make local lookup return Sets instead of lists

Hash2Pub/src/Hash2Pub/DHTProtocol.hs

@@ -6,7 +6,9 @@ module Hash2Pub.DHTProtocol
     )
         where
 
-import Data.Maybe (catMaybes)
+import Data.Maybe (maybe)
+import qualified Data.Set as Set
+
 import Hash2Pub.FediChord
   ( NodeID
   , NodeState (..)
@@ -21,7 +23,9 @@ import Hash2Pub.FediChord
   , localCompare
   )
 
-data QueryResponse = FORWARD [CacheEntry] -- ^return closest nodes from local cache.
+import Debug.Trace (trace)
+
+data QueryResponse = FORWARD (Set.Set CacheEntry) -- ^return closest nodes from local cache.
                                           -- whole cache entry is returned for making
                                           -- the entry time stamp available to the
                                           -- protocol serialiser
@@ -37,20 +41,23 @@ incomingQuery ownState nCache lBestNodes targetID
       | (targetID `localCompare`  ownID) `elem` [LT, EQ] && (targetID `localCompare` (head . predecessors) ownState) == GT = FOUND ownState
     -- my interpretation: the "l best next hops" are the l-1 closest preceding nodes and
     -- the closest succeeding node (like with the p initiated parallel queries
-    | otherwise = FORWARD . catMaybes $ closestSuccessor : closestPredecessors
+    | otherwise = trace ("--- Query for " ++ show targetID ++ " wanting " ++ show lBestNodes ++ " results---") $
+        FORWARD $ closestSuccessor `Set.union` closestPredecessors
   where
     ownID = nid ownState
 
-    closestSuccessor :: Maybe CacheEntry
+    closestSuccessor :: Set.Set CacheEntry
-    closestSuccessor = cacheLookupSucc targetID nCache
+    closestSuccessor = maybe Set.empty Set.singleton $ cacheLookupSucc targetID nCache
 
-    closestPredecessors :: [Maybe CacheEntry]
+    closestPredecessors :: Set.Set CacheEntry
     closestPredecessors = closestPredecessor (lBestNodes-1) $ nid ownState
-    closestPredecessor :: (Integral n) => n -> NodeID -> [Maybe CacheEntry]
+    closestPredecessor :: (Integral n, Show n) => n -> NodeID -> Set.Set CacheEntry
-    closestPredecessor 0 _ = []
+    closestPredecessor 0 _ = Set.empty
-    closestPredecessor remainingLookups lastID =
+    closestPredecessor remainingLookups lastID
+      | remainingLookups < 0 = Set.empty
+      | otherwise =
         let result = cacheLookupPred lastID nCache
       in
         case result of
-          Nothing -> []
+          Nothing -> Set.empty
-          Just nPred -> result:closestPredecessor (remainingLookups-1) (nid . cacheGetNodeStateUnvalidated $ nPred)
+          Just nPred -> Set.insert nPred $ closestPredecessor (remainingLookups-1) (nid . cacheGetNodeStateUnvalidated $ nPred)

Hash2Pub/src/Hash2Pub/FediChord.hs

@@ -145,6 +145,14 @@ data CacheEntry =
   | ProxyEntry (NodeID, ProxyDirection) (Maybe CacheEntry)
     deriving (Show, Eq)
 
+-- | as a compromise, only NodeEntry components are ordered by their NodeID
+-- while ProxyEntry components should never be tried to be ordered.
+instance Ord CacheEntry where
+    a `compare` b = compare (extractID a) (extractID b)
+        where
+            extractID (NodeEntry _ eState _) = nid eState
+            extractID (ProxyEntry _ _) = error "proxy entries should never appear outside of the NodeCache"
+
 data ProxyDirection = Backwards | Forwards deriving (Show, Eq)
 
 instance Enum ProxyDirection where