Merge pull request #5076 from ignazio-bovo/nara-fixes-for-amm

Nara fixes for amm

runtime-modules/common/Cargo.toml

@@ -6,17 +6,24 @@ edition = '2018'
 
 [dependencies]
 serde = { version = "1.0.101", optional = true, features = ["derive"] }
-strum = {version = "0.19", optional = true}
-strum_macros = {version = "0.19", optional = true}
-codec = { package = 'parity-scale-codec', version = '3.1.2', default-features = false, features = ['derive'] }
-scale-info = { version = "2.1.1", default-features = false, features = ["derive"] }
-sp-runtime = { package = 'sp-runtime', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-frame-support = { package = 'frame-support', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-frame-system = { package = 'frame-system', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-pallet-timestamp = { package = 'pallet-timestamp', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-sp-arithmetic = { package = 'sp-arithmetic', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-balances = { package = 'pallet-balances', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
-sp-std = { package = 'sp-std', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9'}
+strum = { version = "0.19", optional = true }
+strum_macros = { version = "0.19", optional = true }
+codec = { package = 'parity-scale-codec', version = '3.1.2', default-features = false, features = [
+	'derive',
+] }
+scale-info = { version = "2.1.1", default-features = false, features = [
+	"derive",
+] }
+sp-runtime = { package = 'sp-runtime', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+frame-support = { package = 'frame-support', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+frame-system = { package = 'frame-system', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+pallet-timestamp = { package = 'pallet-timestamp', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+sp-arithmetic = { package = 'sp-arithmetic', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+balances = { package = 'pallet-balances', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+sp-std = { package = 'sp-std', default-features = false, git = 'https://github.com/joystream/substrate.git', rev = '1d0eefca86ef31b9e7727df01a6ed23ad65491e9' }
+
+[dev-dependencies]
+parameterized = { version = "1.1.0" }
 
 [features]
 default = ['std']

runtime-modules/common/src/numerical.rs

@@ -1,5 +1,6 @@
 use core::ops::Div;
 
+use sp_arithmetic::traits::{AtLeast32BitUnsigned, CheckedAdd, CheckedMul, CheckedNeg, CheckedSub};
 use sp_runtime::{
     traits::{One, Saturating},
     FixedPointNumber, FixedU128, PerThing, Permill, Perquintill,
@@ -87,12 +88,77 @@ pub fn one_plus_interest_pow_fixed(interest: Permill, exp: FixedU128) -> FixedU1
     base_pow_int.mul(base_pow_frac)
 }
 
+// computes integral of integral at + b dt from x to y = a (y^2/2 - x^2/2) + b (y - x)
+pub fn amm_eval_inner<
+    Number: CheckedAdd + CheckedSub + CheckedMul + CheckedNeg + AtLeast32BitUnsigned + Copy,
+>(
+    x: Number,
+    y: Number,
+    a: Number,
+    b: Number,
+) -> Option<Number> {
+    if x == y {
+        return Some(Number::zero());
+    }
+    let lower_bound = y.min(x);
+    let upper_bound = y.max(x);
+    let upper_bound_sq = upper_bound.checked_mul(&upper_bound);
+    let lower_bound_sq = lower_bound.checked_mul(&lower_bound);
+    let first_term_coeff = a.div(2u32.into());
+
+    // squared diff between two Option<Number>: upper_bound_sq - lower_bound_sq
+    let diff_sq = upper_bound_sq.and_then(|upper_| lower_bound_sq.map(|lower_| upper_.sub(lower_)));
+    let diff = upper_bound.sub(lower_bound);
+    let first_term = diff_sq.and_then(|diff_sq| diff_sq.checked_mul(&first_term_coeff));
+    let second_term = diff.checked_mul(&b);
+
+    first_term
+        .and_then(|first_term_| {
+            second_term.map(|second_term_| first_term_.checked_add(&second_term_))
+        })
+        .flatten()
+}
+
 #[cfg(test)]
 mod numerical_tests {
+    use parameterized::parameterized;
     use sp_runtime::traits::Zero;
 
     use super::*;
 
+    #[parameterized(
+        input = {
+            (5u128, 10u128, 2u128, 4u128), // x < y
+            (10u128, 5u128, 2u128, 4u128), // x > y
+            (10u128, 10u128, 2u128, 4u128), // x = y
+            (u128::MAX - 1, u128::MAX , 2u128, 4u128), // overflow
+            (u128::MAX, u128::MAX , 2u128, 4u128), // x = y = u128::MAX
+            (10u128, 10u128, 0u128, 0u128), // a = b = 0
+            (10u128, 5u128, u128::MAX, u128::MAX), // overflow
+            (10u128, 10u128, u128::MAX, u128::MAX), // zero
+            (10u128, 5u128, 5u128, 2u128), // a = odd 
+        },
+        expected = {
+            Some(95),
+            Some(95),
+            Some(0),
+            None,
+            Some(0),
+            Some(0),
+            None,
+            Some(0),
+            Some(160)
+
+        }
+    )]
+    fn amm_eval_inner_base_test(input: (u128, u128, u128, u128), expected: Option<u128>) {
+        let (x, y, a, b) = input;
+
+        let result = amm_eval_inner(x, y, a, b);
+
+        assert_eq!(result, expected);
+    }
+
     #[test]
     fn log_approximation_is_accurate_up_to_14_dec_places() {
         let expected = Perquintill::from_float(0.139761942375158f64); // https://www.wolframalpha.com/input?i=ln%281+%2B+0.15%29

runtime-modules/project-token/src/errors.rs

@@ -186,6 +186,9 @@ decl_error! {
         /// Curve slope parameters below minimum allowed
         CurveSlopeParametersTooLow,
 
+        /// Attempting to sell more than amm provided supply
+        NotEnoughTokenMintedByAmmForThisSale,
+
         /// -------- Patronage --------------------------------------------------
 
         /// Target Rate is higher than current patronage rate

runtime-modules/project-token/src/lib.rs

@@ -37,7 +37,7 @@ use scale_info::TypeInfo;
 use sp_arithmetic::traits::{AtLeast32BitUnsigned, One, Saturating, Zero};
 use sp_runtime::{
     traits::{AccountIdConversion, CheckedAdd},
-    PerThing, Permill,
+    Permill,
 };
 use sp_std::collections::btree_map::BTreeMap;
 use sp_std::convert::TryInto;
@@ -856,7 +856,8 @@ decl_module! {
             let amm_treasury_account = Self::amm_treasury_account(token_id);
             let price = curve.eval::<T>(amount, AmmOperation::Buy)?.into();
             let bloat_bond = Self::bloat_bond();
-            let buy_price = Self::amm_buy_tx_fees().mul_floor(price).checked_add(&price).ok_or(Error::<T>::ArithmeticError)?;
+            let buy_tx_fee = Self::amm_buy_tx_fees().mul_floor(price);
+            let buy_price = buy_tx_fee.checked_add(&price).ok_or(Error::<T>::ArithmeticError)?;
 
             let joys_required = if !user_account_data_exists {
                 buy_price.saturating_add(bloat_bond)
@@ -893,9 +894,12 @@ decl_module! {
                 token_data.increase_amm_bought_amount_by(amount);
             });
 
-            // TODO: redirect tx fees revenue to council
+            // transfer tx_fee * price + price
             Self::transfer_joy(&sender, &amm_treasury_account, buy_price)?;
 
+            // burn tx_fee * price
+            let _ = burn_from_usable::<T>(&amm_treasury_account, buy_tx_fee);
+
             Self::deposit_event(RawEvent::TokensBoughtOnAmm(token_id, member_id, amount, buy_price));
 
             Ok(())
@@ -949,9 +953,9 @@ decl_module! {
                 ensure!(desired_price.saturating_sub(price) <= slippage_tolerance.mul_floor(desired_price), Error::<T>::SlippageToleranceExceeded);
             }
 
-            let sell_price = Self::amm_sell_tx_fees().left_from_one().mul_floor(price);
+            let sell_tx_fee = Self::amm_sell_tx_fees().mul_floor(price);
+            let sell_price = price.saturating_sub(sell_tx_fee);
 
-            // TODO: redirect tx fees revenue to council
             Self::ensure_can_transfer_joy(&amm_treasury_account, sell_price)?;
 
             // == MUTATION SAFE ==
@@ -965,8 +969,12 @@ decl_module! {
                 token_data.decrease_amm_bought_amount_by(amount);
             });
 
+            // transfer the price - tx_fee * price
             Self::transfer_joy(&amm_treasury_account, &sender, sell_price)?;
 
+            // burn tx_fee * price
+            let _ = burn_from_usable::<T>(&amm_treasury_account, sell_tx_fee);
+
             Self::deposit_event(RawEvent::TokensSoldOnAmm(token_id, member_id, amount, sell_price));
 
             Ok(())