                    _logger.Trace("Item: {0}'s release group is wanted: {1}", subject, subject.ReleaseGroup);
+                    return true;
+                }
+            }
+
+            _logger.Trace("Item: {0}'s release group is not wanted: {1}", subject, subject.ReleaseGroup);
+            return false;
+        }
+    }
+}