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|
{- git-annex presence log
-
- This is used to store presence information in the git-annex branch in
- a way that can be union merged.
-
- A line of the log will look like: "date N INFO"
- Where N=1 when the INFO is present, and 0 otherwise.
-
- Copyright 2010-2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Logs.Presence (
LogStatus(..),
addLog,
readLog,
parseLog,
showLog,
logNow,
compactLog,
currentLog,
LogLine
) where
import Data.Time.Clock.POSIX
import Data.Time
import System.Locale
import qualified Data.Map as M
import Common.Annex
import qualified Annex.Branch
data LogLine = LogLine {
date :: POSIXTime,
status :: LogStatus,
info :: String
} deriving (Eq)
data LogStatus = InfoPresent | InfoMissing
deriving (Eq)
addLog :: FilePath -> LogLine -> Annex ()
addLog file line = Annex.Branch.change file $ \s ->
showLog $ compactLog (line : parseLog s)
{- Reads a log file.
- Note that the LogLines returned may be in any order. -}
readLog :: FilePath -> Annex [LogLine]
readLog file = parseLog <$> Annex.Branch.get file
{- Parses a log file. Unparseable lines are ignored. -}
parseLog :: String -> [LogLine]
parseLog = mapMaybe (parseline . words) . lines
where
parseline (a:b:c:_) = do
d <- parseTime defaultTimeLocale "%s%Qs" a
s <- parsestatus b
Just $ LogLine (utcTimeToPOSIXSeconds d) s c
parseline _ = Nothing
parsestatus "1" = Just InfoPresent
parsestatus "0" = Just InfoMissing
parsestatus _ = Nothing
{- Generates a log file. -}
showLog :: [LogLine] -> String
showLog = unlines . map genline
where
genline (LogLine d s i) = unwords [show d, genstatus s, i]
genstatus InfoPresent = "1"
genstatus InfoMissing = "0"
{- Generates a new LogLine with the current date. -}
logNow :: LogStatus -> String -> Annex LogLine
logNow s i = do
now <- liftIO getPOSIXTime
return $ LogLine now s i
{- Reads a log and returns only the info that is still in effect. -}
currentLog :: FilePath -> Annex [String]
currentLog file = map info . filterPresent <$> readLog file
{- Returns the info from LogLines that are in effect. -}
filterPresent :: [LogLine] -> [LogLine]
filterPresent = filter (\l -> InfoPresent == status l) . compactLog
{- Compacts a set of logs, returning a subset that contains the current
- status. -}
compactLog :: [LogLine] -> [LogLine]
compactLog = M.elems . foldr mapLog M.empty
type LogMap = M.Map String LogLine
{- Inserts a log into a map of logs, if the log has better (ie, newer)
- information than the other logs in the map -}
mapLog :: LogLine -> LogMap -> LogMap
mapLog l m =
if better
then M.insert i l m
else m
where
better = maybe True newer $ M.lookup i m
newer l' = date l' <= date l
i = info l
|
