some error handling and cleanup that comes with it

app/Main.hs

@@ -16,6 +16,7 @@ import System.Environment
 import System.Exit
 import Data.Time.Format.ISO8601
 import Sender
+import Monad
 
 isChoirThisWeek :: Day -> Day -> Bool
 isChoirThisWeek today day = today <= day && diffDays day today <= 6
@@ -23,30 +24,46 @@ isChoirThisWeek today day = today <= day && diffDays day today <= 6
 getToday :: IO Day
 getToday = utctDay <$> getCurrentTime
 
-reportError :: String -> IO ()
-reportError err = hPutStr stderr err
+reportErrorLocal :: MonadIO m => String -> m ()
+reportErrorLocal err = liftIO $ hPutStr stderr err
+
+reportErrorMail :: MonadIO m => Config -> String -> m ()
+reportErrorMail config error' = send (mailDomain config) (mailUsername config) (mailPassword config) (mailErrorTo config) (mailFrom config) "choirMail Error" (LT.pack error')
+
+findChoirDay :: Day -> [MailRecord] -> Either String MailRecord
+findChoirDay today table = maybe
+  (Left "Keine Probe :(")
+  (Right)
+  (L.find ((isChoirThisWeek today) .date) table)
+
+
+main' :: App ()
+main' = do
+  args <- liftIO getArgs
+  if length args /= 1
+  then
+    fail "We need exactly one config path as option"
+  else do
+    config <- parseConfigFile (head args)
+    -- we want to handle these while we have the config in scope
+    result <- liftIO $ runApp $ do
+      bs <- request
+      table <- except $ parseBString bs
+      today <- liftIO getToday
+      record <- except $ findChoirDay today table
+      send (mailDomain config) (mailUsername config) (mailPassword config) (mailTo config) (mailFrom config) (mailSubject record) (mailText record)
+    case result of
+      Right x -> return x
+      Left error' -> reportErrorMail config error'
+
+
 
 main :: IO ()
 main = do
-  args <- getArgs
-  if length args /= 1
-  then
-    die "We need exactly one argument"
-  else do
-    configE <- parseFile (head args)
-    case configE of
-      Left text -> reportError text
-      Right config -> do
-        bs <- request
-        let eitherTable = parseBString bs
-        case eitherTable of
-          Left x -> reportError x
-          Right table -> do
-            today <- getToday
-            maybe 
-              (T.putStr "Keine Probe :(")
-              (\record -> send (mailDomain config) (mailUsername config) (mailPassword config) (mailTo config) (mailFrom config) (mailSubject record) (mailText record))
-              (L.find ((isChoirThisWeek today) . date) table)
+  result <- runApp main'
+  case result of
+    Right x -> return x
+    Left error' -> reportErrorLocal error'
 
 mailText :: MailRecord -> LT.Text
 mailText record = LT.fromStrict $T.concat ["Guten Morgen,\n\n"