Contract Source Code:

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IRouter {
    function addPlugin(address _plugin) external;
    function pluginTransfer(address _token, address _account, address _receiver, uint256 _amount) external;
    function pluginIncreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external;
    function pluginDecreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external returns (uint256);
    function swap(address[] memory _path, uint256 _amountIn, uint256 _minOut, address _receiver) external;
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IShortsTracker {
    function isGlobalShortDataReady() external view returns (bool);
    function globalShortAveragePrices(address _token) external view returns (uint256);
    function getNextGlobalShortData(
        address _account,
        address _collateralToken,
        address _indexToken,
        uint256 _nextPrice,
        uint256 _sizeDelta,
        bool _isIncrease
    ) external view returns (uint256, uint256);
    function updateGlobalShortData(
        address _account,
        address _collateralToken,
        address _indexToken,
        bool _isLong,
        uint256 _sizeDelta,
        uint256 _markPrice,
        bool _isIncrease
    ) external;
    function setIsGlobalShortDataReady(bool value) external;
    function setInitData(address[] calldata _tokens, uint256[] calldata _averagePrices) external;
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "./IVaultUtils.sol";

interface IVault {
    function isInitialized() external view returns (bool);
    function isSwapEnabled() external view returns (bool);
    function isLeverageEnabled() external view returns (bool);

    function setVaultUtils(IVaultUtils _vaultUtils) external;
    function setError(uint256 _errorCode, string calldata _error) external;

    function router() external view returns (address);
    function usdg() external view returns (address);
    function gov() external view returns (address);

    function whitelistedTokenCount() external view returns (uint256);
    function maxLeverage() external view returns (uint256);

    function minProfitTime() external view returns (uint256);
    function hasDynamicFees() external view returns (bool);
    function fundingInterval() external view returns (uint256);
    function totalTokenWeights() external view returns (uint256);
    function getTargetUsdgAmount(address _token) external view returns (uint256);

    function inManagerMode() external view returns (bool);
    function inPrivateLiquidationMode() external view returns (bool);

    function maxGasPrice() external view returns (uint256);

    function approvedRouters(address _account, address _router) external view returns (bool);
    function isLiquidator(address _account) external view returns (bool);
    function isManager(address _account) external view returns (bool);

    function minProfitBasisPoints(address _token) external view returns (uint256);
    function tokenBalances(address _token) external view returns (uint256);
    function lastFundingTimes(address _token) external view returns (uint256);

    function setMaxLeverage(uint256 _maxLeverage) external;
    function setInManagerMode(bool _inManagerMode) external;
    function setManager(address _manager, bool _isManager) external;
    function setIsSwapEnabled(bool _isSwapEnabled) external;
    function setIsLeverageEnabled(bool _isLeverageEnabled) external;
    function setMaxGasPrice(uint256 _maxGasPrice) external;
    function setUsdgAmount(address _token, uint256 _amount) external;
    function setBufferAmount(address _token, uint256 _amount) external;
    function setMaxGlobalShortSize(address _token, uint256 _amount) external;
    function setInPrivateLiquidationMode(bool _inPrivateLiquidationMode) external;
    function setLiquidator(address _liquidator, bool _isActive) external;

    function setFundingRate(uint256 _fundingInterval, uint256 _fundingRateFactor, uint256 _stableFundingRateFactor) external;

    function setFees(
        uint256 _taxBasisPoints,
        uint256 _stableTaxBasisPoints,
        uint256 _mintBurnFeeBasisPoints,
        uint256 _swapFeeBasisPoints,
        uint256 _stableSwapFeeBasisPoints,
        uint256 _marginFeeBasisPoints,
        uint256 _liquidationFeeUsd,
        uint256 _minProfitTime,
        bool _hasDynamicFees
    ) external;

    function setTokenConfig(
        address _token,
        uint256 _tokenDecimals,
        uint256 _redemptionBps,
        uint256 _minProfitBps,
        uint256 _maxUsdgAmount,
        bool _isStable,
        bool _isShortable
    ) external;

    function setPriceFeed(address _priceFeed) external;
    function withdrawFees(address _token, address _receiver) external returns (uint256);

    function directPoolDeposit(address _token) external;
    function buyUSDG(address _token, address _receiver) external returns (uint256);
    function sellUSDG(address _token, address _receiver) external returns (uint256);
    function swap(address _tokenIn, address _tokenOut, address _receiver) external returns (uint256);
    function increasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external;
    function decreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external returns (uint256);
    function validateLiquidation(address _account, address _collateralToken, address _indexToken, bool _isLong, bool _raise) external view returns (uint256, uint256);
    function liquidatePosition(address _account, address _collateralToken, address _indexToken, bool _isLong, address _feeReceiver) external;
    function tokenToUsdMin(address _token, uint256 _tokenAmount) external view returns (uint256);

    function priceFeed() external view returns (address);
    function fundingRateFactor() external view returns (uint256);
    function stableFundingRateFactor() external view returns (uint256);
    function cumulativeFundingRates(address _token) external view returns (uint256);
    function getNextFundingRate(address _token) external view returns (uint256);
    function getFeeBasisPoints(address _token, uint256 _usdgDelta, uint256 _feeBasisPoints, uint256 _taxBasisPoints, bool _increment) external view returns (uint256);

    function liquidationFeeUsd() external view returns (uint256);
    function taxBasisPoints() external view returns (uint256);
    function stableTaxBasisPoints() external view returns (uint256);
    function mintBurnFeeBasisPoints() external view returns (uint256);
    function swapFeeBasisPoints() external view returns (uint256);
    function stableSwapFeeBasisPoints() external view returns (uint256);
    function marginFeeBasisPoints() external view returns (uint256);

    function allWhitelistedTokensLength() external view returns (uint256);
    function allWhitelistedTokens(uint256) external view returns (address);
    function whitelistedTokens(address _token) external view returns (bool);
    function stableTokens(address _token) external view returns (bool);
    function shortableTokens(address _token) external view returns (bool);
    function feeReserves(address _token) external view returns (uint256);
    function globalShortSizes(address _token) external view returns (uint256);
    function globalShortAveragePrices(address _token) external view returns (uint256);
    function maxGlobalShortSizes(address _token) external view returns (uint256);
    function tokenDecimals(address _token) external view returns (uint256);
    function tokenWeights(address _token) external view returns (uint256);
    function guaranteedUsd(address _token) external view returns (uint256);
    function poolAmounts(address _token) external view returns (uint256);
    function bufferAmounts(address _token) external view returns (uint256);
    function reservedAmounts(address _token) external view returns (uint256);
    function usdgAmounts(address _token) external view returns (uint256);
    function maxUsdgAmounts(address _token) external view returns (uint256);
    function getRedemptionAmount(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getMaxPrice(address _token) external view returns (uint256);
    function getMinPrice(address _token) external view returns (uint256);

    function getDelta(address _indexToken, uint256 _size, uint256 _averagePrice, bool _isLong, uint256 _lastIncreasedTime) external view returns (bool, uint256);
    function getPosition(address _account, address _collateralToken, address _indexToken, bool _isLong) external view returns (uint256, uint256, uint256, uint256, uint256, uint256, bool, uint256);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface IVaultUtils {
    function updateCumulativeFundingRate(address _collateralToken, address _indexToken) external returns (bool);
    function validateIncreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _sizeDelta, bool _isLong) external view;
    function validateDecreasePosition(address _account, address _collateralToken, address _indexToken, uint256 _collateralDelta, uint256 _sizeDelta, bool _isLong, address _receiver) external view;
    function validateLiquidation(address _account, address _collateralToken, address _indexToken, bool _isLong, bool _raise) external view returns (uint256, uint256);
    function getEntryFundingRate(address _collateralToken, address _indexToken, bool _isLong) external view returns (uint256);
    function getPositionFee(address _account, address _collateralToken, address _indexToken, bool _isLong, uint256 _sizeDelta) external view returns (uint256);
    function getFundingFee(address _account, address _collateralToken, address _indexToken, bool _isLong, uint256 _size, uint256 _entryFundingRate) external view returns (uint256);
    function getBuyUsdgFeeBasisPoints(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getSellUsdgFeeBasisPoints(address _token, uint256 _usdgAmount) external view returns (uint256);
    function getSwapFeeBasisPoints(address _tokenIn, address _tokenOut, uint256 _usdgAmount) external view returns (uint256);
    function getFeeBasisPoints(address _token, uint256 _usdgDelta, uint256 _feeBasisPoints, uint256 _taxBasisPoints, bool _increment) external view returns (uint256);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

import "../libraries/math/SafeMath.sol";
import "../peripherals/interfaces/ITimelock.sol";

import "./interfaces/IVault.sol";
import "./interfaces/IRouter.sol";
import "./interfaces/IShortsTracker.sol";

library PositionUtils {
    using SafeMath for uint256;

    uint256 public constant BASIS_POINTS_DIVISOR = 10000;

    event LeverageDecreased(uint256 collateralDelta, uint256 prevLeverage, uint256 nextLeverage);

    function shouldDeductFee(
        address _vault,
        address _account,
        address[] memory _path,
        uint256 _amountIn,
        address _indexToken,
        bool _isLong,
        uint256 _sizeDelta,
        uint256 _increasePositionBufferBps
    ) external returns (bool) {
        // if the position is a short, do not charge a fee
        if (!_isLong) { return false; }

        // if the position size is not increasing, this is a collateral deposit
        if (_sizeDelta == 0) { return true; }

        address collateralToken = _path[_path.length - 1];

        IVault vault = IVault(_vault);
        (uint256 size, uint256 collateral, , , , , , ) = vault.getPosition(_account, collateralToken, _indexToken, _isLong);

        // if there is no existing position, do not charge a fee
        if (size == 0) { return false; }

        uint256 nextSize = size.add(_sizeDelta);
        uint256 collateralDelta = vault.tokenToUsdMin(collateralToken, _amountIn);
        uint256 nextCollateral = collateral.add(collateralDelta);

        uint256 prevLeverage = size.mul(BASIS_POINTS_DIVISOR).div(collateral);
        // allow for a maximum of a increasePositionBufferBps decrease since there might be some swap fees taken from the collateral
        uint256 nextLeverage = nextSize.mul(BASIS_POINTS_DIVISOR + _increasePositionBufferBps).div(nextCollateral);

        emit LeverageDecreased(collateralDelta, prevLeverage, nextLeverage);

        // deduct a fee if the leverage is decreased
        return nextLeverage < prevLeverage;
    }

    function increasePosition(
        address _vault,
        address _router,
        address _shortsTracker,
        address _account,
        address _collateralToken,
        address _indexToken,
        uint256 _sizeDelta,
        bool _isLong,
        uint256 _price
    ) external {
        uint256 markPrice = _isLong ? IVault(_vault).getMaxPrice(_indexToken) : IVault(_vault).getMinPrice(_indexToken);
        if (_isLong) {
            require(markPrice <= _price, "markPrice > price");
        } else {
            require(markPrice >= _price, "markPrice < price");
        }

        address timelock = IVault(_vault).gov();

        // should be called strictly before position is updated in Vault
        IShortsTracker(_shortsTracker).updateGlobalShortData(_account, _collateralToken, _indexToken, _isLong, _sizeDelta, markPrice, true);

        ITimelock(timelock).enableLeverage(_vault);
        IRouter(_router).pluginIncreasePosition(_account, _collateralToken, _indexToken, _sizeDelta, _isLong);
        ITimelock(timelock).disableLeverage(_vault);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

interface ITimelock {
    function marginFeeBasisPoints() external returns (uint256);
    function setAdmin(address _admin) external;
    function enableLeverage(address _vault) external;
    function disableLeverage(address _vault) external;
    function setIsLeverageEnabled(address _vault, bool _isLeverageEnabled) external;
    function signalSetGov(address _target, address _gov) external;
}