{- git-annex file content managing
 -
 - Copyright 2010,2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Annex.Content (
	inAnnex,
	inAnnexSafe,
	lockContent,
	calcGitLink,
	getViaTmp,
	getViaTmpUnchecked,
	withTmp,
	checkDiskSpace,
	moveAnnex,
	sendAnnex,
	removeAnnex,
	fromAnnex,
	moveBad,
	getKeysPresent,
	saveState,
	downloadUrl,
	preseedTmp,
	freezeContent,
	thawContent,
	freezeContentDir,
	createContentDir,
	replaceFile,
) where

import System.IO.Unsafe (unsafeInterleaveIO)

import Common.Annex
import Logs.Location
import qualified Git
import qualified Annex
import qualified Annex.Queue
import qualified Annex.Branch
import Utility.DiskFree
import Utility.FileMode
import qualified Utility.Url as Url
import Types.Key
import Utility.DataUnits
import Utility.CopyFile
import Config
import Annex.Exception
import Git.SharedRepository
import Annex.Perms
import Annex.Content.Direct

{- Checks if a given key's content is currently present. -}
inAnnex :: Key -> Annex Bool
inAnnex = inAnnex' id False $ liftIO . doesFileExist

{- Generic inAnnex, handling both indirect and direct mode.
 -
 - In direct mode, at least one of the associated files must pass the
 - check. Additionally, the file must be unmodified.
 -}
inAnnex' :: (a -> Bool) -> a -> (FilePath -> Annex a) -> Key -> Annex a
inAnnex' isgood bad check key = withObjectLoc key checkindirect checkdirect
  where
	checkindirect loc = do
		whenM (fromRepo Git.repoIsUrl) $
			error "inAnnex cannot check remote repo"
		check loc
	checkdirect [] = return bad
	checkdirect (loc:locs) = do
		r <- check loc
		if isgood r
			then ifM (goodContent key loc)
				( return r
				, checkdirect locs
				)
			else checkdirect locs

{- A safer check; the key's content must not only be present, but
 - is not in the process of being removed. -}
inAnnexSafe :: Key -> Annex (Maybe Bool)
inAnnexSafe = inAnnex' (maybe False id) (Just False) go
  where
	go f = liftIO $ openforlock f >>= check
	openforlock f = catchMaybeIO $
		openFd f ReadOnly Nothing defaultFileFlags
	check Nothing = return is_missing
	check (Just h) = do
		v <- getLock h (ReadLock, AbsoluteSeek, 0, 0)
		closeFd h
		return $ case v of
			Just _ -> is_locked
			Nothing -> is_unlocked
	is_locked = Nothing
	is_unlocked = Just True
	is_missing = Just False

{- Content is exclusively locked while running an action that might remove
 - it. (If the content is not present, no locking is done.) -}
lockContent :: Key -> Annex a -> Annex a
lockContent key a = do
	file <- inRepo $ gitAnnexLocation key
	bracketIO (openforlock file >>= lock) unlock a
  where
	{- Since files are stored with the write bit disabled, have
	 - to fiddle with permissions to open for an exclusive lock. -}
	openforlock f = catchMaybeIO $ ifM (doesFileExist f)
		( withModifiedFileMode f
			(`unionFileModes` ownerWriteMode)
			open
		, open
		)
	  where
		open = openFd f ReadWrite Nothing defaultFileFlags
	lock Nothing = return Nothing
	lock (Just fd) = do
		v <- tryIO $ setLock fd (WriteLock, AbsoluteSeek, 0, 0)
		case v of
			Left _ -> error "content is locked"
			Right _ -> return $ Just fd
	unlock Nothing = noop
	unlock (Just l) = closeFd l

{- Calculates the relative path to use to link a file to a key. -}
calcGitLink :: FilePath -> Key -> Annex FilePath
calcGitLink file key = do
	cwd <- liftIO getCurrentDirectory
	let absfile = fromMaybe whoops $ absNormPath cwd file
	loc <- inRepo $ gitAnnexLocation key
	return $ relPathDirToFile (parentDir absfile) loc
  where
	whoops = error $ "unable to normalize " ++ file

{- Runs an action, passing it a temporary filename to get,
 - and if the action succeeds, moves the temp file into 
 - the annex as a key's content. -}
getViaTmp :: Key -> (FilePath -> Annex Bool) -> Annex Bool
getViaTmp key action = do
	tmp <- fromRepo $ gitAnnexTmpLocation key

	-- Check that there is enough free disk space.
	-- When the temp file already exists, count the space
	-- it is using as free.
	e <- liftIO $ doesFileExist tmp
	alreadythere <- if e
		then fromIntegral . fileSize <$> liftIO (getFileStatus tmp)
		else return 0
	ifM (checkDiskSpace Nothing key alreadythere)
		( do
			when e $ thawContent tmp
			getViaTmpUnchecked key action
		, return False
		)

prepTmp :: Key -> Annex FilePath
prepTmp key = do
	tmp <- fromRepo $ gitAnnexTmpLocation key
	createAnnexDirectory (parentDir tmp)
	return tmp

{- Like getViaTmp, but does not check that there is enough disk space
 - for the incoming key. For use when the key content is already on disk
 - and not being copied into place. -}
getViaTmpUnchecked :: Key -> (FilePath -> Annex Bool) -> Annex Bool
getViaTmpUnchecked key action = do
	tmpfile <- prepTmp key
	ifM (action tmpfile)
		( do
			moveAnnex key tmpfile
			logStatus key InfoPresent
			return True
		, do
			-- the tmp file is left behind, in case caller wants
			-- to resume its transfer
			return False
		)

{- Creates a temp file, runs an action on it, and cleans up the temp file. -}
withTmp :: Key -> (FilePath -> Annex a) -> Annex a
withTmp key action = do
	tmp <- prepTmp key
	res <- action tmp
	liftIO $ nukeFile tmp
	return res

{- Checks that there is disk space available to store a given key,
 - in a destination (or the annex) printing a warning if not. -}
checkDiskSpace :: Maybe FilePath -> Key -> Integer -> Annex Bool
checkDiskSpace destination key alreadythere = do
	reserve <- annexDiskReserve <$> Annex.getGitConfig
	free <- liftIO . getDiskFree =<< dir
	force <- Annex.getState Annex.force
	case (free, keySize key) of
		(Just have, Just need) -> do
			let ok = (need + reserve <= have + alreadythere) || force
			unless ok $ do
				liftIO $ print (need, reserve, have, alreadythere)
				needmorespace (need + reserve - have - alreadythere)
			return ok
		_ -> return True
  where
	dir = maybe (fromRepo gitAnnexDir) return destination
	needmorespace n =
		warning $ "not enough free space, need " ++ 
			roughSize storageUnits True n ++
			" more" ++ forcemsg
	forcemsg = " (use --force to override this check or adjust annex.diskreserve)"

{- Moves a key's content into .git/annex/objects/
 -
 - In direct mode, moves it to the associated file, or files.
 -
 - What if the key there already has content? This could happen for
 - various reasons; perhaps the same content is being annexed again.
 - Perhaps there has been a hash collision generating the keys.
 -
 - The current strategy is to assume that in this case it's safe to delete
 - one of the two copies of the content; and the one already in the annex
 - is left there, assuming it's the original, canonical copy.
 -
 - I considered being more paranoid, and checking that both files had
 - the same content. Decided against it because A) users explicitly choose
 - a backend based on its hashing properties and so if they're dealing
 - with colliding files it's their own fault and B) adding such a check
 - would not catch all cases of colliding keys. For example, perhaps 
 - a remote has a key; if it's then added again with different content then
 - the overall system now has two different peices of content for that
 - key, and one of them will probably get deleted later. So, adding the
 - check here would only raise expectations that git-annex cannot truely
 - meet.
 -}
moveAnnex :: Key -> FilePath -> Annex ()
moveAnnex key src = withObjectLoc key storeobject storedirect
  where
	storeobject dest = do
		ifM (liftIO $ doesFileExist dest)
			( liftIO $ removeFile src
			, do
				createContentDir dest
				liftIO $ moveFile src dest
				freezeContent dest
				freezeContentDir dest
			)
	storedirect [] = storeobject =<< inRepo (gitAnnexLocation key)
	storedirect (dest:fs) = do
		updateCache key src
		thawContent src
		liftIO $ replaceFile dest $ moveFile src
		liftIO $ forM_ fs $ \f -> replaceFile f $ createLink dest

{- Replaces any existing file with a new version, by running an action.
 - First, makes sure the file is deleted. Or, if it didn't already exist,
 - makes sure the parent directory exists. -}
replaceFile :: FilePath -> (FilePath -> IO ()) -> IO ()
replaceFile file a = do
	r <- tryIO $ removeFile file
	case r of
		Left _ -> createDirectoryIfMissing True (parentDir file)
		_ -> noop
	a file

{- Runs an action to transfer an object's content.
 -
 - In direct mode, it's possible for the file to change as it's being sent.
 - If this happens, returns False. Currently, an arbitrary amount of bad
 - data may be sent when this occurs. The send is not retried even if
 - another file is known to have the same content; the action may not be
 - idempotent.
 -
 - Since objects changing as they're transferred is a somewhat unusual
 - situation, and since preventing writes to the file would be expensive,
 - annoying or both, we instead detect the situation after the affect,
 - and fail. Thus, it's up to the caller to detect a failure and take
 - appropriate action. Such as, for example, ensuring that the bad
 - data that was sent does not get installed into the annex it's being
 - sent to.
 -}
sendAnnex :: Key -> (FilePath -> Annex Bool) -> Annex Bool
sendAnnex key a = withObjectLoc key sendobject senddirect
  where
	sendobject = a
	senddirect [] = return False
	senddirect (f:fs) = do
		cache <- recordedCache key
		-- check that we have a good file
		ifM (compareCache f cache)
			( do
				r <- sendobject f
				-- see if file changed while it was being sent
				ok <- compareCache f cache
				return (r && ok)
			, senddirect fs
			)

{- Performs an action, passing it the location to use for a key's content.
 -
 - In direct mode, the associated files will be passed. But, if there are
 - no associated files for a key, the indirect mode action will be
 - performed instead. -}
withObjectLoc :: Key -> (FilePath -> Annex a) -> ([FilePath] -> Annex a) -> Annex a
withObjectLoc key indirect direct = ifM isDirect
	( do
		fs <- associatedFiles key
		if null fs
			then goindirect
			else direct fs
	, goindirect
	)
  where
	goindirect = indirect =<< inRepo (gitAnnexLocation key)


cleanObjectLoc :: Key -> Annex ()
cleanObjectLoc key = do
	file <- inRepo $ gitAnnexLocation key
	liftIO $ removeparents file (3 :: Int)
  where
	removeparents _ 0 = noop
	removeparents file n = do
		let dir = parentDir file
		maybe noop (const $ removeparents dir (n-1))
			<=< catchMaybeIO $ removeDirectory dir

{- Removes a key's file from .git/annex/objects/
 -
 - In direct mode, deletes the associated files or files, and replaces
 - them with symlinks. -}
removeAnnex :: Key -> Annex ()
removeAnnex key = withObjectLoc key remove removedirect
  where
	remove file = do
		liftIO $ do
			allowWrite $ parentDir file
			removeFile file
		cleanObjectLoc key
	removedirect fs = do
		removeCache key
		mapM_ resetfile fs
	resetfile f = do
		l <- calcGitLink f key
		top <- fromRepo Git.repoPath
		cwd <- liftIO getCurrentDirectory
		let top' = fromMaybe top $ absNormPath cwd top
		let l' = relPathDirToFile top' (fromMaybe l $ absNormPath top' l)
		liftIO $ replaceFile f $ const $
			createSymbolicLink l' f

{- Moves a key's file out of .git/annex/objects/ -}
fromAnnex :: Key -> FilePath -> Annex ()
fromAnnex key dest = do
	file <- inRepo $ gitAnnexLocation key
	liftIO $ allowWrite $ parentDir file
	thawContent file
	liftIO $ moveFile file dest
	cleanObjectLoc key

{- Moves a key out of .git/annex/objects/ into .git/annex/bad, and
 - returns the file it was moved to. -}
moveBad :: Key -> Annex FilePath
moveBad key = do
	src <- inRepo $ gitAnnexLocation key
	bad <- fromRepo gitAnnexBadDir
	let dest = bad </> takeFileName src
	createAnnexDirectory (parentDir dest)
	liftIO $ do
		allowWrite (parentDir src)
		moveFile src dest
	cleanObjectLoc key
	logStatus key InfoMissing
	return dest

{- List of keys whose content exists in .git/annex/objects/ -}
getKeysPresent :: Annex [Key]
getKeysPresent = liftIO . traverse (2 :: Int) =<< fromRepo gitAnnexObjectDir
  where
	traverse depth dir = do
		contents <- catchDefaultIO [] (dirContents dir)
		if depth == 0
			then continue (mapMaybe (fileKey . takeFileName) contents) []
			else do
				let deeper = traverse (depth - 1)
				continue [] (map deeper contents)
	continue keys [] = return keys
	continue keys (a:as) = do
		{- Force lazy traversal with unsafeInterleaveIO. -}
		morekeys <- unsafeInterleaveIO a
		continue (morekeys++keys) as

{- Things to do to record changes to content when shutting down.
 -
 - It's acceptable to avoid committing changes to the branch,
 - especially if performing a short-lived action.
 -}
saveState :: Bool -> Annex ()
saveState nocommit = doSideAction $ do
	Annex.Queue.flush
	unless nocommit $
		whenM (annexAlwaysCommit <$> Annex.getGitConfig) $
			Annex.Branch.commit "update"

{- Downloads content from any of a list of urls. -}
downloadUrl :: [Url.URLString] -> FilePath -> Annex Bool
downloadUrl urls file = do
	o <- map Param . words <$> getConfig (annexConfig "web-options") ""
	headers <- getHttpHeaders
	liftIO $ anyM (\u -> Url.download u headers o file) urls

{- Copies a key's content, when present, to a temp file.
 - This is used to speed up some rsyncs. -}
preseedTmp :: Key -> FilePath -> Annex Bool
preseedTmp key file = go =<< inAnnex key
  where
	go False = return False
	go True = do
		ok <- copy
		when ok $ thawContent file
		return ok
	copy = ifM (liftIO $ doesFileExist file)
			( return True
			, do
				s <- inRepo $ gitAnnexLocation key
				liftIO $ copyFileExternal s file
			)

{- Blocks writing to an annexed file. The file is made unwritable
 - to avoid accidental edits. core.sharedRepository may change
 - who can read it. -}
freezeContent :: FilePath -> Annex ()
freezeContent file = liftIO . go =<< fromRepo getSharedRepository
  where
	go GroupShared = modifyFileMode file $
		removeModes writeModes .
		addModes [ownerReadMode, groupReadMode]
	go AllShared = modifyFileMode file $
		removeModes writeModes .
		addModes readModes
	go _ = preventWrite file

{- Allows writing to an annexed file that freezeContent was called on
 - before. -}
thawContent :: FilePath -> Annex ()
thawContent file = liftIO . go =<< fromRepo getSharedRepository
  where
	go GroupShared = groupWriteRead file
	go AllShared = groupWriteRead file
	go _ = allowWrite file

{- Blocks writing to the directory an annexed file is in, to prevent the
 - file accidentially being deleted. However, if core.sharedRepository
 - is set, this is not done, since the group must be allowed to delete the
 - file.
 -}
freezeContentDir :: FilePath -> Annex ()
freezeContentDir file = liftIO . go =<< fromRepo getSharedRepository
  where
	dir = parentDir file
	go GroupShared = groupWriteRead dir
	go AllShared = groupWriteRead dir
	go _ = preventWrite dir

{- Makes the directory tree to store an annexed file's content,
 - with appropriate permissions on each level. -}
createContentDir :: FilePath -> Annex ()
createContentDir dest = do
	unlessM (liftIO $ doesDirectoryExist dir) $
		createAnnexDirectory dir 
	-- might have already existed with restricted perms
	liftIO $ allowWrite dir
  where
	dir = parentDir dest