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feat(adapter): Add Curve trade adapter [SIM-173] (#238)
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‎contracts/interfaces/external/IStableSwapStEth.sol‎

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/*
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Copyright 2022 Set Labs Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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SPDX-License-Identifier: Apache License, Version 2.0
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*/
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pragma solidity 0.6.10;
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/**
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* Curve StableSwap pool for stETH.
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*/
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interface IStableSwapStEth {
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function exchange(
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int128 i,
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int128 j,
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uint256 dx,
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uint256 min_dy
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) external payable returns (uint256);
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function coins(uint256) external view returns (address);
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}

‎contracts/mocks/external/CurveStEthStableswapMock.sol‎

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/*
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Copyright 2022 Set Labs Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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SPDX-License-Identifier: Apache License, Version 2.0
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*/
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pragma solidity 0.6.10;
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import { Address } from "@openzeppelin/contracts/utils/Address.sol";
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import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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import { ReentrancyGuard } from "@openzeppelin/contracts/utils/ReentrancyGuard.sol";
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import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
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import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
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// Minimal Curve Eth/StEth Stableswap Pool
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contract CurveStEthStableswapMock is ReentrancyGuard {
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using SafeERC20 for IERC20;
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using SafeMath for uint256;
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using SafeMath for int128;
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using Address for address;
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address[] tokens;
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constructor(address[] memory _tokens) public {
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require(_tokens[1] != address(0));
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tokens = _tokens;
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}
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function add_liquidity(uint256[] memory _amounts, uint256 _min_mint_amount) payable external nonReentrant returns (uint256) {
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require(_amounts[0] == msg.value, "Eth sent should equal amount");
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IERC20(tokens[1]).safeTransferFrom(msg.sender, address(this), _amounts[1]);
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return _min_mint_amount;
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}
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/**
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* @dev Index values can be found via the `coins` public getter method
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* @param _i Index value for the coin to send
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* @param _j Index value of the coin to receive
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* @param _dx Amount of `i` being exchanged
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* @param _min_dy Minimum amount of `j` to receive
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* @return Actual amount of `j` received
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*/
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function exchange(int128 _i, int128 _j, uint256 _dx, uint256 _min_dy) payable external nonReentrant returns (uint256) {
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require(_i != _j);
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require(_dx == _min_dy);
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if (_i == 0 && _j == 1) {
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// The caller has sent eth receive stETH
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require(_dx == msg.value);
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IERC20(tokens[1]).safeTransfer(msg.sender, _dx);
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} else if (_j == 0 && _i == 1) {
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// The caller has sent stETH to receive ETH
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IERC20(tokens[1]).safeTransferFrom(msg.sender, address(this), _dx);
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Address.sendValue(msg.sender, _dx);
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} else {
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revert("Invalid index values");
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}
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return _dx;
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}
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/**
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* @param _index Index to look up address for.
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*
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* @return address Address of the token at index
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*/
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function coins(uint256 _index) external view returns (address) {
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return tokens[_index];
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}
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}

‎contracts/protocol/integration/exchange/CurveStEthExchangeAdapter.sol‎

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/*
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Copyright 2022 Set Labs Inc.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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SPDX-License-Identifier: Apache License, Version 2.0
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*/
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pragma solidity 0.6.10;
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pragma experimental "ABIEncoderV2";
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import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
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import { IStableSwapStEth } from "../../../interfaces/external/IStableSwapStEth.sol";
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import { IWETH } from "../../../interfaces/external/IWETH.sol";
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import { PreciseUnitMath } from "../../../lib/PreciseUnitMath.sol";
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/**
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* @title CurveStEthExchangeAdapter
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* @author FlattestWhite & ncitron
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*
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* Exchange adapter for the specialized Curve stETH <-> ETH
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* exchange contracts. Implements helper functionality for
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* wrapping and unwrapping WETH since the curve exchange uses
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* raw ETH.
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*
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* This contract is intended to be used by trade modules to rebalance
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* SetTokens that hold stETH as part of its components.
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*/
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contract CurveStEthExchangeAdapter {
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using SafeMath for uint256;
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using PreciseUnitMath for uint256;
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/* ========= State Variables ========= */
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// Address of WETH token.
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IWETH immutable public weth;
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// Address of stETH token.
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IERC20 immutable public stETH;
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// Address of Curve Eth/StEth stableswap pool.
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IStableSwapStEth immutable public stableswap;
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// Index for ETH for Curve stableswap pool.
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int128 internal constant ETH_INDEX = 0;
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// Index for stETH for Curve stableswap pool.
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int128 internal constant STETH_INDEX = 1;
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/* ========= Constructor ========== */
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/**
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* Set state variables
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*
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* @param _weth Address of WETH token
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* @param _stETH Address of stETH token
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* @param _stableswap Address of Curve Eth/StEth Stableswap pool
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*/
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constructor(
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IWETH _weth,
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IERC20 _stETH,
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IStableSwapStEth _stableswap
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)
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public
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{
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weth = _weth;
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stETH = _stETH;
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stableswap = _stableswap;
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require(_stableswap.coins(0) == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE, "Stableswap pool has invalid ETH_INDEX");
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require(_stableswap.coins(1) == address(_stETH), "Stableswap pool has invalid STETH_INDEX");
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_stETH.approve(address(_stableswap), PreciseUnitMath.maxUint256());
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}
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/* ======== External Functions ======== */
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/**
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* Buys stEth using WETH
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*
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* @param _sourceQuantity The amount of WETH as input.
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* @param _minDestinationQuantity The minimum amounnt of stETH to receive.
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* @param _destinationAddress The address to send the trade proceeds to.
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*/
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function buyStEth(
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uint256 _sourceQuantity,
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uint256 _minDestinationQuantity,
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address _destinationAddress
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)
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external
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{
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// transfer weth
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weth.transferFrom(msg.sender, address(this), _sourceQuantity);
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// unwrap weth
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weth.withdraw(_sourceQuantity);
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// buy stETH
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uint256 amountOut = stableswap.exchange{value: _sourceQuantity} (
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ETH_INDEX,
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STETH_INDEX,
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_sourceQuantity,
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_minDestinationQuantity
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);
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// transfer proceeds
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stETH.transfer(_destinationAddress, amountOut);
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}
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/**
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* Sells stETH for WETH
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*
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* @param _sourceQuantity The amount of stETH as input.
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* @param _minDestinationQuantity The minimum amount of WETH to receive.
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* @param _destinationAddress The address to send the trade proceeds to.
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*/
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function sellStEth(
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uint256 _sourceQuantity,
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uint256 _minDestinationQuantity,
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address _destinationAddress
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)
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external
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{
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// transfer stETH
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stETH.transferFrom(msg.sender, address(this), _sourceQuantity);
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// sell stETH
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uint256 amountOut = stableswap.exchange(STETH_INDEX, ETH_INDEX, _sourceQuantity, _minDestinationQuantity);
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// wrap eth
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weth.deposit{value: amountOut}();
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// transfer proceeds
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weth.transfer(_destinationAddress, amountOut);
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}
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/* ============ External Getter Functions ============ */
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/**
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* Calculate Curve trade encoded calldata. To be invoked on the SetToken.
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*
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* @param _sourceToken Either WETH or stETH. The input token.
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* @param _destinationToken Either WETH or stETH. The output token.
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* @param _destinationAddress The address where the proceeds of the output is sent to.
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* @param _sourceQuantity Amount of input token.
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* @param _minDestinationQuantity The minimum amount of output token to be received.
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*
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* @return address Target contract address
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* @return uint256 Call value
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* @return bytes Trade calldata
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*/
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function getTradeCalldata(
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address _sourceToken,
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address _destinationToken,
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address _destinationAddress,
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uint256 _sourceQuantity,
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uint256 _minDestinationQuantity,
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bytes memory /* data */
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)
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external
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view
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returns (address, uint256, bytes memory)
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{
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if (_sourceToken == address(weth) && _destinationToken == address(stETH)) {
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bytes memory callData = abi.encodeWithSignature(
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"buyStEth(uint256,uint256,address)",
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_sourceQuantity,
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_minDestinationQuantity,
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_destinationAddress
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);
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return (address(this), 0, callData);
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} else if (_sourceToken == address(stETH) && _destinationToken == address(weth)) {
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bytes memory callData = abi.encodeWithSignature(
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"sellStEth(uint256,uint256,address)",
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_sourceQuantity,
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_minDestinationQuantity,
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_destinationAddress
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);
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return (address(this), 0, callData);
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} else {
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revert("Must swap between weth and stETH");
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}
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}
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/**
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* Returns the address to approve source tokens to for trading. In this case, the address of this contract.
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*
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* @return address Address of the contract to approve tokens to.
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*/
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function getSpender() external view returns (address) {
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return address(this);
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}
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/**
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* This function is invoked when:
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* 1. WETH is withdrawn for ETH.
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* 2. ETH is received from Curve stableswap pool on exchange call.
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*/
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receive() external payable {}
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}

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