content: {-# LANGUAGE TemplateHaskell, StandaloneDeriving,
               GeneralizedNewtypeDeriving #-}
  
  {-| Implementation of the Ganeti logging functionality.
  
  This currently lacks the following (FIXME):
  
  - log file reopening
  
  Note that this requires the hslogger library version 1.1 and above.
  
  -}
  
  {-
  
  Copyright (C) 2011, 2012, 2013 Google Inc.
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
  1. Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.
  
  2. Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  -}
  
  module Ganeti.Logging
    ( setupLogging
    , MonadLog(..)
    , Priority(..)
    , logDebug
    , logInfo
    , logNotice
    , logWarning
    , logError
    , logCritical
    , logAlert
    , logEmergency
    , SyslogUsage(..)
    , syslogUsageToRaw
    , syslogUsageFromRaw
    , withErrorLogAt
    , isDebugMode
    ) where
  
  import Control.Monad
  import Control.Monad.Except (MonadError(..), catchError)
  import Control.Monad.Reader
  import qualified Control.Monad.RWS.Strict as RWSS
  import qualified Control.Monad.State.Strict as SS
  import Control.Monad.Trans.Identity
  import Control.Monad.Trans.Maybe
  import System.Log.Logger
  import System.Log.Handler.Simple
  import System.Log.Handler.Syslog
  import System.Log.Handler (setFormatter, LogHandler)
  import System.Log.Formatter
  import System.IO
  
  import Ganeti.BasicTypes (Error(..), ResultT(..))
  import Ganeti.THH
  import qualified Ganeti.ConstantUtils as ConstantUtils
  
  -- | Syslog usage type.
  $(declareLADT ''String "SyslogUsage"
    [ ("SyslogNo",   "no")
    , ("SyslogYes",  "yes")
    , ("SyslogOnly", "only")
    ])
  
  -- | Builds the log formatter.
  logFormatter :: String  -- ^ Program
               -> Bool    -- ^ Multithreaded
               -> Bool    -- ^ Syslog
               -> LogFormatter a
  logFormatter prog mt syslog =
    let parts = [ if syslog
                    then "[$pid]:"
                    else "$time: " ++ prog ++ " pid=$pid"
                , if mt then if syslog then " ($tid)" else "/$tid"
                    else ""
                , " $prio $msg"
                ]
    in tfLogFormatter "%F %X,%q %Z" $ concat parts
  
  -- | Helper to open and set the formatter on a log if enabled by a
  -- given condition, otherwise returning an empty list.
  openFormattedHandler :: (LogHandler a) => Bool
                       -> LogFormatter a -> IO a -> IO [a]
  openFormattedHandler False _ _ = return []
  openFormattedHandler True fmt opener = do
    handler <- opener
    return [setFormatter handler fmt]
  
  -- | Sets up the logging configuration.
  setupLogging :: Maybe String    -- ^ Log file
               -> String    -- ^ Program name
               -> Bool      -- ^ Debug level
               -> Bool      -- ^ Log to stderr
               -> Bool      -- ^ Log to console
               -> SyslogUsage -- ^ Syslog usage
               -> IO ()
  setupLogging logf program debug stderr_logging console syslog = do
    let level = if debug then DEBUG else INFO
        destf = if console then Just ConstantUtils.devConsole else logf
        fmt = logFormatter program True False
        file_logging = syslog /= SyslogOnly
  
    updateGlobalLogger rootLoggerName (setLevel level)
  
    stderr_handlers <- openFormattedHandler stderr_logging fmt $
                       streamHandler stderr level
  
    file_handlers <- case destf of
                       Nothing -> return []
                       Just path -> openFormattedHandler file_logging fmt $
                                    fileHandler path level
  
    let handlers = file_handlers ++ stderr_handlers
    updateGlobalLogger rootLoggerName $ setHandlers handlers
    -- syslog handler is special (another type, still instance of the
    -- typeclass, and has a built-in formatter), so we can't pass it in
    -- the above list
    when (syslog /= SyslogNo) $ do
      syslog_handler <- openlog program [PID] DAEMON INFO
      updateGlobalLogger rootLoggerName $ addHandler syslog_handler
  
  -- * Logging function aliases
  
  -- | A monad that allows logging.
  class Monad m => MonadLog m where
    -- | Log at a given level.
    logAt :: Priority -> String -> m ()
  
  instance MonadLog IO where
    logAt = logM rootLoggerName
  
  deriving instance (MonadLog m) => MonadLog (IdentityT m)
  
  instance (MonadLog m) => MonadLog (MaybeT m) where
    logAt p = lift . logAt p
  
  instance (MonadLog m) => MonadLog (ReaderT r m) where
    logAt p = lift . logAt p
  
  instance (MonadLog m) => MonadLog (SS.StateT s m) where
    logAt p = lift . logAt p
  
  instance (MonadLog m, Monoid w) => MonadLog (RWSS.RWST r w s m) where
    logAt p = lift . logAt p
  
  instance (MonadLog m, Error e) => MonadLog (ResultT e m) where
    logAt p = lift . logAt p
  
  -- | Log at debug level.
  logDebug :: (MonadLog m) => String -> m ()
  logDebug = logAt DEBUG
  
  -- | Log at info level.
  logInfo :: (MonadLog m) => String -> m ()
  logInfo = logAt INFO
  
  -- | Log at notice level.
  logNotice :: (MonadLog m) => String -> m ()
  logNotice = logAt NOTICE
  
  -- | Log at warning level.
  logWarning :: (MonadLog m) => String -> m ()
  logWarning = logAt WARNING
  
  -- | Log at error level.
  logError :: (MonadLog m) => String -> m ()
  logError = logAt ERROR
  
  -- | Log at critical level.
  logCritical :: (MonadLog m) => String -> m ()
  logCritical = logAt CRITICAL
  
  -- | Log at alert level.
  logAlert :: (MonadLog m) => String -> m ()
  logAlert = logAt ALERT
  
  -- | Log at emergency level.
  logEmergency :: (MonadLog m) => String -> m ()
  logEmergency = logAt EMERGENCY
  
  -- | Check if the logging is at DEBUG level.
  -- DEBUG logging is unacceptable for production.
  isDebugMode :: IO Bool
  isDebugMode = (Just DEBUG ==) . getLevel <$> getRootLogger
  
  -- * Logging in an error monad with rethrowing errors
  
  -- | If an error occurs within a given computation, it annotated
  -- with a given message and logged and the error is re-thrown.
  withErrorLogAt :: (MonadLog m, MonadError e m, Show e)
                 => Priority -> String -> m a -> m a
  withErrorLogAt prio msg = flip catchError $ \e -> do
    logAt prio (msg ++ ": " ++ show e)
    throwError e
  