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

NzbDrone.Core/DecisionEngine/QualityUpgradableSpecification.cs

@@ -0,0 +1,47 @@
+using NLog;
+using NzbDrone.Core.Qualities;
+using NzbDrone.Core.Tv;
+
+namespace NzbDrone.Core.DecisionEngine
+{
+    public interface IQualityUpgradableSpecification
+    {
+        bool IsUpgradable(QualityProfile profile, QualityModel currentQuality, QualityModel newQuality = null);
+    }
+
+    public class QualityUpgradableSpecification : IQualityUpgradableSpecification
+    {
+        private readonly Logger _logger;
+
+        public QualityUpgradableSpecification(Logger logger)
+        {
+            _logger = logger;
+        }
+
+        public bool IsUpgradable(QualityProfile profile, QualityModel currentQuality, QualityModel newQuality = null)
+        {
+            if (newQuality != null)
+            {
+                if (currentQuality >= newQuality)
+                {
+                    _logger.Trace("existing item has better or equal quality. skipping");
+                    return false;
+                }
+
+                if (currentQuality.Quality == newQuality.Quality && newQuality.Proper)
+                {
+                    _logger.Trace("Upgrading existing item to proper.");
+                    return true;
+                }
+            }
+
+            if (currentQuality.Quality >= profile.Cutoff)
+            {
+                _logger.Trace("Existing item meets cut-off. skipping.");
+                return false;
+            }
+
+            return true;
+        }
+    }
+}