path: root/packages/order-utils/src/rate_utils.ts

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;
    },
};