From 21962bd8edfb490c0c71fc7292fdf69581ee5924 Mon Sep 17 00:00:00 2001
From: Svyatoslav Nikolsky <svyatonik@gmail.com>
Date: Tue, 16 Apr 2024 08:56:17 +0300
Subject: [PATCH] port FinalityApi::free_headers_interval from
 https://github.com/paritytech/parity-bridges-common/pull/2884

---
 bridges/primitives/runtime/src/chain.rs         | 12 ++++++++++++
 .../bridge-hubs/bridge-hub-rococo/src/lib.rs    | 17 ++++++++++++++++-
 .../bridge-hubs/bridge-hub-westend/src/lib.rs   | 11 ++++++++++-
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/bridges/primitives/runtime/src/chain.rs b/bridges/primitives/runtime/src/chain.rs
index f232c7726a91..1b1c623104f9 100644
--- a/bridges/primitives/runtime/src/chain.rs
+++ b/bridges/primitives/runtime/src/chain.rs
@@ -314,6 +314,11 @@ macro_rules! decl_bridge_finality_runtime_apis {
 				pub const [<BEST_FINALIZED_ $chain:upper _HEADER_METHOD>]: &str =
 					stringify!([<$chain:camel FinalityApi_best_finalized>]);
 
+				/// Name of the `<ThisChain>FinalityApi::free_headers_interval` runtime method.
+				pub const [<FREE_HEADERS_INTERVAL_FOR_ $chain:upper _METHOD>]: &str =
+					stringify!([<$chain:camel FinalityApi_free_headers_interval>]);
+
+
 				$(
 					/// Name of the `<ThisChain>FinalityApi::accepted_<consensus>_finality_proofs`
 					/// runtime method.
@@ -330,6 +335,13 @@ macro_rules! decl_bridge_finality_runtime_apis {
 						/// Returns number and hash of the best finalized header known to the bridge module.
 						fn best_finalized() -> Option<bp_runtime::HeaderId<Hash, BlockNumber>>;
 
+						/// Returns free headers interval, if it is configured in the runtime.
+						/// The caller expects that if his transaction improves best known header
+						/// at least by the free_headers_interval`, it will be fee-free.
+						///
+						/// See [`pallet_bridge_grandpa::Config::FreeHeadersInterval`] for details.
+						fn free_headers_interval() -> Option<BlockNumber>;
+
 						$(
 							/// Returns the justifications accepted in the current block.
 							fn [<synced_headers_ $consensus:lower _info>](
diff --git a/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs b/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs
index da4f8c6e9dd6..cc59e71ea25f 100644
--- a/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs
+++ b/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs
@@ -69,7 +69,7 @@ use frame_support::{
 	dispatch::DispatchClass,
 	genesis_builder_helper::{build_state, get_preset},
 	parameter_types,
-	traits::{ConstBool, ConstU32, ConstU64, ConstU8, TransformOrigin},
+	traits::{ConstBool, ConstU32, ConstU64, ConstU8, Get, TransformOrigin},
 	weights::{ConstantMultiplier, Weight},
 	PalletId,
 };
@@ -962,6 +962,11 @@ impl_runtime_apis! {
 		fn best_finalized() -> Option<HeaderId<bp_westend::Hash, bp_westend::BlockNumber>> {
 			BridgeWestendGrandpa::best_finalized()
 		}
+		fn free_headers_interval() -> Option<bp_westend::BlockNumber> {
+			<Runtime as pallet_bridge_grandpa::Config<
+				bridge_common_config::BridgeGrandpaWestendInstance
+			>>::FreeHeadersInterval::get()
+		}
 		fn synced_headers_grandpa_info(
 		) -> Vec<bp_header_chain::StoredHeaderGrandpaInfo<bp_westend::Header>> {
 			BridgeWestendGrandpa::synced_headers_grandpa_info()
@@ -974,6 +979,10 @@ impl_runtime_apis! {
 				bp_bridge_hub_westend::BridgeHubWestend
 			>().unwrap_or(None)
 		}
+		fn free_headers_interval() -> Option<bp_bridge_hub_westend::BlockNumber> {
+			// "free interval" is not currently used for parachains
+			None
+		}
 	}
 
 	// This is exposed by BridgeHubRococo
@@ -1008,6 +1017,12 @@ impl_runtime_apis! {
 			BridgePolkadotBulletinGrandpa::best_finalized()
 		}
 
+		fn free_headers_interval() -> Option<bp_polkadot_bulletin::BlockNumber> {
+			<Runtime as pallet_bridge_grandpa::Config<
+				bridge_common_config::BridgeGrandpaRococoBulletinInstance
+			>>::FreeHeadersInterval::get()
+		}
+
 		fn synced_headers_grandpa_info(
 		) -> Vec<bp_header_chain::StoredHeaderGrandpaInfo<bp_polkadot_bulletin::Header>> {
 			BridgePolkadotBulletinGrandpa::synced_headers_grandpa_info()
diff --git a/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs b/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs
index 1475be5bc125..5dea30436a83 100644
--- a/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs
+++ b/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs
@@ -63,7 +63,7 @@ use frame_support::{
 	dispatch::DispatchClass,
 	genesis_builder_helper::{build_state, get_preset},
 	parameter_types,
-	traits::{ConstBool, ConstU32, ConstU64, ConstU8, TransformOrigin},
+	traits::{ConstBool, ConstU32, ConstU64, ConstU8, Get, TransformOrigin},
 	weights::{ConstantMultiplier, Weight},
 	PalletId,
 };
@@ -711,6 +711,11 @@ impl_runtime_apis! {
 		fn best_finalized() -> Option<HeaderId<bp_rococo::Hash, bp_rococo::BlockNumber>> {
 			BridgeRococoGrandpa::best_finalized()
 		}
+		fn free_headers_interval() -> Option<bp_rococo::BlockNumber> {
+			<Runtime as pallet_bridge_grandpa::Config<
+				bridge_to_rococo_config::BridgeGrandpaRococoInstance
+			>>::FreeHeadersInterval::get()
+		}
 		fn synced_headers_grandpa_info(
 		) -> Vec<bp_header_chain::StoredHeaderGrandpaInfo<bp_rococo::Header>> {
 			BridgeRococoGrandpa::synced_headers_grandpa_info()
@@ -723,6 +728,10 @@ impl_runtime_apis! {
 				bp_bridge_hub_rococo::BridgeHubRococo
 			>().unwrap_or(None)
 		}
+		fn free_headers_interval() -> Option<bp_bridge_hub_rococo::BlockNumber> {
+			// "free interval" is not currently used for parachains
+			None
+		}
 	}
 
 	impl bp_bridge_hub_rococo::FromBridgeHubRococoInboundLaneApi<Block> for Runtime {