send notifications when the TransferQueue is changed

The fun part was making it move things from TransferQueue to currentTransfers
entirely atomically. Which will avoid inconsistent display if the WebApp
renders the current status at just the wrong time. STM to the rescue!

Assistant/TransferQueue.hs

@@ -23,6 +23,7 @@ import Types.Remote
 import qualified Remote
 
 import Control.Concurrent.STM
+import qualified Data.Map as M
 
 {- The transfer queue consists of a channel listing the transfers to make;
  - the size of the queue is also tracked, and a list is maintained
@@ -58,8 +59,8 @@ stubInfo f r = TransferInfo
 
 {- Adds transfers to queue for some of the known remotes. -}
 queueTransfers :: Schedule -> TransferQueue -> DaemonStatusHandle -> Key -> AssociatedFile -> Direction -> Annex ()
-queueTransfers schedule q daemonstatus k f direction = do
-	rs <- knownRemotes <$> liftIO (getDaemonStatus daemonstatus)
+queueTransfers schedule q dstatus k f direction = do
+	rs <- knownRemotes <$> liftIO (getDaemonStatus dstatus)
 	mapM_ go =<< sufficientremotes rs
 	where
 		sufficientremotes rs
@@ -80,37 +81,48 @@ queueTransfers schedule q daemonstatus k f direction = do
 			, transferKey = k
 			, transferUUID = Remote.uuid r
 			}
-		go r = liftIO $ atomically $
-			enqueue schedule q (gentransfer r) (stubInfo f r)
+		go r = liftIO $
+			enqueue schedule q dstatus (gentransfer r) (stubInfo f r)
 
-enqueue :: Schedule -> TransferQueue -> Transfer -> TransferInfo -> STM ()
-enqueue schedule q t info
+enqueue :: Schedule -> TransferQueue -> DaemonStatusHandle -> Transfer -> TransferInfo -> IO ()
+enqueue schedule q dstatus t info
 	| schedule == Next = go unGetTChan (new:)
 	| otherwise = go writeTChan (\l -> l++[new])
 	where
 		new = (t, info)
 		go modqueue modlist = do
-			void $ modqueue (queue q) new
-			void $ modifyTVar' (queuesize q) succ
-			void $ modifyTVar' (queuelist q) modlist
+			atomically $ do
+				void $ modqueue (queue q) new
+				void $ modifyTVar' (queuesize q) succ
+				void $ modifyTVar' (queuelist q) modlist
+			void $ notifyDaemonStatusChange dstatus
 
 {- Adds a transfer to the queue. -}
-queueTransfer :: Schedule -> TransferQueue -> AssociatedFile -> Transfer -> Remote -> IO ()
-queueTransfer schedule q f t remote = atomically $
-	enqueue schedule q t (stubInfo f remote)
+queueTransfer :: Schedule -> TransferQueue -> DaemonStatusHandle -> AssociatedFile -> Transfer -> Remote -> IO ()
+queueTransfer schedule q dstatus f t remote =
+	enqueue schedule q dstatus t (stubInfo f remote)
 
 {- Blocks until the queue is no larger than a given size, and then adds a
  - transfer to the queue. -}
-queueTransferAt :: Integer -> Schedule -> TransferQueue -> AssociatedFile -> Transfer -> Remote -> IO ()
-queueTransferAt wantsz schedule q f t remote = atomically $ do
-	sz <- readTVar (queuesize q)
-	if sz <= wantsz
-		then enqueue schedule q t (stubInfo f remote)
-		else retry -- blocks until queuesize changes
+queueTransferAt :: Integer -> Schedule -> TransferQueue -> DaemonStatusHandle -> AssociatedFile -> Transfer -> Remote -> IO ()
+queueTransferAt wantsz schedule q dstatus f t remote = do
+	atomically $ do
+		sz <- readTVar (queuesize q)
+		if sz <= wantsz
+			then return ()
+			else retry -- blocks until queuesize changes
+	enqueue schedule q dstatus t (stubInfo f remote)
 
-{- Blocks until a pending transfer is available from the queue. -}
-getNextTransfer :: TransferQueue -> IO (Transfer, TransferInfo)
-getNextTransfer q = atomically $ do
+{- Blocks until a pending transfer is available from the queue.
+ - The transfer is removed from the transfer queue, and added to
+ - the daemon status currentTransfers map. This is done in a single STM
+ - transaction, so there is no window where an observer sees an
+ - inconsistent status. -}
+getNextTransfer :: TransferQueue -> DaemonStatusHandle -> IO (Transfer, TransferInfo)
+getNextTransfer q dstatus = atomically $ do
 	void $ modifyTVar' (queuesize q) pred
 	void $ modifyTVar' (queuelist q) (drop 1)
-	readTChan (queue q)
+	r@(t, info) <- readTChan (queue q)
+	adjustTransfersSTM dstatus $
+		M.insertWith' const t info
+	return r