// Contract: AggregatorDataProvider
// Target function: function getUserSnapshot(
 be delegator(ex: leverage contract) and borrower must be solvent after invocation or transaction will revert
    /// @param _collateralAmount The amount of Collateral Token to transfer
    /// @param _receiver The address to receive the transferred funds
    /// @param _borrower The address removing collateral from
    function removeCollateralFrom(
        uint256 _collateralAmount,
        address _receiver,
        address _borrower
    ) external payable nonReentrant isSolvent(_borrower) {
        if(whitelistedDelegators[msg.sender] == false) revert InvalidDelegator();
        if (_receiver == address(0)) revert InvalidReceiver();
        if (_borrower == address(0)) revert InvalidBorrower();

        _addInterest();
        // Note: exchange rate is irrelevant when borrower has no debt shares
        if (userBorrowShares[_borrower] > 0) {
            (bool _isBorrowAllowed, , ) = _updateExchangeRate();
            if (!_isBorrowAllowed) revert ExceedsMaxOracleDeviation();
        }
        _removeCollateral(_collateralAmount, _receiver, _borrower);
    }

    /// @notice The ```RepayAsset``` event is emitted whenever a debt position is repaid
    /// @param payer The address paying for the repayment
    /// @param borrower The borrower whose account will be credited
    /// @param amountToRepay The amount of Asset token to be transferred
    /// @param shares The amount of Borrow Shares which will be debited from the borrower after repayment
    event RepayAsset(address indexed payer, address indexed borrower, uint256 amountToRepay, uint256 shares);

    /// @notice The ```_repayAsset``` function is the internal implementation for repaying a borrow position
    /// @dev The payer must have called ERC20.approve() on the Asset Token contract prior to invocation
    /// @param _totalBorrow An in memory copy of the totalBorrow VaultAccount struct
    /// @param _amountToRepay The amount of Asset Token to transfer
    /// @param _shares The number of Borrow Shares the sender is repaying
    /// @param _payer The address from which funds will be transferred
    /// @param _borrower The borrower account which will be credited
    function _repayAsset(
        VaultAccount memory _totalBorrow,
        uint128 _amountToRepay,
        uint128 _shares,
        address _payer,
        address _borrower
    ) internal {
        // Effects: Bookkeeping
        _totalBorrow.amount -= _amountToRepay;
        _totalBorrow.shares -= _shares;

        // Effects: write to state
        userBorrowShares[_borrower] -= _shares;
        totalBorrow = _totalBorrow;

        // Interactions
        if (_payer != address(this)) {
            assetContract.safeTransferFrom(_payer, address(this), _amountToRepay);
        }
        emit RepayAsset(_payer, _borrower, _amountToRepay, _shares);
    }

    /// @notice The ```repayAsset``` function allows the caller to pay down the debt for a given borrower.
    /// @dev Caller must first invoke ```ERC20.approve()``` for the Asset Token contract
    /// @param _shares The number of Borrow Shares which will be repaid by the call
    /// @param _borrower The account for which the debt will be reduced
    /// @return _amountToRepay The amount of Asset Tokens which were transferred in order to repay the Borrow Shares
    function repayAsset(uint256 _shares, address _borrower) external nonReentrant returns (uint256 _amountToRepay) {
        if (_borrower == address(0)) revert InvalidReceiver();

        // Check if repay is paused revert if necessary
        if (isRepayPaused) revert RepayPaused();

        // Accrue interest if necessary
        _addInterest();

        // Calculate amount to repay based on shares
        VaultAccount memory _totalBorrow = totalBorrow;
        _amountToRepay = _totalBorrow.toAmount(_shares, true);

        // Execute repayment effects
        _repayAsset(_totalBorrow, _amountToRepay.toUint128(), _shares.toUint128(), msg.sender, _borrower);
    }

    // ============================================================================================
    // Functions: Liquidations
    // ============================================================================================
    /// @notice The ```Liquidate``` event is emitted when a liquidation occurs
    /// @param _borrower The borrower account for which the liquidation occurred
    /// @param _collateralForLiquidator The amount of Collateral Token transferred to the liquidator
    /// @param _sharesToLiquidate The number of Borrow Shares the liquidator repaid on behalf of the borrower
    /// @param _sharesToAdjust The number of Borrow Shares that were adjusted on liabilities and assets (a writeoff)
    event Liquidate(
        address indexed _borrower,
        uint256 _collateralForLiquidator,
        uint256 _sharesToLiquidate,
        uint256 _amountLiquidatorToRepay,
        uint256 _feesAmount,
        uint256 _sharesToAdjust,
        uint256 _amountToAdjust
    );

    /// @notice The ```liquidate``` function allows a third party to repay a borrower's debt if they have become insolvent
    /// @dev Caller must invoke ```ERC20.approve``` on the Asset Token contract prior to calling ```Liquidate()```
    /// @param _sharesToLiquidate The number of Borrow Shares repaid by the liquidator
    /// @param _deadline The timestamp after which tx will revert
    /// @param _borrower The account for which the repayment is credited and from whom collateral will be taken
    /// @return _collateralForLiquidator The amount of Collateral Token transferred to the liquidator
    function liquidate(
        uint128 _sharesToLiquidate,
        uint256 _deadline,
        address _borrower
    ) external nonReentrant returns (uint256 _collateralForLiquidator) {
        if (_borrower == address(0)) revert InvalidReceiver();

        // Check if liquidate is paused revert if necessary
        if (isLiquidatePaused) revert LiquidatePaused();

        // Ensure deadline has not passed
        if (block.timestamp > _deadline) revert PastDeadline(block.timestamp, _deadline);

        // accrue interest if necessary
        _addInterest();

        // Update exchange rate and use the lower rate for liquidations
        (, uint256 _exchangeRate, ) = _updateExchangeRate();

        // Check if borrower is solvent, revert if they are
        if (_isSolvent(_borrower, _exchangeRate)) {
            revert BorrowerSolvent();
        }

        // Read from state
        VaultAccount memory _totalBorrow = totalBorrow;
        uint256 _userCollateralBalance = userCollateralBalance[_borrower];
        uint128 _borrowerShares = userBorrowShares[_borrower].toUint128();

        // Prevent stack-too-deep
        int256 _leftoverCollateral;
        uint256 _feesAmount;
        {
            // Checks & Calculations
            // Determine the liquidation amount in collateral units (i.e. how much debt liquidator is going to repay)
            uint256 _liquidationAmountInCollateralUnits = ((_totalBorrow.toAmount(_sharesToLiquidate, false) *
                _exchangeRate) / EXCHANGE_PRECISION);

            // We first optimistically calculate the amount of collateral to give the liquidator based on the higher clean liquidation fee
            // This fee only applies if the liquidator does a full liquidation
            uint256 _optimisticCollateralForLiquidator = (_liquidationAmountInCollateralUnits *
                (LIQ_PRECISION + cleanLiquidationFee)) / LIQ_PRECISION;

            // Because interest accrues every block, _liquidationAmountInCollateralUnits from a few lines up is an ever increasing value
            // This means that leftoverCollateral can occasionally go negative by a few hundred wei (cleanLiqFee premium covers this for liquidator)
            _leftoverCollateral = (_userCollateralBalance.toInt256() - _optimisticCollateralForLiquidator.toInt256());

            // If cleanLiquidation fee results in no leftover collateral, give liquidator all the collateral
            // This will only be true when there liquidator is cleaning out the position
            _collateralForLiquidator = _leftoverCollateral <= 0
                ? _userCollateralBalance
                : (_liquidationAmountInCollateralUnits * (LIQ_PRECISION + dirtyLiquidationFee)) / LIQ_PRECISION;

            if (protocolLiquidationFee > 0) {
                _feesAmount = (protocolLiquidationFee * _collateralForLiquidator) / LIQ_PRECISION;
                _collateralForLiquidator = _collateralForLiquidator - _feesAmount;
            }
        }

        // Calculated here for use during repayment, grouped with other calcs before effects start
        uint128 _amountLiquidatorToRepay = (_totalBorrow.toAmount(_sharesToLiquidate, true)).toUint128();

        // Determine if and how much debt to adjust
        uint128 _sharesToAdjust = 0;
        {
            uint128 _amountToAdjust = 0;
            if (_leftoverCollateral <= 0) {
                // Determine if we need to adjust any shares
                _sharesToAdjust = _borrowerShares - _sharesToLiquidate;
                if (_sharesToAdjust > 0) {
                    // Write off bad debt
                    _amountToAdjust = (_totalBorrow.toAmount(_sharesToAdjust, false)).toUint128();

                    // Note: Ensure this memory struct will be passed to _repayAsset for write to state
                    _totalBorrow.amount -= _amountToAdjust;

                    // Effects: write to state
                    totalAsset.amount -= _amountToAdjust;
                }
            }
            emit Liquidate(
                _borrower,
                _collateralForLiquidator,
                _sharesToLiquidate,
                _amountLiquidatorToRepay,
                _feesAmount,
                _sharesToAdjust,
                _amountToAdjust
            );
        }

        // Effects & Interactions
        // NOTE: reverts if _shares > userBorrowShares
        _repayAsset(
            _totalBorrow,
            _amountLiquidatorToRepay,
            _sharesToLiquidate + _sharesToAdjust,
            msg.sender,
            _borrower
        ); // liquidator repays shares on behalf of borrower
        // NOTE: reverts if _collateralForLiquidator > userCollateralBalance
        // Collateral is removed on behalf of borrower and sent to liquidator
        // NOTE: reverts if _collateralForLiquidator > userCollateralBalance
        _removeCollateral(_collateralForLiquidator, msg.sender, _borrower);
        // Adjust bookkeeping only (decreases collateral held by borrower)
        _removeCollateral(_feesAmount, address(this), _borrower);
        // Adjusts bookkeeping only (increases collateral held by protocol)
        _addCollateral(address(this), _feesAmount, address(this));
    }

    // ============================================================================================
    // Functions: Leverage
    // ============================================================================================

    /// @notice The ```RepayAssetWithCollateral``` event is emitted whenever ```repayAssetWithCollateral()``` is invoked
    /// @param _borrower The borrower account for which the repayment is taking place
    /// @param _swapperAddress The address of the whitelisted swapper to use for token swaps
    /// @param _collateralToSwap The amount of Collateral Token to swap and use for repayment
    /// @param _amountAssetOut The amount of Asset Token which was repaid
    /// @param _sharesRepaid The number of Borrow Shares which were repaid
    event RepayAssetWithCollateral(
        address indexed _borrower,
        address _swapperAddress,
        uint256 _collateralToSwap,
        uint256 _amountAssetOut,
        uint256 _sharesRepaid
    );

    /// @notice The ```repayAssetWithCollateral``` function allows a borrower to repay their debt using existing collateral in contract
    /// @param _swapperAddress The address of the whitelisted swapper to use for token swaps
    /// @param _collateralToSwap The amount of Collateral Tokens to swap for Asset Tokens
    /// @param _amountAssetOutMin The minimum amount of Asset Tokens to receive during the swap
    /// @param _path An array containing the addresses of ERC20 tokens to swap.  Adheres to UniV2 style path params.
    /// @return _amountAssetOut The amount of Asset Tokens received for the Collateral Tokens, the amount the borrowers account was credited
    function repayAssetWithCollateral(
        address _swapperAddress,
        uint256 _collateralToSwap,
        uint256 _amountAssetOutMin,
        address[] calldata _path
    ) external nonReentrant isSolvent(msg.sender) returns (uint256 _amountAssetOut) {
        // Accrue interest if necessary
        _addInterest();

        // Update exchange rate and check if borrow is allowed, revert if not
        (bool _isBorrowAllowed, , ) = _updateExchangeRate();
        if (!_isBorrowAllowed) revert ExceedsMaxOracleDeviation();

        IERC20 _assetContract = assetContract;
        IERC20 _collateralContract = collateralContract;

        if (!swappers[_swapperAddress]) {
            revert BadSwapper();
        }
        if (_path[0] != address(_collateralContract)) {
            revert InvalidPath(address(_collateralContract), _path[0]);
        }
        if (_path[_path.length - 1] != address(_assetContract)) {
            revert InvalidPath(address(_assetContract), _path[_path.length - 1]);
        }

        // Effects: bookkeeping & write to state
        // Debit users collateral balance in preparation for swap, setting _recipient to address(this) means no transfer occurs
        _removeCollateral(_collateralToSwap, address(this), msg.sender);

        // Interactions
        _collateralContract.approve(_swapperAddress, _collateralToSwap);

        // Even though swappers are trusted, we verify the balance before and after swap
        uint256 _initialAssetBalance = _assetContract.balanceOf(address(this));
        ISwapper(_swapperAddress).swapExactTokensForTokens(
            _collateralToSwap,
            _amountAssetOutMin,
            _path,
            address(this),
            block.timestamp
        );
        uint256 _finalAssetBalance = _assetContract.balanceOf(address(this));

        // Note: VIOLATES CHECKS-EFFECTS-INTERACTION pattern, make sure function is NONREENTRANT
        // Effects: bookkeeping
        _amountAssetOut = _finalAssetBalance - _initialAssetBalance;
        if (_amountAssetOut < _amountAssetOutMin) {
            revert SlippageTooHigh(_amountAssetOutMin, _amountAssetOut);
        }

        VaultAccount memory _totalBorrow = totalBorrow;
        uint256 _sharesToRepay = _totalBorrow.toShares(_amountAssetOut, false);

        // Effects: write to state
        // Note: setting _payer to address(this) means no actual transfer will occur.  Contract already has funds
        _repayAsset(_totalBorrow, _amountAssetOut.toUint128(), _sharesToRepay.toUint128(), address(this), msg.sender);

        emit RepayAssetWithCollateral(msg.sender, _swapperAddress, _collateralToSwap, _amountAssetOut, _sharesToRepay);
    }
}

contract SturdyPair is IERC20Metadata, SturdyPairCore {
    using VaultAccountingLibrary for VaultAccount;
    using SafeERC20 for IERC20;
    using SafeCast for uint256;

    /// @param _configData abi.encode(address _asset, address _collateral, address _oracle, uint32 _maxOracleDeviation, address _rateContract, uint64 _fullUtilizationRate, uint256 _maxLTV, uint256 _cleanLiquidationFee, uint256 _dirtyLiquidationFee, uint256 _protocolLiquidationFee)
    /// @param _immutables abi.encode(address _circuitBreakerAddress, address _comptrollerAddress, address _timelockAddress)
    /// @param _customConfigData abi.encode(string memory _nameOfContract, string memory _symbolOfContract, uint8 _decimalsOfContract)
    constructor(
        bytes memory _configData,
        bytes memory _immutables,
        bytes memory _customConfigData
    ) SturdyPairCore(_configData, _immutables, _customConfigData) {}

    // ============================================================================================
    // ERC20 Metadata
    // ============================================================================================

    function name() public view override(ERC20, IERC20Metadata) returns (string memory) {
        return nameOfContract;
    }

    function symbol() public view override(ERC20, IERC20Metadata) returns (string memory) {
        return symbolOfContract;
    }

    function decimals() public view override(ERC20, IERC20Metadata) returns (uint8) {
        return decimalsOfContract;
    }

    // totalSupply for fToken ERC20 compatibility
    function totalSupply() public view override(ERC20, IERC20) returns (uint256) {
        return totalAsset.shares;
    }

    // ============================================================================================
    // Functions: Helpers
    // ============================================================================================

    function asset() external view returns (address) {
        return address(assetContract);
    }

    function getConstants()
        external
        pure
        returns (
            uint256 _LTV_PRECISION,
            uint256 _LIQ_PRECISION,
            uint256 _UTIL_PREC,
            uint256 _FEE_PRECISION,
            uint256 _EXCHANGE_PRECISION,
            uint256 _DEVIATION_PRECISION,
            uint256 _RATE_PRECISION,
            uint256 _MAX_PROTOCOL_FEE
        )
    {
        _LTV_PRECISION = LTV_PRECISION;
        _LIQ_PRECISION = LIQ_PRECISION;
        _UTIL_PREC = UTIL_PREC;
        _FEE_PRECISION = FEE_PRECISION;
        _EXCHANGE_PRECISION = EXCHANGE_PRECISION;
        _DEVIATION_PRECISION = DEVIATION_PRECISION;
        _RATE_PRECISION = RATE_PRECISION;
        _MAX_PROTOCOL_FEE = MAX_PROTOCOL_FEE;
    }