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Handlers.hs
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Handlers.hs
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{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE UndecidableInstances #-}
-- | Provide infrastructure-independent "handlers" for posting transactions and following the chain.
--
-- This module encapsulates the transformation logic between cardano transactions and `HydraNode` abstractions
-- `PostChainTx` and `OnChainTx`, and maintainance of on-chain relevant state.
module Hydra.Chain.Direct.Handlers where
import Hydra.Prelude
import Cardano.Api.UTxO qualified as UTxO
import Cardano.Slotting.Slot (SlotNo (..))
import Control.Concurrent.Class.MonadSTM (modifyTVar, newTVarIO, writeTVar)
import Control.Monad.Class.MonadSTM (throwSTM)
import Hydra.Cardano.Api (
BlockHeader,
ChainPoint (..),
Tx,
TxId,
chainPointToSlotNo,
getChainPoint,
getTxBody,
getTxId,
)
import Hydra.Chain (
Chain (..),
ChainCallback,
ChainEvent (..),
ChainStateHistory,
OnChainTx (..),
PostChainTx (..),
PostTxError (..),
currentState,
pushNewState,
rollbackHistory,
)
import Hydra.Chain.ChainState (
ChainSlot (..),
ChainStateType,
IsChainState,
)
import Hydra.Chain.Direct.State (
ChainContext (..),
ChainStateAt (..),
abort,
chainSlotFromPoint,
close,
collect,
commit',
contest,
decrement,
fanout,
getKnownUTxO,
increment,
initialize,
recover,
)
import Hydra.Chain.Direct.TimeHandle (TimeHandle (..))
import Hydra.Chain.Direct.Tx (
AbortObservation (..),
CloseObservation (..),
CollectComObservation (..),
CommitObservation (..),
ContestObservation (..),
DecrementObservation (..),
FanoutObservation (..),
HeadObservation (..),
IncrementObservation (..),
InitObservation (..),
headSeedToTxIn,
observeHeadTx,
txInToHeadSeed,
)
import Hydra.Chain.Direct.Wallet (
ErrCoverFee (..),
TinyWallet (..),
TinyWalletLog,
)
import Hydra.Ledger.Cardano (adjustUTxO, fromChainSlot)
import Hydra.Logging (Tracer, traceWith)
import Hydra.Plutus.Extras (posixToUTCTime)
import Hydra.Tx (
CommitBlueprintTx (..),
HeadParameters (..),
UTxOType,
)
import Hydra.Tx.Contest (ClosedThreadOutput (..))
import Hydra.Tx.ContestationPeriod (toNominalDiffTime)
import Hydra.Tx.Deposit (DepositObservation (..), depositTx)
import Hydra.Tx.Recover (RecoverObservation (..))
import System.IO.Error (userError)
-- | Handle of a mutable local chain state that is kept in the direct chain layer.
data LocalChainState m tx = LocalChainState
{ getLatest :: STM m (ChainStateType tx)
, pushNew :: ChainStateType tx -> STM m ()
, rollback :: ChainSlot -> STM m (ChainStateType tx)
, history :: STM m (ChainStateHistory tx)
}
-- | Initialize a new local chain state from a given chain state history.
newLocalChainState ::
(MonadSTM m, IsChainState tx) =>
ChainStateHistory tx ->
m (LocalChainState m tx)
newLocalChainState chainState = do
tv <- newTVarIO chainState
pure
LocalChainState
{ getLatest = getLatest tv
, pushNew = pushNew tv
, rollback = rollback tv
, history = readTVar tv
}
where
getLatest tv = currentState <$> readTVar tv
pushNew tv cs =
modifyTVar tv (pushNewState cs)
rollback tv chainSlot = do
rolledBack <-
readTVar tv
<&> rollbackHistory chainSlot
writeTVar tv rolledBack
pure (currentState rolledBack)
-- * Posting Transactions
-- | A callback used to actually submit a transaction to the chain.
type SubmitTx m = Tx -> m ()
-- | A way to acquire a 'TimeHandle'
type GetTimeHandle m = m TimeHandle
-- | Create a `Chain` component for posting "real" cardano transactions.
--
-- This component does not actually interact with a cardano-node, but creates
-- cardano transactions from `PostChainTx` transactions emitted by a
-- `HydraNode`, balancing and signing them using given `TinyWallet`, before
-- handing it off to the given 'SubmitTx' callback. There is also a 'draftTx'
-- option for drafting a commit tx on behalf of the user using their selected
-- utxo.
--
-- NOTE: Given the constraints on `m` this function should work within `IOSim`
-- and does not require any actual `IO` to happen which makes it highly suitable
-- for simulations and testing.
mkChain ::
(MonadSTM m, MonadThrow (STM m)) =>
Tracer m DirectChainLog ->
-- | Means to acquire a new 'TimeHandle'.
GetTimeHandle m ->
TinyWallet m ->
ChainContext ->
LocalChainState m Tx ->
SubmitTx m ->
Chain Tx m
mkChain tracer queryTimeHandle wallet ctx LocalChainState{getLatest} submitTx =
Chain
{ postTx = \tx -> do
ChainStateAt{spendableUTxO} <- atomically getLatest
traceWith tracer $ ToPost{toPost = tx}
timeHandle <- queryTimeHandle
vtx <-
atomically (prepareTxToPost timeHandle wallet ctx spendableUTxO tx)
>>= finalizeTx wallet ctx spendableUTxO mempty
submitTx vtx
, -- Handle that creates a draft commit tx using the user utxo and a _blueprint_ transaction.
-- Possible errors are handled at the api server level.
draftCommitTx = \headId commitBlueprintTx -> do
ChainStateAt{spendableUTxO} <- atomically getLatest
let CommitBlueprintTx{lookupUTxO} = commitBlueprintTx
traverse (finalizeTx wallet ctx spendableUTxO lookupUTxO) $
commit' ctx headId spendableUTxO commitBlueprintTx
, -- Handle that creates a draft **deposit** tx using the user utxo and a deadline.
-- Possible errors are handled at the api server level.
draftDepositTx = \headId commitBlueprintTx deadline -> do
let CommitBlueprintTx{lookupUTxO} = commitBlueprintTx
ChainStateAt{spendableUTxO} <- atomically getLatest
traverse (finalizeTx wallet ctx spendableUTxO lookupUTxO) $
-- TODO: Should we move deposit tx argument verification to `depositTx` function and have Either here?
Right (depositTx (networkId ctx) headId commitBlueprintTx deadline)
, -- Submit a cardano transaction to the cardano-node using the
-- LocalTxSubmission protocol.
submitTx
}
-- | Balance and sign the given partial transaction.
finalizeTx ::
MonadThrow m =>
TinyWallet m ->
ChainContext ->
UTxO.UTxO ->
UTxO.UTxO ->
Tx ->
m Tx
finalizeTx TinyWallet{sign, coverFee} ctx utxo userUTxO partialTx = do
let headUTxO = getKnownUTxO ctx <> utxo <> userUTxO
coverFee headUTxO partialTx >>= \case
Left ErrNoFuelUTxOFound ->
throwIO (NoFuelUTXOFound :: PostTxError Tx)
Left ErrNotEnoughFunds{} ->
throwIO (NotEnoughFuel :: PostTxError Tx)
Left ErrScriptExecutionFailed{redeemerPointer, scriptFailure} ->
throwIO
( ScriptFailedInWallet
{ redeemerPtr = redeemerPointer
, failureReason = scriptFailure
} ::
PostTxError Tx
)
Left e ->
throwIO
( InternalWalletError
{ headUTxO
, reason = show e
, tx = partialTx
} ::
PostTxError Tx
)
Right balancedTx ->
pure $ sign balancedTx
-- * Following the Chain
-- | A /handler/ that takes care of following the chain.
data ChainSyncHandler m = ChainSyncHandler
{ onRollForward :: BlockHeader -> [Tx] -> m ()
, onRollBackward :: ChainPoint -> m ()
}
-- | Conversion of a slot number to a time failed. This can be usually be
-- considered an internal error and may be happening because the used era
-- history is too old.
data TimeConversionException = TimeConversionException
{ slotNo :: SlotNo
, reason :: Text
}
deriving stock (Eq, Show)
deriving anyclass (Exception)
-- | Creates a `ChainSyncHandler` that can notify the given `callback` of events happening
-- on-chain.
--
-- This forms the other half of a `ChainComponent` along with `mkChain` but is decoupled from
-- actual interactions with the chain.
--
-- A `TimeHandle` is needed to do `SlotNo -> POSIXTime` conversions for 'Tick' events.
--
-- Throws 'TimeConversionException' when a received block's 'SlotNo' cannot be
-- converted to a 'UTCTime' with the given 'TimeHandle'.
chainSyncHandler ::
forall m.
(MonadSTM m, MonadThrow m) =>
-- | Tracer for logging
Tracer m DirectChainLog ->
ChainCallback Tx m ->
-- | Means to acquire a new 'TimeHandle'.
GetTimeHandle m ->
-- | Contextual information about our chain connection.
ChainContext ->
LocalChainState m Tx ->
-- | A chain-sync handler to use in a local-chain-sync client.
ChainSyncHandler m
chainSyncHandler tracer callback getTimeHandle ctx localChainState =
ChainSyncHandler
{ onRollBackward
, onRollForward
}
where
ChainContext{networkId} = ctx
LocalChainState{rollback, getLatest, pushNew} = localChainState
onRollBackward :: ChainPoint -> m ()
onRollBackward point = do
traceWith tracer $ RolledBackward{point}
rolledBackChainState <- atomically $ rollback (chainSlotFromPoint point)
callback Rollback{rolledBackChainState}
onRollForward :: BlockHeader -> [Tx] -> m ()
onRollForward header receivedTxs = do
let point = getChainPoint header
traceWith tracer $
RolledForward
{ point
, receivedTxIds = getTxId . getTxBody <$> receivedTxs
}
case chainPointToSlotNo point of
Nothing -> pure ()
Just slotNo -> do
timeHandle <- getTimeHandle
case slotToUTCTime timeHandle slotNo of
Left reason ->
throwIO TimeConversionException{slotNo, reason}
Right utcTime -> do
let chainSlot = ChainSlot . fromIntegral $ unSlotNo slotNo
callback (Tick{chainTime = utcTime, chainSlot})
forM_ receivedTxs $
maybeObserveSomeTx point >=> \case
Nothing -> pure ()
Just event -> callback event
maybeObserveSomeTx point tx = atomically $ do
ChainStateAt{spendableUTxO} <- getLatest
let observation = observeHeadTx networkId spendableUTxO tx
case convertObservation observation of
Nothing -> pure Nothing
Just observedTx -> do
let newChainState =
ChainStateAt
{ spendableUTxO = adjustUTxO tx spendableUTxO
, recordedAt = Just point
}
pushNew newChainState
pure $ Just Observation{observedTx, newChainState}
convertObservation :: HeadObservation -> Maybe (OnChainTx Tx)
convertObservation = \case
NoHeadTx -> Nothing
Init InitObservation{headId, contestationPeriod, parties, seedTxIn, participants} ->
pure
OnInitTx
{ headId
, headSeed = txInToHeadSeed seedTxIn
, headParameters = HeadParameters{contestationPeriod, parties}
, participants
}
Abort AbortObservation{headId} ->
pure OnAbortTx{headId}
Commit CommitObservation{headId, party, committed} ->
pure OnCommitTx{headId, party, committed}
CollectCom CollectComObservation{headId} ->
pure OnCollectComTx{headId}
Deposit DepositObservation{headId, deposited, depositTxId, deadline} ->
pure $ OnDepositTx{headId, deposited, depositTxId, deadline = posixToUTCTime deadline}
Recover RecoverObservation{headId, recoveredTxId} ->
pure OnRecoverTx{headId, recoveredTxId}
Increment IncrementObservation{headId, newVersion, depositTxId} ->
pure OnIncrementTx{headId, newVersion, depositTxId}
Decrement DecrementObservation{headId, newVersion, distributedOutputs} ->
pure OnDecrementTx{headId, newVersion, distributedOutputs}
Close CloseObservation{headId, snapshotNumber, threadOutput = ClosedThreadOutput{closedContestationDeadline}} ->
pure
OnCloseTx
{ headId
, snapshotNumber
, contestationDeadline = posixToUTCTime closedContestationDeadline
}
Contest ContestObservation{contestationDeadline, headId, snapshotNumber} ->
pure OnContestTx{contestationDeadline, headId, snapshotNumber}
Fanout FanoutObservation{headId} ->
pure OnFanoutTx{headId}
prepareTxToPost ::
(MonadSTM m, MonadThrow (STM m)) =>
TimeHandle ->
TinyWallet m ->
ChainContext ->
-- | Spendable UTxO
UTxOType Tx ->
PostChainTx Tx ->
STM m Tx
prepareTxToPost timeHandle wallet ctx spendableUTxO tx =
case tx of
InitTx{participants, headParameters} ->
getSeedInput wallet >>= \case
Just seedInput ->
pure $ initialize ctx seedInput participants headParameters
Nothing ->
throwIO (NoSeedInput @Tx)
AbortTx{utxo, headSeed} ->
case headSeedToTxIn headSeed of
Nothing ->
throwIO (InvalidSeed{headSeed} :: PostTxError Tx)
Just seedTxIn ->
case abort ctx seedTxIn spendableUTxO utxo of
Left _ -> throwIO (FailedToConstructAbortTx @Tx)
Right abortTx -> pure abortTx
-- TODO: We do not rely on the utxo from the collect com tx here because the
-- chain head-state is already tracking UTXO entries locked by commit scripts,
-- and thus, can re-construct the committed UTXO for the collectComTx from
-- the commits' datums.
--
-- Perhaps we do want however to perform some kind of sanity check to ensure
-- that both states are consistent.
CollectComTx{utxo, headId, headParameters} ->
case collect ctx headId headParameters utxo spendableUTxO of
Left _ -> throwIO (FailedToConstructCollectTx @Tx)
Right collectTx -> pure collectTx
IncrementTx{headId, headParameters, incrementingSnapshot, depositTxId} ->
case increment ctx spendableUTxO headId headParameters incrementingSnapshot depositTxId of
Left _ -> throwIO (FailedToConstructIncrementTx @Tx)
Right incrementTx' -> pure incrementTx'
RecoverTx{headId, recoverTxId, deadline} -> do
case recover ctx headId recoverTxId spendableUTxO (fromChainSlot deadline) of
Left _ -> throwIO (FailedToConstructRecoverTx @Tx)
Right recoverTx' -> pure recoverTx'
DecrementTx{headId, headParameters, decrementingSnapshot} ->
case decrement ctx spendableUTxO headId headParameters decrementingSnapshot of
Left _ -> throwIO (FailedToConstructDecrementTx @Tx)
Right decrementTx' -> pure decrementTx'
CloseTx{headId, headParameters, openVersion, closingSnapshot} -> do
(currentSlot, currentTime) <- throwLeft currentPointInTime
let HeadParameters{contestationPeriod} = headParameters
upperBound <- calculateTxUpperBoundFromContestationPeriod currentTime contestationPeriod
case close ctx spendableUTxO headId headParameters openVersion closingSnapshot currentSlot upperBound of
Left _ -> throwIO (FailedToConstructCloseTx @Tx)
Right closeTx -> pure closeTx
ContestTx{headId, headParameters, openVersion, contestingSnapshot} -> do
(_, currentTime) <- throwLeft currentPointInTime
let HeadParameters{contestationPeriod} = headParameters
upperBound <- calculateTxUpperBoundFromContestationPeriod currentTime contestationPeriod
case contest ctx spendableUTxO headId contestationPeriod openVersion contestingSnapshot upperBound of
Left _ -> throwIO (FailedToConstructContestTx @Tx)
Right contestTx -> pure contestTx
FanoutTx{utxo, utxoToDecommit, headSeed, contestationDeadline} -> do
deadlineSlot <- throwLeft $ slotFromUTCTime contestationDeadline
case headSeedToTxIn headSeed of
Nothing ->
throwIO (InvalidSeed{headSeed} :: PostTxError Tx)
Just seedTxIn ->
case fanout ctx spendableUTxO seedTxIn utxo utxoToDecommit deadlineSlot of
Left _ -> throwIO (FailedToConstructFanoutTx @Tx)
Right fanoutTx -> pure fanoutTx
where
-- XXX: Might want a dedicated exception type here
throwLeft = either (throwSTM . userError . toString) pure
TimeHandle{currentPointInTime, slotFromUTCTime} = timeHandle
-- See ADR21 for context
calculateTxUpperBoundFromContestationPeriod currentTime contestationPeriod = do
let effectiveDelay = min (toNominalDiffTime contestationPeriod) maxGraceTime
let upperBoundTime = addUTCTime effectiveDelay currentTime
upperBoundSlot <- throwLeft $ slotFromUTCTime upperBoundTime
pure (upperBoundSlot, upperBoundTime)
-- | Maximum delay we put on the upper bound of transactions to fit into a block.
-- NOTE: This is highly depending on the network. If the security parameter and
-- epoch length result in a short horizon, this is problematic.
maxGraceTime :: NominalDiffTime
maxGraceTime = 200
--
-- Tracing
--
data DirectChainLog
= ToPost {toPost :: PostChainTx Tx}
| PostingTx {txId :: TxId}
| PostedTx {txId :: TxId}
| PostingFailed {tx :: Tx, postTxError :: PostTxError Tx}
| RolledForward {point :: ChainPoint, receivedTxIds :: [TxId]}
| RolledBackward {point :: ChainPoint}
| Wallet TinyWalletLog
deriving stock (Eq, Show, Generic)
deriving anyclass (ToJSON, FromJSON)
instance Arbitrary DirectChainLog where
arbitrary = genericArbitrary
shrink = genericShrink