Apache style logger for WAI applications.

An example:

 {-# LANGUAGE OverloadedStrings #-}
 module Main where

 import Blaze.ByteString.Builder (fromByteString)
 import Control.Monad.IO.Class (liftIO)
 import qualified Data.ByteString.Char8 as BS
 import Network.HTTP.Types (status200)
 import Network.Wai (Application, responseBuilder)
 import Network.Wai.Handler.Warp (run)
 import Network.Wai.Logger (withStdoutLogger, ApacheLogger)

 main :: IO ()
 main = withStdoutLogger $ \aplogger ->
     run 3000 $ logApp aplogger

 logApp :: ApacheLogger -> Application
 logApp aplogger req = do
     liftIO $ aplogger req status (Just len)
     return $ responseBuilder status hdr msg
   where
     status = status200
     hdr = [("Content-Type", "text/plain")
           ,("Content-Length", BS.pack (show len))]
     pong = "PONG"
     len = fromIntegral $ BS.length pong
     msg = toLogStr pong