refactored smart contract

migrations/2_deploy_contracts.js

@@ -3,5 +3,5 @@ const sushiAddress = "0xd9e1cE17f2641f24aE83637ab66a2cca9C378B9F"
 const usdcAddress = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
 const wethAddress = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"
 module.exports = function (deployer) {
-  deployer.deploy(DexAggregator, sushiAddress, usdcAddress, wethAddress)
+  deployer.deploy(DexAggregator, sushiAddress, usdcAddress)
 };

src/abis/Migrations.json

@@ -2311,8 +2311,8 @@
     "1": {
       "events": {},
       "links": {},
-      "address": "0x7a03F2Ab01ce33f66Bae50912c722b565318015F",
-      "transactionHash": "0xc8c7e16cb230c020a4bae7497e9294c695732abfa4fe7742dd1aa55594fe24b6"
+      "address": "0x0740d4C5416569A011E47B98190835261E995033",
+      "transactionHash": "0xd795c6d195bc53229c514c52f58d503b7ee7cafd90c6dd2d33c026eaed441305"
     },
     "1640296764925": {
       "events": {},
@@ -2322,7 +2322,7 @@
     }
   },
   "schemaVersion": "3.4.3",
-  "updatedAt": "2022-01-14T18:01:13.238Z",
+  "updatedAt": "2022-01-20T22:28:08.673Z",
   "networkType": "ethereum",
   "devdoc": {
     "kind": "dev",

src/components/App.js

@@ -11,6 +11,7 @@ const usdcAddress = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
 const wethAddress = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"
 const exchangeDataReset = {        
   outputsLoading: false,
+  dexIndexWithBestPrice: '0',
   uniOutput: '0',
   sushiOutput: '0',
 }
@@ -88,14 +89,17 @@ class App extends Component {
     let data = this.state.exchangeData
     if(input !== '0' ){
       this.setState({ exchangeData: {...data, outputsLoading: true }})
-      const outputs = await this.state.dexAggregator.methods.getReturnAmounts(input, pairArray).call()
-      console.log(outputs)
+      const result = await this.state.dexAggregator.methods.getOutputAmounts(input, pairArray).call()
+      const index = result[0].toString()
+      const amounts = result[1]
+      console.log(result)
       this.setState({ 
         exchangeData: {
           ...data,
           outputsLoading: false,
-          uniOutput: outputs[0],
-          sushiOutput: outputs[1]
+          dexIndexWithBestPrice: index,
+          uniOutput: index === "0" ? amounts[0] : amounts[1],
+          sushiOutput: index === "0" ? amounts[1] : amounts[0]
         }
       })
     } else {

src/components/BuyForm.js

@@ -94,6 +94,7 @@ class BuyForm extends Component {
   render() {
     const {
       outputsLoading,
+      dexIndexWithBestPrice,
       uniOutput,
       sushiOutput
     } = this.props.exchangeData
@@ -147,7 +148,7 @@ class BuyForm extends Component {
           </span>
         </div>
         <div>
-          {window.web3.utils.fromWei(uniOutput, "ether") > window.web3.utils.fromWei(sushiOutput, "ether")
+          { dexIndexWithBestPrice === "0"
             ? renderOutputForms(uniOutput, sushiOutput, this.state.etherAmount, outputsLoading, ['Uniswap', 'SushiSwap'])
             : renderOutputForms(sushiOutput, uniOutput, this.state.etherAmount, outputsLoading, ['SushiSwap', 'Uniswap'])
           }

src/components/SellForm.js

@@ -94,6 +94,7 @@ class SellForm extends Component {
   render() {
     const {
       outputsLoading,
+      dexIndexWithBestPrice,
       uniOutput,
       sushiOutput
     } = this.props.exchangeData
@@ -147,7 +148,7 @@ class SellForm extends Component {
           </span>
         </div>
         <div>
-          {(uniOutput > sushiOutput)
+          { dexIndexWithBestPrice === "0"
             ? renderOutputForms(uniOutput, sushiOutput, this.state.usdcAmount, outputsLoading, ['Uniswap', 'SushiSwap'])
             : renderOutputForms(sushiOutput, uniOutput, this.state.usdcAmount, outputsLoading, ['SushiSwap', 'Uniswap'])
           }

src/contracts/DexAggregator.sol

@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: MIT
-pragma solidity 0.8.11;
+pragma solidity ^0.8.11;
 import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 //Code for the shared dex interface of sushiSwap and uniSwap.
 interface IDex {
+    function WETH() external pure returns (address);
     function swapTokensForExactETH(uint amountOut, uint amountInMax, address[] calldata path, address to, uint deadline)
         external
         returns (uint[] memory amounts);
@@ -13,69 +14,69 @@ interface IDex {
     function getAmountsOut(uint amountIn, address[] calldata path) external view returns (uint[] memory amounts);
 }
 contract DexAggregator {
-    address public immutable sushiAddress;
-    address public immutable usdcAddress;
+    // Uniswap at index 0 and sushiswap at index 1
+    IDex[2] public Dexes;
+    IERC20 public immutable usdc;
     address public immutable wethAddress;
-    address public constant UNI_ADDRESS = address(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
     /// @notice USDCBought event emitted on successful ETH to USDC swap. 
     event USDCBought(
         uint256 usdcAmountBought, 
         uint256 ethAmountSold,
         address dex, 
-        uint256 nextBestUsdcReturn
+        uint256 nextBestUsdcOutput
     );
     /// @notice USDCSold event emitted on successful USDC to ETH swap.    
     event USDCSold(
         uint256 ethAmountBought,
         uint256 usdcAmountSold, 
         address dex, 
-        uint256 nextBestEthReturn
+        uint256 nextBestEthOutput
     );
-    constructor (address _sushiAddress, address _usdcAddress, address _wethAddress) {
-        sushiAddress = _sushiAddress;
-        usdcAddress = _usdcAddress;
-        wethAddress = _wethAddress;
+    // Don't need to pass uni address to constructor b/c its the same across all networks.
+    constructor (address _sushiAddress, address _usdcAddress) {
+        // Don't need to pass uni address to constructor b/c its the same across all networks.
+        Dexes[0] = IDex(address(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D)); 
+        Dexes[1] = IDex(_sushiAddress);
+        wethAddress = Dexes[0].WETH();
+        usdc = IERC20(_usdcAddress);
     }
+    // important to recieve refunded ETH from either dex
     receive() external payable {}
-    function getReturnAmounts(uint _amountIn, address[] calldata _path) public view returns(uint _uniAmount, uint _sushiAmount){
-        uint[] memory _uniAmounts = IDex(UNI_ADDRESS).getAmountsOut(_amountIn, _path);
-        uint[] memory _sushiAmounts = IDex(sushiAddress).getAmountsOut(_amountIn, _path);
-        _uniAmount = _uniAmounts[1];
-        _sushiAmount = _sushiAmounts[1];
+    // Function that returns the index of the exchange with the highest output amount and the output amount from each exchange in an array
+    function getOutputAmounts(uint _amountIn, address[] calldata _path) public view returns(uint8 _bestPriceDex, uint[] memory _amounts){
+        //Create new in memory array of length 2
+        _amounts = new uint[] (2);
+        // fetch output amounts from each exchange
+        _amounts[0] = (Dexes[0].getAmountsOut(_amountIn, _path))[1];
+        _amounts[1] = (Dexes[1].getAmountsOut(_amountIn, _path))[1];
+        // If sushi amount is greater than uni amount, swap order of amounts array and set dex which offers the greater output index 0 (sushi)
+        if(_amounts[1] > _amounts[0]) {
+            _amounts[0] = _amounts[1];
+            _amounts[1] = (Dexes[0].getAmountsOut(_amountIn, _path))[1];
+            _bestPriceDex = 1;
+        }
     }
     function buyUSDCAtBestPrice(uint _deadline,address[] calldata _path) external payable {
-        require(_path[0] == wethAddress && _path[1] == usdcAddress, "Wrong token pair array");
-        // get USDC return amounts for each exchange
-        (uint _uniUSDCAmount, uint _sushiUSDCAmount) = getReturnAmounts(msg.value, _path);
-        // determine which exchange offers the greater return then route the swap to that exchange.
-        if(_uniUSDCAmount > _sushiUSDCAmount) {
-            IDex(UNI_ADDRESS).swapETHForExactTokens{ value: msg.value }(_uniUSDCAmount, _path, msg.sender, _deadline);
-            emit USDCBought(_uniUSDCAmount, msg.value, UNI_ADDRESS, _sushiUSDCAmount);
-        } else {
-            IDex(sushiAddress).swapETHForExactTokens{ value: msg.value }(_sushiUSDCAmount, _path, msg.sender, _deadline);
-            emit USDCBought(_sushiUSDCAmount, msg.value, sushiAddress, _uniUSDCAmount);
-        }
+        require(_path[0] == wethAddress && _path[1] == address(usdc), "Wrong token pair array");
+        // get dex with best USDC price and output amounts for each exchange
+        (uint8 _dex, uint[] memory _USDCAmounts) = getOutputAmounts(msg.value, _path);
+        // Route trade to dex with best USDC price
+        Dexes[_dex].swapETHForExactTokens{ value: msg.value }(_USDCAmounts[0], _path, msg.sender, _deadline);
+        emit USDCBought(_USDCAmounts[0], msg.value, address(Dexes[_dex]), _USDCAmounts[1]);
         // refund leftover ETH to user
         payable(msg.sender).transfer(address(this).balance);
     }
     function sellUSDCAtBestPrice(uint _USDCAmount, uint _deadline, address[] calldata _path) external {
-        require(_path[1] == wethAddress && _path[0] == usdcAddress, "Wrong token pair array");
-        require(IERC20(usdcAddress).balanceOf(msg.sender) >= _USDCAmount, "Error, can't sell more USDC than owned");
+        require(_path[1] == wethAddress && _path[0] == address(usdc), "Wrong token pair array");
+        require(usdc.balanceOf(msg.sender) >= _USDCAmount, "Error, can't sell more USDC than owned");
         // Transfer the usdc amount from the user to this contract. 
-        require(IERC20(usdcAddress).transferFrom(msg.sender, address(this), _USDCAmount));
-        // get ETH return amounts for each exchange
-        (uint _uniETHAmount, uint _sushiETHAmount) = getReturnAmounts(_USDCAmount, _path);
-        // determine which exchange offers the greater return then route the swap to that exchange.
-        if(_uniETHAmount > _sushiETHAmount) {
-            // approve Uni to spend USDC tokens
-            require(IERC20(usdcAddress).approve(UNI_ADDRESS, _USDCAmount), 'approve failed.');
-            IDex(UNI_ADDRESS).swapTokensForExactETH(_uniETHAmount, _USDCAmount, _path, msg.sender, _deadline);
-            emit USDCSold(_uniETHAmount, _USDCAmount, UNI_ADDRESS, _sushiETHAmount);
-        } else {
-            // approve Sushi to spend USDC tokens
-            require(IERC20(usdcAddress).approve(sushiAddress, _USDCAmount), 'approve failed.');
-            IDex(sushiAddress).swapTokensForExactETH(_sushiETHAmount, _USDCAmount, _path, msg.sender, _deadline);
-            emit USDCSold(_sushiETHAmount, _USDCAmount, sushiAddress, _uniETHAmount);
-        }
+        require(usdc.transferFrom(msg.sender, address(this), _USDCAmount));
+        // get dex with best ETH price and output amounts for each exchange
+        (uint8 _dex, uint[] memory _ETHAmounts) = getOutputAmounts(_USDCAmount, _path);
+        // approve dex with best ETH price to spend USDC tokens
+        require(usdc.approve(address(Dexes[_dex]), _USDCAmount), 'approve failed.');
+        // Route trade to dex with best ETH price
+        Dexes[_dex].swapTokensForExactETH(_ETHAmounts[0], _USDCAmount, _path, msg.sender, _deadline);
+        emit USDCSold(_ETHAmounts[0], _USDCAmount, address(Dexes[_dex]), _ETHAmounts[1]);
     }
 }