{-# LANGUAGE UndecidableInstances #-}
-- | The 'LogWriter' type encapsulates an effectful function to write 'LogMessage's.
--
-- Used in conjunction with the 'HandleLogWriter' class, it
-- can be used to write messages from within an effectful
-- computation.
module Control.Eff.Log.Writer
(
-- * 'LogWriter' Definition
LogWriter(..)
-- * LogWriter Reader Effect
, LogWriterReader
, localLogWriterReader
, askLogWriter
, runLogWriterReader
-- * LogWriter Handler Class
, HandleLogWriter(..)
-- ** 'LogWriter' Handler Instance Zoo
-- *** Pure Writer
, noOpLogWriter
, debugTraceLogWriter
, PureLogWriter(..)
-- *** List Writer
, listLogWriter
, CaptureLogs(..)
, CapturedLogsWriter
, runCapturedLogsWriter
-- *** IO Writer
, consoleLogWriter
, ioHandleLogWriter
-- ** Writer Combinator
-- *** Pure Writer Combinator
, filteringLogWriter
, mappingLogWriter
-- *** Impure Writer Combinator
, mappingLogWriterM
-- *** IO Based Combinator
, ioLogWriter
, defaultIoLogWriter
)
where
import Control.Eff
import Control.Eff.Extend
import Control.Eff.Log.Message
import Data.Default
import Data.Function ( fix )
import Debug.Trace
import GHC.Stack
import Control.Eff.Writer.Strict ( Writer
, tell
, runListWriter
)
import Data.Functor.Identity ( Identity )
import Control.DeepSeq ( force )
import Data.Foldable ( traverse_ )
import qualified System.IO as IO
import Control.Monad ( (>=>)
, when
)
import Control.Monad.Base ( MonadBase() )
import qualified Control.Monad.Catch as Catch
import Control.Monad.Trans.Control ( MonadBaseControl
( restoreM
, liftBaseWith
, StM
)
)
import Data.Kind
import Control.Lens
-- | A function that takes a log message and returns an effect that
-- /logs/ the message.
newtype LogWriter writerM = MkLogWriter
{ runLogWriter :: LogMessage -> writerM ()
}
instance Applicative w => Default (LogWriter w) where
def = MkLogWriter (const (pure ()))
-- | Provide the 'LogWriter'
--
-- Exposed for custom extensions, if in doubt use 'withLogging'.
runLogWriterReader :: LogWriter h -> Eff (LogWriterReader h ': e) a -> Eff e a
runLogWriterReader e m = fix (handle_relay (\x _ -> return x)) m e
-- | Get the current 'LogWriter'.
askLogWriter
:: SetMember LogWriterReader (LogWriterReader h) e => Eff e (LogWriter h)
askLogWriter = send AskLogWriter
-- | Modify the current 'LogWriter'.
localLogWriterReader
:: forall h e a
. SetMember LogWriterReader (LogWriterReader h) e
=> (LogWriter h -> LogWriter h)
-> Eff e a
-> Eff e a
localLogWriterReader f m =
f
<$> askLogWriter
>>= fix (respond_relay @(LogWriterReader h) (\x _ -> return x)) m
-- | A Reader specialized for 'LogWriter's
--
-- The existing @Reader@ couldn't be used together with 'SetMember', so this
-- lazy reader was written, specialized to reading 'LogWriter'.
data LogWriterReader h v where
AskLogWriter ::LogWriterReader h (LogWriter h)
instance Handle (LogWriterReader h) e a (LogWriter h -> k) where
handle k q AskLogWriter lw = k (q ^$ lw) lw
instance forall h m r. (MonadBase m m, LiftedBase m r)
=> MonadBaseControl m (Eff (LogWriterReader h ': r)) where
type StM (Eff (LogWriterReader h ': r)) a = StM (Eff r) a
liftBaseWith f = do
lf <- askLogWriter
raise (liftBaseWith (\runInBase -> f (runInBase . runLogWriterReader lf)))
restoreM = raise . restoreM
instance (LiftedBase m e, Catch.MonadThrow (Eff e))
=> Catch.MonadThrow (Eff (LogWriterReader h ': e)) where
throwM exception = raise (Catch.throwM exception)
instance (Applicative m, LiftedBase m e, Catch.MonadCatch (Eff e))
=> Catch.MonadCatch (Eff (LogWriterReader h ': e)) where
catch effect handler = do
lf <- askLogWriter
let lower = runLogWriterReader lf
nestedEffects = lower effect
nestedHandler exception = lower (handler exception)
raise (Catch.catch nestedEffects nestedHandler)
instance (Applicative m, LiftedBase m e, Catch.MonadMask (Eff e))
=> Catch.MonadMask (Eff (LogWriterReader h ': e)) where
mask maskedEffect = do
lf <- askLogWriter
let lower :: Eff (LogWriterReader h ': e) a -> Eff e a
lower = runLogWriterReader lf
raise
(Catch.mask
(\nestedUnmask -> lower (maskedEffect (raise . nestedUnmask . lower)))
)
uninterruptibleMask maskedEffect = do
lf <- askLogWriter
let lower :: Eff (LogWriterReader h ': e) a -> Eff e a
lower = runLogWriterReader lf
raise
(Catch.uninterruptibleMask
(\nestedUnmask -> lower (maskedEffect (raise . nestedUnmask . lower)))
)
generalBracket acquire release useIt = do
lf <- askLogWriter
let lower :: Eff (LogWriterReader h ': e) a -> Eff e a
lower = runLogWriterReader lf
raise
(Catch.generalBracket (lower acquire)
(((.) . (.)) lower release)
(lower . useIt)
)
-- * 'LogWriter' Zoo
-- | The instances of this class are the monads that define (side-) effect(s) of writting logs.
class HandleLogWriter (writerEff :: Type -> Type) where
-- | A list of effects that are required for writing the log messages.
-- For example 'Lift IO' or '[]' for pure log writers.
type LogWriterEffects writerEff :: [Type -> Type]
-- | Run the side effect of a 'LogWriter' in a compatible 'Eff'.
handleLogWriterEffect :: (LogWriterEffects writerEff <:: e) => writerEff () -> Eff e ()
-- | Write a message using the 'LogWriter' found in the environment.
--
-- The semantics of this function are a combination of 'runLogWriter' and 'handleLogWriterEffect',
-- with the 'LogWriter' read from a 'LogWriterReader'.
liftWriteLogMessage :: ( SetMember LogWriterReader (LogWriterReader writerEff) e
, LogWriterEffects writerEff <:: e)
=> LogMessage
-> Eff e ()
liftWriteLogMessage m = do
w <- askLogWriter
handleLogWriterEffect (runLogWriter w m)
-- ** Pure Log Writers
-- | A phantom type for the 'HandleLogWriter' class for /pure/ 'LogWriter's
newtype PureLogWriter a = MkPureLogWriter { runPureLogWriter :: Identity a }
deriving (Applicative, Functor, Monad)
-- | A 'LogWriter' monad for 'Debug.Trace' based pure logging.
instance HandleLogWriter PureLogWriter where
type LogWriterEffects PureLogWriter = '[]
handleLogWriterEffect lw = return (force (runIdentity (force (runPureLogWriter lw))))
-- | This 'LogWriter' will discard all messages.
--
-- NOTE: This is just an alias for 'def'
noOpLogWriter :: Applicative m => LogWriter m
noOpLogWriter = def
-- | A 'LogWriter' that applies 'renderLogMessage' to the log message and then
-- traces it using 'traceM'.
-- This 'LogWriter' work with /any/ base monad.
debugTraceLogWriter :: Monad h => LogWriter h
debugTraceLogWriter = MkLogWriter (traceM . renderLogMessage)
-- ** Impure logging
-- | A 'LogWriter' monad that provides pure logging by capturing via the 'Writer' effect.
listLogWriter :: LogWriter CaptureLogs
listLogWriter = MkLogWriter (MkCaptureLogs . tell)
-- | A 'LogWriter' monad that provides pure logging by capturing via the 'Writer' effect.
newtype CaptureLogs a = MkCaptureLogs { unCaptureLogs :: Eff '[CapturedLogsWriter] a }
deriving (Functor, Applicative, Monad)
-- | A 'LogWriter' monad for pure logging.
--
-- The 'HandleLogWriter' instance for this type assumes a 'Writer' effect.
instance HandleLogWriter CaptureLogs where
type LogWriterEffects CaptureLogs = '[CapturedLogsWriter]
handleLogWriterEffect =
traverse_ (tell @LogMessage) . snd . run . runListWriter . unCaptureLogs
-- | Run a 'Writer' for 'LogMessage's.
--
-- Such a 'Writer' is needed for 'CaptureLogs'
runCapturedLogsWriter
:: Eff (CapturedLogsWriter ': e) a -> Eff e (a, [LogMessage])
runCapturedLogsWriter = runListWriter
-- | Alias for the 'Writer' that contains the captured 'LogMessage's from 'CaptureLogs'.
type CapturedLogsWriter = Writer LogMessage
-- | A 'LogWriter' that uses an 'IO' action to write the message.
--
-- Example use cases for this function are the 'consoleLogWriter' and the 'ioHandleLogWriter'.
ioLogWriter :: HasCallStack => (LogMessage -> IO ()) -> LogWriter IO
ioLogWriter = MkLogWriter
-- | A 'LogWriter' that renders 'LogMessage's to strings via 'renderLogMessage'
-- and prints them to an 'IO.Handle' using 'hPutStrLn'.
ioHandleLogWriter :: HasCallStack => IO.Handle -> LogWriter IO
ioHandleLogWriter h = ioLogWriter (IO.hPutStrLn h . renderLogMessage)
instance HandleLogWriter IO where
type LogWriterEffects IO = '[Lift IO]
handleLogWriterEffect = send . Lift
-- | Write 'LogMessage's to standard output, formatted with 'printLogMessage'.
consoleLogWriter :: LogWriter IO
consoleLogWriter = ioLogWriter printLogMessage
-- | Decorate an IO based 'LogWriter' to fill out these fields in 'LogMessage's:
--
-- * The messages will carry the given application name in the 'lmAppName' field.
-- * The 'lmTimestamp' field contains the UTC time of the log event
-- * The 'lmThreadId' field contains the thread-Id
-- * The 'lmHostname' field contains the FQDN of the current host
-- * The 'lmFacility' field contains the given 'Facility'
--
-- It works by using 'mappingLogWriterM'.
defaultIoLogWriter
:: String -- ^ The default application name to put into the 'lmAppName' field.
-> Facility -- ^ The default RFC-5424 facility to put into the 'lmFacility' field.
-> LogWriter IO -- ^ The IO based writer to decorate
-> LogWriter IO
defaultIoLogWriter appName facility = mappingLogWriterM
( setLogMessageThreadId
>=> setLogMessageTimestamp
>=> setLogMessageHostname
>=> pure
. set lmFacility facility
. set lmAppName (Just appName)
)
-- | A 'LogWriter' that applies a predicate to the 'LogMessage' and delegates to
-- to the given writer of the predicate is satisfied.
filteringLogWriter :: Monad e => LogPredicate -> LogWriter e -> LogWriter e
filteringLogWriter p lw =
MkLogWriter (\msg -> when (p msg) (runLogWriter lw msg))
-- | A 'LogWriter' that applies a function to the 'LogMessage' and delegates the result to
-- to the given writer.
mappingLogWriter :: (LogMessage -> LogMessage) -> LogWriter e -> LogWriter e
mappingLogWriter f lw = MkLogWriter (runLogWriter lw . f)
-- | Like 'mappingLogWriter' allow the function that changes the 'LogMessage' to have effects.
mappingLogWriterM
:: Monad e => (LogMessage -> e LogMessage) -> LogWriter e -> LogWriter e
mappingLogWriterM f lw = MkLogWriter (f >=> runLogWriter lw)