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{- Copyright 2017 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
{-# LANGUAGE OverloadedStrings, DeriveGeneric #-}
module SessionID (
SessionID,
mkSessionID,
sessionLogFile,
withSessionID,
sessionIDUrl,
) where
import JSON
import System.FilePath
import System.IO
import System.Directory
import Data.List
import Data.UUID
import Data.UUID.V4
import Network.URI
import Control.Concurrent.STM
import Control.Exception
-- | A SessionID is the base name of the log file to use,
-- and may not contain any path information.
newtype SessionID = SessionID FilePath
deriving (Show, Eq, Ord, Generic)
-- | Custom JSON deserialization so we can check smart constructor
-- to verify it's legal.
instance FromJSON SessionID where
parseJSON v = verify =<< genericParseJSON defaultOptions v
where
verify (SessionID unverified) =
maybe (fail "illegal SessionID") return
(mkSessionID unverified)
instance ToJSON SessionID
-- | Smart constructor that enforces legal SessionID contents.
--
-- The passed String can either be the bare SessionID, or it can be an URL
-- which ends with the SessionID.
mkSessionID :: String -> Maybe SessionID
mkSessionID s
| "http" `isPrefixOf` s = Just $ SessionID $ takeFileName s
| takeFileName s == s = Just $ SessionID s
| otherwise = Nothing
sessionLogFile :: FilePath -> SessionID -> FilePath
sessionLogFile dir (SessionID f) = dir </> "debug-me." ++ f ++ ".log"
-- | Allocate a new SessionID open a Handle to its log file.
--
-- A UUID is used, to avoid ever generating a SessionID that has been used
-- before.
withSessionID :: FilePath -> ((TVar Handle, SessionID) -> IO a) -> IO a
withSessionID dir a = do
createDirectoryIfMissing False dir
sid <- SessionID . toString <$> nextRandom
let f = sessionLogFile dir sid
-- File should not already exist, but just in case we get
-- spectacularly unlucky (or the RNG is broken..),
-- avoid overwriting a log, and try again.
exists <- doesFileExist f
if exists
then withSessionID dir a
else bracket (setup f) cleanup (go sid)
where
setup f = do
h <- openFile f WriteMode
hv <- newTVarIO h
return hv
cleanup hv = hClose =<< atomically (readTVar hv)
go sid hv = a (hv, sid)
sessionIDUrl :: SessionID -> URI -> URI
sessionIDUrl (SessionID f) serverurl = serverurl { uriPath = "/" ++ f }
|
