Added BalanceChecker contract (#60)

* Added BalanceChecker contract

* Upgraded to solidity 0.6, simplified contract, added tests

* uint -> uint256

* export BalanceChecker contract wrapper

* prettier

* removed superfluous test code

* prettier

packages/asset-swapper/contracts/src/BalanceChecker.sol

@@ -0,0 +1,89 @@
+/*
+
+  Copyright 2020 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.6;
+
+// ERC20 contract interface
+abstract contract IToken {
+    /// @dev Query the balance of owner
+    /// @param _owner The address from which the balance will be retrieved
+    /// @return Balance of owner
+    function balanceOf(address _owner) public virtual view returns (uint256);
+
+    /// @param _owner The address of the account owning tokens
+    /// @param _spender The address of the account able to transfer the tokens
+    /// @return Amount of remaining tokens allowed to spent
+    function allowance(address _owner, address _spender) public virtual view returns (uint256);
+}
+
+contract BalanceChecker {
+    /*
+      Check the token balances of wallet-token pairs.
+      Pass 0xeee... as a "token" address to get ETH balance.
+      Possible error throws:
+        - extremely large arrays for user and or tokens (gas cost too high)
+
+      Returns a one-dimensional that's user.length long.
+    */
+    function balances(address[] calldata users, address[] calldata tokens) external view returns (uint256[] memory) {
+        // make sure the users array and tokens array are of equal length
+        require(users.length == tokens.length, "users array is a different length than the tokens array");
+
+        uint256[] memory addrBalances = new uint256[](users.length);
+
+        for(uint i = 0; i < users.length; i++) {
+            if (tokens[i] != address(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE)) {
+                addrBalances[i] = IToken(tokens[i]).balanceOf(users[i]);
+            } else {
+                addrBalances[i] = users[i].balance; // ETH balance
+            }
+        }
+
+        return addrBalances;
+    }
+
+    /*
+      Check the allowances of an array of owner-spender-tokens
+      
+      Returns 0 for 0xeee... (ETH)
+      Possible error throws:
+        - extremely large arrays for user and or tokens (gas cost too high)
+
+      Returns a one-dimensional array that's owners.length long.
+    */
+    function allowances(address[] calldata owners, address[] calldata spenders, address[] calldata tokens) external view returns (uint256[] memory) {
+        // make sure the arrays are all of equal length
+        require(owners.length == spenders.length, "all arrays must be of equal length");
+        require(owners.length == tokens.length, "all arrays must be of equal length");
+
+        uint256[] memory addrAllowances = new uint256[](owners.length);
+
+        for(uint i = 0; i < owners.length; i++) {
+            if (tokens[i] != address(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE)) {
+                addrAllowances[i] = IToken(tokens[i]).allowance(owners[i], spenders[i]);
+            } else {
+                // ETH
+                addrAllowances[i] = 0;
+            }
+        }
+
+        return addrAllowances;
+    }
+
+
+}

packages/asset-swapper/package.json

@@ -36,9 +36,9 @@
         "publish:private": "yarn build && gitpkg publish"
     },
     "config": {
-        "publicInterfaceContracts": "ERC20BridgeSampler",
+        "publicInterfaceContracts": "ERC20BridgeSampler,BalanceChecker",
         "abis:comment": "This list is auto-generated by contracts-gen. Don't edit manually.",
-        "abis": "./test/generated-artifacts/@(ApproximateBuys|BalancerSampler|CurveSampler|DODOSampler|DeploymentConstants|DummyLiquidityProvider|ERC20BridgeSampler|Eth2DaiSampler|IBalancer|ICurve|IEth2Dai|IKyberNetwork|IMStable|IMooniswap|IMultiBridge|IShell|IUniswapExchangeQuotes|IUniswapV2Router01|KyberSampler|LiquidityProviderSampler|MStableSampler|MooniswapSampler|MultiBridgeSampler|NativeOrderSampler|SamplerUtils|ShellSampler|SushiSwapSampler|TestERC20BridgeSampler|TestNativeOrderSampler|TwoHopSampler|UniswapSampler|UniswapV2Sampler).json",
+        "abis": "./test/generated-artifacts/@(ApproximateBuys|BalanceChecker|BalancerSampler|CurveSampler|DODOSampler|DeploymentConstants|DummyLiquidityProvider|ERC20BridgeSampler|Eth2DaiSampler|IBalancer|ICurve|IEth2Dai|IKyberNetwork|IMStable|IMooniswap|IMultiBridge|IShell|IUniswapExchangeQuotes|IUniswapV2Router01|KyberSampler|LiquidityProviderSampler|MStableSampler|MooniswapSampler|MultiBridgeSampler|NativeOrderSampler|SamplerUtils|ShellSampler|SushiSwapSampler|TestERC20BridgeSampler|TestNativeOrderSampler|TwoHopSampler|UniswapSampler|UniswapV2Sampler).json",
         "postpublish": {
             "assets": []
         }

packages/asset-swapper/src/artifacts.ts

@@ -5,5 +5,9 @@
  */
 import { ContractArtifact } from 'ethereum-types';
 
+import * as BalanceChecker from '../generated-artifacts/BalanceChecker.json';
 import * as ERC20BridgeSampler from '../generated-artifacts/ERC20BridgeSampler.json';
-export const artifacts = { ERC20BridgeSampler: ERC20BridgeSampler as ContractArtifact };
+export const artifacts = {
+    ERC20BridgeSampler: ERC20BridgeSampler as ContractArtifact,
+    BalanceChecker: BalanceChecker as ContractArtifact,
+};

packages/asset-swapper/src/index.ts

@@ -177,7 +177,7 @@ export {
 } from './utils/quote_report_generator';
 export { QuoteRequestor } from './utils/quote_requestor';
 export { rfqtMocker } from './utils/rfqt_mocker';
-export { ERC20BridgeSamplerContract } from './wrappers';
+export { ERC20BridgeSamplerContract, BalanceCheckerContract } from './wrappers';
 import { ERC20BridgeSource } from './utils/market_operation_utils/types';
 export type Native = ERC20BridgeSource.Native;
 export type MultiHop = ERC20BridgeSource.MultiHop;

packages/asset-swapper/src/wrappers.ts

@@ -3,4 +3,5 @@
  * Warning: This file is auto-generated by contracts-gen. Don't edit manually.
  * -----------------------------------------------------------------------------
  */
+export * from '../generated-wrappers/balance_checker';
 export * from '../generated-wrappers/erc20_bridge_sampler';

packages/asset-swapper/test/artifacts.ts

@@ -6,6 +6,7 @@
 import { ContractArtifact } from 'ethereum-types';
 
 import * as ApproximateBuys from '../test/generated-artifacts/ApproximateBuys.json';
+import * as BalanceChecker from '../test/generated-artifacts/BalanceChecker.json';
 import * as BalancerSampler from '../test/generated-artifacts/BalancerSampler.json';
 import * as CurveSampler from '../test/generated-artifacts/CurveSampler.json';
 import * as DeploymentConstants from '../test/generated-artifacts/DeploymentConstants.json';
@@ -39,6 +40,7 @@ import * as UniswapSampler from '../test/generated-artifacts/UniswapSampler.json
 import * as UniswapV2Sampler from '../test/generated-artifacts/UniswapV2Sampler.json';
 export const artifacts = {
     ApproximateBuys: ApproximateBuys as ContractArtifact,
+    BalanceChecker: BalanceChecker as ContractArtifact,
     BalancerSampler: BalancerSampler as ContractArtifact,
     CurveSampler: CurveSampler as ContractArtifact,
     DODOSampler: DODOSampler as ContractArtifact,

packages/asset-swapper/test/contracts/balance_checker_test.ts

@@ -0,0 +1,60 @@
+import { artifacts as erc20Artifacts, DummyERC20TokenContract } from '@0x/contracts-erc20';
+import { blockchainTests, constants, expect, web3Wrapper } from '@0x/contracts-test-utils';
+import { BigNumber } from '@0x/utils';
+import * as _ from 'lodash';
+
+import { artifacts } from '../artifacts';
+import { BalanceCheckerContract } from '../wrappers';
+
+// tslint:disable: custom-no-magic-numbers
+
+const ETH_ADDRESS = '0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee';
+
+blockchainTests.resets('BalanceChecker contract', env => {
+    let contract: BalanceCheckerContract;
+
+    before(async () => {
+        contract = await BalanceCheckerContract.deployFrom0xArtifactAsync(
+            artifacts.BalanceChecker,
+            env.provider,
+            env.txDefaults,
+            {},
+        );
+    });
+
+    describe('getBalances', () => {
+        it('returns the correct array for a successful call', async () => {
+            const makerToken = await DummyERC20TokenContract.deployFrom0xArtifactAsync(
+                erc20Artifacts.DummyERC20Token,
+                env.provider,
+                env.txDefaults,
+                artifacts,
+                constants.DUMMY_TOKEN_NAME,
+                constants.DUMMY_TOKEN_SYMBOL,
+                new BigNumber(18),
+                constants.DUMMY_TOKEN_TOTAL_SUPPLY,
+            );
+
+            const accounts = await web3Wrapper.getAvailableAddressesAsync();
+            const owner = accounts[0];
+            const owner2 = accounts[1];
+
+            await makerToken.mint(new BigNumber(100)).awaitTransactionSuccessAsync({ from: owner });
+
+            const testResults = await contract.balances([owner, owner2], [makerToken.address, ETH_ADDRESS]).callAsync();
+
+            expect(testResults).to.eql([new BigNumber(100), new BigNumber(100000000000000000000)]);
+        });
+        it('it throws an error if the input arrays of different lengths', async () => {
+            const accounts = await web3Wrapper.getAvailableAddressesAsync();
+            const owner = accounts[0];
+
+            try {
+                await contract.balances([owner], [ETH_ADDRESS, ETH_ADDRESS]).callAsync();
+                expect.fail();
+            } catch (error) {
+                expect(error.message).to.eql('users array is a different length than the tokens array');
+            }
+        });
+    });
+});

packages/asset-swapper/test/wrappers.ts

@@ -4,6 +4,7 @@
  * -----------------------------------------------------------------------------
  */
 export * from '../test/generated-wrappers/approximate_buys';
+export * from '../test/generated-wrappers/balance_checker';
 export * from '../test/generated-wrappers/balancer_sampler';
 export * from '../test/generated-wrappers/curve_sampler';
 export * from '../test/generated-wrappers/d_o_d_o_sampler';

packages/asset-swapper/tsconfig.json

@@ -3,8 +3,10 @@
     "compilerOptions": { "outDir": "lib", "rootDir": ".", "resolveJsonModule": true },
     "include": ["./src/**/*", "./test/**/*", "./generated-wrappers/**/*"],
     "files": [
+        "generated-artifacts/BalanceChecker.json",
         "generated-artifacts/ERC20BridgeSampler.json",
         "test/generated-artifacts/ApproximateBuys.json",
+        "test/generated-artifacts/BalanceChecker.json",
         "test/generated-artifacts/BalancerSampler.json",
         "test/generated-artifacts/CurveSampler.json",
         "test/generated-artifacts/DODOSampler.json",