never executed always true always false

    1 module PureClaw.Handles.Log
    2   ( -- * Handle type
    3     LogHandle (..)
    4     -- * Implementations
    5   , mkStderrLogHandle
    6   , mkNoOpLogHandle
    7   ) where
    8 
    9 import Data.Text (Text)
   10 import Data.Text.IO qualified as TIO
   11 import Data.Text qualified as T
   12 import Data.Time
   13 import System.IO
   14 
   15 -- | Logging capability. Functions that only receive a 'LogHandle' cannot
   16 -- shell out, read files, or access the network — they can only log.
   17 data LogHandle = LogHandle
   18   { _lh_logInfo  :: Text -> IO ()
   19   , _lh_logWarn  :: Text -> IO ()
   20   , _lh_logError :: Text -> IO ()
   21   , _lh_logDebug :: Text -> IO ()
   22   }
   23 
   24 -- | Log to stderr with ISO 8601 timestamps and level prefixes.
   25 mkStderrLogHandle :: LogHandle
   26 mkStderrLogHandle = LogHandle
   27   { _lh_logInfo  = logWithLevel "INFO"
   28   , _lh_logWarn  = logWithLevel "WARN"
   29   , _lh_logError = logWithLevel "ERROR"
   30   , _lh_logDebug = logWithLevel "DEBUG"
   31   }
   32   where
   33     logWithLevel :: Text -> Text -> IO ()
   34     logWithLevel level msg = do
   35       now <- getCurrentTime
   36       let timestamp = T.pack (formatTime defaultTimeLocale "%Y-%m-%dT%H:%M:%S" now)
   37       TIO.hPutStrLn stderr $ "[" <> timestamp <> "] [" <> level <> "] " <> msg
   38 
   39 -- | No-op log handle. All operations silently succeed.
   40 mkNoOpLogHandle :: LogHandle
   41 mkNoOpLogHandle = LogHandle
   42   { _lh_logInfo  = \_ -> pure ()
   43   , _lh_logWarn  = \_ -> pure ()
   44   , _lh_logError = \_ -> pure ()
   45   , _lh_logDebug = \_ -> pure ()
   46   }