git-annex/Logs/UUID.hs

{- git-annex uuids
 -
 - Each git repository used by git-annex has an annex.uuid setting that
 - uniquely identifies that repository.
 -
 - UUIDs of remotes are cached in git config, using keys named
 - remote.<name>.annex-uuid
 -
 - uuid.log stores a list of known uuids, and their descriptions.
 -
 - Copyright 2010-2012 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Logs.UUID (
	uuidLog,
	describeUUID,
	recordUUID,
	uuidMap,
	uuidMapLoad
) where

import Types.UUID
import Annex.Common
import Annex.VectorClock
import qualified Annex
import qualified Annex.Branch
import Logs
import Logs.UUIDBased
import qualified Annex.UUID

import qualified Data.Map as M

{- Records a description for a uuid in the log. -}
describeUUID :: UUID -> String -> Annex ()
describeUUID uuid desc = do
	c <- liftIO currentVectorClock
	Annex.Branch.change uuidLog $
		showLog id . changeLog c uuid desc . fixBadUUID . parseLog Just

{- Temporarily here to fix badly formatted uuid logs generated by
 - versions 3.20111105 and 3.20111025. 
 -
 - Those logs contain entries with the UUID and description flipped.
 - Due to parsing, if the description is multiword, only the first
 - will be taken to be the UUID. So, if the UUID of an entry does
 - not look like a UUID, and the last word of the description does,
 - flip them back.
 -}
fixBadUUID :: Log String -> Log String
fixBadUUID = M.fromList . map fixup . M.toList
  where
	fixup (k, v)
		| isbad = (fixeduuid, LogEntry (newertime v) fixedvalue)
		| otherwise = (k, v)
	  where
		kuuid = fromUUID k
		isbad = not (isuuid kuuid) && not (null ws) && isuuid lastword
		ws = words $ value v
		lastword = Prelude.last ws
		fixeduuid = toUUID lastword
		fixedvalue = unwords $ kuuid: Prelude.init ws
	-- For the fixed line to take precidence, it should be
	-- slightly newer, but only slightly.
	newertime (LogEntry (VectorClock c) _) = VectorClock (c + minimumPOSIXTimeSlice)
	newertime (LogEntry Unknown _) = VectorClock minimumPOSIXTimeSlice
	minimumPOSIXTimeSlice = 0.000001
	isuuid s = length s == 36 && length (splitc '-' s) == 5

{- Records the uuid in the log, if it's not already there. -}
recordUUID :: UUID -> Annex ()
recordUUID u = go . M.lookup u =<< uuidMap 
  where
	go (Just "") = set
	go Nothing = set
	go _ = noop
	set = describeUUID u ""

{- The map is cached for speed. -}
uuidMap :: Annex UUIDMap
uuidMap = maybe uuidMapLoad return =<< Annex.getState Annex.uuidmap

{- Read the uuidLog into a simple Map.
 -
 - The UUID of the current repository is included explicitly, since
 - it may not have been described and so otherwise would not appear. -}
uuidMapLoad :: Annex UUIDMap
uuidMapLoad = do
	m <- (simpleMap . parseLog Just) <$> Annex.Branch.get uuidLog
	u <- Annex.UUID.getUUID
	let m' = M.insertWith' preferold u "" m
	Annex.changeState $ \s -> s { Annex.uuidmap = Just m' }
	return m'
  where
	preferold = flip const