Correct parsing of memos

src/ZGoTx.hs

@@ -106,7 +106,7 @@ data ZGoMemo =
     , m_address :: Maybe T.Text
     , m_payment :: Bool
     }
-  deriving (Eq)
+  deriving (Eq, Show)
 
 data MemoToken
   = Login !U.UUID
@@ -174,21 +174,24 @@ pZGoMemo = do
   tks <- some pMemo
   pure $ ZGoMemo (isSession tks) (isAddress tks) (isPayment tks)
   where
+    isPayment [] = False
     isPayment tks =
       not (null tks) &&
       case head tks of
         PayMsg x -> True
-        _ -> False
+        _ -> isPayment $ tail tks
+    isAddress [] = Nothing
     isAddress tks =
       if not (null tks)
         then case head tks of
                Address x -> Just x
-               _ -> Nothing
+               _ -> isAddress $ tail tks
         else Nothing
+    isSession [] = Nothing
     isSession tks =
       if not (null tks)
         then case head tks of
                Login x -> Just x
                PayMsg y -> Just y
-               _ -> Nothing
+               _ -> isSession $ tail tks
         else Nothing