add default error and debug log functions

src/Env.hs

@@ -2,7 +2,7 @@
 
 module Env(Env(..), App(..), runMover, SourceFunctions(..)) where
 
-import Log(Logger(..))
+import Log
 import Mover
 import Source
 import Destination
@@ -11,7 +11,6 @@ import Message
 import Filter
 import Control.Monad.Trans.Reader (ReaderT)
 import Control.Monad.Reader (MonadReader, liftIO, ask, asks, MonadIO, runReaderT)
-import qualified Data.Text.IO as T(putStrLn)
 
 data SourceFunctions = MkSourceFunctions (IO (Either NoMessageReason Message)) ([ReceiveId] -> IO ())
 
@@ -42,8 +41,8 @@ instance Filter App where
     liftIO $ (envFilterAction env) msg
 
 instance Logger App where
-  logError = liftIO . T.putStrLn
-  logDebug = logError
+  logError = ioErrorLog
+  logDebug = ioDebugLog
 
 runMover :: Env -> IO ()
 runMover = runReaderT (run moveMessages)

src/Log.hs

@@ -1,8 +1,19 @@
-module Log(Logger(..)) where
+module Log(Logger(..), ioErrorLog, ioDebugLog) where
 
 import Data.Text
+import qualified Data.Text.IO as TIO(putStrLn)
+import qualified Data.Text as T(concat)
+import Control.Monad.IO.Class(MonadIO, liftIO)
 
 class Monad m => Logger m where
   logError :: Text -> m ()
   logDebug :: Text -> m ()
 
+ioErrorLog :: MonadIO m => Text -> m ()
+ioErrorLog = ioLog "ERROR "
+
+ioDebugLog :: MonadIO m => Text -> m ()
+ioDebugLog = ioLog "DEBUG "
+
+ioLog :: MonadIO m => Text -> Text -> m ()
+ioLog prefix msg = liftIO $ TIO.putStrLn $ T.concat [prefix, msg]