Proposal: Length is definitive, fallback to modified if no length

src/NzbDrone.Core.Test/MediaCoverTests/CoverExistsSpecificationFixture.cs

@@ -27,7 +27,7 @@ namespace NzbDrone.Core.Test.MediaCoverTests
         }
 
         [Test]
-        public void should_return_false_if_file_exists_but_diffrent_date()
+        public void should_return_false_if_file_exists_but_different_date()
         {
             GivenFileExistsOnDisk(DateTime.Now);
 
@@ -35,7 +35,7 @@ namespace NzbDrone.Core.Test.MediaCoverTests
         }
 
         [Test]
-        public void should_return_ture_if_file_exists_and_same_date_but_no_length_header()
+        public void should_return_true_if_file_exists_and_same_date_but_no_length_header()
         {
             var givenDate = DateTime.Now;
 
@@ -45,12 +45,31 @@ namespace NzbDrone.Core.Test.MediaCoverTests
         }
 
         [Test]
-        public void should_return_ture_if_file_exists_and_date_header_is_null_but_has_length_header()
+        public void should_return_false_if_file_exists_and_same_date_but_length_header_different()
         {
+            var givenDate = DateTime.Now;
 
+            GivenFileExistsOnDisk(givenDate);
+
+            Subject.AlreadyExists(givenDate, 999, "c:\\file.exe").Should().BeFalse();
+        }
+
+
+        [Test]
+        public void should_return_true_if_file_exists_and_date_header_is_null_but_has_length_header()
+        {
             GivenFileExistsOnDisk(DateTime.Now);
 
             Subject.AlreadyExists(null, 1000, "c:\\file.exe").Should().BeTrue();
         }
+
+        [Test]
+        public void should_return_true_if_file_exists_and_date_header_is_different_but_length_header_the_same()
+        {
+            GivenFileExistsOnDisk(DateTime.Now.AddDays(-1));
+
+            Subject.AlreadyExists(DateTime.Now, 1000, "c:\\file.exe").Should().BeTrue();
+        }
+
     }
 }

src/NzbDrone.Core/MediaCover/CoverAlreadyExistsSpecification.cs

@@ -1,6 +1,5 @@
 using System;
 using NzbDrone.Common.Disk;
-using NzbDrone.Common.Http;
 
 namespace NzbDrone.Core.MediaCover
 {
@@ -25,13 +24,6 @@ namespace NzbDrone.Core.MediaCover
                 return false;
             }
 
-            if (serverModifiedDate.HasValue)
-            {
-                DateTime? lastModifiedLocal = _diskProvider.FileGetLastWrite(localPath);
-
-                return lastModifiedLocal.Value.ToUniversalTime() == serverModifiedDate.Value.ToUniversalTime();
-            }
-
             if (serverContentLength.HasValue && serverContentLength.Value > 0)
             {
                 var fileSize = _diskProvider.GetFileSize(localPath);
@@ -39,6 +31,13 @@ namespace NzbDrone.Core.MediaCover
                 return fileSize == serverContentLength;
             }
 
+            if (serverModifiedDate.HasValue)
+            {
+                DateTime? lastModifiedLocal = _diskProvider.FileGetLastWrite(localPath);
+
+                return lastModifiedLocal.Value.ToUniversalTime() == serverModifiedDate.Value.ToUniversalTime();
+            }
+
             return false;
         }
     }