improve encoding documentation and syntax

Hash2Pub/src/Hash2Pub/ASN1Coding.hs

@@ -34,6 +34,7 @@ data FediChordMessage =
   , sender          :: NodeState
   , parts           :: Integer
   , part            :: Integer
+  -- ^ part starts at 0
   , action          :: Action
   , payload         :: ActionPayload
                         }
@@ -81,7 +82,9 @@ data ActionPayload =
 -- Only some kinds of payloads can be split, and only to a limited number of parts.
 -- This function only deals with potentially large payload types and passes the
 -- rest as-is.
-splitPayload :: Int -> ActionPayload -> [ActionPayload]
+splitPayload :: Int                 -- number of parts to split payload into
+             -> ActionPayload       -- payload to be split
+             -> [ActionPayload]     -- list of smaller payloads
 splitPayload numParts pl@LeaveRequestPayload{} = [
     LeaveRequestPayload {
         leaveSuccessors = fromMaybe [] $ headMay . drop thisPart $ listInto numParts $ leaveSuccessors pl
@@ -125,7 +128,10 @@ chunkLength numParts totalSize = ceiling $ (realToFrac totalSize :: Double) / re
 -- The number of parts per message is limited to 150 for DOS protection reasons.
 -- The returned byte strings might exceed the desired maximum length, as only the payload (and not all of them)
 -- can be split into multiple parts.
-serialiseMessage :: FediChordMessage -> Int -> [BS.ByteString]
+serialiseMessage :: FediChordMessage        -- mesage to be serialised in preparation for sending
+                 -> Int                     -- maximum message size in bytes
+                 -> [BS.ByteString]         -- list of ASN.1 DER encoded messages together representing
+                                            -- the contents of the input message
 serialiseMessage msg maxBytesLength =
     splitPayloadUntilSmallEnough 1
     where
@@ -155,31 +161,33 @@ serialiseMessage msg maxBytesLength =
 
 -- ===== encoding functions =====
 
+-- encode a message 'ActionPayload' according to its type,
+-- indicated by the data constructor, as ASN.1
 encodePayload :: ActionPayload -> [ASN1]
 encodePayload LeaveResponsePayload = [Null]
-encodePayload payload@LeaveRequestPayload{} = 
+encodePayload payload'@LeaveRequestPayload{} = 
     Start Sequence
   : Start Sequence
-  : (map (IntVal . getNodeID) $ leaveSuccessors payload)
+  : map (IntVal . getNodeID) (leaveSuccessors payload')
   ++ [End Sequence
   , Start Sequence]
-  ++ (map (IntVal . getNodeID) $ leavePredecessors payload)
+  ++ map (IntVal . getNodeID) (leavePredecessors payload')
   ++ [End Sequence
   , End Sequence]
 -- currently StabiliseResponsePayload and LeaveRequestPayload are equal
-encodePayload payload@StabiliseResponsePayload{} = 
+encodePayload payload'@StabiliseResponsePayload{} = 
     Start Sequence
   : Start Sequence
-  : (map (IntVal . getNodeID) $ stabiliseSuccessors payload)
+  : map (IntVal . getNodeID) (stabiliseSuccessors payload')
   ++ [End Sequence
   , Start Sequence]
-  ++ (map (IntVal . getNodeID) $ stabilisePredecessors payload)
+  ++ map (IntVal . getNodeID) (stabilisePredecessors payload')
   ++ [End Sequence
   , End Sequence]
-encodePayload payload@StabiliseRequestPayload = [Null]
+encodePayload payload'@StabiliseRequestPayload = [Null]
-encodePayload payload@QueryIDResponsePayload{} = 
+encodePayload payload'@QueryIDResponsePayload{} = 
   let
-    resp = queryResult payload
+    resp = queryResult payload'
   in
     Start Sequence
   : encodeQueryResult resp
@@ -190,33 +198,32 @@ encodePayload payload@QueryIDResponsePayload{} =
           : (concatMap encodeCacheEntry . Set.elems $ entrySet)
           ++ [End Sequence]
   ++ [End Sequence]
-encodePayload payload@QueryIDResponsePayload{} = [
+encodePayload payload'@QueryIDRequestPayload{} = [
     Start Sequence
-  , IntVal . getNodeID $ queryTargetID payload
+  , IntVal . getNodeID $ queryTargetID payload'
-  , IntVal $ queryLBestNodes payload
+  , IntVal $ queryLBestNodes payload'
   , End Sequence
                                                  ]
 -- | encodes the @JoinResponsePayload@ ASN.1 type
-encodePayload payload@JoinResponsePayload{} =
+encodePayload payload'@JoinResponsePayload{} =
     Start Sequence
   : Start Sequence
-  : (map (IntVal . getNodeID) $ joinSuccessors payload)
+  : map (IntVal . getNodeID) (joinSuccessors payload')
   ++ [End Sequence
   , Start Sequence]
-  ++ (map (IntVal . getNodeID) $ joinPredecessors payload)
+  ++ map (IntVal . getNodeID) (joinPredecessors payload')
   ++ [End Sequence
     , Start Sequence]
-  ++ (concatMap encodeCacheEntry $ joinCache payload)
+  ++ concatMap encodeCacheEntry (joinCache payload')
   ++ [End Sequence
     , End Sequence]
-encodePayload payload@JoinRequestPayload{} = [Null]
+encodePayload payload'@JoinRequestPayload{} = [Null]
 encodePayload PingRequestPayload{} = [Null]
-encodePayload payload@PingResponsePayload{} =
+encodePayload payload'@PingResponsePayload{} =
     Start Sequence
-  : (concatMap encodeNodeState $ pingNodeStates payload)
+  : concatMap encodeNodeState (pingNodeStates payload')
   ++ [End Sequence]
 
-
 encodeNodeState :: NodeState -> [ASN1]
 encodeNodeState ns = [
     Start Sequence