// File: contracts/SortedTroves.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "./Interfaces/ISortedTroves.sol";
import "./Interfaces/ITroveManager.sol";
import "./Interfaces/IBorrowerOperations.sol";
import "./Dependencies/SafeMath.sol";
import "./Dependencies/Ownable.sol";
import "./Dependencies/CheckContract.sol";


/*
 * A sorted doubly linked list with nodes sorted in descending order.
 *
 * Nodes map to active Troves in the system - the ID property is the address of a Trove owner.
 * Nodes are ordered according to their current nominal individual collateral ratio (NICR),
 * which is like the ICR but without the price, i.e., just collateral / debt.
 *
 * The list optionally accepts insert position hints.
 *
 * NICRs are computed dynamically at runtime, and not stored on the Node. This is because NICRs of active Troves
 * change dynamically as liquidation events occur.
 *
 * The list relies on the fact that liquidation events preserve ordering: a liquidation decreases the NICRs of all active Troves,
 * but maintains their order. A node inserted based on current NICR will maintain the correct position,
 * relative to it's peers, as rewards accumulate, as long as it's raw collateral and debt have not changed.
 * Thus, Nodes remain sorted by current NICR.
 *
 * Nodes need only be re-inserted upon a Trove operation - when the owner adds or removes collateral or debt
 * to their position.
 *
 * The list is a modification of the following audited SortedDoublyLinkedList:
 * https://github.com/livepeer/protocol/blob/master/contracts/libraries/SortedDoublyLL.sol
 *
 *
 * Changes made in the Liquity implementation:
 *
 * - Keys have been removed from nodes
 *
 * - Ordering checks for insertion are performed by comparing an NICR argument to the current NICR, calculated at runtime.
 *   The list relies on the property that ordering by ICR is maintained as the ETH:USD price varies.
 *
 * - Public functions with parameters have been made internal to save gas, and given an external wrapper function for external access
 */
contract SortedTroves is Ownable, CheckContract, ISortedTroves {
    using SafeMath for uint256;

    string public constant NAME = "SortedTroves";

    address public borrowerOperationsAddress;

    ITroveManager public troveManager;

    // Information for a node in the list
    struct Node {
        bool exists;
        address nextId; // Id of next node (smaller NICR) in the list
        address prevId; // Id of previous node (larger NICR) in the list
    }

    // Information for the list
    struct Data {
        address head; // Head of the list. Also the node in the list with the largest NICR
        address tail; // Tail of the list. Also the node in the list with the smallest NICR
        uint256 maxSize; // Maximum size of the list
        uint256 size; // Current size of the list
        mapping(address => Node) nodes; // Track the corresponding ids for each node in the list
    }

    Data public data;

    // --- Dependency setters ---

    function setParams(
        uint256 _size,
        address _troveManagerAddress,
        address _borrowerOperationsAddress
    ) external override onlyOwner {
        require(_size > 0, "SortedTroves: Size can't be zero");
        checkContract(_troveManagerAddress);
        checkContract(_borrowerOperationsAddress);

        data.maxSize = _size;

        troveManager = ITroveManager(_troveManagerAddress);
        borrowerOperationsAddress = _borrowerOperationsAddress;

        emit TroveManagerAddressChanged(_troveManagerAddress);
        emit BorrowerOperationsAddressChanged(_borrowerOperationsAddress);

        _renounceOwnership();
    }

    /*
     * @dev Add a node to the list
     * @param _id Node's id
     * @param _NICR Node's NICR
     * @param _prevId Id of previous node for the insert position
     * @param _nextId Id of next node for the insert position
     */

    function insert(
        address _id,
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) external override {
        ITroveManager troveManagerCached = troveManager;

        _requireCallerIsBOorTroveM(troveManagerCached);
        _insert(troveManagerCached, _id, _NICR, _prevId, _nextId);
    }

    function _insert(
        ITroveManager _troveManager,
        address _id,
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) internal {
        // List must not be full
        require(!isFull(), "SortedTroves: List is full");
        // List must not already contain node
        require(!contains(_id), "SortedTroves: List already contains the node");
        // Node id must not be null
        require(_id != address(0), "SortedTroves: Id cannot be zero");
        // NICR must be non-zero
        require(_NICR > 0, "SortedTroves: NICR must be positive");

        address prevId = _prevId;
        address nextId = _nextId;

        if (!_validInsertPosition(_troveManager, _NICR, prevId, nextId)) {
            // Sender's hint was not a valid insert position
            // Use sender's hint to find a valid insert position
            (prevId, nextId) = _findInsertPosition(_troveManager, _NICR, prevId, nextId);
        }

        data.nodes[_id].exists = true;

        if (prevId == address(0) && nextId == address(0)) {
            // Insert as head and tail
            data.head = _id;
            data.tail = _id;
        } else if (prevId == address(0)) {
            // Insert before `prevId` as the head
            data.nodes[_id].nextId = data.head;
            data.nodes[data.head].prevId = _id;
            data.head = _id;
        } else if (nextId == address(0)) {
            // Insert after `nextId` as the tail
            data.nodes[_id].prevId = data.tail;
            data.nodes[data.tail].nextId = _id;
            data.tail = _id;
        } else {
            // Insert at insert position between `prevId` and `nextId`
            data.nodes[_id].nextId = nextId;
            data.nodes[_id].prevId = prevId;
            data.nodes[prevId].nextId = _id;
            data.nodes[nextId].prevId = _id;
        }

        data.size = data.size.add(1);
        emit NodeAdded(_id, _NICR);
    }

    function remove(address _id) external override {
        _requireCallerIsTroveManager();
        _remove(_id);
    }

    /*
     * @dev Remove a node from the list
     * @param _id Node's id
     */
    function _remove(address _id) internal {
        // List must contain the node
        require(contains(_id), "SortedTroves: List does not contain the id");

        if (data.size > 1) {
            // List contains more than a single node
            if (_id == data.head) {
                // The removed node is the head
                // Set head to next node
                data.head = data.nodes[_id].nextId;
                // Set prev pointer of new head to null
                data.nodes[data.head].prevId = address(0);
            } else if (_id == data.tail) {
                // The removed node is the tail
                // Set tail to previous node
                data.tail = data.nodes[_id].prevId;
                // Set next pointer of new tail to null
                data.nodes[data.tail].nextId = address(0);
            } else {
                // The removed node is neither the head nor the tail
                // Set next pointer of previous node to the next node
                data.nodes[data.nodes[_id].prevId].nextId = data.nodes[_id].nextId;
                // Set prev pointer of next node to the previous node
                data.nodes[data.nodes[_id].nextId].prevId = data.nodes[_id].prevId;
            }
        } else {
            // List contains a single node
            // Set the head and tail to null
            data.head = address(0);
            data.tail = address(0);
        }

        delete data.nodes[_id];
        data.size = data.size.sub(1);
        NodeRemoved(_id);
    }

    /*
     * @dev Re-insert the node at a new position, based on its new NICR
     * @param _id Node's id
     * @param _newNICR Node's new NICR
     * @param _prevId Id of previous node for the new insert position
     * @param _nextId Id of next node for the new insert position
     */
    function reInsert(
        address _id,
        uint256 _newNICR,
        address _prevId,
        address _nextId
    ) external override {
        ITroveManager troveManagerCached = troveManager;

        _requireCallerIsBOorTroveM(troveManagerCached);
        // List must contain the node
        require(contains(_id), "SortedTroves: List does not contain the id");
        // NICR must be non-zero
        require(_newNICR > 0, "SortedTroves: NICR must be positive");

        // Remove node from the list
        _remove(_id);

        _insert(troveManagerCached, _id, _newNICR, _prevId, _nextId);
    }

    /*
     * @dev Checks if the list contains a node
     */
    function contains(address _id) public view override returns (bool) {
        return data.nodes[_id].exists;
    }

    /*
     * @dev Checks if the list is full
     */
    function isFull() public view override returns (bool) {
        return data.size == data.maxSize;
    }

    /*
     * @dev Checks if the list is empty
     */
    function isEmpty() public view override returns (bool) {
        return data.size == 0;
    }

    /*
     * @dev Returns the current size of the list
     */
    function getSize() external view override returns (uint256) {
        return data.size;
    }

    /*
     * @dev Returns the maximum size of the list
     */
    function getMaxSize() external view override returns (uint256) {
        return data.maxSize;
    }

    /*
     * @dev Returns the first node in the list (node with the largest NICR)
     */
    function getFirst() external view override returns (address) {
        return data.head;
    }

    /*
     * @dev Returns the last node in the list (node with the smallest NICR)
     */
    function getLast() external view override returns (address) {
        return data.tail;
    }

    /*
     * @dev Returns the next node (with a smaller NICR) in the list for a given node
     * @param _id Node's id
     */
    function getNext(address _id) external view override returns (address) {
        return data.nodes[_id].nextId;
    }

    /*
     * @dev Returns the previous node (with a larger NICR) in the list for a given node
     * @param _id Node's id
     */
    function getPrev(address _id) external view override returns (address) {
        return data.nodes[_id].prevId;
    }

    /*
     * @dev Check if a pair of nodes is a valid insertion point for a new node with the given NICR
     * @param _NICR Node's NICR
     * @param _prevId Id of previous node for the insert position
     * @param _nextId Id of next node for the insert position
     */
    function validInsertPosition(
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) external view override returns (bool) {
        return _validInsertPosition(troveManager, _NICR, _prevId, _nextId);
    }

    function _validInsertPosition(
        ITroveManager _troveManager,
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) internal view returns (bool) {
        if (_prevId == address(0) && _nextId == address(0)) {
            // `(null, null)` is a valid insert position if the list is empty
            return isEmpty();
        } else if (_prevId == address(0)) {
            // `(null, _nextId)` is a valid insert position if `_nextId` is the head of the list
            return data.head == _nextId && _NICR >= _troveManager.getNominalICR(_nextId);
        } else if (_nextId == address(0)) {
            // `(_prevId, null)` is a valid insert position if `_prevId` is the tail of the list
            return data.tail == _prevId && _NICR <= _troveManager.getNominalICR(_prevId);
        } else {
            // `(_prevId, _nextId)` is a valid insert position if they are adjacent nodes and `_NICR` falls between the two nodes' NICRs
            return
                data.nodes[_prevId].nextId == _nextId &&
                _troveManager.getNominalICR(_prevId) >= _NICR &&
                _NICR >= _troveManager.getNominalICR(_nextId);
        }
    }

    /*
     * @dev Descend the list (larger NICRs to smaller NICRs) to find a valid insert position
     * @param _troveManager TroveManager contract, passed in as param to save SLOAD’s
     * @param _NICR Node's NICR
     * @param _startId Id of node to start descending the list from
     */
    function _descendList(
        ITroveManager _troveManager,
        uint256 _NICR,
        address _startId
    ) internal view returns (address, address) {
        // If `_startId` is the head, check if the insert position is before the head
        if (data.head == _startId && _NICR >= _troveManager.getNominalICR(_startId)) {
            return (address(0), _startId);
        }

        address prevId = _startId;
        address nextId = data.nodes[prevId].nextId;

        // Descend the list until we reach the end or until we find a valid insert position
        while (prevId != address(0) && !_validInsertPosition(_troveManager, _NICR, prevId, nextId)) {
            prevId = data.nodes[prevId].nextId;
            nextId = data.nodes[prevId].nextId;
        }

        return (prevId, nextId);
    }

    /*
     * @dev Ascend the list (smaller NICRs to larger NICRs) to find a valid insert position
     * @param _troveManager TroveManager contract, passed in as param to save SLOAD’s
     * @param _NICR Node's NICR
     * @param _startId Id of node to start ascending the list from
     */
    function _ascendList(
        ITroveManager _troveManager,
        uint256 _NICR,
        address _startId
    ) internal view returns (address, address) {
        // If `_startId` is the tail, check if the insert position is after the tail
        if (data.tail == _startId && _NICR <= _troveManager.getNominalICR(_startId)) {
            return (_startId, address(0));
        }

        address nextId = _startId;
        address prevId = data.nodes[nextId].prevId;

        // Ascend the list until we reach the end or until we find a valid insertion point
        while (nextId != address(0) && !_validInsertPosition(_troveManager, _NICR, prevId, nextId)) {
            nextId = data.nodes[nextId].prevId;
            prevId = data.nodes[nextId].prevId;
        }

        return (prevId, nextId);
    }

    /*
     * @dev Find the insert position for a new node with the given NICR
     * @param _NICR Node's NICR
     * @param _prevId Id of previous node for the insert position
     * @param _nextId Id of next node for the insert position
     */
    function findInsertPosition(
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) external view override returns (address, address) {
        return _findInsertPosition(troveManager, _NICR, _prevId, _nextId);
    }

    function _findInsertPosition(
        ITroveManager _troveManager,
        uint256 _NICR,
        address _prevId,
        address _nextId
    ) internal view returns (address, address) {
        address prevId = _prevId;
        address nextId = _nextId;

        if (prevId != address(0)) {
            if (!contains(prevId) || _NICR > _troveManager.getNominalICR(prevId)) {
                // `prevId` does not exist anymore or now has a smaller NICR than the given NICR
                prevId = address(0);
            }
        }

        if (nextId != address(0)) {
            if (!contains(nextId) || _NICR < _troveManager.getNominalICR(nextId)) {
                // `nextId` does not exist anymore or now has a larger NICR than the given NICR
                nextId = address(0);
            }
        }

        if (prevId == address(0) && nextId == address(0)) {
            // No hint - descend list starting from head
            return _descendList(_troveManager, _NICR, data.head);
        } else if (prevId == address(0)) {
            // No `prevId` for hint - ascend list starting from `nextId`
            return _ascendList(_troveManager, _NICR, nextId);
        } else if (nextId == address(0)) {
            // No `nextId` for hint - descend list starting from `prevId`
            return _descendList(_troveManager, _NICR, prevId);
        } else {
            // Descend list starting from `prevId`
            return _descendList(_troveManager, _NICR, prevId);
        }
    }

    // --- 'require' functions ---

    function _requireCallerIsTroveManager() internal view {
        require(msg.sender == address(troveManager), "SortedTroves: Caller is not the TroveManager");
    }

    function _requireCallerIsBOorTroveM(ITroveManager _troveManager) internal view {
        require(
            msg.sender == borrowerOperationsAddress || msg.sender == address(_troveManager),
            "SortedTroves: Caller is neither BO nor TroveM"
        );
    }
}

// File: contracts/Interfaces/ISortedTroves.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

// Common interface for the SortedTroves Doubly Linked List.
interface ISortedTroves {
    // --- Events ---

    event TroveManagerAddressChanged(address _troveManagerAddress);
    event BorrowerOperationsAddressChanged(address _borrowerOperationsAddress);
    event NodeAdded(address _id, uint256 _NICR);
    event NodeRemoved(address _id);
    event NodeOwnerUpdated(address id, address newId, uint256 timestamp);

    // --- Functions ---

    function setParams(
        uint256 _size,
        address _TroveManagerAddress,
        address _borrowerOperationsAddress
    ) external;

    function insert(
        address _id,
        uint256 _ICR,
        address _prevId,
        address _nextId
    ) external;

    function remove(address _id) external;

    function reInsert(
        address _id,
        uint256 _newICR,
        address _prevId,
        address _nextId
    ) external;

    function contains(address _id) external view returns (bool);

    function isFull() external view returns (bool);

    function isEmpty() external view returns (bool);

    function getSize() external view returns (uint256);

    function getMaxSize() external view returns (uint256);

    function getFirst() external view returns (address);

    function getLast() external view returns (address);

    function getNext(address _id) external view returns (address);

    function getPrev(address _id) external view returns (address);

    function validInsertPosition(
        uint256 _ICR,
        address _prevId,
        address _nextId
    ) external view returns (bool);

    function findInsertPosition(
        uint256 _ICR,
        address _prevId,
        address _nextId
    ) external view returns (address, address);
}

// File: contracts/Interfaces/ITroveManager.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "./IStabilityPool.sol";
import "./ILiquityBase.sol";
import "../Interfaces/ILiquityLUSDToken.sol";

// Common interface for the Trove Manager.
interface ITroveManager is ILiquityBase {


    event BorrowerOperationsAddressChanged(address _newBorrowerOperationsAddress);
    event LUSDTokenAddressChanged(address _newLUSDTokenAddress);
    event ActivePoolAddressChanged(address _activePoolAddress);
    event DefaultPoolAddressChanged(address _defaultPoolAddress);
    event StabilityPoolAddressChanged(address _stabilityPoolAddress);
    event GasPoolAddressChanged(address _gasPoolAddress);
    event CollSurplusPoolAddressChanged(address _collSurplusPoolAddress);
    event SortedTrovesAddressChanged(address _sortedTrovesAddress);
    event GovernanceAddressChanged(address _governanceAddress);
    event WETHAddressChanged(address _wethAddress);

    event RewardSnapshotDetailsUpdated(address owner, address newOwner, uint256 timestamp);
    event TroveOwnersUpdated(address owner, address newOwner, uint256 idx, uint256 timestamp);
    event Liquidation(
        uint256 _liquidatedDebt,
        uint256 _liquidatedColl,
        uint256 _collGasCompensation,
        uint256 _LUSDGasCompensation
    );
    event Redemption(
        uint256 _attemptedLUSDAmount,
        uint256 _actualLUSDAmount,
        uint256 _ETHSent,
        uint256 _ETHFee
    );
    event TroveUpdated(
        address indexed _borrower,
        uint256 _debt,
        uint256 _coll,
        uint256 _stake,
        TroveManagerOperation _operation
    );
    event TroveLiquidated(
        address indexed _borrower,
        uint256 _debt,
        uint256 _coll,
        TroveManagerOperation _operation
    );
    event BaseRateUpdated(uint256 _baseRate);
    event LastFeeOpTimeUpdated(uint256 _lastFeeOpTime);
    event TotalStakesUpdated(uint256 _newTotalStakes);
    event SystemSnapshotsUpdated(uint256 _totalStakesSnapshot, uint256 _totalCollateralSnapshot);
    event LTermsUpdated(uint256 _L_ETH, uint256 _L_LUSDDebt);
    event TroveSnapshotsUpdated(uint256 _L_ETH, uint256 _L_LUSDDebt);
    event TroveIndexUpdated(address _borrower, uint256 _newIndex);

    enum TroveManagerOperation {
        applyPendingRewards,
        liquidateInNormalMode,
        liquidateInRecoveryMode,
        redeemCollateral
    }

    // --- Functions ---

    function setAddresses(
        address _borrowerOperationsAddress,
        address _activePoolAddress,
        address _defaultPoolAddress,
        address _stabilityPoolAddress,
        address _gasPoolAddress,
        address _collSurplusPoolAddress,
        address _lusdTokenAddress,
        address _sortedTrovesAddress,
        address _governanceAddress,
        address _wethAddress
    ) external;

    function stabilityPool() external view returns (IStabilityPool);

    function lusdToken() external view returns (ILiquityLUSDToken);

    function getTroveOwnersCount() external view returns (uint256);

    function getTroveFromTroveOwnersArray(uint256 _index) external view returns (address);

    function getNominalICR(address _borrower) external view returns (uint256);

    function getCurrentICR(address _borrower, uint256 _price) external view returns (uint256);

    function liquidate(address _borrower) external;

    function liquidateTroves(uint256 _n) external;

    function batchLiquidateTroves(address[] calldata _troveArray) external;

    function redeemCollateral(
        uint256 _LUSDAmount,
        address _firstRedemptionHint,
        address _upperPartialRedemptionHint,
        address _lowerPartialRedemptionHint,
        uint256 _partialRedemptionHintNICR,
        uint256 _maxIterations,
        uint256 _maxFee
    ) external;

    function updateStakeAndTotalStakes(address _borrower) external returns (uint256);

    function updateTroveRewardSnapshots(address _borrower) external;

    function addTroveOwnerToArray(address _borrower) external returns (uint256 index);

    function applyPendingRewards(address _borrower) external;

    function getPendingETHReward(address _borrower) external view returns (uint256);

    function getPendingLUSDDebtReward(address _borrower) external view returns (uint256);

    function hasPendingRewards(address _borrower) external view returns (bool);

    function getEntireDebtAndColl(address _borrower)
        external
        view
        returns (
            uint256 debt,
            uint256 coll,
            uint256 pendingLUSDDebtReward,
            uint256 pendingETHReward
        );

    function closeTrove(address _borrower) external;

    function removeStake(address _borrower) external;

    function getRedemptionRate() external view returns (uint256);

    function getRedemptionRateWithDecay() external view returns (uint256);

    function getRedemptionFeeWithDecay(uint256 _ETHDrawn) external view returns (uint256);

    function getBorrowingRate() external view returns (uint256);

    function getBorrowingRateWithDecay() external view returns (uint256);

    function getBorrowingFee(uint256 LUSDDebt) external view returns (uint256);

    function getBorrowingFeeWithDecay(uint256 _LUSDDebt) external view returns (uint256);

    function decayBaseRateFromBorrowing() external;

    function getTroveStatus(address _borrower) external view returns (uint256);

    function getTroveStake(address _borrower) external view returns (uint256);

    function getTroveDebt(address _borrower) external view returns (uint256);

    function getTroveFrontEnd(address _borrower) external view returns (address);

    function getTroveColl(address _borrower) external view returns (uint256);

    function setTroveStatus(address _borrower, uint256 num) external;

    function setTroveFrontEndTag(address _borrower, address _frontEndTag) external;

    function increaseTroveColl(address _borrower, uint256 _collIncrease) external returns (uint256);

    function decreaseTroveColl(address _borrower, uint256 _collDecrease) external returns (uint256);

    function increaseTroveDebt(address _borrower, uint256 _debtIncrease) external returns (uint256);

    function decreaseTroveDebt(address _borrower, uint256 _collDecrease) external returns (uint256);

    function getTCR(uint256 _price) external view returns (uint256);

    function checkRecoveryMode(uint256 _price) external view returns (bool);
}

// File: contracts/Interfaces/IBorrowerOperations.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

// Common interface for the Trove Manager.
interface IBorrowerOperations {
    enum BorrowerOperation {
        openTrove,
        closeTrove,
        adjustTrove
    }
    // --- Events ---

    event FrontEndRegistered(address indexed _frontEnd, uint256 timestamp);
    event TroveManagerAddressChanged(address _newTroveManagerAddress);
    event ActivePoolAddressChanged(address _activePoolAddress);
    event GovernanceAddressChanged(address _governanceAddress);
    event DefaultPoolAddressChanged(address _defaultPoolAddress);
    event StabilityPoolAddressChanged(address _stabilityPoolAddress);
    event GasPoolAddressChanged(address _gasPoolAddress);
    event CollSurplusPoolAddressChanged(address _collSurplusPoolAddress);
    event SortedTrovesAddressChanged(address _sortedTrovesAddress);
    event LUSDTokenAddressChanged(address _lusdTokenAddress);

    event TroveCreated(address indexed _borrower, uint256 arrayIndex);
    event TroveUpdated(
        address indexed _borrower,
        uint256 _debt,
        uint256 _coll,
        uint256 stake,
        BorrowerOperation operation
    );
    event LUSDBorrowingFeePaid(address indexed _borrower, uint256 _LUSDFee);


    // --- Functions ---

    function setAddresses(
        address _troveManagerAddress,
        address _activePoolAddress,
        address _defaultPoolAddress,
        address _stabilityPoolAddress,
        address _gasPoolAddress,
        address _collSurplusPoolAddress,
        address _sortedTrovesAddress,
        address _lusdTokenAddress,
        address _wethAddress,
        address _governanceAddress
    ) external;

    function registerFrontEnd() external;

    function openTrove(
        uint256 _maxFee,
        uint256 _LUSDAmount,
        uint256 _ETHAmount,
        address _upperHint,
        address _lowerHint,
        address _frontEndTag
    ) external;

    function addColl(
        uint256 _ETHAmount,
        address _upperHint,
        address _lowerHint
    ) external;

    function moveETHGainToTrove(
        uint256 _ETHAmount,
        address _user,
        address _upperHint,
        address _lowerHint
    ) external;

    function withdrawColl(
        uint256 _amount,
        address _upperHint,
        address _lowerHint
    ) external;

    function withdrawLUSD(
        uint256 _maxFee,
        uint256 _amount,
        address _upperHint,
        address _lowerHint
    ) external;

    function repayLUSD(
        uint256 _amount,
        address _upperHint,
        address _lowerHint
    ) external;

    function closeTrove() external;

    function adjustTrove(
        uint256 _maxFee,
        uint256 _collWithdrawal,
        uint256 _debtChange,
        uint256 _ETHAmount,
        bool isDebtIncrease,
        address _upperHint,
        address _lowerHint
    ) external;

    function claimCollateral() external;

    function getCompositeDebt(uint256 _debt) external view returns (uint256);
}

// File: contracts/Dependencies/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * Based on OpenZeppelin's SafeMath:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/math/SafeMath.sol
 *
 * @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.
     *
     * _Available since v2.4.0._
     */
    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.
     *
     * _Available since v2.4.0._
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        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.
     *
     * _Available since v2.4.0._
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// File: contracts/Dependencies/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "./Context.sol";
// MOdificaitons taken from: `https://github.com/FraxFinance/frax-solidity/blob/master/src/hardhat/contracts/Common/Ownable.sol`
/**
 * Based on OpenZeppelin's Ownable contract:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol
 *
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address internal _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     *
     * NOTE: This function is not safe, as it doesn't check owner is calling it.
     * Make sure you check it before calling it.
     */
    function _renounceOwnership() internal {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
}

// File: contracts/Dependencies/CheckContract.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

contract CheckContract {
    /**
     * Check that the account is an already deployed non-destroyed contract.
     * See: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol#L12
     */
    function checkContract(address _account) internal view {
        require(_account != address(0), "Account cannot be zero address");

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(_account)
        }
        require(size > 0, "Account code size cannot be zero");
    }
}

// File: contracts/Interfaces/IStabilityPool.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/*
 * The Stability Pool holds LUSD tokens deposited by Stability Pool depositors.
 *
 * When a trove is liquidated, then depending on system conditions, some of its LUSD debt gets offset with
 * LUSD in the Stability Pool:  that is, the offset debt evaporates, and an equal amount of LUSD tokens in the Stability Pool is burned.
 *
 * Thus, a liquidation causes each depositor to receive a LUSD loss, in proportion to their deposit as a share of total deposits.
 * They also receive an ETH gain, as the ETH collateral of the liquidated trove is distributed among Stability depositors,
 * in the same proportion.
 *
 * When a liquidation occurs, it depletes every deposit by the same fraction: for example, a liquidation that depletes 40%
 * of the total LUSD in the Stability Pool, depletes 40% of each deposit.
 *
 * A deposit that has experienced a series of liquidations is termed a "compounded deposit": each liquidation depletes the deposit,
 * multiplying it by some factor in range ]0,1[
 *
 * Please see the implementation spec in the proof document, which closely follows on from the compounded deposit / ETH gain derivations:
 * https://github.com/liquity/liquity/blob/master/papers/Scalable_Reward_Distribution_with_Compounding_Stakes.pdf
 *
 * --- LQTY ISSUANCE TO STABILITY POOL DEPOSITORS ---
 *
 * An LQTY issuance event occurs at every deposit operation, and every liquidation.
 *
 * Each deposit is tagged with the address of the front end through which it was made.
 *
 * All deposits earn a share of the issued LQTY in proportion to the deposit as a share of total deposits. The LQTY earned
 * by a given deposit, is split between the depositor and the front end through which the deposit was made, based on the front end's kickbackRate.
 *
 * Please see the system Readme for an overview:
 * https://github.com/liquity/dev/blob/main/README.md#lqty-issuance-to-stability-providers
 */
interface IStabilityPool {
    // --- Events ---

    event StabilityPoolETHBalanceUpdated(uint256 _newBalance);
    event StabilityPoolLUSDBalanceUpdated(uint256 _newBalance);
    event BorrowerOperationsAddressChanged(address _newBorrowerOperationsAddress);
    event TroveManagerAddressChanged(address _newTroveManagerAddress);
    event ActivePoolAddressChanged(address _newActivePoolAddress);
    event DefaultPoolAddressChanged(address _newDefaultPoolAddress);
    event LUSDTokenAddressChanged(address _newLUSDTokenAddress);
    event SortedTrovesAddressChanged(address _newSortedTrovesAddress);
    event CommunityIssuanceAddressChanged(address _newCommunityIssuanceAddress);

    event P_Updated(uint256 _P);
    event S_Updated(uint256 _S, uint128 _epoch, uint128 _scale);
    event G_Updated(uint256 _G, uint128 _epoch, uint128 _scale);
    event EpochUpdated(uint128 _currentEpoch);
    event ScaleUpdated(uint128 _currentScale);

    event FrontEndRegistered(address indexed _frontEnd, uint256 _kickbackRate);
    event FrontEndTagSet(address indexed _depositor, address indexed _frontEnd);

    event DepositSnapshotUpdated(address indexed _depositor, uint256 _P, uint256 _S, uint256 _G);
    event FrontEndSnapshotUpdated(address indexed _frontEnd, uint256 _P, uint256 _G);
    event UserDepositChanged(address indexed _depositor, uint256 _newDeposit);
    event FrontEndStakeChanged(
        address indexed _frontEnd,
        uint256 _newFrontEndStake,
        address _depositor
    );

    event ETHGainWithdrawn(address indexed _depositor, uint256 _ETH, uint256 _LUSDLoss);
    event LQTYPaidToDepositor(address indexed _depositor, uint256 _LQTY);
    event LQTYPaidToFrontEnd(address indexed _frontEnd, uint256 _LQTY);
    event EtherSent(address _to, uint256 _amount);
    event GovernanceAddressChanged(address _governanceAddress);

    // --- Functions ---

    /*
     * Called only once on init, to set addresses of other Liquity contracts
     * Callable only by owner, renounces ownership at the end
     */
    function setAddresses(
        address _borrowerOperationsAddress,
        address _troveManagerAddress,
        address _activePoolAddress,
        address _lusdTokenAddress,
        address _sortedTrovesAddress,
        address _wethAddress,
        address _governanceAddress
    ) external;

    /*
     * Initial checks:
     * - Frontend is registered or zero address
     * - Sender is not a registered frontend
     * - _amount is not zero
     * ---
     * - Triggers a LQTY issuance, based on time passed since the last issuance. The LQTY issuance is shared between *all* depositors and front ends
     * - Tags the deposit with the provided front end tag param, if it's a new deposit
     * - Sends depositor's accumulated gains (LQTY, ETH) to depositor
     * - Sends the tagged front end's accumulated LQTY gains to the tagged front end
     * - Increases deposit and tagged front end's stake, and takes new snapshots for each.
     */
    function provideToSP(uint256 _amount, address _frontEndTag) external;

    /*
     * Initial checks:
     * - _amount is zero or there are no under collateralized troves left in the system
     * - User has a non zero deposit
     * ---
     * - Triggers a LQTY issuance, based on time passed since the last issuance. The LQTY issuance is shared between *all* depositors and front ends
     * - Removes the deposit's front end tag if it is a full withdrawal
     * - Sends all depositor's accumulated gains (LQTY, ETH) to depositor
     * - Sends the tagged front end's accumulated LQTY gains to the tagged front end
     * - Decreases deposit and tagged front end's stake, and takes new snapshots for each.
     *
     * If _amount > userDeposit, the user withdraws all of their compounded deposit.
     */
    function withdrawFromSP(uint256 _amount) external;

    /*
     * Initial checks:
     * - User has a non zero deposit
     * - User has an open trove
     * - User has some ETH gain
     * ---
     * - Triggers a LQTY issuance, based on time passed since the last issuance. The LQTY issuance is shared between *all* depositors and front ends
     * - Sends all depositor's LQTY gain to  depositor
     * - Sends all tagged front end's LQTY gain to the tagged front end
     * - Transfers the depositor's entire ETH gain from the Stability Pool to the caller's trove
     * - Leaves their compounded deposit in the Stability Pool
     * - Updates snapshots for deposit and tagged front end stake
     */
    function withdrawETHGainToTrove(address _upperHint, address _lowerHint) external;

    /*
     * Initial checks:
     * - Frontend (sender) not already registered
     * - User (sender) has no deposit
     * - _kickbackRate is in the range [0, 100%]
     * ---
     * Front end makes a one-time selection of kickback rate upon registering
     */
    function registerFrontEnd(uint256 _kickbackRate) external;

    /*
     * Initial checks:
     * - Caller is TroveManager
     * ---
     * Cancels out the specified debt against the LUSD contained in the Stability Pool (as far as possible)
     * and transfers the Trove's ETH collateral from ActivePool to StabilityPool.
     * Only called by liquidation functions in the TroveManager.
     */
    function offset(uint256 _debt, uint256 _coll) external;

    /*
     * Returns the total amount of ETH held by the pool, accounted in an internal variable instead of `balance`,
     * to exclude edge cases like ETH received from a self-destruct.
     */
    function getETH() external view returns (uint256);

    /*
     * Returns LUSD held in the pool. Changes when users deposit/withdraw, and when Trove debt is offset.
     */
    function getTotalLUSDDeposits() external view returns (uint256);

    /*
     * Calculates the ETH gain earned by the deposit since its last snapshots were taken.
     */
    function getDepositorETHGain(address _depositor) external view returns (uint256);

    /*
     * Calculate the LQTY gain earned by a deposit since its last snapshots were taken.
     * If not tagged with a front end, the depositor gets a 100% cut of what their deposit earned.
     * Otherwise, their cut of the deposit's earnings is equal to the kickbackRate, set by the front end through
     * which they made their deposit.
     */
    function getDepositorLQTYGain(address _depositor) external view returns (uint256);

    /*
     * Return the LQTY gain earned by the front end.
     */
    function getFrontEndLQTYGain(address _frontEnd) external view returns (uint256);

    /*
     * Return the user's compounded deposit.
     */
    function getCompoundedLUSDDeposit(address _depositor) external view returns (uint256);

    /*
     * Return the front end's compounded stake.
     *
     * The front end's compounded stake is equal to the sum of its depositors' compounded deposits.
     */
    function getCompoundedFrontEndStake(address _frontEnd) external view returns (uint256);

    /*
     * Fallback function
     * Only callable by Active Pool, it just accounts for ETH received
     * receive() external payable;
     */
    function receiveETH(uint256 _amount) external;
}

// File: contracts/Interfaces/ILiquityBase.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "./IPriceFeed.sol";

interface ILiquityBase {
    function getPriceFeed() external view returns (IPriceFeed);
}

// File: contracts/Interfaces/ILiquityLUSDToken.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

import "../Dependencies/IERC20.sol";
import "../Dependencies/IERC2612.sol";

interface ILiquityLUSDToken is IERC20, IERC2612 {

    // --- Events ---

    event BorrowerOperationsAddressToggled(address borrowerOperations, bool oldFlag, bool newFlag, uint256 timestamp);
    event TroveManagerToggled(address troveManager, bool oldFlag, bool newFlag, uint256 timestamp);
    event StabilityPoolToggled(address stabilityPool, bool oldFlag, bool newFlag, uint256 timestamp);

    event LUSDTokenBalanceUpdated(address _user, uint _amount);

    // --- Functions ---

    function toggleBorrowerOperations(address borrowerOperations) external;

    function toggleTroveManager(address troveManager) external;

    function toggleStabilityPool(address stabilityPool) external;

    function mint(address _account, uint256 _amount) external;

    function burn(address _account, uint256 _amount) external;

    function sendToPool(address _sender,  address poolAddress, uint256 _amount) external;

    function returnFromPool(address poolAddress, address user, uint256 _amount ) external;
}

// File: contracts/Interfaces/IPriceFeed.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;
pragma experimental ABIEncoderV2;

interface IPriceFeed {
    // --- Events ---
    event LastGoodPriceUpdated(uint256 _lastGoodPrice);

    // --- Function ---
    function fetchPrice() external returns (uint256);
}

// File: contracts/Dependencies/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * Based on the OpenZeppelin IER20 interface:
 * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol
 *
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    function increaseAllowance(address spender, uint256 addedValue) external returns (bool);

    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    function name() external view returns (string memory);

    function symbol() external view returns (string memory);

    function decimals() external view returns (uint8);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: contracts/Dependencies/IERC2612.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/**
 * @dev Interface of the ERC2612 standard as defined in the EIP.
 *
 * Adds the {permit} method, which can be used to change one's
 * {IERC20-allowance} without having to send a transaction, by signing a
 * message. This allows users to spend tokens without having to hold Ether.
 *
 * See https://eips.ethereum.org/EIPS/eip-2612.
 *
 * Code adapted from https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2237/
 */
interface IERC2612 {
    /**
     * @dev Sets `amount` as the allowance of `spender` over `owner`'s tokens,
     * given `owner`'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 amount,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current ERC2612 nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases `owner`'s nonce by one. This
     * prevents a signature from being used multiple times.
     *
     * `owner` can limit the time a Permit is valid for by setting `deadline` to
     * a value in the near future. The deadline argument can be set to uint(-1) to
     * create Permits that effectively never expire.
     */
    function nonces(address owner) external view returns (uint256);

    function version() external view returns (string memory);

    function permitTypeHash() external view returns (bytes32);

    function domainSeparator() external view returns (bytes32);
}

// File: contracts/Dependencies/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.8.0;

/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}