[API-4248] Wrap and unwrap ETH

SwapRouter/script/Deploy.s.sol

@@ -11,7 +11,9 @@ contract SwapRouterDeploy is Script {
     function run() external {
         vm.startBroadcast();
 
-        SkipGoSwapRouter router = SkipGoSwapRouter(0xa11CC0eFb1B3AcD95a2B8cd316E8c132E16048b5);
+        address weth = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
+
+        SkipGoSwapRouter router = new SkipGoSwapRouter(weth);
 
         UniswapV2Adapter uniswapV2Adapter = new UniswapV2Adapter();
         UniswapV3Adapter uniswapV3Adapter = new UniswapV3Adapter();

SwapRouter/src/SkipGoSwapRouter.sol

@@ -5,6 +5,7 @@ import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
 
 import {IAdapter} from "./interfaces/IAdapter.sol";
+import {IWETH} from "./interfaces/IWETH.sol";
 
 contract SkipGoSwapRouter is Ownable {
     enum ExchangeType {
@@ -14,6 +15,8 @@ contract SkipGoSwapRouter is Ownable {
 
     mapping(ExchangeType => address) public adapters;
 
+    address public weth;
+
     struct Hop {
         ExchangeType exchangeType;
         bytes data;
@@ -24,7 +27,11 @@ contract SkipGoSwapRouter is Ownable {
         uint256 feeBPS;
     }
 
-    constructor() Ownable(msg.sender) {}
+    constructor(address _weth) Ownable(msg.sender) {
+        weth = _weth;
+    }
+
+    receive() external payable {}
 
     function swapExactIn(
         uint256 amountIn,
@@ -34,7 +41,15 @@ contract SkipGoSwapRouter is Ownable {
         Hop[] calldata hops,
         Affiliate[] calldata affiliates
     ) external payable returns (uint256 amountOut) {
-        IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
+        // if token in is ETH, msg.value must be equal to amountIn
+        // if token in is not ETH, msg.value must be 0
+        require(msg.value == (tokenIn == address(0) ? amountIn : 0), "invalid msg.value");
+
+        if (tokenIn == address(0)) {
+            IWETH(weth).deposit{value: amountIn}();
+        } else {
+            IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
+        }
 
         amountOut = amountIn;
 
@@ -61,9 +76,14 @@ contract SkipGoSwapRouter is Ownable {
 
         uint256 amountPaid = _payAffiliateFees(tokenOut, amountOut, affiliates);
 
-        IERC20(tokenOut).transfer(msg.sender, amountOut - amountPaid);
-
         amountOut = amountOut - amountPaid;
+
+        if (tokenOut == address(0)) {
+            IWETH(weth).withdraw(amountOut);
+            payable(msg.sender).transfer(amountOut);
+        } else {
+            IERC20(tokenOut).transfer(msg.sender, amountOut);
+        }
     }
 
     function swapExactOut(
@@ -78,7 +98,13 @@ contract SkipGoSwapRouter is Ownable {
 
         require(amountIn <= amountInMax, "amount in is greater than amount in max");
 
-        IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
+        if (tokenIn == address(0)) {
+            require(msg.value >= amountIn, "msg.value is less than amount in");
+            IWETH(weth).deposit{value: amountIn}();
+        } else {
+            require(msg.value == 0, "msg.value must be 0");
+            IERC20(tokenIn).transferFrom(msg.sender, address(this), amountIn);
+        }
 
         amountOut = amountIn;
 
@@ -103,7 +129,19 @@ contract SkipGoSwapRouter is Ownable {
 
         uint256 amountPaid = _payAffiliateFees(tokenOut, amountOut, affiliates);
 
-        IERC20(tokenOut).transfer(msg.sender, amountOut - amountPaid);
+        uint256 amountOutAfterFees = amountOut - amountPaid;
+
+        if (tokenOut == address(0)) {
+            IWETH(weth).withdraw(amountOutAfterFees);
+            payable(msg.sender).transfer(amountOutAfterFees);
+        } else {
+            IERC20(tokenOut).transfer(msg.sender, amountOutAfterFees);
+        }
+
+        // refund unused ETH
+        if (tokenIn == address(0) && msg.value > amountIn) {
+            payable(msg.sender).transfer(msg.value - amountIn);
+        }
     }
 
     function getAmountOut(uint256 amountIn, Hop[] calldata hops) public view returns (uint256 amountOut) {

SwapRouter/src/adapters/UniswapV2Adapter.sol

@@ -13,7 +13,7 @@ contract UniswapV2Adapter {
         uint256 fee;
     }
 
-    function swapExactIn(uint256 amountIn, bytes calldata data) external returns (uint256 amountOut) {
+    function swapExactIn(uint256 amountIn, bytes calldata data) external payable returns (uint256 amountOut) {
         UniswapV2Data memory uniswapV2Data = abi.decode(data, (UniswapV2Data));
 
         (uint112 reserve0, uint112 reserve1,) = IUniswapV2Pair(uniswapV2Data.pool).getReserves();

SwapRouter/src/adapters/UniswapV3Adapter.sol

@@ -15,7 +15,7 @@ contract UniswapV3Adapter {
         address swapRouter;
     }
 
-    function swapExactIn(uint256 amountIn, bytes calldata data) external returns (uint256 amountOut) {
+    function swapExactIn(uint256 amountIn, bytes calldata data) external payable returns (uint256 amountOut) {
         UniswapV3Data memory uniswapV3Data = abi.decode(data, (UniswapV3Data));
 
         IERC20(uniswapV3Data.tokenIn).approve(uniswapV3Data.swapRouter, amountIn);

SwapRouter/src/interfaces/IWETH.sol

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2015, 2016, 2017 Dapphub
+// Adapted by Ethereum Community 2021
+pragma solidity ^0.8.0;
+
+/// @dev Wrapped Ether v10 (WETH10) is an Ether (ETH) ERC-20 wrapper. You can `deposit` ETH and obtain a WETH10 balance which can then be operated as an ERC-20 token. You can
+/// `withdraw` ETH from WETH10, which will then burn WETH10 token in your wallet. The amount of WETH10 token in any wallet is always identical to the
+/// balance of ETH deposited minus the ETH withdrawn with that specific wallet.
+interface IWETH {
+    /// @dev `msg.value` of ETH sent to this contract grants caller account a matching increase in WETH10 token balance.
+    /// Emits {Transfer} event to reflect WETH10 token mint of `msg.value` from `address(0)` to caller account.
+    function deposit() external payable;
+
+    /// @dev Burn `value` WETH10 token from caller account and withdraw matching ETH to the same.
+    /// Emits {Transfer} event to reflect WETH10 token burn of `value` to `address(0)` from caller account.
+    /// Requirements:
+    ///   - caller account must have at least `value` balance of WETH10 token.
+    function withdraw(uint256 value) external;
+}