From 5db065644c03ac66aa6ea20bfc8ce0e4fa996982 Mon Sep 17 00:00:00 2001
From: Michael Zhu <mchl.zhu.96@gmail.com>
Date: Tue, 3 Mar 2020 17:11:26 -0800
Subject: [PATCH] Add tooling and unit tests

---
 contracts/extensions/src/index.ts             |  1 +
 .../extensions/src/max_gas_price_utils.ts     | 44 ++++++++++++
 .../extensions/test/max_gas_price_test.ts     | 71 +++++++++++++++++++
 3 files changed, 116 insertions(+)
 create mode 100644 contracts/extensions/src/max_gas_price_utils.ts
 create mode 100644 contracts/extensions/test/max_gas_price_test.ts

diff --git a/contracts/extensions/src/index.ts b/contracts/extensions/src/index.ts
index 8615baa7c9..1e8731cfd1 100644
--- a/contracts/extensions/src/index.ts
+++ b/contracts/extensions/src/index.ts
@@ -29,3 +29,4 @@ export {
     TupleDataItem,
     StateMutability,
 } from 'ethereum-types';
+export * from './max_gas_price_utils';
diff --git a/contracts/extensions/src/max_gas_price_utils.ts b/contracts/extensions/src/max_gas_price_utils.ts
new file mode 100644
index 0000000000..754c8d4069
--- /dev/null
+++ b/contracts/extensions/src/max_gas_price_utils.ts
@@ -0,0 +1,44 @@
+import { constants } from '@0x/contracts-test-utils';
+import { assetDataUtils } from '@0x/order-utils';
+import { StaticCallAssetData } from '@0x/types';
+import { AbiEncoder, BigNumber } from '@0x/utils';
+
+const maxGasPriceEncoder = AbiEncoder.create([{ name: 'maxGasPrice', type: 'uint256' }]);
+const customGasPriceEncoder = AbiEncoder.createMethod('checkGasPrice', [{ name: 'data', type: 'bytes' }]);
+const defaultGasPriceEncoder = AbiEncoder.createMethod('checkGasPrice', []);
+
+const ONE_GWEI = new BigNumber(10 ** 9);
+export const TWENTY_GWEI = ONE_GWEI.times(20);
+
+/**
+ * Encodes the given stop limit data parameters into StaticCall asset data so that it can be used
+ * in a 0x order.
+ */
+export function encodeMaxGasPriceStaticCallData(maxGasPriceContractAddress: string, maxGasPrice?: BigNumber): string {
+    const staticCallData =
+        maxGasPrice === undefined
+            ? defaultGasPriceEncoder.encode({})
+            : customGasPriceEncoder.encode({
+                  data: maxGasPriceEncoder.encode({ maxGasPrice }),
+              });
+    return assetDataUtils.encodeStaticCallAssetData(
+        maxGasPriceContractAddress,
+        staticCallData,
+        constants.KECCAK256_NULL,
+    );
+}
+
+/**
+ * Decodes the maxGasPrice StaticCall asset data.
+ */
+export function decodeMaxGasPriceStaticCallData(assetData: string): BigNumber {
+    // tslint:disable-next-line:no-unnecessary-type-assertion
+    const { staticCallData } = assetDataUtils.decodeAssetDataOrThrow(assetData) as StaticCallAssetData;
+    try {
+        const { maxGasPrice } = maxGasPriceEncoder.decode(customGasPriceEncoder.strictDecode<string>(staticCallData));
+        return maxGasPrice;
+    } catch (e) {
+        defaultGasPriceEncoder.strictDecode(staticCallData);
+        return TWENTY_GWEI;
+    }
+}
diff --git a/contracts/extensions/test/max_gas_price_test.ts b/contracts/extensions/test/max_gas_price_test.ts
new file mode 100644
index 0000000000..3264532d84
--- /dev/null
+++ b/contracts/extensions/test/max_gas_price_test.ts
@@ -0,0 +1,71 @@
+import { blockchainTests, constants, expect, getRandomInteger } from '@0x/contracts-test-utils';
+import { AbiEncoder } from '@0x/utils';
+
+import {
+    decodeMaxGasPriceStaticCallData,
+    encodeMaxGasPriceStaticCallData,
+    TWENTY_GWEI,
+} from '../src/max_gas_price_utils';
+
+import { artifacts } from './artifacts';
+import { MaximumGasPriceContract } from './wrappers';
+
+blockchainTests.resets('MaximumGasPrice unit tests', env => {
+    let maxGasPriceContract: MaximumGasPriceContract;
+    const maxGasPriceEncoder = AbiEncoder.create([{ name: 'maxGasPrice', type: 'uint256' }]);
+
+    before(async () => {
+        maxGasPriceContract = await MaximumGasPriceContract.deployFrom0xArtifactAsync(
+            artifacts.MaximumGasPrice,
+            env.provider,
+            env.txDefaults,
+            artifacts,
+        );
+    });
+
+    describe('Contract functionality', () => {
+        it('does not revert if tx.gasprice < default maximum', async () => {
+            await maxGasPriceContract.checkGasPrice1().callAsync({ gasPrice: TWENTY_GWEI.minus(1) });
+        });
+        it('does not revert if tx.gasprice = default maximum', async () => {
+            await maxGasPriceContract.checkGasPrice1().callAsync({ gasPrice: TWENTY_GWEI });
+        });
+        it('reverts if tx.gasPrice > default maximum', async () => {
+            const tx = maxGasPriceContract.checkGasPrice1().callAsync({ gasPrice: TWENTY_GWEI.plus(1) });
+            return expect(tx).to.revertWith('MaximumGasPrice/GAS_PRICE_EXCEEDS_20_GWEI');
+        });
+        it('does not revert if tx.gasprice < custom maximum', async () => {
+            const maxGasPrice = getRandomInteger(0, TWENTY_GWEI.times(2));
+            await maxGasPriceContract
+                .checkGasPrice2(maxGasPriceEncoder.encode({ maxGasPrice }))
+                .callAsync({ gasPrice: maxGasPrice.minus(1) });
+        });
+        it('does not revert if tx.gasprice = default maximum', async () => {
+            const maxGasPrice = getRandomInteger(0, TWENTY_GWEI.times(2));
+            await maxGasPriceContract
+                .checkGasPrice2(maxGasPriceEncoder.encode({ maxGasPrice }))
+                .callAsync({ gasPrice: maxGasPrice });
+        });
+        it('reverts if tx.gasPrice > default maximum', async () => {
+            const maxGasPrice = getRandomInteger(0, TWENTY_GWEI.times(2));
+            const tx = maxGasPriceContract
+                .checkGasPrice2(maxGasPriceEncoder.encode({ maxGasPrice }))
+                .callAsync({ gasPrice: maxGasPrice.plus(1) });
+            return expect(tx).to.revertWith('MaximumGasPrice/GAS_PRICE_EXCEEDS_MAXIMUM');
+        });
+    });
+
+    describe('Data encoding/decoding tools', () => {
+        it('correctly decodes default maximum gas price', async () => {
+            const encoded = encodeMaxGasPriceStaticCallData(maxGasPriceContract.address);
+            const decoded = decodeMaxGasPriceStaticCallData(encoded);
+            expect(decoded).to.bignumber.equal(TWENTY_GWEI);
+        });
+        it('correctly decodes custom maximum gas price', async () => {
+            const maxGasPrice = getRandomInteger(0, constants.MAX_UINT256);
+            const encoded = encodeMaxGasPriceStaticCallData(maxGasPriceContract.address, maxGasPrice);
+            const decoded = decodeMaxGasPriceStaticCallData(encoded);
+            expect(decoded).to.bignumber.equal(maxGasPrice);
+        });
+    });
+});