typescript source code of balancerV1

import { BigNumber } from "ethers";
import { BaseProvider } from "@ethersproject/providers";
import { BigNumber as BigNumberJS } from "bignumber.js";

import {
  SOR,
} from "@balancer-labs/sor";
import { ether, gWei, preciseDiv, preciseMul } from "@setprotocol/index-coop-contracts/dist/utils/common";

import { ZERO } from "../../../utils/constants";
import { ExchangeQuote, exchanges, Address } from "../../types";
import DEPENDENCY from "../../dependencies";

const {
  ETH_ADDRESS,
} = DEPENDENCY;

// Usage note, targetPriceImpact should be the impact including fees! Balancer pool fees can change and it's not easy to extract from the data
// we have so put in a number that is net of fees.
export async function getBalancerV1Quote(provider: BaseProvider, tokenAddress: Address, targetPriceImpact: BigNumber): Promise<ExchangeQuote> {
  const sor = new SOR(
    provider,
    toBigNumberJS(gWei(100)),
    3,      // Max 3 pools used
    1,      // ChainId = mainnet (1)
    "https://storageapi.fleek.co/balancer-bucket/balancer-exchange/pools"
  );
  await sor.fetchPools();
  await sor.setCostOutputToken(tokenAddress);   // Set cost to limit small trades

  const inputAmount = toBigNumberJS(ether(2));
  const [
    ,
    returnAmountV1,
    marketSpV1Scaled,
  ] = await sor.getSwaps(
    ETH_ADDRESS.toLowerCase(),
    tokenAddress.toLowerCase(),
    "swapExactIn",
    inputAmount
  );

  if (!returnAmountV1.eq(0)) {
    const effectivePrice = inputAmount.div(returnAmountV1);

    const priceImpact = ether(effectivePrice.div(marketSpV1Scaled.div(10 ** 18)).toNumber()).sub(ether(1));
    const priceImpactRatio = preciseDiv(targetPriceImpact, priceImpact.mul(100));

    return {
      exchange: exchanges.BALANCER,
      size: preciseMul(fromBigNumberJS(returnAmountV1), priceImpactRatio).toString(),
      data: "0x",
    } as ExchangeQuote;
  }

  return {
    exchange: exchanges.BALANCER,
    size: ZERO.toString(),
    data: "0x",
  } as ExchangeQuote;
}

function toBigNumberJS(value: BigNumber): BigNumberJS {
  return new BigNumberJS(value.toString());
}

function fromBigNumberJS(value: BigNumberJS): BigNumber {
  return BigNumber.from(value.toString());
}