Generic SyncHeader type (paritytech#529)

* generic SyncHeader type

* add panic condition to method description

* extract -> into_inner

* checked_sub + expect

bridges/relays/headers-relay/src/sync_types.rs

@@ -84,6 +84,8 @@ pub trait SourceHeader<Hash, Number>: Clone + std::fmt::Debug + PartialEq + Send
 	/// Returns ID of header.
 	fn id(&self) -> HeaderId<Hash, Number>;
 	/// Returns ID of parent header.
+	///
+	/// Panics if called for genesis header.
 	fn parent_id(&self) -> HeaderId<Hash, Number>;
 }
 

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

@@ -17,13 +17,9 @@
 //! Types used to connect to the Millau-Substrate chain.
 
 use codec::Encode;
-use headers_relay::sync_types::SourceHeader;
 use relay_substrate_client::{Chain, ChainBase, ChainWithBalances, Client, TransactionSignScheme};
 use sp_core::{storage::StorageKey, Pair};
-use sp_runtime::{
-	generic::SignedPayload,
-	traits::{Header as HeaderT, IdentifyAccount},
-};
+use sp_runtime::{generic::SignedPayload, traits::IdentifyAccount};
 use std::time::Duration;
 
 pub use millau_runtime::BridgeRialtoCall;
@@ -126,35 +122,4 @@ impl std::fmt::Debug for SigningParams {
 }
 
 /// Millau header type used in headers sync.
-#[derive(Clone, Debug, PartialEq)]
-pub struct SyncHeader(millau_runtime::Header);
-
-impl std::ops::Deref for SyncHeader {
-	type Target = millau_runtime::Header;
-
-	fn deref(&self) -> &Self::Target {
-		&self.0
-	}
-}
-
-impl From<millau_runtime::Header> for SyncHeader {
-	fn from(header: millau_runtime::Header) -> Self {
-		Self(header)
-	}
-}
-
-impl From<SyncHeader> for millau_runtime::Header {
-	fn from(header: SyncHeader) -> Self {
-		header.0
-	}
-}
-
-impl SourceHeader<millau_runtime::Hash, millau_runtime::BlockNumber> for SyncHeader {
-	fn id(&self) -> HeaderId {
-		relay_utils::HeaderId(*self.number(), self.hash())
-	}
-
-	fn parent_id(&self) -> HeaderId {
-		relay_utils::HeaderId(*self.number() - 1, *self.parent_hash())
-	}
-}
+pub type SyncHeader = relay_substrate_client::SyncHeader<millau_runtime::Header>;

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

@@ -17,13 +17,9 @@
 //! Types used to connect to the Rialto-Substrate chain.
 
 use codec::Encode;
-use headers_relay::sync_types::SourceHeader;
 use relay_substrate_client::{Chain, ChainBase, ChainWithBalances, Client, TransactionSignScheme};
 use sp_core::{storage::StorageKey, Pair};
-use sp_runtime::{
-	generic::SignedPayload,
-	traits::{Header as HeaderT, IdentifyAccount},
-};
+use sp_runtime::{generic::SignedPayload, traits::IdentifyAccount};
 use std::time::Duration;
 
 pub use rialto_runtime::BridgeMillauCall;
@@ -134,35 +130,4 @@ impl Default for SigningParams {
 }
 
 /// Rialto header type used in headers sync.
-#[derive(Clone, Debug, PartialEq)]
-pub struct SyncHeader(rialto_runtime::Header);
-
-impl std::ops::Deref for SyncHeader {
-	type Target = rialto_runtime::Header;
-
-	fn deref(&self) -> &Self::Target {
-		&self.0
-	}
-}
-
-impl From<rialto_runtime::Header> for SyncHeader {
-	fn from(header: rialto_runtime::Header) -> Self {
-		Self(header)
-	}
-}
-
-impl From<SyncHeader> for rialto_runtime::Header {
-	fn from(header: SyncHeader) -> Self {
-		header.0
-	}
-}
-
-impl SourceHeader<rialto_runtime::Hash, rialto_runtime::BlockNumber> for SyncHeader {
-	fn id(&self) -> HeaderId {
-		relay_utils::HeaderId(*self.number(), self.hash())
-	}
-
-	fn parent_id(&self) -> HeaderId {
-		relay_utils::HeaderId(*self.number() - 1, *self.parent_hash())
-	}
-}
+pub type SyncHeader = relay_substrate_client::SyncHeader<rialto_runtime::Header>;

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

@@ -22,13 +22,15 @@ mod chain;
 mod client;
 mod error;
 mod rpc;
+mod sync_header;
 
 pub mod guard;
 pub mod headers_source;
 
 pub use crate::chain::{BlockWithJustification, Chain, ChainWithBalances, TransactionSignScheme};
 pub use crate::client::{Client, JustificationsSubscription, OpaqueGrandpaAuthoritiesSet};
 pub use crate::error::{Error, Result};
+pub use crate::sync_header::SyncHeader;
 pub use bp_runtime::{BlockNumberOf, Chain as ChainBase, HashOf, HeaderOf};
 
 /// Header id used by the chain.

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

@@ -0,0 +1,61 @@
+// 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/>.
+
+use headers_relay::sync_types::SourceHeader;
+use num_traits::{CheckedSub, One};
+use relay_utils::HeaderId;
+use sp_runtime::traits::Header as HeaderT;
+
+/// Generic wrapper for `sp_runtime::traits::Header` based headers, that
+/// implements `headers_relay::sync_types::SourceHeader` and may be used in headers sync directly.
+#[derive(Clone, Debug, PartialEq)]
+pub struct SyncHeader<Header>(Header);
+
+impl<Header> SyncHeader<Header> {
+	/// Extracts wrapped header from self.
+	pub fn into_inner(self) -> Header {
+		self.0
+	}
+}
+
+impl<Header> std::ops::Deref for SyncHeader<Header> {
+	type Target = Header;
+
+	fn deref(&self) -> &Self::Target {
+		&self.0
+	}
+}
+
+impl<Header> From<Header> for SyncHeader<Header> {
+	fn from(header: Header) -> Self {
+		Self(header)
+	}
+}
+
+impl<Header: HeaderT> SourceHeader<Header::Hash, Header::Number> for SyncHeader<Header> {
+	fn id(&self) -> HeaderId<Header::Hash, Header::Number> {
+		relay_utils::HeaderId(*self.number(), self.hash())
+	}
+
+	fn parent_id(&self) -> HeaderId<Header::Hash, Header::Number> {
+		relay_utils::HeaderId(
+			self.number()
+				.checked_sub(&One::one())
+				.expect("should never be called for genesis header"),
+			*self.parent_hash(),
+		)
+	}
+}

bridges/relays/substrate/src/millau_headers_to_rialto.rs

@@ -54,7 +54,7 @@ impl SubstrateHeadersSyncPipeline for MillauHeadersToRialto {
 	) -> Result<Self::SignedTransaction, SubstrateError> {
 		let account_id = self.target_sign.signer.public().as_array_ref().clone().into();
 		let nonce = self.target_client.next_account_index(account_id).await?;
-		let call = BridgeMillauCall::import_signed_header(header.header().clone().into()).into();
+		let call = BridgeMillauCall::import_signed_header(header.header().clone().into_inner()).into();
 		let transaction = Rialto::sign_transaction(&self.target_client, &self.target_sign.signer, nonce, call);
 		Ok(transaction)
 	}

bridges/relays/substrate/src/rialto_headers_to_millau.rs

@@ -53,7 +53,7 @@ impl SubstrateHeadersSyncPipeline for RialtoHeadersToMillau {
 	) -> Result<Self::SignedTransaction, SubstrateError> {
 		let account_id = self.target_sign.signer.public().as_array_ref().clone().into();
 		let nonce = self.target_client.next_account_index(account_id).await?;
-		let call = BridgeRialtoCall::import_signed_header(header.header().clone().into()).into();
+		let call = BridgeRialtoCall::import_signed_header(header.header().clone().into_inner()).into();
 		let transaction = Millau::sign_transaction(&self.target_client, &self.target_sign.signer, nonce, call);
 		Ok(transaction)
 	}