2023-11-olympus-amplification parameter update

readme

setup an eth forkable rpc
put this file in  test/
run : forge test --mt testHash_IncorrectCalculationIfAmplificationParameterUpdate -vv

testAmplificationParameterUpdate.sol

pragma solidity 0.8.15;

import "forge-std/Test.sol";
import {IStablePool} from "src/libraries/Balancer/interfaces/IStablePool.sol";
import {IVault} from "src/libraries/Balancer/interfaces/IVault.sol";
import {FullMath} from "src/libraries/FullMath.sol";
import {StableMath} from "src/libraries/Balancer/math/StableMath.sol";
import {IVault} from "src/libraries/Balancer/interfaces/IVault.sol";
import {IBasePool} from "src/libraries/Balancer/interfaces/IBasePool.sol";
import {IWeightedPool} from "src/libraries/Balancer/interfaces/IWeightedPool.sol";
import {IStablePool} from "src/libraries/Balancer/interfaces/IStablePool.sol";
import {VaultReentrancyLib} from "src/libraries/Balancer/contracts/VaultReentrancyLib.sol";
import {LogExpMath} from "src/libraries/Balancer/math/LogExpMath.sol";
import {FixedPoint} from "src/libraries/Balancer/math/FixedPoint.sol";

interface IStablePoolWithAmp is IStablePool {
    function getAmplificationParameter()
        external
        view
        returns (uint amp, bool isUpdating, uint precision);
}

contract PriceTest is Test {
    using FullMath for uint256;

    function testHash_IncorrectCalculationIfAmplificationParameterUpdate() public {
        IVault balVault = IVault(0xBA12222222228d8Ba445958a75a0704d566BF2C8);
        IStablePoolWithAmp pool = IStablePoolWithAmp(0x3dd0843A028C86e0b760b1A76929d1C5Ef93a2dd);
        
        // auraBal pool
        // fork block 15719717. amp update is started here
        vm.rollFork(15719717);
        (, uint cachedAmpFactor) = pool.getLastInvariant();
        {
            (, bool isUpdating, ) = pool.getAmplificationParameter();
             assert(isUpdating == true);
        }

        // if no join actions are performed, the cachedAmpFactor will not be updated
        vm.rollFork(15769772);
        assert(block.number == 15769772);

        bytes32 poolId = pool.getPoolId();
        {
            (address[] memory tokens_, , ) = balVault.getPoolTokens(poolId);
            // token0 is 80bal20eth lp token
            assert(tokens_[0] == 0x5c6Ee304399DBdB9C8Ef030aB642B10820DB8F56);
        }

        uint actualAmpFactor;
        (actualAmpFactor, , ) = pool.getAmplificationParameter();

        (, uint[] memory balances_, ) = balVault.getPoolTokens(poolId);
        uint256[] memory scalingFactors = pool.getScalingFactors();
        {
            
            uint256 len = scalingFactors.length;
            for (uint256 i; i < len; ++i) {
                balances_[i] = FixedPoint.mulDown(balances_[i], scalingFactors[i]);
            }
        }

        // lookup token auraBal and destination token lp token
        uint destinationTokenIndex = 0;
        uint lookupTokenIndex = 1;

        {
            console.log("calculation with previous amp factor");
            uint lookupTokensPerDestinationToken;
            lookupTokensPerDestinationToken = StableMath._calcOutGivenIn(
                cachedAmpFactor,
                balances_,
                destinationTokenIndex,
                lookupTokenIndex,
                1e18,
                StableMath._calculateInvariant(cachedAmpFactor, balances_)
            );

            // Downscale the amount to token decimals
            lookupTokensPerDestinationToken = FixedPoint.divDown(
                lookupTokensPerDestinationToken,
                scalingFactors[lookupTokenIndex]
            );

            uint outputDecimals = 8;

            lookupTokensPerDestinationToken =
                (lookupTokensPerDestinationToken * 10 ** outputDecimals) /
                1e18;

            // bal lp token price https://thegraph.com/hosted-service/subgraph/balancer-labs/balancer-v2
            uint destinationTokenPrice = 1352719207;
            console.log("bal lp price", destinationTokenPrice);
            uint lookupTokenPrice;

            lookupTokenPrice = destinationTokenPrice.mulDiv(
                10 ** outputDecimals,
                lookupTokensPerDestinationToken
            );

            console.log("aurabal price", lookupTokenPrice);
        }

        {
            console.log("calculation with updated amp factor");
            uint lookupTokensPerDestinationToken;
            lookupTokensPerDestinationToken = StableMath._calcOutGivenIn(
                actualAmpFactor,
                balances_,
                destinationTokenIndex,
                lookupTokenIndex,
                1e18,
                StableMath._calculateInvariant(actualAmpFactor, balances_)
            );

            // Downscale the amount to token decimals
            lookupTokensPerDestinationToken = FixedPoint.divDown(
                lookupTokensPerDestinationToken,
                scalingFactors[lookupTokenIndex]
            );

            uint outputDecimals = 8;

            lookupTokensPerDestinationToken =
                (lookupTokensPerDestinationToken * 10 ** outputDecimals) /
                1e18;

            // bal lp token price https://thegraph.com/hosted-service/subgraph/balancer-labs/balancer-v2
            uint destinationTokenPrice = 1352719207;
            console.log("bal lp price", destinationTokenPrice);
            uint lookupTokenPrice;

            lookupTokenPrice = destinationTokenPrice.mulDiv(
                10 ** outputDecimals,
                lookupTokensPerDestinationToken
            );

            console.log("aurabal price", lookupTokenPrice);
        }
    }
}