dispatch incoming requests to their response functions

- contributes to #28

src/Hash2Pub/DHTProtocol.hs

@@ -177,14 +177,28 @@ handleIncomingRequest :: LocalNodeState                     -- ^ the handling no
 handleIncomingRequest ns sendQ msgSet sourceAddr = do
     -- add nodestate to cache
     now <- getPOSIXTime
-    queueAddEntries (Identity . RemoteCacheEntry (sender . head . Set.elems $ msgSet) $ now) ns
-    -- distinguish on whether and how to respond
-    -- create and enqueue ACK
-    -- Idea: only respond with payload on last part (part == parts), problem: need to know partnumber of response from first part on
-    -- 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
-    pure ()
+    aPart <- headMay . Set.elems $ msgSet
+    case aPart of
+      Nothing -> pure ()
+      Just aPart' ->
+        queueAddEntries (Identity . RemoteCacheEntry (sender aPart') $ now) ns
+        -- distinguish on whether and how to respond. If responding, pass message to response generating function and write responses to send queue
+        maybe (pure ()) (\respSet ->
+            forM_ (\resp -> atomically $ writeTQueue sendQ (resp, sourceAddr)))
+            (case action aPart' of
+                Ping -> Just  respondPing ns msgSet
+                Join -> Just respondJoin ns msgSet
+                -- ToDo: figure out what happens if not joined
+                QueryID -> Just respondQueryID ns msgSet
+                -- only when joined
+                Leave -> if isJoined_ ns then Just respondLeave ns msgSet else Nothing
+                -- only when joined
+                Stabilise -> if isJoined_ ns then Just respondStabilise ns msgSet else 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
 
 -- ....... response sending .......