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|
{- git-annex location log
-
- git-annex keeps track of on which repository it last saw a file's content.
- 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 file's content.
-
- Location tracking information is stored in `.git-annex/filename.log`.
- Repositories record their name and the date when they --get or --drop
- a file's content. (Git is configured to use a union merge for this file,
- so the lines may be in arbitrary order, but it will never conflict.)
-
- A line of the log will look like: "date N reponame"
- Where N=1 when the repo has the file, and 0 otherwise.
-
- TOOD: compact logs, by storing only current presence infomation when
- writing them.
-
- TODO: use ByteString
-}
module LocationLog where
import Data.DateTime
import System.IO
import System.Directory
import Data.Char
import GitRepo
import Utility
data LogStatus = FilePresent | FileMissing | Undefined
deriving (Eq)
instance Show LogStatus where
show FilePresent = "1"
show FileMissing = "0"
show Undefined = "undefined"
instance Read LogStatus where
readsPrec _ "1" = [(FilePresent, "")]
readsPrec _ "0" = [(FileMissing, "")]
readsPrec _ _ = [(Undefined, "")]
data LogLine = LogLine {
date :: DateTime,
status :: LogStatus,
repo :: String
} deriving (Eq)
instance Show LogLine where
show (LogLine date status repo) = unwords
[(show (toSeconds date)), (show status), repo]
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 && all isDigit date)
then [((LogLine (fromSeconds $ read date) status repo), "")]
else [((LogLine (fromSeconds 0) Undefined ""), "")]
where
w = words string
date = w !! 0
status = read $ w !! 1
repo = unwords $ drop 2 w
{- Reads a log file.
- Note that the LogLines returned may be in any order. -}
readLog :: String -> 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 -}
writeLog :: String -> LogLine -> IO ()
writeLog file line = do
createDirectoryIfMissing True (parentDir file)
withFileLocked file AppendMode $ \h ->
hPutStrLn h $ show line
{- Generates a new LogLine with the current date. -}
logNow :: LogStatus -> String -> IO LogLine
logNow status repo = do
now <- getCurrentTime
return $ LogLine now status repo
{- Returns the filename of the log file for a given annexed file. -}
logFile :: String -> IO String
logFile annexedFile = do
repo <- repoTop
return $ (gitStateDir repo) ++
(gitRelative repo annexedFile) ++ ".log"
{- Returns a list of repositories that, according to the log, have
- the content of a file -}
fileLocations :: String -> IO [String]
fileLocations file = do
log <- logFile file
lines <- readLog log
return $ map repo (filterPresent lines)
{- Filters the list of LogLines to find repositories where the file
- is (or should still be) present. -}
filterPresent :: [LogLine] -> [LogLine]
filterPresent lines = error "unimplimented" -- TODO
|
