1 files changed, 28 insertions, 0 deletions
diff --git a/SessionID.hs b/SessionID.hs
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+++ b/SessionID.hs
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+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)