feat: boost fee split

state-chain/custom-rpc/src/lib.rs

@@ -49,7 +49,7 @@ use sp_api::{ApiError, ApiExt, CallApiAt};
 use sp_core::U256;
 use sp_runtime::{
 	traits::{Block as BlockT, Header as HeaderT, UniqueSaturatedInto},
-	Permill,
+	Percent, Permill,
 };
 use sp_state_machine::InspectState;
 use state_chain_runtime::{
@@ -565,6 +565,7 @@ mod boost_pool_rpc {
 		available_amounts: Vec<AccountAndAmount>,
 		deposits_pending_finalization: Vec<PendingBoost>,
 		pending_withdrawals: Vec<PendingWithdrawal>,
+		network_fee_deduction_percents: Percent,
 	}
 
 	impl BoostPoolDetailsRpc {
@@ -602,6 +603,7 @@ mod boost_pool_rpc {
 						pending_deposits,
 					})
 					.collect(),
+				network_fee_deduction_percents: details.network_fee_deduction_percents,
 			}
 		}
 	}
@@ -2422,6 +2424,7 @@ mod test {
 				(1, BTreeMap::from([(ID_1.clone(), OwedAmount { total: 1_000, fee: 50 })])),
 			]),
 			pending_withdrawals: Default::default(),
+			network_fee_deduction_percents: Percent::from_percent(40),
 		}
 	}
 
@@ -2439,6 +2442,7 @@ mod test {
 				(ID_1.clone(), BTreeSet::from([0])),
 				(ID_2.clone(), BTreeSet::from([0])),
 			]),
+			network_fee_deduction_percents: Percent::from_percent(0),
 		}
 	}
 

state-chain/custom-rpc/src/snapshots/custom_rpc__test__boost_details_serialization.snap

@@ -37,7 +37,8 @@ expression: val
         ]
       }
     ],
-    "pending_withdrawals": []
+    "pending_withdrawals": [],
+    "network_fee_deduction_percents": 40
   },
   {
     "fee_tier": 30,
@@ -72,6 +73,7 @@ expression: val
           0
         ]
       }
-    ]
+    ],
+    "network_fee_deduction_percents": 0
   }
 ]

state-chain/pallets/cf-ingress-egress/src/boost_pool.rs

@@ -3,7 +3,7 @@ mod tests;
 
 use frame_support::DefaultNoBound;
 use sp_runtime::{
-	helpers_128bit::multiply_by_rational_with_rounding, Rounding, SaturatedConversion,
+	helpers_128bit::multiply_by_rational_with_rounding, Percent, Rounding, SaturatedConversion,
 };
 use sp_std::collections::{btree_map::BTreeMap, btree_set::BTreeSet};
 
@@ -146,6 +146,15 @@ pub struct BoostPool<AccountId, C: Chain> {
 	pending_withdrawals: BTreeMap<AccountId, BTreeSet<PrewitnessedDepositId>>,
 }
 
+#[derive(DefaultNoBound, DebugNoBound, PartialEqNoBound)]
+pub struct DepositFinalisationOutcomeForPool<AccountId, C: Chain>
+where
+	AccountId: PartialEq + core::fmt::Debug,
+{
+	pub unlocked_funds: Vec<(AccountId, C::ChainAmount)>,
+	pub amount_credited: C::ChainAmount,
+}
+
 impl<AccountId, C: Chain> BoostPool<AccountId, C>
 where
 	AccountId: PartialEq + Ord + Clone + core::fmt::Debug,
@@ -225,6 +234,7 @@ where
 		&mut self,
 		prewitnessed_deposit_id: PrewitnessedDepositId,
 		amount_to_boost: C::ChainAmount,
+		network_fee_deduction: Percent,
 	) -> Result<(C::ChainAmount, C::ChainAmount), &'static str> {
 		let amount_to_boost = ScaledAmount::<C>::from_chain_amount(amount_to_boost);
 		let full_amount_fee = fee_from_boosted_amount(amount_to_boost, self.fee_bps);
@@ -240,7 +250,12 @@ where
 			(provided_amount, fee)
 		};
 
-		self.use_funds_for_boosting(prewitnessed_deposit_id, provided_amount, fee_amount)?;
+		// NOTE: only a portion of the boost fee goes to the boost pool,
+		// the rest is charged as network fee:
+		let network_fee = network_fee_deduction * u128::from(fee_amount);
+		let boost_pool_fee = fee_amount.saturating_sub(ScaledAmount::from(network_fee));
+
+		self.use_funds_for_boosting(prewitnessed_deposit_id, provided_amount, boost_pool_fee)?;
 
 		Ok((
 			provided_amount.saturating_add(fee_amount).into_chain_amount(),
@@ -254,7 +269,7 @@ where
 		&mut self,
 		prewitnessed_deposit_id: PrewitnessedDepositId,
 		required_amount: ScaledAmount<C>,
-		boost_fee: ScaledAmount<C>,
+		boost_pool_fee: ScaledAmount<C>,
 	) -> Result<(), &'static str> {
 		let current_total_available_amount = self.available_amount;
 
@@ -266,7 +281,7 @@ where
 		let mut total_contributed = ScaledAmount::<C>::default();
 		let mut to_receive_recorded = ScaledAmount::default();
 
-		let amount_to_receive = required_amount.saturating_add(boost_fee);
+		let amount_to_receive = required_amount.saturating_add(boost_pool_fee);
 
 		let mut boosters_to_receive: BTreeMap<_, _> = self
 			.amounts
@@ -347,13 +362,14 @@ where
 	pub(crate) fn process_deposit_as_finalised(
 		&mut self,
 		prewitnessed_deposit_id: PrewitnessedDepositId,
-	) -> Vec<(AccountId, C::ChainAmount)> {
+	) -> DepositFinalisationOutcomeForPool<AccountId, C> {
 		let Some(boost_contributions) = self.pending_boosts.remove(&prewitnessed_deposit_id) else {
 			// The deposit hadn't been boosted
-			return vec![];
+			return Default::default();
 		};
 
 		let mut unlocked_funds = vec![];
+		let mut amount_credited: ScaledAmount<C> = 0.into();
 
 		for (booster_id, amount) in boost_contributions {
 			// Depending on whether the booster is withdrawing, add deposits to
@@ -371,9 +387,14 @@ where
 			} else {
 				self.add_funds_inner(booster_id, amount.total);
 			}
+
+			amount_credited = amount_credited.saturating_add(amount.total);
 		}
 
-		unlocked_funds
+		DepositFinalisationOutcomeForPool {
+			unlocked_funds,
+			amount_credited: amount_credited.into_chain_amount(),
+		}
 	}
 
 	// Returns the number of boosters affected