1 files changed, 66 insertions, 0 deletions
diff --git a/src/utils/order_validation_utils.ts b/src/utils/order_validation_utils.ts
new file mode 100644
index 000000000..05c284ac3
--- /dev/null
+++ b/src/utils/order_validation_utils.ts
@@ -0,0 +1,66 @@
+import {ExchangeContractErrs, SignedOrder} from '../types';
+
+export const orderValidationUtils = {
+    /**
+     * This method does not currently validate the edge-case where the makerToken or takerToken is also the token used
+     * to pay fees  (ZRX). It is possible for them to have enough for fees and the transfer but not both.
+     * Handling the edge-cases that arise when this happens would require making sure that the user has sufficient
+     * funds to pay both the fees and the transfer amount. We decided to punt on this for now as the contracts
+     * will throw for these edge-cases.
+     * TODO: Throw errors before calling the smart contract for these edge-cases in order to minimize
+     * the callers gas costs.
+     */
+    async validateFillOrderBalancesAndAllowancesAndThrowIfInvalidAsync(
+        signedOrder: SignedOrder, fillTakerAmount: BigNumber.BigNumber, senderAddress: string, zrxTokenAddress: string,
+    ): Promise<void> {
+
+        const makerBalance = await this._tokenWrapper.getBalanceAsync(signedOrder.makerTokenAddress,
+                                                                     signedOrder.maker);
+        const takerBalance = await this._tokenWrapper.getBalanceAsync(signedOrder.takerTokenAddress, senderAddress);
+        const makerAllowance = await this._tokenWrapper.getProxyAllowanceAsync(signedOrder.makerTokenAddress,
+                                                                              signedOrder.maker);
+        const takerAllowance = await this._tokenWrapper.getProxyAllowanceAsync(signedOrder.takerTokenAddress,
+                                                                              senderAddress);
+
+        // exchangeRate is the price of one maker token denominated in taker tokens
+        const exchangeRate = signedOrder.takerTokenAmount.div(signedOrder.makerTokenAmount);
+        const fillMakerAmountInBaseUnits = fillTakerAmount.div(exchangeRate);
+
+        const isMakerTokenZRX = signedOrder.makerTokenAddress === zrxTokenAddress;
+        const isTakerTokenZRX = signedOrder.takerTokenAddress === zrxTokenAddress;
+
+        if (fillTakerAmount.greaterThan(takerBalance)) {
+            throw new Error(ExchangeContractErrs.InsufficientTakerBalance);
+        }
+        if (fillTakerAmount.greaterThan(takerAllowance)) {
+            throw new Error(ExchangeContractErrs.InsufficientTakerAllowance);
+        }
+        if (fillMakerAmountInBaseUnits.greaterThan(makerBalance)) {
+            throw new Error(ExchangeContractErrs.InsufficientMakerBalance);
+        }
+        if (fillMakerAmountInBaseUnits.greaterThan(makerAllowance)) {
+            throw new Error(ExchangeContractErrs.InsufficientMakerAllowance);
+        }
+
+        const makerFeeBalance = await this._tokenWrapper.getBalanceAsync(zrxTokenAddress,
+                                                                        signedOrder.maker);
+        const takerFeeBalance = await this._tokenWrapper.getBalanceAsync(zrxTokenAddress, senderAddress);
+        const makerFeeAllowance = await this._tokenWrapper.getProxyAllowanceAsync(zrxTokenAddress,
+                                                                                 signedOrder.maker);
+        const takerFeeAllowance = await this._tokenWrapper.getProxyAllowanceAsync(zrxTokenAddress,
+                                                                                 senderAddress);
+
+        if (signedOrder.takerFee.greaterThan(takerFeeBalance)) {
+            throw new Error(ExchangeContractErrs.InsufficientTakerFeeBalance);
+        }
+        if (signedOrder.takerFee.greaterThan(takerFeeAllowance)) {
+            throw new Error(ExchangeContractErrs.InsufficientTakerFeeAllowance);
+        }
+        if (signedOrder.makerFee.greaterThan(makerFeeBalance)) {
+            throw new Error(ExchangeContractErrs.InsufficientMakerFeeBalance);
+        }
+        if (signedOrder.makerFee.greaterThan(makerFeeAllowance)) {
+            throw new Error(ExchangeContractErrs.InsufficientMakerFeeAllowance);
+        }
+    },
+};