refund_relayer_extension.rs

// Copyright 2021 Parity Technologies (UK) Ltd.
// This file is part of Parity Bridges Common.

// Parity Bridges Common is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity Bridges Common is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.

//! Signed extension that refunds relayer if he has delivered some new messages.
//! It also refunds transaction cost if the transaction is an `utility.batchAll()`
//! with calls that are: delivering new messsage and all necessary underlying headers
//! (parachain or relay chain).

// hack because we have circular (test-level) dependency between `millau-runtime`
// and `bridge-runtime-common` crates
#[cfg(not(test))]
use crate::messages::target::FromBridgedChainMessagesProof;
#[cfg(test)]
use millau_runtime::bridge_runtime_common::messages::target::FromBridgedChainMessagesProof;

use bp_messages::{target_chain::SourceHeaderChain, LaneId, MessageNonce};
use bp_polkadot_core::parachains::ParaId;
use bp_runtime::{Chain, HashOf};
use codec::{Decode, Encode};
use frame_support::{
	dispatch::{CallableCallFor, DispatchInfo, Dispatchable, PostDispatchInfo},
	traits::IsSubType,
	CloneNoBound, DefaultNoBound, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound,
};
use pallet_bridge_grandpa::{
	BridgedChain, Call as GrandpaCall, Config as GrandpaConfig, Pallet as GrandpaPallet,
};
use pallet_bridge_messages::{
	Call as MessagesCall, Config as MessagesConfig, Pallet as MessagesPallet,
};
use pallet_bridge_parachains::{
	Call as ParachainsCall, Config as ParachainsConfig, Pallet as ParachainsPallet, RelayBlockHash,
	RelayBlockHasher, RelayBlockNumber,
};
use pallet_bridge_relayers::{Config as RelayersConfig, Pallet as RelayersPallet};
use pallet_transaction_payment::{Config as TransactionPaymentConfig, OnChargeTransaction};
use pallet_utility::{Call as UtilityCall, Config as UtilityConfig, Pallet as UtilityPallet};
use scale_info::TypeInfo;
use sp_runtime::{
	traits::{DispatchInfoOf, Get, Header as HeaderT, PostDispatchInfoOf, SignedExtension, Zero},
	transaction_validity::{TransactionValidity, TransactionValidityError, ValidTransaction},
	DispatchResult, FixedPointOperand,
};
use sp_std::marker::PhantomData;

// TODO (https://github.com/paritytech/parity-bridges-common/issues/1667):
// support multiple bridges in this extension

/// Transaction fee calculation.
pub trait TransactionFeeCalculation<Balance> {
	/// Compute fee that is paid for given transaction. The fee is later refunded to relayer.
	fn compute_fee(
		info: &DispatchInfo,
		post_info: &PostDispatchInfo,
		len: usize,
		tip: Balance,
	) -> Balance;
}

impl<R> TransactionFeeCalculation<BalanceOf<R>> for R
where
	R: TransactionPaymentConfig,
	<R as frame_system::Config>::RuntimeCall:
		Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo>,
	BalanceOf<R>: FixedPointOperand,
{
	fn compute_fee(
		info: &DispatchInfo,
		post_info: &PostDispatchInfo,
		len: usize,
		tip: BalanceOf<R>,
	) -> BalanceOf<R> {
		pallet_transaction_payment::Pallet::<R>::compute_actual_fee(len as _, info, post_info, tip)
	}
}
/// Signed extension that refunds relayer for new messages coming from the parachain.
///
/// Also refunds relayer for successful finality delivery if it comes in batch (`utility.batchAll`)
/// with message delivery transaction. Batch may deliver either both relay chain header and
/// parachain head, or just parachain head. Corresponding headers must be used in messages
/// proof verification.
///
/// Extension does not refund transaction tip due to security reasons.
#[derive(
	CloneNoBound,
	Decode,
	DefaultNoBound,
	Encode,
	EqNoBound,
	PartialEqNoBound,
	RuntimeDebugNoBound,
	TypeInfo,
)]
#[scale_info(skip_type_params(RT, GI, PI, MI, BE, PID, LID, FEE))]
#[allow(clippy::type_complexity)] // TODO: get rid of that in https://github.com/paritytech/parity-bridges-common/issues/1666
pub struct RefundRelayerForMessagesFromParachain<RT, GI, PI, MI, BE, PID, LID, FEE>(
	PhantomData<(RT, GI, PI, MI, BE, PID, LID, FEE)>,
);

/// Data that is crafted in `pre_dispatch` method and used at `post_dispatch`.
#[derive(PartialEq)]
#[cfg_attr(test, derive(Debug))]
pub struct PreDispatchData<AccountId> {
	/// Transaction submitter (relayer) account.
	pub relayer: AccountId,
	/// Type of the call.
	pub call_type: CallType,
}

/// Type of the call that the extension recognizes.
#[derive(Clone, Copy, PartialEq, RuntimeDebugNoBound)]
pub enum CallType {
	/// Relay chain finality + parachain finality + message delivery calls.
	AllFinalityAndDelivery(ExpectedRelayChainState, ExpectedParachainState, MessagesState),
	/// Parachain finality + message delivery calls.
	ParachainFinalityAndDelivery(ExpectedParachainState, MessagesState),
	/// Standalone message delivery call.
	Delivery(MessagesState),
}

impl CallType {
	/// Returns the pre-dispatch messages pallet state.
	fn pre_dispatch_messages_state(&self) -> MessagesState {
		match *self {
			Self::AllFinalityAndDelivery(_, _, messages_state) => messages_state,
			Self::ParachainFinalityAndDelivery(_, messages_state) => messages_state,
			Self::Delivery(messages_state) => messages_state,
		}
	}
}

/// Expected post-dispatch state of the relay chain pallet.
#[derive(Clone, Copy, PartialEq, RuntimeDebugNoBound)]
pub struct ExpectedRelayChainState {
	/// Best known relay chain block number.
	pub best_block_number: RelayBlockNumber,
}

/// Expected post-dispatch state of the parachain pallet.
#[derive(Clone, Copy, PartialEq, RuntimeDebugNoBound)]
pub struct ExpectedParachainState {
	/// At which relay block the parachain head has been updated?
	pub at_relay_block_number: RelayBlockNumber,
}

/// Pre-dispatch state of messages pallet.
///
/// This struct is for pre-dispatch state of the pallet, not the expected post-dispatch state.
/// That's because message delivery transaction may deliver some of messages that it brings.
/// If this happens, we consider it "helpful" and refund its cost. If transaction fails to
/// deliver at least one message, it is considered wrong and is not refunded.
#[derive(Clone, Copy, PartialEq, RuntimeDebugNoBound)]
pub struct MessagesState {
	/// Best delivered message nonce.
	pub best_nonce: MessageNonce,
}

// without this typedef rustfmt fails with internal err
type BalanceOf<R> =
	<<R as TransactionPaymentConfig>::OnChargeTransaction as OnChargeTransaction<R>>::Balance;
type CallOf<R> = <R as frame_system::Config>::RuntimeCall;

impl<R, GI, PI, MI, BE, PID, LID, FEE> SignedExtension
	for RefundRelayerForMessagesFromParachain<R, GI, PI, MI, BE, PID, LID, FEE>
where
	R: 'static
		+ Send
		+ Sync
		+ frame_system::Config
		+ UtilityConfig<RuntimeCall = CallOf<R>>
		+ GrandpaConfig<GI>
		+ ParachainsConfig<PI, BridgesGrandpaPalletInstance = GI>
		+ MessagesConfig<MI>
		+ RelayersConfig,
	GI: 'static + Send + Sync,
	PI: 'static + Send + Sync,
	MI: 'static + Send + Sync,
	BE: 'static
		+ Send
		+ Sync
		+ Default
		+ SignedExtension<AccountId = R::AccountId, Call = CallOf<R>>,
	PID: 'static + Send + Sync + Get<u32>,
	LID: 'static + Send + Sync + Get<LaneId>,
	FEE: 'static + Send + Sync + TransactionFeeCalculation<<R as RelayersConfig>::Reward>,
	<R as frame_system::Config>::RuntimeCall:
		Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo>,
	CallOf<R>: IsSubType<CallableCallFor<UtilityPallet<R>, R>>
		+ IsSubType<CallableCallFor<GrandpaPallet<R, GI>, R>>
		+ IsSubType<CallableCallFor<ParachainsPallet<R, PI>, R>>
		+ IsSubType<CallableCallFor<MessagesPallet<R, MI>, R>>,
	<R as GrandpaConfig<GI>>::BridgedChain:
		Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>,
	<R as MessagesConfig<MI>>::SourceHeaderChain: SourceHeaderChain<
		MessagesProof = FromBridgedChainMessagesProof<HashOf<BridgedChain<R, GI>>>,
	>,
{
	const IDENTIFIER: &'static str = "RefundRelayerForMessagesFromParachain";
	type AccountId = R::AccountId;
	type Call = CallOf<R>;
	type AdditionalSigned = ();
	type Pre = Option<PreDispatchData<R::AccountId>>;

	fn additional_signed(&self) -> Result<(), TransactionValidityError> {
		Ok(())
	}

	fn validate(
		&self,
		who: &Self::AccountId,
		call: &Self::Call,
		info: &DispatchInfoOf<Self::Call>,
		len: usize,
	) -> TransactionValidity {
		// reject batch transactions with obsolete headers
		if let Some(UtilityCall::<R>::batch_all { ref calls }) = call.is_sub_type() {
			for nested_call in calls {
				let reject_obsolete_transactions = BE::default();
				reject_obsolete_transactions.pre_dispatch(who, nested_call, info, len)?;
			}
		}

		Ok(ValidTransaction::default())
	}

	fn pre_dispatch(
		self,
		who: &Self::AccountId,
		call: &Self::Call,
		info: &DispatchInfoOf<Self::Call>,
		len: usize,
	) -> Result<Self::Pre, TransactionValidityError> {
		// reject batch transactions with obsolete headers
		self.validate(who, call, info, len).map(drop)?;

		// now try to check if tx matches one of types we support
		let parse_call_type = || {
			if let Some(UtilityCall::<R>::batch_all { ref calls }) = call.is_sub_type() {
				if calls.len() == 3 {
					return Some(CallType::AllFinalityAndDelivery(
						extract_expected_relay_chain_state::<R, GI>(&calls[0])?,
						extract_expected_parachain_state::<R, GI, PI, PID>(&calls[1])?,
						extract_messages_state::<R, GI, MI, LID>(&calls[2])?,
					))
				}
				if calls.len() == 2 {
					return Some(CallType::ParachainFinalityAndDelivery(
						extract_expected_parachain_state::<R, GI, PI, PID>(&calls[0])?,
						extract_messages_state::<R, GI, MI, LID>(&calls[1])?,
					))
				}
				return None
			}

			Some(CallType::Delivery(extract_messages_state::<R, GI, MI, LID>(call)?))
		};

		Ok(parse_call_type().map(|call_type| PreDispatchData { relayer: who.clone(), call_type }))
	}

	fn post_dispatch(
		pre: Option<Self::Pre>,
		info: &DispatchInfoOf<Self::Call>,
		post_info: &PostDispatchInfoOf<Self::Call>,
		len: usize,
		result: &DispatchResult,
	) -> Result<(), TransactionValidityError> {
		// we never refund anything if it is not bridge transaction or if it is a bridge
		// transaction that we do not support here
		let (relayer, call_type) = match pre {
			Some(Some(pre)) => (pre.relayer, pre.call_type),
			_ => return Ok(()),
		};

		// we never refund anything if transaction has failed
		if result.is_err() {
			return Ok(())
		}

		// check if relay chain state has been updated
		if let CallType::AllFinalityAndDelivery(expected_relay_chain_state, _, _) = call_type {
			let actual_relay_chain_state = relay_chain_state::<R, GI>();
			if actual_relay_chain_state != Some(expected_relay_chain_state) {
				// we only refund relayer if all calls have updated chain state
				return Ok(())
			}

			// there's a conflict between how bridge GRANDPA pallet works and the
			// `AllFinalityAndDelivery` transaction. If relay chain header is mandatory, the GRANDPA
			// pallet returns `Pays::No`, because such transaction is mandatory for operating the
			// bridge. But `utility.batchAll` transaction always requires payment. But in both cases
			// we'll refund relayer - either explicitly here, or using `Pays::No` if he's choosing
			// to submit dedicated transaction.
		}

		// check if parachain state has been updated
		match call_type {
			CallType::AllFinalityAndDelivery(_, expected_parachain_state, _) |
			CallType::ParachainFinalityAndDelivery(expected_parachain_state, _) => {
				let actual_parachain_state = parachain_state::<R, PI, PID>();
				if actual_parachain_state != Some(expected_parachain_state) {
					// we only refund relayer if all calls have updated chain state
					return Ok(())
				}
			},
			_ => (),
		}

		// check if messages have been delivered
		let actual_messages_state = messages_state::<R, MI, LID>();
		let pre_dispatch_messages_state = call_type.pre_dispatch_messages_state();
		if actual_messages_state == Some(pre_dispatch_messages_state) {
			// we only refund relayer if all calls have updated chain state
			return Ok(())
		}

		// regarding the tip - refund that happens here (at this side of the bridge) isn't the whole
		// relayer compensation. He'll receive some amount at the other side of the bridge. It shall
		// (in theory) cover the tip here. Otherwise, if we'll be compensating tip here, some
		// malicious relayer may use huge tips, effectively depleting account that pay rewards. The
		// cost of this attack is nothing. Hence we use zero as tip here.
		let tip = Zero::zero();

		// compute the relayer reward
		let reward = FEE::compute_fee(info, post_info, len, tip);

		// finally - register reward in relayers pallet
		RelayersPallet::<R>::register_relayer_reward(LID::get(), &relayer, reward);

		Ok(())
	}
}

/// Extracts expected relay chain state from the call.
fn extract_expected_relay_chain_state<R, GI>(call: &CallOf<R>) -> Option<ExpectedRelayChainState>
where
	R: GrandpaConfig<GI>,
	GI: 'static,
	<R as GrandpaConfig<GI>>::BridgedChain: Chain<BlockNumber = RelayBlockNumber>,
	CallOf<R>: IsSubType<CallableCallFor<GrandpaPallet<R, GI>, R>>,
{
	if let Some(GrandpaCall::<R, GI>::submit_finality_proof { ref finality_target, .. }) =
		call.is_sub_type()
	{
		return Some(ExpectedRelayChainState { best_block_number: *finality_target.number() })
	}
	None
}

/// Extracts expected parachain state from the call.
fn extract_expected_parachain_state<R, GI, PI, PID>(
	call: &CallOf<R>,
) -> Option<ExpectedParachainState>
where
	R: GrandpaConfig<GI> + ParachainsConfig<PI, BridgesGrandpaPalletInstance = GI>,
	GI: 'static,
	PI: 'static,
	PID: Get<u32>,
	<R as GrandpaConfig<GI>>::BridgedChain:
		Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>,
	CallOf<R>: IsSubType<CallableCallFor<ParachainsPallet<R, PI>, R>>,
{
	if let Some(ParachainsCall::<R, PI>::submit_parachain_heads {
		ref at_relay_block,
		ref parachains,
		..
	}) = call.is_sub_type()
	{
		if parachains.len() != 1 || parachains[0].0 != ParaId(PID::get()) {
			return None
		}

		return Some(ExpectedParachainState { at_relay_block_number: at_relay_block.0 })
	}
	None
}

/// Extracts messages state from the call.
fn extract_messages_state<R, GI, MI, LID>(call: &CallOf<R>) -> Option<MessagesState>
where
	R: GrandpaConfig<GI> + MessagesConfig<MI>,
	GI: 'static,
	MI: 'static,
	LID: Get<LaneId>,
	CallOf<R>: IsSubType<CallableCallFor<MessagesPallet<R, MI>, R>>,
	<R as MessagesConfig<MI>>::SourceHeaderChain: SourceHeaderChain<
		MessagesProof = FromBridgedChainMessagesProof<HashOf<BridgedChain<R, GI>>>,
	>,
{
	if let Some(MessagesCall::<R, MI>::receive_messages_proof { ref proof, .. }) =
		call.is_sub_type()
	{
		if LID::get() != proof.lane {
			return None
		}

		return Some(MessagesState {
			best_nonce: MessagesPallet::<R, MI>::inbound_lane_data(proof.lane)
				.last_delivered_nonce(),
		})
	}
	None
}

/// Returns relay chain state that we are interested in.
fn relay_chain_state<R, GI>() -> Option<ExpectedRelayChainState>
where
	R: GrandpaConfig<GI>,
	GI: 'static,
	<R as GrandpaConfig<GI>>::BridgedChain: Chain<BlockNumber = RelayBlockNumber>,
{
	GrandpaPallet::<R, GI>::best_finalized_number()
		.map(|best_block_number| ExpectedRelayChainState { best_block_number })
}

/// Returns parachain state that we are interested in.
fn parachain_state<R, PI, PID>() -> Option<ExpectedParachainState>
where
	R: ParachainsConfig<PI>,
	PI: 'static,
	PID: Get<u32>,
{
	ParachainsPallet::<R, PI>::best_parachain_info(ParaId(PID::get())).map(|para_info| {
		ExpectedParachainState {
			at_relay_block_number: para_info.best_head_hash.at_relay_block_number,
		}
	})
}

/// Returns messages state that we are interested in.
fn messages_state<R, MI, LID>() -> Option<MessagesState>
where
	R: MessagesConfig<MI>,
	MI: 'static,
	LID: Get<LaneId>,
{
	Some(MessagesState {
		best_nonce: MessagesPallet::<R, MI>::inbound_lane_data(LID::get()).last_delivered_nonce(),
	})
}

#[cfg(test)]
mod tests {
	use super::*;
	use bp_messages::InboundLaneData;
	use bp_parachains::{BestParaHeadHash, ParaInfo};
	use bp_polkadot_core::parachains::ParaHeadsProof;
	use bp_runtime::HeaderId;
	use bp_test_utils::make_default_justification;
	use frame_support::{assert_storage_noop, parameter_types, weights::Weight};
	use millau_runtime::{
		RialtoGrandpaInstance, Runtime, RuntimeCall, WithRialtoParachainMessagesInstance,
		WithRialtoParachainsInstance,
	};
	use sp_runtime::{transaction_validity::InvalidTransaction, DispatchError};

	parameter_types! {
		pub TestParachain: u32 = 1000;
		pub TestLaneId: LaneId = [0, 0, 0, 0];
	}

	type TestExtension = RefundRelayerForMessagesFromParachain<
		millau_runtime::Runtime,
		RialtoGrandpaInstance,
		WithRialtoParachainsInstance,
		WithRialtoParachainMessagesInstance,
		millau_runtime::BridgeRejectObsoleteHeadersAndMessages,
		TestParachain,
		TestLaneId,
		millau_runtime::Runtime,
	>;

	fn relayer_account() -> millau_runtime::AccountId {
		[0u8; 32].into()
	}

	fn initialize_environment(
		best_relay_header_number: RelayBlockNumber,
		parachain_head_at_relay_header_number: RelayBlockNumber,
		best_delivered_message: MessageNonce,
	) {
		let best_relay_header = HeaderId(best_relay_header_number, RelayBlockHash::default());
		pallet_bridge_grandpa::BestFinalized::<Runtime, RialtoGrandpaInstance>::put(
			best_relay_header,
		);

		let para_id = ParaId(TestParachain::get());
		let para_info = ParaInfo {
			best_head_hash: BestParaHeadHash {
				at_relay_block_number: parachain_head_at_relay_header_number,
				head_hash: Default::default(),
			},
			next_imported_hash_position: 0,
		};
		pallet_bridge_parachains::ParasInfo::<Runtime, WithRialtoParachainsInstance>::insert(
			para_id, para_info,
		);

		let lane_id = TestLaneId::get();
		let lane_data =
			InboundLaneData { last_confirmed_nonce: best_delivered_message, ..Default::default() };
		pallet_bridge_messages::InboundLanes::<Runtime, WithRialtoParachainMessagesInstance>::insert(lane_id, lane_data);
	}

	fn submit_relay_header_call(relay_header_number: RelayBlockNumber) -> RuntimeCall {
		let relay_header = bp_rialto::Header::new(
			relay_header_number,
			Default::default(),
			Default::default(),
			Default::default(),
			Default::default(),
		);
		let relay_justification = make_default_justification(&relay_header);

		RuntimeCall::BridgeRialtoGrandpa(GrandpaCall::submit_finality_proof {
			finality_target: Box::new(relay_header),
			justification: relay_justification,
		})
	}

	fn submit_parachain_head_call(
		parachain_head_at_relay_header_number: RelayBlockNumber,
	) -> RuntimeCall {
		RuntimeCall::BridgeRialtoParachains(ParachainsCall::submit_parachain_heads {
			at_relay_block: (parachain_head_at_relay_header_number, RelayBlockHash::default()),
			parachains: vec![(ParaId(TestParachain::get()), [1u8; 32].into())],
			parachain_heads_proof: ParaHeadsProof(vec![]),
		})
	}

	fn message_delivery_call(best_message: MessageNonce) -> RuntimeCall {
		RuntimeCall::BridgeRialtoParachainMessages(MessagesCall::receive_messages_proof {
			relayer_id_at_bridged_chain: relayer_account(),
			proof: millau_runtime::bridge_runtime_common::messages::target::FromBridgedChainMessagesProof {
				bridged_header_hash: Default::default(),
				storage_proof: vec![],
				lane: TestLaneId::get(),
				nonces_start: best_message,
				nonces_end: best_message,
			},
			messages_count: 1,
			dispatch_weight: Weight::zero(),
		})
	}

	fn parachain_finality_and_delivery_batch_call(
		parachain_head_at_relay_header_number: RelayBlockNumber,
		best_message: MessageNonce,
	) -> RuntimeCall {
		RuntimeCall::Utility(UtilityCall::batch_all {
			calls: vec![
				submit_parachain_head_call(parachain_head_at_relay_header_number),
				message_delivery_call(best_message),
			],
		})
	}

	fn all_finality_and_delivery_batch_call(
		relay_header_number: RelayBlockNumber,
		parachain_head_at_relay_header_number: RelayBlockNumber,
		best_message: MessageNonce,
	) -> RuntimeCall {
		RuntimeCall::Utility(UtilityCall::batch_all {
			calls: vec![
				submit_relay_header_call(relay_header_number),
				submit_parachain_head_call(parachain_head_at_relay_header_number),
				message_delivery_call(best_message),
			],
		})
	}

	fn all_finality_pre_dispatch_data() -> PreDispatchData<millau_runtime::AccountId> {
		PreDispatchData {
			relayer: relayer_account(),
			call_type: CallType::AllFinalityAndDelivery(
				ExpectedRelayChainState { best_block_number: 200 },
				ExpectedParachainState { at_relay_block_number: 200 },
				MessagesState { best_nonce: 100 },
			),
		}
	}

	fn parachain_finality_pre_dispatch_data() -> PreDispatchData<millau_runtime::AccountId> {
		PreDispatchData {
			relayer: relayer_account(),
			call_type: CallType::ParachainFinalityAndDelivery(
				ExpectedParachainState { at_relay_block_number: 200 },
				MessagesState { best_nonce: 100 },
			),
		}
	}

	fn delivery_pre_dispatch_data() -> PreDispatchData<millau_runtime::AccountId> {
		PreDispatchData {
			relayer: relayer_account(),
			call_type: CallType::Delivery(MessagesState { best_nonce: 100 }),
		}
	}

	fn run_test(test: impl FnOnce()) {
		sp_io::TestExternalities::new(Default::default()).execute_with(test)
	}

	fn run_validate(call: RuntimeCall) -> TransactionValidity {
		let extension: TestExtension = RefundRelayerForMessagesFromParachain(PhantomData);
		extension.validate(&relayer_account(), &call, &DispatchInfo::default(), 0)
	}

	fn run_pre_dispatch(
		call: RuntimeCall,
	) -> Result<Option<PreDispatchData<millau_runtime::AccountId>>, TransactionValidityError> {
		let extension: TestExtension = RefundRelayerForMessagesFromParachain(PhantomData);
		extension.pre_dispatch(&relayer_account(), &call, &DispatchInfo::default(), 0)
	}

	fn dispatch_info() -> DispatchInfo {
		DispatchInfo {
			weight: frame_support::weights::constants::WEIGHT_PER_SECOND,
			class: frame_support::dispatch::DispatchClass::Normal,
			pays_fee: frame_support::dispatch::Pays::Yes,
		}
	}

	fn post_dispatch_info() -> PostDispatchInfo {
		PostDispatchInfo { actual_weight: None, pays_fee: frame_support::dispatch::Pays::Yes }
	}

	fn run_post_dispatch(
		pre_dispatch_data: Option<PreDispatchData<millau_runtime::AccountId>>,
		dispatch_result: DispatchResult,
	) {
		let post_dispatch_result = TestExtension::post_dispatch(
			Some(pre_dispatch_data),
			&dispatch_info(),
			&post_dispatch_info(),
			1024,
			&dispatch_result,
		);
		assert_eq!(post_dispatch_result, Ok(()));
	}

	fn expected_reward() -> millau_runtime::Balance {
		pallet_transaction_payment::Pallet::<Runtime>::compute_actual_fee(
			1024,
			&dispatch_info(),
			&post_dispatch_info(),
			Zero::zero(),
		)
	}

	#[test]
	fn validate_allows_non_obsolete_transactions() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(run_validate(message_delivery_call(200)), Ok(ValidTransaction::default()),);

			assert_eq!(
				run_validate(parachain_finality_and_delivery_batch_call(200, 200)),
				Ok(ValidTransaction::default()),
			);

			assert_eq!(
				run_validate(all_finality_and_delivery_batch_call(200, 200, 200)),
				Ok(ValidTransaction::default()),
			);
		});
	}

	#[test]
	fn ext_rejects_batch_with_obsolete_relay_chain_header() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(all_finality_and_delivery_batch_call(100, 200, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_validate(all_finality_and_delivery_batch_call(100, 200, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);
		});
	}

	#[test]
	fn ext_rejects_batch_with_obsolete_parachain_head() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(all_finality_and_delivery_batch_call(101, 100, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_pre_dispatch(parachain_finality_and_delivery_batch_call(100, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_validate(all_finality_and_delivery_batch_call(101, 100, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_validate(parachain_finality_and_delivery_batch_call(100, 200)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);
		});
	}

	#[test]
	fn ext_rejects_batch_with_obsolete_messages() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(all_finality_and_delivery_batch_call(200, 200, 100)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_pre_dispatch(parachain_finality_and_delivery_batch_call(200, 100)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_validate(all_finality_and_delivery_batch_call(200, 200, 100)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);

			assert_eq!(
				run_validate(parachain_finality_and_delivery_batch_call(200, 100)),
				Err(TransactionValidityError::Invalid(InvalidTransaction::Stale)),
			);
		});
	}

	#[test]
	fn pre_dispatch_parses_batch_with_relay_chain_and_parachain_headers() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(all_finality_and_delivery_batch_call(200, 200, 200)),
				Ok(Some(all_finality_pre_dispatch_data())),
			);
		});
	}

	#[test]
	fn pre_dispatch_parses_batch_with_parachain_header() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(parachain_finality_and_delivery_batch_call(200, 200)),
				Ok(Some(parachain_finality_pre_dispatch_data())),
			);
		});
	}

	#[test]
	fn pre_dispatch_fails_to_parse_batch_with_multiple_parachain_headers() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			let call = RuntimeCall::Utility(UtilityCall::batch_all {
				calls: vec![
					RuntimeCall::BridgeRialtoParachains(ParachainsCall::submit_parachain_heads {
						at_relay_block: (100, RelayBlockHash::default()),
						parachains: vec![
							(ParaId(TestParachain::get()), [1u8; 32].into()),
							(ParaId(TestParachain::get() + 1), [1u8; 32].into()),
						],
						parachain_heads_proof: ParaHeadsProof(vec![]),
					}),
					message_delivery_call(200),
				],
			});

			assert_eq!(run_pre_dispatch(call), Ok(None),);
		});
	}

	#[test]
	fn pre_dispatch_parses_message_delivery_transaction() {
		run_test(|| {
			initialize_environment(100, 100, 100);

			assert_eq!(
				run_pre_dispatch(message_delivery_call(200)),
				Ok(Some(delivery_pre_dispatch_data())),
			);
		});
	}

	#[test]
	fn post_dispatch_ignores_unknown_transaction() {
		run_test(|| {
			assert_storage_noop!(run_post_dispatch(None, Ok(())));
		});
	}

	#[test]
	fn post_dispatch_ignores_failed_transaction() {
		run_test(|| {
			assert_storage_noop!(run_post_dispatch(
				Some(all_finality_pre_dispatch_data()),
				Err(DispatchError::BadOrigin)
			));
		});
	}

	#[test]
	fn post_dispatch_ignores_transaction_that_has_not_updated_relay_chain_state() {
		run_test(|| {
			initialize_environment(100, 200, 200);

			assert_storage_noop!(run_post_dispatch(Some(all_finality_pre_dispatch_data()), Ok(())));
		});
	}

	#[test]
	fn post_dispatch_ignores_transaction_that_has_not_updated_parachain_state() {
		run_test(|| {
			initialize_environment(200, 100, 200);

			assert_storage_noop!(run_post_dispatch(Some(all_finality_pre_dispatch_data()), Ok(())));
			assert_storage_noop!(run_post_dispatch(
				Some(parachain_finality_pre_dispatch_data()),
				Ok(())
			));
		});
	}

	#[test]
	fn post_dispatch_ignores_transaction_that_has_not_delivered_any_messages() {
		run_test(|| {
			initialize_environment(200, 200, 100);

			assert_storage_noop!(run_post_dispatch(Some(all_finality_pre_dispatch_data()), Ok(())));
			assert_storage_noop!(run_post_dispatch(
				Some(parachain_finality_pre_dispatch_data()),
				Ok(())
			));
			assert_storage_noop!(run_post_dispatch(Some(delivery_pre_dispatch_data()), Ok(())));
		});
	}

	#[test]
	fn post_dispatch_refunds_relayer_in_all_finality_batch() {
		run_test(|| {
			initialize_environment(200, 200, 200);

			run_post_dispatch(Some(all_finality_pre_dispatch_data()), Ok(()));
			assert_eq!(
				RelayersPallet::<Runtime>::relayer_reward(relayer_account(), TestLaneId::get()),
				Some(expected_reward()),
			);
		});
	}

	#[test]
	fn post_dispatch_refunds_relayer_in_parachain_finality_batch() {
		run_test(|| {
			initialize_environment(200, 200, 200);

			run_post_dispatch(Some(parachain_finality_pre_dispatch_data()), Ok(()));
			assert_eq!(
				RelayersPallet::<Runtime>::relayer_reward(relayer_account(), TestLaneId::get()),
				Some(expected_reward()),
			);
		});
	}

	#[test]
	fn post_dispatch_refunds_relayer_in_message_delivery_transaction() {
		run_test(|| {
			initialize_environment(200, 200, 200);

			run_post_dispatch(Some(delivery_pre_dispatch_data()), Ok(()));
			assert_eq!(
				RelayersPallet::<Runtime>::relayer_reward(relayer_account(), TestLaneId::get()),
				Some(expected_reward()),
			);
		});
	}
}