{- Sqlite database of information about Keys
 -
 - Copyright 2015-2016 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

{-# LANGUAGE ScopedTypeVariables #-}

module Database.Keys (
	DbHandle,
	closeDb,
	addAssociatedFile,
	getAssociatedFiles,
	getAssociatedKey,
	removeAssociatedFile,
	scanAssociatedFiles,
	storeInodeCaches,
	addInodeCaches,
	getInodeCaches,
	removeInodeCaches,
) where

import qualified Database.Keys.SQL as SQL
import Database.Types
import Database.Keys.Handle
import qualified Database.Queue as H
import Annex.Locations
import Annex.Common hiding (delete)
import Annex.Version (versionUsesKeysDatabase)
import qualified Annex
import Annex.Perms
import Annex.LockFile
import Utility.InodeCache
import Annex.InodeSentinal
import qualified Git.Types
import qualified Git.LsTree
import qualified Git.Branch
import Git.Ref
import Git.FilePath
import Annex.CatFile

import Database.Esqueleto hiding (Key)

{- 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 <- getDbHandle
	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 <- getDbHandle
	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)

{- Gets the handle cached in Annex state; creates a new one if it's not yet
 - available, but doesn't open the database. -}
getDbHandle :: Annex DbHandle
getDbHandle = go =<< Annex.getState Annex.keysdbhandle
  where
	go (Just h) = pure h
	go Nothing = do
		h <- ifM versionUsesKeysDatabase
			( liftIO newDbHandle
			, liftIO unavailableDbHandle
			)
		Annex.changeState $ \s -> s { Annex.keysdbhandle = Just h }
		return h

{- 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 </> "db"
	dbexists <- liftIO $ doesFileExist db
	case (dbexists, createdb) of
		(True, _) -> open db
		(False, True) -> do
			liftIO $ do
				createDirectoryIfMissing True dbdir
				H.initDb db SQL.createTables
			setAnnexDirPerm dbdir
			setAnnexFilePerm db
			open db
		(False, False) -> return DbUnavailable
  where
	open db = liftIO $ DbOpen <$> H.openDbQueue db SQL.containedTable
	-- 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

{- 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 =<< getDbHandle

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

{- 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 = map fromIKey <$$> runReaderIO . SQL.getAssociatedKey

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

{- Find all unlocked associated files. This is expensive, and so normally
 - the associated files are updated incrementally when changes are noticed. -}
scanAssociatedFiles :: Annex ()
scanAssociatedFiles = whenM (isJust <$> inRepo Git.Branch.current) $ 
	runWriter $ \h -> do
		showSideAction "scanning for unlocked files"
		dropallassociated h
		(l, cleanup) <- inRepo $ Git.LsTree.lsTree headRef
		forM_ l $ \i -> 
			when (isregfile i) $
				maybe noop (add h i)
					=<< catKey (Git.LsTree.sha i)
		liftIO $ void cleanup
  where
	dropallassociated h = liftIO $ flip SQL.queueDb h $
		delete $ from $ \(_r :: SqlExpr (Entity SQL.Associated)) ->
			return ()
	isregfile i = case Git.Types.toBlobType (Git.LsTree.mode i) of
		Just Git.Types.FileBlob -> True
		Just Git.Types.ExecutableBlob -> True
		_ -> False
	add h i k = liftIO $ flip SQL.queueDb h $ 
		void $ insertUnique $ SQL.Associated
			(toIKey k)
			(toSFilePath $ getTopFilePath $ Git.LsTree.file i)

{- Stats the files, and stores their InodeCaches. -}
storeInodeCaches :: Key -> [FilePath] -> Annex ()
storeInodeCaches k fs = withTSDelta $ \d ->
	addInodeCaches k . catMaybes =<< liftIO (mapM (`genInodeCache` d) fs)

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

removeInodeCaches :: Key -> Annex ()
removeInodeCaches = runWriterIO . SQL.removeInodeCaches . toIKey