5 files changed, 398 insertions, 0 deletions
diff --git a/packages/asset-buyer/src/utils/assert.ts b/packages/asset-buyer/src/utils/assert.ts
new file mode 100644
index 000000000..04f425237
--- /dev/null
+++ b/packages/asset-buyer/src/utils/assert.ts
@@ -0,0 +1,51 @@
+import { assert as sharedAssert } from '@0xproject/assert';
+import { schemas } from '@0xproject/json-schemas';
+import { SignedOrder } from '@0xproject/types';
+import * as _ from 'lodash';
+
+import { BuyQuote, OrderProvider, OrderProviderRequest } from '../types';
+
+export const assert = {
+    ...sharedAssert,
+    isValidBuyQuote(variableName: string, buyQuote: BuyQuote): void {
+        sharedAssert.isHexString(`${variableName}.assetData`, buyQuote.assetData);
+        sharedAssert.doesConformToSchema(`${variableName}.orders`, buyQuote.orders, schemas.signedOrdersSchema);
+        sharedAssert.doesConformToSchema(`${variableName}.feeOrders`, buyQuote.feeOrders, schemas.signedOrdersSchema);
+        sharedAssert.isBigNumber(`${variableName}.minRate`, buyQuote.minRate);
+        sharedAssert.isBigNumber(`${variableName}.maxRate`, buyQuote.maxRate);
+        sharedAssert.isBigNumber(`${variableName}.assetBuyAmount`, buyQuote.assetBuyAmount);
+        if (!_.isUndefined(buyQuote.feePercentage)) {
+            sharedAssert.isNumber(`${variableName}.feePercentage`, buyQuote.feePercentage);
+        }
+    },
+    isValidOrderProvider(variableName: string, orderFetcher: OrderProvider): void {
+        sharedAssert.isFunction(`${variableName}.getOrdersAsync`, orderFetcher.getOrdersAsync);
+    },
+    isValidOrderProviderRequest(variableName: string, orderFetcherRequest: OrderProviderRequest): void {
+        sharedAssert.isHexString(`${variableName}.makerAssetData`, orderFetcherRequest.makerAssetData);
+        sharedAssert.isHexString(`${variableName}.takerAssetData`, orderFetcherRequest.takerAssetData);
+        sharedAssert.isNumber(`${variableName}.networkId`, orderFetcherRequest.networkId);
+    },
+    areValidProvidedOrders(variableName: string, orders: SignedOrder[]): void {
+        if (orders.length === 0) {
+            return;
+        }
+        const makerAssetData = orders[0].makerAssetData;
+        const takerAssetData = orders[0].takerAssetData;
+        const filteredOrders = _.filter(
+            orders,
+            order => order.makerAssetData === makerAssetData && order.takerAssetData === takerAssetData,
+        );
+        sharedAssert.assert(
+            orders.length === filteredOrders.length,
+            `Expected all orders in ${variableName} to have the same makerAssetData and takerAssetData.`,
+        );
+    },
+    isValidPercentage(variableName: string, percentage: number): void {
+        assert.isNumber(variableName, percentage);
+        assert.assert(
+            percentage >= 0 && percentage <= 1,
+            `Expected ${variableName} to be between 0 and 1, but is ${percentage}`,
+        );
+    },
+};
diff --git a/packages/asset-buyer/src/utils/asset_data_utils.ts b/packages/asset-buyer/src/utils/asset_data_utils.ts
new file mode 100644
index 000000000..d05ff2504
--- /dev/null
+++ b/packages/asset-buyer/src/utils/asset_data_utils.ts
@@ -0,0 +1,26 @@
+import { ContractWrappers } from '@0xproject/contract-wrappers';
+import { assetDataUtils as sharedAssetDataUtils } from '@0xproject/order-utils';
+import * as _ from 'lodash';
+
+import { AssetBuyerError } from '../types';
+
+export const assetDataUtils = {
+    ...sharedAssetDataUtils,
+    getEtherTokenAssetDataOrThrow(contractWrappers: ContractWrappers): string {
+        const etherTokenAddressIfExists = contractWrappers.etherToken.getContractAddressIfExists();
+        if (_.isUndefined(etherTokenAddressIfExists)) {
+            throw new Error(AssetBuyerError.NoEtherTokenContractFound);
+        }
+        const etherTokenAssetData = sharedAssetDataUtils.encodeERC20AssetData(etherTokenAddressIfExists);
+        return etherTokenAssetData;
+    },
+    getZrxTokenAssetDataOrThrow(contractWrappers: ContractWrappers): string {
+        let zrxTokenAssetData: string;
+        try {
+            zrxTokenAssetData = contractWrappers.exchange.getZRXAssetData();
+        } catch (err) {
+            throw new Error(AssetBuyerError.NoZrxTokenContractFound);
+        }
+        return zrxTokenAssetData;
+    },
+};
diff --git a/packages/asset-buyer/src/utils/buy_quote_calculator.ts b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
new file mode 100644
index 000000000..9946924ef
--- /dev/null
+++ b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
@@ -0,0 +1,89 @@
+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';
+
+import { orderUtils } from './order_utils';
+
+// Calculates a buy quote for orders that have WETH as the takerAsset
+export const buyQuoteCalculator = {
+    calculate(
+        ordersAndFillableAmounts: AssetBuyerOrdersAndFillableAmounts,
+        assetBuyAmount: BigNumber,
+        feePercentage: number,
+        slippagePercentage: number,
+    ): BuyQuote {
+        const {
+            orders,
+            feeOrders,
+            remainingFillableMakerAssetAmounts,
+            remainingFillableFeeAmounts,
+        } = ordersAndFillableAmounts;
+        const slippageBufferAmount = assetBuyAmount.mul(slippagePercentage).round();
+        const {
+            resultOrders,
+            remainingFillAmount,
+            ordersRemainingFillableMakerAssetAmounts,
+        } = marketUtils.findOrdersThatCoverMakerAssetFillAmount(orders, assetBuyAmount, {
+            remainingFillableMakerAssetAmounts,
+            slippageBufferAmount,
+        });
+        if (remainingFillAmount.gt(constants.ZERO_AMOUNT)) {
+            throw new Error(AssetBuyerError.InsufficientAssetLiquidity);
+        }
+        // TODO(bmillman): 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,
+            feeOrdersRemainingFillableMakerAssetAmounts,
+        } = marketUtils.findFeeOrdersThatCoverFeesForTargetOrders(resultOrders, feeOrders, {
+            remainingFillableMakerAssetAmounts,
+            remainingFillableFeeAmounts,
+        });
+        if (remainingFeeAmount.gt(constants.ZERO_AMOUNT)) {
+            throw new Error(AssetBuyerError.InsufficientZrxLiquidity);
+        }
+        const assetData = orders[0].makerAssetData;
+
+        // 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 claimableTakerAssetAmount = orderUtils.calculateRemainingTakerAssetAmount(
+                order,
+                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: feeAdjustedMinRate,
+            maxRate: feeAdjustedMaxRate,
+            assetBuyAmount,
+            feePercentage,
+        };
+    },
+};
diff --git a/packages/asset-buyer/src/utils/order_provider_response_processor.ts b/packages/asset-buyer/src/utils/order_provider_response_processor.ts
new file mode 100644
index 000000000..31fdcc182
--- /dev/null
+++ b/packages/asset-buyer/src/utils/order_provider_response_processor.ts
@@ -0,0 +1,202 @@
+import { OrderAndTraderInfo, OrderStatus, OrderValidatorWrapper } from '@0xproject/contract-wrappers';
+import { sortingUtils } from '@0xproject/order-utils';
+import { RemainingFillableCalculator } from '@0xproject/order-utils/lib/src/remaining_fillable_calculator';
+import { SignedOrder } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { constants } from '../constants';
+import {
+    AssetBuyerError,
+    AssetBuyerOrdersAndFillableAmounts,
+    OrderProviderRequest,
+    OrderProviderResponse,
+    SignedOrderWithRemainingFillableMakerAssetAmount,
+} from '../types';
+
+import { orderUtils } from './order_utils';
+
+interface OrdersAndRemainingFillableMakerAssetAmounts {
+    orders: SignedOrder[];
+    remainingFillableMakerAssetAmounts: BigNumber[];
+}
+
+export const orderProviderResponseProcessor = {
+    throwIfInvalidResponse(response: OrderProviderResponse, request: OrderProviderRequest): void {
+        const { makerAssetData, takerAssetData } = request;
+        _.forEach(response.orders, order => {
+            if (order.makerAssetData !== makerAssetData || order.takerAssetData !== takerAssetData) {
+                throw new Error(AssetBuyerError.InvalidOrderProviderResponse);
+            }
+        });
+    },
+    /**
+     * Take the responses for the target orders to buy and fee orders and process them.
+     * Processing includes:
+     * - Drop orders that are expired or not open orders (null taker address)
+     * - If shouldValidateOnChain, attempt to grab fillable amounts from on-chain otherwise assume completely fillable
+     * - Sort by rate
+     */
+    async processAsync(
+        targetOrderProviderResponse: OrderProviderResponse,
+        feeOrderProviderResponse: OrderProviderResponse,
+        zrxTokenAssetData: string,
+        expiryBufferSeconds: number,
+        orderValidator?: OrderValidatorWrapper,
+    ): Promise<AssetBuyerOrdersAndFillableAmounts> {
+        // drop orders that are expired or not open
+        const filteredTargetOrders = filterOutExpiredAndNonOpenOrders(
+            targetOrderProviderResponse.orders,
+            expiryBufferSeconds,
+        );
+        const filteredFeeOrders = filterOutExpiredAndNonOpenOrders(
+            feeOrderProviderResponse.orders,
+            expiryBufferSeconds,
+        );
+        // set the orders to be sorted equal to the filtered orders
+        let unsortedTargetOrders = filteredTargetOrders;
+        let unsortedFeeOrders = filteredFeeOrders;
+        // if an orderValidator is provided, use on chain information to calculate remaining fillable makerAsset amounts
+        if (!_.isUndefined(orderValidator)) {
+            // TODO(bmillman): improvement
+            // try/catch these requests and throw a more domain specific error
+            // TODO(bmillman): optimization
+            // reduce this to once RPC call buy combining orders into one array and then splitting up the response
+            const [targetOrdersAndTradersInfo, feeOrdersAndTradersInfo] = await Promise.all(
+                _.map([filteredTargetOrders, filteredFeeOrders], ordersToBeValidated => {
+                    const takerAddresses = _.map(ordersToBeValidated, () => constants.NULL_ADDRESS);
+                    return orderValidator.getOrdersAndTradersInfoAsync(ordersToBeValidated, takerAddresses);
+                }),
+            );
+            // take orders + on chain information and find the valid orders and remaining fillable maker asset amounts
+            unsortedTargetOrders = getValidOrdersWithRemainingFillableMakerAssetAmountsFromOnChain(
+                filteredTargetOrders,
+                targetOrdersAndTradersInfo,
+                zrxTokenAssetData,
+            );
+            // take orders + on chain information and find the valid orders and remaining fillable maker asset amounts
+            unsortedFeeOrders = getValidOrdersWithRemainingFillableMakerAssetAmountsFromOnChain(
+                filteredFeeOrders,
+                feeOrdersAndTradersInfo,
+                zrxTokenAssetData,
+            );
+        }
+        // sort orders by rate
+        // TODO(bmillman): optimization
+        // provide a feeRate to the sorting function to more accurately sort based on the current market for ZRX tokens
+        const sortedTargetOrders = sortingUtils.sortOrdersByFeeAdjustedRate(unsortedTargetOrders);
+        const sortedFeeOrders = sortingUtils.sortFeeOrdersByFeeAdjustedRate(unsortedFeeOrders);
+        // unbundle orders and fillable amounts and compile final result
+        const targetOrdersAndRemainingFillableMakerAssetAmounts = unbundleOrdersWithAmounts(sortedTargetOrders);
+        const feeOrdersAndRemainingFillableMakerAssetAmounts = unbundleOrdersWithAmounts(sortedFeeOrders);
+        return {
+            orders: targetOrdersAndRemainingFillableMakerAssetAmounts.orders,
+            feeOrders: feeOrdersAndRemainingFillableMakerAssetAmounts.orders,
+            remainingFillableMakerAssetAmounts:
+                targetOrdersAndRemainingFillableMakerAssetAmounts.remainingFillableMakerAssetAmounts,
+            remainingFillableFeeAmounts:
+                feeOrdersAndRemainingFillableMakerAssetAmounts.remainingFillableMakerAssetAmounts,
+        };
+    },
+};
+
+/**
+ * Given an array of orders, return a new array with expired and non open orders filtered out.
+ */
+function filterOutExpiredAndNonOpenOrders(
+    orders: SignedOrderWithRemainingFillableMakerAssetAmount[],
+    expiryBufferSeconds: number,
+): SignedOrderWithRemainingFillableMakerAssetAmount[] {
+    const result = _.filter(orders, order => {
+        return orderUtils.isOpenOrder(order) && !orderUtils.willOrderExpire(order, expiryBufferSeconds);
+    });
+    return result;
+}
+
+/**
+ * Given an array of orders and corresponding on-chain infos, return a subset of the orders
+ * that are still fillable orders with their corresponding remainingFillableMakerAssetAmounts.
+ */
+function getValidOrdersWithRemainingFillableMakerAssetAmountsFromOnChain(
+    inputOrders: SignedOrder[],
+    ordersAndTradersInfo: OrderAndTraderInfo[],
+    zrxAssetData: string,
+): SignedOrderWithRemainingFillableMakerAssetAmount[] {
+    // iterate through the input orders and find the ones that are still fillable
+    // for the orders that are still fillable, calculate the remaining fillable maker asset amount
+    const result = _.reduce(
+        inputOrders,
+        (accOrders, order, index) => {
+            // get corresponding on-chain state for the order
+            const { orderInfo, traderInfo } = ordersAndTradersInfo[index];
+            // if the order IS NOT fillable, do not add anything to the accumulations and continue iterating
+            if (orderInfo.orderStatus !== OrderStatus.FILLABLE) {
+                return accOrders;
+            }
+            // if the order IS fillable, add the order and calculate the remaining fillable amount
+            const transferrableAssetAmount = BigNumber.min([traderInfo.makerAllowance, traderInfo.makerBalance]);
+            const transferrableFeeAssetAmount = BigNumber.min([
+                traderInfo.makerZrxAllowance,
+                traderInfo.makerZrxBalance,
+            ]);
+            const remainingTakerAssetAmount = order.takerAssetAmount.minus(orderInfo.orderTakerAssetFilledAmount);
+            const remainingMakerAssetAmount = orderUtils.calculateRemainingMakerAssetAmount(
+                order,
+                remainingTakerAssetAmount,
+            );
+            const remainingFillableCalculator = new RemainingFillableCalculator(
+                order.makerFee,
+                order.makerAssetAmount,
+                order.makerAssetData === zrxAssetData,
+                transferrableAssetAmount,
+                transferrableFeeAssetAmount,
+                remainingMakerAssetAmount,
+            );
+            const remainingFillableAmount = remainingFillableCalculator.computeRemainingFillable();
+            // if the order does not have any remaining fillable makerAsset, do not add anything to the accumulations and continue iterating
+            if (remainingFillableAmount.lte(constants.ZERO_AMOUNT)) {
+                return accOrders;
+            }
+            const orderWithRemainingFillableMakerAssetAmount = {
+                ...order,
+                remainingFillableMakerAssetAmount: remainingFillableAmount,
+            };
+            const newAccOrders = _.concat(accOrders, orderWithRemainingFillableMakerAssetAmount);
+            return newAccOrders;
+        },
+        [] as SignedOrderWithRemainingFillableMakerAssetAmount[],
+    );
+    return result;
+}
+
+/**
+ * Given an array of orders with remaining fillable maker asset amounts. Unbundle into an instance of OrdersAndRemainingFillableMakerAssetAmounts.
+ * If an order is missing a corresponding remainingFillableMakerAssetAmount, assume it is completely fillable.
+ */
+function unbundleOrdersWithAmounts(
+    ordersWithAmounts: SignedOrderWithRemainingFillableMakerAssetAmount[],
+): OrdersAndRemainingFillableMakerAssetAmounts {
+    const result = _.reduce(
+        ordersWithAmounts,
+        (acc, orderWithAmount) => {
+            const { orders, remainingFillableMakerAssetAmounts } = acc;
+            const { remainingFillableMakerAssetAmount, ...order } = orderWithAmount;
+            // if we are still missing a remainingFillableMakerAssetAmount, assume the order is completely fillable
+            const newRemainingAmount = remainingFillableMakerAssetAmount || order.makerAssetAmount;
+            // if remaining amount is less than or equal to zero, do not add it
+            if (newRemainingAmount.lte(constants.ZERO_AMOUNT)) {
+                return acc;
+            }
+            const newAcc = {
+                orders: _.concat(orders, order),
+                remainingFillableMakerAssetAmounts: _.concat(remainingFillableMakerAssetAmounts, newRemainingAmount),
+            };
+            return newAcc;
+        },
+        {
+            orders: [] as SignedOrder[],
+            remainingFillableMakerAssetAmounts: [] as BigNumber[],
+        },
+    );
+    return result;
+}
diff --git a/packages/asset-buyer/src/utils/order_utils.ts b/packages/asset-buyer/src/utils/order_utils.ts
new file mode 100644
index 000000000..62166eb76
--- /dev/null
+++ b/packages/asset-buyer/src/utils/order_utils.ts
@@ -0,0 +1,30 @@
+import { SignedOrder } from '@0xproject/types';
+import { BigNumber } from '@0xproject/utils';
+
+import { constants } from '../constants';
+
+export const orderUtils = {
+    isOrderExpired(order: SignedOrder): boolean {
+        return orderUtils.willOrderExpire(order, 0);
+    },
+    willOrderExpire(order: SignedOrder, secondsFromNow: number): boolean {
+        const millisecondsInSecond = 1000;
+        const currentUnixTimestampSec = new BigNumber(Date.now() / millisecondsInSecond).round();
+        return order.expirationTimeSeconds.lessThan(currentUnixTimestampSec.minus(secondsFromNow));
+    },
+    calculateRemainingMakerAssetAmount(order: SignedOrder, remainingTakerAssetAmount: BigNumber): BigNumber {
+        if (remainingTakerAssetAmount.eq(0)) {
+            return constants.ZERO_AMOUNT;
+        }
+        return remainingTakerAssetAmount.times(order.makerAssetAmount).dividedToIntegerBy(order.takerAssetAmount);
+    },
+    calculateRemainingTakerAssetAmount(order: SignedOrder, remainingMakerAssetAmount: BigNumber): BigNumber {
+        if (remainingMakerAssetAmount.eq(0)) {
+            return constants.ZERO_AMOUNT;
+        }
+        return remainingMakerAssetAmount.times(order.takerAssetAmount).dividedToIntegerBy(order.makerAssetAmount);
+    },
+    isOpenOrder(order: SignedOrder): boolean {
+        return order.takerAddress === constants.NULL_ADDRESS;
+    },
+};