fix RingMap function types

src/Hash2Pub/FediChordTypes.hs

@@ -2,6 +2,7 @@
 {-# LANGUAGE DerivingStrategies         #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE OverloadedStrings          #-}
+{-# LANGUAGE RankNTypes                 #-}
 
 module Hash2Pub.FediChordTypes (
     NodeID -- abstract, but newtype constructors cannot be hidden
@@ -239,7 +240,7 @@ instance HasKeyID CacheEntry where
 type NodeCache = RingMap CacheEntry
 
 -- | generic data structure for holding elements with a key and modular lookup
-newtype RingMap a = RingMap { getRingMap :: HasKeyID a => Map.Map NodeID (RingEntry a) } deriving (Show, Eq)
+newtype RingMap a = RingMap { getRingMap :: HasKeyID a => Map.Map NodeID (RingEntry a) }
 
 -- | An entry of the 'nodeCache' can hold 2 different kinds of data.
 -- Type variable @a@ should be of type class 'NodeState', but I do not want to use GADTs here.
@@ -253,7 +254,7 @@ data CacheEntry = CacheEntry Bool RemoteNodeState POSIXTime
 
 -- | as a compromise, only KeyEntry components are ordered by their NodeID
 -- while ProxyEntry components should never be tried to be ordered.
-instance Ord RingEntry where
+instance (HasKeyID a, Eq a) => Ord (RingEntry a) where
     a `compare` b = compare (extractID a) (extractID b)
         where
             extractID (KeyEntry e) = getKeyID e
@@ -274,18 +275,20 @@ instance Enum ProxyDirection where
 cacheEntries :: NodeCache -> [CacheEntry]
 cacheEntries = mapMaybe extractNodeEntries . Map.elems . getRingMap
     where
-  extractNodeEntries (ProxyEntry _ possibleEntry) = possibleEntry
+  extractNodeEntries :: RingEntry CacheEntry  -> Maybe CacheEntry
-  extractNodeEntries (KeyEntry entry)             = Just entry
+  extractNodeEntries (ProxyEntry _ (Just (KeyEntry entry))) = Just entry
+  extractNodeEntries (KeyEntry entry)                       = Just entry
+  extractNodeEntries _                                      = Nothing
 
 -- | An empty @NodeCache@ needs to be initialised with 2 proxy entries,
 -- linking the modular name space together by connecting @minBound@ and @maxBound@
 initRMap :: HasKeyID a => RingMap a
-initRMap = RingMap . Map.fromList . proxyEntry <$> [(maxBound, (minBound, Forwards)), (minBound, (maxBound, Backwards))]
+initRMap = RingMap . Map.fromList $ proxyEntry <$> [(maxBound, (minBound, Forwards)), (minBound, (maxBound, Backwards))]
   where
     proxyEntry (from,to) = (from, ProxyEntry to Nothing)
 
 initCache :: NodeCache
-initCache = initRingMap
+initCache = initRMap
 
 -- | Maybe returns the entry stored at given key
 rMapLookup :: HasKeyID a
@@ -293,8 +296,9 @@ rMapLookup :: HasKeyID a
            -> RingMap a    -- ^lookup cache
            -> Maybe a
 rMapLookup key rmap = case Map.lookup key $ getRingMap rmap of
-                          Just (ProxyEntry _ result) -> result
+                          Just (ProxyEntry _ (Just (KeyEntry result))) -> Just result
-                          res                        -> res
+                          Just (KeyEntry res)                        -> Just res
+                          _     -> Nothing
 
 cacheLookup :: NodeID       -- ^lookup key
             -> NodeCache    -- ^lookup cache
@@ -304,8 +308,8 @@ cacheLookup = rMapLookup
 -- | a wrapper around lookup functions, making the lookup redirectable by a @ProxyEntry@
 -- to simulate a modular ring
 lookupWrapper :: HasKeyID a
-              => (NodeID -> Map.Map NodeID a -> Maybe (NodeID, a))
+              => (NodeID -> Map.Map NodeID (RingEntry a) -> Maybe (NodeID, RingEntry a))
-              -> (NodeID -> Map.Map NodeID a -> Maybe (NodeID, a))
+              -> (NodeID -> Map.Map NodeID (RingEntry a) -> Maybe (NodeID, RingEntry a))
               -> ProxyDirection
               -> NodeID
               -> RingMap a
@@ -313,7 +317,7 @@ lookupWrapper :: HasKeyID a
 lookupWrapper f fRepeat direction key rmap =
     case f key $ getRingMap rmap of
         -- the proxy entry found holds a
-        Just (_, ProxyEntry _ (Just entry@KeyEntry{})) -> Just entry
+        Just (_, ProxyEntry _ (Just (KeyEntry entry))) -> Just entry
         -- proxy entry holds another proxy entry, this should not happen
         Just (_, ProxyEntry _ (Just (ProxyEntry _ _))) -> Nothing
         -- proxy entry without own entry is a pointer on where to continue
@@ -326,10 +330,10 @@ lookupWrapper f fRepeat direction key rmap =
                then lookupWrapper fRepeat fRepeat direction newKey rmap
                else Nothing
         -- normal entries are returned
-        Just (_, entry@KeyEntry{}) -> Just entry
+        Just (_, (KeyEntry entry)) -> Just entry
         Nothing -> Nothing
   where
-    rMapNotEmpty :: RingMap a -> Bool
+    rMapNotEmpty :: (HasKeyID a) => RingMap a -> Bool
     rMapNotEmpty rmap' = (Map.size (getRingMap rmap') > 2)     -- there are more than the 2 ProxyEntries
                    || isJust (rMapLookup minBound rmap') -- or one of the ProxyEntries holds a node
                    || isJust (rMapLookup maxBound rmap')