Loans: borrow & repay method using pricing-based principal (#1455)

* main implementation * minor clean change * all previous tests passing * add new tests * fix benchmarks * fix integration-tests
centrifuge · Jul 14, 2023 · a3bd197 · a3bd197
1 parent 10e23ec
commit a3bd197
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Showing 15 changed files with 550 additions and 268 deletions.
diff --git a/pallets/loans/src/benchmarking.rs b/pallets/loans/src/benchmarking.rs
@@ -41,15 +41,15 @@ use crate::{
 		loans::LoanInfo,
 		pricing::{
 			internal::{InternalPricing, MaxBorrowAmount},
-			Pricing,
+			Pricing, PricingAmount, RepaidPricingAmount,
 		},
 	},
 	pallet::*,
 	types::{
 		policy::{WriteOffRule, WriteOffTrigger},
 		valuation::{DiscountedCashFlow, ValuationMethod},
 		BorrowRestrictions, InterestPayments, LoanMutation, LoanRestrictions, Maturity,
-		PayDownSchedule, RepaidAmount, RepayRestrictions, RepaymentSchedule,
+		PayDownSchedule, RepayRestrictions, RepaymentSchedule,
 	},
 };
 
@@ -189,7 +189,7 @@ where
 			RawOrigin::Signed(borrower).into(),
 			pool_id,
 			loan_id,
-			10.into(),
+			PricingAmount::Internal(10.into()),
 		)
 		.unwrap();
 	}
@@ -200,8 +200,8 @@ where
 			RawOrigin::Signed(borrower).into(),
 			pool_id,
 			loan_id,
-			RepaidAmount {
-				principal: 10.into(),
+			RepaidPricingAmount {
+				principal: PricingAmount::Internal(10.into()),
 				interest: T::Balance::max_value(),
 				unscheduled: 0.into(),
 			},
@@ -341,7 +341,7 @@ benchmarks! {
 		let pool_id = Helper::<T>::initialize_active_state(n);
 		let loan_id = Helper::<T>::create_loan(pool_id, u16::MAX.into());
 
-	}: _(RawOrigin::Signed(borrower), pool_id, loan_id, 10.into())
+	}: _(RawOrigin::Signed(borrower), pool_id, loan_id, PricingAmount::Internal(10.into()))
 
 	repay {
 		let n in 1..Helper::<T>::max_active_loans() - 1;
@@ -351,7 +351,11 @@ benchmarks! {
 		let loan_id = Helper::<T>::create_loan(pool_id, u16::MAX.into());
 		Helper::<T>::borrow_loan(pool_id, loan_id);
 
-		let repaid = RepaidAmount { principal: 10.into(), interest: 0.into(), unscheduled: 0.into() };
+		let repaid = RepaidPricingAmount {
+			principal: PricingAmount::Internal(10.into()),
+			interest: 0.into(),
+			unscheduled: 0.into()
+		};
 
 	}: _(RawOrigin::Signed(borrower), pool_id, loan_id, repaid)
 

diff --git a/pallets/loans/src/entities/loans.rs b/pallets/loans/src/entities/loans.rs
@@ -19,6 +19,7 @@ use sp_runtime::{
 
 use super::pricing::{
 	external::ExternalActivePricing, internal::InternalActivePricing, ActivePricing, Pricing,
+	PricingAmount, RepaidPricingAmount,
 };
 use crate::{
 	pallet::{AssetOf, Config, Error, PriceOf},
@@ -279,22 +280,28 @@ impl<T: Config> ActiveLoan<T> {
 		self.write_down(value)
 	}
 
-	fn ensure_can_borrow(&self, amount: T::Balance) -> DispatchResult {
+	fn ensure_can_borrow(&self, amount: &PricingAmount<T>) -> DispatchResult {
 		let max_borrow_amount = match &self.pricing {
-			ActivePricing::Internal(inner) => inner.max_borrow_amount(self.total_borrowed)?,
-			ActivePricing::External(inner) => inner.max_borrow_amount(amount)?,
+			ActivePricing::Internal(inner) => {
+				amount.internal()?;
+				inner.max_borrow_amount(self.total_borrowed)?
+			}
+			ActivePricing::External(inner) => {
+				let external_amount = amount.external()?;
+				inner.max_borrow_amount(external_amount)?
+			}
 		};
 
 		ensure!(
-			amount <= max_borrow_amount,
+			amount.balance()? <= max_borrow_amount,
 			Error::<T>::from(BorrowLoanError::MaxAmountExceeded)
 		);
 
 		ensure!(
 			match self.restrictions.borrows {
 				BorrowRestrictions::NotWrittenOff => self.write_off_status().is_none(),
 				BorrowRestrictions::FullOnce => {
-					self.total_borrowed.is_zero() && amount == max_borrow_amount
+					self.total_borrowed.is_zero() && amount.balance()? == max_borrow_amount
 				}
 			},
 			Error::<T>::from(BorrowLoanError::Restriction)
@@ -309,15 +316,18 @@ impl<T: Config> ActiveLoan<T> {
 		Ok(())
 	}
 
-	pub fn borrow(&mut self, amount: T::Balance) -> DispatchResult {
+	pub fn borrow(&mut self, amount: &PricingAmount<T>) -> DispatchResult {
 		self.ensure_can_borrow(amount)?;
 
-		self.total_borrowed.ensure_add_assign(amount)?;
+		self.total_borrowed.ensure_add_assign(amount.balance()?)?;
 
 		match &mut self.pricing {
-			ActivePricing::Internal(inner) => inner.adjust(Adjustment::Increase(amount))?,
+			ActivePricing::Internal(inner) => {
+				inner.adjust(Adjustment::Increase(amount.balance()?))?
+			}
 			ActivePricing::External(inner) => {
-				inner.adjust(Adjustment::Increase(amount), Zero::zero())?
+				let quantity = amount.external()?.quantity;
+				inner.adjust(Adjustment::Increase(quantity), Zero::zero())?
 			}
 		}
 
@@ -332,33 +342,39 @@ impl<T: Config> ActiveLoan<T> {
 	/// - Checking repay restrictions
 	fn prepare_repayment(
 		&self,
-		mut amount: RepaidAmount<T::Balance>,
-	) -> Result<RepaidAmount<T::Balance>, DispatchError> {
+		mut amount: RepaidPricingAmount<T>,
+	) -> Result<RepaidPricingAmount<T>, DispatchError> {
 		let (interest_accrued, max_repay_principal) = match &self.pricing {
 			ActivePricing::Internal(inner) => {
+				amount.principal.internal()?;
+
 				let principal = self
 					.total_borrowed
 					.ensure_sub(self.total_repaid.principal)?;
 
 				(inner.current_interest(principal)?, principal)
 			}
 			ActivePricing::External(inner) => {
-				(inner.current_interest()?, inner.outstanding_amount()?)
+				let external_amount = amount.principal.external()?;
+				let max_repay_principal = inner.max_repay_principal(external_amount)?;
+
+				(inner.current_interest()?, max_repay_principal)
 			}
 		};
 
 		amount.interest = amount.interest.min(interest_accrued);
 
 		ensure!(
-			amount.principal <= max_repay_principal,
+			amount.principal.balance()? <= max_repay_principal,
 			Error::<T>::from(RepayLoanError::MaxPrincipalAmountExceeded)
 		);
 
 		ensure!(
 			match self.restrictions.repayments {
 				RepayRestrictions::None => true,
 				RepayRestrictions::Full => {
-					amount.principal == max_repay_principal && amount.interest == interest_accrued
+					amount.principal.balance()? == max_repay_principal
+						&& amount.interest == interest_accrued
 				}
 			},
 			Error::<T>::from(RepayLoanError::Restriction)
@@ -369,18 +385,21 @@ impl<T: Config> ActiveLoan<T> {
 
 	pub fn repay(
 		&mut self,
-		amount: RepaidAmount<T::Balance>,
-	) -> Result<RepaidAmount<T::Balance>, DispatchError> {
+		amount: RepaidPricingAmount<T>,
+	) -> Result<RepaidPricingAmount<T>, DispatchError> {
 		let amount = self.prepare_repayment(amount)?;
 
-		self.total_repaid.ensure_add_assign(&amount)?;
+		self.total_repaid
+			.ensure_add_assign(&amount.repaid_amount()?)?;
 
 		match &mut self.pricing {
 			ActivePricing::Internal(inner) => {
-				inner.adjust(Adjustment::Decrease(amount.effective()?))?
+				let amount = amount.repaid_amount()?.effective()?;
+				inner.adjust(Adjustment::Decrease(amount))?
 			}
 			ActivePricing::External(inner) => {
-				inner.adjust(Adjustment::Decrease(amount.principal), amount.interest)?
+				let quantity = amount.principal.external()?.quantity;
+				inner.adjust(Adjustment::Decrease(quantity), amount.interest)?
 			}
 		}
 

diff --git a/pallets/loans/src/entities/pricing.rs b/pallets/loans/src/entities/pricing.rs
@@ -1,8 +1,12 @@
 use codec::{Decode, Encode, MaxEncodedLen};
 use frame_support::RuntimeDebugNoBound;
 use scale_info::TypeInfo;
+use sp_runtime::{ArithmeticError, DispatchError};
 
-use crate::pallet::Config;
+use crate::{
+	pallet::{Config, Error},
+	types::RepaidAmount,
+};
 
 pub mod external;
 pub mod internal;
@@ -28,3 +32,51 @@ pub enum ActivePricing<T: Config> {
 	/// Internal attributes
 	External(external::ExternalActivePricing<T>),
 }
+
+#[derive(Encode, Decode, Clone, PartialEq, Eq, TypeInfo, RuntimeDebugNoBound, MaxEncodedLen)]
+#[scale_info(skip_type_params(T))]
+pub enum PricingAmount<T: Config> {
+	Internal(T::Balance),
+	External(external::ExternalAmount<T>),
+}
+
+impl<T: Config> PricingAmount<T> {
+	pub fn balance(&self) -> Result<T::Balance, ArithmeticError> {
+		match self {
+			Self::Internal(amount) => Ok(*amount),
+			Self::External(external) => external.balance(),
+		}
+	}
+
+	pub fn internal(&self) -> Result<T::Balance, DispatchError> {
+		match self {
+			Self::Internal(amount) => Ok(*amount),
+			Self::External(_) => Err(Error::<T>::MismatchedPricingMethod.into()),
+		}
+	}
+
+	pub fn external(&self) -> Result<external::ExternalAmount<T>, DispatchError> {
+		match self {
+			Self::Internal(_) => Err(Error::<T>::MismatchedPricingMethod.into()),
+			Self::External(principal) => Ok(principal.clone()),
+		}
+	}
+}
+
+#[derive(Encode, Decode, Clone, PartialEq, Eq, TypeInfo, RuntimeDebugNoBound, MaxEncodedLen)]
+#[scale_info(skip_type_params(T))]
+pub struct RepaidPricingAmount<T: Config> {
+	pub principal: PricingAmount<T>,
+	pub interest: T::Balance,
+	pub unscheduled: T::Balance,
+}
+
+impl<T: Config> RepaidPricingAmount<T> {
+	pub fn repaid_amount(&self) -> Result<RepaidAmount<T::Balance>, ArithmeticError> {
+		Ok(RepaidAmount {
+			principal: self.principal.balance()?,
+			interest: self.interest,
+			unscheduled: self.unscheduled,
+		})
+	}
+}
diff --git a/pallets/loans/src/entities/pricing/external.rs b/pallets/loans/src/entities/pricing/external.rs
@@ -10,14 +10,41 @@ use frame_support::{self, ensure, RuntimeDebug, RuntimeDebugNoBound};
 use scale_info::TypeInfo;
 use sp_runtime::{
 	traits::{EnsureAdd, EnsureFixedPointNumber, EnsureSub, Zero},
-	DispatchError, DispatchResult, FixedPointNumber,
+	ArithmeticError, DispatchError, DispatchResult, FixedPointNumber,
 };
 
 use crate::{
 	entities::interest::ActiveInterestRate,
 	pallet::{Config, Error, PriceOf},
 };
 
+#[derive(Encode, Decode, Clone, PartialEq, Eq, TypeInfo, RuntimeDebugNoBound, MaxEncodedLen)]
+#[scale_info(skip_type_params(T))]
+pub struct ExternalAmount<T: Config> {
+	pub quantity: T::Rate,
+	pub settlement_price: T::Balance,
+}
+
+impl<T: Config> ExternalAmount<T> {
+	pub fn new(quantity: T::Rate, price: T::Balance) -> Self {
+		Self {
+			quantity,
+			settlement_price: price,
+		}
+	}
+
+	pub fn empty() -> Self {
+		Self {
+			quantity: T::Rate::zero(),
+			settlement_price: T::Balance::zero(),
+		}
+	}
+
+	pub fn balance(&self) -> Result<T::Balance, ArithmeticError> {
+		self.quantity.ensure_mul_int(self.settlement_price)
+	}
+}
+
 /// Define the max borrow amount of a loan
 #[derive(Encode, Decode, Clone, PartialEq, Eq, TypeInfo, RuntimeDebug, MaxEncodedLen)]
 pub enum MaxBorrowAmount<Quantity> {
@@ -46,7 +73,7 @@ impl<T: Config> ExternalPricing<T> {
 	pub fn validate(&self) -> DispatchResult {
 		if let MaxBorrowAmount::Quantity(quantity) = self.max_borrow_amount {
 			ensure!(
-				quantity.frac().is_zero() && quantity > T::Rate::zero(),
+				quantity.frac().is_zero() && quantity >= T::Rate::zero(),
 				Error::<T>::AmountNotNaturalNumber
 			)
 		}
@@ -99,11 +126,6 @@ impl<T: Config> ExternalActivePricing<T> {
 		Ok(T::PriceRegistry::get(&self.info.price_id)?.1)
 	}
 
-	pub fn outstanding_amount(&self) -> Result<T::Balance, DispatchError> {
-		let price = self.current_price()?;
-		Ok(self.outstanding_quantity.ensure_mul_int(price)?)
-	}
-
 	pub fn current_interest(&self) -> Result<T::Balance, DispatchError> {
 		let outstanding_notional = self
 			.outstanding_quantity
@@ -114,7 +136,8 @@ impl<T: Config> ExternalActivePricing<T> {
 	}
 
 	pub fn present_value(&self) -> Result<T::Balance, DispatchError> {
-		self.outstanding_amount()
+		let price = self.current_price()?;
+		Ok(self.outstanding_quantity.ensure_mul_int(price)?)
 	}
 
 	pub fn present_value_cached<Prices>(&self, cache: &Prices) -> Result<T::Balance, DispatchError>
@@ -127,42 +150,42 @@ impl<T: Config> ExternalActivePricing<T> {
 
 	pub fn max_borrow_amount(
 		&self,
-		desired_amount: T::Balance,
+		amount: ExternalAmount<T>,
 	) -> Result<T::Balance, DispatchError> {
 		match self.info.max_borrow_amount {
 			MaxBorrowAmount::Quantity(quantity) => {
-				let price = self.current_price()?;
 				let available = quantity.ensure_sub(self.outstanding_quantity)?;
-				Ok(available.ensure_mul_int(price)?)
+				Ok(available.ensure_mul_int(amount.settlement_price)?)
 			}
-			MaxBorrowAmount::NoLimit => Ok(desired_amount),
+			MaxBorrowAmount::NoLimit => Ok(amount.balance()?),
 		}
 	}
 
+	pub fn max_repay_principal(
+		&self,
+		amount: ExternalAmount<T>,
+	) -> Result<T::Balance, DispatchError> {
+		Ok(self
+			.outstanding_quantity
+			.ensure_mul_int(amount.settlement_price)?)
+	}
+
 	pub fn adjust(
 		&mut self,
-		principal_adj: Adjustment<T::Balance>,
+		quantity_adj: Adjustment<T::Rate>,
 		interest: T::Balance,
 	) -> DispatchResult {
-		let quantity_adj = principal_adj.try_map(|principal| -> Result<_, DispatchError> {
-			let price = self.current_price()?;
-
-			let quantity = T::Rate::ensure_from_rational(principal, price)?;
+		self.outstanding_quantity = quantity_adj.ensure_add(self.outstanding_quantity)?;
 
+		let interest_adj = quantity_adj.try_map(|quantity| -> Result<_, DispatchError> {
 			ensure!(
-				quantity.frac().is_zero(),
-				Error::<T>::AmountNotMultipleOfPrice
+				quantity.frac().is_zero() && quantity >= T::Rate::zero(),
+				Error::<T>::AmountNotNaturalNumber
 			);
 
-			Ok(quantity)
-		})?;
-
-		self.outstanding_quantity = quantity_adj.ensure_add(self.outstanding_quantity)?;
-
-		let interest_adj = quantity_adj.try_map(|quantity| {
-			quantity
+			Ok(quantity
 				.ensure_mul_int(self.info.notional)?
-				.ensure_add(interest)
+				.ensure_add(interest)?)
 		})?;
 
 		self.interest.adjust_debt(interest_adj)?;