Complex RialtoParachain <> Millau relay (#1405)

* complex parachain relay

* fix spelling

bridges/relays/lib-substrate-relay/src/parachains/target.rs

@@ -0,0 +1,161 @@
+// 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/>.
+
+//! Parachain heads target.
+
+use crate::{
+	parachains::{
+		ParachainsPipelineAdapter, SubmitParachainHeadsCallBuilder, SubstrateParachainsPipeline,
+	},
+	TransactionParams,
+};
+
+use async_trait::async_trait;
+use bp_parachains::{parachain_head_storage_key_at_target, BestParaHeadHash};
+use bp_polkadot_core::parachains::{ParaHeadsProof, ParaId};
+use codec::{Decode, Encode};
+use parachains_relay::parachains_loop::TargetClient;
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, BlockNumberOf, Chain, Client, Error as SubstrateError, HashOf,
+	HeaderIdOf, RelayChain, SignParam, TransactionEra, TransactionSignScheme, UnsignedTransaction,
+};
+use relay_utils::{relay_loop::Client as RelayClient, HeaderId};
+use sp_core::{Bytes, Pair};
+use sp_runtime::traits::Header as HeaderT;
+
+/// Substrate client as parachain heads source.
+pub struct ParachainsTarget<P: SubstrateParachainsPipeline> {
+	client: Client<P::TargetChain>,
+	transaction_params: TransactionParams<AccountKeyPairOf<P::TransactionSignScheme>>,
+}
+
+impl<P: SubstrateParachainsPipeline> ParachainsTarget<P> {
+	/// Creates new parachains target client.
+	pub fn new(
+		client: Client<P::TargetChain>,
+		transaction_params: TransactionParams<AccountKeyPairOf<P::TransactionSignScheme>>,
+	) -> Self {
+		ParachainsTarget { client, transaction_params }
+	}
+
+	/// Returns reference to the underlying RPC client.
+	pub fn client(&self) -> &Client<P::TargetChain> {
+		&self.client
+	}
+}
+
+impl<P: SubstrateParachainsPipeline> Clone for ParachainsTarget<P> {
+	fn clone(&self) -> Self {
+		ParachainsTarget {
+			client: self.client.clone(),
+			transaction_params: self.transaction_params.clone(),
+		}
+	}
+}
+
+#[async_trait]
+impl<P: SubstrateParachainsPipeline> RelayClient for ParachainsTarget<P> {
+	type Error = SubstrateError;
+
+	async fn reconnect(&mut self) -> Result<(), SubstrateError> {
+		self.client.reconnect().await
+	}
+}
+
+#[async_trait]
+impl<P> TargetClient<ParachainsPipelineAdapter<P>> for ParachainsTarget<P>
+where
+	P: SubstrateParachainsPipeline,
+	P::TransactionSignScheme: TransactionSignScheme<Chain = P::TargetChain>,
+	AccountIdOf<P::TargetChain>: From<<AccountKeyPairOf<P::TransactionSignScheme> as Pair>::Public>,
+{
+	async fn best_block(&self) -> Result<HeaderIdOf<P::TargetChain>, Self::Error> {
+		let best_header = self.client.best_header().await?;
+		let best_hash = best_header.hash();
+		let best_id = HeaderId(*best_header.number(), best_hash);
+
+		Ok(best_id)
+	}
+
+	async fn best_finalized_source_block(
+		&self,
+		at_block: &HeaderIdOf<P::TargetChain>,
+	) -> Result<HeaderIdOf<P::SourceRelayChain>, Self::Error> {
+		let encoded_best_finalized_source_block = self
+			.client
+			.state_call(
+				P::SourceRelayChain::BEST_FINALIZED_HEADER_ID_METHOD.into(),
+				Bytes(Vec::new()),
+				Some(at_block.1),
+			)
+			.await?;
+		let decoded_best_finalized_source_block: (
+			BlockNumberOf<P::SourceRelayChain>,
+			HashOf<P::SourceRelayChain>,
+		) = Decode::decode(&mut &encoded_best_finalized_source_block.0[..])
+			.map_err(SubstrateError::ResponseParseFailed)?;
+		Ok(HeaderId(decoded_best_finalized_source_block.0, decoded_best_finalized_source_block.1))
+	}
+
+	async fn parachain_head(
+		&self,
+		at_block: HeaderIdOf<P::TargetChain>,
+		para_id: ParaId,
+	) -> Result<Option<BestParaHeadHash>, Self::Error> {
+		let storage_key = parachain_head_storage_key_at_target(
+			P::SourceRelayChain::PARACHAINS_FINALITY_PALLET_NAME,
+			para_id,
+		);
+		let para_head = self.client.storage_value(storage_key, Some(at_block.1)).await?;
+
+		Ok(para_head)
+	}
+
+	async fn submit_parachain_heads_proof(
+		&self,
+		at_relay_block: HeaderIdOf<P::SourceRelayChain>,
+		updated_parachains: Vec<ParaId>,
+		proof: ParaHeadsProof,
+	) -> Result<(), Self::Error> {
+		let genesis_hash = *self.client.genesis_hash();
+		let transaction_params = self.transaction_params.clone();
+		let (spec_version, transaction_version) = self.client.simple_runtime_version().await?;
+		let call = P::SubmitParachainHeadsCallBuilder::build_submit_parachain_heads_call(
+			at_relay_block.1,
+			updated_parachains,
+			proof,
+		);
+		self.client
+			.submit_signed_extrinsic(
+				self.transaction_params.signer.public().into(),
+				move |best_block_id, transaction_nonce| {
+					Ok(Bytes(
+						P::TransactionSignScheme::sign_transaction(SignParam {
+							spec_version,
+							transaction_version,
+							genesis_hash,
+							signer: transaction_params.signer,
+							era: TransactionEra::new(best_block_id, transaction_params.mortality),
+							unsigned: UnsignedTransaction::new(call.into(), transaction_nonce),
+						})?
+						.encode(),
+					))
+				},
+			)
+			.await
+			.map(drop)
+	}
+}