FastCGIUtils.hs

{-# LANGUAGE DeriveDataTypeable, CPP #-}
module FastCGIUtils (--initFastCGI, loopFastCGI,
                     throwCGIError, handleCGIErrors,
                     stderrToFile,
                     outputJSONP,
                     outputPNG,
                     outputHTML,
                     splitBy) where

import Control.Concurrent
import Control.Exception
import Control.Monad
import Data.Dynamic
import Data.IORef
import Prelude hiding (catch)
import System.Environment
import System.Exit
import System.IO
import System.IO.Unsafe
#ifndef mingw32_HOST_OS
import System.Posix
#endif

--import Network.FastCGI
import Network.CGI

import Text.JSON
import qualified Codec.Binary.UTF8.String as UTF8 (encodeString)
import qualified Data.ByteString.Lazy as BS

{- -- There are used in MorphoService.hs, but not in PGFService.hs
initFastCGI :: IO ()
initFastCGI = installSignalHandlers

loopFastCGI :: CGI CGIResult -> IO ()
loopFastCGI f = 
    do (do runOneFastCGI f
           exitIfToldTo
           restartIfModified) 
         `catchAborted` logError "Request aborted"
       loopFastCGI f
-}

-- Signal handling for FastCGI programs.


#ifndef mingw32_HOST_OS
installSignalHandlers :: IO ()
installSignalHandlers =
    do t <- myThreadId
       installHandler sigUSR1 (Catch gracefulExit) Nothing
       installHandler sigTERM (Catch gracelessExit) Nothing
       installHandler sigPIPE (Catch (requestAborted t)) Nothing
       return ()

requestAborted :: ThreadId -> IO ()
requestAborted t = throwTo t (ErrorCall "**aborted**")
  
gracelessExit :: IO ()
gracelessExit = do logError "Graceless exit"
                   exitWith ExitSuccess

gracefulExit :: IO ()
gracefulExit = 
    do logError "Graceful exit"
       writeIORef shouldExit True
#else
installSignalHandlers :: IO ()
installSignalHandlers = return ()
#endif

exitIfToldTo :: IO ()
exitIfToldTo = 
    do b <- readIORef shouldExit
       when b $ do logError "Exiting..."
                   exitWith ExitSuccess

{-# NOINLINE shouldExit #-}
shouldExit :: IORef Bool
shouldExit = unsafePerformIO $ newIORef False

catchAborted ::  IO a -> IO a -> IO a
catchAborted x y = x `catch` \e -> case e of
                                     ErrorCall "**aborted**" -> y
                                     _ -> throw e

-- Restart handling for FastCGI programs.

#ifndef mingw32_HOST_OS
{-# NOINLINE myModTimeRef #-}
myModTimeRef :: IORef EpochTime
myModTimeRef = unsafePerformIO (getProgModTime >>= newIORef)

-- FIXME: doesn't get directory
myProgPath :: IO FilePath
myProgPath = getProgName

getProgModTime :: IO EpochTime
getProgModTime = liftM modificationTime (myProgPath >>= getFileStatus)

needsRestart :: IO Bool
needsRestart = liftM2 (/=) (readIORef myModTimeRef) getProgModTime

exitIfModified :: IO ()
exitIfModified = 
    do restart <- needsRestart
       when restart $ exitWith ExitSuccess

restartIfModified :: IO ()
restartIfModified = 
    do restart <- needsRestart
       when restart $ do prog <- myProgPath
                         args <- getArgs
                         hPutStrLn stderr $ prog ++ " has been modified, restarting ..."
                         -- FIXME: setCurrentDirectory?
                         executeFile prog False args Nothing

#else
restartIfModified :: IO ()
restartIfModified = return ()
#endif

-- Logging

#ifndef mingw32_HOST_OS
logError :: String -> IO ()
logError s = hPutStrLn stderr s

stderrToFile :: FilePath -> IO ()
stderrToFile file =
    do let mode = ownerReadMode `unionFileModes` ownerWriteMode `unionFileModes` groupReadMode `unionFileModes` otherReadMode
       fileFd <- openFd file WriteOnly (Just mode) (defaultFileFlags { append = True })
       dupTo fileFd stdError
       return ()
#else
logError :: String -> IO ()
logError s = return ()

stderrToFile :: FilePath -> IO ()
stderrToFile s = return ()
#endif

-- * General CGI Error exception mechanism

data CGIError = CGIError { cgiErrorCode :: Int, cgiErrorMessage :: String, cgiErrorText :: [String] }
                deriving (Show,Typeable)

instance Exception CGIError where
  toException e = SomeException e
  fromException (SomeException e) = cast e

throwCGIError :: Int -> String -> [String] -> CGI a
throwCGIError c m t = throwCGI $ toException $ CGIError c m t

handleCGIErrors :: CGI CGIResult -> CGI CGIResult
handleCGIErrors x = x `catchCGI` \e -> case fromException e of
                                         Nothing -> throw e
                                         Just (CGIError c m t) -> outputError c m t

-- * General CGI and JSON stuff

outputJSONP :: JSON a => a -> CGI CGIResult
outputJSONP x = 
    do mc <- getInput "jsonp"
       let str = case mc of
                   Nothing -> encode x
                   Just c  -> c ++ "(" ++ encode x ++ ")"
       setHeader "Content-Type" "text/javascript; charset=utf-8"
       outputStrict $ UTF8.encodeString str

outputPNG :: BS.ByteString -> CGI CGIResult
outputPNG x = do
       setHeader "Content-Type" "image/png"
       outputFPS x

outputHTML :: String -> CGI CGIResult
outputHTML x = do
       setHeader "Content-Type" "text/html"
       outputStrict $ UTF8.encodeString x

outputStrict :: String -> CGI CGIResult
outputStrict x | x == x = output x
               | otherwise = fail "I am the pope."

-- * General utilities

splitBy :: (a -> Bool) -> [a] -> [[a]]
splitBy _ [] = [[]]
splitBy f list = case break f list of
                   (first,[]) -> [first]
                   (first,_:rest) -> first : splitBy f rest