CU-1wty1zv fixed lending (#484)

* oracle api clarification

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixing pr comments

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixed comment

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* crazy fmt issue

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* just something to tirgget build after fail

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixed lending

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixed price, added ratio test

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixed comments of review

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

* fixed comments

Signed-off-by: Dzmitry Lahoda <dzmitry@lahoda.pro>

.config/cargo_spellcheck.dic

@@ -22,4 +22,4 @@ tombstoned
 u128
 Wasm
 Xcm
-XCM
+Dispatchable

frame/assets/src/benchmarking.rs

@@ -34,14 +34,14 @@ benchmarks! {
 		let asset_id: T::AssetId = ASSET_ID.into();
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::MultiCurrency::mint_into(asset_id, &caller, amount).unwrap();
+		T::MultiCurrency::mint_into(asset_id, &caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Signed(caller), asset_id, dest, amount, true)
 
 	transfer_native {
 		let caller: T::AccountId = whitelisted_caller();
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::NativeCurrency::mint_into(&caller, amount).unwrap();
+		T::NativeCurrency::mint_into(&caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Signed(caller), dest, amount, false)
 
 	force_transfer {
@@ -50,30 +50,30 @@ benchmarks! {
 		let from = T::Lookup::unlookup(FROM_ACCOUNT.into());
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::MultiCurrency::mint_into(asset_id, &caller, amount).unwrap();
+		T::MultiCurrency::mint_into(asset_id, &caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Root, asset_id, from, dest, amount, false)
 
 	force_transfer_native {
 		let caller: T::AccountId = FROM_ACCOUNT.into();
 		let from = T::Lookup::unlookup(FROM_ACCOUNT.into());
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::NativeCurrency::mint_into(&caller, amount).unwrap();
+		T::NativeCurrency::mint_into(&caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Root, from, dest, amount, false)
 
 	transfer_all {
 		let caller: T::AccountId = whitelisted_caller();
 		let asset_id: T::AssetId = ASSET_ID.into();
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::MultiCurrency::mint_into(asset_id, &caller, amount).unwrap();
+		T::MultiCurrency::mint_into(asset_id, &caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Signed(caller), asset_id, dest, false)
 
 	transfer_all_native {
 		let caller: T::AccountId = whitelisted_caller();
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::NativeCurrency::mint_into(&caller, amount).unwrap();
+		T::NativeCurrency::mint_into(&caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Signed(caller), dest, false)
 
 	mint_initialize {
@@ -98,7 +98,7 @@ benchmarks! {
 		let asset_id: T::AssetId = ASSET_ID.into();
 		let dest = T::Lookup::unlookup(TO_ACCOUNT.into());
 		let amount: T::Balance = TRANSFER_AMOUNT.into();
-		T::MultiCurrency::mint_into(asset_id, &caller, amount).unwrap();
+		T::MultiCurrency::mint_into(asset_id, &caller, amount).expect("always can mint in test");
 	}: _(RawOrigin::Root, asset_id, dest, amount)
 
 }

frame/composable-traits/src/auction.rs

@@ -1,33 +1,2 @@
-use crate::loans::DurationSeconds;
-use frame_support::pallet_prelude::*;
-use scale_info::TypeInfo;
-use sp_runtime::Permill;
-
-#[derive(Decode, Encode, Clone, TypeInfo, Debug, PartialEq)]
-pub enum AuctionStepFunction {
-	/// default - direct pass through to dex without steps, just to satisfy defaults and reasonably
-	/// for testing
-	LinearDecrease(LinearDecrease),
-	StairstepExponentialDecrease(StairstepExponentialDecrease),
-}
-
-impl Default for AuctionStepFunction {
-	fn default() -> Self {
-		Self::LinearDecrease(Default::default())
-	}
-}
-
-#[derive(Default, Decode, Encode, Clone, TypeInfo, Debug, PartialEq)]
-pub struct LinearDecrease {
-	/// Seconds after auction start when the price reaches zero
-	pub total: DurationSeconds,
-}
-
-#[derive(Default, Decode, Encode, Clone, TypeInfo, Debug, PartialEq)]
-pub struct StairstepExponentialDecrease {
-	// Length of time between price drops
-	pub step: DurationSeconds,
-	// Per-step multiplicative factor, usually more than 50%, mostly closer to 100%, but not 100%.
-	// Drop per unit of `step`.
-	pub cut: Permill,
-}
+// TODO: how type alias to such generics can be achieved?
+// pub type DutchAuction = SellEngine<AuctionStepFunction>;

frame/composable-traits/src/currency.rs

@@ -1,9 +1,11 @@
 use codec::FullCodec;
 use frame_support::pallet_prelude::*;
 use scale_info::TypeInfo;
-use sp_runtime::traits::AtLeast32BitUnsigned;
+use sp_runtime::traits::{AtLeast32BitUnsigned, Zero};
 use sp_std::fmt::Debug;
 
+use crate::math::SafeArithmetic;
+
 /// really u8, but easy to do math operations
 pub type Exponent = u32;
 
@@ -77,6 +79,18 @@ impl<
 {
 }
 
+/// limited counted number trait which maximal number is more than `u64`,  but not more than `u128`,
+/// so inner type is either u64 or u128 with helpers for producing `ArithmeticError`s instead of
+/// `Option`s.
+pub trait MathBalance:
+	PartialOrd + Zero + SafeArithmetic + Into<u128> + TryFrom<u128> + From<u64> + Copy
+{
+}
+impl<T: PartialOrd + Zero + SafeArithmetic + Into<u128> + TryFrom<u128> + From<u64> + Copy>
+	MathBalance for T
+{
+}
+
 // hack to imitate type alias until it is in stable
 // named with like implying it is`like` is is necessary to be `AssetId`, but may be not enough (if
 // something is `AssetIdLike` than it is not always asset)

frame/composable-traits/src/defi.rs

@@ -1,37 +1,42 @@
-//! Common codes for defi pallets
-
+//! Common codes and conventions for DeFi pallets
 use codec::{Codec, Decode, Encode, FullCodec};
 use frame_support::{pallet_prelude::MaybeSerializeDeserialize, Parameter};
 use scale_info::TypeInfo;
 use sp_runtime::{
+	helpers_128bit::multiply_by_rational,
 	traits::{CheckedAdd, CheckedMul, CheckedSub, Zero},
-	ArithmeticError, DispatchError, FixedPointOperand, FixedU128,
+	ArithmeticError, DispatchError, FixedPointNumber, FixedPointOperand, FixedU128,
 };
 
-use crate::{
-	currency::{AssetIdLike, BalanceLike},
-	math::{LiftedFixedBalance, SafeArithmetic},
-};
+use crate::currency::{AssetIdLike, BalanceLike, MathBalance};
 
 #[derive(Encode, Decode, TypeInfo, Debug, Clone, PartialEq)]
 pub struct Take<Balance> {
 	/// amount of `base`
 	pub amount: Balance,
 	/// direction depends on referenced order type
-	/// either minimal or maximal amount of `quote` for given unit of `base`
-	pub limit: Balance,
+	/// either minimal or maximal amount of `quote` for given `base`
+	/// depending on engine configuration, `limit` can be hard or flexible (change with time)
+	pub limit: LiftedFixedBalance,
 }
 
-impl<Balance: PartialOrd + Zero + SafeArithmetic> Take<Balance> {
+impl<Balance: MathBalance> Take<Balance> {
 	pub fn is_valid(&self) -> bool {
-		self.amount > Balance::zero() && self.limit > Balance::zero()
+		self.amount > Balance::zero() && self.limit > Ratio::zero()
 	}
-	pub fn new(amount: Balance, limit: Balance) -> Self {
+
+	pub fn new(amount: Balance, limit: Ratio) -> Self {
 		Self { amount, limit }
 	}
 
-	pub fn quote_amount(&self) -> Result<Balance, ArithmeticError> {
-		self.amount.safe_mul(&self.limit)
+	pub fn quote_limit_amount(&self) -> Result<Balance, ArithmeticError> {
+		self.quote_amount(self.amount)
+	}
+
+	pub fn quote_amount(&self, amount: Balance) -> Result<Balance, ArithmeticError> {
+		let result = multiply_by_rational(amount.into(), self.limit.into_inner(), Ratio::DIV)
+			.map_err(|_| ArithmeticError::Overflow)?;
+		result.try_into().map_err(|_| ArithmeticError::Overflow)
 	}
 }
 
@@ -42,15 +47,15 @@ pub struct Sell<AssetId, Balance> {
 	pub take: Take<Balance>,
 }
 
-impl<AssetId: PartialEq, Balance: PartialOrd + Zero + SafeArithmetic> Sell<AssetId, Balance> {
+impl<AssetId: PartialEq, Balance: MathBalance> Sell<AssetId, Balance> {
 	pub fn is_valid(&self) -> bool {
 		self.take.is_valid()
 	}
 	pub fn new(
 		base: AssetId,
 		quote: AssetId,
 		base_amount: Balance,
-		minimal_base_unit_price_in_quote: Balance,
+		minimal_base_unit_price_in_quote: Ratio,
 	) -> Self {
 		Self {
 			take: Take { amount: base_amount, limit: minimal_base_unit_price_in_quote },
@@ -70,9 +75,11 @@ impl<AssetId: PartialEq, Balance: PartialOrd + Zero + SafeArithmetic> Sell<Asset
 pub struct CurrencyPair<AssetId> {
 	/// See [Base Currency](https://www.investopedia.com/terms/b/basecurrency.asp).
 	/// Also can be named `native`(to the market) currency.
+	/// Usually less stable, can be used as collateral.
 	pub base: AssetId,
 	/// Counter currency.
 	/// Also can be named `price` currency.
+	/// Usually more stable, may be `borrowable` asset.
 	pub quote: AssetId,
 }
 
@@ -90,9 +97,10 @@ impl<AssetId: PartialEq> CurrencyPair<AssetId> {
 	/// assert_eq!(slice[0], pair.base);
 	/// assert_eq!(slice[1], pair.quote);
 	/// ```
-	/// ```compile_fail
+	/// ```rust
 	/// # let pair = composable_traits::defi::CurrencyPair::<u128>::new(13, 42);
 	/// # let slice =  pair.as_slice();
+	/// // it is copy
 	/// drop(pair);
 	/// let _ = slice[0];
 	/// ```
@@ -185,6 +193,7 @@ pub trait DeFiComposableConfig: frame_system::Config {
 	type MayBeAssetId: AssetIdLike + MaybeSerializeDeserialize + Default;
 
 	type Balance: BalanceLike
+		+ MathBalance
 		+ Default
 		+ Parameter
 		+ Codec
@@ -197,12 +206,52 @@ pub trait DeFiComposableConfig: frame_system::Config {
 		+ From<u64> // at least 64 bit
 		+ Zero
 		+ FixedPointOperand
-		+ Into<LiftedFixedBalance> // integer part not more than bits in this
 		+ Into<u128>; // cannot do From<u128>, until LiftedFixedBalance integer part is larger than 128
 			  // bit
 }
 
-/// The fixed point number from 0..to max.
-/// Unlike `Ratio` it can be more than 1.
-/// And unlike `NormalizedCollateralFactor`, it can be less than one.
+/// The fixed point number from 0..to max
 pub type Rate = FixedU128;
+
+/// Is [1..MAX]
+pub type OneOrMoreFixedU128 = FixedU128;
+
+/// The fixed point number of suggested by substrate precision
+/// Must be (1.0..MAX] because applied only to price normalized values
+pub type MoreThanOneFixedU128 = FixedU128;
+
+/// Must be [0..1]
+pub type ZeroToOneFixedU128 = FixedU128;
+
+/// Number like of higher bits, so that amount and balance calculations are done it it with higher
+/// precision via fixed point.
+/// While this is 128 bit, cannot support u128 because 18 bits are for of mantissa (so maximal
+/// integer is 110 bit). Can support u128 if lift upper to use FixedU256 analog.
+pub type LiftedFixedBalance = FixedU128;
+
+/// unitless ratio of one thing to other.
+pub type Ratio = FixedU128;
+
+#[cfg(test)]
+mod tests {
+	use super::{Ratio, Take};
+	use sp_runtime::FixedPointNumber;
+
+	#[test]
+	fn take_ratio_half() {
+		let price = 10;
+		let amount = 100_u128;
+		let take = Take::new(amount, Ratio::saturating_from_integer(price));
+		let result = take.quote_amount(amount / 2).unwrap();
+		assert_eq!(result, price * amount / 2);
+	}
+
+	#[test]
+	fn take_ratio_half_amount_half_price() {
+		let price_part = 50;
+		let amount = 100_u128;
+		let take = Take::new(amount, Ratio::saturating_from_rational(price_part, 100));
+		let result = take.quote_amount(amount).unwrap();
+		assert_eq!(result, price_part * amount / 100);
+	}
+}

frame/composable-traits/src/lending/math.rs

@@ -12,23 +12,11 @@ use sp_runtime::{
 use sp_arithmetic::per_things::Percent;
 
 use crate::{
-	defi::Rate,
-	loans::{DurationSeconds, ONE_HOUR},
-	math::{LiftedFixedBalance, SafeArithmetic},
+	defi::{LiftedFixedBalance, Rate, ZeroToOneFixedU128},
+	math::SafeArithmetic,
+	time::{DurationSeconds, SECONDS_PER_YEAR_NAIVE},
 };
 
-/// The fixed point number of suggested by substrate precision
-/// Must be (1.0.. because applied only to price normalized values
-pub type NormalizedCollateralFactor = FixedU128;
-
-/// Must be [0..1]
-/// TODO: implement Ratio as wrapper over FixedU128
-pub type Ratio = FixedU128;
-
-/// current notion of year will take away 1/365 from lenders and give away to borrowers (as does no
-/// accounts to length of year)
-pub const SECONDS_PER_YEAR: DurationSeconds = 365 * 24 * ONE_HOUR;
-
 /// utilization_ratio = total_borrows / (total_cash + total_borrows)
 pub fn calc_utilization_ratio(
 	cash: LiftedFixedBalance,
@@ -110,9 +98,13 @@ impl InterestRateModel {
 	}
 
 	/// Calculates the current supply interest rate
-	pub fn get_supply_rate(borrow_rate: Rate, util: Ratio, reserve_factor: Ratio) -> Rate {
+	pub fn get_supply_rate(
+		borrow_rate: Rate,
+		util: ZeroToOneFixedU128,
+		reserve_factor: ZeroToOneFixedU128,
+	) -> Rate {
 		// ((1 - reserve_factor) * borrow_rate) * utilization
-		let one_minus_reserve_factor = Ratio::one().saturating_sub(reserve_factor);
+		let one_minus_reserve_factor = ZeroToOneFixedU128::one().saturating_sub(reserve_factor);
 		let rate_to_pool = borrow_rate.saturating_mul(one_minus_reserve_factor);
 
 		rate_to_pool.saturating_mul(util)
@@ -151,15 +143,18 @@ pub struct JumpModel {
 }
 
 impl JumpModel {
-	pub const MAX_BASE_RATE: Ratio = Ratio::from_inner(100_000_000_000_000_000); // 10%
-	pub const MAX_JUMP_RATE: Ratio = Ratio::from_inner(300_000_000_000_000_000); // 30%
-	pub const MAX_FULL_RATE: Ratio = Ratio::from_inner(500_000_000_000_000_000); // 50%
+	pub const MAX_BASE_RATE: ZeroToOneFixedU128 =
+		ZeroToOneFixedU128::from_inner(ZeroToOneFixedU128::DIV * 10 / 100);
+	pub const MAX_JUMP_RATE: ZeroToOneFixedU128 =
+		ZeroToOneFixedU128::from_inner(ZeroToOneFixedU128::DIV * 30 / 100);
+	pub const MAX_FULL_RATE: ZeroToOneFixedU128 =
+		ZeroToOneFixedU128::from_inner(ZeroToOneFixedU128::DIV * 50 / 100);
 
 	/// Create a new rate model
 	pub fn new(
-		base_rate: Ratio,
-		jump_rate: Ratio,
-		full_rate: Ratio,
+		base_rate: ZeroToOneFixedU128,
+		jump_rate: ZeroToOneFixedU128,
+		full_rate: ZeroToOneFixedU128,
 		target_utilization: Percent,
 	) -> Option<JumpModel> {
 		let model = Self { base_rate, jump_rate, full_rate, target_utilization };
@@ -390,7 +385,7 @@ pub fn accrued_interest(
 	borrow_rate
 		.checked_mul_int(amount)?
 		.checked_mul(delta_time.into())?
-		.checked_div(SECONDS_PER_YEAR.into())
+		.checked_div(SECONDS_PER_YEAR_NAIVE.into())
 }
 
 /// compounding increment of borrow index
@@ -402,7 +397,7 @@ pub fn increment_index(
 	borrow_rate
 		.safe_mul(&index)?
 		.safe_mul(&FixedU128::saturating_from_integer(delta_time))?
-		.safe_div(&FixedU128::saturating_from_integer(SECONDS_PER_YEAR))?
+		.safe_div(&FixedU128::saturating_from_integer(SECONDS_PER_YEAR_NAIVE))?
 		.safe_add(&index)
 }
 
@@ -412,5 +407,5 @@ pub fn increment_borrow_rate(
 ) -> Result<Rate, ArithmeticError> {
 	borrow_rate
 		.safe_mul(&FixedU128::saturating_from_integer(delta_time))?
-		.safe_div(&FixedU128::saturating_from_integer(SECONDS_PER_YEAR))
+		.safe_div(&FixedU128::saturating_from_integer(SECONDS_PER_YEAR_NAIVE))
 }