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|
{- git-annex metadata log, pure operations
-
- Copyright 2014-2018 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Logs.MetaData.Pure (
Log,
LogEntry(..),
parseLog,
buildLog,
logToCurrentMetaData,
simplifyLog,
filterRemoteMetaData,
filterOutEmpty,
) where
import Types.MetaData
import Logs.SingleValue.Pure
import Types.UUID
import qualified Data.Set as S
import qualified Data.Map.Strict as M
instance SingleValueSerializable MetaData where
serialize = Types.MetaData.serialize
deserialize = Types.MetaData.deserialize
logToCurrentMetaData :: [LogEntry MetaData] -> MetaData
logToCurrentMetaData = currentMetaData . combineMetaData . map value
{- Simplify a log, removing historical values that are no longer
- needed.
-
- This is not as simple as just making a single log line with the newest
- state of all metadata. Consider this case:
-
- We have:
-
- 100 foo +x bar +y
- 200 foo -x
-
- An unmerged remote has:
-
- 150 bar -y baz +w
-
- If what we have were simplified to "200 foo -x bar +y" then when the line
- from the remote became available, it would be older than the simplified
- line, and its change to bar would not take effect. That is wrong.
-
- Instead, simplify it to:
-
- 100 bar +y
- 200 foo -x
-
- (Note that this ends up with the same number of lines as the
- unsimplified version, so there's really no point in updating
- the log to this version. Doing so would only add data to git,
- with little benefit.)
-
- Now merging with the remote yields:
-
- 100 bar +y
- 150 bar -y baz +w
- 200 foo -x
-
- Simplifying again:
-
- 150 bar +z baz +w
- 200 foo -x
-}
simplifyLog :: Log MetaData -> Log MetaData
simplifyLog s = case sl of
(newest:rest) ->
let sl' = go [newest] (value newest) rest
in if length sl' < length sl
then S.fromList sl'
else s
_ -> s
where
sl = S.toDescList s
go c _ [] = c
go c newer (l:ls)
| unique == emptyMetaData = go c newer ls
| otherwise = go (l { value = unique } : c)
(unionMetaData unique newer) ls
where
older = value l
unique = older `differenceMetaData` newer
{- Filters per-remote metadata on the basis of UUID.
-
- Note that the LogEntry's clock is left the same, so this should not be
- used except for in a transition.
-}
filterRemoteMetaData :: (UUID -> Bool) -> Log MetaData -> Log MetaData
filterRemoteMetaData p = S.map go
where
go l@(LogEntry { value = MetaData m }) =
l { value = MetaData $ M.filterWithKey fil m }
fil f _v = case splitRemoteMetaDataField f of
Just (u, _) -> p u
Nothing -> True
{- Filters out log lines that are empty. -}
filterOutEmpty :: Log MetaData -> Log MetaData
filterOutEmpty = S.filter $ \l -> value l /= emptyMetaData
|
