Switch ChainObservation to use HeadObservation

This will allow chain observers to use these valueu directly without
further conversion to 'OnChainTx'. The latter will be the hydra-node
specific type which contains already converted time fields.

The change here is incomplete as HeadObservation is missing several
instances and breaks the explorer API.

Author: ch1bo

hydra-chain-observer/src/Hydra/Blockfrost/ChainObserver.hs

@@ -31,17 +31,17 @@ import Hydra.Cardano.Api (
 import Hydra.Cardano.Api.Prelude (
   BlockHeader (..),
  )
-import Hydra.Chain.Direct.Handlers (convertObservation)
 import Hydra.ChainObserver.NodeClient (
   ChainObservation (..),
   ChainObserverLog (..),
   NodeClient (..),
   ObserverHandler,
-  logOnChainTx,
+  logObservation,
   observeAll,
  )
 import Hydra.Logging (Tracer, traceWith)
 import Hydra.Tx (IsTx (..))
+import Hydra.Tx.Observe (HeadObservation (..))
 
 data APIBlockfrostError
   = BlockfrostError Text
@@ -169,16 +169,15 @@ rollForward tracer prj networkId observerHandler blockConfirmations (blockHash,
 
   -- Collect head observations
   let (adjustedUTxO, observations) = observeAll networkId utxo receivedTxs
-  let onChainTxs = mapMaybe convertObservation observations
-  forM_ onChainTxs (traceWith tracer . logOnChainTx)
+  mapM_ (traceWith tracer) $ mapMaybe logObservation observations
 
   blockNo <- maybe (throwIO $ MissingBlockNo _blockHash) (pure . fromInteger) _blockHeight
-  let observationsAt = ChainObservation point blockNo . Just <$> onChainTxs
+  let observationsAt = ChainObservation point blockNo <$> observations
 
   -- Call observer handler
   observerHandler $
     if null observationsAt
-      then [ChainObservation point blockNo Nothing]
+      then [ChainObservation point blockNo NoHeadTx]
       else observationsAt
 
   -- Next

hydra-chain-observer/src/Hydra/ChainObserver/NodeClient.hs

@@ -13,19 +13,22 @@ import Hydra.Cardano.Api (
   UTxO,
  )
 import Hydra.Cardano.Api.Prelude (TxId)
-import Hydra.Chain (OnChainTx (..))
 import Hydra.Contract (ScriptInfo)
 import Hydra.Ledger.Cardano (adjustUTxO)
 import Hydra.Tx.HeadId (HeadId (..))
-import Hydra.Tx.Observe (HeadObservation (..), observeHeadTx)
+import Hydra.Tx.Observe (AbortObservation (..), CloseObservation (..), CollectComObservation (..), CommitObservation (..), ContestObservation (..), DecrementObservation (..), DepositObservation (..), FanoutObservation (..), HeadObservation (..), IncrementObservation (..), InitObservation (..), RecoverObservation (..), observeHeadTx)
 
 type ObserverHandler m = [ChainObservation] -> m ()
 
 data ChainObservation
   = ChainObservation
   { point :: ChainPoint
   , blockNo :: BlockNo
-  , observedTx :: Maybe (OnChainTx Tx)
+  , -- FIXME: This breaks the explorer interface. Either move 'HeadObservation'
+    -- into similar form, or create a new similar type. Cannot use 'OnChainTx'
+    -- from hydra-node as that contains converted time and requires a
+    -- 'TimeHandle' to create.
+    observed :: HeadObservation
   }
   deriving stock (Eq, Show, Generic)
   deriving anyclass (ToJSON, FromJSON)
@@ -61,19 +64,20 @@ data ChainObserverLog
   deriving stock (Eq, Show, Generic)
   deriving anyclass (ToJSON)
 
-logOnChainTx :: OnChainTx Tx -> ChainObserverLog
-logOnChainTx = \case
-  OnInitTx{headId} -> HeadInitTx{headId}
-  OnCommitTx{headId} -> HeadCommitTx{headId}
-  OnCollectComTx{headId} -> HeadCollectComTx{headId}
-  OnIncrementTx{headId} -> HeadIncrementTx{headId}
-  OnDepositTx{headId} -> HeadDepositTx{headId}
-  OnRecoverTx{headId} -> HeadRecoverTx{headId}
-  OnDecrementTx{headId} -> HeadDecrementTx{headId}
-  OnCloseTx{headId} -> HeadCloseTx{headId}
-  OnFanoutTx{headId} -> HeadFanoutTx{headId}
-  OnAbortTx{headId} -> HeadAbortTx{headId}
-  OnContestTx{headId} -> HeadContestTx{headId}
+logObservation :: HeadObservation -> Maybe ChainObserverLog
+logObservation = \case
+  NoHeadTx -> Nothing
+  Init InitObservation{headId} -> Just HeadInitTx{headId}
+  Commit CommitObservation{headId} -> Just HeadCommitTx{headId}
+  Abort AbortObservation{headId} -> Just HeadAbortTx{headId}
+  CollectCom CollectComObservation{headId} -> Just HeadCollectComTx{headId}
+  Deposit DepositObservation{headId} -> Just HeadDepositTx{headId}
+  Recover RecoverObservation{headId} -> Just HeadRecoverTx{headId}
+  Increment IncrementObservation{headId} -> Just HeadIncrementTx{headId}
+  Decrement DecrementObservation{headId} -> Just HeadDecrementTx{headId}
+  Close CloseObservation{headId} -> Just HeadCloseTx{headId}
+  Contest ContestObservation{headId} -> Just HeadContestTx{headId}
+  Fanout FanoutObservation{headId} -> Just HeadFanoutTx{headId}
 
 observeTx :: NetworkId -> UTxO -> Tx -> (UTxO, Maybe HeadObservation)
 observeTx networkId utxo tx =

hydra-chain-observer/src/Hydra/Ouroborus/ChainObserver.hs

@@ -27,16 +27,16 @@ import Hydra.Cardano.Api (
   pattern Block,
  )
 import Hydra.Chain.CardanoClient (queryTip)
-import Hydra.Chain.Direct.Handlers (convertObservation)
 import Hydra.ChainObserver.NodeClient (
   ChainObservation (..),
   ChainObserverLog (..),
   NodeClient (..),
   ObserverHandler,
-  logOnChainTx,
+  logObservation,
   observeAll,
  )
 import Hydra.Logging (Tracer, traceWith)
+import Hydra.Tx.Observe (HeadObservation (..))
 import Ouroboros.Network.Protocol.ChainSync.Client (
   ChainSyncClient (..),
   ClientStIdle (..),
@@ -145,13 +145,12 @@ chainSyncClient tracer networkId startingPoint observerHandler =
                 _ -> []
 
               (utxo', observations) = observeAll networkId utxo txs
-              onChainTxs = mapMaybe convertObservation observations
 
-          forM_ onChainTxs (traceWith tracer . logOnChainTx)
-          let observationsAt = ChainObservation point blockNo . Just <$> onChainTxs
+          mapM_ (traceWith tracer) $ mapMaybe logObservation observations
+          let observationsAt = ChainObservation point blockNo <$> observations
           observerHandler $
             if null observationsAt
-              then [ChainObservation point blockNo Nothing]
+              then [ChainObservation point blockNo NoHeadTx]
               else observationsAt
 
           pure $ clientStIdle utxo'

hydra-tx/src/Hydra/Tx/Observe.hs

@@ -52,6 +52,19 @@ data HeadObservation
   | Fanout FanoutObservation
   deriving stock (Eq, Show, Generic)
 
+instance ToJSON HeadObservation where
+  -- TODO: implement explorer compatible JSON instance
+  toJSON = undefined
+
+instance FromJSON HeadObservation where
+  -- TODO: implement explorer compatible JSON instance
+  parseJSON = undefined
+
+instance Arbitrary HeadObservation where
+  -- TODO: implement arbitrary instance
+  arbitrary = undefined
+  shrink = undefined
+
 -- | Observe any Hydra head transaction.
 observeHeadTx :: NetworkId -> UTxO -> Tx -> HeadObservation
 observeHeadTx networkId utxo tx =