// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface AggregatorV3Interface {
  function decimals() external view returns (uint8);

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

  function version() external view returns (uint256);

  // getRoundData and latestRoundData should both raise "No data present"
  // if they do not have data to report, instead of returning unset values
  // which could be misinterpreted as actual reported values.
  function getRoundData(uint80 _roundId)
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );

  function latestRoundData()
    external
    view
    returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
    );
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

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 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 calldata) {
        return msg.data;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// SPDX-License-Identifier: ISC
pragma solidity ^0.8.16;

// ====================================================================
// |     ______                   _______                             |
// |    / _____________ __  __   / ____(_____  ____ _____  ________   |
// |   / /_  / ___/ __ `| |/_/  / /_  / / __ \/ __ `/ __ \/ ___/ _ \  |
// |  / __/ / /  / /_/ _>  <   / __/ / / / / / /_/ / / / / /__/  __/  |
// | /_/   /_/   \__,_/_/|_|  /_/   /_/_/ /_/\__,_/_/ /_/\___/\___/   |
// |                                                                  |
// ====================================================================
// ========================== FraxlendPair ============================
// ====================================================================
// Frax Finance: https://github.com/FraxFinance

// Primary Author
// Drake Evans: https://github.com/DrakeEvans

// Reviewers
// Dennis: https://github.com/denett
// Sam Kazemian: https://github.com/samkazemian
// Travis Moore: https://github.com/FortisFortuna
// Jack Corddry: https://github.com/corddry
// Rich Gee: https://github.com/zer0blockchain

// ====================================================================

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "./FraxlendPairConstants.sol";
import "./FraxlendPairCore.sol";
import "./libraries/VaultAccount.sol";
import "./libraries/SafeERC20.sol";
import "./interfaces/IERC4626.sol";
import "./interfaces/IFraxlendWhitelist.sol";
import "./interfaces/IRateCalculator.sol";
import "./interfaces/ISwapper.sol";

contract FraxlendPair is IERC20Metadata, FraxlendPairCore {
    using VaultAccountingLibrary for VaultAccount;
    using SafeERC20 for IERC20;

    constructor(
        bytes memory _configData,
        bytes memory _immutables,
        uint256 _maxLTV,
        uint256 _liquidationFee,
        uint256 _maturityDate,
        uint256 _penaltyRate,
        bool _isBorrowerWhitelistActive,
        bool _isLenderWhitelistActive
    )
        FraxlendPairCore(
            _configData,
            _immutables,
            _maxLTV,
            _liquidationFee,
            _maturityDate,
            _penaltyRate,
            _isBorrowerWhitelistActive,
            _isLenderWhitelistActive
        )
        ERC20("", "")
        Ownable()
        Pausable()
    {}

    // ============================================================================================
    // ERC20 Metadata
    // ============================================================================================

    function name() public view override(ERC20, IERC20Metadata) returns (string memory) {
        return nameOfContract;
    }

    function symbol() public view override(ERC20, IERC20Metadata) returns (string memory) {
        // prettier-ignore
        // solhint-disable-next-line max-line-length
        return string(abi.encodePacked("FraxlendV1 - ", collateralContract.safeSymbol(), "/", assetContract.safeSymbol()));
    }

    function decimals() public pure override(ERC20, IERC20Metadata) returns (uint8) {
        return 18;
    }

    // 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,
            uint64 _DEFAULT_INT,
            uint16 _DEFAULT_PROTOCOL_FEE,
            uint256 _MAX_PROTOCOL_FEE
        )
    {
        _LTV_PRECISION = LTV_PRECISION;
        _LIQ_PRECISION = LIQ_PRECISION;
        _UTIL_PREC = UTIL_PREC;
        _FEE_PRECISION = FEE_PRECISION;
        _EXCHANGE_PRECISION = EXCHANGE_PRECISION;
        _DEFAULT_INT = DEFAULT_INT;
        _DEFAULT_PROTOCOL_FEE = DEFAULT_PROTOCOL_FEE;
        _MAX_PROTOCOL_FEE = MAX_PROTOCOL_FEE;
    }

    /// @notice The ```getImmutableAddressBool``` function gets all the address and bool configs
    /// @return _assetContract Address of asset
    /// @return _collateralContract Address of collateral
    /// @return _oracleMultiply Address of oracle numerator
    /// @return _oracleDivide Address of oracle denominator
    /// @return _rateContract Address of rate contract
    /// @return _DEPLOYER_CONTRACT Address of deployer contract
    /// @return _COMPTROLLER_ADDRESS Address of comptroller
    /// @return _FRAXLEND_WHITELIST Address of whitelist
    /// @return _borrowerWhitelistActive Boolean is borrower whitelist active
    /// @return _lenderWhitelistActive Boolean is lender whitelist active
    function getImmutableAddressBool()
        external
        view
        returns (
            address _assetContract,
            address _collateralContract,
            address _oracleMultiply,
            address _oracleDivide,
            address _rateContract,
            address _DEPLOYER_CONTRACT,
            address _COMPTROLLER_ADDRESS,
            address _FRAXLEND_WHITELIST,
            bool _borrowerWhitelistActive,
            bool _lenderWhitelistActive
        )
    {
        _assetContract = address(assetContract);
        _collateralContract = address(collateralContract);
        _oracleMultiply = oracleMultiply;
        _oracleDivide = oracleDivide;
        _rateContract = address(rateContract);
        _DEPLOYER_CONTRACT = DEPLOYER_ADDRESS;
        _COMPTROLLER_ADDRESS = COMPTROLLER_ADDRESS;
        _FRAXLEND_WHITELIST = FRAXLEND_WHITELIST_ADDRESS;
        _borrowerWhitelistActive = borrowerWhitelistActive;
        _lenderWhitelistActive = lenderWhitelistActive;
    }

    /// @notice The ```getImmutableUint256``` function gets all uint256 config values
    /// @return _oracleNormalization Oracle normalization factor
    /// @return _maxLTV Maximum LTV
    /// @return _cleanLiquidationFee Clean Liquidation Fee
    /// @return _maturityDate Maturity Date
    /// @return _penaltyRate Penalty Rate
    function getImmutableUint256()
        external
        view
        returns (
            uint256 _oracleNormalization,
            uint256 _maxLTV,
            uint256 _cleanLiquidationFee,
            uint256 _maturityDate,
            uint256 _penaltyRate
        )
    {
        _oracleNormalization = oracleNormalization;
        _maxLTV = maxLTV;
        _cleanLiquidationFee = cleanLiquidationFee;
        _maturityDate = maturityDate;
        _penaltyRate = penaltyRate;
    }

    /// @notice The ```getUserSnapshot``` function gets user level accounting data
    /// @param _address The user address
    /// @return _userAssetShares The user fToken balance
    /// @return _userBorrowShares The user borrow shares
    /// @return _userCollateralBalance The user collateral balance
    function getUserSnapshot(address _address)
        external
        view
        returns (
            uint256 _userAssetShares,
            uint256 _userBorrowShares,
            uint256 _userCollateralBalance
        )
    {
        _userAssetShares = balanceOf(_address);
        _userBorrowShares = userBorrowShares[_address];
        _userCollateralBalance = userCollateralBalance[_address];
    }

    /// @notice The ```getPairAccounting``` function gets all pair level accounting numbers
    /// @return _totalAssetAmount Total assets deposited and interest accrued, total claims
    /// @return _totalAssetShares Total fTokens
    /// @return _totalBorrowAmount Total borrows
    /// @return _totalBorrowShares Total borrow shares
    /// @return _totalCollateral Total collateral
    function getPairAccounting()
        external
        view
        returns (
            uint128 _totalAssetAmount,
            uint128 _totalAssetShares,
            uint128 _totalBorrowAmount,
            uint128 _totalBorrowShares,
            uint256 _totalCollateral
        )
    {
        VaultAccount memory _totalAsset = totalAsset;
        _totalAssetAmount = _totalAsset.amount;
        _totalAssetShares = _totalAsset.shares;

        VaultAccount memory _totalBorrow = totalBorrow;
        _totalBorrowAmount = _totalBorrow.amount;
        _totalBorrowShares = _totalBorrow.shares;
        _totalCollateral = totalCollateral;
    }

    /// @notice The ```toBorrowShares``` function converts a given amount of borrow debt into the number of shares
    /// @param _amount Amount of borrow
    /// @param _roundUp Whether to roundup during division
    function toBorrowShares(uint256 _amount, bool _roundUp) external view returns (uint256) {
        return totalBorrow.toShares(_amount, _roundUp);
    }

    /// @notice The ```toBorrowAmount``` function converts a given amount of borrow debt into the number of shares
    /// @param _shares Shares of borrow
    /// @param _roundUp Whether to roundup during division
    /// @return The amount of asset
    function toBorrowAmount(uint256 _shares, bool _roundUp) external view returns (uint256) {
        return totalBorrow.toAmount(_shares, _roundUp);
    }

    /// @notice The ```toAssetAmount``` function converts a given number of shares to an asset amount
    /// @param _shares Shares of asset (fToken)
    /// @param _roundUp Whether to round up after division
    /// @return The amount of asset
    function toAssetAmount(uint256 _shares, bool _roundUp) external view returns (uint256) {
        return totalAsset.toAmount(_shares, _roundUp);
    }

    /// @notice The ```toAssetShares``` function converts a given asset amount to a number of asset shares (fTokens)
    /// @param _amount The amount of asset
    /// @param _roundUp Whether to round up after division
    /// @return The number of shares (fTokens)
    function toAssetShares(uint256 _amount, bool _roundUp) external view returns (uint256) {
        return totalAsset.toShares(_amount, _roundUp);
    }

    // ============================================================================================
    // Functions: Configuration
    // ============================================================================================
    /// @notice The ```SetTimeLock``` event fires when the TIME_LOCK_ADDRESS is set
    /// @param _oldAddress The original address
    /// @param _newAddress The new address
    event SetTimeLock(address _oldAddress, address _newAddress);

    /// @notice The ```setTimeLock``` function sets the TIME_LOCK address
    /// @param _newAddress the new time lock address
    function setTimeLock(address _newAddress) external {
        if (msg.sender != TIME_LOCK_ADDRESS) revert OnlyTimeLock();
        emit SetTimeLock(TIME_LOCK_ADDRESS, _newAddress);
        TIME_LOCK_ADDRESS = _newAddress;
    }

    /// @notice The ```ChangeFee``` event first when the fee is changed
    /// @param _newFee The new fee
    event ChangeFee(uint32 _newFee);

    /// @notice The ```changeFee``` function changes the protocol fee, max 50%
    /// @param _newFee The new fee
    function changeFee(uint32 _newFee) external whenNotPaused {
        if (msg.sender != TIME_LOCK_ADDRESS) revert OnlyTimeLock();
        if (_newFee > MAX_PROTOCOL_FEE) {
            revert BadProtocolFee();
        }
        _addInterest();
        currentRateInfo.feeToProtocolRate = _newFee;
        emit ChangeFee(_newFee);
    }

    /// @notice The ```WithdrawFees``` event fires when the fees are withdrawn
    /// @param _shares Number of _shares (fTokens) redeemed
    /// @param _recipient To whom the assets were sent
    /// @param _amountToTransfer The amount of fees redeemed
    event WithdrawFees(uint128 _shares, address _recipient, uint256 _amountToTransfer);

    /// @notice The ```withdrawFees``` function withdraws fees accumulated
    /// @param _shares Number of fTokens to redeem
    /// @param _recipient Address to send the assets
    /// @return _amountToTransfer Amount of assets sent to recipient
    function withdrawFees(uint128 _shares, address _recipient) external onlyOwner returns (uint256 _amountToTransfer) {
        // Grab some data from state to save gas
        VaultAccount memory _totalAsset = totalAsset;
        VaultAccount memory _totalBorrow = totalBorrow;

        // Take all available if 0 value passed
        if (_shares == 0) _shares = uint128(balanceOf(address(this)));

        // We must calculate this before we subtract from _totalAsset or invoke _burn
        _amountToTransfer = _totalAsset.toAmount(_shares, true);

        // Check for sufficient withdraw liquidity
        uint256 _assetsAvailable = _totalAssetAvailable(_totalAsset, _totalBorrow);
        if (_assetsAvailable < _amountToTransfer) {
            revert InsufficientAssetsInContract(_assetsAvailable, _amountToTransfer);
        }

        // Effects: bookkeeping
        _totalAsset.amount -= uint128(_amountToTransfer);
        _totalAsset.shares -= _shares;

        // Effects: write to states
        // NOTE: will revert if _shares > balanceOf(address(this))
        _burn(address(this), _shares);
        totalAsset = _totalAsset;

        // Interactions
        assetContract.safeTransfer(_recipient, _amountToTransfer);
        emit WithdrawFees(_shares, _recipient, _amountToTransfer);
    }

    /// @notice The ```SetSwapper``` event fires whenever a swapper is black or whitelisted
    /// @param _swapper The swapper address
    /// @param _approval The approval
    event SetSwapper(address _swapper, bool _approval);

    /// @notice The ```setSwapper``` function is called to black or whitelist a given swapper address
    /// @dev
    /// @param _swapper The swapper address
    /// @param _approval The approval
    function setSwapper(address _swapper, bool _approval) external onlyOwner {
        swappers[_swapper] = _approval;
        emit SetSwapper(_swapper, _approval);
    }

    /// @notice The ```SetApprovedLender``` event fires when a lender is black or whitelisted
    /// @param _address The address
    /// @param _approval The approval
    event SetApprovedLender(address indexed _address, bool _approval);

    /// @notice The ```setApprovedLenders``` function sets a given set of addresses to the whitelist
    /// @dev Cannot black list self
    /// @param _lenders The addresses who's status will be set
    /// @param _approval The approval status
    function setApprovedLenders(address[] calldata _lenders, bool _approval) external approvedLender(msg.sender) {
        for (uint256 i = 0; i < _lenders.length; i++) {
            // Do not set when _approval == false and _lender == msg.sender
            if (_approval || _lenders[i] != msg.sender) {
                approvedLenders[_lenders[i]] = _approval;
                emit SetApprovedLender(_lenders[i], _approval);
            }
        }
    }

    /// @notice The ```SetApprovedBorrower``` event fires when a borrower is black or whitelisted
    /// @param _address The address
    /// @param _approval The approval
    event SetApprovedBorrower(address indexed _address, bool _approval);

    /// @notice The ```setApprovedBorrowers``` function sets a given array of addresses to the whitelist
    /// @dev Cannot black list self
    /// @param _borrowers The addresses who's status will be set
    /// @param _approval The approval status
    function setApprovedBorrowers(address[] calldata _borrowers, bool _approval) external approvedBorrower {
        for (uint256 i = 0; i < _borrowers.length; i++) {
            // Do not set when _approval == false and _borrower == msg.sender
            if (_approval || _borrowers[i] != msg.sender) {
                approvedBorrowers[_borrowers[i]] = _approval;
                emit SetApprovedBorrower(_borrowers[i], _approval);
            }
        }
    }

    function pause() external {
        if (
            msg.sender != CIRCUIT_BREAKER_ADDRESS &&
            msg.sender != COMPTROLLER_ADDRESS &&
            msg.sender != owner() &&
            msg.sender != DEPLOYER_ADDRESS
        ) {
            revert ProtocolOrOwnerOnly();
        }
        _addInterest(); // accrue any interest prior to pausing as it won't accrue during pause
        _pause();
    }

    function unpause() external {
        if (msg.sender != COMPTROLLER_ADDRESS && msg.sender != owner()) {
            revert ProtocolOrOwnerOnly();
        }
        // Resets the lastTimestamp which has the effect of no interest accruing over the pause period
        _addInterest();
        _unpause();
    }
}

// SPDX-License-Identifier: ISC
pragma solidity ^0.8.16;

// ====================================================================
// |     ______                   _______                             |
// |    / _____________ __  __   / ____(_____  ____ _____  ________   |
// |   / /_  / ___/ __ `| |/_/  / /_  / / __ \/ __ `/ __ \/ ___/ _ \  |
// |  / __/ / /  / /_/ _>  <   / __/ / / / / / /_/ / / / / /__/  __/  |
// | /_/   /_/   \__,_/_/|_|  /_/   /_/_/ /_/\__,_/_/ /_/\___/\___/   |
// |                                                                  |
// ====================================================================
// ===================== FraxlendPairConstants ========================
// ====================================================================
// Frax Finance: https://github.com/FraxFinance

// Primary Author
// Drake Evans: https://github.com/DrakeEvans

// Reviewers
// Dennis: https://github.com/denett
// Sam Kazemian: https://github.com/samkazemian
// Travis Moore: https://github.com/FortisFortuna
// Jack Corddry: https://github.com/corddry
// Rich Gee: https://github.com/zer0blockchain

// ====================================================================

abstract contract FraxlendPairConstants {
    // ============================================================================================
    // Constants
    // ============================================================================================

    // Precision settings
    uint256 internal constant LTV_PRECISION = 1e5; // 5 decimals
    uint256 internal constant LIQ_PRECISION = 1e5;
    uint256 internal constant UTIL_PREC = 1e5;
    uint256 internal constant FEE_PRECISION = 1e5;
    uint256 internal constant EXCHANGE_PRECISION = 1e18;

    // Default Interest Rate (if borrows = 0)
    uint64 internal constant DEFAULT_INT = 158049988; // 0.5% annual rate 1e18 precision

    // Protocol Fee
    uint16 internal constant DEFAULT_PROTOCOL_FEE = 0; // 1e5 precision
    uint256 internal constant MAX_PROTOCOL_FEE = 5e4; // 50% 1e5 precision

    error Insolvent(uint256 _borrow, uint256 _collateral, uint256 _exchangeRate);
    error BorrowerSolvent();
    error OnlyApprovedBorrowers();
    error OnlyApprovedLenders();
    error PastMaturity();
    error ProtocolOrOwnerOnly();
    error OracleLTEZero(address _oracle);
    error InsufficientAssetsInContract(uint256 _assets, uint256 _request);
    error NotOnWhitelist(address _address);
    error NotDeployer();
    error NameEmpty();
    error AlreadyInitialized();
    error SlippageTooHigh(uint256 _minOut, uint256 _actual);
    error BadSwapper();
    error InvalidPath(address _expected, address _actual);
    error BadProtocolFee();
    error BorrowerWhitelistRequired();
    error OnlyTimeLock();
    error PriceTooLarge();
    error PastDeadline(uint256 _blockTimestamp, uint256 _deadline);
}

// SPDX-License-Identifier: ISC
pragma solidity ^0.8.16;

// ====================================================================
// |     ______                   _______                             |
// |    / _____________ __  __   / ____(_____  ____ _____  ________   |
// |   / /_  / ___/ __ `| |/_/  / /_  / / __ \/ __ `/ __ \/ ___/ _ \  |
// |  / __/ / /  / /_/ _>  <   / __/ / / / / / /_/ / / / / /__/  __/  |
// | /_/   /_/   \__,_/_/|_|  /_/   /_/_/ /_/\__,_/_/ /_/\___/\___/   |
// |                                                                  |
// ====================================================================
// ========================= FraxlendPairCore =========================
// ====================================================================
// Frax Finance: https://github.com/FraxFinance

// Primary Author
// Drake Evans: https://github.com/DrakeEvans

// Reviewers
// Dennis: https://github.com/denett
// Sam Kazemian: https://github.com/samkazemian
// Travis Moore: https://github.com/FortisFortuna
// Jack Corddry: https://github.com/corddry
// Rich Gee: https://github.com/zer0blockchain

// ====================================================================

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/math/SafeCast.sol";
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
import "./FraxlendPairConstants.sol";
import "./libraries/VaultAccount.sol";
import "./libraries/SafeERC20.sol";
import "./interfaces/IERC4626.sol";
import "./interfaces/IFraxlendWhitelist.sol";
import "./interfaces/IRateCalculator.sol";
import "./interfaces/ISwapper.sol";

/// @title FraxlendPairCore
/// @author Drake Evans (Frax Finance) https://github.com/drakeevans
/// @notice  An abstract contract which contains the core logic and storage for the FraxlendPair
abstract contract FraxlendPairCore is FraxlendPairConstants, ERC20, Ownable, Pausable, ReentrancyGuard {
    using VaultAccountingLibrary for VaultAccount;
    using SafeERC20 for IERC20;
    using SafeCast for uint256;

    string public version = "1.0.0";

    // ============================================================================================
    // Settings set by constructor() & initialize()
    // ============================================================================================

    // Asset and collateral contracts
    IERC20 internal immutable assetContract;
    IERC20 public immutable collateralContract;

    // Oracle wrapper contract and oracleData
    address public immutable oracleMultiply;
    address public immutable oracleDivide;
    uint256 public immutable oracleNormalization;

    // LTV Settings
    uint256 public immutable maxLTV;

    // Liquidation Fee
    uint256 public immutable cleanLiquidationFee;
    uint256 public immutable dirtyLiquidationFee;

    // Interest Rate Calculator Contract
    IRateCalculator public immutable rateContract; // For complex rate calculations
    bytes public rateInitCallData; // Optional extra data from init function to be passed to rate calculator

    // Swapper
    mapping(address => bool) public swappers; // approved swapper addresses

    // Deployer
    address public immutable DEPLOYER_ADDRESS;

    // Admin contracts
    address public immutable CIRCUIT_BREAKER_ADDRESS;
    address public immutable COMPTROLLER_ADDRESS;
    address public TIME_LOCK_ADDRESS;

    // Dependencies
    address public immutable FRAXLEND_WHITELIST_ADDRESS;

    // ERC20 token name, accessible via name()
    string internal nameOfContract;

    // Maturity Date & Penalty Interest Rate (per Sec)
    uint256 public immutable maturityDate;
    uint256 public immutable penaltyRate;

    // ============================================================================================
    // Storage
    // ============================================================================================

    /// @notice Stores information about the current interest rate
    /// @dev struct is packed to reduce SLOADs. feeToProtocolRate is 1e5 precision, ratePerSec is 1e18 precision
    CurrentRateInfo public currentRateInfo;
    struct CurrentRateInfo {
        uint64 lastBlock;
        uint64 feeToProtocolRate; // Fee amount 1e5 precision
        uint64 lastTimestamp;
        uint64 ratePerSec;
    }

    /// @notice Stores information about the current exchange rate. Collateral:Asset ratio
    /// @dev Struct packed to save SLOADs. Amount of Collateral Token to buy 1e18 Asset Token
    ExchangeRateInfo public exchangeRateInfo;
    struct ExchangeRateInfo {
        uint32 lastTimestamp;
        uint224 exchangeRate; // collateral:asset ratio. i.e. how much collateral to buy 1e18 asset
    }

    // Contract Level Accounting
    VaultAccount public totalAsset; // amount = total amount of assets, shares = total shares outstanding
    VaultAccount public totalBorrow; // amount = total borrow amount with interest accrued, shares = total shares outstanding
    uint256 public totalCollateral; // total amount of collateral in contract

    // User Level Accounting
    /// @notice Stores the balance of collateral for each user
    mapping(address => uint256) public userCollateralBalance; // amount of collateral each user is backed
    /// @notice Stores the balance of borrow shares for each user
    mapping(address => uint256) public userBorrowShares; // represents the shares held by individuals
    // NOTE: user shares of assets are represented as ERC-20 tokens and accessible via balanceOf()

    // Internal Whitelists
    bool public immutable borrowerWhitelistActive;
    mapping(address => bool) public approvedBorrowers;

    bool public immutable lenderWhitelistActive;
    mapping(address => bool) public approvedLenders;

    // ============================================================================================
    // Initialize
    // ============================================================================================

    /// @notice The ```constructor``` function is called on deployment
    /// @param _configData abi.encode(address _asset, address _collateral, address _oracleMultiply, address _oracleDivide, uint256 _oracleNormalization, address _rateContract, bytes memory _rateInitData)
    /// @param _maxLTV The Maximum Loan-To-Value for a borrower to be considered solvent (1e5 precision)
    /// @param _liquidationFee The fee paid to liquidators given as a % of the repayment (1e5 precision)
    /// @param _maturityDate The maturityDate date of the Pair
    /// @param _penaltyRate The interest rate after maturity date
    /// @param _isBorrowerWhitelistActive Enables borrower whitelist
    /// @param _isLenderWhitelistActive Enables lender whitelist
    constructor(
        bytes memory _configData,
        bytes memory _immutables,
        uint256 _maxLTV,
        uint256 _liquidationFee,
        uint256 _maturityDate,
        uint256 _penaltyRate,
        bool _isBorrowerWhitelistActive,
        bool _isLenderWhitelistActive
    ) {
        // Handle Immutables Configuration
        {
            (
                address _circuitBreaker,
                address _comptrollerAddress,
                address _timeLockAddress,
                address _fraxlendWhitelistAddress
            ) = abi.decode(_immutables, (address, address, address, address));

            // Deployer contract
            DEPLOYER_ADDRESS = msg.sender;
            CIRCUIT_BREAKER_ADDRESS = _circuitBreaker;
            COMPTROLLER_ADDRESS = _comptrollerAddress;
            TIME_LOCK_ADDRESS = _timeLockAddress;
            FRAXLEND_WHITELIST_ADDRESS = _fraxlendWhitelistAddress;
        }

        {
            (
                address _asset,
                address _collateral,
                address _oracleMultiply,
                address _oracleDivide,
                uint256 _oracleNormalization,
                address _rateContract,

            ) = abi.decode(_configData, (address, address, address, address, uint256, address, bytes));

            // Pair Settings
            assetContract = IERC20(_asset);
            collateralContract = IERC20(_collateral);
            currentRateInfo.feeToProtocolRate = DEFAULT_PROTOCOL_FEE;
            cleanLiquidationFee = _liquidationFee;
            dirtyLiquidationFee = (_liquidationFee * 90000) / LIQ_PRECISION; // 90% of clean fee

            if (_maxLTV >= LTV_PRECISION && !_isBorrowerWhitelistActive) revert BorrowerWhitelistRequired();
            maxLTV = _maxLTV;

            // Oracle Settings
            {
                IFraxlendWhitelist _fraxlendWhitelist = IFraxlendWhitelist(FRAXLEND_WHITELIST_ADDRESS);
                // Check that oracles are on the whitelist
                if (_oracleMultiply != address(0) && !_fraxlendWhitelist.oracleContractWhitelist(_oracleMultiply)) {
                    revert NotOnWhitelist(_oracleMultiply);
                }

                if (_oracleDivide != address(0) && !_fraxlendWhitelist.oracleContractWhitelist(_oracleDivide)) {
                    revert NotOnWhitelist(_oracleDivide);
                }

                // Write oracleData to storage
                oracleMultiply = _oracleMultiply;
                oracleDivide = _oracleDivide;
                oracleNormalization = _oracleNormalization;

                // Rate Settings
                if (!_fraxlendWhitelist.rateContractWhitelist(_rateContract)) {
                    revert NotOnWhitelist(_rateContract);
                }
            }

            rateContract = IRateCalculator(_rateContract);
        }

        // Set approved borrowers whitelist
        borrowerWhitelistActive = _isBorrowerWhitelistActive;

        // Set approved lenders whitelist active
        lenderWhitelistActive = _isLenderWhitelistActive;

        // Set maturity date & penalty interest rate
        maturityDate = _maturityDate;
        penaltyRate = _penaltyRate;
    }

    /// @notice The ```initialize``` function is called immediately after deployment
    /// @dev This function can only be called by the deployer
    /// @param _name The name of the contract
    /// @param _approvedBorrowers An array of approved borrower addresses
    /// @param _approvedLenders An array of approved lender addresses
    /// @param _rateInitCallData The configuration data for the Rate Calculator contract
    function initialize(
        string calldata _name,
        address[] calldata _approvedBorrowers,
        address[] calldata _approvedLenders,
        bytes calldata _rateInitCallData
    ) external {
        if (msg.sender != DEPLOYER_ADDRESS) {
            revert NotDeployer();
        }
        if (bytes(_name).length == 0) {
            revert NameEmpty();
        }
        if (bytes(nameOfContract).length != 0) {
            revert AlreadyInitialized();
        }

        // Set name
        nameOfContract = _name;

        // Set approved borrowers
        for (uint256 i = 0; i < _approvedBorrowers.length; ++i) {
            approvedBorrowers[_approvedBorrowers[i]] = true;
        }

        // Set approved lenders
        for (uint256 i = 0; i < _approvedLenders.length; ++i) {
            approvedLenders[_approvedLenders[i]] = true;
        }

        // Reverts if init data is not valid
        IRateCalculator(rateContract).requireValidInitData(_rateInitCallData);

        // Set rate init Data
        rateInitCallData = _rateInitCallData;

        // Instantiate Interest
        _addInterest();

        // Instantiate Exchange Rate
        _updateExchangeRate();
    }

    // ============================================================================================
    // Internal Helpers
    // ============================================================================================

    /// @notice The ```_totalAssetAvailable``` function returns the total balance of Asset Tokens in the contract
    /// @param _totalAsset VaultAccount struct which stores total amount and shares for assets
    /// @param _totalBorrow VaultAccount struct which stores total amount and shares for borrows
    /// @return The balance of Asset Tokens held by contract
    function _totalAssetAvailable(VaultAccount memory _totalAsset, VaultAccount memory _totalBorrow)
        internal
        pure
        returns (uint256)
    {
        return _totalAsset.amount - _totalBorrow.amount;
    }

    /// @notice The ```_isSolvent``` function determines if a given borrower is solvent given an exchange rate
    /// @param _borrower The borrower address to check
    /// @param _exchangeRate The exchange rate, i.e. the amount of collateral to buy 1e18 asset
    /// @return Whether borrower is solvent
    function _isSolvent(address _borrower, uint256 _exchangeRate) internal view returns (bool) {
        if (maxLTV == 0) return true;
        uint256 _borrowerAmount = totalBorrow.toAmount(userBorrowShares[_borrower], true);
        if (_borrowerAmount == 0) return true;
        uint256 _collateralAmount = userCollateralBalance[_borrower];
        if (_collateralAmount == 0) return false;

        uint256 _ltv = (((_borrowerAmount * _exchangeRate) / EXCHANGE_PRECISION) * LTV_PRECISION) / _collateralAmount;
        return _ltv <= maxLTV;
    }

    /// @notice The ```_isPastMaturity``` function determines if the current block timestamp is past the maturityDate date
    /// @return Whether or not the debt is past maturity
    function _isPastMaturity() internal view returns (bool) {
        return maturityDate != 0 && block.timestamp > maturityDate;
    }

    // ============================================================================================
    // Modifiers
    // ============================================================================================

    /// @notice Checks for solvency AFTER executing contract code
    /// @param _borrower The borrower whose solvency we will check
    modifier isSolvent(address _borrower) {
        _;
        if (!_isSolvent(_borrower, exchangeRateInfo.exchangeRate)) {
            revert Insolvent(
                totalBorrow.toAmount(userBorrowShares[_borrower], true),
                userCollateralBalance[_borrower],
                exchangeRateInfo.exchangeRate
            );
        }
    }

    /// @notice Checks if msg.sender is an approved Borrower
    modifier approvedBorrower() {
        if (borrowerWhitelistActive && !approvedBorrowers[msg.sender]) {
            revert OnlyApprovedBorrowers();
        }
        _;
    }

    /// @notice Checks if msg.sender and _receiver are both an approved Lender
    /// @param _receiver An additional receiver address to check
    modifier approvedLender(address _receiver) {
        if (lenderWhitelistActive && (!approvedLenders[msg.sender] || !approvedLenders[_receiver])) {
            revert OnlyApprovedLenders();
        }
        _;
    }

    /// @notice Ensure function is not called when passed maturity
    modifier isNotPastMaturity() {
        if (_isPastMaturity()) {
            revert PastMaturity();
        }
        _;
    }

    // ============================================================================================
    // Functions: Interest Accumulation and Adjustment
    // ============================================================================================

    /// @notice The ```AddInterest``` event is emitted when interest is accrued by borrowers
    /// @param _interestEarned The total interest accrued by all borrowers
    /// @param _rate The interest rate used to calculate accrued interest
    /// @param _deltaTime The time elapsed since last interest accrual
    /// @param _feesAmount The amount of fees paid to protocol
    /// @param _feesShare The amount of shares distributed to protocol
    event AddInterest(
        uint256 _interestEarned,
        uint256 _rate,
        uint256 _deltaTime,
        uint256 _feesAmount,
        uint256 _feesShare
    );

    /// @notice The ```UpdateRate``` event is emitted when the interest rate is updated
    /// @param _ratePerSec The old interest rate (per second)
    /// @param _deltaTime The time elapsed since last update
    /// @param _utilizationRate The utilization of assets in the Pair
    /// @param _newRatePerSec The new interest rate (per second)
    event UpdateRate(uint256 _ratePerSec, uint256 _deltaTime, uint256 _utilizationRate, uint256 _newRatePerSec);

    /// @notice The ```addInterest``` function is a public implementation of _addInterest and allows 3rd parties to trigger interest accrual
    /// @return _interestEarned The amount of interest accrued by all borrowers
    function addInterest()
        external
        nonReentrant
        returns (
            uint256 _interestEarned,
            uint256 _feesAmount,
            uint256 _feesShare,
            uint64 _newRate
        )
    {
        return _addInterest();
    }

    /// @notice The ```_addInterest``` function is invoked prior to every external function and is used to accrue interest and update interest rate
    /// @dev Can only called once per block
    /// @return _interestEarned The amount of interest accrued by all borrowers
    function _addInterest()
        internal
        returns (
            uint256 _interestEarned,
            uint256 _feesAmount,
            uint256 _feesShare,
            uint64 _newRate
        )
    {
        // Add interest only once per block
        CurrentRateInfo memory _currentRateInfo = currentRateInfo;
        if (_currentRateInfo.lastTimestamp == block.timestamp) {
            _newRate = _currentRateInfo.ratePerSec;
            return (_interestEarned, _feesAmount, _feesShare, _newRate);
        }

        // Pull some data from storage to save gas
        VaultAccount memory _totalAsset = totalAsset;
        VaultAccount memory _totalBorrow = totalBorrow;

        // If there are no borrows or contract is paused, no interest accrues and we reset interest rate
        if (_totalBorrow.shares == 0 || paused()) {
            if (!paused()) {
                _currentRateInfo.ratePerSec = DEFAULT_INT;
            }
            _currentRateInfo.lastTimestamp = uint64(block.timestamp);
            _currentRateInfo.lastBlock = uint64(block.number);

            // Effects: write to storage
            currentRateInfo = _currentRateInfo;
        } else {
            // We know totalBorrow.shares > 0
            uint256 _deltaTime = block.timestamp - _currentRateInfo.lastTimestamp;

            // NOTE: Violates Checks-Effects-Interactions pattern
            // Be sure to mark external version NONREENTRANT (even though rateContract is trusted)
            // Calc new rate
            uint256 _utilizationRate = (UTIL_PREC * _totalBorrow.amount) / _totalAsset.amount;
            if (_isPastMaturity()) {
                _newRate = uint64(penaltyRate);
            } else {
                bytes memory _rateData = abi.encode(
                    _currentRateInfo.ratePerSec,
                    _deltaTime,
                    _utilizationRate,
                    block.number - _currentRateInfo.lastBlock
                );
                _newRate = IRateCalculator(rateContract).getNewRate(_rateData, rateInitCallData);
            }

            // Event must be here to use non-mutated values
            emit UpdateRate(_currentRateInfo.ratePerSec, _deltaTime, _utilizationRate, _newRate);

            // Effects: bookkeeping
            _currentRateInfo.ratePerSec = _newRate;
            _currentRateInfo.lastTimestamp = uint64(block.timestamp);
            _currentRateInfo.lastBlock = uint64(block.number);

            // Calculate interest accrued
            _interestEarned = (_deltaTime * _totalBorrow.amount * _currentRateInfo.ratePerSec) / 1e18;

            // Accumulate interest and fees, only if no overflow upon casting
            if (
                _interestEarned + _totalBorrow.amount <= type(uint128).max &&
                _interestEarned + _totalAsset.amount <= type(uint128).max
            ) {
                _totalBorrow.amount += uint128(_interestEarned);
                _totalAsset.amount += uint128(_interestEarned);
                if (_currentRateInfo.feeToProtocolRate > 0) {
                    _feesAmount = (_interestEarned * _currentRateInfo.feeToProtocolRate) / FEE_PRECISION;

                    _feesShare = (_feesAmount * _totalAsset.shares) / (_totalAsset.amount - _feesAmount);

                    // Effects: Give new shares to this contract, effectively diluting lenders an amount equal to the fees
                    // We can safely cast because _feesShare < _feesAmount < interestEarned which is always less than uint128
                    _totalAsset.shares += uint128(_feesShare);

                    // Effects: write to storage
                    _mint(address(this), _feesShare);
                }
                emit AddInterest(_interestEarned, _currentRateInfo.ratePerSec, _deltaTime, _feesAmount, _feesShare);
            }

            // Effects: write to storage
            totalAsset = _totalAsset;
            currentRateInfo = _currentRateInfo;
            totalBorrow = _totalBorrow;
        }
    }

    // ============================================================================================
    // Functions: ExchangeRate
    // ============================================================================================
    /// @notice The ```UpdateExchangeRate``` event is emitted when the Collateral:Asset exchange rate is updated
    /// @param _rate The new rate given as the amount of Collateral Token to buy 1e18 Asset Token
    event UpdateExchangeRate(uint256 _rate);

    /// @notice The ```updateExchangeRate``` function is the external implementation of _updateExchangeRate.
    /// @dev This function is invoked at most once per block as these queries can be expensive
    /// @return _exchangeRate The new exchange rate
    function updateExchangeRate() external nonReentrant returns (uint256 _exchangeRate) {
        _exchangeRate = _updateExchangeRate();
    }

    /// @notice The ```_updateExchangeRate``` function retrieves the latest exchange rate. i.e how much collateral to buy 1e18 asset.
    /// @dev This function is invoked at most once per block as these queries can be expensive
    /// @return _exchangeRate The new exchange rate
    function _updateExchangeRate() internal returns (uint256 _exchangeRate) {
        ExchangeRateInfo memory _exchangeRateInfo = exchangeRateInfo;
        if (_exchangeRateInfo.lastTimestamp == block.timestamp) {
            return _exchangeRate = _exchangeRateInfo.exchangeRate;
        }

        uint256 _price = uint256(1e36);
        if (oracleMultiply != address(0)) {
            (, int256 _answer, , , ) = AggregatorV3Interface(oracleMultiply).latestRoundData();
            if (_answer <= 0) {
                revert OracleLTEZero(oracleMultiply);
            }
            _price = _price * uint256(_answer);
        }

        if (oracleDivide != address(0)) {
            (, int256 _answer, , , ) = AggregatorV3Interface(oracleDivide).latestRoundData();
            if (_answer <= 0) {
                revert OracleLTEZero(oracleDivide);
            }
            _price = _price / uint256(_answer);
        }

        _exchangeRate = _price / oracleNormalization;

        // write to storage, if no overflow
        if (_exchangeRate > type(uint224).max) revert PriceTooLarge();
        _exchangeRateInfo.exchangeRate = uint224(_exchangeRate);
        _exchangeRateInfo.lastTimestamp = uint32(block.timestamp);
        exchangeRateInfo = _exchangeRateInfo;
        emit UpdateExchangeRate(_exchangeRate);
    }

    // ============================================================================================
    // Functions: Lending
    // ============================================================================================

    /// @notice The ```Deposit``` event fires when a user deposits assets to the pair
    /// @param caller the msg.sender
    /// @param owner the account the fTokens are sent to
    /// @param assets the amount of assets deposited
    /// @param shares the number of fTokens minted
    event Deposit(address indexed caller, address indexed owner, uint256 assets, uint256 shares);

    /// @notice The ```_deposit``` function is the internal implementation for lending assets
    /// @dev Caller must invoke ```ERC20.approve``` on the Asset Token contract prior to calling function
    /// @param _totalAsset An in memory VaultAccount struct representing the total amounts and shares for the Asset Token
    /// @param _amount The amount of Asset Token to be transferred
    /// @param _shares The amount of Asset Shares (fTokens) to be minted
    /// @param _receiver The address to receive the Asset Shares (fTokens)
    function _deposit(
        VaultAccount memory _totalAsset,
        uint128 _amount,
        uint128 _shares,
        address _receiver
    ) internal {
        // Effects: bookkeeping
        _totalAsset.amount += _amount;
        _totalAsset.shares += _shares;

        // Effects: write back to storage
        _mint(_receiver, _shares);
        totalAsset = _totalAsset;

        // Interactions
        assetContract.safeTransferFrom(msg.sender, address(this), _amount);
        emit Deposit(msg.sender, _receiver, _amount, _shares);
    }

    /// @notice The ```deposit``` function allows a user to Lend Assets by specifying the amount of Asset Tokens to lend
    /// @dev Caller must invoke ```ERC20.approve``` on the Asset Token contract prior to calling function
    /// @param _amount The amount of Asset Token to transfer to Pair
    /// @param _receiver The address to receive the Asset Shares (fTokens)
    /// @return _sharesReceived The number of fTokens received for the deposit
    function deposit(uint256 _amount, address _receiver)
        external
        nonReentrant
        isNotPastMaturity
        whenNotPaused
        approvedLender(_receiver)
        returns (uint256 _sharesReceived)
    {
        _addInterest();
        VaultAccount memory _totalAsset = totalAsset;
        _sharesReceived = _totalAsset.toShares(_amount, false);
        _deposit(_totalAsset, _amount.toUint128(), _sharesReceived.toUint128(), _receiver);
    }

    /// @notice The ```Withdraw``` event fires when a user redeems their fTokens for the underlying asset
    /// @param caller the msg.sender
    /// @param receiver The address to which the underlying asset will be transferred to
    /// @param owner The owner of the fTokens
    /// @param assets The assets transferred
    /// @param shares The number of fTokens burned
    event Withdraw(
        address indexed caller,
        address indexed receiver,
        address indexed owner,
        uint256 assets,
        uint256 shares
    );

    /// @notice The ```_redeem``` function is an internal implementation which allows a Lender to pull their Asset Tokens out of the Pair
    /// @dev Caller must invoke ```ERC20.approve``` on the Asset Token contract prior to calling function
    /// @param _totalAsset An in-memory VaultAccount struct which holds the total amount of Asset Tokens and the total number of Asset Shares (fTokens)
    /// @param _amountToReturn The number of Asset Tokens to return
    /// @param _shares The number of Asset Shares (fTokens) to burn
    /// @param _receiver The address to which the Asset Tokens will be transferred
    /// @param _owner The owner of the Asset Shares (fTokens)
    function _redeem(
        VaultAccount memory _totalAsset,
        uint128 _amountToReturn,
        uint128 _shares,
        address _receiver,
        address _owner
    ) internal {
        if (msg.sender != _owner) {
            uint256 allowed = allowance(_owner, msg.sender);
            // NOTE: This will revert on underflow ensuring that allowance > shares
            if (allowed != type(uint256).max) _approve(_owner, msg.sender, allowed - _shares);
        }

        // Check for sufficient withdraw liquidity
        uint256 _assetsAvailable = _totalAssetAvailable(_totalAsset, totalBorrow);
        if (_assetsAvailable < _amountToReturn) {
            revert InsufficientAssetsInContract(_assetsAvailable, _amountToReturn);
        }

        // Effects: bookkeeping
        _totalAsset.amount -= _amountToReturn;
        _totalAsset.shares -= _shares;

        // Effects: write to storage
        totalAsset = _totalAsset;
        _burn(_owner, _shares);

        // Interactions
        assetContract.safeTransfer(_receiver, _amountToReturn);
        emit Withdraw(msg.sender, _receiver, _owner, _amountToReturn, _shares);
    }

    /// @notice The ```redeem``` function allows the caller to redeem their Asset Shares for Asset Tokens
    /// @param _shares The number of Asset Shares (fTokens) to burn for Asset Tokens
    /// @param _receiver The address to which the Asset Tokens will be transferred
    /// @param _owner The owner of the Asset Shares (fTokens)
    /// @return _amountToReturn The amount of Asset Tokens to be transferred
    function redeem(
        uint256 _shares,
        address _receiver,
        address _owner
    ) external nonReentrant returns (uint256 _amountToReturn) {
        _addInterest();
        VaultAccount memory _totalAsset = totalAsset;
        _amountToReturn = _totalAsset.toAmount(_shares, false);
        _redeem(_totalAsset, _amountToReturn.toUint128(), _shares.toUint128(), _receiver, _owner);
    }

    // ============================================================================================
    // Functions: Borrowing
    // ============================================================================================

    /// @notice The ```BorrowAsset``` event is emitted when a borrower increases their position
    /// @param _borrower The borrower whose account was debited
    /// @param _receiver The address to which the Asset Tokens were transferred
    /// @param _borrowAmount The amount of Asset Tokens transferred
    /// @param _sharesAdded The number of Borrow Shares the borrower was debited
    event BorrowAsset(
        address indexed _borrower,
        address indexed _receiver,
        uint256 _borrowAmount,
        uint256 _sharesAdded
    );

    /// @notice The ```_borrowAsset``` function is the internal implementation for borrowing assets
    /// @param _borrowAmount The amount of the Asset Token to borrow
    /// @param _receiver The address to receive the Asset Tokens
    /// @return _sharesAdded The amount of borrow shares the msg.sender will be debited
    function _borrowAsset(uint128 _borrowAmount, address _receiver) internal returns (uint256 _sharesAdded) {
        VaultAccount memory _totalBorrow = totalBorrow;

        // Check available capital
        uint256 _assetsAvailable = _totalAssetAvailable(totalAsset, _totalBorrow);
        if (_assetsAvailable < _borrowAmount) {
            revert InsufficientAssetsInContract(_assetsAvailable, _borrowAmount);
        }

        // Effects: Bookkeeping to add shares & amounts to total Borrow accounting
        _sharesAdded = _totalBorrow.toShares(_borrowAmount, true);
        _totalBorrow.amount += _borrowAmount;
        _totalBorrow.shares += uint128(_sharesAdded);
        // NOTE: we can safely cast here because shares are always less than amount and _borrowAmount is uint128

        // Effects: write back to storage
        totalBorrow = _totalBorrow;
        userBorrowShares[msg.sender] += _sharesAdded;

        // Interactions
        if (_receiver != address(this)) {
            assetContract.safeTransfer(_receiver, _borrowAmount);
        }
        emit BorrowAsset(msg.sender, _receiver, _borrowAmount, _sharesAdded);
    }

    /// @notice The ```borrowAsset``` function allows a user to open/increase a borrow position
    /// @dev Borrower must call ```ERC20.approve``` on the Collateral Token contract if applicable
    /// @param _borrowAmount The amount of Asset Token to borrow
    /// @param _collateralAmount The amount of Collateral Token to transfer to Pair
    /// @param _receiver The address which will receive the Asset Tokens
    /// @return _shares The number of borrow Shares the msg.sender will be debited
    function borrowAsset(
        uint256 _borrowAmount,
        uint256 _collateralAmount,
        address _receiver
    )
        external
        isNotPastMaturity
        whenNotPaused
        nonReentrant
        isSolvent(msg.sender)
        approvedBorrower
        returns (uint256 _shares)
    {
        _addInterest();
        _updateExchangeRate();
        if (_collateralAmount > 0) {
            _addCollateral(msg.sender, _collateralAmount, msg.sender);
        }
        _shares = _borrowAsset(_borrowAmount.toUint128(), _receiver);
    }

    event AddCollateral(address indexed _sender, address indexed _borrower, uint256 _collateralAmount);

    /// @notice The ```_addCollateral``` function is an internal implementation for adding collateral to a borrowers position
    /// @param _sender The source of funds for the new collateral
    /// @param _collateralAmount The amount of Collateral Token to be transferred
    /// @param _borrower The borrower account for which the collateral should be credited
    function _addCollateral(
        address _sender,
        uint256 _collateralAmount,
        address _borrower
    ) internal {
        // Effects: write to state
        userCollateralBalance[_borrower] += _collateralAmount;
        totalCollateral += _collateralAmount;

        // Interactions
        if (_sender != address(this)) {
            collateralContract.safeTransferFrom(_sender, address(this), _collateralAmount);
        }
        emit AddCollateral(_sender, _borrower, _collateralAmount);
    }

    /// @notice The ```addCollateral``` function allows the caller to add Collateral Token to a borrowers position
    /// @dev msg.sender must call ERC20.approve() on the Collateral Token contract prior to invocation
    /// @param _collateralAmount The amount of Collateral Token to be added to borrower's position
    /// @param _borrower The account to be credited
    function addCollateral(uint256 _collateralAmount, address _borrower) external nonReentrant isNotPastMaturity {
        _addInterest();
        _addCollateral(msg.sender, _collateralAmount, _borrower);
    }

    /// @notice The ```RemoveCollateral``` event is emitted when collateral is removed from a borrower's position
    /// @param _sender The account from which funds are transferred
    /// @param _collateralAmount The amount of Collateral Token to be transferred
    /// @param _receiver The address to which Collateral Tokens will be transferred
    event RemoveCollateral(
        address indexed _sender,
        uint256 _collateralAmount,
        address indexed _receiver,
        address indexed _borrower
    );

    /// @notice The ```_removeCollateral``` function is the internal implementation for removing collateral from a borrower's position
    /// @param _collateralAmount The amount of Collateral Token to remove from the borrower's position
    /// @param _receiver The address to receive the Collateral Token transferred
    /// @param _borrower The borrower whose account will be debited the Collateral amount
    function _removeCollateral(
        uint256 _collateralAmount,
        address _receiver,
        address _borrower
    ) internal {
        // Effects: write to state
        // Following line will revert on underflow if _collateralAmount > userCollateralBalance
        userCollateralBalance[_borrower] -= _collateralAmount;
        // Following line will revert on underflow if totalCollateral < _collateralAmount
        totalCollateral -= _collateralAmount;

        // Interactions
        if (_receiver != address(this)) {
            collateralContract.safeTransfer(_receiver, _collateralAmount);
        }
        emit RemoveCollateral(msg.sender, _collateralAmount, _receiver, _borrower);
    }

    /// @notice The ```removeCollateral``` function is used to remove collateral from msg.sender's borrow position
    /// @dev msg.sender 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
    function removeCollateral(uint256 _collateralAmount, address _receiver)
        external
        nonReentrant
        isSolvent(msg.sender)
    {
        _addInterest();
        // Note: exchange rate is irrelevant when borrower has no debt shares
        if (userBorrowShares[msg.sender] > 0) {
            _updateExchangeRate();
        }
        _removeCollateral(_collateralAmount, _receiver, msg.sender);
    }

    /// @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) {
        _addInterest();
        VaultAccount memory _totalBorrow = totalBorrow;
        _amountToRepay = _totalBorrow.toAmount(_shares, true);
        _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 _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 whenNotPaused nonReentrant approvedLender(msg.sender) returns (uint256 _collateralForLiquidator) {
        if (block.timestamp > _deadline) revert PastDeadline(block.timestamp, _deadline);

        _addInterest();
        uint256 _exchangeRate = _updateExchangeRate();

        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;
        {
            // Checks & Calculations
            // Determine the liquidation amount in collateral units (i.e. how much debt is liquidator 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;
        }
        // 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;
        {
            uint128 _amountToAdjust;
            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,
                _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);
    }

    // ============================================================================================
    // Functions: Leverage
    // ============================================================================================

    /// @notice The ```LeveragedPosition``` event is emitted when a borrower takes out a new leveraged position
    /// @param _borrower The account for which the debt is debited
    /// @param _swapperAddress The address of the swapper which conforms the FraxSwap interface
    /// @param _borrowAmount The amount of Asset Token to be borrowed to be borrowed
    /// @param _borrowShares The number of Borrow Shares the borrower is credited
    /// @param _initialCollateralAmount The amount of initial Collateral Tokens supplied by the borrower
    /// @param _amountCollateralOut The amount of Collateral Token which was received for the Asset Tokens
    event LeveragedPosition(
        address indexed _borrower,
        address _swapperAddress,
        uint256 _borrowAmount,
        uint256 _borrowShares,
        uint256 _initialCollateralAmount,
        uint256 _amountCollateralOut
    );

    /// @notice The ```leveragedPosition``` function allows a user to enter a leveraged borrow position with minimal upfront Collateral
    /// @dev Caller must invoke ```ERC20.approve()``` on the Collateral Token contract prior to calling function
    /// @param _swapperAddress The address of the whitelisted swapper to use to swap borrowed Asset Tokens for Collateral Tokens
    /// @param _borrowAmount The amount of Asset Tokens borrowed
    /// @param _initialCollateralAmount The initial amount of Collateral Tokens supplied by the borrower
    /// @param _amountCollateralOutMin The minimum amount of Collateral Tokens to be received in exchange for the borrowed Asset Tokens
    /// @param _path An array containing the addresses of ERC20 tokens to swap.  Adheres to UniV2 style path params.
    /// @return _totalCollateralBalance The total amount of Collateral Tokens added to a users account (initial + swap)
    function leveragedPosition(
        address _swapperAddress,
        uint256 _borrowAmount,
        uint256 _initialCollateralAmount,
        uint256 _amountCollateralOutMin,
        address[] memory _path
    )
        external
        isNotPastMaturity
        nonReentrant
        whenNotPaused
        approvedBorrower
        isSolvent(msg.sender)
        returns (uint256 _totalCollateralBalance)
    {
        _addInterest();
        _updateExchangeRate();

        IERC20 _assetContract = assetContract;
        IERC20 _collateralContract = collateralContract;

        if (!swappers[_swapperAddress]) {
            revert BadSwapper();
        }
        if (_path[0] != address(_assetContract)) {
            revert InvalidPath(address(_assetContract), _path[0]);
        }
        if (_path[_path.length - 1] != address(_collateralContract)) {
            revert InvalidPath(address(_collateralContract), _path[_path.length - 1]);
        }

        // Add initial collateral
        if (_initialCollateralAmount > 0) {
            _addCollateral(msg.sender, _initialCollateralAmount, msg.sender);
        }

        // Debit borrowers account
        // setting recipient to address(this) means no transfer will happen
        uint256 _borrowShares = _borrowAsset(_borrowAmount.toUint128(), address(this));

        // Interactions
        _assetContract.approve(_swapperAddress, _borrowAmount);

        // Even though swappers are trusted, we verify the balance before and after swap
        uint256 _initialCollateralBalance = _collateralContract.balanceOf(address(this));
        ISwapper(_swapperAddress).swapExactTokensForTokens(
            _borrowAmount,
            _amountCollateralOutMin,
            _path,
            address(this),
            block.timestamp
        );
        uint256 _finalCollateralBalance = _collateralContract.balanceOf(address(this));

        // Note: VIOLATES CHECKS-EFFECTS-INTERACTION pattern, make sure function is NONREENTRANT
        // Effects: bookkeeping & write to state
        uint256 _amountCollateralOut = _finalCollateralBalance - _initialCollateralBalance;
        if (_amountCollateralOut < _amountCollateralOutMin) {
            revert SlippageTooHigh(_amountCollateralOutMin, _amountCollateralOut);
        }

        // address(this) as _sender means no transfer occurs as the pair has already received the collateral during swap
        _addCollateral(address(this), _amountCollateralOut, msg.sender);

        _totalCollateralBalance = _initialCollateralAmount + _amountCollateralOut;
        emit LeveragedPosition(
            msg.sender,
            _swapperAddress,
            _borrowAmount,
            _borrowShares,
            _initialCollateralAmount,
            _amountCollateralOut
        );
    }

    /// @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) {
        _addInterest();
        _updateExchangeRate();

        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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC20.sol)

pragma solidity ^0.8.0;

import "../token/ERC20/IERC20.sol";

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: ISC
pragma solidity >=0.8.16;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";

interface IERC4626 is IERC20, IERC20Metadata {
    event Deposit(address indexed caller, address indexed owner, uint256 assets, uint256 shares);
    event Withdraw(
        address indexed caller,
        address indexed receiver,
        address indexed owner,
        uint256 assets,
        uint256 shares
    );

    function asset() external view returns (address);

    function convertToAssets(uint256 shares) external view returns (uint256);

    function convertToShares(uint256 assets) external view returns (uint256);

    function maxDeposit(address) external view returns (uint256);

    function maxMint(address) external view returns (uint256);

    function maxRedeem(address owner) external view returns (uint256);

    function maxWithdraw(address owner) external view returns (uint256);

    function previewDeposit(uint256 assets) external view returns (uint256);

    function previewMint(uint256 shares) external view returns (uint256);

    function previewRedeem(uint256 shares) external view returns (uint256);

    function previewWithdraw(uint256 assets) external view returns (uint256);

    function totalAssets() external view returns (uint256);

    function mint(uint256 shares, address receiver) external returns (uint256 assets);

    function deposit(uint256 assets, address receiver) external returns (uint256 shares);

    function redeem(
        uint256 shares,
        address receiver,
        address owner
    ) external returns (uint256 assets);

    function withdraw(
        uint256 assets,
        address receiver,
        address owner
    ) external returns (uint256 shares);
}

// SPDX-License-Identifier: ISC
pragma solidity >=0.8.16;

interface IFraxlendWhitelist {
    function fraxlendDeployerWhitelist(address) external view returns (bool);

    function oracleContractWhitelist(address) external view returns (bool);

    function owner() external view returns (address);

    function rateContractWhitelist(address) external view returns (bool);

    function renounceOwnership() external;

    function setFraxlendDeployerWhitelist(address[] calldata _addresses, bool _bool) external;

    function setOracleContractWhitelist(address[] calldata _addresses, bool _bool) external;

    function setRateContractWhitelist(address[] calldata _addresses, bool _bool) external;

    function transferOwnership(address newOwner) external;
}

// SPDX-License-Identifier: ISC
pragma solidity >=0.8.16;

interface IRateCalculator {
    function name() external pure returns (string memory);

    function requireValidInitData(bytes calldata _initData) external pure;

    function getConstants() external pure returns (bytes memory _calldata);

    function getNewRate(bytes calldata _data, bytes calldata _initData) external pure returns (uint64 _newRatePerSec);
}

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.16;

interface ISwapper {
    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.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.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * 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.
 */
abstract contract Ownable is Context {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

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

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

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/Pausable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/math/SafeCast.sol)

pragma solidity ^0.8.0;

/**
 * @dev Wrappers over Solidity's uintXX/intXX casting operators with added overflow
 * checks.
 *
 * Downcasting from uint256/int256 in Solidity does not revert on overflow. This can
 * easily result in undesired exploitation or bugs, since developers usually
 * assume that overflows raise errors. `SafeCast` restores this intuition by
 * reverting the transaction when such 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.
 *
 * Can be combined with {SafeMath} and {SignedSafeMath} to extend it to smaller types, by performing
 * all math on `uint256` and `int256` and then downcasting.
 */
library SafeCast {
    /**
     * @dev Returns the downcasted uint224 from uint256, reverting on
     * overflow (when the input is greater than largest uint224).
     *
     * Counterpart to Solidity's `uint224` operator.
     *
     * Requirements:
     *
     * - input must fit into 224 bits
     */
    function toUint224(uint256 value) internal pure returns (uint224) {
        require(value <= type(uint224).max, "SafeCast: value doesn't fit in 224 bits");
        return uint224(value);
    }

    /**
     * @dev Returns the downcasted uint128 from uint256, reverting on
     * overflow (when the input is greater than largest uint128).
     *
     * Counterpart to Solidity's `uint128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     */
    function toUint128(uint256 value) internal pure returns (uint128) {
        require(value <= type(uint128).max, "SafeCast: value doesn't fit in 128 bits");
        return uint128(value);
    }

    /**
     * @dev Returns the downcasted uint96 from uint256, reverting on
     * overflow (when the input is greater than largest uint96).
     *
     * Counterpart to Solidity's `uint96` operator.
     *
     * Requirements:
     *
     * - input must fit into 96 bits
     */
    function toUint96(uint256 value) internal pure returns (uint96) {
        require(value <= type(uint96).max, "SafeCast: value doesn't fit in 96 bits");
        return uint96(value);
    }

    /**
     * @dev Returns the downcasted uint64 from uint256, reverting on
     * overflow (when the input is greater than largest uint64).
     *
     * Counterpart to Solidity's `uint64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     */
    function toUint64(uint256 value) internal pure returns (uint64) {
        require(value <= type(uint64).max, "SafeCast: value doesn't fit in 64 bits");
        return uint64(value);
    }

    /**
     * @dev Returns the downcasted uint32 from uint256, reverting on
     * overflow (when the input is greater than largest uint32).
     *
     * Counterpart to Solidity's `uint32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     */
    function toUint32(uint256 value) internal pure returns (uint32) {
        require(value <= type(uint32).max, "SafeCast: value doesn't fit in 32 bits");
        return uint32(value);
    }

    /**
     * @dev Returns the downcasted uint16 from uint256, reverting on
     * overflow (when the input is greater than largest uint16).
     *
     * Counterpart to Solidity's `uint16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     */
    function toUint16(uint256 value) internal pure returns (uint16) {
        require(value <= type(uint16).max, "SafeCast: value doesn't fit in 16 bits");
        return uint16(value);
    }

    /**
     * @dev Returns the downcasted uint8 from uint256, reverting on
     * overflow (when the input is greater than largest uint8).
     *
     * Counterpart to Solidity's `uint8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     */
    function toUint8(uint256 value) internal pure returns (uint8) {
        require(value <= type(uint8).max, "SafeCast: value doesn't fit in 8 bits");
        return uint8(value);
    }

    /**
     * @dev Converts a signed int256 into an unsigned uint256.
     *
     * Requirements:
     *
     * - input must be greater than or equal to 0.
     */
    function toUint256(int256 value) internal pure returns (uint256) {
        require(value >= 0, "SafeCast: value must be positive");
        return uint256(value);
    }

    /**
     * @dev Returns the downcasted int128 from int256, reverting on
     * overflow (when the input is less than smallest int128 or
     * greater than largest int128).
     *
     * Counterpart to Solidity's `int128` operator.
     *
     * Requirements:
     *
     * - input must fit into 128 bits
     *
     * _Available since v3.1._
     */
    function toInt128(int256 value) internal pure returns (int128) {
        require(value >= type(int128).min && value <= type(int128).max, "SafeCast: value doesn't fit in 128 bits");
        return int128(value);
    }

    /**
     * @dev Returns the downcasted int64 from int256, reverting on
     * overflow (when the input is less than smallest int64 or
     * greater than largest int64).
     *
     * Counterpart to Solidity's `int64` operator.
     *
     * Requirements:
     *
     * - input must fit into 64 bits
     *
     * _Available since v3.1._
     */
    function toInt64(int256 value) internal pure returns (int64) {
        require(value >= type(int64).min && value <= type(int64).max, "SafeCast: value doesn't fit in 64 bits");
        return int64(value);
    }

    /**
     * @dev Returns the downcasted int32 from int256, reverting on
     * overflow (when the input is less than smallest int32 or
     * greater than largest int32).
     *
     * Counterpart to Solidity's `int32` operator.
     *
     * Requirements:
     *
     * - input must fit into 32 bits
     *
     * _Available since v3.1._
     */
    function toInt32(int256 value) internal pure returns (int32) {
        require(value >= type(int32).min && value <= type(int32).max, "SafeCast: value doesn't fit in 32 bits");
        return int32(value);
    }

    /**
     * @dev Returns the downcasted int16 from int256, reverting on
     * overflow (when the input is less than smallest int16 or
     * greater than largest int16).
     *
     * Counterpart to Solidity's `int16` operator.
     *
     * Requirements:
     *
     * - input must fit into 16 bits
     *
     * _Available since v3.1._
     */
    function toInt16(int256 value) internal pure returns (int16) {
        require(value >= type(int16).min && value <= type(int16).max, "SafeCast: value doesn't fit in 16 bits");
        return int16(value);
    }

    /**
     * @dev Returns the downcasted int8 from int256, reverting on
     * overflow (when the input is less than smallest int8 or
     * greater than largest int8).
     *
     * Counterpart to Solidity's `int8` operator.
     *
     * Requirements:
     *
     * - input must fit into 8 bits.
     *
     * _Available since v3.1._
     */
    function toInt8(int256 value) internal pure returns (int8) {
        require(value >= type(int8).min && value <= type(int8).max, "SafeCast: value doesn't fit in 8 bits");
        return int8(value);
    }

    /**
     * @dev Converts an unsigned uint256 into a signed int256.
     *
     * Requirements:
     *
     * - input must be less than or equal to maxInt256.
     */
    function toInt256(uint256 value) internal pure returns (int256) {
        // Note: Unsafe cast below is okay because `type(int256).max` is guaranteed to be positive
        require(value <= uint256(type(int256).max), "SafeCast: value doesn't fit in an int256");
        return int256(value);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// SPDX-License-Identifier: ISC
pragma solidity ^0.8.16;

struct VaultAccount {
    uint128 amount; // Total amount, analogous to market cap
    uint128 shares; // Total shares, analogous to shares outstanding
}

/// @title VaultAccount Library
/// @author Drake Evans (Frax Finance) github.com/drakeevans, modified from work by @Boring_Crypto github.com/boring_crypto
/// @notice Provides a library for use with the VaultAccount struct, provides convenient math implementations
/// @dev Uses uint128 to save on storage
library VaultAccountingLibrary {
    /// @notice Calculates the shares value in relationship to `amount` and `total`
    /// @dev Given an amount, return the appropriate number of shares
    function toShares(
        VaultAccount memory total,
        uint256 amount,
        bool roundUp
    ) internal pure returns (uint256 shares) {
        if (total.amount == 0) {
            shares = amount;
        } else {
            shares = (amount * total.shares) / total.amount;
            if (roundUp && (shares * total.amount) / total.shares < amount) {
                shares = shares + 1;
            }
        }
    }

    /// @notice Calculates the amount value in relationship to `shares` and `total`
    /// @dev Given a number of shares, returns the appropriate amount
    function toAmount(
        VaultAccount memory total,
        uint256 shares,
        bool roundUp
    ) internal pure returns (uint256 amount) {
        if (total.shares == 0) {
            amount = shares;
        } else {
            amount = (shares * total.amount) / total.shares;
            if (roundUp && (amount * total.shares) / total.amount < shares) {
                amount = amount + 1;
            }
        }
    }
}

{
  "compilationTarget": {
    "src/contracts/FraxlendPair.sol": "FraxlendPair"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "none"
  },
  "optimizer": {
    "enabled": true,
    "runs": 725
  },
  "remappings": [],
  "viaIR": true
}