import { Currency, CurrencyAmount } from "@uniswap/sdk-core";
import JSBI from "jsbi";
import { MIN_ETH } from "../constants/misc";

/**
 * Given some token amount, return the max that can be spent of it
 * @param currencyAmount to return max of
 */
export function maxAmountSpend(
  currencyAmount?: CurrencyAmount<Currency>
): CurrencyAmount<Currency> | undefined {
  if (!currencyAmount) return undefined;
  if (currencyAmount.currency.isNative) {
    if (JSBI.greaterThan(currencyAmount.quotient, MIN_ETH)) {
      return CurrencyAmount.fromRawAmount(
        currencyAmount.currency,
        JSBI.subtract(currencyAmount.quotient, MIN_ETH)
      );
    } else {
      return CurrencyAmount.fromRawAmount(
        currencyAmount.currency,
        JSBI.BigInt(0)
      );
    }
  }
  return currencyAmount;
}