@indigo-labs/indigo-sdk/src/utils/indigo-helpers.ts

Indigo SDK for interacting with Indigo endpoints via lucid-evolution

import {
  Rational,
  rationalFloor,
  rationalFromInt,
  rationalMul,
} from '../types/rational';

export function calculateFeeFromRatio(
  feeRatio: Rational,
  amount: bigint,
): bigint {
  if (amount < 0) {
    return 0n;
  }

  return rationalFloor(rationalMul(rationalFromInt(amount), feeRatio));
}