Move generic CLI logic to different crate (#2885)

* Move generic CLI logic to separate crate

* Move and rename `CliChain` trait definition

Move it to `relay-substrate-client`

* Move generic cli logic to substrate-relay-helper

* Fix docs warnings

bridges/relays/lib-substrate-relay/Cargo.toml

@@ -10,14 +10,17 @@ workspace = true
 
 [dependencies]
 anyhow = "1.0"
-thiserror = { workspace = true }
 async-std = "1.9.0"
 async-trait = "0.1"
 codec = { package = "parity-scale-codec", version = "3.1.5" }
 futures = "0.3.30"
 hex = "0.4"
-num-traits = "0.2"
 log = { workspace = true }
+num-traits = "0.2"
+rbtag = "0.3"
+structopt = "0.3"
+strum = { version = "0.26.2", features = ["derive"] }
+thiserror = { workspace = true }
 
 # Bridge dependencies
 

bridges/relays/lib-substrate-relay/src/cli/bridge.rs

@@ -0,0 +1,110 @@
+// 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/>.
+
+//! Basic traits for exposing bridges in the CLI.
+
+use crate::{
+	equivocation::SubstrateEquivocationDetectionPipeline,
+	finality::SubstrateFinalitySyncPipeline,
+	messages_lane::{MessagesRelayLimits, SubstrateMessageLane},
+	parachains::SubstrateParachainsPipeline,
+};
+use pallet_bridge_parachains::{RelayBlockHash, RelayBlockHasher, RelayBlockNumber};
+use relay_substrate_client::{
+	Chain, ChainWithRuntimeVersion, ChainWithTransactions, Parachain, RelayChain,
+};
+
+/// Minimal bridge representation that can be used from the CLI.
+/// It connects a source chain to a target chain.
+pub trait CliBridgeBase: Sized {
+	/// The source chain.
+	type Source: Chain + ChainWithRuntimeVersion;
+	/// The target chain.
+	type Target: ChainWithTransactions + ChainWithRuntimeVersion;
+}
+
+/// Bridge representation that can be used from the CLI for relaying headers
+/// from a relay chain to a relay chain.
+pub trait RelayToRelayHeadersCliBridge: CliBridgeBase {
+	/// Finality proofs synchronization pipeline.
+	type Finality: SubstrateFinalitySyncPipeline<
+		SourceChain = Self::Source,
+		TargetChain = Self::Target,
+	>;
+}
+
+/// Convenience trait that adds bounds to `CliBridgeBase`.
+pub trait RelayToRelayEquivocationDetectionCliBridgeBase: CliBridgeBase {
+	/// The source chain with extra bounds.
+	type BoundedSource: ChainWithTransactions;
+}
+
+impl<T> RelayToRelayEquivocationDetectionCliBridgeBase for T
+where
+	T: CliBridgeBase,
+	T::Source: ChainWithTransactions,
+{
+	type BoundedSource = T::Source;
+}
+
+/// Bridge representation that can be used from the CLI for detecting equivocations
+/// in the headers synchronized from a relay chain to a relay chain.
+pub trait RelayToRelayEquivocationDetectionCliBridge:
+	RelayToRelayEquivocationDetectionCliBridgeBase
+{
+	/// Equivocation detection pipeline.
+	type Equivocation: SubstrateEquivocationDetectionPipeline<
+		SourceChain = Self::Source,
+		TargetChain = Self::Target,
+	>;
+}
+
+/// Bridge representation that can be used from the CLI for relaying headers
+/// from a parachain to a relay chain.
+pub trait ParachainToRelayHeadersCliBridge: CliBridgeBase
+where
+	Self::Source: Parachain,
+{
+	/// The `CliBridgeBase` type represents the parachain in this situation.
+	/// We need to add an extra type for the relay chain.
+	type SourceRelay: Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>
+		+ ChainWithRuntimeVersion
+		+ RelayChain;
+	/// Finality proofs synchronization pipeline (source parachain -> target).
+	type ParachainFinality: SubstrateParachainsPipeline<
+		SourceRelayChain = Self::SourceRelay,
+		SourceParachain = Self::Source,
+		TargetChain = Self::Target,
+	>;
+	/// Finality proofs synchronization pipeline (source relay chain -> target).
+	type RelayFinality: SubstrateFinalitySyncPipeline<
+		SourceChain = Self::SourceRelay,
+		TargetChain = Self::Target,
+	>;
+}
+
+/// Bridge representation that can be used from the CLI for relaying messages.
+pub trait MessagesCliBridge: CliBridgeBase {
+	/// The Source -> Destination messages synchronization pipeline.
+	type MessagesLane: SubstrateMessageLane<SourceChain = Self::Source, TargetChain = Self::Target>;
+
+	/// Optional messages delivery transaction limits that the messages relay is going
+	/// to use. If it returns `None`, limits are estimated using `TransactionPayment` API
+	/// at the target chain.
+	fn maybe_messages_limits() -> Option<MessagesRelayLimits> {
+		None
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/chain_schema.rs

@@ -0,0 +1,250 @@
+// Copyright 2019-2022 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/>.
+
+//! Primitives related to chain CLI options.
+
+use relay_substrate_client::{AccountKeyPairOf, ChainWithTransactions};
+use structopt::StructOpt;
+use strum::{EnumString, VariantNames};
+
+use relay_substrate_client::{ChainRuntimeVersion, ChainWithRuntimeVersion, SimpleRuntimeVersion};
+
+use crate::TransactionParams;
+
+#[doc = "Runtime version params."]
+#[derive(StructOpt, Debug, PartialEq, Eq, Clone, Copy, EnumString, VariantNames)]
+pub enum RuntimeVersionType {
+	/// Auto query version from chain
+	Auto,
+	/// Custom `spec_version` and `transaction_version`
+	Custom,
+	/// Read version from bundle dependencies directly.
+	Bundle,
+}
+
+/// Create chain-specific set of runtime version parameters.
+#[macro_export]
+macro_rules! declare_chain_runtime_version_params_cli_schema {
+	($chain:ident, $chain_prefix:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $chain " runtime version params."]
+			#[derive(StructOpt, Debug, PartialEq, Eq, Clone, Copy)]
+			pub struct [<$chain RuntimeVersionParams>] {
+				#[doc = "The type of runtime version for chain " $chain]
+				#[structopt(long, default_value = "Bundle")]
+				pub [<$chain_prefix _version_mode>]: RuntimeVersionType,
+				#[doc = "The custom sepc_version for chain " $chain]
+				#[structopt(long)]
+				pub [<$chain_prefix _spec_version>]: Option<u32>,
+				#[doc = "The custom transaction_version for chain " $chain]
+				#[structopt(long)]
+				pub [<$chain_prefix _transaction_version>]: Option<u32>,
+			}
+
+			impl [<$chain RuntimeVersionParams>] {
+				/// Converts self into `ChainRuntimeVersion`.
+				pub fn into_runtime_version(
+					self,
+					bundle_runtime_version: Option<SimpleRuntimeVersion>,
+				) -> anyhow::Result<ChainRuntimeVersion> {
+					Ok(match self.[<$chain_prefix _version_mode>] {
+						RuntimeVersionType::Auto => ChainRuntimeVersion::Auto,
+						RuntimeVersionType::Custom => {
+							let custom_spec_version = self.[<$chain_prefix _spec_version>]
+								.ok_or_else(|| anyhow::Error::msg(format!("The {}-spec-version is required when choose custom mode", stringify!($chain_prefix))))?;
+							let custom_transaction_version = self.[<$chain_prefix _transaction_version>]
+								.ok_or_else(|| anyhow::Error::msg(format!("The {}-transaction-version is required when choose custom mode", stringify!($chain_prefix))))?;
+							ChainRuntimeVersion::Custom(
+								SimpleRuntimeVersion {
+									spec_version: custom_spec_version,
+									transaction_version: custom_transaction_version
+								}
+							)
+						},
+						RuntimeVersionType::Bundle => match bundle_runtime_version {
+							Some(runtime_version) => ChainRuntimeVersion::Custom(runtime_version),
+							None => {
+								return Err(anyhow::format_err!("Cannot use bundled runtime version of {}: it is not known to the relay", stringify!($chain_prefix)));
+							}
+						},
+					})
+				}
+			}
+		}
+	};
+}
+
+/// Create chain-specific set of runtime version parameters.
+#[macro_export]
+macro_rules! declare_chain_connection_params_cli_schema {
+	($chain:ident, $chain_prefix:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $chain " connection params."]
+			#[derive(StructOpt, Debug, PartialEq, Eq, Clone)]
+			pub struct [<$chain ConnectionParams>] {
+				#[doc = "Connect to " $chain " node at given host."]
+				#[structopt(long, default_value = "127.0.0.1")]
+				pub [<$chain_prefix _host>]: String,
+				#[doc = "Connect to " $chain " node websocket server at given port."]
+				#[structopt(long, default_value = "9944")]
+				pub [<$chain_prefix _port>]: u16,
+				#[doc = "Use secure websocket connection."]
+				#[structopt(long)]
+				pub [<$chain_prefix _secure>]: bool,
+				#[doc = "Custom runtime version"]
+				#[structopt(flatten)]
+				pub [<$chain_prefix _runtime_version>]: [<$chain RuntimeVersionParams>],
+			}
+
+			impl [<$chain ConnectionParams>] {
+				/// Convert connection params into Substrate client.
+				#[allow(dead_code)]
+				pub async fn into_client<Chain: ChainWithRuntimeVersion>(
+					self,
+				) -> anyhow::Result<relay_substrate_client::Client<Chain>> {
+					let chain_runtime_version = self
+						.[<$chain_prefix _runtime_version>]
+						.into_runtime_version(Chain::RUNTIME_VERSION)?;
+					Ok(relay_substrate_client::Client::new(relay_substrate_client::ConnectionParams {
+						host: self.[<$chain_prefix _host>],
+						port: self.[<$chain_prefix _port>],
+						secure: self.[<$chain_prefix _secure>],
+						chain_runtime_version,
+					})
+					.await
+					)
+				}
+			}
+		}
+	};
+}
+
+/// Create chain-specific set of signing parameters.
+#[macro_export]
+macro_rules! declare_chain_signing_params_cli_schema {
+	($chain:ident, $chain_prefix:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $chain " signing params."]
+			#[derive(StructOpt, Debug, PartialEq, Eq, Clone)]
+			pub struct [<$chain SigningParams>] {
+				#[doc = "The SURI of secret key to use when transactions are submitted to the " $chain " node."]
+				#[structopt(long)]
+				pub [<$chain_prefix _signer>]: Option<String>,
+				#[doc = "The password for the SURI of secret key to use when transactions are submitted to the " $chain " node."]
+				#[structopt(long)]
+				pub [<$chain_prefix _signer_password>]: Option<String>,
+
+				#[doc = "Path to the file, that contains SURI of secret key to use when transactions are submitted to the " $chain " node. Can be overridden with " $chain_prefix "_signer option."]
+				#[structopt(long)]
+				pub [<$chain_prefix _signer_file>]: Option<std::path::PathBuf>,
+				#[doc = "Path to the file, that password for the SURI of secret key to use when transactions are submitted to the " $chain " node. Can be overridden with " $chain_prefix "_signer_password option."]
+				#[structopt(long)]
+				pub [<$chain_prefix _signer_password_file>]: Option<std::path::PathBuf>,
+
+				#[doc = "Transactions mortality period, in blocks. MUST be a power of two in [4; 65536] range. MAY NOT be larger than `BlockHashCount` parameter of the chain system module."]
+				#[structopt(long)]
+				pub [<$chain_prefix _transactions_mortality>]: Option<u32>,
+			}
+
+			impl [<$chain SigningParams>] {
+				/// Return transactions mortality.
+				#[allow(dead_code)]
+				pub fn transactions_mortality(&self) -> anyhow::Result<Option<u32>> {
+					self.[<$chain_prefix _transactions_mortality>]
+						.map(|transactions_mortality| {
+							if !(4..=65536).contains(&transactions_mortality)
+								|| !transactions_mortality.is_power_of_two()
+							{
+								Err(anyhow::format_err!(
+									"Transactions mortality {} is not a power of two in a [4; 65536] range",
+									transactions_mortality,
+								))
+							} else {
+								Ok(transactions_mortality)
+							}
+						})
+						.transpose()
+				}
+
+				/// Parse signing params into chain-specific KeyPair.
+				#[allow(dead_code)]
+				pub fn to_keypair<Chain: ChainWithTransactions>(&self) -> anyhow::Result<AccountKeyPairOf<Chain>> {
+					let suri = match (self.[<$chain_prefix _signer>].as_ref(), self.[<$chain_prefix _signer_file>].as_ref()) {
+						(Some(suri), _) => suri.to_owned(),
+						(None, Some(suri_file)) => std::fs::read_to_string(suri_file)
+							.map_err(|err| anyhow::format_err!(
+								"Failed to read SURI from file {:?}: {}",
+								suri_file,
+								err,
+							))?,
+						(None, None) => return Err(anyhow::format_err!(
+							"One of options must be specified: '{}' or '{}'",
+							stringify!([<$chain_prefix _signer>]),
+							stringify!([<$chain_prefix _signer_file>]),
+						)),
+					};
+
+					let suri_password = match (
+						self.[<$chain_prefix _signer_password>].as_ref(),
+						self.[<$chain_prefix _signer_password_file>].as_ref(),
+					) {
+						(Some(suri_password), _) => Some(suri_password.to_owned()),
+						(None, Some(suri_password_file)) => std::fs::read_to_string(suri_password_file)
+							.map(Some)
+							.map_err(|err| anyhow::format_err!(
+								"Failed to read SURI password from file {:?}: {}",
+								suri_password_file,
+								err,
+							))?,
+						_ => None,
+					};
+
+					use sp_core::crypto::Pair;
+
+					AccountKeyPairOf::<Chain>::from_string(
+						&suri,
+						suri_password.as_deref()
+					).map_err(|e| anyhow::format_err!("{:?}", e))
+				}
+
+				/// Return transaction parameters.
+				#[allow(dead_code)]
+				pub fn transaction_params<Chain: ChainWithTransactions>(
+					&self,
+				) -> anyhow::Result<TransactionParams<AccountKeyPairOf<Chain>>> {
+					Ok(TransactionParams {
+						mortality: self.transactions_mortality()?,
+						signer: self.to_keypair::<Chain>()?,
+					})
+				}
+			}
+		}
+	};
+}
+
+/// Create chain-specific set of configuration objects: connection parameters,
+/// signing parameters and bridge initialization parameters.
+#[macro_export]
+macro_rules! declare_chain_cli_schema {
+	($chain:ident, $chain_prefix:ident) => {
+		$crate::declare_chain_runtime_version_params_cli_schema!($chain, $chain_prefix);
+		$crate::declare_chain_connection_params_cli_schema!($chain, $chain_prefix);
+		$crate::declare_chain_signing_params_cli_schema!($chain, $chain_prefix);
+	};
+}
+
+declare_chain_cli_schema!(Source, source);
+declare_chain_cli_schema!(Target, target);

bridges/relays/lib-substrate-relay/src/cli/detect_equivocations.rs

@@ -0,0 +1,65 @@
+// Copyright 2019-2023 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/>.
+
+//! Primitives for exposing the equivocation detection functionality in the CLI.
+
+use crate::{
+	cli::{bridge::*, chain_schema::*, PrometheusParams},
+	equivocation,
+	equivocation::SubstrateEquivocationDetectionPipeline,
+};
+
+use async_trait::async_trait;
+use relay_substrate_client::ChainWithTransactions;
+use structopt::StructOpt;
+
+/// Start equivocation detection loop.
+#[derive(StructOpt)]
+pub struct DetectEquivocationsParams {
+	#[structopt(flatten)]
+	source: SourceConnectionParams,
+	#[structopt(flatten)]
+	source_sign: SourceSigningParams,
+	#[structopt(flatten)]
+	target: TargetConnectionParams,
+	#[structopt(flatten)]
+	prometheus_params: PrometheusParams,
+}
+
+/// Trait used for starting the equivocation detection loop between 2 chains.
+#[async_trait]
+pub trait EquivocationsDetector: RelayToRelayEquivocationDetectionCliBridge
+where
+	Self::Source: ChainWithTransactions,
+{
+	/// Start the equivocation detection loop.
+	async fn start(data: DetectEquivocationsParams) -> anyhow::Result<()> {
+		let source_client = data.source.into_client::<Self::Source>().await?;
+		Self::Equivocation::start_relay_guards(
+			&source_client,
+			source_client.can_start_version_guard(),
+		)
+		.await?;
+
+		equivocation::run::<Self::Equivocation>(
+			source_client,
+			data.target.into_client::<Self::Target>().await?,
+			data.source_sign.transaction_params::<Self::Source>()?,
+			data.prometheus_params.into_metrics_params()?,
+		)
+		.await
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/init_bridge.rs

@@ -0,0 +1,85 @@
+// 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/>.
+
+//! Primitives for exposing the bridge initialization functionality in the CLI.
+
+use async_trait::async_trait;
+use codec::Encode;
+
+use crate::{
+	cli::{bridge::CliBridgeBase, chain_schema::*},
+	finality_base::engine::Engine,
+};
+use bp_runtime::Chain as ChainBase;
+use relay_substrate_client::{AccountKeyPairOf, Chain, UnsignedTransaction};
+use sp_core::Pair;
+use structopt::StructOpt;
+
+/// Bridge initialization params.
+#[derive(StructOpt)]
+pub struct InitBridgeParams {
+	#[structopt(flatten)]
+	source: SourceConnectionParams,
+	#[structopt(flatten)]
+	target: TargetConnectionParams,
+	#[structopt(flatten)]
+	target_sign: TargetSigningParams,
+	/// Generates all required data, but does not submit extrinsic
+	#[structopt(long)]
+	dry_run: bool,
+}
+
+/// Trait used for bridge initializing.
+#[async_trait]
+pub trait BridgeInitializer: CliBridgeBase
+where
+	<Self::Target as ChainBase>::AccountId: From<<AccountKeyPairOf<Self::Target> as Pair>::Public>,
+{
+	/// The finality engine used by the source chain.
+	type Engine: Engine<Self::Source>;
+
+	/// Get the encoded call to init the bridge.
+	fn encode_init_bridge(
+		init_data: <Self::Engine as Engine<Self::Source>>::InitializationData,
+	) -> <Self::Target as Chain>::Call;
+
+	/// Initialize the bridge.
+	async fn init_bridge(data: InitBridgeParams) -> anyhow::Result<()> {
+		let source_client = data.source.into_client::<Self::Source>().await?;
+		let target_client = data.target.into_client::<Self::Target>().await?;
+		let target_sign = data.target_sign.to_keypair::<Self::Target>()?;
+		let dry_run = data.dry_run;
+
+		crate::finality::initialize::initialize::<Self::Engine, _, _, _>(
+			source_client,
+			target_client.clone(),
+			target_sign,
+			move |transaction_nonce, initialization_data| {
+				let call = Self::encode_init_bridge(initialization_data);
+				log::info!(
+					target: "bridge",
+					"Initialize bridge call encoded as hex string: {:?}",
+					format!("0x{}", hex::encode(call.encode()))
+				);
+				Ok(UnsignedTransaction::new(call.into(), transaction_nonce))
+			},
+			dry_run,
+		)
+		.await;
+
+		Ok(())
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/mod.rs

@@ -0,0 +1,192 @@
+// 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/>.
+
+//! Deal with CLI args of substrate-to-substrate relay.
+
+use codec::{Decode, Encode};
+use rbtag::BuildInfo;
+use structopt::StructOpt;
+use strum::{EnumString, VariantNames};
+
+use bp_messages::LaneId;
+
+pub mod bridge;
+pub mod chain_schema;
+pub mod detect_equivocations;
+pub mod init_bridge;
+pub mod relay_headers;
+pub mod relay_headers_and_messages;
+pub mod relay_messages;
+pub mod relay_parachains;
+
+/// The target that will be used when publishing logs related to this pallet.
+pub const LOG_TARGET: &str = "bridge";
+
+/// Lane id.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct HexLaneId(pub [u8; 4]);
+
+impl From<HexLaneId> for LaneId {
+	fn from(lane_id: HexLaneId) -> LaneId {
+		LaneId(lane_id.0)
+	}
+}
+
+impl std::str::FromStr for HexLaneId {
+	type Err = hex::FromHexError;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		let mut lane_id = [0u8; 4];
+		hex::decode_to_slice(s, &mut lane_id)?;
+		Ok(HexLaneId(lane_id))
+	}
+}
+
+/// Nicer formatting for raw bytes vectors.
+#[derive(Default, Encode, Decode, PartialEq, Eq)]
+pub struct HexBytes(pub Vec<u8>);
+
+impl std::str::FromStr for HexBytes {
+	type Err = hex::FromHexError;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		Ok(Self(hex::decode(s)?))
+	}
+}
+
+impl std::fmt::Debug for HexBytes {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		write!(fmt, "0x{self}")
+	}
+}
+
+impl std::fmt::Display for HexBytes {
+	fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+		write!(fmt, "{}", hex::encode(&self.0))
+	}
+}
+
+/// Prometheus metrics params.
+#[derive(Clone, Debug, PartialEq, StructOpt)]
+pub struct PrometheusParams {
+	/// Do not expose a Prometheus metric endpoint.
+	#[structopt(long)]
+	pub no_prometheus: bool,
+	/// Expose Prometheus endpoint at given interface.
+	#[structopt(long, default_value = "127.0.0.1")]
+	pub prometheus_host: String,
+	/// Expose Prometheus endpoint at given port.
+	#[structopt(long, default_value = "9616")]
+	pub prometheus_port: u16,
+}
+
+/// Struct to get git commit info and build time.
+#[derive(BuildInfo)]
+struct SubstrateRelayBuildInfo;
+
+impl SubstrateRelayBuildInfo {
+	/// Get git commit in form `<short-sha-(clean|dirty)>`.
+	pub fn get_git_commit() -> String {
+		// on gitlab we use images without git installed, so we can't use `rbtag` there
+		// locally we don't have `CI_*` env variables, so we can't rely on them
+		// => we are using `CI_*` env variables or else `rbtag`
+		let maybe_sha_from_ci = option_env!("CI_COMMIT_SHORT_SHA");
+		maybe_sha_from_ci
+			.map(|short_sha| {
+				// we assume that on CI the copy is always clean
+				format!("{short_sha}-clean")
+			})
+			.unwrap_or_else(|| SubstrateRelayBuildInfo.get_build_commit().into())
+	}
+}
+
+impl PrometheusParams {
+	/// Tries to convert CLI metrics params into metrics params, used by the relay.
+	pub fn into_metrics_params(self) -> anyhow::Result<relay_utils::metrics::MetricsParams> {
+		let metrics_address = if !self.no_prometheus {
+			Some(relay_utils::metrics::MetricsAddress {
+				host: self.prometheus_host,
+				port: self.prometheus_port,
+			})
+		} else {
+			None
+		};
+
+		let relay_version = option_env!("CARGO_PKG_VERSION").unwrap_or("unknown");
+		let relay_commit = SubstrateRelayBuildInfo::get_git_commit();
+		relay_utils::metrics::MetricsParams::new(
+			metrics_address,
+			relay_version.into(),
+			relay_commit,
+		)
+		.map_err(|e| anyhow::format_err!("{:?}", e))
+	}
+}
+
+/// Either explicit or maximal allowed value.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ExplicitOrMaximal<V> {
+	/// User has explicitly specified argument value.
+	Explicit(V),
+	/// Maximal allowed value for this argument.
+	Maximal,
+}
+
+impl<V: std::str::FromStr> std::str::FromStr for ExplicitOrMaximal<V>
+where
+	V::Err: std::fmt::Debug,
+{
+	type Err = String;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		if s.to_lowercase() == "max" {
+			return Ok(ExplicitOrMaximal::Maximal)
+		}
+
+		V::from_str(s)
+			.map(ExplicitOrMaximal::Explicit)
+			.map_err(|e| format!("Failed to parse '{e:?}'. Expected 'max' or explicit value"))
+	}
+}
+
+#[doc = "Runtime version params."]
+#[derive(StructOpt, Debug, PartialEq, Eq, Clone, Copy, EnumString, VariantNames)]
+pub enum RuntimeVersionType {
+	/// Auto query version from chain
+	Auto,
+	/// Custom `spec_version` and `transaction_version`
+	Custom,
+	/// Read version from bundle dependencies directly.
+	Bundle,
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn hex_bytes_display_matches_from_str_for_clap() {
+		// given
+		let hex = HexBytes(vec![1, 2, 3, 4]);
+		let display = format!("{hex}");
+
+		// when
+		let hex2: HexBytes = display.parse().unwrap();
+
+		// then
+		assert_eq!(hex.0, hex2.0);
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_headers.rs

@@ -0,0 +1,76 @@
+// 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/>.
+
+//! Primitives for exposing the headers relaying functionality in the CLI.
+
+use async_trait::async_trait;
+use structopt::StructOpt;
+
+use relay_utils::metrics::{GlobalMetrics, StandaloneMetric};
+
+use crate::{
+	cli::{bridge::*, chain_schema::*, PrometheusParams},
+	finality::SubstrateFinalitySyncPipeline,
+};
+
+/// Chain headers relaying params.
+#[derive(StructOpt)]
+pub struct RelayHeadersParams {
+	/// If passed, only mandatory headers (headers that are changing the GRANDPA authorities set)
+	/// are relayed.
+	#[structopt(long)]
+	only_mandatory_headers: bool,
+	#[structopt(flatten)]
+	source: SourceConnectionParams,
+	#[structopt(flatten)]
+	target: TargetConnectionParams,
+	#[structopt(flatten)]
+	target_sign: TargetSigningParams,
+	#[structopt(flatten)]
+	prometheus_params: PrometheusParams,
+}
+
+/// Trait used for relaying headers between 2 chains.
+#[async_trait]
+pub trait HeadersRelayer: RelayToRelayHeadersCliBridge {
+	/// Relay headers.
+	async fn relay_headers(data: RelayHeadersParams) -> anyhow::Result<()> {
+		let source_client = data.source.into_client::<Self::Source>().await?;
+		let target_client = data.target.into_client::<Self::Target>().await?;
+		let target_transactions_mortality = data.target_sign.target_transactions_mortality;
+		let target_sign = data.target_sign.to_keypair::<Self::Target>()?;
+
+		let metrics_params: relay_utils::metrics::MetricsParams =
+			data.prometheus_params.into_metrics_params()?;
+		GlobalMetrics::new()?.register_and_spawn(&metrics_params.registry)?;
+
+		let target_transactions_params = crate::TransactionParams {
+			signer: target_sign,
+			mortality: target_transactions_mortality,
+		};
+		Self::Finality::start_relay_guards(&target_client, target_client.can_start_version_guard())
+			.await?;
+
+		crate::finality::run::<Self::Finality>(
+			source_client,
+			target_client,
+			data.only_mandatory_headers,
+			target_transactions_params,
+			metrics_params,
+		)
+		.await
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_headers_and_messages/mod.rs

@@ -0,0 +1,484 @@
+// Copyright 2019-2022 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/>.
+
+//! Complex 2-ways headers+messages relays support.
+//!
+//! To add new complex relay between `ChainA` and `ChainB`, you must:
+//!
+//! 1) ensure that there's a `declare_chain_cli_schema!(...)` for both chains.
+//! 2) add `declare_chain_to_chain_bridge_schema!(...)` or
+//!    `declare_chain_to_parachain_bridge_schema` for the bridge.
+//! 3) declare a new struct for the added bridge and implement the `Full2WayBridge` trait for it.
+
+#[macro_use]
+pub mod parachain_to_parachain;
+#[macro_use]
+pub mod relay_to_relay;
+#[macro_use]
+pub mod relay_to_parachain;
+
+use async_trait::async_trait;
+use std::{marker::PhantomData, sync::Arc};
+use structopt::StructOpt;
+
+use futures::{FutureExt, TryFutureExt};
+
+use crate::{
+	cli::{bridge::MessagesCliBridge, HexLaneId, PrometheusParams},
+	messages_lane::{MessagesRelayLimits, MessagesRelayParams},
+	on_demand::OnDemandRelay,
+	TaggedAccount, TransactionParams,
+};
+use bp_messages::LaneId;
+use bp_runtime::BalanceOf;
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, Chain, ChainWithBalances, ChainWithMessages,
+	ChainWithRuntimeVersion, ChainWithTransactions, Client,
+};
+use relay_utils::metrics::MetricsParams;
+use sp_core::Pair;
+
+/// Parameters that have the same names across all bridges.
+#[derive(Debug, PartialEq, StructOpt)]
+pub struct HeadersAndMessagesSharedParams {
+	/// Hex-encoded lane identifiers that should be served by the complex relay.
+	#[structopt(long, default_value = "00000000")]
+	pub lane: Vec<HexLaneId>,
+	/// If passed, only mandatory headers (headers that are changing the GRANDPA authorities set)
+	/// are relayed.
+	#[structopt(long)]
+	pub only_mandatory_headers: bool,
+	#[structopt(flatten)]
+	/// Prometheus metrics params.
+	pub prometheus_params: PrometheusParams,
+}
+
+/// Bridge parameters, shared by all bridge types.
+pub struct Full2WayBridgeCommonParams<
+	Left: ChainWithTransactions + ChainWithRuntimeVersion,
+	Right: ChainWithTransactions + ChainWithRuntimeVersion,
+> {
+	/// Shared parameters.
+	pub shared: HeadersAndMessagesSharedParams,
+	/// Parameters of the left chain.
+	pub left: BridgeEndCommonParams<Left>,
+	/// Parameters of the right chain.
+	pub right: BridgeEndCommonParams<Right>,
+
+	/// Common metric parameters.
+	pub metrics_params: MetricsParams,
+}
+
+impl<
+		Left: ChainWithTransactions + ChainWithRuntimeVersion,
+		Right: ChainWithTransactions + ChainWithRuntimeVersion,
+	> Full2WayBridgeCommonParams<Left, Right>
+{
+	/// Creates new bridge parameters from its components.
+	pub fn new<L2R: MessagesCliBridge<Source = Left, Target = Right>>(
+		shared: HeadersAndMessagesSharedParams,
+		left: BridgeEndCommonParams<Left>,
+		right: BridgeEndCommonParams<Right>,
+	) -> anyhow::Result<Self> {
+		// Create metrics registry.
+		let metrics_params = shared.prometheus_params.clone().into_metrics_params()?;
+		let metrics_params = relay_utils::relay_metrics(metrics_params).into_params();
+
+		Ok(Self { shared, left, right, metrics_params })
+	}
+}
+
+/// Parameters that are associated with one side of the bridge.
+pub struct BridgeEndCommonParams<Chain: ChainWithTransactions + ChainWithRuntimeVersion> {
+	/// Chain client.
+	pub client: Client<Chain>,
+	/// Params used for sending transactions to the chain.
+	pub tx_params: TransactionParams<AccountKeyPairOf<Chain>>,
+	/// Accounts, which balances are exposed as metrics by the relay process.
+	pub accounts: Vec<TaggedAccount<AccountIdOf<Chain>>>,
+}
+
+/// All data of the bidirectional complex relay.
+pub struct FullBridge<
+	'a,
+	Source: ChainWithTransactions + ChainWithRuntimeVersion,
+	Target: ChainWithTransactions + ChainWithRuntimeVersion,
+	Bridge: MessagesCliBridge<Source = Source, Target = Target>,
+> {
+	source: &'a mut BridgeEndCommonParams<Source>,
+	target: &'a mut BridgeEndCommonParams<Target>,
+	metrics_params: &'a MetricsParams,
+	_phantom_data: PhantomData<Bridge>,
+}
+
+impl<
+		'a,
+		Source: ChainWithTransactions + ChainWithRuntimeVersion,
+		Target: ChainWithTransactions + ChainWithRuntimeVersion,
+		Bridge: MessagesCliBridge<Source = Source, Target = Target>,
+	> FullBridge<'a, Source, Target, Bridge>
+where
+	AccountIdOf<Source>: From<<AccountKeyPairOf<Source> as Pair>::Public>,
+	AccountIdOf<Target>: From<<AccountKeyPairOf<Target> as Pair>::Public>,
+	BalanceOf<Source>: TryFrom<BalanceOf<Target>> + Into<u128>,
+{
+	/// Construct complex relay given it components.
+	fn new(
+		source: &'a mut BridgeEndCommonParams<Source>,
+		target: &'a mut BridgeEndCommonParams<Target>,
+		metrics_params: &'a MetricsParams,
+	) -> Self {
+		Self { source, target, metrics_params, _phantom_data: Default::default() }
+	}
+
+	/// Returns message relay parameters.
+	fn messages_relay_params(
+		&self,
+		source_to_target_headers_relay: Arc<dyn OnDemandRelay<Source, Target>>,
+		target_to_source_headers_relay: Arc<dyn OnDemandRelay<Target, Source>>,
+		lane_id: LaneId,
+		maybe_limits: Option<MessagesRelayLimits>,
+	) -> MessagesRelayParams<Bridge::MessagesLane> {
+		MessagesRelayParams {
+			source_client: self.source.client.clone(),
+			source_transaction_params: self.source.tx_params.clone(),
+			target_client: self.target.client.clone(),
+			target_transaction_params: self.target.tx_params.clone(),
+			source_to_target_headers_relay: Some(source_to_target_headers_relay),
+			target_to_source_headers_relay: Some(target_to_source_headers_relay),
+			lane_id,
+			limits: maybe_limits,
+			metrics_params: self.metrics_params.clone().disable(),
+		}
+	}
+}
+
+/// Base portion of the bidirectional complex relay.
+///
+/// This main purpose of extracting this trait is that in different relays the implementation
+/// of `start_on_demand_headers_relayers` method will be different. But the number of
+/// implementations is limited to relay <> relay, parachain <> relay and parachain <> parachain.
+/// This trait allows us to reuse these implementations in different bridges.
+#[async_trait]
+pub trait Full2WayBridgeBase: Sized + Send + Sync {
+	/// The CLI params for the bridge.
+	type Params;
+	/// The left relay chain.
+	type Left: ChainWithTransactions + ChainWithRuntimeVersion;
+	/// The right destination chain (it can be a relay or a parachain).
+	type Right: ChainWithTransactions + ChainWithRuntimeVersion;
+
+	/// Reference to common relay parameters.
+	fn common(&self) -> &Full2WayBridgeCommonParams<Self::Left, Self::Right>;
+
+	/// Mutable reference to common relay parameters.
+	fn mut_common(&mut self) -> &mut Full2WayBridgeCommonParams<Self::Left, Self::Right>;
+
+	/// Start on-demand headers relays.
+	async fn start_on_demand_headers_relayers(
+		&mut self,
+	) -> anyhow::Result<(
+		Arc<dyn OnDemandRelay<Self::Left, Self::Right>>,
+		Arc<dyn OnDemandRelay<Self::Right, Self::Left>>,
+	)>;
+}
+
+/// Bidirectional complex relay.
+#[async_trait]
+pub trait Full2WayBridge: Sized + Sync
+where
+	AccountIdOf<Self::Left>: From<<AccountKeyPairOf<Self::Left> as Pair>::Public>,
+	AccountIdOf<Self::Right>: From<<AccountKeyPairOf<Self::Right> as Pair>::Public>,
+	BalanceOf<Self::Left>: TryFrom<BalanceOf<Self::Right>> + Into<u128>,
+	BalanceOf<Self::Right>: TryFrom<BalanceOf<Self::Left>> + Into<u128>,
+{
+	/// Base portion of the bidirectional complex relay.
+	type Base: Full2WayBridgeBase<Left = Self::Left, Right = Self::Right>;
+
+	/// The left relay chain.
+	type Left: ChainWithTransactions
+		+ ChainWithBalances
+		+ ChainWithMessages
+		+ ChainWithRuntimeVersion;
+	/// The right relay chain.
+	type Right: ChainWithTransactions
+		+ ChainWithBalances
+		+ ChainWithMessages
+		+ ChainWithRuntimeVersion;
+
+	/// Left to Right bridge.
+	type L2R: MessagesCliBridge<Source = Self::Left, Target = Self::Right>;
+	/// Right to Left bridge
+	type R2L: MessagesCliBridge<Source = Self::Right, Target = Self::Left>;
+
+	/// Construct new bridge.
+	fn new(params: <Self::Base as Full2WayBridgeBase>::Params) -> anyhow::Result<Self>;
+
+	/// Reference to the base relay portion.
+	fn base(&self) -> &Self::Base;
+
+	/// Mutable reference to the base relay portion.
+	fn mut_base(&mut self) -> &mut Self::Base;
+
+	/// Creates and returns Left to Right complex relay.
+	fn left_to_right(&mut self) -> FullBridge<Self::Left, Self::Right, Self::L2R> {
+		let common = self.mut_base().mut_common();
+		FullBridge::<_, _, Self::L2R>::new(
+			&mut common.left,
+			&mut common.right,
+			&common.metrics_params,
+		)
+	}
+
+	/// Creates and returns Right to Left complex relay.
+	fn right_to_left(&mut self) -> FullBridge<Self::Right, Self::Left, Self::R2L> {
+		let common = self.mut_base().mut_common();
+		FullBridge::<_, _, Self::R2L>::new(
+			&mut common.right,
+			&mut common.left,
+			&common.metrics_params,
+		)
+	}
+
+	/// Start complex relay.
+	async fn run(&mut self) -> anyhow::Result<()> {
+		// Register standalone metrics.
+		{
+			let common = self.mut_base().mut_common();
+			common.left.accounts.push(TaggedAccount::Messages {
+				id: common.left.tx_params.signer.public().into(),
+				bridged_chain: Self::Right::NAME.to_string(),
+			});
+			common.right.accounts.push(TaggedAccount::Messages {
+				id: common.right.tx_params.signer.public().into(),
+				bridged_chain: Self::Left::NAME.to_string(),
+			});
+		}
+
+		// start on-demand header relays
+		let (left_to_right_on_demand_headers, right_to_left_on_demand_headers) =
+			self.mut_base().start_on_demand_headers_relayers().await?;
+
+		// add balance-related metrics
+		let lanes = self
+			.base()
+			.common()
+			.shared
+			.lane
+			.iter()
+			.cloned()
+			.map(Into::into)
+			.collect::<Vec<_>>();
+		{
+			let common = self.mut_base().mut_common();
+			crate::messages_metrics::add_relay_balances_metrics::<_, Self::Right>(
+				common.left.client.clone(),
+				&common.metrics_params,
+				&common.left.accounts,
+				&lanes,
+			)
+			.await?;
+			crate::messages_metrics::add_relay_balances_metrics::<_, Self::Left>(
+				common.right.client.clone(),
+				&common.metrics_params,
+				&common.right.accounts,
+				&lanes,
+			)
+			.await?;
+		}
+
+		// Need 2x capacity since we consider both directions for each lane
+		let mut message_relays = Vec::with_capacity(lanes.len() * 2);
+		for lane in lanes {
+			let left_to_right_messages = crate::messages_lane::run::<
+				<Self::L2R as MessagesCliBridge>::MessagesLane,
+			>(self.left_to_right().messages_relay_params(
+				left_to_right_on_demand_headers.clone(),
+				right_to_left_on_demand_headers.clone(),
+				lane,
+				Self::L2R::maybe_messages_limits(),
+			))
+			.map_err(|e| anyhow::format_err!("{}", e))
+			.boxed();
+			message_relays.push(left_to_right_messages);
+
+			let right_to_left_messages = crate::messages_lane::run::<
+				<Self::R2L as MessagesCliBridge>::MessagesLane,
+			>(self.right_to_left().messages_relay_params(
+				right_to_left_on_demand_headers.clone(),
+				left_to_right_on_demand_headers.clone(),
+				lane,
+				Self::R2L::maybe_messages_limits(),
+			))
+			.map_err(|e| anyhow::format_err!("{}", e))
+			.boxed();
+			message_relays.push(right_to_left_messages);
+		}
+
+		relay_utils::relay_metrics(self.base().common().metrics_params.clone())
+			.expose()
+			.await
+			.map_err(|e| anyhow::format_err!("{}", e))?;
+
+		futures::future::select_all(message_relays).await.0
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::{cli::chain_schema::RuntimeVersionType, declare_chain_cli_schema};
+
+	use relay_substrate_client::{ChainRuntimeVersion, Parachain, SimpleRuntimeVersion};
+
+	#[test]
+	// We need `#[allow(dead_code)]` because some of the methods generated by the macros
+	// are not used.
+	#[allow(dead_code)]
+	fn should_parse_parachain_to_parachain_options() {
+		// Chains.
+		declare_chain_cli_schema!(Kusama, kusama);
+		declare_chain_cli_schema!(BridgeHubKusama, bridge_hub_kusama);
+		declare_chain_cli_schema!(Polkadot, polkadot);
+		declare_chain_cli_schema!(BridgeHubPolkadot, bridge_hub_polkadot);
+		// Means to override signers of different layer transactions.
+		declare_chain_cli_schema!(
+			KusamaHeadersToBridgeHubPolkadot,
+			kusama_headers_to_bridge_hub_polkadot
+		);
+		declare_chain_cli_schema!(
+			KusamaParachainsToBridgeHubPolkadot,
+			kusama_parachains_to_bridge_hub_polkadot
+		);
+		declare_chain_cli_schema!(
+			PolkadotHeadersToBridgeHubKusama,
+			polkadot_headers_to_bridge_hub_kusama
+		);
+		declare_chain_cli_schema!(
+			PolkadotParachainsToBridgeHubKusama,
+			polkadot_parachains_to_bridge_hub_kusama
+		);
+		// Bridges.
+		declare_parachain_to_parachain_bridge_schema!(
+			BridgeHubKusama,
+			Kusama,
+			BridgeHubPolkadot,
+			Polkadot
+		);
+
+		let res = BridgeHubKusamaBridgeHubPolkadotHeadersAndMessages::from_iter(vec![
+			"bridge-hub-kusama-bridge-hub-polkadot-headers-and-messages",
+			"--bridge-hub-kusama-host",
+			"bridge-hub-kusama-node-collator1",
+			"--bridge-hub-kusama-port",
+			"9944",
+			"--bridge-hub-kusama-signer",
+			"//Iden",
+			"--bridge-hub-kusama-transactions-mortality",
+			"64",
+			"--kusama-host",
+			"kusama-alice",
+			"--kusama-port",
+			"9944",
+			"--bridge-hub-polkadot-host",
+			"bridge-hub-polkadot-collator1",
+			"--bridge-hub-polkadot-port",
+			"9944",
+			"--bridge-hub-polkadot-signer",
+			"//George",
+			"--bridge-hub-polkadot-transactions-mortality",
+			"64",
+			"--polkadot-host",
+			"polkadot-alice",
+			"--polkadot-port",
+			"9944",
+			"--lane",
+			"00000000",
+			"--prometheus-host",
+			"0.0.0.0",
+		]);
+
+		// then
+		assert_eq!(
+			res,
+			BridgeHubKusamaBridgeHubPolkadotHeadersAndMessages {
+				shared: HeadersAndMessagesSharedParams {
+					lane: vec![HexLaneId([0x00, 0x00, 0x00, 0x00])],
+					only_mandatory_headers: false,
+					prometheus_params: PrometheusParams {
+						no_prometheus: false,
+						prometheus_host: "0.0.0.0".into(),
+						prometheus_port: 9616,
+					},
+				},
+				left: BridgeHubKusamaConnectionParams {
+					bridge_hub_kusama_host: "bridge-hub-kusama-node-collator1".into(),
+					bridge_hub_kusama_port: 9944,
+					bridge_hub_kusama_secure: false,
+					bridge_hub_kusama_runtime_version: BridgeHubKusamaRuntimeVersionParams {
+						bridge_hub_kusama_version_mode: RuntimeVersionType::Bundle,
+						bridge_hub_kusama_spec_version: None,
+						bridge_hub_kusama_transaction_version: None,
+					},
+				},
+				left_sign: BridgeHubKusamaSigningParams {
+					bridge_hub_kusama_signer: Some("//Iden".into()),
+					bridge_hub_kusama_signer_password: None,
+					bridge_hub_kusama_signer_file: None,
+					bridge_hub_kusama_signer_password_file: None,
+					bridge_hub_kusama_transactions_mortality: Some(64),
+				},
+				left_relay: KusamaConnectionParams {
+					kusama_host: "kusama-alice".into(),
+					kusama_port: 9944,
+					kusama_secure: false,
+					kusama_runtime_version: KusamaRuntimeVersionParams {
+						kusama_version_mode: RuntimeVersionType::Bundle,
+						kusama_spec_version: None,
+						kusama_transaction_version: None,
+					},
+				},
+				right: BridgeHubPolkadotConnectionParams {
+					bridge_hub_polkadot_host: "bridge-hub-polkadot-collator1".into(),
+					bridge_hub_polkadot_port: 9944,
+					bridge_hub_polkadot_secure: false,
+					bridge_hub_polkadot_runtime_version: BridgeHubPolkadotRuntimeVersionParams {
+						bridge_hub_polkadot_version_mode: RuntimeVersionType::Bundle,
+						bridge_hub_polkadot_spec_version: None,
+						bridge_hub_polkadot_transaction_version: None,
+					},
+				},
+				right_sign: BridgeHubPolkadotSigningParams {
+					bridge_hub_polkadot_signer: Some("//George".into()),
+					bridge_hub_polkadot_signer_password: None,
+					bridge_hub_polkadot_signer_file: None,
+					bridge_hub_polkadot_signer_password_file: None,
+					bridge_hub_polkadot_transactions_mortality: Some(64),
+				},
+				right_relay: PolkadotConnectionParams {
+					polkadot_host: "polkadot-alice".into(),
+					polkadot_port: 9944,
+					polkadot_secure: false,
+					polkadot_runtime_version: PolkadotRuntimeVersionParams {
+						polkadot_version_mode: RuntimeVersionType::Bundle,
+						polkadot_spec_version: None,
+						polkadot_transaction_version: None,
+					},
+				},
+			}
+		);
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_headers_and_messages/parachain_to_parachain.rs

@@ -0,0 +1,217 @@
+// Copyright 2019-2022 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 to parachain relayer CLI primitives.
+
+use async_trait::async_trait;
+use std::sync::Arc;
+
+use crate::{
+	cli::{
+		bridge::{CliBridgeBase, MessagesCliBridge, ParachainToRelayHeadersCliBridge},
+		relay_headers_and_messages::{Full2WayBridgeBase, Full2WayBridgeCommonParams},
+	},
+	finality::SubstrateFinalitySyncPipeline,
+	on_demand::{
+		headers::OnDemandHeadersRelay, parachains::OnDemandParachainsRelay, OnDemandRelay,
+	},
+};
+use bp_polkadot_core::parachains::ParaHash;
+use pallet_bridge_parachains::{RelayBlockHash, RelayBlockHasher, RelayBlockNumber};
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, Chain, ChainWithRuntimeVersion, ChainWithTransactions, Client,
+	Parachain,
+};
+use sp_core::Pair;
+
+/// A base relay between two parachain from different consensus systems.
+///
+/// Such relay starts 2 messages relay. It also starts 2 on-demand header relays and 2 on-demand
+/// parachain heads relay.
+pub struct ParachainToParachainBridge<
+	L2R: MessagesCliBridge + ParachainToRelayHeadersCliBridge,
+	R2L: MessagesCliBridge + ParachainToRelayHeadersCliBridge,
+> where
+	<L2R as CliBridgeBase>::Source: Parachain,
+	<R2L as CliBridgeBase>::Source: Parachain,
+{
+	/// Parameters that are shared by all bridge types.
+	pub common:
+		Full2WayBridgeCommonParams<<R2L as CliBridgeBase>::Target, <L2R as CliBridgeBase>::Target>,
+	/// Client of the left relay chain.
+	pub left_relay: Client<<L2R as ParachainToRelayHeadersCliBridge>::SourceRelay>,
+	/// Client of the right relay chain.
+	pub right_relay: Client<<R2L as ParachainToRelayHeadersCliBridge>::SourceRelay>,
+}
+
+/// Create set of configuration objects specific to parachain-to-parachain relayer.
+#[macro_export]
+macro_rules! declare_parachain_to_parachain_bridge_schema {
+	// left-parachain, relay-chain-of-left-parachain, right-parachain, relay-chain-of-right-parachain
+	($left_parachain:ident, $left_chain:ident, $right_parachain:ident, $right_chain:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $left_parachain ", " $left_chain ", " $right_parachain " and " $right_chain " headers+parachains+messages relay params."]
+			#[derive(Debug, PartialEq, StructOpt)]
+			pub struct [<$left_parachain $right_parachain HeadersAndMessages>] {
+				// shared parameters
+				#[structopt(flatten)]
+				shared: HeadersAndMessagesSharedParams,
+
+				#[structopt(flatten)]
+				left: [<$left_parachain ConnectionParams>],
+				// default signer, which is always used to sign messages relay transactions on the left chain
+				#[structopt(flatten)]
+				left_sign: [<$left_parachain SigningParams>],
+
+				#[structopt(flatten)]
+				left_relay: [<$left_chain ConnectionParams>],
+
+				#[structopt(flatten)]
+				right: [<$right_parachain ConnectionParams>],
+				// default signer, which is always used to sign messages relay transactions on the right chain
+				#[structopt(flatten)]
+				right_sign: [<$right_parachain SigningParams>],
+
+				#[structopt(flatten)]
+				right_relay: [<$right_chain ConnectionParams>],
+			}
+
+			impl [<$left_parachain $right_parachain HeadersAndMessages>] {
+				async fn into_bridge<
+					Left: ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+					LeftRelay: ChainWithRuntimeVersion,
+					Right: ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+					RightRelay: ChainWithRuntimeVersion,
+					L2R: $crate::cli::bridge::CliBridgeBase<Source = Left, Target = Right>
+						+ MessagesCliBridge
+						+ $crate::cli::bridge::ParachainToRelayHeadersCliBridge<SourceRelay = LeftRelay>,
+					R2L: $crate::cli::bridge::CliBridgeBase<Source = Right, Target = Left>
+						+ MessagesCliBridge
+						+ $crate::cli::bridge::ParachainToRelayHeadersCliBridge<SourceRelay = RightRelay>,
+				>(
+					self,
+				) -> anyhow::Result<$crate::cli::relay_headers_and_messages::parachain_to_parachain::ParachainToParachainBridge<L2R, R2L>> {
+					Ok($crate::cli::relay_headers_and_messages::parachain_to_parachain::ParachainToParachainBridge {
+						common: Full2WayBridgeCommonParams::new::<L2R>(
+							self.shared,
+							BridgeEndCommonParams {
+								client: self.left.into_client::<Left>().await?,
+								tx_params: self.left_sign.transaction_params::<Left>()?,
+								accounts: vec![],
+							},
+							BridgeEndCommonParams {
+								client: self.right.into_client::<Right>().await?,
+								tx_params: self.right_sign.transaction_params::<Right>()?,
+								accounts: vec![],
+							},
+						)?,
+						left_relay: self.left_relay.into_client::<LeftRelay>().await?,
+						right_relay: self.right_relay.into_client::<RightRelay>().await?,
+					})
+				}
+			}
+		}
+	};
+}
+
+#[async_trait]
+impl<
+		Left: Chain<Hash = ParaHash> + ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+		Right: Chain<Hash = ParaHash> + ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+		LeftRelay: Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>
+			+ ChainWithRuntimeVersion,
+		RightRelay: Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>
+			+ ChainWithRuntimeVersion,
+		L2R: CliBridgeBase<Source = Left, Target = Right>
+			+ MessagesCliBridge
+			+ ParachainToRelayHeadersCliBridge<SourceRelay = LeftRelay>,
+		R2L: CliBridgeBase<Source = Right, Target = Left>
+			+ MessagesCliBridge
+			+ ParachainToRelayHeadersCliBridge<SourceRelay = RightRelay>,
+	> Full2WayBridgeBase for ParachainToParachainBridge<L2R, R2L>
+where
+	AccountIdOf<Left>: From<<AccountKeyPairOf<Left> as Pair>::Public>,
+	AccountIdOf<Right>: From<<AccountKeyPairOf<Right> as Pair>::Public>,
+{
+	type Params = ParachainToParachainBridge<L2R, R2L>;
+	type Left = Left;
+	type Right = Right;
+
+	fn common(&self) -> &Full2WayBridgeCommonParams<Left, Right> {
+		&self.common
+	}
+
+	fn mut_common(&mut self) -> &mut Full2WayBridgeCommonParams<Self::Left, Self::Right> {
+		&mut self.common
+	}
+
+	async fn start_on_demand_headers_relayers(
+		&mut self,
+	) -> anyhow::Result<(
+		Arc<dyn OnDemandRelay<Self::Left, Self::Right>>,
+		Arc<dyn OnDemandRelay<Self::Right, Self::Left>>,
+	)> {
+		<L2R as ParachainToRelayHeadersCliBridge>::RelayFinality::start_relay_guards(
+			&self.common.right.client,
+			self.common.right.client.can_start_version_guard(),
+		)
+		.await?;
+		<R2L as ParachainToRelayHeadersCliBridge>::RelayFinality::start_relay_guards(
+			&self.common.left.client,
+			self.common.left.client.can_start_version_guard(),
+		)
+		.await?;
+
+		let left_relay_to_right_on_demand_headers =
+			OnDemandHeadersRelay::<<L2R as ParachainToRelayHeadersCliBridge>::RelayFinality>::new(
+				self.left_relay.clone(),
+				self.common.right.client.clone(),
+				self.common.right.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				Some(self.common.metrics_params.clone()),
+			);
+		let right_relay_to_left_on_demand_headers =
+			OnDemandHeadersRelay::<<R2L as ParachainToRelayHeadersCliBridge>::RelayFinality>::new(
+				self.right_relay.clone(),
+				self.common.left.client.clone(),
+				self.common.left.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				Some(self.common.metrics_params.clone()),
+			);
+
+		let left_to_right_on_demand_parachains = OnDemandParachainsRelay::<
+			<L2R as ParachainToRelayHeadersCliBridge>::ParachainFinality,
+		>::new(
+			self.left_relay.clone(),
+			self.common.right.client.clone(),
+			self.common.right.tx_params.clone(),
+			Arc::new(left_relay_to_right_on_demand_headers),
+		);
+		let right_to_left_on_demand_parachains = OnDemandParachainsRelay::<
+			<R2L as ParachainToRelayHeadersCliBridge>::ParachainFinality,
+		>::new(
+			self.right_relay.clone(),
+			self.common.left.client.clone(),
+			self.common.left.tx_params.clone(),
+			Arc::new(right_relay_to_left_on_demand_headers),
+		);
+
+		Ok((
+			Arc::new(left_to_right_on_demand_parachains),
+			Arc::new(right_to_left_on_demand_parachains),
+		))
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_headers_and_messages/relay_to_parachain.rs

@@ -0,0 +1,199 @@
+// Copyright 2019-2022 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/>.
+
+//! Relay chain to parachain relayer CLI primitives.
+
+use async_trait::async_trait;
+use std::sync::Arc;
+
+use crate::{
+	cli::{
+		bridge::{
+			CliBridgeBase, MessagesCliBridge, ParachainToRelayHeadersCliBridge,
+			RelayToRelayHeadersCliBridge,
+		},
+		relay_headers_and_messages::{Full2WayBridgeBase, Full2WayBridgeCommonParams},
+	},
+	finality::SubstrateFinalitySyncPipeline,
+	on_demand::{
+		headers::OnDemandHeadersRelay, parachains::OnDemandParachainsRelay, OnDemandRelay,
+	},
+};
+use bp_polkadot_core::parachains::ParaHash;
+use pallet_bridge_parachains::{RelayBlockHash, RelayBlockHasher, RelayBlockNumber};
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, Chain, ChainWithRuntimeVersion, ChainWithTransactions, Client,
+	Parachain,
+};
+use sp_core::Pair;
+
+/// A base relay between standalone (relay) chain and a parachain from another consensus system.
+///
+/// Such relay starts 2 messages relay. It also starts 2 on-demand header relays and 1 on-demand
+/// parachain heads relay.
+pub struct RelayToParachainBridge<
+	L2R: MessagesCliBridge + RelayToRelayHeadersCliBridge,
+	R2L: MessagesCliBridge + ParachainToRelayHeadersCliBridge,
+> where
+	<R2L as CliBridgeBase>::Source: Parachain,
+{
+	/// Parameters that are shared by all bridge types.
+	pub common:
+		Full2WayBridgeCommonParams<<R2L as CliBridgeBase>::Target, <L2R as CliBridgeBase>::Target>,
+	/// Client of the right relay chain.
+	pub right_relay: Client<<R2L as ParachainToRelayHeadersCliBridge>::SourceRelay>,
+}
+
+/// Create set of configuration objects specific to relay-to-parachain relayer.
+#[macro_export]
+macro_rules! declare_relay_to_parachain_bridge_schema {
+	// chain, parachain, relay-chain-of-parachain
+	($left_chain:ident, $right_parachain:ident, $right_chain:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $left_chain ", " $right_parachain " and " $right_chain " headers+parachains+messages relay params."]
+			#[derive(Debug, PartialEq, StructOpt)]
+			pub struct [<$left_chain $right_parachain HeadersAndMessages>] {
+				// shared parameters
+				#[structopt(flatten)]
+				shared: HeadersAndMessagesSharedParams,
+
+				#[structopt(flatten)]
+				left: [<$left_chain ConnectionParams>],
+				// default signer, which is always used to sign messages relay transactions on the left chain
+				#[structopt(flatten)]
+				left_sign: [<$left_chain SigningParams>],
+
+				#[structopt(flatten)]
+				right: [<$right_parachain ConnectionParams>],
+				// default signer, which is always used to sign messages relay transactions on the right chain
+				#[structopt(flatten)]
+				right_sign: [<$right_parachain SigningParams>],
+
+				#[structopt(flatten)]
+				right_relay: [<$right_chain ConnectionParams>],
+			}
+
+			impl [<$left_chain $right_parachain HeadersAndMessages>] {
+				async fn into_bridge<
+					Left: ChainWithTransactions + ChainWithRuntimeVersion,
+					Right: ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+					RightRelay: ChainWithRuntimeVersion,
+					L2R: CliBridgeBase<Source = Left, Target = Right> + MessagesCliBridge + RelayToRelayHeadersCliBridge,
+					R2L: CliBridgeBase<Source = Right, Target = Left>
+						+ MessagesCliBridge
+						+ ParachainToRelayHeadersCliBridge<SourceRelay = RightRelay>,
+				>(
+					self,
+				) -> anyhow::Result<RelayToParachainBridge<L2R, R2L>> {
+					Ok(RelayToParachainBridge {
+						common: Full2WayBridgeCommonParams::new::<L2R>(
+							self.shared,
+							BridgeEndCommonParams {
+								client: self.left.into_client::<Left>().await?,
+								tx_params: self.left_sign.transaction_params::<Left>()?,
+								accounts: vec![],
+							},
+							BridgeEndCommonParams {
+								client: self.right.into_client::<Right>().await?,
+								tx_params: self.right_sign.transaction_params::<Right>()?,
+								accounts: vec![],
+							},
+						)?,
+						right_relay: self.right_relay.into_client::<RightRelay>().await?,
+					})
+				}
+			}
+		}
+	};
+}
+
+#[async_trait]
+impl<
+		Left: ChainWithTransactions + ChainWithRuntimeVersion,
+		Right: Chain<Hash = ParaHash> + ChainWithTransactions + ChainWithRuntimeVersion + Parachain,
+		RightRelay: Chain<BlockNumber = RelayBlockNumber, Hash = RelayBlockHash, Hasher = RelayBlockHasher>
+			+ ChainWithRuntimeVersion,
+		L2R: CliBridgeBase<Source = Left, Target = Right>
+			+ MessagesCliBridge
+			+ RelayToRelayHeadersCliBridge,
+		R2L: CliBridgeBase<Source = Right, Target = Left>
+			+ MessagesCliBridge
+			+ ParachainToRelayHeadersCliBridge<SourceRelay = RightRelay>,
+	> Full2WayBridgeBase for RelayToParachainBridge<L2R, R2L>
+where
+	AccountIdOf<Left>: From<<AccountKeyPairOf<Left> as Pair>::Public>,
+	AccountIdOf<Right>: From<<AccountKeyPairOf<Right> as Pair>::Public>,
+{
+	type Params = RelayToParachainBridge<L2R, R2L>;
+	type Left = Left;
+	type Right = Right;
+
+	fn common(&self) -> &Full2WayBridgeCommonParams<Left, Right> {
+		&self.common
+	}
+
+	fn mut_common(&mut self) -> &mut Full2WayBridgeCommonParams<Self::Left, Self::Right> {
+		&mut self.common
+	}
+
+	async fn start_on_demand_headers_relayers(
+		&mut self,
+	) -> anyhow::Result<(
+		Arc<dyn OnDemandRelay<Self::Left, Self::Right>>,
+		Arc<dyn OnDemandRelay<Self::Right, Self::Left>>,
+	)> {
+		<L2R as RelayToRelayHeadersCliBridge>::Finality::start_relay_guards(
+			&self.common.right.client,
+			self.common.right.client.can_start_version_guard(),
+		)
+		.await?;
+		<R2L as ParachainToRelayHeadersCliBridge>::RelayFinality::start_relay_guards(
+			&self.common.left.client,
+			self.common.left.client.can_start_version_guard(),
+		)
+		.await?;
+
+		let left_to_right_on_demand_headers =
+			OnDemandHeadersRelay::<<L2R as RelayToRelayHeadersCliBridge>::Finality>::new(
+				self.common.left.client.clone(),
+				self.common.right.client.clone(),
+				self.common.right.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				None,
+			);
+		let right_relay_to_left_on_demand_headers =
+			OnDemandHeadersRelay::<<R2L as ParachainToRelayHeadersCliBridge>::RelayFinality>::new(
+				self.right_relay.clone(),
+				self.common.left.client.clone(),
+				self.common.left.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				Some(self.common.metrics_params.clone()),
+			);
+		let right_to_left_on_demand_parachains = OnDemandParachainsRelay::<
+			<R2L as ParachainToRelayHeadersCliBridge>::ParachainFinality,
+		>::new(
+			self.right_relay.clone(),
+			self.common.left.client.clone(),
+			self.common.left.tx_params.clone(),
+			Arc::new(right_relay_to_left_on_demand_headers),
+		);
+
+		Ok((
+			Arc::new(left_to_right_on_demand_headers),
+			Arc::new(right_to_left_on_demand_parachains),
+		))
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_headers_and_messages/relay_to_relay.rs

@@ -0,0 +1,169 @@
+// Copyright 2019-2022 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/>.
+
+// we don't have any relay/standalone <> relay/standalone chain bridges, but we may need it in a
+// future
+#![allow(unused_macros)]
+
+//! Relay chain to Relay chain relayer CLI primitives.
+
+use async_trait::async_trait;
+use std::sync::Arc;
+
+use crate::{
+	cli::{
+		bridge::{CliBridgeBase, MessagesCliBridge, RelayToRelayHeadersCliBridge},
+		relay_headers_and_messages::{Full2WayBridgeBase, Full2WayBridgeCommonParams},
+	},
+	finality::SubstrateFinalitySyncPipeline,
+	on_demand::{headers::OnDemandHeadersRelay, OnDemandRelay},
+};
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, ChainWithRuntimeVersion, ChainWithTransactions,
+};
+use sp_core::Pair;
+
+/// A base relay between two standalone (relay) chains.
+///
+/// Such relay starts 2 messages relay and 2 on-demand header relays.
+pub struct RelayToRelayBridge<
+	L2R: MessagesCliBridge + RelayToRelayHeadersCliBridge,
+	R2L: MessagesCliBridge + RelayToRelayHeadersCliBridge,
+> {
+	/// Parameters that are shared by all bridge types.
+	pub common:
+		Full2WayBridgeCommonParams<<R2L as CliBridgeBase>::Target, <L2R as CliBridgeBase>::Target>,
+}
+
+/// Create set of configuration objects specific to relay-to-relay relayer.
+macro_rules! declare_relay_to_relay_bridge_schema {
+	($left_chain:ident, $right_chain:ident) => {
+		bp_runtime::paste::item! {
+			#[doc = $left_chain " and " $right_chain " headers+messages relay params."]
+			#[derive(Debug, PartialEq, StructOpt)]
+			pub struct [<$left_chain $right_chain HeadersAndMessages>] {
+				#[structopt(flatten)]
+				shared: HeadersAndMessagesSharedParams,
+
+				#[structopt(flatten)]
+				left: [<$left_chain ConnectionParams>],
+				// default signer, which is always used to sign messages relay transactions on the left chain
+				#[structopt(flatten)]
+				left_sign: [<$left_chain SigningParams>],
+
+				#[structopt(flatten)]
+				right: [<$right_chain ConnectionParams>],
+				#[structopt(flatten)]
+				// default signer, which is always used to sign messages relay transactions on the right chain
+				right_sign: [<$right_chain SigningParams>],
+			}
+
+			impl [<$left_chain $right_chain HeadersAndMessages>] {
+				async fn into_bridge<
+					Left: ChainWithTransactions + CliChain,
+					Right: ChainWithTransactions + CliChain,
+					L2R: CliBridgeBase<Source = Left, Target = Right> + MessagesCliBridge + RelayToRelayHeadersCliBridge,
+					R2L: CliBridgeBase<Source = Right, Target = Left> + MessagesCliBridge + RelayToRelayHeadersCliBridge,
+				>(
+					self,
+				) -> anyhow::Result<RelayToRelayBridge<L2R, R2L>> {
+					Ok(RelayToRelayBridge {
+						common: Full2WayBridgeCommonParams::new::<L2R>(
+							self.shared,
+							BridgeEndCommonParams {
+								client: self.left.into_client::<Left>().await?,
+								tx_params: self.left_sign.transaction_params::<Left>()?,
+								accounts: vec![],
+							},
+							BridgeEndCommonParams {
+								client: self.right.into_client::<Right>().await?,
+								tx_params: self.right_sign.transaction_params::<Right>()?,
+								accounts: vec![],
+							},
+						)?,
+						right_to_left_transaction_params: self.left_sign.transaction_params::<Left>(),
+						left_to_right_transaction_params: self.right_sign.transaction_params::<Right>(),
+					})
+				}
+			}
+		}
+	};
+}
+
+#[async_trait]
+impl<
+		Left: ChainWithTransactions + ChainWithRuntimeVersion,
+		Right: ChainWithTransactions + ChainWithRuntimeVersion,
+		L2R: CliBridgeBase<Source = Left, Target = Right>
+			+ MessagesCliBridge
+			+ RelayToRelayHeadersCliBridge,
+		R2L: CliBridgeBase<Source = Right, Target = Left>
+			+ MessagesCliBridge
+			+ RelayToRelayHeadersCliBridge,
+	> Full2WayBridgeBase for RelayToRelayBridge<L2R, R2L>
+where
+	AccountIdOf<Left>: From<<AccountKeyPairOf<Left> as Pair>::Public>,
+	AccountIdOf<Right>: From<<AccountKeyPairOf<Right> as Pair>::Public>,
+{
+	type Params = RelayToRelayBridge<L2R, R2L>;
+	type Left = Left;
+	type Right = Right;
+
+	fn common(&self) -> &Full2WayBridgeCommonParams<Left, Right> {
+		&self.common
+	}
+
+	fn mut_common(&mut self) -> &mut Full2WayBridgeCommonParams<Self::Left, Self::Right> {
+		&mut self.common
+	}
+
+	async fn start_on_demand_headers_relayers(
+		&mut self,
+	) -> anyhow::Result<(
+		Arc<dyn OnDemandRelay<Self::Left, Self::Right>>,
+		Arc<dyn OnDemandRelay<Self::Right, Self::Left>>,
+	)> {
+		<L2R as RelayToRelayHeadersCliBridge>::Finality::start_relay_guards(
+			&self.common.right.client,
+			self.common.right.client.can_start_version_guard(),
+		)
+		.await?;
+		<R2L as RelayToRelayHeadersCliBridge>::Finality::start_relay_guards(
+			&self.common.left.client,
+			self.common.left.client.can_start_version_guard(),
+		)
+		.await?;
+
+		let left_to_right_on_demand_headers =
+			OnDemandHeadersRelay::<<L2R as RelayToRelayHeadersCliBridge>::Finality>::new(
+				self.common.left.client.clone(),
+				self.common.right.client.clone(),
+				self.common.right.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				None,
+			);
+		let right_to_left_on_demand_headers =
+			OnDemandHeadersRelay::<<R2L as RelayToRelayHeadersCliBridge>::Finality>::new(
+				self.common.right.client.clone(),
+				self.common.left.client.clone(),
+				self.common.left.tx_params.clone(),
+				self.common.shared.only_mandatory_headers,
+				None,
+			);
+
+		Ok((Arc::new(left_to_right_on_demand_headers), Arc::new(right_to_left_on_demand_headers)))
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_messages.rs

@@ -0,0 +1,89 @@
+// 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/>.
+
+//! Primitives for exposing the messages relaying functionality in the CLI.
+
+use crate::{
+	cli::{bridge::*, chain_schema::*, HexLaneId, PrometheusParams},
+	messages_lane::MessagesRelayParams,
+	TransactionParams,
+};
+
+use async_trait::async_trait;
+use sp_core::Pair;
+use structopt::StructOpt;
+
+use relay_substrate_client::{
+	AccountIdOf, AccountKeyPairOf, BalanceOf, ChainWithRuntimeVersion, ChainWithTransactions,
+};
+
+/// Messages relaying params.
+#[derive(StructOpt)]
+pub struct RelayMessagesParams {
+	/// Hex-encoded lane id that should be served by the relay. Defaults to `00000000`.
+	#[structopt(long, default_value = "00000000")]
+	lane: HexLaneId,
+	#[structopt(flatten)]
+	source: SourceConnectionParams,
+	#[structopt(flatten)]
+	source_sign: SourceSigningParams,
+	#[structopt(flatten)]
+	target: TargetConnectionParams,
+	#[structopt(flatten)]
+	target_sign: TargetSigningParams,
+	#[structopt(flatten)]
+	prometheus_params: PrometheusParams,
+}
+
+/// Trait used for relaying messages between 2 chains.
+#[async_trait]
+pub trait MessagesRelayer: MessagesCliBridge
+where
+	Self::Source: ChainWithTransactions + ChainWithRuntimeVersion,
+	AccountIdOf<Self::Source>: From<<AccountKeyPairOf<Self::Source> as Pair>::Public>,
+	AccountIdOf<Self::Target>: From<<AccountKeyPairOf<Self::Target> as Pair>::Public>,
+	BalanceOf<Self::Source>: TryFrom<BalanceOf<Self::Target>>,
+{
+	/// Start relaying messages.
+	async fn relay_messages(data: RelayMessagesParams) -> anyhow::Result<()> {
+		let source_client = data.source.into_client::<Self::Source>().await?;
+		let source_sign = data.source_sign.to_keypair::<Self::Source>()?;
+		let source_transactions_mortality = data.source_sign.transactions_mortality()?;
+		let target_client = data.target.into_client::<Self::Target>().await?;
+		let target_sign = data.target_sign.to_keypair::<Self::Target>()?;
+		let target_transactions_mortality = data.target_sign.transactions_mortality()?;
+
+		crate::messages_lane::run::<Self::MessagesLane>(MessagesRelayParams {
+			source_client,
+			source_transaction_params: TransactionParams {
+				signer: source_sign,
+				mortality: source_transactions_mortality,
+			},
+			target_client,
+			target_transaction_params: TransactionParams {
+				signer: target_sign,
+				mortality: target_transactions_mortality,
+			},
+			source_to_target_headers_relay: None,
+			target_to_source_headers_relay: None,
+			lane_id: data.lane.into(),
+			limits: Self::maybe_messages_limits(),
+			metrics_params: data.prometheus_params.into_metrics_params()?,
+		})
+		.await
+		.map_err(|e| anyhow::format_err!("{}", e))
+	}
+}

bridges/relays/lib-substrate-relay/src/cli/relay_parachains.rs

@@ -0,0 +1,91 @@
+// 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/>.
+
+//! Primitives for exposing the parachains finality relaying functionality in the CLI.
+
+use async_std::sync::Mutex;
+use async_trait::async_trait;
+use parachains_relay::parachains_loop::{AvailableHeader, SourceClient, TargetClient};
+use relay_substrate_client::Parachain;
+use relay_utils::metrics::{GlobalMetrics, StandaloneMetric};
+use std::sync::Arc;
+use structopt::StructOpt;
+
+use crate::{
+	cli::{
+		bridge::{CliBridgeBase, ParachainToRelayHeadersCliBridge},
+		chain_schema::*,
+		PrometheusParams,
+	},
+	parachains::{source::ParachainsSource, target::ParachainsTarget, ParachainsPipelineAdapter},
+	TransactionParams,
+};
+
+/// Parachains heads relaying params.
+#[derive(StructOpt)]
+pub struct RelayParachainsParams {
+	#[structopt(flatten)]
+	source: SourceConnectionParams,
+	#[structopt(flatten)]
+	target: TargetConnectionParams,
+	#[structopt(flatten)]
+	target_sign: TargetSigningParams,
+	#[structopt(flatten)]
+	prometheus_params: PrometheusParams,
+}
+
+/// Trait used for relaying parachains finality between 2 chains.
+#[async_trait]
+pub trait ParachainsRelayer: ParachainToRelayHeadersCliBridge
+where
+	ParachainsSource<Self::ParachainFinality>:
+		SourceClient<ParachainsPipelineAdapter<Self::ParachainFinality>>,
+	ParachainsTarget<Self::ParachainFinality>:
+		TargetClient<ParachainsPipelineAdapter<Self::ParachainFinality>>,
+	<Self as CliBridgeBase>::Source: Parachain,
+{
+	/// Start relaying parachains finality.
+	async fn relay_parachains(data: RelayParachainsParams) -> anyhow::Result<()> {
+		let source_client = data.source.into_client::<Self::SourceRelay>().await?;
+		let source_client = ParachainsSource::<Self::ParachainFinality>::new(
+			source_client,
+			Arc::new(Mutex::new(AvailableHeader::Missing)),
+		);
+
+		let target_transaction_params = TransactionParams {
+			signer: data.target_sign.to_keypair::<Self::Target>()?,
+			mortality: data.target_sign.target_transactions_mortality,
+		};
+		let target_client = data.target.into_client::<Self::Target>().await?;
+		let target_client = ParachainsTarget::<Self::ParachainFinality>::new(
+			target_client.clone(),
+			target_transaction_params,
+		);
+
+		let metrics_params: relay_utils::metrics::MetricsParams =
+			data.prometheus_params.into_metrics_params()?;
+		GlobalMetrics::new()?.register_and_spawn(&metrics_params.registry)?;
+
+		parachains_relay::parachains_loop::run(
+			source_client,
+			target_client,
+			metrics_params,
+			futures::future::pending(),
+		)
+		.await
+		.map_err(|e| anyhow::format_err!("{}", e))
+	}
+}

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

@@ -22,6 +22,7 @@ use relay_substrate_client::{Chain, ChainWithUtilityPallet, UtilityPallet};
 
 use std::marker::PhantomData;
 
+pub mod cli;
 pub mod equivocation;
 pub mod error;
 pub mod finality;