pre flight checks for paying gas in ERC20 token

preFlight.js

const appRoot = require("app-root-path");
var log = require(`${appRoot}/config/winston`).logger(module);
const config = require(`${appRoot}/config`);
const cache = require(`${appRoot}/src/services/caching`);
const ethers = require("ethers");
const {
  getGasPriceKey,
} = require(`${appRoot}/src/controllers/utils/cache-utils`);
const TOKEN_GAS_PRICE_THRESHOLD_PERCENTAGE =
  config.TOKEN_GAS_PRICE_THRESHOLD_PERCENTAGE;

const getPreFlightChecks = async (
  networkId,
  oracleAggregatorContract,
  forwardRequest
) => {
  let result = {};
  result.readyToPayGasInTokens = false;
  try {
    let gasPriceFromCache = await cache.get(
      getGasPriceKey(networkId, config.networksGasPriceType[networkId])
    );
    let tokenAddress = forwardRequest.token;
    const tokenGasPriceFromRequest = ethers.BigNumber.from(
      forwardRequest.tokenGasPrice
    );
    const tokenPriceCurrent = await oracleAggregatorContract.getTokenPrice(
      tokenAddress
    );
    const tokenOracleDecimals = await oracleAggregatorContract.getTokenOracleDecimals(
      tokenAddress
    );

    /* should probably assume use of high gas price and calculate from different sources on the go (upvest,gasstation,etherscan) and avergae out 
     same for the oracle vs token price fetch apis - coingecko etc 
     add robustness for calcs 
     //todo
   */

    const gasPrice = ethers.BigNumber.from(
      ethers.utils.parseUnits(gasPriceFromCache.toString(), "wei").toString()
    );
    const tokenGasPriceCurrent = ethers.BigNumber.from(gasPrice)
      .mul(ethers.BigNumber.from(10).pow(tokenOracleDecimals))
      .div(tokenPriceCurrent);

    if (tokenGasPriceCurrent && tokenPriceCurrent && tokenOracleDecimals) {
      log.info(`token price ${tokenPriceCurrent.toString()}`);
      log.info(`token oracle decimals ${tokenOracleDecimals.toString()}`);
      log.info(`token gas price ${tokenGasPriceCurrent.toString()}`);

      var minimumTokenGasPriceAccepted = ethers.BigNumber.from(
        TOKEN_GAS_PRICE_THRESHOLD_PERCENTAGE
      )
        .mul(ethers.BigNumber.from(tokenGasPriceCurrent))
        .div(ethers.BigNumber.from(100));

      if (tokenGasPriceFromRequest.lte(minimumTokenGasPriceAccepted)) {
        log.info("Not favorable to process this transaction");
        result.errorMessage =
          "$token/ETH pair price has dropped beyond threshold";
      } else {
        result.readyToPayGasInTokens = true;
      }
    }
  } catch (error) {
    log.info("Error while getting data points for pre flight checks");
    result.errorMessage = error.toString();
    log.error(error);
  }
  log.info(`ready to pay in ERC20 tokens? ${result.readyToPayGasInTokens}`);
  return result;
};

module.exports = { getPreFlightChecks };