finality_target.rs

// Copyright 2019-2021 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/>.

//! Substrate client as Substrate finality proof target. The chain we connect to should have
//! bridge GRANDPA pallet deployed and provide `<BridgedChainName>FinalityApi` to allow bridging
//! with <BridgedName> chain.

use crate::{
	finality_pipeline::{
		FinalitySyncPipelineAdapter, SubmitFinalityProofCallBuilder, SubstrateFinalitySyncPipeline,
	},
	TransactionParams,
};

use async_trait::async_trait;
use bp_header_chain::{justification::GrandpaJustification, storage_keys::is_halted_key};
use codec::Encode;
use finality_relay::TargetClient;
use relay_substrate_client::{
	AccountIdOf, AccountKeyPairOf, BlockNumberOf, Chain, ChainWithGrandpa, Client, Error, HashOf,
	HeaderOf, SignParam, SyncHeader, TransactionEra, TransactionSignScheme, UnsignedTransaction,
};
use relay_utils::relay_loop::Client as RelayClient;
use sp_core::{Bytes, Pair};

/// Substrate client as Substrate finality target.
pub struct SubstrateFinalityTarget<P: SubstrateFinalitySyncPipeline> {
	client: Client<P::TargetChain>,
	transaction_params: TransactionParams<AccountKeyPairOf<P::TransactionSignScheme>>,
}

impl<P: SubstrateFinalitySyncPipeline> SubstrateFinalityTarget<P> {
	/// Create new Substrate headers target.
	pub fn new(
		client: Client<P::TargetChain>,
		transaction_params: TransactionParams<AccountKeyPairOf<P::TransactionSignScheme>>,
	) -> Self {
		SubstrateFinalityTarget { client, transaction_params }
	}

	/// Ensure that the GRANDPA pallet at target chain is active.
	async fn ensure_pallet_active(&self) -> Result<(), Error> {
		let is_halted = self
			.client
			.storage_value(is_halted_key(P::SourceChain::WITH_CHAIN_GRANDPA_PALLET_NAME), None)
			.await?;
		if is_halted.unwrap_or(false) {
			Err(Error::BridgePalletIsHalted)
		} else {
			Ok(())
		}
	}
}

impl<P: SubstrateFinalitySyncPipeline> Clone for SubstrateFinalityTarget<P> {
	fn clone(&self) -> Self {
		SubstrateFinalityTarget {
			client: self.client.clone(),
			transaction_params: self.transaction_params.clone(),
		}
	}
}

#[async_trait]
impl<P: SubstrateFinalitySyncPipeline> RelayClient for SubstrateFinalityTarget<P> {
	type Error = Error;

	async fn reconnect(&mut self) -> Result<(), Error> {
		self.client.reconnect().await
	}
}

#[async_trait]
impl<P: SubstrateFinalitySyncPipeline> TargetClient<FinalitySyncPipelineAdapter<P>>
	for SubstrateFinalityTarget<P>
where
	AccountIdOf<P::TargetChain>: From<<AccountKeyPairOf<P::TransactionSignScheme> as Pair>::Public>,
	P::TransactionSignScheme: TransactionSignScheme<Chain = P::TargetChain>,
{
	async fn best_finalized_source_block_number(
		&self,
	) -> Result<BlockNumberOf<P::SourceChain>, Error> {
		// we can't continue to relay finality if target node is out of sync, because
		// it may have already received (some of) headers that we're going to relay
		self.client.ensure_synced().await?;
		// we can't relay finality if GRANDPA pallet at target chain is halted
		self.ensure_pallet_active().await?;

		Ok(crate::messages_source::read_client_state::<
			P::TargetChain,
			HashOf<P::SourceChain>,
			BlockNumberOf<P::SourceChain>,
		>(&self.client, P::SourceChain::BEST_FINALIZED_HEADER_ID_METHOD)
		.await?
		.best_finalized_peer_at_best_self
		.0)
	}

	async fn submit_finality_proof(
		&self,
		header: SyncHeader<HeaderOf<P::SourceChain>>,
		proof: GrandpaJustification<HeaderOf<P::SourceChain>>,
	) -> Result<(), Error> {
		let genesis_hash = *self.client.genesis_hash();
		let transaction_params = self.transaction_params.clone();
		let call =
			P::SubmitFinalityProofCallBuilder::build_submit_finality_proof_call(header, proof);
		let (spec_version, transaction_version) = self.client.simple_runtime_version().await?;
		self.client
			.submit_signed_extrinsic(
				self.transaction_params.signer.public().into(),
				move |best_block_id, transaction_nonce| {
					Bytes(
						P::TransactionSignScheme::sign_transaction(SignParam {
							spec_version,
							transaction_version,
							genesis_hash,
							signer: transaction_params.signer.clone(),
							era: TransactionEra::new(best_block_id, transaction_params.mortality),
							unsigned: UnsignedTransaction::new(call, transaction_nonce),
						})
						.encode(),
					)
				},
			)
			.await
			.map(drop)
	}
}