Check for ordering of effective dates of policies

Author: Matthias Gessinger

src/Abstractions/src/Asp.Versioning.Abstractions/DeprecationPolicy.cs

@@ -55,4 +55,24 @@ public DeprecationPolicy() { }
     /// </summary>
     /// <param name="link">The link which provides information about the deprecation policy.</param>
     public DeprecationPolicy( LinkHeaderValue link ) => Links.Add( link );
+
+    /// <summary>
+    /// Returns a boolean to indicate if this policy is effective at the given <paramref name="dateTimeOffset"/>.
+    /// </summary>
+    /// <param name="dateTimeOffset">The point in time to serve as a reference.</param>
+    /// <returns>A boolean which indicates if this policy is effective.</returns>
+    public bool IsEffective( DateTimeOffset? dateTimeOffset )
+    {
+        if ( dateTimeOffset is not { } when )
+        {
+            return true;
+        }
+
+        if ( Date is not { } date )
+        {
+            return true;
+        }
+
+        return date < when;
+    }
 }

src/Common/src/Common/DefaultApiVersionReporter.cs

@@ -94,15 +94,20 @@ public void Report( HttpResponse response, ApiVersionModel apiVersionModel )
         var version = context.GetRequestedApiVersion();
 #endif
         var name = metadata.Name;
+        DateTimeOffset? sunsetDate = null;
 
         if ( sunsetPolicyManager.TryResolvePolicy( name, version, out var sunsetPolicy ) )
         {
+            sunsetDate = sunsetPolicy.Date;
             response.WriteSunsetPolicy( sunsetPolicy );
         }
 
         if ( deprecationPolicyManager.TryResolvePolicy( name, version, out var deprecationPolicy ) )
         {
-            response.WriteDeprecationPolicy( deprecationPolicy );
+            if ( deprecationPolicy.IsEffective( sunsetDate ) )
+            {
+                response.WriteDeprecationPolicy( deprecationPolicy );
+            }
         }
     }
 }