Calculate min and max rates in buy quote

3 files changed, 70 insertions, 33 deletions

diff --git a/packages/asset-buyer/src/utils/buy_quote_calculator.ts b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
index e05ab1e55..52cecf8ad 100644
--- a/packages/asset-buyer/src/utils/buy_quote_calculator.ts
+++ b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
@@ -1,5 +1,6 @@
 import { marketUtils } from '@0xproject/order-utils';
 import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
 
 import { constants } from '../constants';
 import { AssetBuyerError, AssetBuyerOrdersAndFillableAmounts, BuyQuote } from '../types';
@@ -18,41 +19,64 @@ export const buyQuoteCalculator = {
             remainingFillableFeeAmounts,
         } = ordersAndFillableAmounts;
         const slippageBufferAmount = assetBuyAmount.mul(slippagePercentage).round();
-        const { resultOrders, remainingFillAmount } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(
-            orders,
-            assetBuyAmount,
-            {
-                remainingFillableMakerAssetAmounts,
-                slippageBufferAmount,
-            },
-        );
+        const {
+            resultOrders,
+            remainingFillAmount,
+            ordersRemainingFillableMakerAssetAmounts,
+        } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(orders, assetBuyAmount, {
+            remainingFillableMakerAssetAmounts,
+            slippageBufferAmount,
+        });
         if (remainingFillAmount.gt(constants.ZERO_AMOUNT)) {
             throw new Error(AssetBuyerError.InsufficientAssetLiquidity);
         }
         // TODO: optimization
         // update this logic to find the minimum amount of feeOrders to cover the worst case as opposed to
         // finding order that cover all fees, this will help with estimating ETH and minimizing gas usage
-        const { resultFeeOrders, remainingFeeAmount } = marketUtils.findFeeOrdersThatCoverFeesForTargetOrders(
-            resultOrders,
-            feeOrders,
-            {
-                remainingFillableMakerAssetAmounts,
-                remainingFillableFeeAmounts,
-            },
-        );
+        const {
+            resultFeeOrders,
+            remainingFeeAmount,
+            feeOrdersRemainingFillableMakerAssetAmounts,
+        } = marketUtils.findFeeOrdersThatCoverFeesForTargetOrders(resultOrders, feeOrders, {
+            remainingFillableMakerAssetAmounts,
+            remainingFillableFeeAmounts,
+        });
         if (remainingFeeAmount.gt(constants.ZERO_AMOUNT)) {
             throw new Error(AssetBuyerError.InsufficientZrxLiquidity);
         }
         const assetData = orders[0].makerAssetData;
-        // TODO: critical
+
         // calculate minRate and maxRate by calculating min and max eth usage and then dividing into
         // assetBuyAmount to get assetData / WETH, needs to take into account feePercentage as well
+        // minEthAmount = (sum(takerAssetAmount[i]) until sum(makerAssetAmount[i]) >= assetBuyAmount ) * (1 + feePercentage)
+        // maxEthAmount = (sum(takerAssetAmount[i]) until i == orders.length) * (1 + feePercentage)
+        const allOrders = _.concat(resultOrders, resultFeeOrders);
+        const allRemainingAmounts = _.concat(
+            ordersRemainingFillableMakerAssetAmounts,
+            feeOrdersRemainingFillableMakerAssetAmounts,
+        );
+        let minEthAmount = constants.ZERO_AMOUNT;
+        let maxEthAmount = constants.ZERO_AMOUNT;
+        let cumulativeMakerAmount = constants.ZERO_AMOUNT;
+        _.forEach(allOrders, (order, index) => {
+            const remainingFillableMakerAssetAmount = allRemainingAmounts[index];
+            const orderRate = order.takerAssetAmount.div(order.makerAssetAmount);
+            const claimableTakerAssetAmount = orderRate.mul(remainingFillableMakerAssetAmount);
+            // taker asset is always assumed to be WETH
+            maxEthAmount = maxEthAmount.plus(claimableTakerAssetAmount);
+            if (cumulativeMakerAmount.lessThan(assetBuyAmount)) {
+                minEthAmount = minEthAmount.plus(claimableTakerAssetAmount);
+            }
+            cumulativeMakerAmount = cumulativeMakerAmount.plus(remainingFillableMakerAssetAmount);
+        });
+        const feeAdjustedMinRate = minEthAmount.mul(feePercentage + 1).div(assetBuyAmount);
+        const feeAdjustedMaxRate = minEthAmount.mul(feePercentage + 1).div(assetBuyAmount);
         return {
             assetData,
             orders: resultOrders,
             feeOrders: resultFeeOrders,
-            minRate: constants.ZERO_AMOUNT,
-            maxRate: constants.ZERO_AMOUNT,
+            minRate: feeAdjustedMinRate,
+            maxRate: feeAdjustedMaxRate,
             assetBuyAmount,
             feePercentage,
         };
diff --git a/packages/order-utils/src/market_utils.ts b/packages/order-utils/src/market_utils.ts
index 4a664cb14..ed6af7d85 100644
--- a/packages/order-utils/src/market_utils.ts
+++ b/packages/order-utils/src/market_utils.ts
@@ -51,17 +51,23 @@ export const marketUtils = {
         // iterate through the orders input from left to right until we have enough makerAsset to fill totalFillAmount
         const result = _.reduce(
             orders,
-            ({ resultOrders, remainingFillAmount }, order, index) => {
+            ({ resultOrders, remainingFillAmount, ordersRemainingFillableMakerAssetAmounts }, order, index) => {
                 if (remainingFillAmount.lessThanOrEqualTo(constants.ZERO_AMOUNT)) {
-                    return { resultOrders, remainingFillAmount: constants.ZERO_AMOUNT };
+                    return {
+                        resultOrders,
+                        remainingFillAmount: constants.ZERO_AMOUNT,
+                        ordersRemainingFillableMakerAssetAmounts,
+                    };
                 } else {
                     const makerAssetAmountAvailable = remainingFillableMakerAssetAmounts[index];
+                    const shouldIncludeOrder = makerAssetAmountAvailable.gt(constants.ZERO_AMOUNT);
                     // if there is no makerAssetAmountAvailable do not append order to resultOrders
                     // if we have exceeded the total amount we want to fill set remainingFillAmount to 0
                     return {
-                        resultOrders: makerAssetAmountAvailable.gt(constants.ZERO_AMOUNT)
-                            ? _.concat(resultOrders, order)
-                            : resultOrders,
+                        resultOrders: shouldIncludeOrder ? _.concat(resultOrders, order) : resultOrders,
+                        ordersRemainingFillableMakerAssetAmounts: shouldIncludeOrder
+                            ? _.concat(ordersRemainingFillableMakerAssetAmounts, makerAssetAmountAvailable)
+                            : ordersRemainingFillableMakerAssetAmounts,
                         remainingFillAmount: BigNumber.max(
                             constants.ZERO_AMOUNT,
                             remainingFillAmount.minus(makerAssetAmountAvailable),
@@ -69,7 +75,11 @@ export const marketUtils = {
                     };
                 }
             },
-            { resultOrders: [] as T[], remainingFillAmount: totalFillAmount },
+            {
+                resultOrders: [] as T[],
+                remainingFillAmount: totalFillAmount,
+                ordersRemainingFillableMakerAssetAmounts: [] as BigNumber[],
+            },
         );
         return result;
     },
@@ -133,17 +143,18 @@ export const marketUtils = {
             },
             constants.ZERO_AMOUNT,
         );
-        const { resultOrders, remainingFillAmount } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(
-            feeOrders,
-            totalFeeAmount,
-            {
-                remainingFillableMakerAssetAmounts: remainingFillableFeeAmounts,
-                slippageBufferAmount,
-            },
-        );
+        const {
+            resultOrders,
+            remainingFillAmount,
+            ordersRemainingFillableMakerAssetAmounts,
+        } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(feeOrders, totalFeeAmount, {
+            remainingFillableMakerAssetAmounts: remainingFillableFeeAmounts,
+            slippageBufferAmount,
+        });
         return {
             resultFeeOrders: resultOrders,
             remainingFeeAmount: remainingFillAmount,
+            feeOrdersRemainingFillableMakerAssetAmounts: ordersRemainingFillableMakerAssetAmounts,
         };
         // TODO: add more orders here to cover rounding
         // https://github.com/0xProject/0x-protocol-specification/blob/master/v2/forwarding-contract-specification.md#over-buying-zrx
diff --git a/packages/order-utils/src/types.ts b/packages/order-utils/src/types.ts
index 09292e557..a843efaa4 100644
--- a/packages/order-utils/src/types.ts
+++ b/packages/order-utils/src/types.ts
@@ -72,10 +72,12 @@ export interface FindFeeOrdersThatCoverFeesForTargetOrdersOpts {
 
 export interface FeeOrdersAndRemainingFeeAmount<T> {
     resultFeeOrders: T[];
+    feeOrdersRemainingFillableMakerAssetAmounts: BigNumber[];
     remainingFeeAmount: BigNumber;
 }
 
 export interface OrdersAndRemainingFillAmount<T> {
     resultOrders: T[];
+    ordersRemainingFillableMakerAssetAmounts: BigNumber[];
     remainingFillAmount: BigNumber;
 }