respond to Stabilise requests

src/Hash2Pub/DHTProtocol.hs

@@ -195,22 +195,44 @@ handleIncomingRequest nsSTM sendQ msgSet sourceAddr = do
 --                -- ToDo: figure out what happens if not joined
 --                QueryID -> Just <$> respondQueryID nsSTM msgSet
 --                -- only when joined
---                Leave -> if isJoined_ ns then Just <$> respondLeave nsSTM msgSet else Nothing
+--                Leave -> if isJoined_ ns then Just <$> respondLeave nsSTM msgSet else pure Nothing
 --                -- only when joined
---                Stabilise -> if isJoined_ ns then Just <$> respondStabilise nsSTM msgSet else Nothing
---            )
+                Stabilise -> if isJoined_ ns then Just <$> respondStabilise nsSTM msgSet else pure Nothing
+            )
       -- for single part request, response starts with part number 1. For multipart requests, response starts with part number n+1.
 
       -- TODO: determine request type only from first part, but catch RecSelError on each record access when folding, because otherwise different request type parts can make this crash
       -- TODO: test case: mixed message types of parts
 
-            ) -- placeholder
-
 
 -- ....... response sending .......
 
 -- TODO: could all these respond* functions be in STM instead of IO?
 
+
+-- | respond to stabilise requests by returning successor and predecessor list
+respondStabilise :: LocalNodeStateSTM -> Set.Set FediChordMessage -> IO (Map.Map Integer BS.ByteString)
+respondStabilise nsSTM msgSet = do
+    nsSnap <- readTVarIO nsSTM
+    let
+        aRequestPart = Set.elemAt 0 msgSet
+        responsePayload = StabiliseResponsePayload {
+            stabiliseSuccessors = successors nsSnap
+          , stabilisePredecessors = predecessors nsSnap
+                                                   }
+        stabiliseResponse = Response {
+            responseTo = requestID aRequestPart
+          , senderID = getNid nsSnap
+          , part = if Set.size msgSet == 1 then 1 else fromIntegral $ Set.size msgSet + 1
+          , isFinalPart = False
+          , action = Stabilise
+          , payload = Just responsePayload
+                                }
+    -- TODO: return service endpoint for copying over key data
+    pure $ serialiseMessage sendMessageSize stabiliseResponse
+
+
+-- | respond to Ping request by returning all active vserver NodeStates
 respondPing :: LocalNodeStateSTM -> Set.Set FediChordMessage -> IO (Map.Map Integer BS.ByteString)
 respondPing nsSTM msgSet = do
     -- TODO: respond with all active VS when implementing k-choices