Substrate relay stub (#376)

* substrate-relay: initial commit

* MillauHeaderApi and RialtoHeaderApi

* post-merge fixes + TODOs + compilation

bridges/relays/substrate-client/src/chain.rs

@@ -19,9 +19,13 @@ use crate::client::Client;
 use frame_support::Parameter;
 use jsonrpsee::common::{DeserializeOwned, Serialize};
 use sp_core::Pair;
-use sp_runtime::traits::{
-	AtLeast32Bit, AtLeast32BitUnsigned, Bounded, CheckEqual, Dispatchable, Header as HeaderT, MaybeDisplay,
-	MaybeMallocSizeOf, MaybeSerialize, MaybeSerializeDeserialize, Member, SimpleBitOps,
+use sp_runtime::{
+	generic::SignedBlock,
+	traits::{
+		AtLeast32Bit, AtLeast32BitUnsigned, Bounded, CheckEqual, Dispatchable, Header as HeaderT, MaybeDisplay,
+		MaybeMallocSizeOf, MaybeSerialize, MaybeSerializeDeserialize, Member, SimpleBitOps,
+	},
+	Justification,
 };
 use sp_std::fmt::Debug;
 
@@ -63,11 +67,17 @@ pub trait Chain {
 	/// with a sender account.
 	type Index: Parameter + Member + MaybeSerialize + Debug + Default + MaybeDisplay + AtLeast32Bit + Copy;
 	/// Block type.
-	type SignedBlock: Member + Serialize + DeserializeOwned;
+	type SignedBlock: Member + Serialize + DeserializeOwned + BlockWithJustification;
 	/// The aggregated `Call` type.
 	type Call: Dispatchable + Debug;
 }
 
+/// Block with justification.
+pub trait BlockWithJustification {
+	/// Return block justification, if known.
+	fn justification(&self) -> Option<&Justification>;
+}
+
 /// Substrate-based chain transactions signing scheme.
 pub trait TransactionSignScheme {
 	/// Chain that this scheme is to be used.
@@ -85,3 +95,18 @@ pub trait TransactionSignScheme {
 		call: <Self::Chain as Chain>::Call,
 	) -> Self::SignedTransaction;
 }
+
+/// Header type used by the chain.
+pub type HeaderOf<C> = <C as Chain>::Header;
+
+/// Hash type used by the chain.
+pub type HashOf<C> = <C as Chain>::Hash;
+
+/// Block number used by the chain.
+pub type BlockNumberOf<C> = <C as Chain>::BlockNumber;
+
+impl<Block> BlockWithJustification for SignedBlock<Block> {
+	fn justification(&self) -> Option<&Justification> {
+		self.justification.as_ref()
+	}
+}

bridges/relays/substrate-client/src/error.rs

@@ -45,6 +45,12 @@ impl MaybeConnectionError for Error {
 	}
 }
 
+impl From<Error> for String {
+	fn from(error: Error) -> String {
+		error.to_string()
+	}
+}
+
 impl ToString for Error {
 	fn to_string(&self) -> String {
 		match self {

bridges/relays/substrate-client/src/headers_source.rs

@@ -0,0 +1,99 @@
+// Copyright 2019-2020 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/>.
+
+//! Default generic implementation of headers source for basic Substrate client.
+
+use crate::chain::{BlockWithJustification, Chain};
+use crate::client::Client;
+use crate::error::Error;
+
+use async_trait::async_trait;
+use headers_relay::{
+	sync_loop::SourceClient,
+	sync_types::{HeaderIdOf, HeadersSyncPipeline, QueuedHeader, SourceHeader},
+};
+use jsonrpsee::common::DeserializeOwned;
+use num_traits::Saturating;
+use sp_runtime::{traits::Header as HeaderT, Justification};
+use std::marker::PhantomData;
+
+/// Substrate node as headers source.
+pub struct HeadersSource<C: Chain, P> {
+	client: Client<C>,
+	_phantom: PhantomData<P>,
+}
+
+impl<C: Chain, P> HeadersSource<C, P> {
+	/// Create new headers source using given client.
+	pub fn new(client: Client<C>) -> Self {
+		HeadersSource {
+			client,
+			_phantom: Default::default(),
+		}
+	}
+}
+
+#[async_trait]
+impl<C, P> SourceClient<P> for HeadersSource<C, P>
+where
+	C: Chain,
+	C::BlockNumber: Into<u64> + Saturating,
+	C::Header: DeserializeOwned + Into<P::Header>,
+	C::Index: DeserializeOwned,
+	P: HeadersSyncPipeline<Extra = (), Completion = Justification, Hash = C::Hash, Number = C::BlockNumber>,
+	P::Header: SourceHeader<C::Hash, C::BlockNumber>,
+{
+	type Error = Error;
+
+	async fn best_block_number(&self) -> Result<P::Number, Self::Error> {
+		Ok(*self.client.best_header().await?.number())
+	}
+
+	async fn header_by_hash(&self, hash: P::Hash) -> Result<P::Header, Self::Error> {
+		self.client
+			.header_by_hash(hash)
+			.await
+			.map(Into::into)
+			.map_err(Into::into)
+	}
+
+	async fn header_by_number(&self, number: P::Number) -> Result<P::Header, Self::Error> {
+		self.client
+			.header_by_number(number)
+			.await
+			.map(Into::into)
+			.map_err(Into::into)
+	}
+
+	async fn header_completion(
+		&self,
+		id: HeaderIdOf<P>,
+	) -> Result<(HeaderIdOf<P>, Option<P::Completion>), Self::Error> {
+		let hash = id.1;
+		let signed_block = self.client.get_block(Some(hash)).await?;
+		let grandpa_justification = signed_block.justification().cloned();
+
+		Ok((id, grandpa_justification))
+	}
+
+	async fn header_extra(
+		&self,
+		id: HeaderIdOf<P>,
+		_header: QueuedHeader<P>,
+	) -> Result<(HeaderIdOf<P>, ()), Self::Error> {
+		Ok((id, ()))
+	}
+}

bridges/relays/substrate-client/src/lib.rs

@@ -23,7 +23,9 @@ mod client;
 mod error;
 mod rpc;
 
-pub use crate::chain::{Chain, TransactionSignScheme};
+pub mod headers_source;
+
+pub use crate::chain::{BlockNumberOf, BlockWithJustification, Chain, HashOf, HeaderOf, TransactionSignScheme};
 pub use crate::client::{Client, OpaqueGrandpaAuthoritiesSet};
 pub use crate::error::{Error, Result};