Merge development

6 files changed, 252 insertions, 104 deletions

diff --git a/packages/order-utils/src/index.ts b/packages/order-utils/src/index.ts
index 638126af6..1f393b0c4 100644
--- a/packages/order-utils/src/index.ts
+++ b/packages/order-utils/src/index.ts
@@ -4,6 +4,8 @@ export { generatePseudoRandomSalt } from './salt';
 export { assetDataUtils } from './asset_data_utils';
 export { eip712Utils } from './eip712_utils';
 export { marketUtils } from './market_utils';
+export { rateUtils } from './rate_utils';
+export { sortingUtils } from './sorting_utils';
 
 export { OrderStateUtils } from './order_state_utils';
 export { AbstractBalanceAndProxyAllowanceFetcher } from './abstract/abstract_balance_and_proxy_allowance_fetcher';
diff --git a/packages/order-utils/src/market_utils.ts b/packages/order-utils/src/market_utils.ts
index 681059ddf..a0a827546 100644
--- a/packages/order-utils/src/market_utils.ts
+++ b/packages/order-utils/src/market_utils.ts
@@ -1,46 +1,51 @@
 import { schemas } from '@0xproject/json-schemas';
-import { SignedOrder } from '@0xproject/types';
+import { Order } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 import * as _ from 'lodash';
 
 import { assert } from './assert';
 import { constants } from './constants';
+import { FindFeeOrdersThatCoverFeesForTargetOrdersOpts, FindOrdersThatCoverMakerAssetFillAmountOpts } from './types';
 
 export const marketUtils = {
     /**
-     * Takes an array of orders and returns a subset of those orders that has enough makerAssetAmount (taking into account on-chain balances,
-     * allowances, and partial fills) in order to fill the input makerAssetFillAmount plus slippageBufferAmount. Iterates from first order to last.
+     * Takes an array of orders and returns a subset of those orders that has enough makerAssetAmount
+     * in order to fill the input makerAssetFillAmount plus slippageBufferAmount. Iterates from first order to last order.
      * Sort the input by ascending rate in order to get the subset of orders that will cost the least ETH.
-     * @param   signedOrders                        An array of objects that conform to the SignedOrder interface. All orders should specify the same makerAsset.
-     *                                              All orders should specify WETH as the takerAsset.
-     * @param   remainingFillableMakerAssetAmounts  An array of BigNumbers corresponding to the signedOrders parameter.
-     *                                              You can use OrderStateUtils @0xproject/order-utils to perform blockchain lookups
-     *                                              for these values.
-     * @param   makerAssetFillAmount                The amount of makerAsset desired to be filled.
-     * @param   slippageBufferAmount                An additional amount of makerAsset to be covered by the result in case of trade collisions or partial fills.
+     * @param   orders                      An array of objects that extend the Order interface. All orders should specify the same makerAsset.
+     *                                      All orders should specify WETH as the takerAsset.
+     * @param   makerAssetFillAmount        The amount of makerAsset desired to be filled.
+     * @param   opts                        Optional arguments this function accepts.
      * @return  Resulting orders and remaining fill amount that could not be covered by the input.
      */
-    findOrdersThatCoverMakerAssetFillAmount(
-        signedOrders: SignedOrder[],
-        remainingFillableMakerAssetAmounts: BigNumber[],
+    findOrdersThatCoverMakerAssetFillAmount<T extends Order>(
+        orders: T[],
         makerAssetFillAmount: BigNumber,
-        slippageBufferAmount: BigNumber = constants.ZERO_AMOUNT,
-    ): { resultOrders: SignedOrder[]; remainingFillAmount: BigNumber } {
-        assert.doesConformToSchema('signedOrders', signedOrders, schemas.signedOrdersSchema);
+        opts?: FindOrdersThatCoverMakerAssetFillAmountOpts,
+    ): { resultOrders: T[]; remainingFillAmount: BigNumber } {
+        assert.doesConformToSchema('orders', orders, schemas.ordersSchema);
+        assert.isValidBaseUnitAmount('makerAssetFillAmount', makerAssetFillAmount);
+        // try to get remainingFillableMakerAssetAmounts from opts, if it's not there, use makerAssetAmount values from orders
+        const remainingFillableMakerAssetAmounts = _.get(
+            opts,
+            'remainingFillableMakerAssetAmounts',
+            _.map(orders, order => order.makerAssetAmount),
+        ) as BigNumber[];
         _.forEach(remainingFillableMakerAssetAmounts, (amount, index) =>
             assert.isValidBaseUnitAmount(`remainingFillableMakerAssetAmount[${index}]`, amount),
         );
-        assert.isValidBaseUnitAmount('makerAssetFillAmount', makerAssetFillAmount);
-        assert.isValidBaseUnitAmount('slippageBufferAmount', slippageBufferAmount);
         assert.assert(
-            signedOrders.length === remainingFillableMakerAssetAmounts.length,
-            'Expected signedOrders.length to equal remainingFillableMakerAssetAmounts.length',
+            orders.length === remainingFillableMakerAssetAmounts.length,
+            'Expected orders.length to equal opts.remainingFillableMakerAssetAmounts.length',
         );
+        // try to get slippageBufferAmount from opts, if it's not there, default to 0
+        const slippageBufferAmount = _.get(opts, 'slippageBufferAmount', constants.ZERO_AMOUNT) as BigNumber;
+        assert.isValidBaseUnitAmount('opts.slippageBufferAmount', slippageBufferAmount);
         // calculate total amount of makerAsset needed to be filled
         const totalFillAmount = makerAssetFillAmount.plus(slippageBufferAmount);
-        // iterate through the signedOrders input from left to right until we have enough makerAsset to fill totalFillAmount
+        // iterate through the orders input from left to right until we have enough makerAsset to fill totalFillAmount
         const result = _.reduce(
-            signedOrders,
+            orders,
             ({ resultOrders, remainingFillAmount }, order, index) => {
                 if (remainingFillAmount.lessThanOrEqualTo(constants.ZERO_AMOUNT)) {
                     return { resultOrders, remainingFillAmount: constants.ZERO_AMOUNT };
@@ -59,55 +64,61 @@ export const marketUtils = {
                     };
                 }
             },
-            { resultOrders: [] as SignedOrder[], remainingFillAmount: totalFillAmount },
+            { resultOrders: [] as T[], remainingFillAmount: totalFillAmount },
         );
         return result;
     },
     /**
-     * Takes an array of orders and an array of feeOrders. Returns a subset of the feeOrders that has enough ZRX (taking into account
-     * on-chain balances, allowances, and partial fills) in order to fill the takerFees required by signedOrders plus a
-     * slippageBufferAmount. Iterates from first feeOrder to last. Sort the feeOrders by ascending rate in order to get the subset of
+     * Takes an array of orders and an array of feeOrders. Returns a subset of the feeOrders that has enough ZRX
+     * in order to fill the takerFees required by orders plus a slippageBufferAmount.
+     * Iterates from first feeOrder to last. Sort the feeOrders by ascending rate in order to get the subset of
      * feeOrders that will cost the least ETH.
-     * @param   signedOrders                        An array of objects that conform to the SignedOrder interface. All orders should specify ZRX as
-     *                                              the makerAsset and WETH as the takerAsset.
-     * @param   remainingFillableMakerAssetAmounts  An array of BigNumbers corresponding to the signedOrders parameter.
-     *                                              You can use OrderStateUtils @0xproject/order-utils to perform blockchain lookups
-     *                                              for these values.
-     * @param   signedFeeOrders                     An array of objects that conform to the SignedOrder interface. All orders should specify ZRX as
-     *                                              the makerAsset and WETH as the takerAsset.
-     * @param   remainingFillableFeeAmounts         An array of BigNumbers corresponding to the signedFeeOrders parameter.
-     *                                              You can use OrderStateUtils @0xproject/order-utils to perform blockchain lookups
-     *                                              for these values.
-     * @param   slippageBufferAmount                An additional amount of fee to be covered by the result in case of trade collisions or partial fills.
+     * @param   orders      An array of objects that extend the Order interface. All orders should specify ZRX as
+     *                      the makerAsset and WETH as the takerAsset.
+     * @param   feeOrders   An array of objects that extend the Order interface. All orders should specify ZRX as
+     *                      the makerAsset and WETH as the takerAsset.
+     * @param   opts        Optional arguments this function accepts.
      * @return  Resulting orders and remaining fee amount that could not be covered by the input.
      */
-    findFeeOrdersThatCoverFeesForTargetOrders(
-        signedOrders: SignedOrder[],
-        remainingFillableMakerAssetAmounts: BigNumber[],
-        signedFeeOrders: SignedOrder[],
-        remainingFillableFeeAmounts: BigNumber[],
-        slippageBufferAmount: BigNumber = constants.ZERO_AMOUNT,
-    ): { resultOrders: SignedOrder[]; remainingFeeAmount: BigNumber } {
-        assert.doesConformToSchema('signedOrders', signedOrders, schemas.signedOrdersSchema);
+    findFeeOrdersThatCoverFeesForTargetOrders<T extends Order>(
+        orders: T[],
+        feeOrders: T[],
+        opts?: FindFeeOrdersThatCoverFeesForTargetOrdersOpts,
+    ): { resultOrders: T[]; remainingFeeAmount: BigNumber } {
+        assert.doesConformToSchema('orders', orders, schemas.ordersSchema);
+        assert.doesConformToSchema('feeOrders', feeOrders, schemas.ordersSchema);
+        // try to get remainingFillableMakerAssetAmounts from opts, if it's not there, use makerAssetAmount values from orders
+        const remainingFillableMakerAssetAmounts = _.get(
+            opts,
+            'remainingFillableMakerAssetAmounts',
+            _.map(orders, order => order.makerAssetAmount),
+        ) as BigNumber[];
         _.forEach(remainingFillableMakerAssetAmounts, (amount, index) =>
             assert.isValidBaseUnitAmount(`remainingFillableMakerAssetAmount[${index}]`, amount),
         );
-        assert.doesConformToSchema('signedFeeOrders', signedFeeOrders, schemas.signedOrdersSchema);
+        assert.assert(
+            orders.length === remainingFillableMakerAssetAmounts.length,
+            'Expected orders.length to equal opts.remainingFillableMakerAssetAmounts.length',
+        );
+        // try to get remainingFillableFeeAmounts from opts, if it's not there, use makerAssetAmount values from feeOrders
+        const remainingFillableFeeAmounts = _.get(
+            opts,
+            'remainingFillableFeeAmounts',
+            _.map(feeOrders, order => order.makerAssetAmount),
+        ) as BigNumber[];
         _.forEach(remainingFillableFeeAmounts, (amount, index) =>
             assert.isValidBaseUnitAmount(`remainingFillableFeeAmounts[${index}]`, amount),
         );
-        assert.isValidBaseUnitAmount('slippageBufferAmount', slippageBufferAmount);
         assert.assert(
-            signedOrders.length === remainingFillableMakerAssetAmounts.length,
-            'Expected signedOrders.length to equal remainingFillableMakerAssetAmounts.length',
+            feeOrders.length === remainingFillableFeeAmounts.length,
+            'Expected feeOrders.length to equal opts.remainingFillableFeeAmounts.length',
         );
-        assert.assert(
-            signedOrders.length === remainingFillableMakerAssetAmounts.length,
-            'Expected signedFeeOrders.length to equal remainingFillableFeeAmounts.length',
-        );
-        // calculate total amount of ZRX needed to fill signedOrders
+        // try to get slippageBufferAmount from opts, if it's not there, default to 0
+        const slippageBufferAmount = _.get(opts, 'slippageBufferAmount', constants.ZERO_AMOUNT) as BigNumber;
+        assert.isValidBaseUnitAmount('opts.slippageBufferAmount', slippageBufferAmount);
+        // calculate total amount of ZRX needed to fill orders
         const totalFeeAmount = _.reduce(
-            signedOrders,
+            orders,
             (accFees, order, index) => {
                 const makerAssetAmountAvailable = remainingFillableMakerAssetAmounts[index];
                 const feeToFillMakerAssetAmountAvailable = makerAssetAmountAvailable
@@ -118,10 +129,12 @@ export const marketUtils = {
             constants.ZERO_AMOUNT,
         );
         const { resultOrders, remainingFillAmount } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(
-            signedFeeOrders,
-            remainingFillableFeeAmounts,
+            feeOrders,
             totalFeeAmount,
-            slippageBufferAmount,
+            {
+                remainingFillableMakerAssetAmounts: remainingFillableFeeAmounts,
+                slippageBufferAmount,
+            },
         );
         return {
             resultOrders,
diff --git a/packages/order-utils/src/order_state_utils.ts b/packages/order-utils/src/order_state_utils.ts
index cb08c5ae2..a0e24acf0 100644
--- a/packages/order-utils/src/order_state_utils.ts
+++ b/packages/order-utils/src/order_state_utils.ts
@@ -11,6 +11,7 @@ import { BigNumber } from '@0xproject/utils';
 import { AbstractBalanceAndProxyAllowanceFetcher } from './abstract/abstract_balance_and_proxy_allowance_fetcher';
 import { AbstractOrderFilledCancelledFetcher } from './abstract/abstract_order_filled_cancelled_fetcher';
 import { orderHashUtils } from './order_hash';
+import { OrderValidationUtils } from './order_validation_utils';
 import { RemainingFillableCalculator } from './remaining_fillable_calculator';
 import { utils } from './utils';
 
@@ -22,9 +23,16 @@ interface SidedOrderRelevantState {
     traderFeeProxyAllowance: BigNumber;
     filledTakerAssetAmount: BigNumber;
     remainingFillableAssetAmount: BigNumber;
+    isOrderCancelled: boolean;
 }
-
-const ACCEPTABLE_RELATIVE_ROUNDING_ERROR = 0.0001;
+interface OrderValidResult {
+    isValid: true;
+}
+interface OrderInvalidResult {
+    isValid: false;
+    error: ExchangeContractErrs;
+}
+type OrderValidationResult = OrderValidResult | OrderInvalidResult;
 
 export class OrderStateUtils {
     private readonly _balanceAndProxyAllowanceFetcher: AbstractBalanceAndProxyAllowanceFetcher;
@@ -32,64 +40,56 @@ export class OrderStateUtils {
     private static _validateIfOrderIsValid(
         signedOrder: SignedOrder,
         sidedOrderRelevantState: SidedOrderRelevantState,
-    ): void {
+    ): OrderValidationResult {
         const isMakerSide = sidedOrderRelevantState.isMakerSide;
+        if (sidedOrderRelevantState.isOrderCancelled) {
+            return { isValid: false, error: ExchangeContractErrs.OrderCancelled };
+        }
         const availableTakerAssetAmount = signedOrder.takerAssetAmount.minus(
             sidedOrderRelevantState.filledTakerAssetAmount,
         );
         if (availableTakerAssetAmount.eq(0)) {
-            throw new Error(ExchangeContractErrs.OrderRemainingFillAmountZero);
+            return { isValid: false, error: ExchangeContractErrs.OrderRemainingFillAmountZero };
         }
 
         if (sidedOrderRelevantState.traderBalance.eq(0)) {
-            throw new Error(
-                isMakerSide
-                    ? ExchangeContractErrs.InsufficientMakerBalance
-                    : ExchangeContractErrs.InsufficientTakerBalance,
-            );
+            const error = isMakerSide
+                ? ExchangeContractErrs.InsufficientMakerBalance
+                : ExchangeContractErrs.InsufficientTakerBalance;
+            return { isValid: false, error };
         }
         if (sidedOrderRelevantState.traderProxyAllowance.eq(0)) {
-            throw new Error(
-                isMakerSide
-                    ? ExchangeContractErrs.InsufficientMakerAllowance
-                    : ExchangeContractErrs.InsufficientTakerAllowance,
-            );
+            const error = isMakerSide
+                ? ExchangeContractErrs.InsufficientMakerAllowance
+                : ExchangeContractErrs.InsufficientTakerAllowance;
+            return { isValid: false, error };
         }
         if (!signedOrder.makerFee.eq(0)) {
             if (sidedOrderRelevantState.traderFeeBalance.eq(0)) {
-                throw new Error(
-                    isMakerSide
-                        ? ExchangeContractErrs.InsufficientMakerFeeBalance
-                        : ExchangeContractErrs.InsufficientTakerFeeBalance,
-                );
+                const error = isMakerSide
+                    ? ExchangeContractErrs.InsufficientMakerFeeBalance
+                    : ExchangeContractErrs.InsufficientTakerFeeBalance;
+                return { isValid: false, error };
             }
             if (sidedOrderRelevantState.traderFeeProxyAllowance.eq(0)) {
-                throw new Error(
-                    isMakerSide
-                        ? ExchangeContractErrs.InsufficientMakerFeeAllowance
-                        : ExchangeContractErrs.InsufficientTakerFeeAllowance,
-                );
+                const error = isMakerSide
+                    ? ExchangeContractErrs.InsufficientMakerFeeAllowance
+                    : ExchangeContractErrs.InsufficientTakerFeeAllowance;
+                return { isValid: false, error };
             }
         }
-
-        let minFillableTakerAssetAmountWithinNoRoundingErrorRange;
-        if (isMakerSide) {
-            minFillableTakerAssetAmountWithinNoRoundingErrorRange = signedOrder.takerAssetAmount
-                .dividedBy(ACCEPTABLE_RELATIVE_ROUNDING_ERROR)
-                .dividedBy(signedOrder.makerAssetAmount);
-        } else {
-            minFillableTakerAssetAmountWithinNoRoundingErrorRange = signedOrder.makerAssetAmount
-                .dividedBy(ACCEPTABLE_RELATIVE_ROUNDING_ERROR)
-                .dividedBy(signedOrder.takerAssetAmount);
-        }
-
-        if (
-            sidedOrderRelevantState.remainingFillableAssetAmount.lessThan(
-                minFillableTakerAssetAmountWithinNoRoundingErrorRange,
-            )
-        ) {
-            throw new Error(ExchangeContractErrs.OrderFillRoundingError);
+        const remainingTakerAssetAmount = signedOrder.takerAssetAmount.minus(
+            sidedOrderRelevantState.filledTakerAssetAmount,
+        );
+        const isRoundingError = OrderValidationUtils.isRoundingError(
+            remainingTakerAssetAmount,
+            signedOrder.takerAssetAmount,
+            signedOrder.makerAssetAmount,
+        );
+        if (isRoundingError) {
+            return { isValid: false, error: ExchangeContractErrs.OrderFillRoundingError };
         }
+        return { isValid: true };
     }
     /**
      * Instantiate OrderStateUtils
@@ -117,6 +117,7 @@ export class OrderStateUtils {
     public async getOpenOrderStateAsync(signedOrder: SignedOrder): Promise<OrderState> {
         const orderRelevantState = await this.getOpenOrderRelevantStateAsync(signedOrder);
         const orderHash = orderHashUtils.getOrderHashHex(signedOrder);
+        const isOrderCancelled = await this._orderFilledCancelledFetcher.isOrderCancelledAsync(orderHash);
         const sidedOrderRelevantState = {
             isMakerSide: true,
             traderBalance: orderRelevantState.makerBalance,
@@ -125,20 +126,21 @@ export class OrderStateUtils {
             traderFeeProxyAllowance: orderRelevantState.makerFeeProxyAllowance,
             filledTakerAssetAmount: orderRelevantState.filledTakerAssetAmount,
             remainingFillableAssetAmount: orderRelevantState.remainingFillableMakerAssetAmount,
+            isOrderCancelled,
         };
-        try {
-            OrderStateUtils._validateIfOrderIsValid(signedOrder, sidedOrderRelevantState);
+        const orderValidationResult = OrderStateUtils._validateIfOrderIsValid(signedOrder, sidedOrderRelevantState);
+        if (orderValidationResult.isValid) {
             const orderState: OrderStateValid = {
                 isValid: true,
                 orderHash,
                 orderRelevantState,
             };
             return orderState;
-        } catch (err) {
+        } else {
             const orderState: OrderStateInvalid = {
                 isValid: false,
                 orderHash,
-                error: err.message,
+                error: orderValidationResult.error,
             };
             return orderState;
         }
@@ -279,6 +281,7 @@ export class OrderStateUtils {
             traderFeeProxyAllowance,
             filledTakerAssetAmount,
             remainingFillableAssetAmount,
+            isOrderCancelled,
         };
         return sidedOrderRelevantState;
     }
diff --git a/packages/order-utils/src/rate_utils.ts b/packages/order-utils/src/rate_utils.ts
new file mode 100644
index 000000000..c9ca72c59
--- /dev/null
+++ b/packages/order-utils/src/rate_utils.ts
@@ -0,0 +1,48 @@
+import { schemas } from '@0xproject/json-schemas';
+import { Order } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+
+import { assert } from './assert';
+import { constants } from './constants';
+
+export const rateUtils = {
+    /**
+     * Takes an order and calculates the fee adjusted rate (takerAsset/makerAsset) by calculating how much takerAsset
+     * is required to cover the fees (feeRate * takerFee), adding the takerAssetAmount and dividing by makerAssetAmount
+     * @param   order       An object that conforms to the order interface
+     * @param   feeRate     The market rate of ZRX denominated in takerAssetAmount
+     *                      (ex. feeRate is 0.1 takerAsset/ZRX if it takes 1 unit of takerAsset to buy 10 ZRX)
+     *                      Defaults to 0
+     * @return  The rate (takerAsset/makerAsset) of the order adjusted for fees
+     */
+    getFeeAdjustedRateOfOrder(order: Order, feeRate: BigNumber = constants.ZERO_AMOUNT): BigNumber {
+        assert.doesConformToSchema('order', order, schemas.orderSchema);
+        assert.isBigNumber('feeRate', feeRate);
+        assert.assert(
+            feeRate.gte(constants.ZERO_AMOUNT),
+            `Expected feeRate: ${feeRate} to be greater than or equal to 0`,
+        );
+        const takerAssetAmountNeededToPayForFees = order.takerFee.mul(feeRate);
+        const totalTakerAssetAmount = takerAssetAmountNeededToPayForFees.plus(order.takerAssetAmount);
+        const rate = totalTakerAssetAmount.div(order.makerAssetAmount);
+        return rate;
+    },
+    /**
+     * Takes a fee order (makerAssetData corresponds to ZRX and takerAssetData corresponds to WETH) and calculates
+     * the fee adjusted rate (WETH/ZRX) by dividing the takerAssetAmount by the makerAmount minus the takerFee
+     * @param   feeOrder    An object that conforms to the order interface
+     * @return  The rate (WETH/ZRX) of the fee order adjusted for fees
+     */
+    getFeeAdjustedRateOfFeeOrder(feeOrder: Order): BigNumber {
+        assert.doesConformToSchema('feeOrder', feeOrder, schemas.orderSchema);
+        const zrxAmountAfterFees = feeOrder.makerAssetAmount.sub(feeOrder.takerFee);
+        assert.assert(
+            zrxAmountAfterFees.greaterThan(constants.ZERO_AMOUNT),
+            `Expected takerFee: ${JSON.stringify(feeOrder.takerFee)} to be less than makerAssetAmount: ${JSON.stringify(
+                feeOrder.makerAssetAmount,
+            )}`,
+        );
+        const rate = feeOrder.takerAssetAmount.div(zrxAmountAfterFees);
+        return rate;
+    },
+};
diff --git a/packages/order-utils/src/sorting_utils.ts b/packages/order-utils/src/sorting_utils.ts
new file mode 100644
index 000000000..8811bcaf8
--- /dev/null
+++ b/packages/order-utils/src/sorting_utils.ts
@@ -0,0 +1,54 @@
+import { schemas } from '@0xproject/json-schemas';
+import { Order } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { assert } from './assert';
+import { constants } from './constants';
+import { rateUtils } from './rate_utils';
+
+export const sortingUtils = {
+    /**
+     * Takes an array of orders and sorts them by takerAsset/makerAsset rate in ascending order (best rate first).
+     * Adjusts the rate of each order according to the feeRate and takerFee for that order.
+     * @param   orders      An array of objects that extend the Order interface. All orders should specify ZRX as
+     *                      the makerAsset and WETH as the takerAsset.
+     * @param   feeRate     The market rate of ZRX denominated in takerAssetAmount
+     *                      (ex. feeRate is 0.1 takerAsset/ZRX if it takes 1 unit of takerAsset to buy 10 ZRX)
+     *                      Defaults to 0
+     * @return  The input orders sorted by rate in ascending order
+     */
+    sortOrdersByFeeAdjustedRate<T extends Order>(orders: T[], feeRate: BigNumber = constants.ZERO_AMOUNT): T[] {
+        assert.doesConformToSchema('orders', orders, schemas.ordersSchema);
+        assert.isBigNumber('feeRate', feeRate);
+        const rateCalculator = (order: Order) => rateUtils.getFeeAdjustedRateOfOrder(order, feeRate);
+        const sortedOrders = sortOrders(orders, rateCalculator);
+        return sortedOrders;
+    },
+    /**
+     * Takes an array of fee orders (makerAssetData corresponds to ZRX and takerAssetData corresponds to WETH)
+     * and sorts them by rate in ascending order (best rate first). Adjusts the rate according to the takerFee.
+     * @param   feeOrders       An array of objects that extend the Order interface. All orders should specify ZRX as
+     *                          the makerAsset and WETH as the takerAsset.
+     * @return  The input orders sorted by rate in ascending order
+     */
+    sortFeeOrdersByFeeAdjustedRate(feeOrders: Order[]): Order[] {
+        assert.doesConformToSchema('feeOrders', feeOrders, schemas.ordersSchema);
+        const rateCalculator = rateUtils.getFeeAdjustedRateOfFeeOrder.bind(rateUtils);
+        const sortedOrders = sortOrders(feeOrders, rateCalculator);
+        return sortedOrders;
+    },
+};
+
+type RateCalculator = (order: Order) => BigNumber;
+
+// takes an array of orders, copies them, and sorts the copy based on the rate definition provided by rateCalculator
+function sortOrders<T extends Order>(orders: T[], rateCalculator: RateCalculator): T[] {
+    const copiedOrders = _.cloneDeep(orders);
+    copiedOrders.sort((firstOrder, secondOrder) => {
+        const firstOrderRate = rateCalculator(firstOrder);
+        const secondOrderRate = rateCalculator(secondOrder);
+        return firstOrderRate.comparedTo(secondOrderRate);
+    });
+    return copiedOrders;
+}
diff --git a/packages/order-utils/src/types.ts b/packages/order-utils/src/types.ts
index 1fbd8cf7b..2e9c79d80 100644
--- a/packages/order-utils/src/types.ts
+++ b/packages/order-utils/src/types.ts
@@ -41,3 +41,31 @@ export interface CreateOrderOpts {
     salt?: BigNumber;
     expirationTimeSeconds?: BigNumber;
 }
+
+/**
+ * remainingFillableMakerAssetAmount: An array of BigNumbers corresponding to the `orders` parameter.
+ * You can use `OrderStateUtils` `@0xproject/order-utils` to perform blockchain lookups for these values.
+ * Defaults to `makerAssetAmount` values from the orders param.
+ * slippageBufferAmount: An additional amount of makerAsset to be covered by the result in case of trade collisions or partial fills.
+ * Defaults to 0
+ */
+export interface FindOrdersThatCoverMakerAssetFillAmountOpts {
+    remainingFillableMakerAssetAmounts?: BigNumber[];
+    slippageBufferAmount?: BigNumber;
+}
+
+/**
+ * remainingFillableMakerAssetAmount: An array of BigNumbers corresponding to the `orders` parameter.
+ * You can use `OrderStateUtils` `@0xproject/order-utils` to perform blockchain lookups for these values.
+ * Defaults to `makerAssetAmount` values from the orders param.
+ * remainingFillableFeeAmounts: An array of BigNumbers corresponding to the feeOrders parameter.
+ * You can use OrderStateUtils @0xproject/order-utils to perform blockchain lookups for these values.
+ * Defaults to `makerAssetAmount` values from the feeOrders param.
+ * slippageBufferAmount: An additional amount of fee to be covered by the result in case of trade collisions or partial fills.
+ * Defaults to 0
+ */
+export interface FindFeeOrdersThatCoverFeesForTargetOrdersOpts {
+    remainingFillableMakerAssetAmounts?: BigNumber[];
+    remainingFillableFeeAmounts?: BigNumber[];
+    slippageBufferAmount?: BigNumber;
+}