82 lines
2.4 KiB
Haskell
82 lines
2.4 KiB
Haskell
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{- 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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- Copyright 2014 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Logs.MapLog where
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import qualified Data.Map as M
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import Data.Time.Clock.POSIX
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import Data.Time
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import System.Locale
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import Common
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data TimeStamp = Unknown | Date POSIXTime
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deriving (Eq, Ord, Show)
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data LogEntry v = LogEntry
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{ changed :: TimeStamp
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, value :: v
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} deriving (Eq, Show)
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type MapLog f v = M.Map f (LogEntry v)
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showMapLog :: (f -> String) -> (v -> String) -> MapLog f v -> String
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showMapLog fieldshower valueshower = unlines . map showpair . M.toList
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where
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showpair (f, LogEntry (Date p) v) =
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unwords [show p, fieldshower f, valueshower v]
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showpair (f, LogEntry Unknown v) =
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unwords ["0", fieldshower f, valueshower v]
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parseMapLog :: Ord f => (String -> Maybe f) -> (String -> Maybe v) -> String -> MapLog f v
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parseMapLog fieldparser valueparser = M.fromListWith best . mapMaybe parse . lines
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where
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parse line = do
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let (ts, rest) = splitword line
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(sf, sv) = splitword rest
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date <- Date . utcTimeToPOSIXSeconds <$> parseTime defaultTimeLocale "%s%Qs" ts
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f <- fieldparser sf
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v <- valueparser sv
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Just (f, LogEntry date v)
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splitword = separate (== ' ')
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changeMapLog :: Ord f => POSIXTime -> f -> v -> MapLog f v -> MapLog f v
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changeMapLog t f v = M.insert f $ LogEntry (Date t) v
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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 = M.insertWith' best
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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 = M.map value
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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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-- Unknown is oldest.
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prop_TimeStamp_sane :: Bool
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prop_TimeStamp_sane = Unknown < Date 1
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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 (Date 1) "new") l == l2
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newestWins = addMapLog ("foo") (LogEntry (Date 1) "newest") l2 /= l2
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l = M.fromList [("foo", LogEntry (Date 0) "old")]
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l2 = M.fromList [("foo", LogEntry (Date 1) "new")]
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