assistant: XMPP git pull and push requests are cached and sent when presence of a new client is detected.

Noticed that, At startup or network reconnect, git push messages were sent,
often before presence info has been gathered, so were not sent to any
buddies.

To fix this, keep track of which buddies have seen such messages,
and when new presence is received from a buddy that has not yet seen it,
resend.

This is done only for push initiation messages, so very little data needs
to be stored.

Assistant/Threads/XMPPClient.hs

@@ -35,7 +35,7 @@ import Data.Time.Clock
 
 {- Whether to include verbose protocol dump in debug output. -}
 protocolDebug :: Bool
-protocolDebug = True
+protocolDebug = False
 
 xmppClientThread :: UrlRenderer -> NamedThread
 xmppClientThread urlrenderer = namedThread "XMPPClient" $
@@ -97,10 +97,10 @@ xmppClient urlrenderer d creds =
 			inAssistant $ debug ["received:", show l]
 		mapM_ (handle selfjid) l
 
-	handle _ (PresenceMessage p) = do
-		
+	handle selfjid (PresenceMessage p) = do
 		void $ inAssistant $ 
 			updateBuddyList (updateBuddies p) <<~ buddyList
+		resendImportantMessages selfjid p
 	handle _ (GotNetMessage QueryPresence) = putStanza gitAnnexSignature
 	handle _ (GotNetMessage (NotifyPush us)) = void $ inAssistant $ pull us
 	handle selfjid (GotNetMessage (PairingNotification stage c u)) =
@@ -114,6 +114,16 @@ xmppClient urlrenderer d creds =
 	handle _ (Unknown _) = noop
 	handle _ (ProtocolError _) = noop
 
+	resendImportantMessages selfjid (Presence { presenceFrom = Just jid }) = do
+		let c = formatJID jid
+		(stored, sent) <- inAssistant $
+			checkImportantNetMessages (formatJID (baseJID jid), c)
+		forM_ (S.toList $ S.difference stored sent) $ \msg -> do
+			inAssistant $ debug ["sending to new client:", show c, show msg]
+			a <- inAssistant $ convertNetMsg (readdressNetMessage msg c) selfjid
+			a
+			inAssistant $ sentImportantNetMessage msg c
+	resendImportantMessages _ _ = noop
 
 data XMPPEvent
 	= GotNetMessage NetMessage
@@ -151,21 +161,27 @@ decodeStanza _ s = [Unknown s]
  - Chat messages must be directed to specific clients, not a base
  - account JID, due to git-annex clients using a negative presence priority.
  - PairingNotification messages are always directed at specific
- - clients, but Pushing messages are sometimes not, and need to be exploded.
+ - clients, but Pushing messages are sometimes not, and need to be exploded
+ - out to specific clients.
+ -
+ - Important messages, not directed at any specific client, 
+ - are cached to be sent later when additional clients connect.
  -}
 relayNetMessage :: JID -> Assistant (XMPP ())
 relayNetMessage selfjid = do
 	msg <- waitNetMessage
 	when protocolDebug $
 		debug ["sending:", show msg]
+	handleImportant msg
 	convert msg
   where
-	convert (NotifyPush us) = return $ putStanza $ pushNotification us
-	convert QueryPresence = return $ putStanza presenceQuery
-	convert (PairingNotification stage c u) = withclient c $ \tojid -> do
-		changeBuddyPairing tojid True
-		return $ putStanza $ pairingNotification stage u tojid selfjid
-	convert (Pushing c pushstage) = withclient c $ \tojid -> do
+	handleImportant msg = case parseJID =<< isImportantNetMessage msg of
+		Just tojid
+			| tojid == baseJID tojid ->
+				storeImportantNetMessage msg (formatJID tojid) $
+					\c -> (baseJID <$> parseJID c) == Just tojid
+		_ -> noop
+	convert (Pushing c pushstage) = withOtherClient selfjid c $ \tojid -> do
 		if tojid == baseJID tojid
 			then do
 				clients <- maybe [] (S.toList . buddyAssistants)
@@ -175,12 +191,29 @@ relayNetMessage selfjid = do
 				return $ forM_ (clients) $ \(Client jid) ->
 					putStanza $ pushMessage pushstage jid selfjid
 			else return $ putStanza $ pushMessage pushstage tojid selfjid
+	convert msg = convertNetMsg msg selfjid
 
-	withclient c a = case parseJID c of
-		Nothing -> return noop
-		Just tojid
-			| tojid == selfjid -> return noop
-			| otherwise -> a tojid
+{- Converts a NetMessage to an XMPP action. -}
+convertNetMsg :: NetMessage -> JID -> Assistant (XMPP ())
+convertNetMsg msg selfjid = convert msg
+  where
+	convert (NotifyPush us) = return $ putStanza $ pushNotification us
+	convert QueryPresence = return $ putStanza presenceQuery
+	convert (PairingNotification stage c u) = withOtherClient selfjid c $ \tojid -> do
+		changeBuddyPairing tojid True
+		return $ putStanza $ pairingNotification stage u tojid selfjid
+	convert (Pushing c pushstage) = withOtherClient selfjid c $ \tojid ->
+		return $ putStanza $  pushMessage pushstage tojid selfjid
+
+withOtherClient :: JID -> ClientID -> (JID -> Assistant (XMPP ())) -> (Assistant (XMPP ()))
+withOtherClient selfjid c a = case parseJID c of
+	Nothing -> return noop
+	Just tojid
+		| tojid == selfjid -> return noop
+		| otherwise -> a tojid
+
+withClient :: ClientID -> (JID -> XMPP ()) -> XMPP ()
+withClient c a = maybe noop a $ parseJID c
 
 {- Runs a XMPP action in a separate thread, using a session to allow it
  - to access the same XMPP client. -}