38b9ebc5fdNoticed that Semigroup instance of Map is not suitable to use
for MapLog. For example, it behaved like this:
ghci> parseTrustLog "foo 1 timestamp=10\nfoo 2 timestamp=11" <> parseTrustLog "foo X timestamp=12"
fromList [(UUID "foo",LogEntry {changed = VectorClock 11s, value = SemiTrusted})]
Which was wrong, it lost the newer DeadTrusted value.
Luckily, nothing used that Semigroup when operating on a MapLog. And this
provides a safe instance.
Sponsored-by: Graham Spencer on Patreon
128 lines
3.9 KiB
Haskell
128 lines
3.9 KiB
Haskell
{- git-annex Map log
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-
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- This is used to store a Map, in a way that can be union merged.
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-
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- A line of the log will look like: "timestamp field value"
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-
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- The field names cannot contain whitespace.
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-
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- Copyright 2014-2023 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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module Logs.MapLog (
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module Logs.MapLog,
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VectorClock,
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currentVectorClock,
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) where
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import Common
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import Annex.VectorClock
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import Logs.Line
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import Utility.QuickCheck
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import qualified Data.ByteString.Lazy as L
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import qualified Data.Map.Strict as M
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import qualified Data.Attoparsec.ByteString as A
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import qualified Data.Attoparsec.ByteString.Lazy as AL
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import qualified Data.Attoparsec.ByteString.Char8 as A8
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import Data.ByteString.Builder
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import qualified Data.Semigroup as Sem
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import Prelude
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data LogEntry v = LogEntry
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{ changed :: VectorClock
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, value :: v
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} deriving (Eq, Show)
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instance Arbitrary v => Arbitrary (LogEntry v) where
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arbitrary = LogEntry <$> arbitrary <*> arbitrary
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newtype MapLog f v = MapLog (M.Map f (LogEntry v))
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deriving (Show, Eq)
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instance Ord f => Sem.Semigroup (MapLog f v)
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where
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a <> MapLog b = foldl' (\m (f, v) -> addMapLog f v m) a (M.toList b)
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instance Ord f => Monoid (MapLog f v)
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where
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mempty = MapLog M.empty
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fromMapLog :: MapLog f v -> M.Map f (LogEntry v)
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fromMapLog (MapLog m) = m
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buildMapLog :: (f -> Builder) -> (v -> Builder) -> MapLog f v -> Builder
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buildMapLog fieldbuilder valuebuilder (MapLog m) =
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mconcat $ map genline $ M.toList m
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where
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genline (f, LogEntry c v) =
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buildVectorClock c <> sp
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<> fieldbuilder f <> sp
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<> valuebuilder v <> nl
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sp = charUtf8 ' '
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nl = charUtf8 '\n'
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parseMapLog :: Ord f => A.Parser f -> A.Parser v -> L.ByteString -> MapLog f v
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parseMapLog fieldparser valueparser =
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parseMapLogWith (mapLogParser fieldparser valueparser)
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parseMapLogWith :: Ord f => A.Parser (MapLog f v) -> L.ByteString -> MapLog f v
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parseMapLogWith parser = fromMaybe (MapLog M.empty)
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. AL.maybeResult
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. AL.parse parser
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mapLogParser :: Ord f => A.Parser f -> A.Parser v -> A.Parser (MapLog f v)
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mapLogParser fieldparser valueparser = mapLogParser' $ do
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c <- vectorClockParser
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_ <- A8.char ' '
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w <- A8.takeTill (== ' ')
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f <- either fail return $
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A.parseOnly (fieldparser <* A.endOfInput) w
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_ <- A8.char ' '
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v <- valueparser
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A.endOfInput
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return (f, LogEntry c v)
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mapLogParser' :: Ord f => A.Parser (f, LogEntry v) -> A.Parser (MapLog f v)
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mapLogParser' p = MapLog . M.fromListWith best
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<$> parseLogLines p
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changeMapLog :: Ord f => CandidateVectorClock -> f -> v -> MapLog f v -> MapLog f v
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changeMapLog c f v (MapLog m) = MapLog (M.insert f (LogEntry c' v) m)
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where
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c' = case M.lookup f m of
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Nothing -> advanceVectorClock c []
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Just old -> advanceVectorClock c [changed old]
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{- Only add an LogEntry if it's newer (or at least as new as) than any
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- existing LogEntry for a field. -}
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addMapLog :: Ord f => f -> LogEntry v -> MapLog f v -> MapLog f v
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addMapLog f v (MapLog m) = MapLog (M.insertWith best f v m)
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filterMapLogWith :: (f -> LogEntry v -> Bool) -> MapLog f v -> MapLog f v
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filterMapLogWith f (MapLog m) = MapLog (M.filterWithKey f m)
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mapLogWithKey :: (f -> LogEntry v -> LogEntry v) -> MapLog f v -> MapLog f v
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mapLogWithKey f (MapLog m) = MapLog (M.mapWithKey f m)
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{- Converts a MapLog into a simple Map without the timestamp information.
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- This is a one-way trip, but useful for code that never needs to change
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- the log. -}
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simpleMap :: MapLog f v -> M.Map f v
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simpleMap (MapLog m) = M.map value m
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best :: LogEntry v -> LogEntry v -> LogEntry v
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best new old
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| changed old > changed new = old
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| otherwise = new
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prop_addMapLog_sane :: Bool
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prop_addMapLog_sane = newWins && newestWins
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where
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newWins = addMapLog "foo" (LogEntry (VectorClock 1) "new") l == l2
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newestWins = addMapLog "foo" (LogEntry (VectorClock 1) "newest") l2 /= l2
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l = MapLog (M.fromList [("foo", LogEntry (VectorClock 0) "old")])
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l2 = MapLog (M.fromList [("foo", LogEntry (VectorClock 1) "new")])
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