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{-# LANGUAGE OverloadedStrings, DeriveGeneric #-}
module SessionID (
SessionID,
mkSessionID,
sessionLogFile,
withSessionID,
sessionIDUrl,
) where
import Serialization
import System.FilePath
import System.IO
import System.Directory
import Network.Wai.Handler.Warp (Port)
import Network.WebSockets hiding (Message)
import qualified Data.Aeson
import Data.Maybe
import Data.List
import Data.UUID
import Data.UUID.V4
-- | 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)
instance ToJSON SessionID
instance FromJSON SessionID
instance WebSocketsData SessionID where
-- fromDataMessage = fromLazyByteString . fromDataMessage
fromLazyByteString b =
-- Down't trust a legal SessionID to be deserialized;
-- use smart constructor to verify it's legal.
let SessionID unverified = fromMaybe (error "bad SessionID serialization") (Data.Aeson.decode b)
in fromMaybe (error "illegal SessionID") (mkSessionID unverified)
toLazyByteString = Data.Aeson.encode
-- | 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 and return an open Handle to its log file.
--
-- A UUID is used, to avoid ever generating a SessionID that has been used
-- before.
withSessionID :: FilePath -> ((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 withFile f WriteMode $ \h -> a (h, sid)
type UrlString = String
sessionIDUrl :: SessionID -> String -> Port -> UrlString
sessionIDUrl (SessionID f) host port = "http://" ++ host ++ ":" ++ show port ++ "/" ++ f
|