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{- git-annex uuid-based logs
-
- This is used to store information about a UUID in a way that can
- be union merged.
-
- A line of the log will look like: "UUID[ INFO[ timestamp=foo]]"
- The timestamp is last for backwards compatability reasons,
- and may not be present on old log lines.
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Logs.UUIDBased (
Log,
LogEntry(..),
TimeStamp(..),
parseLog,
showLog,
changeLog,
addLog,
simpleMap,
prop_TimeStamp_sane,
prop_addLog_sane,
) where
import qualified Data.Map as M
import Data.Time.Clock.POSIX
import Data.Time
import System.Locale
import Common
import Types.UUID
data TimeStamp = Unknown | Date POSIXTime
deriving (Eq, Ord, Show)
data LogEntry a = LogEntry
{ changed :: TimeStamp
, value :: a
} deriving (Eq, Show)
type Log a = M.Map UUID (LogEntry a)
tskey :: String
tskey = "timestamp="
showLog :: (a -> String) -> Log a -> String
showLog shower = unlines . map showpair . M.toList
where
showpair (k, LogEntry (Date p) v) =
unwords [fromUUID k, shower v, tskey ++ show p]
showpair (k, LogEntry Unknown v) =
unwords [fromUUID k, shower v]
parseLog :: (String -> Maybe a) -> String -> Log a
parseLog parser = M.fromListWith best . mapMaybe parse . lines
where
parse line
| null ws = Nothing
| otherwise = parser (unwords info) >>= makepair
where
makepair v = Just (toUUID u, LogEntry ts v)
ws = words line
u = Prelude.head ws
t = Prelude.last ws
ts
| tskey `isPrefixOf` t =
pdate $ drop 1 $ dropWhile (/= '=') t
| otherwise = Unknown
info
| ts == Unknown = drop 1 ws
| otherwise = drop 1 $ beginning ws
pdate s = case parseTime defaultTimeLocale "%s%Qs" s of
Nothing -> Unknown
Just d -> Date $ utcTimeToPOSIXSeconds d
changeLog :: POSIXTime -> UUID -> a -> Log a -> Log a
changeLog t u v = M.insert u $ LogEntry (Date t) v
{- Only add an LogEntry if it's newer (or at least as new as) than any
- existing LogEntry for a UUID. -}
addLog :: UUID -> LogEntry a -> Log a -> Log a
addLog = M.insertWith' best
{- Converts a Log into a simple Map without the timestamp information.
- This is a one-way trip, but useful for code that never needs to change
- the log. -}
simpleMap :: Log a -> M.Map UUID a
simpleMap = M.map value
best :: LogEntry a -> LogEntry a -> LogEntry a
best new old
| changed old > changed new = old
| otherwise = new
-- Unknown is oldest.
prop_TimeStamp_sane :: Bool
prop_TimeStamp_sane = Unknown < Date 1
prop_addLog_sane :: Bool
prop_addLog_sane = newWins && newestWins
where
newWins = addLog (UUID "foo") (LogEntry (Date 1) "new") l == l2
newestWins = addLog (UUID "foo") (LogEntry (Date 1) "newest") l2 /= l2
l = M.fromList [(UUID "foo", LogEntry (Date 0) "old")]
l2 = M.fromList [(UUID "foo", LogEntry (Date 1) "new")]
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