From 29d39811c5b023f43168a544dd53d52a53eb29a0 Mon Sep 17 00:00:00 2001
From: Neil Mayhew <neil.mayhew@iohk.io>
Date: Tue, 28 Nov 2023 17:23:10 -0700
Subject: [PATCH] Refactor to share more code between socket and chan ledger
 event handlers

---
 cardano-node/src/Cardano/Node/LedgerEvent.hs | 63 ++++++++++----------
 1 file changed, 31 insertions(+), 32 deletions(-)

diff --git a/cardano-node/src/Cardano/Node/LedgerEvent.hs b/cardano-node/src/Cardano/Node/LedgerEvent.hs
index d76255d7c75..cfb5ad6362d 100644
--- a/cardano-node/src/Cardano/Node/LedgerEvent.hs
+++ b/cardano-node/src/Cardano/Node/LedgerEvent.hs
@@ -11,6 +11,7 @@
 {-# LANGUAGE PartialTypeSignatures      #-}
 {-# LANGUAGE RankNTypes                 #-}
 {-# LANGUAGE ScopedTypeVariables        #-}
+{-# LANGUAGE TupleSections              #-}
 {-# LANGUAGE TypeApplications           #-}
 {-# LANGUAGE TypeOperators              #-}
 {-# LANGUAGE UndecidableInstances       #-}
@@ -59,6 +60,7 @@ module Cardano.Node.LedgerEvent (
 
 import           Cardano.Prelude hiding (All, Sum)
 
+import           Control.Arrow ((&&&))
 import           Control.Monad.Fail (MonadFail(..))
 import           Cardano.Ledger.Binary (DecCBOR(..), EncCBOR(..), Version,
                    decodeFull', fromCBOR, serialize', toCBOR)
@@ -731,8 +733,8 @@ instance DecCBOR AnchoredEvent where
       <! From
       <! From
 
-serializeAnchoredEvent :: Version -> AnchoredEvent -> ByteString
-serializeAnchoredEvent version event =
+serializeAnchoredEvent :: (Version, AnchoredEvent) -> ByteString
+serializeAnchoredEvent (version, event) =
   CBOR.toStrictByteString encoding
  where
   encoding =
@@ -744,7 +746,7 @@ serializeAnchoredEvent version event =
 
 deserializeAnchoredEvent
   :: LBS.ByteString
-  -> Either CBOR.DeserialiseFailure (LBS.ByteString, AnchoredEvent)
+  -> Either CBOR.DeserialiseFailure (LBS.ByteString, (Version, AnchoredEvent))
 deserializeAnchoredEvent =
   CBOR.deserialiseFromBytes decoder
  where
@@ -753,7 +755,7 @@ deserializeAnchoredEvent =
     _ <- CBOR.decodeListLen
     version <- fromCBOR
     bytes <- CBOR.decodeBytes
-    either (fail . show) pure (decodeFull' version bytes)
+    either (fail . show) (pure . (version,)) $ decodeFull' version bytes
 
 -- IO action to read ledger events in binary form
 foldEvent
@@ -769,7 +771,7 @@ foldEvent h st0 fn =
       if eof then
         pure st
       else do
-        (events, event) <- either (panic . show) pure $ deserializeAnchoredEvent bytes
+        (events, (_version, event)) <- either (panic . show) pure $ deserializeAnchoredEvent bytes
         st' <- fn st event
         go st' events
 
@@ -779,13 +781,13 @@ withLedgerEventsServerStream
   :: PortNumber
   -> (StandardLedgerEventHandler -> IO ())
   -> IO ()
-withLedgerEventsServerStream port handler = do
+withLedgerEventsServerStream port action = do
   withSocketsDo $ do
     bracket open closeSockets go
  where
   go s = do
     h <- socketToHandle s WriteMode
-    handler $ LedgerEventHandler $ writeLedgerEvents h
+    action $ mkLedgerEventHandler (writeAnchoredEvent h)
 
   open = do
     sock <- socket AF_INET Stream defaultProtocol
@@ -797,21 +799,15 @@ withLedgerEventsServerStream port handler = do
 
   closeSockets = close
 
-  writeLedgerEvents h ph headerHash slotNo blockNo events = do
-    forM_ events $ \event -> do
-      case fromAuxLedgerEvent event of
-        Nothing -> pure ()
-        Just e -> do
-          let chainHashToHeaderHash GenesisHash = Origin
-              chainHashToHeaderHash (BlockHash bh) = At bh
-          let anchoredEvent = AnchoredEvent (getOneEraHash <$> chainHashToHeaderHash ph) (getOneEraHash headerHash) slotNo blockNo e
-          catch (BS.hPut h $ serializeAnchoredEvent (eventCodecVersion event) anchoredEvent) $ \case
-            -- If the client closes the socket, we continue running the node, but ignore the events.
-            IOError { ioe_type = ResourceVanished } -> do
-              pure ()
-            err -> do
-              print err
-              throwIO err
+  writeAnchoredEvent h = handle errHandler . BS.hPut h . serializeAnchoredEvent
+    where
+      errHandler = \case
+        -- If the client closes the socket, we continue running the node, but ignore the events.
+        IOError { ioe_type = ResourceVanished } -> do
+          pure ()
+        err -> do
+          print err
+          throwIO err
 
 withLedgerEventsChan
   :: (LedgerEventWriter -> LedgerEventReader -> IO a)
@@ -820,8 +816,8 @@ withLedgerEventsChan action = do
   chan <- newTChanIO
   action (atomically . writeTChan chan) (atomically $ readTChan chan)
 
-type LedgerEventWriter = AnchoredEvent -> IO ()
-type LedgerEventReader = IO AnchoredEvent
+type LedgerEventWriter = (Version, AnchoredEvent) -> IO ()
+type LedgerEventReader = IO (Version, AnchoredEvent)
 
 mkLedgerEventHandler
   :: LedgerEventWriter
@@ -835,15 +831,18 @@ mkAnchoredEvents
   -> SlotNo
   -> BlockNo
   -> [AuxLedgerEvent (LedgerState StandardCrypto)]
-  -> [AnchoredEvent]
+  -> [(Version, AnchoredEvent)]
 mkAnchoredEvents prevHash headerHash slotNo blockNo auxEvents =
-  [ AnchoredEvent
-    (getOneEraHash <$> chainHashToOriginHash prevHash)
-    (getOneEraHash headerHash)
-    slotNo
-    blockNo
-    ledgerEvent
-  | Just ledgerEvent <- map fromAuxLedgerEvent auxEvents
+  [ (version,
+      AnchoredEvent
+        (getOneEraHash <$> chainHashToOriginHash prevHash)
+        (getOneEraHash headerHash)
+        slotNo
+        blockNo
+        ledgerEvent
+    )
+  | (version, Just ledgerEvent)
+      <- (eventCodecVersion &&& fromAuxLedgerEvent) <$> auxEvents
   ]
   where
     chainHashToOriginHash :: ChainHash b -> WithOrigin (HeaderHash b)