{- Sqlite database of information about Keys
 -
 - Copyright 2015-2021 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE OverloadedStrings #-}

module Database.Keys (
	DbHandle,
	closeDb,
	addAssociatedFile,
	getAssociatedFiles,
	getAssociatedKey,
	removeAssociatedFile,
	storeInodeCaches,
	storeInodeCaches',
	addInodeCaches,
	getInodeCaches,
	removeInodeCaches,
	removeInodeCache,
	isInodeKnown,
	runWriter,
) where

import qualified Database.Keys.SQL as SQL
import Database.Types
import Database.Keys.Handle
import qualified Database.Queue as H
import Database.Init
import Annex.Locations
import Annex.Common hiding (delete)
import qualified Annex
import Annex.LockFile
import Annex.CatFile
import Annex.Content.PointerFile
import Annex.Link
import Utility.InodeCache
import Annex.InodeSentinal
import Git
import Git.FilePath
import Git.Command
import Git.Types
import Git.Index
import Git.Sha
import Git.Branch (writeTreeQuiet, update')
import qualified Git.Ref
import Config.Smudge
import qualified Utility.RawFilePath as R

import qualified Data.ByteString as S
import qualified Data.ByteString.Char8 as S8
import qualified System.FilePath.ByteString as P

{- Runs an action that reads from the database.
 -
 - If the database doesn't already exist, it's not created; mempty is
 - returned instead. This way, when the keys database is not in use,
 - there's minimal overhead in checking it.
 -
 - If the database is already open, any writes are flushed to it, to ensure
 - consistency.
 -
 - Any queued writes will be flushed before the read.
 -}
runReader :: Monoid v => (SQL.ReadHandle -> Annex v) -> Annex v
runReader a = do
	h <- Annex.getRead Annex.keysdbhandle
	withDbState h go
  where
	go DbUnavailable = return (mempty, DbUnavailable)
	go st@(DbOpen qh) = do
		liftIO $ H.flushDbQueue qh
		v <- a (SQL.ReadHandle qh)
		return (v, st)
	go DbClosed = do
		st' <- openDb False DbClosed
		v <- case st' of
			(DbOpen qh) -> a (SQL.ReadHandle qh)
			_ -> return mempty
		return (v, st')

runReaderIO :: Monoid v => (SQL.ReadHandle -> IO v) -> Annex v
runReaderIO a = runReader (liftIO . a)

{- Runs an action that writes to the database. Typically this is used to
 - queue changes, which will be flushed at a later point.
 -
 - The database is created if it doesn't exist yet. -}
runWriter :: (SQL.WriteHandle -> Annex ()) -> Annex ()
runWriter a = do
	h <- Annex.getRead Annex.keysdbhandle
	withDbState h go
  where
	go st@(DbOpen qh) = do
		v <- a (SQL.WriteHandle qh)
		return (v, st)
	go st = do
		st' <- openDb True st
		v <- case st' of
			DbOpen qh -> a (SQL.WriteHandle qh)
			_ -> error "internal"
		return (v, st')

runWriterIO :: (SQL.WriteHandle -> IO ()) -> Annex ()
runWriterIO a = runWriter (liftIO . a)

{- Opens the database, perhaps creating it if it doesn't exist yet.
 -
 - Multiple readers and writers can have the database open at the same
 - time. Database.Handle deals with the concurrency issues.
 - The lock is held while opening the database, so that when
 - the database doesn't exist yet, one caller wins the lock and
 - can create it undisturbed.
 -}
openDb :: Bool -> DbState -> Annex DbState
openDb _ st@(DbOpen _) = return st
openDb False DbUnavailable = return DbUnavailable
openDb createdb _ = catchPermissionDenied permerr $ withExclusiveLock gitAnnexKeysDbLock $ do
	dbdir <- fromRepo gitAnnexKeysDb
	let db = dbdir P.</> "db"
	dbexists <- liftIO $ R.doesPathExist db
	case (dbexists, createdb) of
		(True, _) -> open db
		(False, True) -> do
			initDb db SQL.createTables
			open db
		(False, False) -> return DbUnavailable
  where
	-- If permissions don't allow opening the database, treat it as if
	-- it does not exist.
	permerr e = case createdb of
		False -> return DbUnavailable
		True -> throwM e
	
	open db = do
		qh <- liftIO $ H.openDbQueue H.MultiWriter db SQL.containedTable
		reconcileStaged qh
		return $ DbOpen qh

{- Closes the database if it was open. Any writes will be flushed to it.
 -
 - This does not normally need to be called; the database will auto-close
 - when the handle is garbage collected. However, this can be used to
 - force a re-read of the database, in case another process has written
 - data to it.
 -}
closeDb :: Annex ()
closeDb = liftIO . closeDbHandle =<< Annex.getRead Annex.keysdbhandle

addAssociatedFile :: Key -> TopFilePath -> Annex ()
addAssociatedFile k f = runWriterIO $ SQL.addAssociatedFile k f

{- Note that the files returned were once associated with the key, but
 - some of them may not be any longer. -}
getAssociatedFiles :: Key -> Annex [TopFilePath]
getAssociatedFiles = runReaderIO . SQL.getAssociatedFiles

{- Gets any keys that are on record as having a particular associated file.
 - (Should be one or none but the database doesn't enforce that.) -}
getAssociatedKey :: TopFilePath -> Annex [Key]
getAssociatedKey = runReaderIO . SQL.getAssociatedKey

removeAssociatedFile :: Key -> TopFilePath -> Annex ()
removeAssociatedFile k = runWriterIO . SQL.removeAssociatedFile k

{- Stats the files, and stores their InodeCaches. -}
storeInodeCaches :: Key -> [RawFilePath] -> Annex ()
storeInodeCaches k fs = storeInodeCaches' k fs []

storeInodeCaches' :: Key -> [RawFilePath] -> [InodeCache] -> Annex ()
storeInodeCaches' k fs ics = withTSDelta $ \d ->
	addInodeCaches k . (++ ics) . catMaybes
		=<< liftIO (mapM (\f -> genInodeCache f d) fs)

addInodeCaches :: Key -> [InodeCache] -> Annex ()
addInodeCaches k is = runWriterIO $ SQL.addInodeCaches k is

{- A key may have multiple InodeCaches; one for the annex object, and one
 - for each pointer file that is a copy of it. -}
getInodeCaches :: Key -> Annex [InodeCache]
getInodeCaches = runReaderIO . SQL.getInodeCaches

{- Remove all inodes cached for a key. -}
removeInodeCaches :: Key -> Annex ()
removeInodeCaches = runWriterIO . SQL.removeInodeCaches

{- Remove cached inodes, for any key. -}
removeInodeCache :: InodeCache -> Annex ()
removeInodeCache = runWriterIO . SQL.removeInodeCache

isInodeKnown :: InodeCache -> SentinalStatus -> Annex Bool
isInodeKnown i s = or <$> runReaderIO ((:[]) <$$> SQL.isInodeKnown i s)

{- Looks at staged changes to annexed files, and updates the keys database,
 - so that its information is consistent with the state of the repository.
 -
 - This is run with a lock held, so only one process can be running this at
 - a time.
 -
 - To avoid unncessary work, the index file is statted, and if it's not
 - changed since last time this was run, nothing is done.
 -
 - A tree is generated from the index, and the diff between that tree
 - and the last processed tree is examined for changes.
 -
 - This also cleans up after a race between eg a git mv and git-annex
 - get/drop/similar. If git moves the file between this being run and the
 - get/drop, the moved file won't be updated for the get/drop. 
 - The next time this runs, it will see the staged change. It then checks
 - if the worktree file's content availability does not match the git-annex
 - content availablity, and makes changes as necessary to reconcile them.
 -
 - Note that if a commit happens before this runs again, it won't see
 - the staged change. Instead, during the commit, git will run the clean
 - filter. If a drop missed the file then the file is added back into the
 - annex. If a get missed the file then the clean filter populates the
 - file.
 -
 - There is a situation where, after this has run, the database can still
 - contain associated files that have been deleted from the index.
 - That happens when addAssociatedFile is used to record a newly
 - added file, but that file then gets removed from the index before
 - this is run. Eg, "git-annex add foo; git rm foo"
 - So when using getAssociatedFiles, have to make sure the file still
 - is an associated file.
 -}
reconcileStaged :: H.DbQueue -> Annex ()
reconcileStaged qh = do
	gitindex <- inRepo currentIndexFile
	indexcache <- fromRawFilePath <$> fromRepo gitAnnexKeysDbIndexCache
	withTSDelta (liftIO . genInodeCache gitindex) >>= \case
		Just cur -> readindexcache indexcache >>= \case
			Nothing -> go cur indexcache =<< getindextree
			Just prev -> ifM (compareInodeCaches prev cur)
				( noop
				, go cur indexcache =<< getindextree
				)
		Nothing -> noop
  where
	lastindexref = Ref "refs/annex/last-index"

	getindextree = inRepo writeTreeQuiet

	readindexcache indexcache = liftIO $ maybe Nothing readInodeCache
		<$> catchMaybeIO (readFile indexcache)

	getoldtree = fromMaybe emptyTree <$> inRepo (Git.Ref.sha lastindexref)

	go cur indexcache (Just newtree) = do
		oldtree <- getoldtree
		when (oldtree /= newtree) $ do
			updatetodiff (fromRef oldtree) (fromRef newtree)
			liftIO $ writeFile indexcache $ showInodeCache cur
			-- Storing the tree in a ref makes sure it does not
			-- get garbage collected, and is available to diff
			-- against next time.
			inRepo $ update' lastindexref newtree
	-- git write-tree will fail if the index is locked or when there is
	-- a merge conflict. To get up-to-date with the current index, 
	-- diff --cached with the old index tree. The current index tree
	-- is not known, so not recorded, and the inode cache is not updated,
	-- so the next time git-annex runs, it will diff again, even
	-- if the index is unchanged.
	go _ _ Nothing = do
		oldtree <- getoldtree
		updatetodiff (fromRef oldtree) "--cached"
		
	updatetodiff old new = do
		(l, cleanup) <- inRepo $ pipeNullSplit' $ diff old new
		changed <- procdiff l False
		void $ liftIO cleanup
		-- Flush database changes immediately
		-- so other processes can see them.
		when changed $
			liftIO $ H.flushDbQueue qh
	
	diff old new =
		-- Avoid running smudge or clean filters, since we want the
		-- raw output, and they would block trying to access the
		-- locked database. The --raw normally avoids git diff
		-- running them, but older versions of git need this.
		bypassSmudgeConfig ++
		-- Avoid using external diff command, which would be slow.
		-- (The -G option may make it be used otherwise.)
		[ Param "-c", Param "diff.external="
		, Param "diff"
		, Param old
		, Param new
		, Param "--raw"
		, Param "-z"
		, Param "--no-abbrev"
		-- Optimization: Limit to pointer files and annex symlinks.
		-- This is not perfect. A file could contain with this and not
		-- be a pointer file. And a pointer file that is replaced with
		-- a non-pointer file will match this. This is only a
		-- prefilter so that's ok.
		, Param $ "-G" ++ fromRawFilePath (toInternalGitPath $
			P.pathSeparator `S.cons` objectDir')
		-- Disable rename detection.
		, Param "--no-renames"
		-- Avoid other complications.
		, Param "--ignore-submodules=all"
		, Param "--no-ext-diff"
		]
	
	procdiff (info:file:rest) changed
		| ":" `S.isPrefixOf` info = case S8.words info of
			(_colonsrcmode:dstmode:srcsha:dstsha:_change:[]) -> do
				removed <- catKey (Ref srcsha) >>= \case
					Just oldkey -> do
						liftIO $ SQL.removeAssociatedFile oldkey
							(asTopFilePath file)
							(SQL.WriteHandle qh)
						return True
					Nothing -> return False
				added <- catKey (Ref dstsha) >>= \case
					Just key -> do
						liftIO $ SQL.addAssociatedFile key
							(asTopFilePath file)
							(SQL.WriteHandle qh)
						when (dstmode /= fmtTreeItemType TreeSymlink) $
							reconcilerace (asTopFilePath file) key
						return True
					Nothing -> return False
				procdiff rest (changed || removed || added)
			_ -> return changed -- parse failed
	procdiff _ changed = return changed

	reconcilerace file key = do
		caches <- liftIO $ SQL.getInodeCaches key (SQL.ReadHandle qh)
		keyloc <- calcRepo (gitAnnexLocation key)
		keypopulated <- sameInodeCache keyloc caches
		p <- fromRepo $ fromTopFilePath file
		filepopulated <- sameInodeCache p caches
		case (keypopulated, filepopulated) of
			(True, False) ->
				populatePointerFile (Restage True) key keyloc p >>= \case
					Nothing -> return ()
					Just ic -> liftIO $
						SQL.addInodeCaches key [ic] (SQL.WriteHandle qh)
			(False, True) -> depopulatePointerFile key p
			_ -> return ()