git-annex/Annex/Locations.hs

{- git-annex file locations
 -
 - Copyright 2010-2019 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE OverloadedStrings #-}

module Annex.Locations (
	keyFile,
	keyFile',
	fileKey,
	fileKey',
	keyPaths,
	keyPath,
	annexDir,
	objectDir,
	gitAnnexLocation,
	gitAnnexLocationDepth,
	gitAnnexLink,
	gitAnnexLinkCanonical,
	gitAnnexContentLock,
	gitAnnexMapping,
	gitAnnexInodeCache,
	gitAnnexInodeSentinal,
	gitAnnexInodeSentinalCache,
	annexLocations,
	gitAnnexDir,
	gitAnnexObjectDir,
	gitAnnexTmpOtherDir,
	gitAnnexTmpOtherLock,
	gitAnnexTmpOtherDirOld,
	gitAnnexTmpWatcherDir,
	gitAnnexTmpObjectDir,
	gitAnnexTmpObjectLocation,
	gitAnnexTmpWorkDir,
	gitAnnexBadDir,
	gitAnnexBadLocation,
	gitAnnexUnusedLog,
	gitAnnexKeysDb,
	gitAnnexKeysDbLock,
	gitAnnexKeysDbIndexCache,
	gitAnnexFsckState,
	gitAnnexFsckDbDir,
	gitAnnexFsckDbLock,
	gitAnnexFsckResultsLog,
	gitAnnexSmudgeLog,
	gitAnnexSmudgeLock,
	gitAnnexExportDbDir,
	gitAnnexExportLock,
	gitAnnexExportUpdateLock,
	gitAnnexExportExcludeLog,
	gitAnnexContentIdentifierDbDir,
	gitAnnexContentIdentifierLock,
	gitAnnexScheduleState,
	gitAnnexTransferDir,
	gitAnnexCredsDir,
	gitAnnexWebCertificate,
	gitAnnexWebPrivKey,
	gitAnnexFeedStateDir,
	gitAnnexFeedState,
	gitAnnexMergeDir,
	gitAnnexJournalDir,
	gitAnnexJournalLock,
	gitAnnexGitQueueLock,
	gitAnnexPreCommitLock,
	gitAnnexMergeLock,
	gitAnnexIndex,
	gitAnnexIndexStatus,
	gitAnnexViewIndex,
	gitAnnexViewLog,
	gitAnnexMergedRefs,
	gitAnnexIgnoredRefs,
	gitAnnexPidFile,
	gitAnnexPidLockFile,
	gitAnnexDaemonStatusFile,
	gitAnnexLogFile,
	gitAnnexFuzzTestLogFile,
	gitAnnexHtmlShim,
	gitAnnexUrlFile,
	gitAnnexTmpCfgFile,
	gitAnnexSshDir,
	gitAnnexRemotesDir,
	gitAnnexAssistantDefaultDir,
	HashLevels(..),
	hashDirMixed,
	hashDirLower,
	preSanitizeKeyName,
	reSanitizeKeyName,
) where

import Data.Char
import Data.Default
import qualified Data.ByteString.Char8 as S8

import Common
import Key
import Types.UUID
import Types.GitConfig
import Types.Difference
import qualified Git
import qualified Git.Types as Git
import Git.FilePath
import Annex.DirHashes
import Annex.Fixup

{- Conventions:
 -
 - Functions ending in "Dir" should always return values ending with a
 - trailing path separator. Most code does not rely on that, but a few
 - things do. 
 -
 - Everything else should not end in a trailing path sepatator. 
 -
 - Only functions (with names starting with "git") that build a path
 - based on a git repository should return full path relative to the git
 - repository. Everything else returns path segments.
 -}

{- The directory git annex uses for local state, relative to the .git
 - directory -}
annexDir :: FilePath
annexDir = addTrailingPathSeparator "annex"

{- The directory git annex uses for locally available object content,
 - relative to the .git directory -}
objectDir :: FilePath
objectDir = addTrailingPathSeparator $ annexDir </> "objects"

{- Annexed file's possible locations relative to the .git directory.
 - There are two different possibilities, using different hashes.
 -
 - Also, some repositories have a Difference in hash directory depth.
 -}
annexLocations :: GitConfig -> Key -> [FilePath]
annexLocations config key = map (annexLocation config key) dirHashes

annexLocation :: GitConfig -> Key -> (HashLevels -> Hasher) -> FilePath
annexLocation config key hasher = objectDir </> keyPath key (hasher $ objectHashLevels config)

{- Number of subdirectories from the gitAnnexObjectDir
 - to the gitAnnexLocation. -}
gitAnnexLocationDepth :: GitConfig -> Int
gitAnnexLocationDepth config = hashlevels + 1
  where
	HashLevels hashlevels = objectHashLevels config

{- Annexed object's location in a repository.
 -
 - When there are multiple possible locations, returns the one where the
 - file is actually present.
 -
 - When the file is not present, returns the location where the file should
 - be stored.
 -
 - This does not take direct mode into account, so in direct mode it is not
 - the actual location of the file's content.
 -}
gitAnnexLocation :: Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexLocation key r config = gitAnnexLocation' key r config (annexCrippledFileSystem config) (coreSymlinks config) doesFileExist (Git.localGitDir r)
gitAnnexLocation' :: Key -> Git.Repo -> GitConfig -> Bool -> Bool -> (FilePath -> IO Bool) -> FilePath -> IO FilePath
gitAnnexLocation' key r config crippled symlinkssupported checker gitdir
	{- Bare repositories default to hashDirLower for new
	 - content, as it's more portable. But check all locations. -}
	| Git.repoIsLocalBare r = checkall
	| hasDifference ObjectHashLower (annexDifferences config) = 
		only hashDirLower
	{- Repositories on crippled filesystems use hashDirLower
	 - for new content, unless symlinks are supported too.
	 - Then hashDirMixed is used. But, the content could be
	 - in either location so check both. -}
	| crippled = if symlinkssupported
		then check $ map inrepo $ reverse $ annexLocations config key
		else checkall
	{- Regular repositories only use hashDirMixed, so
	 - don't need to do any work to check if the file is
	 - present. -}
	| otherwise = only hashDirMixed
  where
	only = return . inrepo . annexLocation config key
	checkall = check $ map inrepo $ annexLocations config key

	inrepo d = gitdir </> d
	check locs@(l:_) = fromMaybe l <$> firstM checker locs
	check [] = error "internal"

{- Calculates a symlink target to link a file to an annexed object. -}
gitAnnexLink :: FilePath -> Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexLink file key r config = do
	currdir <- getCurrentDirectory
	let absfile = absNormPathUnix currdir file
	let gitdir = getgitdir currdir
	loc <- gitAnnexLocation' key r config False False (\_ -> return True) gitdir
	toInternalGitPath <$> relPathDirToFile (parentDir absfile) loc
  where
	getgitdir currdir
		{- This special case is for git submodules on filesystems not
		 - supporting symlinks; generate link target that will
		 - work portably. -}
		| not (coreSymlinks config) && needsSubmoduleFixup r =
			absNormPathUnix currdir $ Git.repoPath r </> ".git"
		| otherwise = Git.localGitDir r
	absNormPathUnix d p = fromRawFilePath $ toInternalGitPath $ toRawFilePath $
		absPathFrom
			(fromRawFilePath $ toInternalGitPath $ toRawFilePath d)
			(fromRawFilePath $ toInternalGitPath $ toRawFilePath p)

{- Calculates a symlink target as would be used in a typical git
 - repository, with .git in the top of the work tree. -}
gitAnnexLinkCanonical :: FilePath -> Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexLinkCanonical file key r config = gitAnnexLink file key r' config'
  where
	r' = case r of
		Git.Repo { Git.location = l@Git.Local { Git.worktree = Just wt } } ->
			r { Git.location = l { Git.gitdir = wt </> ".git" } }
		_ -> r
	config' = config
		{ annexCrippledFileSystem = False
		, coreSymlinks = True
		}

{- File used to lock a key's content. -}
gitAnnexContentLock :: Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexContentLock key r config = do
	loc <- gitAnnexLocation key r config
	return $ loc ++ ".lck"

{- File that maps from a key to the file(s) in the git repository.
 - Used in direct mode. -}
gitAnnexMapping :: Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexMapping key r config = do
	loc <- gitAnnexLocation key r config
	return $ loc ++ ".map"

{- File that caches information about a key's content, used to determine
 - if a file has changed.
 - Used in direct mode. -}
gitAnnexInodeCache :: Key -> Git.Repo -> GitConfig -> IO FilePath
gitAnnexInodeCache key r config  = do
	loc <- gitAnnexLocation key r config
	return $ loc ++ ".cache"

gitAnnexInodeSentinal :: Git.Repo -> FilePath
gitAnnexInodeSentinal r = gitAnnexDir r </> "sentinal"

gitAnnexInodeSentinalCache :: Git.Repo -> FilePath
gitAnnexInodeSentinalCache r = gitAnnexInodeSentinal r ++ ".cache"

{- The annex directory of a repository. -}
gitAnnexDir :: Git.Repo -> FilePath
gitAnnexDir r = addTrailingPathSeparator $ Git.localGitDir r </> annexDir

{- The part of the annex directory where file contents are stored. -}
gitAnnexObjectDir :: Git.Repo -> FilePath
gitAnnexObjectDir r = addTrailingPathSeparator $ Git.localGitDir r </> objectDir

{- .git/annex/tmp/ is used for temp files for key's contents -}
gitAnnexTmpObjectDir :: Git.Repo -> FilePath
gitAnnexTmpObjectDir r = addTrailingPathSeparator $ gitAnnexDir r </> "tmp"

{- .git/annex/othertmp/ is used for other temp files -}
gitAnnexTmpOtherDir :: Git.Repo -> FilePath
gitAnnexTmpOtherDir r = addTrailingPathSeparator $ gitAnnexDir r </> "othertmp"

{- Lock file for gitAnnexTmpOtherDir. -}
gitAnnexTmpOtherLock :: Git.Repo -> FilePath
gitAnnexTmpOtherLock r = gitAnnexDir r </> "othertmp.lck"

{- .git/annex/misctmp/ was used by old versions of git-annex and is still
 - used during initialization -}
gitAnnexTmpOtherDirOld :: Git.Repo -> FilePath
gitAnnexTmpOtherDirOld r = addTrailingPathSeparator $ gitAnnexDir r </> "misctmp"

{- .git/annex/watchtmp/ is used by the watcher and assistant -}
gitAnnexTmpWatcherDir :: Git.Repo -> FilePath
gitAnnexTmpWatcherDir r = addTrailingPathSeparator $ gitAnnexDir r </> "watchtmp"

{- The temp file to use for a given key's content. -}
gitAnnexTmpObjectLocation :: Key -> Git.Repo -> FilePath
gitAnnexTmpObjectLocation key r = gitAnnexTmpObjectDir r </> keyFile key

{- Given a temp file such as gitAnnexTmpObjectLocation, makes a name for a
 - subdirectory in the same location, that can be used as a work area
 - when receiving the key's content.
 -
 - There are ordering requirements for creating these directories;
 - use Annex.Content.withTmpWorkDir to set them up.
 -}
gitAnnexTmpWorkDir :: FilePath -> FilePath
gitAnnexTmpWorkDir p =
	let (dir, f) = splitFileName p
	-- Using a prefix avoids name conflict with any other keys.
	in dir </> "work." ++ f

{- .git/annex/bad/ is used for bad files found during fsck -}
gitAnnexBadDir :: Git.Repo -> FilePath
gitAnnexBadDir r = addTrailingPathSeparator $ gitAnnexDir r </> "bad"

{- The bad file to use for a given key. -}
gitAnnexBadLocation :: Key -> Git.Repo -> FilePath
gitAnnexBadLocation key r = gitAnnexBadDir r </> keyFile key

{- .git/annex/foounused is used to number possibly unused keys -}
gitAnnexUnusedLog :: FilePath -> Git.Repo -> FilePath
gitAnnexUnusedLog prefix r = gitAnnexDir r </> (prefix ++ "unused")

{- .git/annex/keys/ contains a database of information about keys. -}
gitAnnexKeysDb :: Git.Repo -> FilePath
gitAnnexKeysDb r = gitAnnexDir r </> "keys"

{- Lock file for the keys database. -}
gitAnnexKeysDbLock :: Git.Repo -> FilePath
gitAnnexKeysDbLock r = gitAnnexKeysDb r ++ ".lck"

{- Contains the stat of the last index file that was
 - reconciled with rhe keys database. -}
gitAnnexKeysDbIndexCache :: Git.Repo -> FilePath
gitAnnexKeysDbIndexCache r = gitAnnexKeysDb r ++ ".cache"

{- .git/annex/fsck/uuid/ is used to store information about incremental
 - fscks. -}
gitAnnexFsckDir :: UUID -> Git.Repo -> FilePath
gitAnnexFsckDir u r = gitAnnexDir r </> "fsck" </> fromUUID u

{- used to store information about incremental fscks. -}
gitAnnexFsckState :: UUID -> Git.Repo -> FilePath
gitAnnexFsckState u r = gitAnnexFsckDir u r </> "state"

{- Directory containing database used to record fsck info. -}
gitAnnexFsckDbDir :: UUID -> Git.Repo -> FilePath
gitAnnexFsckDbDir u r = gitAnnexFsckDir u r </> "db"

{- Lock file for the fsck database. -}
gitAnnexFsckDbLock :: UUID -> Git.Repo -> FilePath
gitAnnexFsckDbLock u r = gitAnnexFsckDir u r </> "fsck.lck"

{- .git/annex/fsckresults/uuid is used to store results of git fscks -}
gitAnnexFsckResultsLog :: UUID -> Git.Repo -> FilePath
gitAnnexFsckResultsLog u r = gitAnnexDir r </> "fsckresults" </> fromUUID u

{- .git/annex/smudge.log is used to log smudges worktree files that need to
 - be updated. -}
gitAnnexSmudgeLog :: Git.Repo -> FilePath
gitAnnexSmudgeLog r = gitAnnexDir r </> "smudge.log"

gitAnnexSmudgeLock :: Git.Repo -> FilePath
gitAnnexSmudgeLock r = gitAnnexDir r </> "smudge.lck"

{- .git/annex/export/uuid/ is used to store information about
 - exports to special remotes. -}
gitAnnexExportDir :: UUID -> Git.Repo -> FilePath
gitAnnexExportDir u r = gitAnnexDir r </> "export" </> fromUUID u

{- Directory containing database used to record export info. -}
gitAnnexExportDbDir :: UUID -> Git.Repo -> FilePath
gitAnnexExportDbDir u r = gitAnnexExportDir u r </> "db"

{- Lock file for export state for a special remote. -}
gitAnnexExportLock :: UUID -> Git.Repo -> FilePath
gitAnnexExportLock u r = gitAnnexExportDbDir u r ++ ".lck"

{- Lock file for updating the export state for a special remote. -}
gitAnnexExportUpdateLock :: UUID -> Git.Repo -> FilePath
gitAnnexExportUpdateLock u r = gitAnnexExportDbDir u r ++ ".upl"

{- Log file used to keep track of files that were in the tree exported to a
 - remote, but were excluded by its preferred content settings. -}
gitAnnexExportExcludeLog :: UUID -> Git.Repo -> FilePath
gitAnnexExportExcludeLog u r = gitAnnexDir r </> "export.ex" </> fromUUID u

{- Directory containing database used to record remote content ids.
 -
 - (This used to be "cid", but a problem with the database caused it to
 - need to be rebuilt with a new name.)
 -}
gitAnnexContentIdentifierDbDir :: Git.Repo -> FilePath
gitAnnexContentIdentifierDbDir r = gitAnnexDir r </> "cids"

{- Lock file for writing to the content id database. -}
gitAnnexContentIdentifierLock :: Git.Repo -> FilePath
gitAnnexContentIdentifierLock r = gitAnnexContentIdentifierDbDir r ++ ".lck"

{- .git/annex/schedulestate is used to store information about when
 - scheduled jobs were last run. -}
gitAnnexScheduleState :: Git.Repo -> FilePath
gitAnnexScheduleState r = gitAnnexDir r </> "schedulestate"

{- .git/annex/creds/ is used to store credentials to access some special
 - remotes. -}
gitAnnexCredsDir :: Git.Repo -> FilePath
gitAnnexCredsDir r = addTrailingPathSeparator $ gitAnnexDir r </> "creds"

{- .git/annex/certificate.pem and .git/annex/key.pem are used by the webapp
 - when HTTPS is enabled -}
gitAnnexWebCertificate :: Git.Repo -> FilePath
gitAnnexWebCertificate r = gitAnnexDir r </> "certificate.pem"
gitAnnexWebPrivKey :: Git.Repo -> FilePath
gitAnnexWebPrivKey r = gitAnnexDir r </> "privkey.pem"

{- .git/annex/feeds/ is used to record per-key (url) state by importfeeds -}
gitAnnexFeedStateDir :: Git.Repo -> FilePath
gitAnnexFeedStateDir r = addTrailingPathSeparator $ gitAnnexDir r </> "feedstate"

gitAnnexFeedState :: Key -> Git.Repo -> FilePath
gitAnnexFeedState k r = gitAnnexFeedStateDir r </> keyFile k

{- .git/annex/merge/ is used as a empty work tree for direct mode merges and
 - merges in adjusted branches. -}
gitAnnexMergeDir :: Git.Repo -> FilePath
gitAnnexMergeDir r = addTrailingPathSeparator $ gitAnnexDir r </> "merge"

{- .git/annex/transfer/ is used to record keys currently
 - being transferred, and other transfer bookkeeping info. -}
gitAnnexTransferDir :: Git.Repo -> FilePath
gitAnnexTransferDir r = addTrailingPathSeparator $ gitAnnexDir r </> "transfer"

{- .git/annex/journal/ is used to journal changes made to the git-annex
 - branch -}
gitAnnexJournalDir :: Git.Repo -> FilePath
gitAnnexJournalDir r = addTrailingPathSeparator $ gitAnnexDir r </> "journal"

{- Lock file for the journal. -}
gitAnnexJournalLock :: Git.Repo -> FilePath
gitAnnexJournalLock r = gitAnnexDir r </> "journal.lck"

{- Lock file for flushing a git queue that writes to the git index or
 - other git state that should only have one writer at a time. -}
gitAnnexGitQueueLock :: Git.Repo -> FilePath
gitAnnexGitQueueLock r = gitAnnexDir r </> "gitqueue.lck"

{- Lock file for the pre-commit hook. -}
gitAnnexPreCommitLock :: Git.Repo -> FilePath
gitAnnexPreCommitLock r = gitAnnexDir r </> "precommit.lck"

{- Lock file for direct mode merge. -}
gitAnnexMergeLock :: Git.Repo -> FilePath
gitAnnexMergeLock r = gitAnnexDir r </> "merge.lck"

{- .git/annex/index is used to stage changes to the git-annex branch -}
gitAnnexIndex :: Git.Repo -> FilePath
gitAnnexIndex r = gitAnnexDir r </> "index"

{- Holds the ref of the git-annex branch that the index was last updated to.
 -
 - The .lck in the name is a historical accident; this is not used as a
 - lock. -}
gitAnnexIndexStatus :: Git.Repo -> FilePath
gitAnnexIndexStatus r = gitAnnexDir r </> "index.lck"

{- The index file used to generate a filtered branch view._-}
gitAnnexViewIndex :: Git.Repo -> FilePath
gitAnnexViewIndex r = gitAnnexDir r </> "viewindex"

{- File containing a log of recently accessed views. -}
gitAnnexViewLog :: Git.Repo -> FilePath
gitAnnexViewLog r = gitAnnexDir r </> "viewlog"

{- List of refs that have already been merged into the git-annex branch. -}
gitAnnexMergedRefs :: Git.Repo -> FilePath
gitAnnexMergedRefs r = gitAnnexDir r </> "mergedrefs"

{- List of refs that should not be merged into the git-annex branch. -}
gitAnnexIgnoredRefs :: Git.Repo -> FilePath
gitAnnexIgnoredRefs r = gitAnnexDir r </> "ignoredrefs"

{- Pid file for daemon mode. -}
gitAnnexPidFile :: Git.Repo -> FilePath
gitAnnexPidFile r = gitAnnexDir r </> "daemon.pid"

{- Pid lock file for pidlock mode -}
gitAnnexPidLockFile :: Git.Repo -> FilePath
gitAnnexPidLockFile r = gitAnnexDir r </> "pidlock"

{- Status file for daemon mode. -}
gitAnnexDaemonStatusFile :: Git.Repo -> FilePath
gitAnnexDaemonStatusFile r = gitAnnexDir r </> "daemon.status"

{- Log file for daemon mode. -}
gitAnnexLogFile :: Git.Repo -> FilePath
gitAnnexLogFile r = gitAnnexDir r </> "daemon.log"

{- Log file for fuzz test. -}
gitAnnexFuzzTestLogFile :: Git.Repo -> FilePath
gitAnnexFuzzTestLogFile r = gitAnnexDir r </> "fuzztest.log"

{- Html shim file used to launch the webapp. -}
gitAnnexHtmlShim :: Git.Repo -> FilePath
gitAnnexHtmlShim r = gitAnnexDir r </> "webapp.html"

{- File containing the url to the webapp. -}
gitAnnexUrlFile :: Git.Repo -> FilePath
gitAnnexUrlFile r = gitAnnexDir r </> "url"

{- Temporary file used to edit configuriation from the git-annex branch. -}
gitAnnexTmpCfgFile :: Git.Repo -> FilePath
gitAnnexTmpCfgFile r = gitAnnexDir r </> "config.tmp"

{- .git/annex/ssh/ is used for ssh connection caching -}
gitAnnexSshDir :: Git.Repo -> FilePath
gitAnnexSshDir r = addTrailingPathSeparator $ gitAnnexDir r </> "ssh"

{- .git/annex/remotes/ is used for remote-specific state. -}
gitAnnexRemotesDir :: Git.Repo -> FilePath
gitAnnexRemotesDir r = addTrailingPathSeparator $ gitAnnexDir r </> "remotes"

{- This is the base directory name used by the assistant when making
 - repositories, by default. -}
gitAnnexAssistantDefaultDir :: FilePath
gitAnnexAssistantDefaultDir = "annex"

{- Sanitizes a String that will be used as part of a Key's keyName,
 - dealing with characters that cause problems.
 -
 - This is used when a new Key is initially being generated, eg by getKey.
 - Unlike keyFile and fileKey, it does not need to be a reversable
 - escaping. Also, it's ok to change this to add more problematic
 - characters later. Unlike changing keyFile, which could result in the
 - filenames used for existing keys changing and contents getting lost.
 -
 - It is, however, important that the input and output of this function
 - have a 1:1 mapping, to avoid two different inputs from mapping to the
 - same key.
 -}
preSanitizeKeyName :: String -> String
preSanitizeKeyName = preSanitizeKeyName' False

preSanitizeKeyName' :: Bool -> String -> String
preSanitizeKeyName' resanitize = concatMap escape
  where
	escape c
		| isAsciiUpper c || isAsciiLower c || isDigit c = [c]
		| c `elem` ['.', '-', '_'] = [c] -- common, assumed safe
		| c `elem` ['/', '%', ':'] = [c] -- handled by keyFile
		-- , is safe and uncommon, so will be used to escape
		-- other characters. By itself, it is escaped to 
		-- doubled form.
		| c == ',' = if not resanitize
			then ",,"
			else ","
		| otherwise = ',' : show (ord c)

{- Converts a keyName that has been santizied with an old version of
 - preSanitizeKeyName to be sanitized with the new version. -}
reSanitizeKeyName :: String -> String
reSanitizeKeyName = preSanitizeKeyName' True

{- Converts a key into a filename fragment without any directory.
 -
 - Escape "/" in the key name, to keep a flat tree of files and avoid
 - issues with keys containing "/../" or ending with "/" etc. 
 -
 - "/" is escaped to "%" because it's short and rarely used, and resembles
 -     a slash
 - "%" is escaped to "&s", and "&" to "&a"; this ensures that the mapping
 -     is one to one.
 - ":" is escaped to "&c", because it seemed like a good idea at the time.
 -
 - Changing what this function escapes and how is not a good idea, as it
 - can cause existing objects to get lost.
 -}
keyFile :: Key -> FilePath
keyFile = fromRawFilePath . keyFile'

keyFile' :: Key -> RawFilePath
keyFile' k = 
	let b = serializeKey' k
	in if S8.any (`elem` ['&', '%', ':', '/']) b
		then S8.concatMap esc b
		else b
  where
	esc '&' = "&a"
	esc '%' = "&s"
	esc ':' = "&c"
	esc '/' = "%"
	esc c = S8.singleton c


{- Reverses keyFile, converting a filename fragment (ie, the basename of
 - the symlink target) into a key. -}
fileKey :: FilePath -> Maybe Key
fileKey = fileKey' . toRawFilePath

fileKey' :: RawFilePath -> Maybe Key
fileKey' = deserializeKey' . S8.intercalate "/" . map go . S8.split '%'
  where
	go = S8.concat . unescafterfirst . S8.split '&'
	unescafterfirst [] = []
	unescafterfirst (b:bs) = b : map (unesc . S8.uncons) bs
	unesc :: Maybe (Char, S8.ByteString) -> S8.ByteString
	unesc Nothing = mempty
	unesc (Just ('c', b)) = S8.cons ':' b
	unesc (Just ('s', b)) = S8.cons '%' b
	unesc (Just ('a', b)) = S8.cons '&' b
	unesc (Just (c, b)) = S8.cons c b

{- A location to store a key on a special remote that uses a filesystem.
 - A directory hash is used, to protect against filesystems that dislike
 - having many items in a single directory.
 -
 - The file is put in a directory with the same name, this allows
 - write-protecting the directory to avoid accidental deletion of the file.
 -}
keyPath :: Key -> Hasher -> FilePath
keyPath key hasher = hasher key </> f </> f
  where
	f = keyFile key

{- All possibile locations to store a key in a special remote
 - using different directory hashes.
 -
 - This is compatible with the annexLocations, for interoperability between
 - special remotes and git-annex repos.
 -}
keyPaths :: Key -> [FilePath]
keyPaths key = map (\h -> keyPath key (h def)) dirHashes