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DanielVFFranck Chastagnol
DanielVF
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Franck Chastagnol
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Flipper for zero slippage trading of OUSD for stablecoins (#558)
* Add flipper contract allow zero slippage trading of OUSD for stablecoins. * Comments on methods, removing unneeded constant. * Hide errors about tether not being ERC20 complient. * Deploy script 15 + Prod flipper contract * Fix deploy 15 logging * Fix slither error * Rinkeby deploy * mainnet abi * Fix comments in contract files Co-authored-by: Franck Chastagnol <[email protected]>
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‎contracts/contracts/flipper/Flipper.sol

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pragma solidity 0.5.11;
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import "../governance/Governable.sol";
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import "../token/OUSD.sol";
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import "../interfaces/Tether.sol";
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import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
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// Contract to exchange usdt, usdc, dai from and to ousd.
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// - 1 to 1. No slippage
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// - Optimized for low gas usage
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// - No guarantee of availability
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contract Flipper is Governable {
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using SafeERC20 for IERC20;
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uint256 constant MAXIMUM_PER_TRADE = (25000 * 1e18);
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// Saves approx 4K gas per swap by using hardcoded addresses.
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IERC20 dai = IERC20(0x6B175474E89094C44Da98b954EedeAC495271d0F);
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OUSD constant ousd = OUSD(0x2A8e1E676Ec238d8A992307B495b45B3fEAa5e86);
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IERC20 usdc = IERC20(0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48);
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Tether constant usdt = Tether(0xdAC17F958D2ee523a2206206994597C13D831ec7);
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// -----------
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// Constructor
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// -----------
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constructor() public {}
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// -----------------
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// Trading functions
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// -----------------
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/// @notice Purchase OUSD with Dai
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithDai(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(dai.transferFrom(msg.sender, address(this), amount));
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for Dai
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForDai(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(dai.transfer(msg.sender, amount));
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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/// @notice Purchase OUSD with USDC
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithUsdc(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// Potential rounding error is an intentional tradeoff
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require(usdc.transferFrom(msg.sender, address(this), amount / 1e12));
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for USDC
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForUsdc(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(usdc.transfer(msg.sender, amount / 1e12));
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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/// @notice Purchase OUSD with USDT
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithUsdt(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// Potential rounding error is an intentional tradeoff
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// USDT does not return a boolean and reverts,
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// so no need for a require.
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usdt.transferFrom(msg.sender, address(this), amount / 1e12);
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for USDT
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForUsdt(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// USDT does not return a boolean and reverts,
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// so no need for a require.
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usdt.transfer(msg.sender, amount / 1e12);
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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// --------------------
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// Governance functions
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// --------------------
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/// @dev Opting into yield reduces the gas cost per transfer by about 4K, since
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/// ousd needs to do less accounting and one less storage write.
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function rebaseOptIn() external onlyGovernor nonReentrant {
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ousd.rebaseOptIn();
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}
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/// @notice Owner function to withdraw a specific amount of a token
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function withdraw(address token, uint256 amount)
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external
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onlyGovernor
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nonReentrant
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{
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IERC20(token).safeTransfer(_governor(), amount);
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}
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/// @notice Owner function to withdraw all tradable tokens
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/// @dev Equivalent to "pausing" the contract.
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function withdrawAll() external onlyGovernor nonReentrant {
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IERC20(dai).safeTransfer(_governor(), dai.balanceOf(address(this)));
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IERC20(ousd).safeTransfer(_governor(), ousd.balanceOf(address(this)));
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IERC20(address(usdt)).safeTransfer(
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_governor(),
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usdt.balanceOf(address(this))
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);
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IERC20(usdc).safeTransfer(_governor(), usdc.balanceOf(address(this)));
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}
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}

‎contracts/contracts/flipper/FlipperDev.sol

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pragma solidity 0.5.11;
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import "../governance/Governable.sol";
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import "../token/OUSD.sol";
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import "../interfaces/Tether.sol";
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import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
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import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
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// Contract to exchange usdt, usdc, dai from and to ousd.
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// - 1 to 1. No slippage
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// - Optimized for low gas usage
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// - No guarantee of availability
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contract FlipperDev is Governable {
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using SafeERC20 for IERC20;
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uint256 constant MAXIMUM_PER_TRADE = (25000 * 1e18);
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// Settable coin addresses allow easy testing and use of mock currencies.
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IERC20 dai = IERC20(0);
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OUSD ousd = OUSD(0);
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IERC20 usdc = IERC20(0);
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Tether usdt = Tether(0);
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// ---------------------
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// Dev constructor
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// ---------------------
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constructor(
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address dai_,
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address ousd_,
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address usdc_,
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address usdt_
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) public {
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dai = IERC20(dai_);
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ousd = OUSD(ousd_);
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usdc = IERC20(usdc_);
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usdt = Tether(usdt_);
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require(address(ousd) != address(0));
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require(address(dai) != address(0));
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require(address(usdc) != address(0));
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require(address(usdt) != address(0));
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}
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// -----------------
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// Trading functions
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// -----------------
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/// @notice Purchase OUSD with Dai
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithDai(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(dai.transferFrom(msg.sender, address(this), amount));
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for Dai
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForDai(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(dai.transfer(msg.sender, amount));
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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/// @notice Purchase OUSD with USDC
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithUsdc(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// Potential rounding error is an intentional tradeoff
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require(usdc.transferFrom(msg.sender, address(this), amount / 1e12));
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for USDC
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForUsdc(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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require(usdc.transfer(msg.sender, amount / 1e12));
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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/// @notice Purchase OUSD with USDT
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/// @param amount Amount of OUSD to purchase, in 18 fixed decimals.
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function buyOusdWithUsdt(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// Potential rounding error is an intentional tradeoff
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// USDT does not return a boolean and reverts,
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// so no need for a require.
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usdt.transferFrom(msg.sender, address(this), amount / 1e12);
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require(ousd.transfer(msg.sender, amount));
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}
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/// @notice Sell OUSD for USDT
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/// @param amount Amount of OUSD to sell, in 18 fixed decimals.
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function sellOusdForUsdt(uint256 amount) external {
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require(amount <= MAXIMUM_PER_TRADE, "Amount too large");
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// USDT does not return a boolean and reverts,
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// so no need for a require.
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usdt.transfer(msg.sender, amount / 1e12);
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require(ousd.transferFrom(msg.sender, address(this), amount));
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}
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// --------------------
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// Governance functions
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// --------------------
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/// @dev Opting into yield reduces the gas cost per transfer by about 4K, since
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/// ousd needs to do less accounting and one less storage write.
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function rebaseOptIn() external onlyGovernor nonReentrant {
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ousd.rebaseOptIn();
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}
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/// @notice Owner function to withdraw a specific amount of a token
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function withdraw(address token, uint256 amount)
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external
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onlyGovernor
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nonReentrant
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{
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IERC20(token).safeTransfer(_governor(), amount);
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}
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/// @notice Owner function to withdraw all tradable tokens
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/// @dev Equivalent to "pausing" the contract.
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function withdrawAll() external onlyGovernor nonReentrant {
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IERC20(dai).safeTransfer(_governor(), dai.balanceOf(address(this)));
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IERC20(ousd).safeTransfer(_governor(), ousd.balanceOf(address(this)));
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IERC20(address(usdt)).safeTransfer(
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_governor(),
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usdt.balanceOf(address(this))
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);
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IERC20(usdc).safeTransfer(_governor(), usdc.balanceOf(address(this)));
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}
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}

‎contracts/contracts/interfaces/Tether.sol

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pragma solidity 0.5.11;
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interface Tether {
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function transfer(address to, uint256 value) external;
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function transferFrom(
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address from,
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address to,
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uint256 value
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) external;
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function balanceOf(address) external returns (uint256);
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}

‎contracts/deploy/001_core.js

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log("Initialized OUSD");
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};
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// Deploy the Flipper trading contract
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const deployFlipper = async () => {
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const assetAddresses = await getAssetAddresses(deployments);
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const { governorAddr } = await hre.getNamedAccounts();
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const sGovernor = await ethers.provider.getSigner(governorAddr);
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const ousd = await ethers.getContract("OUSDProxy");
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await deployWithConfirmation("FlipperDev", [
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assetAddresses.DAI,
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ousd.address,
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assetAddresses.USDC,
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assetAddresses.USDT,
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]);
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const flipper = await ethers.getContract("FlipperDev");
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await withConfirmation(flipper.transferGovernance(governorAddr));
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await withConfirmation(flipper.connect(sGovernor).claimGovernance());
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};
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const main = async () => {
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console.log("Running 001_core deployment...");
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await deployOracles();
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await deployAaveStrategy();
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await deployThreePoolStrategy();
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await configureVault();
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await deployFlipper();
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console.log("001_core deploy done.");
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return true;
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};

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