refactor trying to join on any bootstrap node into own function

contributes to #56

src/Hash2Pub/FediChord.hs

@@ -40,6 +40,7 @@ module Hash2Pub.FediChord (
   , fediChordInit
   , fediChordJoin
   , fediChordBootstrapJoin
+  , tryBootstrapJoining
   , fediMainThreads
   , RealNode (..)
   , nodeStateInit
@@ -166,6 +167,25 @@ fediChordBootstrapJoin nsSTM (joinHost, joinPort) =
                                                    )
        `catch` (\e -> pure . Left $ "Error at bootstrap joining: " <> displayException (e :: IOException))
 
+
+-- | Try joining the DHT through any of the bootstrapping nodes until it succeeds.
+tryBootstrapJoining :: LocalNodeStateSTM -> IO (Either String LocalNodeStateSTM)
+tryBootstrapJoining nsSTM = do
+    bss <- atomically $ do
+        nsSnap <- readTVar nsSTM
+        realNodeSnap <- readTVar $ parentRealNode nsSnap
+        pure $ bootstrapNodes realNodeSnap
+    tryJoining bss
+  where
+    tryJoining (bn:bns) = do
+        j <- fediChordBootstrapJoin nsSTM bn
+        case j of
+          Left err     -> putStrLn ("join error: " <> err) >> tryJoining bns
+          Right joined -> pure $ Right joined
+    tryJoining [] = pure $ Left "Exhausted all bootstrap points for joining."
+
+
+
 -- | join a node to the DHT, using the provided cache snapshot for resolving the new
 -- node's position.
 fediChordJoin :: NodeCache                          -- ^ a snapshot of the NodeCache to