Integrate Rialto <-> Millau message lanes into Millau/Rialto runtimes (#386)

* millau -> rialto lanes integration

* extrace common message-lane integration types into bridge-runtime-common

* rialto_messages.rs in Millau runtime

* tests

* Update bin/rialto/runtime/src/millau_messages.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* RELAYER_INTEREST_PERCENT -> RELAYER_FEE_PERCENT

* Update bin/runtime-common/src/messages.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* estimate_message_dispatch_and_delivery_fee returns Result

* Update bin/rialto/runtime/src/millau_messages.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* Update bin/rialto/runtime/src/millau_messages.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* Update bin/rialto/runtime/src/millau_messages.rs

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

* fmt

* mowed weight formula to primitives

Co-authored-by: Hernando Castano <HCastano@users.noreply.github.com>

bridges/modules/message-lane/src/instant_payments.rs

@@ -0,0 +1,75 @@
+// 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/>.
+
+//! Implementation of `MessageDeliveryAndDispatchPayment` trait on top of `Currency` trait.
+//! All payments are instant.
+
+use bp_message_lane::source_chain::MessageDeliveryAndDispatchPayment;
+use bp_runtime::{bridge_account_id, MESSAGE_LANE_MODULE_PREFIX, NO_INSTANCE_ID};
+use codec::Decode;
+use frame_support::traits::{Currency as CurrencyT, ExistenceRequirement};
+use sp_std::fmt::Debug;
+
+/// Instant message payments made in given currency. Until claimed, fee is stored in special
+/// 'relayers-fund' account.
+pub struct InstantCurrencyPayments<AccountId, Currency> {
+	_phantom: sp_std::marker::PhantomData<(AccountId, Currency)>,
+}
+
+impl<AccountId, Currency> MessageDeliveryAndDispatchPayment<AccountId, Currency::Balance>
+	for InstantCurrencyPayments<AccountId, Currency>
+where
+	Currency: CurrencyT<AccountId>,
+	AccountId: Debug + Default + Decode,
+{
+	type Error = &'static str;
+
+	fn pay_delivery_and_dispatch_fee(submitter: &AccountId, fee: &Currency::Balance) -> Result<(), Self::Error> {
+		Currency::transfer(
+			submitter,
+			&relayers_fund_account(),
+			*fee,
+			ExistenceRequirement::AllowDeath,
+		)
+		.map_err(Into::into)
+	}
+
+	fn pay_relayer_reward(_confirmation_relayer: &AccountId, relayer: &AccountId, reward: &Currency::Balance) {
+		let pay_result = Currency::transfer(
+			&relayers_fund_account(),
+			relayer,
+			*reward,
+			ExistenceRequirement::AllowDeath,
+		);
+
+		// we can't actually do anything here, because rewards are paid as a part of unrelated transaction
+		if let Err(error) = pay_result {
+			frame_support::debug::trace!(
+				target: "runtime",
+				"Failed to pay relayer {:?} reward {:?}: {:?}",
+				relayer,
+				reward,
+				error,
+			);
+		}
+	}
+}
+
+/// Return account id of shared relayers-fund account that is storing all fees
+/// paid by submitters, until they're claimed by relayers.
+fn relayers_fund_account<AccountId: Default + Decode>() -> AccountId {
+	bridge_account_id(NO_INSTANCE_ID, MESSAGE_LANE_MODULE_PREFIX)
+}

bridges/modules/message-lane/src/lib.rs

@@ -48,6 +48,8 @@ use sp_std::{cell::RefCell, marker::PhantomData, prelude::*};
 mod inbound_lane;
 mod outbound_lane;
 
+pub mod instant_payments;
+
 #[cfg(test)]
 mod mock;