git-annex/Logs/Transitions.hs
Joey Hess bfc9039ead
convert git-annex branch access to ByteStrings and Builders
Most of the individual logs are not converted yet, only presense logs
have an efficient ByteString Builder implemented so far. The rest
convert to and from String.
2019-01-03 13:21:48 -04:00

87 lines
2.8 KiB
Haskell

{- git-annex transitions log
-
- This is used to record transitions that have been performed on the
- git-annex branch, and when the transition was first started.
-
- We can quickly detect when the local branch has already had an transition
- done that is listed in the remote branch by checking that the local
- branch contains the same transition, with the same or newer start time.
-
- Copyright 2013 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Logs.Transitions where
import Annex.Common
import Annex.VectorClock
import Logs.Line
import qualified Data.Set as S
import qualified Data.ByteString.Lazy as L
transitionsLog :: FilePath
transitionsLog = "transitions.log"
data Transition
= ForgetGitHistory
| ForgetDeadRemotes
deriving (Show, Ord, Eq, Read)
data TransitionLine = TransitionLine
{ transitionStarted :: VectorClock
, transition :: Transition
} deriving (Ord, Eq)
type Transitions = S.Set TransitionLine
describeTransition :: Transition -> String
describeTransition ForgetGitHistory = "forget git history"
describeTransition ForgetDeadRemotes = "forget dead remotes"
noTransitions :: Transitions
noTransitions = S.empty
addTransition :: VectorClock -> Transition -> Transitions -> Transitions
addTransition c t = S.insert $ TransitionLine c t
showTransitions :: Transitions -> String
showTransitions = unlines . map showTransitionLine . S.elems
{- If the log contains new transitions we don't support, returns Nothing. -}
parseTransitions :: String -> Maybe Transitions
parseTransitions = check . map parseTransitionLine . splitLines
where
check l
| all isJust l = Just $ S.fromList $ catMaybes l
| otherwise = Nothing
parseTransitionsStrictly :: String -> String -> Transitions
parseTransitionsStrictly source = fromMaybe badsource . parseTransitions
where
badsource = giveup $ "unknown transitions listed in " ++ source ++ "; upgrade git-annex!"
showTransitionLine :: TransitionLine -> String
showTransitionLine (TransitionLine c t) = unwords [show t, formatVectorClock c]
parseTransitionLine :: String -> Maybe TransitionLine
parseTransitionLine s = TransitionLine
<$> parseVectorClock cs
<*> readish ts
where
ws = words s
ts = Prelude.head ws
cs = unwords $ Prelude.tail ws
combineTransitions :: [Transitions] -> Transitions
combineTransitions = S.unions
transitionList :: Transitions -> [Transition]
transitionList = nub . map transition . S.elems
{- Typically ran with Annex.Branch.change, but we can't import Annex.Branch
- here since it depends on this module. -}
recordTransitions :: (FilePath -> (L.ByteString -> L.ByteString) -> Annex ()) -> Transitions -> Annex ()
recordTransitions changer t = changer transitionsLog $
encodeBL . showTransitions . S.union t . parseTransitionsStrictly "local" . decodeBL