Add more code documentation.

[dead/htsn.git] / src / Logging.hs

diff --git a/src/Logging.hs b/src/Logging.hs
index 94f4f7aa63bc383c23277c13bb8d93dd5b713cb3..ede739a28ba9a9027bbbebc894dc51a5ad0cdd18 100644 (file)
--- a/src/Logging.hs
+++ b/src/Logging.hs
@@ -6,13 +6,16 @@ module Logging (
   log_warning )
 where
 
-import System.Log.Handler.Simple ( fileHandler )
+import Control.Monad ( when )
+import System.Log.Formatter ( simpleLogFormatter )
+import System.Log.Handler ( setFormatter )
+import System.Log.Handler.Simple ( GenericHandler, fileHandler )
 import System.Log.Handler.Syslog (
   Facility ( USER ),
-  Option ( PID ),
   openlog )
 import System.Log.Logger (
-  Priority ( DEBUG, INFO ),
+  Priority ( INFO ),
+  addHandler,
   debugM,
   errorM,
   infoM,
@@ -22,26 +25,57 @@ import System.Log.Logger (
   updateGlobalLogger,
   warningM )
 
+
+-- | Log a message at the DEBUG level.
 log_debug :: String -> IO ()
 log_debug = debugM rootLoggerName
 
+-- | Log a message at the ERROR level.
 log_error :: String -> IO ()
 log_error = errorM rootLoggerName
 
+-- | Log a message at the INFO level.
 log_info :: String -> IO ()
 log_info = infoM rootLoggerName
 
+-- | Log a message at the WARNING level.
 log_warning :: String -> IO ()
 log_warning = warningM rootLoggerName
 
-init_logging :: FilePath -> Priority -> Bool -> IO ()
-init_logging log_file log_level syslog
-  | syslog == True = do
-      handler <- openlog rootLoggerName [PID] USER level
-      updateGlobalLogger rootLoggerName (setLevel level . setHandlers [handler])
-  | otherwise = do
-      handler <- fileHandler log_file level
-      updateGlobalLogger rootLoggerName (setLevel level . setHandlers [handler])
-  where
-    min_level = if syslog then INFO else DEBUG
-    level = if log_level < min_level then min_level else log_level
+
+-- | Set up the logging. All logs are handled by the global "root"
+--   logger provided by HSLogger. We remove all of its handlers so
+--   that it does nothing; then we conditionally add back two handlers
+--   -- one for syslog, and one for a normal file -- dependent upon
+--   the 'syslog' and 'log_file' configuration items.
+--
+--   Why don't we take a Configuration as an argument? Because it
+--   would create circular imports!
+init_logging :: Maybe FilePath -> Priority -> Bool -> IO ()
+init_logging log_file log_level syslog = do
+  -- First set the global log level and clear the default handler.
+  let no_handlers = [] :: [GenericHandler a]
+  updateGlobalLogger rootLoggerName (setLevel log_level .
+                                              setHandlers no_handlers)
+
+  when syslog $ do
+    let min_level = INFO
+    let sl_level = if log_level < min_level then min_level else log_level
+
+    -- The syslog handle gets its own level which will cowardly refuse
+    -- to log all debug info (i.e. the entire feed) to syslog.
+    sl_handler' <- openlog rootLoggerName [] USER sl_level
+
+    -- Syslog should output the date by itself.
+    let sl_formatter = simpleLogFormatter "htsn[$pid] $prio: $msg"
+    let sl_handler = setFormatter sl_handler' sl_formatter
+
+    updateGlobalLogger rootLoggerName (addHandler sl_handler)
+
+  case log_file of
+    Nothing -> return ()
+    Just lf -> do
+      lf_handler' <- fileHandler lf log_level
+      let lf_formatter = simpleLogFormatter "$time: htsn[$pid] $prio: $msg"
+      let lf_handler = setFormatter lf_handler' lf_formatter
+      updateGlobalLogger rootLoggerName (addHandler lf_handler)