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|
{- git-annex location log
-
- git-annex keeps track of on which repository it last saw a value.
- This can be useful when using it for archiving with offline storage.
- When you indicate you --want a file, git-annex will tell you which
- repositories have the value.
-
- Location tracking information is stored in `.git-annex/key.log`.
- Repositories record their UUID and the date when they --get or --drop
- a value.
-
- A line of the log will look like: "date N UUID"
- Where N=1 when the repo has the file, and 0 otherwise.
-
- Git is configured to use a union merge for this file,
- so the lines may be in arbitrary order, but it will never conflict.
-}
module LocationLog (
LogStatus(..),
logChange,
keyLocations
) where
import Data.Time.Clock.POSIX
import Data.Time
import System.Locale
import qualified Data.Map as Map
import System.IO
import System.Directory
import Data.Char
import qualified GitRepo as Git
import Utility
import UUID
import AbstractTypes
import Locations
data LogLine = LogLine {
date :: POSIXTime,
status :: LogStatus,
uuid :: UUID
} deriving (Eq)
data LogStatus = ValuePresent | ValueMissing | Undefined
deriving (Eq)
instance Show LogStatus where
show ValuePresent = "1"
show ValueMissing = "0"
show Undefined = "undefined"
instance Read LogStatus where
readsPrec _ "1" = [(ValuePresent, "")]
readsPrec _ "0" = [(ValueMissing, "")]
readsPrec _ _ = [(Undefined, "")]
instance Show LogLine where
show (LogLine date status uuid) = unwords
[(show date), (show status), uuid]
instance Read LogLine where
-- This parser is robust in that even unparsable log lines are
-- read without an exception being thrown.
-- Such lines have a status of Undefined.
readsPrec _ string =
if (length w == 3)
then case (pdate) of
Just v -> good v
Nothing -> undefined
else undefined
where
w = words string
date = w !! 0
status = read $ w !! 1
uuid = w !! 2
pdate = (parseTime defaultTimeLocale "%s%Qs" date) :: Maybe UTCTime
good v = ret $ LogLine (utcTimeToPOSIXSeconds v) status uuid
undefined = ret $ LogLine (0) Undefined ""
ret v = [(v, "")]
{- Log a change in the presence of a key's value in a repository,
- and return the log filename. -}
logChange :: Git.Repo -> Key -> UUID -> LogStatus -> IO FilePath
logChange repo key uuid status = do
log <- logNow status uuid
ls <- readLog logfile
writeLog logfile (compactLog $ log:ls)
return logfile
where
logfile = logFile repo key
{- Reads a log file.
- Note that the LogLines returned may be in any order. -}
readLog :: FilePath -> IO [LogLine]
readLog file = do
exists <- doesFileExist file
if exists
then do
s <- withFileLocked file ReadMode $ \h ->
hGetContentsStrict h
-- filter out any unparsable lines
return $ filter (\l -> (status l) /= Undefined )
$ map read $ lines s
else do
return []
{- Adds a LogLine to a log file -}
appendLog :: FilePath -> LogLine -> IO ()
appendLog file line = do
createDirectoryIfMissing True (parentDir file)
withFileLocked file AppendMode $ \h ->
hPutStrLn h $ show line
-- TODO git add log
{- Writes a set of lines to a log file -}
writeLog :: FilePath -> [LogLine] -> IO ()
writeLog file lines = do
createDirectoryIfMissing True (parentDir file)
withFileLocked file WriteMode $ \h ->
hPutStr h $ unlines $ map show lines
{- Generates a new LogLine with the current date. -}
logNow :: LogStatus -> UUID -> IO LogLine
logNow status uuid = do
now <- getPOSIXTime
return $ LogLine now status uuid
{- Returns the filename of the log file for a given key. -}
logFile :: Git.Repo -> Key -> String
logFile repo key =
(gitStateDir repo) ++ (Git.relative repo (keyFile key)) ++ ".log"
{- Returns a list of repository UUIDs that, according to the log, have
- the value of a key. -}
keyLocations :: Git.Repo -> Key -> IO [UUID]
keyLocations thisrepo key = do
lines <- readLog $ logFile thisrepo key
return $ map uuid (filterPresent lines)
{- Filters the list of LogLines to find ones where the value
- is (or should still be) present. -}
filterPresent :: [LogLine] -> [LogLine]
filterPresent lines = filter (\l -> ValuePresent == status l) $ compactLog lines
{- Compacts a set of logs, returning a subset that contains the current
- status. -}
compactLog :: [LogLine] -> [LogLine]
compactLog lines = compactLog' Map.empty lines
compactLog' map [] = Map.elems map
compactLog' map (l:ls) = compactLog' (mapLog map l) ls
{- Inserts a log into a map of logs, if the log has better (ie, newer)
- information about a repo than the other logs in the map -}
mapLog map log =
if (better)
then Map.insert (uuid log) log map
else map
where
better = case (Map.lookup (uuid log) map) of
Just l -> (date l <= date log)
Nothing -> True
|
