addressed reviews and light refactor

added comments to types and refactored some naming

packages/asset-buyer/src/utils/affiliate_fee_utils.ts

@@ -0,0 +1,24 @@
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
+
+import { SwapQuote, SwapQuoteInfo } from '../types';
+
+export const affiliateFeeUtils = {
+    getSwapQuoteWithAffiliateFee(quote: SwapQuote, feePercentage: number): SwapQuote {
+        const newQuote = _.clone(quote);
+        newQuote.bestCaseQuoteInfo = getSwapQuoteInfoWithAffiliateFee(newQuote.bestCaseQuoteInfo, feePercentage);
+        newQuote.worstCaseQuoteInfo = getSwapQuoteInfoWithAffiliateFee(newQuote.worstCaseQuoteInfo, feePercentage);
+        return newQuote;
+    },
+};
+
+const getSwapQuoteInfoWithAffiliateFee = (quoteInfo: SwapQuoteInfo, feePercentage: number): SwapQuoteInfo => {
+    const newQuoteInfo = _.clone(quoteInfo);
+    const affiliateFeeAmount = newQuoteInfo.takerTokenAmount
+        .multipliedBy(feePercentage)
+        .integerValue(BigNumber.ROUND_CEIL);
+    const newFeeAmount = newQuoteInfo.feeTakerTokenAmount.plus(affiliateFeeAmount);
+    newQuoteInfo.feeTakerTokenAmount = newFeeAmount;
+    newQuoteInfo.totalTakerTokenAmount = newFeeAmount.plus(newQuoteInfo.takerTokenAmount);
+    return newQuoteInfo;
+};