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OnChain.hs
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OnChain.hs
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{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeApplications #-}
{-# OPTIONS_GHC -fno-specialize #-}
module Hydra.Contract.OnChain where
import Ledger
import PlutusTx.Prelude
import Data.Aeson (FromJSON, ToJSON)
import Ledger.Ada (lovelaceValueOf)
import Ledger.Constraints (checkScriptContext)
import Ledger.Constraints.TxConstraints (
mustBeSignedBy,
mustForgeCurrency,
mustPayToOtherScript,
mustPayToTheScript,
mustProduceAtLeast,
mustSpendAtLeast,
mustSpendPubKeyOutput,
mustSpendScriptOutput,
)
import Ledger.Credential (Credential (..))
import Ledger.Typed.Scripts (ValidatorTypes (..))
import qualified Ledger.Typed.Scripts as Scripts
import Ledger.Value (TokenName (..))
import qualified Ledger.Value as Value
import PlutusPrelude (Generic, (>=>))
import qualified PlutusTx
import PlutusTx.AssocMap (Map)
import qualified PlutusTx.AssocMap as Map
import PlutusTx.IsData.Class (IsData (..))
import Text.Show (Show)
--
-- Head Parameters
--
data HeadParameters = HeadParameters
{ participants :: [PubKeyHash]
, policyId :: MonetaryPolicyHash
}
PlutusTx.makeLift ''HeadParameters
data Snapshot = Snapshot
{ snapshotNumber :: Integer
, utxo :: [TxOut]
}
deriving stock (Generic, Show)
deriving anyclass (FromJSON, ToJSON)
PlutusTx.makeLift ''Snapshot
PlutusTx.unstableMakeIsData ''Snapshot
--
-- Hydra State-Machine
--
data State
= Initial
| Open [TxOut]
| Closed Snapshot
| Final
deriving stock (Generic, Show)
deriving anyclass (FromJSON, ToJSON)
PlutusTx.makeLift ''State
PlutusTx.unstableMakeIsData ''State
data Transition
= CollectCom
| Close Snapshot
| Abort
deriving (Generic)
PlutusTx.makeLift ''Transition
PlutusTx.unstableMakeIsData ''Transition
data Hydra
instance Scripts.ValidatorTypes Hydra where
type DatumType Hydra = State
type RedeemerType Hydra = Transition
hydraValidator ::
HeadParameters ->
State ->
Transition ->
ScriptContext ->
Bool
hydraValidator HeadParameters{participants, policyId} s i ctx =
case (s, i) of
(Initial, CollectCom) ->
let collectComUtxos =
snd <$> filterInputs (hasParty policyId) ctx
committedOutputs =
mapMaybe decodeCommit collectComUtxos
newState =
Open committedOutputs
amountPaid =
foldMap txOutValue collectComUtxos
in and
[ mustBeSignedByOneOf participants ctx
, all (mustForwardParty ctx policyId) participants
, checkScriptContext @(RedeemerType Hydra) @(DatumType Hydra)
(mustPayToTheScript newState amountPaid)
ctx
]
(Open _, Close snapshot) ->
let newState =
Closed snapshot
amountPaid =
foldMap txOutValue (snd <$> filterInputs (hasParty policyId) ctx)
in -- snapshotValue =
-- foldMap txOutValue (utxo snapshot)
mustBeSignedByOneOf participants ctx
-- , -- TODO / QUESTION: When closing, shouldn't we ensure that the total
-- -- value captured by the snapshot is smaller or equal to the value
-- -- available at the contract. Checking the signatures isn't enough
-- -- as the head participants could be making a mistake?
-- -- FIXME: snapshotValue does not contain participation tokens!
-- && snapshotValue == snapshotValue
&& checkScriptContext @(RedeemerType Hydra) @(DatumType Hydra)
(mustPayToTheScript newState amountPaid)
ctx
(Initial, Abort) ->
let newState =
Final
amountPaid =
lovelaceValueOf 0
in and
[ mustBeSignedByOneOf participants ctx
, all (mustBurnParty ctx policyId) participants
, checkScriptContext @(RedeemerType Hydra) @(DatumType Hydra)
(mustPayToTheScript newState amountPaid)
ctx
]
_ ->
False
where
decodeCommit =
txOutDatumHash
>=> (`findDatum` scriptContextTxInfo ctx)
>=> (fromData @(DatumType Commit) . getDatum)
{- ORMOLU_DISABLE -}
hydraTypedValidator
:: HeadParameters
-> Scripts.TypedValidator Hydra
hydraTypedValidator params = Scripts.mkTypedValidator @Hydra
( $$(PlutusTx.compile [|| hydraValidator ||])
`PlutusTx.applyCode` PlutusTx.liftCode params
)
$$(PlutusTx.compile [|| wrap ||])
where
wrap = Scripts.wrapValidator @(DatumType Hydra) @(RedeemerType Hydra)
{- ORMOLU_ENABLE -}
hydraValidatorHash :: HeadParameters -> ValidatorHash
hydraValidatorHash = Scripts.validatorHash . hydraTypedValidator
{-# INLINEABLE hydraValidatorHash #-}
--
-- Initial Validator
--
data Initial
instance Scripts.ValidatorTypes Initial where
type DatumType Initial = PubKeyHash
type RedeemerType Initial = TxOutRef
-- | The Validator 'initial' ensures that the input is consumed by a commit or
-- an abort transaction.
initialValidator ::
HeadParameters ->
ValidatorHash ->
ValidatorHash ->
PubKeyHash ->
TxOutRef ->
ScriptContext ->
Bool
initialValidator HeadParameters{policyId} hydraScript commitScript vk ref ctx =
consumedByCommit || consumedByAbort
where
-- A commit transaction, identified by:
-- (a) A signature that verifies as valid with verification key defined as datum
-- (b) Spending a UTxO also referenced as redeemer.
-- (c) Having the commit validator in its only output, with a valid
-- participation token for the associated key, and the total value of the
-- committed UTxO.
consumedByCommit =
case findUtxo ref ctx of
Nothing ->
False
Just utxo ->
let commitDatum = asDatum @(DatumType Commit) (snd utxo)
commitValue = txOutValue (snd utxo) <> mkParty policyId vk
in checkScriptContext @(RedeemerType Initial) @(DatumType Initial)
( mconcat
[ mustBeSignedBy vk
, mustSpendPubKeyOutput (fst utxo)
, mustPayToOtherScript commitScript commitDatum commitValue
]
)
ctx
consumedByAbort =
mustRunContract hydraScript Abort ctx
{- ORMOLU_DISABLE -}
initialTypedValidator
:: HeadParameters
-> Scripts.TypedValidator Initial
initialTypedValidator policyId = Scripts.mkTypedValidator @Initial
($$(PlutusTx.compile [|| initialValidator ||])
`PlutusTx.applyCode` PlutusTx.liftCode policyId
`PlutusTx.applyCode` PlutusTx.liftCode (hydraValidatorHash policyId)
`PlutusTx.applyCode` PlutusTx.liftCode (commitValidatorHash policyId)
)
$$(PlutusTx.compile [|| wrap ||])
where
wrap = Scripts.wrapValidator @(DatumType Initial) @(RedeemerType Initial)
{- ORMOLU_ENABLE -}
--
-- Commit Validator
--
data Commit
instance Scripts.ValidatorTypes Commit where
type DatumType Commit = TxOut
type RedeemerType Commit = ()
-- | To lock outputs for a Hydra head, the ith head member will attach a commit
-- transaction to the i-th output of the initial transaction.
-- Validator 'commit' ensures that the commit transaction correctly records the
-- partial UTxO set Ui committed by the party.
--
-- The data field of the output of the commit transaction is
--
-- Ui = makeUTxO(o_1 , . . . , o_m),
--
-- where the o_j are the outputs referenced by the commit transaction’s inputs
-- and makeUTxO stores pairs (out-ref_j , o_j) of outputs o_j with the
-- corresponding output reference out-ref_j .
commitValidator ::
ValidatorHash ->
TxOut ->
() ->
ScriptContext ->
Bool
commitValidator hydraScript committedOut () ctx =
consumedByCollectCom || consumedByAbort
where
consumedByCollectCom =
mustRunContract hydraScript CollectCom ctx
consumedByAbort =
and
[ mustRunContract hydraScript Abort ctx
, mustReimburse committedOut ctx
]
{- ORMOLU_DISABLE -}
commitTypedValidator
:: HeadParameters
-> Scripts.TypedValidator Commit
commitTypedValidator params = Scripts.mkTypedValidator @Commit
($$(PlutusTx.compile [|| commitValidator ||])
`PlutusTx.applyCode` PlutusTx.liftCode (hydraValidatorHash params)
)
$$(PlutusTx.compile [|| wrap ||])
where
wrap = Scripts.wrapValidator @(DatumType Commit) @(RedeemerType Commit)
{- ORMOLU_ENABLE -}
commitValidatorHash :: HeadParameters -> ValidatorHash
commitValidatorHash = Scripts.validatorHash . commitTypedValidator
{-# INLINEABLE commitValidatorHash #-}
--
-- Monetary Policy
--
-- For the sake of simplicity in testing and whatnot, we currently 'fake' the
-- currencyId with an Integer chosen by a fair dice roll. In practice, we really
-- want this to a 'TxOutRef' so we can get actual guarantees from the ledger
-- about this being unique.
type FakeTxOutRef = Integer
-- The validator is parameterized by the public keys of the participants, as well
-- as a reference to a particular UTxO. A minting transaction will be considered
-- valid if it is able to spend that UTxO (automatically ensuring that minting
-- can only happen *once*).
--
-- What it not necessarily transparent here is that, the on-chain code is really
-- made of the curried function 'ScriptContext -> Bool', after the first parameter
-- has been partially applied. This is similar to what is called 'closures' in
-- some languages. Fundamentally, the parameter 'FakeTxOutRef' is embedded within the
-- policy and is part of the on-chain code itself!
validateMonetaryPolicy ::
FakeTxOutRef ->
ScriptContext ->
Bool
validateMonetaryPolicy _outRef _ctx =
validateMinting || validateBurning
where
-- FIXME
validateBurning =
True
-- TODO: In practice, we would do:
--
-- let constraints = mustSpendPubKeyOutput outRef
-- in checkScriptContext @() @() constraints ctx
validateMinting =
True
hydraMonetaryPolicy ::
FakeTxOutRef ->
MonetaryPolicy
hydraMonetaryPolicy outRef =
mkMonetaryPolicyScript $
$$(PlutusTx.compile [||Scripts.wrapMonetaryPolicy . validateMonetaryPolicy||])
`PlutusTx.applyCode` PlutusTx.liftCode outRef
--
-- Helpers
--
-- | This function can be rather unsafe and should *always* be used with a type
-- annotation to avoid silly mistakes and hours of debugging.
--
-- So prefer:
--
-- >>> asDatum @(DatumType MyContract) val
--
-- over
--
-- >>> asDatum val
--
-- A 'Datum' is an opaque type, and type information is lost when turning into a
-- a 'Data'. Hence, various functions of the Plutus Tx framework that rely on
-- 'Datum' or 'Redeemer' are basically stringly-typed function with no guarantee
-- whatsoever that the 'IsData a' being passed will correspond to what's
-- expected by the underlying script. So, save you some hours of debugging and
-- always explicitly specify the source type when using this function,
-- preferably using the data-family from the 'ValidatorTypes' instance.
asDatum :: IsData a => a -> Datum
asDatum = Datum . toData
{-# INLINEABLE asDatum #-}
-- | Always use with explicit type-annotation, See warnings on 'asDatum'.
asRedeemer :: IsData a => a -> Redeemer
asRedeemer = Redeemer . toData
{-# INLINEABLE asRedeemer #-}
mustBeSignedByOneOf ::
[PubKeyHash] ->
ScriptContext ->
Bool
mustBeSignedByOneOf vks ctx =
or ((`checkScriptContext` ctx) . mustBeSignedBy @() @() <$> vks)
{-# INLINEABLE mustBeSignedByOneOf #-}
mustReimburse ::
TxOut ->
ScriptContext ->
Bool
mustReimburse txOut =
elem txOut . txInfoOutputs . scriptContextTxInfo
{-# INLINEABLE mustReimburse #-}
mustRunContract ::
forall redeemer.
(IsData redeemer) =>
ValidatorHash ->
redeemer ->
ScriptContext ->
Bool
mustRunContract script redeemer ctx =
case findContractInput script ctx of
Nothing ->
False
Just contractRef ->
checkScriptContext @() @()
( mconcat
[ mustSpendScriptOutput contractRef (asRedeemer redeemer)
]
)
ctx
{-# INLINEABLE mustRunContract #-}
mustForwardParty ::
ScriptContext ->
MonetaryPolicyHash ->
PubKeyHash ->
Bool
mustForwardParty ctx policyId vk =
let participationToken = mkParty policyId vk
in checkScriptContext @() @()
( mconcat
[ mustSpendAtLeast participationToken
, mustProduceAtLeast participationToken
]
)
ctx
{-# INLINEABLE mustForwardParty #-}
mustBurnParty ::
ScriptContext ->
MonetaryPolicyHash ->
PubKeyHash ->
Bool
mustBurnParty ctx policyId vk =
let assetName = mkPartyName vk
in checkScriptContext @() @() (mustForgeCurrency policyId assetName (-1)) ctx
{-# INLINEABLE mustBurnParty #-}
mkParty ::
MonetaryPolicyHash ->
PubKeyHash ->
Value
mkParty policyId vk =
Value.singleton (Value.mpsSymbol policyId) (mkPartyName vk) 1
{-# INLINEABLE mkParty #-}
mkPartyName ::
PubKeyHash ->
TokenName
mkPartyName =
TokenName . getPubKeyHash
{-# INLINEABLE mkPartyName #-}
hasParty :: MonetaryPolicyHash -> TxInInfo -> Bool
hasParty policyId input =
let currency = Value.mpsSymbol policyId
in currency `elem` symbols (txOutValue $ txInInfoResolved input)
{-# INLINEABLE hasParty #-}
filterInputs :: (TxInInfo -> Bool) -> ScriptContext -> [(TxOutRef, TxOut)]
filterInputs predicate =
mapMaybe fn . txInfoInputs . scriptContextTxInfo
where
fn info
| predicate info = Just (txInInfoOutRef info, txInInfoResolved info)
| otherwise = Nothing
{-# INLINEABLE filterInputs #-}
findUtxo :: TxOutRef -> ScriptContext -> Maybe (TxOutRef, TxOut)
findUtxo ref ctx =
case filterInputs (\input -> ref == txInInfoOutRef input) ctx of
[utxo] -> Just utxo
_ -> Nothing
{-# INLINEABLE findUtxo #-}
findContractInput :: ValidatorHash -> ScriptContext -> Maybe TxOutRef
findContractInput script ctx =
case filterInputs (matchScript . txInInfoResolved) ctx of
[utxo] -> Just (fst utxo)
_ -> Nothing
where
matchScript :: TxOut -> Bool
matchScript txOut =
case txOutAddress txOut of
Address (ScriptCredential script') _ -> script == script'
_ -> False
{-# INLINEABLE findContractInput #-}
-- NOTE: Not using `Value.symbols` because it is broken. In fact, a 'Value' may
-- carry null quantities of some particular tokens, leading to weird situation
-- where both:
--
-- - value == lovelaceValueOf n
-- - symbols value /= [adaSymbol]
--
-- are true at the same time. The equality makes no difference between the
-- absence of a certain symbol/token, and a null quantity of that symbol. Such
-- null quantities are probably constructed when moving values around but they
-- don't really mean anything so they should be discarded from views of the
-- value itself, like 'symbols'
symbols :: Value -> [CurrencySymbol]
symbols = foldr normalize [] . Map.toList . Value.getValue
where
normalize :: (CurrencySymbol, Map TokenName Integer) -> [CurrencySymbol] -> [CurrencySymbol]
normalize (currency, tokens) acc
| currency `elem` acc = acc
| otherwise =
let elems = snd <$> Map.toList tokens
in if sum elems == 0 then acc else currency : acc
{-# INLINEABLE symbols #-}