convert Watcher thread to Assistant monad

This is a nice win; much less code runs in Annex, so other threads have
more chances to run concurrently.

I do notice that renaming a file has gone from 1 to 2 commits. I think this
is due to the above improvement letting the committer run more frequently,
so it commits the rm first.

4 files changed, 89 insertions, 88 deletions

diff --git a/Assistant.hs b/Assistant.hs
index 8a1be3130..07f022aa6 100644
--- a/Assistant.hs
+++ b/Assistant.hs
@@ -215,7 +215,7 @@ startAssistant assistant daemonize webappwaiter = withThreadState $ \st -> do
 #ifdef WITH_XMPP
 			, assist $ pushNotifierThread st dstatus pushnotifier
 #endif
-			, watch $ watchThread st dstatus transferqueue changechan
+			, watch $ watchThread
 			]
 		liftIO waitForTermination
 
diff --git a/Assistant/Changes.hs b/Assistant/Changes.hs
index cccc372c1..b20dce09a 100644
--- a/Assistant/Changes.hs
+++ b/Assistant/Changes.hs
@@ -8,7 +8,6 @@
 module Assistant.Changes where
 
 import Common.Annex
-import qualified Annex.Queue
 import Types.KeySource
 import Utility.TSet
 
@@ -39,19 +38,15 @@ newChangeChan :: IO ChangeChan
 newChangeChan = newTSet
 
 {- Handlers call this when they made a change that needs to get committed. -}
-madeChange :: FilePath -> ChangeType -> Annex (Maybe Change)
-madeChange f t = do
-	-- Just in case the commit thread is not flushing the queue fast enough.
-	Annex.Queue.flushWhenFull
-	liftIO $ Just <$> (Change <$> getCurrentTime <*> pure f <*> pure t)
+madeChange :: FilePath -> ChangeType -> IO (Maybe Change)
+madeChange f t = Just <$> (Change <$> getCurrentTime <*> pure f <*> pure t)
 
-noChange :: Annex (Maybe Change)
+noChange :: IO (Maybe Change)
 noChange = return Nothing
 
 {- Indicates an add needs to be done, but has not started yet. -}
-pendingAddChange :: FilePath -> Annex (Maybe Change)
-pendingAddChange f =
-	liftIO $ Just <$> (PendingAddChange <$> getCurrentTime <*> pure f)
+pendingAddChange :: FilePath -> IO (Maybe Change)
+pendingAddChange f = Just <$> (PendingAddChange <$> getCurrentTime <*> pure f)
 
 isPendingAddChange :: Change -> Bool
 isPendingAddChange (PendingAddChange {}) = True
diff --git a/Assistant/Threads/SanityChecker.hs b/Assistant/Threads/SanityChecker.hs
index 6379eee46..d92c6c394 100644
--- a/Assistant/Threads/SanityChecker.hs
+++ b/Assistant/Threads/SanityChecker.hs
@@ -90,9 +90,5 @@ check = do
 		dstatus <- getAssistant daemonStatusHandle
 		liftIO $ void $ addAlert dstatus $ sanityCheckFixAlert msg
 	addsymlink file s = do
-		d <- getAssistant id
-		liftIO $ Watcher.runHandler (threadName d)
-			(threadState d) (daemonStatusHandle d)
-			(transferQueue d) (changeChan d)
-			Watcher.onAddSymlink file s
+		Watcher.runHandler Watcher.onAddSymlink file s
 		insanity $ "found unstaged symlink: " ++ file
diff --git a/Assistant/Threads/Watcher.hs b/Assistant/Threads/Watcher.hs
index 7ab124b14..33d4196da 100644
--- a/Assistant/Threads/Watcher.hs
+++ b/Assistant/Threads/Watcher.hs
@@ -15,7 +15,6 @@ module Assistant.Threads.Watcher (
 ) where
 
 import Assistant.Common
-import Assistant.ThreadedMonad
 import Assistant.DaemonStatus
 import Assistant.Changes
 import Assistant.TransferQueue
@@ -37,9 +36,6 @@ import Git.Types
 import Data.Bits.Utils
 import qualified Data.ByteString.Lazy as L
 
-thisThread :: ThreadName
-thisThread = "Watcher"
-
 checkCanWatch :: Annex ()
 checkCanWatch
 	| canWatch = 
@@ -55,35 +51,42 @@ needLsof = error $ unlines
 	, "Be warned: This can corrupt data in the annex, and make fsck complain."
 	]
 
-watchThread :: ThreadState -> DaemonStatusHandle -> TransferQueue -> ChangeChan -> NamedThread
-watchThread st dstatus transferqueue changechan = NamedThread thisThread $ liftIO $ do
-	void $ watchDir "." ignored hooks startup
-	brokendebug thisThread [ "watching", "."]
-  where
-	startup = startupScan st dstatus
-	hook a = Just $ runHandler thisThread st dstatus transferqueue changechan a
-	hooks = mkWatchHooks
-		{ addHook = hook onAdd
-		, delHook = hook onDel
-		, addSymlinkHook = hook onAddSymlink
-		, delDirHook = hook onDelDir
-		, errHook = hook onErr
+watchThread :: NamedThread
+watchThread = NamedThread "Watcher" $ do
+	startup <- asIO startupScan
+	addhook <- hook onAdd
+	delhook <- hook onDel
+	addsymlinkhook <- hook onAddSymlink
+	deldirhook <- hook onDelDir
+	errhook <- hook onErr
+	let hooks = mkWatchHooks
+		{ addHook = addhook
+		, delHook = delhook
+		, addSymlinkHook = addsymlinkhook
+		, delDirHook = deldirhook
+		, errHook = errhook
 		}
+	void $ liftIO $ watchDir "." ignored hooks startup
+	debug [ "watching", "."]
+  where
+	hook a = Just <$> asIO2 (runHandler a)
 
 {- Initial scartup scan. The action should return once the scan is complete. -}
-startupScan :: ThreadState -> DaemonStatusHandle -> IO a -> IO a
-startupScan st dstatus scanner = do
-	runThreadState st $ showAction "scanning"
-	alertWhile' dstatus startupScanAlert $ do
-		r <- scanner
+startupScan :: IO a -> Assistant a
+startupScan scanner = do
+	liftAnnex $ showAction "scanning"
+	dstatus <- getAssistant daemonStatusHandle
+	alertWhile' dstatus startupScanAlert <~> do
+		r <- liftIO $ scanner
 
 		-- Notice any files that were deleted before
 		-- watching was started.
-		runThreadState st $ do
+		liftAnnex $ do
 			inRepo $ Git.Command.run "add" [Param "--update"]
 			showAction "started"
 		
-		modifyDaemonStatus_ dstatus $ \s -> s { scanComplete = True }
+		liftIO $ modifyDaemonStatus_ dstatus $
+			\s -> s { scanComplete = True }
 
 		return (True, r)
 
@@ -95,52 +98,52 @@ ignored = ig . takeFileName
 	ig ".gitattributes" = True
 	ig _ = False
 
-type Handler = ThreadName -> FilePath -> Maybe FileStatus -> DaemonStatusHandle -> TransferQueue -> Annex (Maybe Change)
+type Handler = FilePath -> Maybe FileStatus -> Assistant (Maybe Change)
 
-{- Runs an action handler, inside the Annex monad, and if there was a
- - change, adds it to the ChangeChan.
+{- Runs an action handler, and if there was a change, adds it to the ChangeChan.
  -
  - Exceptions are ignored, otherwise a whole watcher thread could be crashed.
  -}
-runHandler :: ThreadName -> ThreadState -> DaemonStatusHandle -> TransferQueue -> ChangeChan -> Handler -> FilePath -> Maybe FileStatus -> IO ()
-runHandler threadname st dstatus transferqueue changechan handler file filestatus = void $ do
-	r <- tryIO go
+runHandler :: Handler -> FilePath -> Maybe FileStatus -> Assistant ()
+runHandler handler file filestatus = void $ do
+	r <- tryIO <~> handler file filestatus
 	case r of
-		Left e -> print e
+		Left e -> liftIO $ print e
 		Right Nothing -> noop
-		Right (Just change) -> recordChange changechan change
-  where
-	go = runThreadState st $ handler threadname file filestatus dstatus transferqueue
+		Right (Just change) -> do
+			-- Just in case the commit thread is not
+			-- flushing the queue fast enough.
+			liftAnnex $ Annex.Queue.flushWhenFull
+			flip recordChange change <<~ changeChan
 
 onAdd :: Handler
-onAdd _ file filestatus _ _
-	| maybe False isRegularFile filestatus = pendingAddChange file
-	| otherwise = noChange
+onAdd file filestatus
+	| maybe False isRegularFile filestatus = liftIO $ pendingAddChange file
+	| otherwise = liftIO $ noChange
 
 {- A symlink might be an arbitrary symlink, which is just added.
  - Or, if it is a git-annex symlink, ensure it points to the content
  - before adding it.
  -}
 onAddSymlink :: Handler
-onAddSymlink threadname file filestatus dstatus transferqueue = go =<< Backend.lookupFile file
+onAddSymlink file filestatus = go =<< liftAnnex (Backend.lookupFile file)
   where
 	go (Just (key, _)) = do
-		link <- calcGitLink file key
+		link <- liftAnnex $ calcGitLink file key
 		ifM ((==) link <$> liftIO (readSymbolicLink file))
 			( do
-				s <- liftIO $ getDaemonStatus dstatus
+				s <- daemonStatus
 				checkcontent key s
 				ensurestaged link s
 			, do
-				liftIO $ brokendebug threadname ["fix symlink", file]
 				liftIO $ removeFile file
 				liftIO $ createSymbolicLink link file
-				checkcontent key =<< liftIO (getDaemonStatus dstatus)
+				checkcontent key =<< daemonStatus
 				addlink link
 			)
 	go Nothing = do -- other symlink
 		link <- liftIO (readSymbolicLink file)
-		ensurestaged link =<< liftIO (getDaemonStatus dstatus)
+		ensurestaged link =<< daemonStatus
 
 	{- This is often called on symlinks that are already
 	 - staged correctly. A symlink may have been deleted
@@ -156,41 +159,47 @@ onAddSymlink threadname file filestatus dstatus transferqueue = go =<< Backend.l
 	ensurestaged link daemonstatus
 		| scanComplete daemonstatus = addlink link
 		| otherwise = case filestatus of
-			Just s
-				| not (afterLastDaemonRun (statusChangeTime s) daemonstatus) -> noChange
+			Just s | changedrecently s -> liftIO noChange
 			_ -> addlink link
+	  where
+		changedrecently s = not $
+			afterLastDaemonRun (statusChangeTime s) daemonstatus
 
 	{- For speed, tries to reuse the existing blob for symlink target. -}
 	addlink link = do
-		liftIO $ brokendebug threadname ["add symlink", file]
-		v <- catObjectDetails $ Ref $ ':':file
-		case v of
-			Just (currlink, sha)
-				| s2w8 link == L.unpack currlink ->
+		debug ["add symlink", file]
+		liftAnnex $ do
+			v <- catObjectDetails $ Ref $ ':':file
+			case v of
+				Just (currlink, sha)
+					| s2w8 link == L.unpack currlink ->
+						stageSymlink file sha
+				_ -> do
+					sha <- inRepo $
+						Git.HashObject.hashObject BlobObject link
 					stageSymlink file sha
-			_ -> do
-				sha <- inRepo $
-					Git.HashObject.hashObject BlobObject link
-				stageSymlink file sha
-		madeChange file LinkChange
+		liftIO $ madeChange file LinkChange
 
 	{- When a new link appears, or a link is changed, after the startup
 	 - scan, handle getting or dropping the key's content. -}
 	checkcontent key daemonstatus
 		| scanComplete daemonstatus = do
-			present <- inAnnex key
-			unless present $
-				queueTransfers Next transferqueue dstatus
-					key (Just file) Download
-			handleDrops dstatus present key (Just file)
+			present <- liftAnnex $ inAnnex key
+			dstatus <- getAssistant daemonStatusHandle
+			unless present $ do
+				transferqueue <- getAssistant transferQueue
+				liftAnnex $ queueTransfers Next transferqueue
+					dstatus key (Just file) Download
+			liftAnnex $ handleDrops dstatus present key (Just file)
 		| otherwise = noop
 
 onDel :: Handler
-onDel threadname file _ _dstatus _ = do
-	liftIO $ brokendebug threadname ["file deleted", file]
-	Annex.Queue.addUpdateIndex =<<
-		inRepo (Git.UpdateIndex.unstageFile file)
-	madeChange file RmChange
+onDel file _ = do
+	debug ["file deleted", file]
+	liftAnnex $ 
+		Annex.Queue.addUpdateIndex =<<
+			inRepo (Git.UpdateIndex.unstageFile file)
+	liftIO $ madeChange file RmChange
 
 {- A directory has been deleted, or moved, so tell git to remove anything
  - that was inside it from its cache. Since it could reappear at any time,
@@ -200,18 +209,19 @@ onDel threadname file _ _dstatus _ = do
  - command to get the recursive list of files in the directory, so rm is
  - just as good. -}
 onDelDir :: Handler
-onDelDir threadname dir _ _dstatus _ = do
-	liftIO $ brokendebug threadname ["directory deleted", dir]
-	Annex.Queue.addCommand "rm"
+onDelDir dir _ = do
+	debug ["directory deleted", dir]
+	liftAnnex $ Annex.Queue.addCommand "rm"
 		[Params "--quiet -r --cached --ignore-unmatch --"] [dir]
-	madeChange dir RmDirChange
+	liftIO $ madeChange dir RmDirChange
 
 {- Called when there's an error with inotify or kqueue. -}
 onErr :: Handler
-onErr _ msg _ dstatus _ = do
-	warning msg
+onErr msg _ = do
+	liftAnnex $ warning msg
+	dstatus <- getAssistant daemonStatusHandle
 	void $ liftIO $ addAlert dstatus $ warningAlert "watcher" msg
-	return Nothing
+	liftIO noChange
 
 {- Adds a symlink to the index, without ever accessing the actual symlink
  - on disk. This avoids a race if git add is used, where the symlink is