✨ swapper: swap ETH for EXA on velodrome

Co-authored-by: Santiago Sanchez Avalos <santisanchezavalos@gmail.com>

.changeset/eleven-dots-deliver.md

@@ -0,0 +1,5 @@
+---
+"@exactly/protocol": patch
+---
+
+✨ swapper: swap `ETH` for `EXA` on velodrome

.gas-snapshot

@@ -411,4 +411,9 @@ RewardsControllerTest:testUpdateWithTotalDebtZeroShouldUpdateLastUndistributed()
 RewardsControllerTest:testUtilizationEqualZero() (gas: 622308)
 RewardsControllerTest:testWithTwelveFixedPools() (gas: 3989456)
 RewardsControllerTest:testWithdrawAllRewardBalance() (gas: 47146)
-RewardsControllerTest:testWithdrawOnlyAdminRole() (gas: 84719)
+RewardsControllerTest:testWithdrawOnlyAdminRole() (gas: 84719)
+SwapperTest:testSwapBasic() (gas: 187376)
+SwapperTest:testSwapWithInaccurateSlippageSendsETHToAccount() (gas: 207789)
+SwapperTest:testSwapWithKeepAmount() (gas: 194032)
+SwapperTest:testSwapWithKeepEqualToValue() (gas: 79362)
+SwapperTest:testSwapWithKeepHigherThanValue() (gas: 34589)

contracts/periphery/Swapper.sol

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity 0.8.17;
+
+import { WETH, ERC20 } from "solmate/src/tokens/WETH.sol";
+import { SafeTransferLib } from "solmate/src/utils/SafeTransferLib.sol";
+
+contract Swapper {
+  using SafeTransferLib for address payable;
+  using SafeTransferLib for WETH;
+
+  /// @notice The EXA asset.
+  /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
+  ERC20 public immutable exa;
+  /// @notice The WETH asset.
+  /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
+  WETH public immutable weth;
+  /// @notice The liquidity pool.
+  /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
+  IPool public immutable pool;
+
+  /// @custom:oz-upgrades-unsafe-allow constructor
+  constructor(ERC20 exa_, WETH weth_, IPool pool_) {
+    exa = exa_;
+    weth = weth_;
+    pool = pool_;
+  }
+
+  /// @notice Swaps `msg.value` ETH for EXA and sends it to `account`.
+  /// @param account The account to send the EXA to.
+  /// @param minEXA The minimum amount of EXA to receive.
+  /// @param keepETH The amount of ETH to send to `account` (ex: for gas).
+  function swap(address payable account, uint256 minEXA, uint256 keepETH) external payable {
+    if (keepETH > msg.value) return account.safeTransferETH(msg.value);
+
+    uint256 inETH = msg.value - keepETH;
+    uint256 outEXA = pool.getAmountOut(inETH, weth);
+    if (outEXA < minEXA) return account.safeTransferETH(msg.value);
+
+    weth.deposit{ value: inETH }();
+    weth.safeTransfer(address(pool), inETH);
+
+    (uint256 amount0Out, uint256 amount1Out) = address(exa) < address(weth)
+      ? (outEXA, uint256(0))
+      : (uint256(0), outEXA);
+    try pool.swap(amount0Out, amount1Out, account, "") {
+      account.safeTransferETH(keepETH);
+    } catch {
+      account.safeTransferETH(msg.value);
+    }
+  }
+}
+
+interface IPool {
+  function swap(uint256 amount0Out, uint256 amount1Out, address to, bytes calldata data) external;
+
+  function getAmountOut(uint256 amountIn, WETH tokenIn) external view returns (uint256);
+}

test/solidity/Swapper.t.sol

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity 0.8.17;
+
+import { ForkTest } from "./Fork.t.sol";
+import { FixedPointMathLib } from "solmate/src/utils/FixedPointMathLib.sol";
+import { Swapper, IPool, ERC20, WETH } from "../../contracts/periphery/Swapper.sol";
+
+contract SwapperTest is ForkTest {
+  using FixedPointMathLib for uint256;
+
+  ERC20 internal exa;
+  WETH internal weth;
+  IPool internal pool;
+  Swapper internal swapper;
+
+  function setUp() external {
+    vm.createSelectFork(vm.envString("OPTIMISM_NODE"), 107_385_046);
+
+    exa = ERC20(deployment("EXA"));
+    weth = WETH(payable(deployment("WETH")));
+    pool = IPool(deployment("EXAPool"));
+    swapper = new Swapper(exa, weth, pool);
+
+    deal(address(weth), address(this), 500 ether);
+  }
+
+  function testSwapBasic() external _checkBalance {
+    uint256 balanceETH = address(this).balance;
+    uint256 amountEXA = pool.getAmountOut(1 ether, weth);
+    swapper.swap{ value: 1 ether }(payable(address(this)), 0, 0);
+
+    assertEq(address(this).balance, balanceETH - 1 ether, "eth spent");
+    assertEq(exa.balanceOf(address(this)), amountEXA, "exa received");
+  }
+
+  function testSwapWithKeepAmount() external _checkBalance {
+    uint256 balanceETH = address(this).balance;
+    uint256 amountEXA = pool.getAmountOut(0.9 ether, weth);
+    swapper.swap{ value: 1 ether }(payable(address(this)), 0, 0.1 ether);
+
+    assertEq(address(this).balance, balanceETH - 0.9 ether, "eth spent");
+    assertEq(exa.balanceOf(address(this)), amountEXA, "exa received");
+  }
+
+  function testSwapWithKeepEqualToValue() external _checkBalance {
+    uint256 balanceETH = address(this).balance;
+    swapper.swap{ value: 1 ether }(payable(address(this)), 0, 1 ether);
+
+    assertEq(address(this).balance, balanceETH, "eth spent");
+    assertEq(exa.balanceOf(address(this)), 0, "exa received");
+  }
+
+  function testSwapWithKeepHigherThanValue() external _checkBalance {
+    uint256 balanceETH = address(this).balance;
+    swapper.swap{ value: 1 ether }(payable(address(this)), 0, 2 ether);
+
+    assertEq(address(this).balance, balanceETH, "eth spent");
+    assertEq(exa.balanceOf(address(this)), 0, "exa received");
+  }
+
+  function testSwapWithInaccurateSlippageSendsETHToAccount() external _checkBalance {
+    uint256 balanceETH = address(this).balance;
+    uint256 amountEXA = pool.getAmountOut(1 ether, weth);
+
+    swapper.swap{ value: 1 ether }(payable(address(this)), amountEXA * 5, 0);
+    assertEq(address(this).balance, balanceETH, "eth spent");
+    assertEq(exa.balanceOf(address(this)), 0, "exa received");
+
+    swapper.swap{ value: 1 ether }(payable(address(this)), amountEXA - 10e18, 0);
+    assertEq(address(this).balance, balanceETH - 1 ether, "eth spent");
+    assertEq(exa.balanceOf(address(this)), amountEXA, "exa received");
+  }
+
+  modifier _checkBalance() {
+    _;
+    assertEq(address(swapper).balance, 0);
+  }
+
+  // solhint-disable-next-line no-empty-blocks
+  receive() external payable {}
+}