Fixed: Improve moving file to location where another one exists

Closes #1762

src/NzbDrone.Common/Disk/DiskProviderBase.cs

@@ -278,6 +278,11 @@ namespace NzbDrone.Common.Disk
 
         protected virtual void MoveFileInternal(string source, string destination)
         {
+            if (File.Exists(destination))
+            {
+                throw new FileAlreadyExistsException("File already exists", destination);
+            }
+
             _fileSystem.File.Move(source, destination);
         }
 

src/NzbDrone.Common/Disk/FileAlreadyExistsException.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace NzbDrone.Common.Disk
+{
+    public class FileAlreadyExistsException : Exception
+    {
+        public string Filename { get; set; }
+
+        public FileAlreadyExistsException(string message, string filename)
+            : base(message)
+        {
+            Filename = filename;
+        }
+    }
+}

src/NzbDrone.Core/MediaFiles/RenameBookFileService.cs

@@ -135,6 +135,10 @@ namespace NzbDrone.Core.MediaFiles
 
                     _eventAggregator.PublishEvent(new BookFileRenamedEvent(author, bookFile, bookFilePath));
                 }
+                catch (FileAlreadyExistsException ex)
+                {
+                    _logger.Warn("File not renamed, there is already a file at the destination: {0}", ex.Filename);
+                }
                 catch (SameFilenameException ex)
                 {
                     _logger.Debug("File not renamed, source and destination are the same: {0}", ex.Filename);