module SessionID (SessionID, mkSessionID, sessionLogFile, withSessionID) where

import System.FilePath
import Data.Text
import System.IO

-- | 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)

-- | Smart constructor that enforces security requirements.
mkSessionID :: Text -> Maybe SessionID
mkSessionID t = 
	let f = unpack t
	in if takeFileName f == f
		then Just (SessionID f)
		else 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.
withSessionID :: FilePath -> ((Handle, SessionID) -> IO a) -> IO a
withSessionID dir a = do
	-- TODO find an unused log file and open it
	let sid = SessionID "1"
	withFile "debug-me-server.log" WriteMode $ \h -> a (h, sid)