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|
--------------------------------------------------------------------------------
-- | Produce pretty, thread-safe logs
module Hakyll.Core.Logger
( Verbosity (..)
, Logger
, new
, flush
, error
, header
, message
, debug
) where
--------------------------------------------------------------------------------
import Control.Applicative (pure, (<$>), (<*>))
import Control.Concurrent (forkIO)
import Control.Concurrent.Chan (Chan, newChan, readChan, writeChan)
import Control.Concurrent.MVar (MVar, newEmptyMVar, putMVar, takeMVar)
import Control.Monad (forever)
import Control.Monad.Trans (MonadIO, liftIO)
import Prelude hiding (error)
--------------------------------------------------------------------------------
data Verbosity
= Error
| Message
| Debug
deriving (Eq, Ord, Show)
--------------------------------------------------------------------------------
-- | Logger structure. Very complicated.
data Logger = Logger
{ loggerChan :: Chan (Maybe String) -- ^ Nothing marks the end
, loggerSync :: MVar () -- ^ Used for sync on quit
, loggerSink :: String -> IO () -- ^ Out sink
, loggerVerbosity :: Verbosity -- ^ Verbosity
}
--------------------------------------------------------------------------------
-- | Create a new logger
new :: Verbosity -> IO Logger
new vbty = do
logger <- Logger <$>
newChan <*> newEmptyMVar <*> pure putStrLn <*> pure vbty
_ <- forkIO $ loggerThread logger
return logger
where
loggerThread logger = forever $ do
msg <- readChan $ loggerChan logger
case msg of
-- Stop: sync
Nothing -> putMVar (loggerSync logger) ()
-- Print and continue
Just m -> loggerSink logger m
--------------------------------------------------------------------------------
-- | Flush the logger (blocks until flushed)
flush :: Logger -> IO ()
flush logger = do
writeChan (loggerChan logger) Nothing
() <- takeMVar $ loggerSync logger
return ()
--------------------------------------------------------------------------------
string :: MonadIO m
=> Logger -- ^ Logger
-> Verbosity -- ^ Verbosity of the string
-> String -- ^ Section name
-> m () -- ^ No result
string l v m
| loggerVerbosity l >= v = liftIO $ writeChan (loggerChan l) (Just m)
| otherwise = return ()
--------------------------------------------------------------------------------
error :: MonadIO m => Logger -> String -> m ()
error l m = string l Error $ " [ERROR] " ++ m
--------------------------------------------------------------------------------
header :: MonadIO m => Logger -> String -> m ()
header l = string l Message
--------------------------------------------------------------------------------
message :: MonadIO m => Logger -> String -> m ()
message l m = string l Message $ " " ++ m
--------------------------------------------------------------------------------
debug :: MonadIO m => Logger -> String -> m ()
debug l m = string l Debug $ " [DEBUG] " ++ m
|
