Relay subcommands to initialize substrate bridge pallet (#483)

* initialize substrate bridge from relay

* is_halted: false

* initialize using su instead of owner

* Fix wording in comments

Co-authored-by: Hernando Castano <castano.ha@gmail.com>

bridges/relays/substrate/src/headers_initialize.rs

@@ -0,0 +1,141 @@
+// 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/>.
+
+//! Initialize Substrate -> Substrate headers bridge.
+//!
+//! Initialization is a transaction that calls `initialize()` function of the
+//! `pallet-substrate-bridge` pallet. This transaction brings initial header
+//! and authorities set from source to target chain. The headers sync starts
+//! with this header.
+
+use codec::Decode;
+use pallet_substrate_bridge::InitializationData;
+use relay_substrate_client::{Chain, Client};
+use sp_core::Bytes;
+use sp_finality_grandpa::{AuthorityList as GrandpaAuthoritiesSet, SetId as GrandpaAuthoritiesSetId};
+
+/// Submit headers-bridge initialization transaction.
+pub async fn initialize<SourceChain: Chain, TargetChain: Chain>(
+	source_client: Client<SourceChain>,
+	target_client: Client<TargetChain>,
+	raw_initial_header: Option<Bytes>,
+	raw_initial_authorities_set: Option<Bytes>,
+	initial_authorities_set_id: Option<GrandpaAuthoritiesSetId>,
+	prepare_initialize_transaction: impl FnOnce(InitializationData<SourceChain::Header>) -> Result<Bytes, String>,
+) {
+	let result = do_initialize(
+		source_client,
+		target_client,
+		raw_initial_header,
+		raw_initial_authorities_set,
+		initial_authorities_set_id,
+		prepare_initialize_transaction,
+	)
+	.await;
+
+	match result {
+		Ok(tx_hash) => log::info!(
+			target: "bridge",
+			"Successfully submitted {}-headers bridge initialization transaction to {}: {:?}",
+			SourceChain::NAME,
+			TargetChain::NAME,
+			tx_hash,
+		),
+		Err(err) => log::error!(
+			target: "bridge",
+			"Failed to submit {}-headers bridge initialization transaction to {}: {:?}",
+			SourceChain::NAME,
+			TargetChain::NAME,
+			err,
+		),
+	}
+}
+
+/// Craft and submit initialization transaction, returning any error that may occur.
+async fn do_initialize<SourceChain: Chain, TargetChain: Chain>(
+	source_client: Client<SourceChain>,
+	target_client: Client<TargetChain>,
+	raw_initial_header: Option<Bytes>,
+	raw_initial_authorities_set: Option<Bytes>,
+	initial_authorities_set_id: Option<GrandpaAuthoritiesSetId>,
+	prepare_initialize_transaction: impl FnOnce(InitializationData<SourceChain::Header>) -> Result<Bytes, String>,
+) -> Result<TargetChain::Hash, String> {
+	let initialization_data = prepare_initialization_data(
+		source_client,
+		raw_initial_header,
+		raw_initial_authorities_set,
+		initial_authorities_set_id,
+	)
+	.await?;
+	let initialization_tx = prepare_initialize_transaction(initialization_data)?;
+	let initialization_tx_hash = target_client
+		.submit_extrinsic(initialization_tx)
+		.await
+		.map_err(|err| format!("Failed to submit {} transaction: {:?}", TargetChain::NAME, err))?;
+	Ok(initialization_tx_hash)
+}
+
+/// Prepare initialization data for the headers-bridge pallet.
+async fn prepare_initialization_data<SourceChain: Chain>(
+	source_client: Client<SourceChain>,
+	raw_initial_header: Option<Bytes>,
+	raw_initial_authorities_set: Option<Bytes>,
+	initial_authorities_set_id: Option<GrandpaAuthoritiesSetId>,
+) -> Result<InitializationData<SourceChain::Header>, String> {
+	let source_genesis_hash = *source_client.genesis_hash();
+
+	let initial_header = match raw_initial_header {
+		Some(raw_initial_header) => SourceChain::Header::decode(&mut &raw_initial_header.0[..])
+			.map_err(|err| format!("Failed to decode {} initial header: {:?}", SourceChain::NAME, err))?,
+		None => source_client
+			.header_by_hash(source_genesis_hash)
+			.await
+			.map_err(|err| format!("Failed to retrive {} genesis header: {:?}", SourceChain::NAME, err))?,
+	};
+
+	let raw_initial_authorities_set = match raw_initial_authorities_set {
+		Some(raw_initial_authorities_set) => raw_initial_authorities_set.0,
+		None => source_client
+			.grandpa_authorities_set(source_genesis_hash)
+			.await
+			.map_err(|err| {
+				format!(
+					"Failed to retrive {} authorities set at genesis header: {:?}",
+					SourceChain::NAME,
+					err
+				)
+			})?,
+	};
+	let initial_authorities_set =
+		GrandpaAuthoritiesSet::decode(&mut &raw_initial_authorities_set[..]).map_err(|err| {
+			format!(
+				"Failed to decode {} initial authorities set: {:?}",
+				SourceChain::NAME,
+				err
+			)
+		})?;
+
+	Ok(InitializationData {
+		header: initial_header,
+		authority_list: initial_authorities_set,
+		set_id: initial_authorities_set_id.unwrap_or(0),
+		// There may be multiple scheduled changes, so on real chains we should select proper
+		// moment, when there's nothing scheduled. On ephemeral (temporary) chains, it is ok to
+		// start with genesis.
+		scheduled_change: None,
+		is_halted: false,
+	})
+}