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| // SPDX-License-Identifier: BlueOak-1.0.0
pragma solidity 0.8.17;
import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import "@openzeppelin/contracts/utils/math/Math.sol";
import "@openzeppelin/contracts-upgradeable/token/ERC20/utils/SafeERC20Upgradeable.sol";
import "../../libraries/Fixed.sol";
import "../../interfaces/IBroker.sol";
import "../../interfaces/IGnosis.sol";
import "../../interfaces/ITrade.sol";
enum TradeStatus {
NOT_STARTED, // before init()
OPEN, // after init() and before settle()
CLOSED, // after settle()
PENDING // during init() or settle() (reentrancy protection)
}
// Modifications to this contract's state must only ever be made when status=PENDING!
/// Trade contract against the Gnosis EasyAuction mechanism
contract GnosisTrade is ITrade {
using FixLib for uint192;
using SafeERC20Upgradeable for IERC20Upgradeable;
// ==== Constants
uint256 public constant FEE_DENOMINATOR = 1000;
// Upper bound for the max number of orders we're happy to have the auction clear in;
// When we have good price information, this determines the minimum buy amount per order.
uint96 public constant MAX_ORDERS = 1e5;
// raw "/" for compile-time const
uint192 public constant DEFAULT_MIN_BID = FIX_ONE / 100; // {tok}
// ==== status: This contract's state-machine state. See TradeStatus enum, above
TradeStatus public status;
// ==== The rest of contract state is all parameters that are immutable after init()
// == Metadata
IGnosis public gnosis; // Gnosis Auction contract
uint256 public auctionId; // The Gnosis Auction ID returned by gnosis.initiateAuction()
IBroker public broker; // The Broker that cloned this contract into existence
// == Economic parameters
// This trade is on behalf of origin. Only origin may call settle(), and the `buy` tokens
// from this trade's acution will all eventually go to origin.
address public origin;
IERC20Metadata public sell; // address of token this trade is selling
IERC20Metadata public buy; // address of token this trade is buying
uint256 public initBal; // {qTok}, this trade's balance of `sell` when init() was called
uint48 public endTime; // timestamp after which this trade's auction can be settled
uint192 public worstCasePrice; // {buyTok/sellTok}, the worst price we expect to get at Auction
// We expect Gnosis Auction either to meet or beat worstCasePrice, or to return the `sell`
// tokens. If we actually *get* a worse clearing that worstCasePrice, we consider it an error in
// our trading scheme and call broker.reportViolation()
// This modifier both enforces the state-machine pattern and guards against reentrancy.
modifier stateTransition(TradeStatus begin, TradeStatus end) {
require(status == begin, "Invalid trade state");
status = TradeStatus.PENDING;
_;
assert(status == TradeStatus.PENDING);
status = end;
}
/// Constructor function, can only be called once
/// @dev Expects sell tokens to already be present
/// @custom:interaction reentrancy-safe b/c state-locking
// checks:
// state is NOT_STARTED
// req.sellAmount <= our balance of sell tokens < 2**96
// req.minBuyAmount < 2**96
// effects:
// state' is OPEN
// correctly sets all Metadata and Economic parameters of this contract
//
// actions:
// increases the `req.sell` allowance for `gnosis` by the amount needed to fund the auction
// calls gnosis.initiateAuction(...) to launch the requested auction.
function init(
IBroker broker_,
address origin_,
IGnosis gnosis_,
uint48 auctionLength,
TradeRequest calldata req
) external stateTransition(TradeStatus.NOT_STARTED, TradeStatus.OPEN) {
require(req.sellAmount <= type(uint96).max, "sellAmount too large");
require(req.minBuyAmount <= type(uint96).max, "minBuyAmount too large");
sell = req.sell.erc20();
buy = req.buy.erc20();
initBal = sell.balanceOf(address(this));
require(initBal <= type(uint96).max, "initBal too large");
require(initBal >= req.sellAmount, "unfunded trade");
assert(origin_ != address(0));
broker = broker_;
origin = origin_;
gnosis = gnosis_;
endTime = uint48(block.timestamp) + auctionLength;
// {buyTok/sellTok}
worstCasePrice = shiftl_toFix(req.minBuyAmount, -int8(buy.decimals())).div(
shiftl_toFix(req.sellAmount, -int8(sell.decimals()))
);
// Downsize our sell amount to adjust for fee
// {qTok} = {qTok} * {1} / {1}
uint96 sellAmount = uint96(
_divrnd(
req.sellAmount * FEE_DENOMINATOR,
FEE_DENOMINATOR + gnosis.feeNumerator(),
FLOOR
)
);
// Don't decrease minBuyAmount even if fees are in effect. The fee is part of the slippage
uint96 minBuyAmount = uint96(Math.max(1, req.minBuyAmount)); // Safe downcast; require'd
uint256 minBuyAmtPerOrder = Math.max(
minBuyAmount / MAX_ORDERS,
DEFAULT_MIN_BID.shiftl_toUint(int8(buy.decimals()))
);
// Gnosis EasyAuction requires minBuyAmtPerOrder > 0
// untestable:
// Value will always be at least 1. Handled previously in the calling contracts.
Iif (minBuyAmtPerOrder == 0) minBuyAmtPerOrder = 1;
// == Interactions ==
// Set allowance (two safeApprove calls to support USDT)
IERC20Upgradeable(address(sell)).safeApprove(address(gnosis), 0);
IERC20Upgradeable(address(sell)).safeApprove(address(gnosis), initBal);
auctionId = gnosis.initiateAuction(
sell,
buy,
endTime,
endTime,
sellAmount,
minBuyAmount,
minBuyAmtPerOrder,
0,
false,
address(0),
new bytes(0)
);
}
/// Settle trade, transfer tokens to trader, and report bad trade if needed
/// @custom:interaction reentrancy-safe b/c state-locking
// checks:
// state is OPEN
// caller is `origin`
// now >= endTime
// actions:
// (if not already called) call gnosis.settleAuction(auctionID), which:
// settles the Gnosis Auction
// transfers the resulting tokens back to this address
// if the auction's clearing price was below what we assert it should be,
// then broker.reportViolation()
// transfer all balancess of `buy` and `sell` at this address to `origin`
// effects:
// state' is CLOSED
function settle()
external
stateTransition(TradeStatus.OPEN, TradeStatus.CLOSED)
returns (uint256 soldAmt, uint256 boughtAmt)
{
require(msg.sender == origin, "only origin can settle");
// Optionally process settlement of the auction in Gnosis
if (!isAuctionCleared()) {
// By design, we don't rely on this return value at all, just the
// "cleared" state of the auction, and the token balances this contract owns.
// slither-disable-next-line unused-return
gnosis.settleAuction(auctionId);
assert(isAuctionCleared());
}
// At this point we know the auction has cleared
// Transfer balances to origin
uint256 sellBal = sell.balanceOf(address(this));
boughtAmt = buy.balanceOf(address(this));
if (sellBal > 0) IERC20Upgradeable(address(sell)).safeTransfer(origin, sellBal);
if (boughtAmt > 0) IERC20Upgradeable(address(buy)).safeTransfer(origin, boughtAmt);
// Check clearing prices
if (sellBal < initBal) {
soldAmt = initBal - sellBal;
// Gnosis rounds defensively in the buy token; we should not consider it a violation
uint256 adjustedSoldAmt = Math.max(soldAmt, 1);
uint256 adjustedBuyAmt = boughtAmt + 1;
// {buyTok/sellTok}
uint192 clearingPrice = shiftl_toFix(adjustedBuyAmt, -int8(buy.decimals())).div(
shiftl_toFix(adjustedSoldAmt, -int8(sell.decimals()))
);
Iif (clearingPrice.lt(worstCasePrice)) {
broker.reportViolation();
}
}
}
/// Anyone can transfer any ERC20 back to the origin after the trade has been closed
/// @dev Escape hatch in case trading partner freezes up, or other unexpected events
/// @custom:interaction CEI (and respects the state lock)
function transferToOriginAfterTradeComplete(IERC20 erc20) external {
require(status == TradeStatus.CLOSED, "only after trade is closed");
IERC20Upgradeable(address(erc20)).safeTransfer(origin, erc20.balanceOf(address(this)));
}
/// @return True if the trade can be settled.
// Guaranteed to be true some time after init(), until settle() is called
function canSettle() external view returns (bool) {
return status == TradeStatus.OPEN && endTime <= block.timestamp;
}
// === Private ===
function isAuctionCleared() private view returns (bool) {
GnosisAuctionData memory data = gnosis.auctionData(auctionId);
return data.clearingPriceOrder != bytes32(0);
}
}
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