xmpp buddy list tracking

Assistant/Types/Buddies.hs

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+{- git-annex assistant buddies
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE CPP #-}
+
+module Assistant.Types.Buddies where
+
+import Common.Annex
+
+import qualified Data.Map as M
+import Control.Concurrent.STM
+import Utility.NotificationBroadcaster
+
+{- When XMPP is enabled, this is an XMPP buddy map.
+ - Otherwise, it's an empty map, for simplicity. -}
+#ifdef WITH_XMPP
+import Assistant.XMPP.Buddies
+#else
+type Buddies = M.Map String Buddy
+data Buddy
+	deriving (Eq)
+#endif
+
+{- A list of buddies, and a way to notify when it changes. -}
+type BuddyList = (TMVar Buddies, NotificationBroadcaster)
+
+noBuddies :: Buddies
+noBuddies = M.empty
+
+newBuddyList :: IO BuddyList
+newBuddyList = (,)
+	<$> atomically (newTMVar noBuddies)
+	<*> newNotificationBroadcaster
+
+getBuddyList :: BuddyList -> IO [Buddy]
+getBuddyList (v, _) = M.elems <$> atomically (readTMVar v)
+
+{- Applies a function to modify the buddy list, and if it's changed,
+ - sends notifications to any listeners. -}
+updateBuddyList :: (Buddies -> Buddies) -> BuddyList -> IO ()
+updateBuddyList a (v, caster) = do
+	changed <- atomically $ do
+		buds <- takeTMVar v
+		let buds' = a buds
+		putTMVar v buds'
+		return $ buds /= buds'
+	when changed $
+		sendNotification caster
+
+{- Allocates a notification handle for a client to use to listen for
+ - changes to the buddy list. -}
+newBuddyListNotificationHandle :: BuddyList -> IO NotificationHandle
+newBuddyListNotificationHandle (_, caster) = newNotificationHandle caster