make request and response distinguishable

Hash2Pub/FediChord.asn1

@@ -7,11 +7,11 @@ Domain ::= VisibleString
 Action ::= ENUMERATED {queryID, join, leave, stabilise, ping}
 
 Request ::= SEQUENCE {
+	action			Action,
 	requestID		INTEGER,
 	senderID		NodeID,
 	parts			INTEGER,	-- number of message parts
 	part			INTEGER,	-- part number of this message
-	action			Action,
 	actionPayload	CHOICE {
 		queryIDSendPayload		QueryIDSendPayload,
 		joinSendPayload			JoinSendPayload,
@@ -21,6 +21,9 @@ Request ::= SEQUENCE {
 		}
 	}
 
+-- idea: different message layouts as a way of distinguishing between
+-- request and response instead of explicit flag
+
 Response ::= SEQUENCE {
 	responseTo		INTEGER,
 	senderID		NodeID,

Hash2Pub/src/Hash2Pub/ASN1Coding.hs

@@ -114,14 +114,23 @@ encodeJoinReceivePayload succ' pred' ncache =
 encodeJoinSendPayload :: NodeState -> [ASN1]
 encodeJoinSendPayload = encodeNodeState
 
+encodePingSendPayload :: [ASN1]
+encodePingSendPayload = Null
+
+encodePingReceivePayload :: [NodeState] -> [ASN1]
+encodePingReceivePayload nss =
+    Start Sequence
+  : concatMap encodeNodeState nss
+  ++ [End Sequence]
+
 encodeRequest :: Integer -> NodeID -> Integer -> Integer -> Action -> [ASN1] -> [ASN1]
 encodeRequest requestID senderID parts part action payload = [
     Start Sequence
+  , Enumerated . fromIntegral . fromEnum $ action
   , IntVal requestID
   , IntVal . getNodeID $ senderID
   , IntVal parts
-  , IntVal part
-  , Enumerated . fromIntegral . fromEnum $ action]
+  , IntVal part ]
   ++ payload
 
 encodeResponse :: Integer -> NodeID -> Integer -> Integer -> Action -> [ASN1] -> [ASN1]
@@ -134,11 +143,55 @@ encodeResponse responseTo senderID parts part action payload = [
   , Enumerated . fromIntegral . fromEnum $ action]
   ++ payload
 
-encodePingSendPayload :: [ASN1]
-encodePingSendPayload = Null
+-- ===== parser combinators =====
 
-encodePingReceivePayload :: [NodeState] -> [ASN1]
-encodePingReceivePayload nss =
-    Start Sequence
-  : concatMap encodeNodeState nss
-  ++ [End Sequence]
+parseMessage :: ParseASN1 () -- todo: change type
+parseMessage = do
+-- request and response messages are distiguishable by their structure,
+-- see ASN.1 schema
+    first <- getNext
+    case first of
+      Enumerated a -> parseRequest . toEnum $ a
+      IntVal i -> parseResponse i
+
+parseRequest :: Action -> ParseASN1 () -- todo: change type
+parseRequest action = do
+    requestID <- parseInteger
+    senderID <- (fromInteger <$> parseInteger :: ParseASN1 NodeID)
+    parts <- parseInteger
+    part <- parseInteger
+    payload <- onNextContainer Sequence $
+        case action of
+            QueryID -> parseQueryIDRequest
+            Join -> parseJoinRequest
+            Leave -> parseLeaveRequest
+            Stabilise -> parseStabiliseRequest
+            Ping -> parsePingRequest
+
+    return ()
+
+parseResponse :: Integer -> ParseASN1 () -- todo: change type
+parseResponse responseTo = do
+    senderID <- (fromInteger <$> parseInteger :: ParseASN1 NodeID)
+    parts <- parseInteger
+    part <- parseInteger
+    action <- (parseEnum :: ParseASN1 Action)
+    payload <- onNextContainer Sequence $
+        case action of
+            QueryID -> parseQueryIDResponse
+            Join -> parseJoinResponse
+            Leave -> parseLeaveResponse
+            Stabilise -> parseStabiliseResponse
+            Ping -> parsePingResponse
+
+    return ()
+
+parseInteger :: ParseASN1 Integer
+parseInteger = do
+    IntVal parsed <- getNext
+    return parsed
+
+parseEnum :: Enum a => ParseASN1 a
+parseEnum = do
+    Enumerated en <- getNext
+    return $ toEnum . fromIntegral $ en