fix: address PR comments

6 files changed, 90 insertions, 33 deletions

diff --git a/packages/instant/public/index.html b/packages/instant/public/index.html
index dc172e6e4..62532dad9 100644
--- a/packages/instant/public/index.html
+++ b/packages/instant/public/index.html
@@ -35,37 +35,39 @@
             DECIMAL_PLACES: 78,
         });
         const providedOrders = [
+            // Order selling REP
             {
-                "senderAddress": "0x0000000000000000000000000000000000000000",
-                "makerAddress": "0x34a745008a643eebc58920eaa29fb1165b4a288e",
-                "takerAddress": "0x0000000000000000000000000000000000000000",
-                "makerFee": new BigNumber("0"),
-                "takerFee": new BigNumber("0"),
-                "makerAssetAmount": new BigNumber("400000000000000000000"),
-                "takerAssetAmount": new BigNumber("40000000000000000000"),
-                "makerAssetData": "0xf47261b00000000000000000000000008cb3971b8eb709c14616bd556ff6683019e90d9c",
-                "takerAssetData": "0xf47261b0000000000000000000000000d0a1e359811322d97991e03f863a0c30c2cf029c",
-                "expirationTimeSeconds": new BigNumber("1543046400"),
-                "feeRecipientAddress": "0x0000000000000000000000000000000000000000",
-                "salt": new BigNumber("47929252863126413473766089649682650973189811771354566206928245255479607883031"),
-                "signature": "0x1c0bf8ba709ceb5b32e6b0b5a8bb7f07e9d19aba88d8530715f8a298d12188e3862fcc0a30ddfad4062b30459f2859323c064052f12cc687466c457934b9419a1b03",
-                "exchangeAddress": "0x35dd2932454449b14cee11a94d3674a936d5d7b2"
+                senderAddress: '0x0000000000000000000000000000000000000000',
+                makerAddress: '0x34a745008a643eebc58920eaa29fb1165b4a288e',
+                takerAddress: '0x0000000000000000000000000000000000000000',
+                makerFee: new BigNumber('0'),
+                takerFee: new BigNumber('0'),
+                makerAssetAmount: new BigNumber('400000000000000000000'),
+                takerAssetAmount: new BigNumber('40000000000000000000'),
+                makerAssetData: '0xf47261b00000000000000000000000008cb3971b8eb709c14616bd556ff6683019e90d9c',
+                takerAssetData: '0xf47261b0000000000000000000000000d0a1e359811322d97991e03f863a0c30c2cf029c',
+                expirationTimeSeconds: new BigNumber('1543046400'),
+                feeRecipientAddress: '0x0000000000000000000000000000000000000000',
+                salt: new BigNumber('47929252863126413473766089649682650973189811771354566206928245255479607883031'),
+                signature: '0x1c0bf8ba709ceb5b32e6b0b5a8bb7f07e9d19aba88d8530715f8a298d12188e3862fcc0a30ddfad4062b30459f2859323c064052f12cc687466c457934b9419a1b03',
+                exchangeAddress: '0x35dd2932454449b14cee11a94d3674a936d5d7b2'
             },
+            // Order selling ZRX
             {
-                "senderAddress": "0x0000000000000000000000000000000000000000",
-                "makerAddress": "0x34a745008a643eebc58920eaa29fb1165b4a288e",
-                "takerAddress": "0x0000000000000000000000000000000000000000",
-                "makerFee": new BigNumber("0"),
-                "takerFee": new BigNumber("0"),
-                "makerAssetAmount": new BigNumber("300000000000000000000"),
-                "takerAssetAmount": new BigNumber("31000000000000000000"),
-                "makerAssetData": "0xf47261b00000000000000000000000002002d3812f58e35f0ea1ffbf80a75a38c32175fa",
-                "takerAssetData": "0xf47261b0000000000000000000000000d0a1e359811322d97991e03f863a0c30c2cf029c",
-                "expirationTimeSeconds": new BigNumber("2524636800"),
-                "feeRecipientAddress": "0x0000000000000000000000000000000000000000",
-                "salt": new BigNumber("64592004666704945574675477805199411288137454783320798602050822322450089238268"),
-                "signature": "0x1c13cacddca8d7d8248e91f412377e68f8f1f9891a59a6c1b2eea9f7b33558c30c4fb86a448e08ab7def40a28fb3a3062dcb33bb3c45302447fce5c4288b7c7f5b03",
-                "exchangeAddress": "0x35dd2932454449b14cee11a94d3674a936d5d7b2"
+                senderAddress: '0x0000000000000000000000000000000000000000',
+                makerAddress: '0x34a745008a643eebc58920eaa29fb1165b4a288e',
+                takerAddress: '0x0000000000000000000000000000000000000000',
+                makerFee: new BigNumber('0'),
+                takerFee: new BigNumber('0'),
+                makerAssetAmount: new BigNumber('300000000000000000000'),
+                takerAssetAmount: new BigNumber('31000000000000000000'),
+                makerAssetData: '0xf47261b00000000000000000000000002002d3812f58e35f0ea1ffbf80a75a38c32175fa',
+                takerAssetData: '0xf47261b0000000000000000000000000d0a1e359811322d97991e03f863a0c30c2cf029c',
+                expirationTimeSeconds: new BigNumber('2524636800'),
+                feeRecipientAddress: '0x0000000000000000000000000000000000000000',
+                salt: new BigNumber('64592004666704945574675477805199411288137454783320798602050822322450089238268'),
+                signature: '0x1c13cacddca8d7d8248e91f412377e68f8f1f9891a59a6c1b2eea9f7b33558c30c4fb86a448e08ab7def40a28fb3a3062dcb33bb3c45302447fce5c4288b7c7f5b03',
+                exchangeAddress: '0x35dd2932454449b14cee11a94d3674a936d5d7b2'
             }
         ];
         const queryParams = new Uri(window.location.search);
diff --git a/packages/instant/src/components/buy_button.tsx b/packages/instant/src/components/buy_button.tsx
index e65e62e47..58575b1b3 100644
--- a/packages/instant/src/components/buy_button.tsx
+++ b/packages/instant/src/components/buy_button.tsx
@@ -7,6 +7,7 @@ import { ColorOption } from '../style/theme';
 import { ZeroExInstantError } from '../types';
 import { getBestAddress } from '../util/address';
 import { balanceUtil } from '../util/balance';
+import { gasPriceEstimator } from '../util/gas_price_estimator';
 import { util } from '../util/util';
 import { web3Wrapper } from '../util/web3_wrapper';
 
@@ -56,9 +57,9 @@ export class BuyButton extends React.Component<BuyButtonProps> {
         }
 
         let txHash: string | undefined;
+        const gasPrice = await gasPriceEstimator.getFastAmountInWeiAsync();
         try {
-            const gasPrice = DEFAULT_GAS_PRICE;
-            txHash = await assetBuyer.executeBuyQuoteAsync(buyQuote, { gasPrice, takerAddress });
+            txHash = await assetBuyer.executeBuyQuoteAsync(buyQuote, { takerAddress, gasPrice });
         } catch (e) {
             if (e instanceof Error) {
                 if (e.message === AssetBuyerError.SignatureRequestDenied) {
diff --git a/packages/instant/src/components/zero_ex_instant.tsx b/packages/instant/src/components/zero_ex_instant.tsx
index 19a2d6b9b..d54dfc153 100644
--- a/packages/instant/src/components/zero_ex_instant.tsx
+++ b/packages/instant/src/components/zero_ex_instant.tsx
@@ -13,6 +13,7 @@ import { AssetMetaData, Network } from '../types';
 import { assetUtils } from '../util/asset';
 import { BigNumberInput } from '../util/big_number_input';
 import { errorFlasher } from '../util/error_flasher';
+import { gasPriceEstimator } from '../util/gas_price_estimator';
 import { getProvider } from '../util/provider';
 import { web3Wrapper } from '../util/web3_wrapper';
 
@@ -78,6 +79,12 @@ export class ZeroExInstant extends React.Component<ZeroExInstantProps> {
     public componentDidMount(): void {
         // tslint:disable-next-line:no-floating-promises
         asyncData.fetchAndDispatchToStore(this._store);
+
+        // warm up the gas price estimator cache just in case we can't
+        // grab the gas price estimate when submitting the transaction
+        // tslint:disable-next-line:no-floating-promises
+        gasPriceEstimator.getFastAmountInWeiAsync();
+
         // tslint:disable-next-line:no-floating-promises
         this._flashErrorIfWrongNetwork();
     }
diff --git a/packages/instant/src/constants.ts b/packages/instant/src/constants.ts
index 47cb2eaeb..424f35ecb 100644
--- a/packages/instant/src/constants.ts
+++ b/packages/instant/src/constants.ts
@@ -5,3 +5,5 @@ export const DEFAULT_ZERO_EX_CONTAINER_SELECTOR = '#zeroExInstantContainer';
 export const WEB_3_WRAPPER_TRANSACTION_FAILED_ERROR_MSG_PREFIX = 'Transaction failed';
 export const GWEI_IN_WEI = new BigNumber(1000000000);
 export const DEFAULT_GAS_PRICE = GWEI_IN_WEI.mul(6);
+export const ETH_GAS_STATION_API_BASE_URL = 'https://ethgasstation.info';
+export const COINBASE_API_BASE_URL = 'https://api.coinbase.com/v2';
diff --git a/packages/instant/src/util/coinbase_api.ts b/packages/instant/src/util/coinbase_api.ts
index 080421f98..faac8d82d 100644
--- a/packages/instant/src/util/coinbase_api.ts
+++ b/packages/instant/src/util/coinbase_api.ts
@@ -1,9 +1,10 @@
-import { BigNumber } from '@0x/utils';
+import { BigNumber, fetchAsync } from '@0x/utils';
+
+import { COINBASE_API_BASE_URL } from '../constants';
 
-const baseEndpoint = 'https://api.coinbase.com/v2';
 export const coinbaseApi = {
     getEthUsdPrice: async (): Promise<BigNumber> => {
-        const res = await fetch(`${baseEndpoint}/prices/ETH-USD/buy`);
+        const res = await fetchAsync(`${COINBASE_API_BASE_URL}/prices/ETH-USD/buy`);
         const resJson = await res.json();
         return new BigNumber(resJson.data.amount);
     },
diff --git a/packages/instant/src/util/gas_price_estimator.ts b/packages/instant/src/util/gas_price_estimator.ts
new file mode 100644
index 000000000..336c4a3fa
--- /dev/null
+++ b/packages/instant/src/util/gas_price_estimator.ts
@@ -0,0 +1,44 @@
+import { BigNumber, fetchAsync } from '@0x/utils';
+
+import { DEFAULT_GAS_PRICE, ETH_GAS_STATION_API_BASE_URL, GWEI_IN_WEI } from '../constants';
+
+interface EthGasStationResult {
+    average: number;
+    fastestWait: number;
+    fastWait: number;
+    fast: number;
+    safeLowWait: number;
+    blockNum: number;
+    avgWait: number;
+    block_time: number;
+    speed: number;
+    fastest: number;
+    safeLow: number;
+}
+
+const fetchFastAmountInWeiAsync = async () => {
+    const res = await fetchAsync(`${ETH_GAS_STATION_API_BASE_URL}/json/ethgasAPI.json`);
+    const gasInfo = (await res.json()) as EthGasStationResult;
+    // Eth Gas Station result is gwei * 10
+    const gasPriceInGwei = new BigNumber(gasInfo.fast / 10);
+    return gasPriceInGwei.mul(GWEI_IN_WEI);
+};
+
+export class GasPriceEstimator {
+    private _lastFetched?: BigNumber;
+    public async getFastAmountInWeiAsync(): Promise<BigNumber> {
+        let fetchedAmount: BigNumber | undefined;
+        try {
+            fetchedAmount = await fetchFastAmountInWeiAsync();
+        } catch {
+            fetchedAmount = undefined;
+        }
+
+        if (fetchedAmount) {
+            this._lastFetched = fetchedAmount;
+        }
+
+        return fetchedAmount || this._lastFetched || DEFAULT_GAS_PRICE;
+    }
+}
+export const gasPriceEstimator = new GasPriceEstimator();