{- git-annex assistant daemon status
 -
 - Copyright 2012 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Assistant.DaemonStatus where

import Common.Annex
import Assistant.ThreadedMonad
import Utility.ThreadScheduler
import Utility.TempFile
import Utility.NotificationBroadcaster
import Logs.Transfer
import qualified Command.Sync

import Control.Concurrent.STM
import System.Posix.Types
import Data.Time.Clock.POSIX
import Data.Time
import System.Locale
import qualified Data.Map as M

data DaemonStatus = DaemonStatus
	-- False when the daemon is performing its startup scan
	{ scanComplete :: Bool
	-- Time when a previous process of the daemon was running ok
	, lastRunning :: Maybe POSIXTime
	-- True when the sanity checker is running
	, sanityCheckRunning :: Bool
	-- Last time the sanity checker ran
	, lastSanityCheck :: Maybe POSIXTime
	-- Currently running file content transfers
	, currentTransfers :: TransferMap
	-- Ordered list of remotes to talk to.
	, knownRemotes :: [Remote]
	-- Clients can use this to wait on changes to the DaemonStatus
	-- and other related things like the TransferQueue.
	, notificationBroadcaster :: NotificationBroadcaster
	}

type TransferMap = M.Map Transfer TransferInfo

{- This TMVar is never left empty, so accessing it will never block. -}
type DaemonStatusHandle = TMVar DaemonStatus

newDaemonStatus :: IO DaemonStatus
newDaemonStatus = do
	nb <- newNotificationBroadcaster
	return $ DaemonStatus
		{ scanComplete = False
		, lastRunning = Nothing
		, sanityCheckRunning = False
		, lastSanityCheck = Nothing
		, currentTransfers = M.empty
		, knownRemotes = []
		, notificationBroadcaster = nb
		}

getDaemonStatus :: DaemonStatusHandle -> IO DaemonStatus
getDaemonStatus = atomically . readTMVar

modifyDaemonStatus_ :: DaemonStatusHandle -> (DaemonStatus -> DaemonStatus) -> IO ()
modifyDaemonStatus_ handle a = modifyDaemonStatus handle $ \s -> (a s, ())

modifyDaemonStatus :: DaemonStatusHandle -> (DaemonStatus -> (DaemonStatus, b)) -> IO b
modifyDaemonStatus handle a = do
	(b, nb) <- atomically $ do
		(s, b) <- a <$> takeTMVar handle
		putTMVar handle s
		return $ (b, notificationBroadcaster s)
	sendNotification nb
	return b

{- Can be used to send a notification that the daemon status, or other
 - associated thing, like the TransferQueue, has changed. -}
notifyDaemonStatusChange :: DaemonStatusHandle -> IO ()
notifyDaemonStatusChange handle = sendNotification
	=<< notificationBroadcaster <$> atomically (readTMVar handle)

{- Updates the cached ordered list of remotes from the list in Annex
 - state. -}
updateKnownRemotes :: DaemonStatusHandle -> Annex ()
updateKnownRemotes dstatus = do
	remotes <- Command.Sync.syncRemotes []
	liftIO $ modifyDaemonStatus_ dstatus $
		\s -> s { knownRemotes = remotes }

{- Load any previous daemon status file, and store it in a MVar for this
 - process to use as its DaemonStatus. Also gets current transfer status. -}
startDaemonStatus :: Annex DaemonStatusHandle
startDaemonStatus = do
	file <- fromRepo gitAnnexDaemonStatusFile
	status <- liftIO $
		catchDefaultIO (readDaemonStatusFile file) =<< newDaemonStatus
	transfers <- M.fromList <$> getTransfers
	remotes <- Command.Sync.syncRemotes []
	liftIO $ atomically $ newTMVar status
		{ scanComplete = False
		, sanityCheckRunning = False
		, currentTransfers = transfers
		, knownRemotes = remotes
		}

{- This writes the daemon status to disk, when it changes, but no more
 - frequently than once every ten minutes.
 -}
daemonStatusThread :: ThreadState -> DaemonStatusHandle -> IO ()
daemonStatusThread st handle = do
	bhandle <- newNotificationHandle
		=<< notificationBroadcaster <$> getDaemonStatus handle
	checkpoint
	runEvery (Seconds tenMinutes) $ do
		waitNotification bhandle
		checkpoint
	where
		checkpoint = do
			status <- getDaemonStatus handle
			file <- runThreadState st $ fromRepo gitAnnexDaemonStatusFile
			writeDaemonStatusFile file status

{- Don't just dump out the structure, because it will change over time,
 - and parts of it are not relevant. -}
writeDaemonStatusFile :: FilePath -> DaemonStatus -> IO ()
writeDaemonStatusFile file status = 
	viaTmp writeFile file =<< serialized <$> getPOSIXTime
	where
		serialized now = unlines
			[ "lastRunning:" ++ show now
			, "scanComplete:" ++ show (scanComplete status)
			, "sanityCheckRunning:" ++ show (sanityCheckRunning status)
			, "lastSanityCheck:" ++ maybe "" show (lastSanityCheck status)
			]

readDaemonStatusFile :: FilePath -> IO DaemonStatus
readDaemonStatusFile file = parse <$> newDaemonStatus <*> readFile file
	where
		parse status = foldr parseline status . lines
		parseline line status
			| key == "lastRunning" = parseval readtime $ \v ->
				status { lastRunning = Just v }
			| key == "scanComplete" = parseval readish $ \v ->
				status { scanComplete = v }
			| key == "sanityCheckRunning" = parseval readish $ \v ->
				status { sanityCheckRunning = v }
			| key == "lastSanityCheck" = parseval readtime $ \v ->
				status { lastSanityCheck = Just v }
			| otherwise = status -- unparsable line
			where
				(key, value) = separate (== ':') line
				parseval parser a = maybe status a (parser value)
				readtime s = do
					d <- parseTime defaultTimeLocale "%s%Qs" s
					Just $ utcTimeToPOSIXSeconds d

{- Checks if a time stamp was made after the daemon was lastRunning.
 -
 - Some slop is built in; this really checks if the time stamp was made
 - at least ten minutes after the daemon was lastRunning. This is to
 - ensure the daemon shut down cleanly, and deal with minor clock skew.
 -
 - If the daemon has never ran before, this always returns False.
 -}
afterLastDaemonRun :: EpochTime -> DaemonStatus -> Bool
afterLastDaemonRun timestamp status = maybe False (< t) (lastRunning status)
	where
		t = realToFrac (timestamp + slop) :: POSIXTime
		slop = fromIntegral tenMinutes

tenMinutes :: Int
tenMinutes = 10 * 60

{- Mutates the transfer map. Runs in STM so that the transfer map can
 - be modified in the same transaction that modifies the transfer queue.
 - Note that this does not send a notification of the change; that's left
 - to the caller. -}
adjustTransfersSTM :: DaemonStatusHandle -> (TransferMap -> TransferMap) -> STM ()
adjustTransfersSTM dstatus a = do
	s <- takeTMVar dstatus
	putTMVar dstatus $ s { currentTransfers = a (currentTransfers s) }

{- Variant that does send notifications. -}
adjustTransfers :: DaemonStatusHandle -> (TransferMap -> TransferMap) -> IO ()
adjustTransfers dstatus a = modifyDaemonStatus_ dstatus $
	\s -> s { currentTransfers = a (currentTransfers s) }

{- Removes a transfer from the map, and returns its info. -}
removeTransfer :: DaemonStatusHandle -> Transfer -> IO (Maybe TransferInfo)
removeTransfer dstatus t = modifyDaemonStatus dstatus go
	where
		go s =
			let (info, ts) = M.updateLookupWithKey
				(\_k _v -> Nothing)
				t (currentTransfers s)
			in (s { currentTransfers = ts }, info)