refactor: clean up per good-code review

- Remove internal helpers from Postgres.hs export list (withDB, withDB',
  handleDuplicate, assertUpdated, withLog are not imported externally)
- Replace local isNothing_ with Data.Maybe.isNothing in Env.hs
- Consolidate duplicate/unused imports in XFTPStoreTests.hs
- Add file_path IS NULL and status guards to STM setFilePath, matching
  the Postgres implementation semantics

src/Simplex/FileTransfer/Server/Env.hs

@@ -41,6 +41,7 @@ import Simplex.FileTransfer.Server.Store
 import Simplex.Messaging.Agent.Store.Shared (MigrationConfirmation)
 #if defined(dbServerPostgres)
 import Data.Functor (($>))
+import Data.Maybe (isNothing)
 import Simplex.FileTransfer.Server.Store.Postgres (PostgresFileStore, importFileStore, exportFileStore)
 import Simplex.FileTransfer.Server.Store.Postgres.Config (PostgresFileStoreCfg (..), defaultXFTPDBOpts)
 import Simplex.Messaging.Server.CLI (iniDBOptions, settingIsOn)
@@ -190,14 +191,11 @@ checkFileStoreMode ini storeType storeLogFilePath = case storeType of
   "database" -> do
     storeLogExists <- doesFileExist storeLogFilePath
     let dbStoreLogOn = settingIsOn "STORE_LOG" "db_store_log" ini
-    when (storeLogExists && isNothing_ dbStoreLogOn) $ do
+    when (storeLogExists && isNothing dbStoreLogOn) $ do
       putStrLn $ "Error: store log file " <> storeLogFilePath <> " exists but store_files is `database`."
       putStrLn "Use `file-server database import` to migrate, or set `db_store_log: on`."
       exitFailure
   _ -> pure ()
-  where
-    isNothing_ Nothing = True
-    isNothing_ _ = False
 #else
 checkFileStoreMode _ _ _ = pure ()
 #endif

src/Simplex/FileTransfer/Server/Store.hs

@@ -97,9 +97,15 @@ instance FileStoreClass STMFileStore where
       pure $ Right ()
 
   setFilePath st sId fPath = atomically $
-    withSTMFile st sId $ \FileRec {filePath} -> do
-      writeTVar filePath (Just fPath)
-      pure $ Right ()
+    withSTMFile st sId $ \FileRec {filePath, fileStatus} -> do
+      readTVar filePath >>= \case
+        Just _ -> pure $ Left AUTH
+        Nothing ->
+          readTVar fileStatus >>= \case
+            EntityActive -> do
+              writeTVar filePath (Just fPath)
+              pure $ Right ()
+            _ -> pure $ Left AUTH
 
   addRecipient st@STMFileStore {recipients} senderId (FileRecipient rId rKey) = atomically $
     withSTMFile st senderId $ \FileRec {recipientIds} -> do

src/Simplex/FileTransfer/Server/Store/Postgres.hs

@@ -9,11 +9,6 @@
 
 module Simplex.FileTransfer.Server.Store.Postgres
   ( PostgresFileStore (..),
-    withDB,
-    withDB',
-    handleDuplicate,
-    assertUpdated,
-    withLog,
     importFileStore,
     exportFileStore,
   )