Make the config saving process more robust (#670)

src/Jackett/Services/IndexerManagerService.cs

@@ -148,10 +148,60 @@ namespace Jackett.Services
 
         public void SaveConfig(IIndexer indexer, JToken obj)
         {
+            var uID = Guid.NewGuid().ToString("N");
             var configFilePath = GetIndexerConfigFilePath(indexer);
+            var configFilePathBak = configFilePath + ".bak";
+            var configFilePathTmp = configFilePath + "." + uID + ".tmp";
+            var content = obj.ToString();
+
+            logger.Debug(string.Format("Saving new config file: {0}", configFilePathTmp));
+
+            if (string.IsNullOrWhiteSpace(content))
+            {
+                throw new Exception(string.Format("New config content for {0} is empty, please report this bug.", indexer.ID));
+            }
+
+            if (content.Contains("NULL"))
+            {
+                throw new Exception(string.Format("New config content for {0} contains NULL, please report this bug. Content: {1}", indexer.ID, content));
+            }
+
+            // make sure the config directory exists
             if (!Directory.Exists(configService.GetIndexerConfigDir()))
                 Directory.CreateDirectory(configService.GetIndexerConfigDir());
-            File.WriteAllText(configFilePath, obj.ToString());
+
+            // create new temporary config file
+            File.WriteAllText(configFilePathTmp, content);
+            var fileInfo = new FileInfo(configFilePathTmp);
+            if (fileInfo.Length == 0)
+            {
+                throw new Exception(string.Format("New config file {0} is empty, please report this bug.", configFilePathTmp));
+            }
+
+            // create backup file
+            File.Delete(configFilePathBak);
+            if (File.Exists(configFilePath))
+            {
+                try
+                {
+                    File.Move(configFilePath, configFilePathBak);
+                }
+                catch (IOException ex)
+                {
+                    logger.Error(string.Format("Error while moving {0} to {1}: {2}", configFilePath, configFilePathBak, ex.ToString()));
+                }
+            }
+
+            // replace the actual config file
+            File.Delete(configFilePath);
+            try
+            {
+                File.Move(configFilePathTmp, configFilePath);
+            }
+            catch (IOException ex)
+            {
+                logger.Error(string.Format("Error while moving {0} to {1}: {2}", configFilePath, configFilePathBak, ex.ToString()));
+            }
         }
     }
 }