add wrapper for session manager

runtime/basilisk/src/system.rs

@@ -17,6 +17,7 @@
 
 use super::*;
 use crate::governance::{origins::GeneralAdmin, TechCommitteeMajority, TechnicalCollective, TreasuryAccount};
+use sp_io::transaction_index::index;
 
 use pallet_transaction_multi_payment::{DepositAll, TransferFees};
 use pallet_transaction_payment::{Multiplier, TargetedFeeAdjustment};
@@ -540,12 +541,36 @@ impl pallet_collator_rewards::Config for Runtime {
 	type RewardPerCollator = RewardPerCollator;
 	type RewardCurrencyId = NativeAssetId;
 	type ExcludedCollators = ExcludedCollators;
-	// We wrap the ` SessionManager` implementation of `CollatorSelection` to get the collatrs that
-	// we hand out rewards to.
-	type SessionManager = CollatorSelection;
+
+	type SessionManager = RotatingCollatorManager;
 	type MaxCandidates = MaxInvulnerables;
 }
 
+pub struct RotatingCollatorManager;
+impl SessionManager<AccountId> for RotatingCollatorManager {
+	fn new_session(new_index: SessionIndex) -> Option<Vec<AccountId>> {
+		// We wrap the ` SessionManager` implementation of `CollatorSelection` to get the collators that
+		// we hand out rewards to,
+		// then we rotate the collators to have a regular distribution for block production
+
+		let mut collators = CollatorSelection::new_session(new_index)?;
+
+		if !collators.is_empty() {
+			collators.rotate_left(1);
+		}
+
+		Some(collators)
+	}
+
+	fn end_session(end_index: SessionIndex) {
+		CollatorSelection::end_session(end_index)
+	}
+
+	fn start_session(start_index: SessionIndex) {
+		CollatorSelection::start_session(start_index)
+	}
+}
+
 parameter_types! {
 	pub const BasicDeposit: Balance = 5 * DOLLARS;
 	pub const ByteDeposit: Balance = DOLLARS / 10;
@@ -614,6 +639,8 @@ use frame_system::EnsureSigned;
 
 #[cfg(not(feature = "runtime-benchmarks"))]
 use frame_system::EnsureSignedBy;
+use pallet_session::SessionManager;
+use sp_staking::SessionIndex;
 
 impl pallet_state_trie_migration::Config for Runtime {
 	type ControlOrigin = EnsureRoot<Self::AccountId>;