chore: add LP mint calculation for stableswap pools

contracts/liquidity_hub/pool-network/terraswap_pair/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "terraswap-pair"
-version = "1.3.7"
+version = "1.3.8"
 authors = [
   "Terraform Labs, PTE.",
   "DELIGHT LABS",

contracts/liquidity_hub/pool-network/terraswap_pair/src/commands.rs

@@ -11,7 +11,8 @@
 #[cfg(any(feature = "osmosis_token_factory", feature = "injective"))]
 use white_whale_std::pool_network::asset::is_factory_token;
 use white_whale_std::pool_network::asset::{
-    get_total_share, Asset, AssetInfo, AssetInfoRaw, PairInfoRaw, MINIMUM_LIQUIDITY_AMOUNT,
+    get_total_share, Asset, AssetInfo, AssetInfoRaw, PairInfoRaw, PairType,
+    MINIMUM_LIQUIDITY_AMOUNT,
 };
 #[cfg(feature = "injective")]
 use white_whale_std::pool_network::denom_injective::{Coin, MsgBurn, MsgMint};
@@ -22,7 +23,9 @@
 
 use crate::error::ContractError;
 use crate::helpers;
-use crate::helpers::get_protocol_fee_for_asset;
+use crate::helpers::{
+    compute_d, compute_lp_mint_amount_for_stableswap_deposit, get_protocol_fee_for_asset,
+};
 use crate::state::{
     store_fee, ALL_TIME_BURNED_FEES, ALL_TIME_COLLECTED_PROTOCOL_FEES, COLLECTED_PROTOCOL_FEES,
     CONFIG, PAIR_INFO,
@@ -194,56 +197,112 @@
     };
 
     let total_share = get_total_share(&deps.as_ref(), liquidity_token.clone())?;
-    let share = if total_share == Uint128::zero() {
-        // Make sure at least MINIMUM_LIQUIDITY_AMOUNT is deposited to mitigate the risk of the first
-        // depositor preventing small liquidity providers from joining the pool
-        let share = Uint128::new(
-            (U256::from(deposits[0].u128())
-                .checked_mul(U256::from(deposits[1].u128()))
-                .ok_or::<ContractError>(ContractError::LiquidityShareComputation {}))?
-            .integer_sqrt()
-            .as_u128(),
-        )
-        .checked_sub(MINIMUM_LIQUIDITY_AMOUNT)
-        .map_err(|_| ContractError::InvalidInitialLiquidityAmount(MINIMUM_LIQUIDITY_AMOUNT))?;
-
-        messages.append(&mut mint_lp_token_msg(
-            liquidity_token.clone(),
-            env.contract.address.to_string(),
-            env.contract.address.to_string(),
-            MINIMUM_LIQUIDITY_AMOUNT,
-        )?);
-
-        // share should be above zero after subtracting the MINIMUM_LIQUIDITY_AMOUNT
-        if share.is_zero() {
-            return Err(ContractError::InvalidInitialLiquidityAmount(
-                MINIMUM_LIQUIDITY_AMOUNT,
-            ));
-        }
 
-        share
-    } else {
-        // min(1, 2)
-        // 1. sqrt(deposit_0 * exchange_rate_0_to_1 * deposit_0) * (total_share / sqrt(pool_0 * pool_1))
-        // == deposit_0 * total_share / pool_0
-        // 2. sqrt(deposit_1 * exchange_rate_1_to_0 * deposit_1) * (total_share / sqrt(pool_1 * pool_1))
-        // == deposit_1 * total_share / pool_1
-        let amount = std::cmp::min(
-            deposits[0].multiply_ratio(total_share, pools[0].amount),
-            deposits[1].multiply_ratio(total_share, pools[1].amount),
-        );
-
-        // assert slippage tolerance
-        helpers::assert_slippage_tolerance(
-            &slippage_tolerance,
-            &deposits,
-            &pools,
-            pair_info.pair_type,
-            amount,
-            total_share,
-        )?;
+    let share = match &pair_info.pair_type {
+        PairType::StableSwap { amp } => {
+            if total_share == Uint128::zero() {
+                // Make sure at least MINIMUM_LIQUIDITY_AMOUNT is deposited to mitigate the risk of the first
+                // depositor preventing small liquidity providers from joining the pool
+                let min_lp_token_amount = MINIMUM_LIQUIDITY_AMOUNT * Uint128::from(2u8);
+
+                let share = Uint128::try_from(compute_d(amp, deposits[0], deposits[1]).unwrap())?
+                    .saturating_sub(min_lp_token_amount);
+
+                messages.append(&mut mint_lp_token_msg(
+                    liquidity_token.clone(),
+                    env.contract.address.to_string(),
+                    env.contract.address.to_string(),
+                    min_lp_token_amount,
+                )?);
+
+                // share should be above zero after subtracting the min_lp_token_amount
+                if share.is_zero() {
+                    return Err(ContractError::InvalidInitialLiquidityAmount(
+                        min_lp_token_amount,
+                    ));
+                }
 
-        amount
+                share
+            } else {
+                let amount = compute_lp_mint_amount_for_stableswap_deposit(
+                    amp,
+                    deposits[0],
+                    deposits[1],
+                    pools[0].amount,
+                    pools[1].amount,
+                    total_share,
+                )
+                .unwrap();
+
+                // assert slippage tolerance
+                helpers::assert_slippage_tolerance(
+                    &slippage_tolerance,
+                    &deposits,
+                    &pools,
+                    pair_info.pair_type,
+                    amount,
+                    total_share,
+                )?;
+
+                amount
+            }
+        }
+        PairType::ConstantProduct => {
+            if total_share == Uint128::zero() {
+                // Make sure at least MINIMUM_LIQUIDITY_AMOUNT is deposited to mitigate the risk of the first
+                // depositor preventing small liquidity providers from joining the pool
+                let share = Uint128::new(
+                    (U256::from(deposits[0].u128())
+                        .checked_mul(U256::from(deposits[1].u128()))
+                        .ok_or::<ContractError>(ContractError::LiquidityShareComputation {}))?
+                    .integer_sqrt()
+                    .as_u128(),
+                )
+                .checked_sub(MINIMUM_LIQUIDITY_AMOUNT)
+                .map_err(|_| {
+                    ContractError::InvalidInitialLiquidityAmount(MINIMUM_LIQUIDITY_AMOUNT)
+                })?;
+
+                messages.append(&mut mint_lp_token_msg(
+                    liquidity_token.clone(),
+                    env.contract.address.to_string(),
+                    env.contract.address.to_string(),
+                    MINIMUM_LIQUIDITY_AMOUNT,
+                )?);
+
+                // share should be above zero after subtracting the MINIMUM_LIQUIDITY_AMOUNT
+                if share.is_zero() {
+                    return Err(ContractError::InvalidInitialLiquidityAmount(
+                        MINIMUM_LIQUIDITY_AMOUNT,
+                    ));
+                }
+
+                share
+            } else {
+                // min(1, 2)
+                // 1. sqrt(deposit_0 * exchange_rate_0_to_1 * deposit_0) * (total_share / sqrt(pool_0 * pool_1))
+                // == deposit_0 * total_share / pool_0
+                // 2. sqrt(deposit_1 * exchange_rate_1_to_0 * deposit_1) * (total_share / sqrt(pool_1 * pool_1))
+                // == deposit_1 * total_share / pool_1
+                //todo fix the index stuff here
+                let amount = std::cmp::min(
+                    deposits[0].multiply_ratio(total_share, pools[0].amount),
+                    deposits[1].multiply_ratio(total_share, pools[1].amount),
+                );
+
+                // assert slippage tolerance
+                helpers::assert_slippage_tolerance(
+                    &slippage_tolerance,
+                    &deposits,
+                    &pools,
+                    pair_info.pair_type,
+                    amount,
+                    total_share,
+                )?;
+
+                amount
+            }
+        }
     };
 
     // mint LP token to sender

contracts/liquidity_hub/pool-network/terraswap_pair/src/helpers.rs

@@ -5,7 +5,7 @@
 use cosmwasm_std::CosmosMsg;
 use cosmwasm_std::{
     to_json_binary, Decimal, Decimal256, DepsMut, Env, ReplyOn, Response, StdError, StdResult,
-    Storage, SubMsg, Uint128, Uint256, WasmMsg,
+    Storage, SubMsg, Uint128, Uint256, Uint512, WasmMsg,
 };
 use cw20::MinterResponse;
 use cw_storage_plus::Item;
@@ -99,6 +99,95 @@
     ReverseSimulate,
 }
 
+/// Computes the Stable Swap invariant (D).
+///
+/// The invariant is defined as follows:
+///
+/// ```text
+/// A * sum(x_i) * n**n + D = A * D * n**n + D**(n+1) / (n**n * prod(x_i))
+/// ```
+///
+/// # Arguments
+///
+/// - `amount_a` - The amount of token A owned by the LP pool. (i.e. token A reserves)
+/// - `amount_b` - The amount of token B owned by the LP pool. (i.e. token B reserves)
+///
+#[allow(clippy::unwrap_used)]
+pub fn compute_d(amp_factor: &u64, amount_a: Uint128, amount_b: Uint128) -> Option<Uint512> {
+    let sum_x = amount_a.checked_add(amount_b).unwrap(); // sum(x_i), a.k.a S
+
+    // a and b
+    let n_coins = Uint128::new(2);
+
+    if sum_x == Uint128::zero() {
+        Some(Uint512::zero())
+    } else {
+        let amount_a_times_coins = amount_a.checked_mul(n_coins).unwrap();
+        let amount_b_times_coins = amount_b.checked_mul(n_coins).unwrap();
+
+        // Newton's method to approximate D
+        let mut d_prev: Uint512;
+        let mut d: Uint512 = sum_x.into();
+        for _ in 0..256 {
+            let mut d_prod = d;
+            d_prod = d_prod
+                .checked_mul(d)
+                .unwrap()
+                .checked_div(amount_a_times_coins.into())
+                .unwrap();
+            d_prod = d_prod
+                .checked_mul(d)
+                .unwrap()
+                .checked_div(amount_b_times_coins.into())
+                .unwrap();
+            d_prev = d;
+            d = compute_next_d(amp_factor, d, d_prod, sum_x, n_coins).unwrap();
+            // Equality with the precision of 1
+            if d > d_prev {
+                if d.checked_sub(d_prev).unwrap() <= Uint512::one() {
+                    break;
+                }
+            } else if d_prev.checked_sub(d).unwrap() <= Uint512::one() {
+                break;
+            }
+        }
+
+        Some(d)
+    }
+}
+
+#[allow(clippy::unwrap_used)]
+fn compute_next_d(
+    amp_factor: &u64,
+    d_init: Uint512,
+    d_prod: Uint512,
+    sum_x: Uint128,
+    n_coins: Uint128,
+) -> Option<Uint512> {
+    let ann = amp_factor.checked_mul(n_coins.u128() as u64)?;
+    let leverage = Uint512::from(sum_x).checked_mul(ann.into()).unwrap();
+    // d = (ann * sum_x + d_prod * n_coins) * d / ((ann - 1) * d + (n_coins + 1) * d_prod)
+    let numerator = d_init
+        .checked_mul(
+            d_prod
+                .checked_mul(n_coins.into())
+                .unwrap()
+                .checked_add(leverage)
+                .unwrap(),
+        )
+        .unwrap();
+    let denominator = d_init
+        .checked_mul(ann.checked_sub(1)?.into())
+        .unwrap()
+        .checked_add(
+            d_prod
+                .checked_mul((n_coins.checked_add(1u128.into()).unwrap()).into())
+                .unwrap(),
+        )
+        .unwrap();
+    Some(numerator.checked_div(denominator).unwrap())
+}
+
 /// Calculates the new pool amount given the current pools and swap size.
 pub fn calculate_stableswap_y(
     offer_pool: Decimal256,
@@ -151,6 +240,36 @@
     Err(ContractError::ConvergeError {})
 }
 
+/// Computes the amount of pool tokens to mint after a deposit.
+#[allow(clippy::unwrap_used, clippy::too_many_arguments)]
+pub fn compute_lp_mint_amount_for_stableswap_deposit(
+    amp_factor: &u64,
+    deposit_amount_a: Uint128,
+    deposit_amount_b: Uint128,
+    swap_amount_a: Uint128,
+    swap_amount_b: Uint128,
+    pool_token_supply: Uint128,
+) -> Option<Uint128> {
+    // Initial invariant
+    let d_0 = compute_d(amp_factor, swap_amount_a, swap_amount_b)?;
+    let new_balances = [
+        swap_amount_a.checked_add(deposit_amount_a).unwrap(),
+        swap_amount_b.checked_add(deposit_amount_b).unwrap(),
+    ];
+    // Invariant after change
+    let d_1 = compute_d(amp_factor, new_balances[0], new_balances[1])?;
+    if d_1 <= d_0 {
+        None
+    } else {
+        let amount = Uint512::from(pool_token_supply)
+            .checked_mul(d_1.checked_sub(d_0).unwrap())
+            .unwrap()
+            .checked_div(d_0)
+            .unwrap();
+        Some(Uint128::try_from(amount).unwrap())
+    }
+}
+
 pub fn compute_swap(
     offer_pool: Uint128,
     ask_pool: Uint128,

contracts/liquidity_hub/pool-network/terraswap_pair/src/lib.rs

@@ -7,10 +7,9 @@ pub mod state;
 mod error;
 mod helpers;
 mod math;
+mod migrations;
 mod queries;
 mod response;
-
-mod migrations;
 #[cfg(test)]
 #[cfg(not(target_arch = "wasm32"))]
 pub mod tests;

scripts/deployment/deploy_env/mainnets/terra.env

@@ -1,4 +1,4 @@
 export CHAIN_ID="phoenix-1"
 export DENOM="uluna"
 export BINARY="terrad"
-export RPC="https://ww-terra-rpc.polkachu.com:443"
+export RPC="https://rpc.lavenderfive.com:443/terra2"