BendUpgradeableProxy

< // SPDX-License-Identifier: agpl-3.0
pragma solidity 0.8.4;

import {TransparentUpgradeableProxy} from "@openzeppelin/contracts/proxy/transparent/TransparentUpgradeableProxy.sol";
import "../helpers/Errors.sol";

contract BendUpgradeableProxy is TransparentUpgradeableProxy {
  constructor(
    address _logic,
    address admin_,
    bytes memory _data
  ) payable TransparentUpgradeableProxy(_logic, admin_, _data) {}

  modifier OnlyAdmin() {
    require(msg.sender == _getAdmin(), Errors.CALLER_NOT_POOL_ADMIN);
    _;
  }

  function getImplementation() external view OnlyAdmin returns (address) {
    return _getImplementation();
  }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/transparent/TransparentUpgradeableProxy.sol)

pragma solidity ^0.8.0;

import "../ERC1967/ERC1967Proxy.sol";

/**
 * @dev This contract implements a proxy that is upgradeable by an admin.
 *
 * To avoid https://medium.com/nomic-labs-blog/malicious-backdoors-in-ethereum-proxies-62629adf3357[proxy selector
 * clashing], which can potentially be used in an attack, this contract uses the
 * https://blog.openzeppelin.com/the-transparent-proxy-pattern/[transparent proxy pattern]. This pattern implies two
 * things that go hand in hand:
 *
 * 1. If any account other than the admin calls the proxy, the call will be forwarded to the implementation, even if
 * that call matches one of the admin functions exposed by the proxy itself.
 * 2. If the admin calls the proxy, it can access the admin functions, but its calls will never be forwarded to the
 * implementation. If the admin tries to call a function on the implementation it will fail with an error that says
 * "admin cannot fallback to proxy target".
 *
 * These properties mean that the admin account can only be used for admin actions like upgrading the proxy or changing
 * the admin, so it's best if it's a dedicated account that is not used for anything else. This will avoid headaches due
 * to sudden errors when trying to call a function from the proxy implementation.
 *
 * Our recommendation is for the dedicated account to be an instance of the {ProxyAdmin} contract. If set up this way,
 * you should think of the `ProxyAdmin` instance as the real administrative interface of your proxy.
 */
contract TransparentUpgradeableProxy is ERC1967Proxy {
    /**
     * @dev Initializes an upgradeable proxy managed by `_admin`, backed by the implementation at `_logic`, and
     * optionally initialized with `_data` as explained in {ERC1967Proxy-constructor}.
     */
    constructor(
        address _logic,
        address admin_,
        bytes memory _data
    ) payable ERC1967Proxy(_logic, _data) {
        assert(_ADMIN_SLOT == bytes32(uint256(keccak256("eip1967.proxy.admin")) - 1));
        _changeAdmin(admin_);
    }

    /**
     * @dev Modifier used internally that will delegate the call to the implementation unless the sender is the admin.
     */
    modifier ifAdmin() {
        if (msg.sender == _getAdmin()) {
            _;
        } else {
            _fallback();
        }
    }

    /**
     * @dev Returns the current admin.
     *
     * NOTE: Only the admin can call this function. See {ProxyAdmin-getProxyAdmin}.
     *
     * TIP: To get this value clients can read directly from the storage slot shown below (specified by EIP1967) using the
     * https://eth.wiki/json-rpc/API#eth_getstorageat[`eth_getStorageAt`] RPC call.
     * `0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103`
     */
    function admin() external ifAdmin returns (address admin_) {
        admin_ = _getAdmin();
    }

    /**
     * @dev Returns the current implementation.
     *
     * NOTE: Only the admin can call this function. See {ProxyAdmin-getProxyImplementation}.
     *
     * TIP: To get this value clients can read directly from the storage slot shown below (specified by EIP1967) using the
     * https://eth.wiki/json-rpc/API#eth_getstorageat[`eth_getStorageAt`] RPC call.
     * `0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc`
     */
    function implementation() external ifAdmin returns (address implementation_) {
        implementation_ = _implementation();
    }

    /**
     * @dev Changes the admin of the proxy.
     *
     * Emits an {AdminChanged} event.
     *
     * NOTE: Only the admin can call this function. See {ProxyAdmin-changeProxyAdmin}.
     */
    function changeAdmin(address newAdmin) external virtual ifAdmin {
        _changeAdmin(newAdmin);
    }

    /**
     * @dev Upgrade the implementation of the proxy.
     *
     * NOTE: Only the admin can call this function. See {ProxyAdmin-upgrade}.
     */
    function upgradeTo(address newImplementation) external ifAdmin {
        _upgradeToAndCall(newImplementation, bytes(""), false);
    }

    /**
     * @dev Upgrade the implementation of the proxy, and then call a function from the new implementation as specified
     * by `data`, which should be an encoded function call. This is useful to initialize new storage variables in the
     * proxied contract.
     *
     * NOTE: Only the admin can call this function. See {ProxyAdmin-upgradeAndCall}.
     */
    function upgradeToAndCall(address newImplementation, bytes calldata data) external payable ifAdmin {
        _upgradeToAndCall(newImplementation, data, true);
    }

    /**
     * @dev Returns the current admin.
     */
    function _admin() internal view virtual returns (address) {
        return _getAdmin();
    }

    /**
     * @dev Makes sure the admin cannot access the fallback function. See {Proxy-_beforeFallback}.
     */
    function _beforeFallback() internal virtual override {
        require(msg.sender != _getAdmin(), "TransparentUpgradeableProxy: admin cannot fallback to proxy target");
        super._beforeFallback();
    }
}
// SPDX-License-Identifier: agpl-3.0
pragma solidity 0.8.4;

/**
 * @title Errors library
 * @author Bend
 * @notice Defines the error messages emitted by the different contracts of the Bend protocol
 */
library Errors {
  enum ReturnCode {
    SUCCESS,
    FAILED
  }

  string public constant SUCCESS = "0";

  //common errors
  string public constant CALLER_NOT_POOL_ADMIN = "100"; // 'The caller must be the pool admin'
  string public constant CALLER_NOT_ADDRESS_PROVIDER = "101";
  string public constant INVALID_FROM_BALANCE_AFTER_TRANSFER = "102";
  string public constant INVALID_TO_BALANCE_AFTER_TRANSFER = "103";

  //math library erros
  string public constant MATH_MULTIPLICATION_OVERFLOW = "200";
  string public constant MATH_ADDITION_OVERFLOW = "201";
  string public constant MATH_DIVISION_BY_ZERO = "202";

  //validation & check errors
  string public constant VL_INVALID_AMOUNT = "301"; // 'Amount must be greater than 0'
  string public constant VL_NO_ACTIVE_RESERVE = "302"; // 'Action requires an active reserve'
  string public constant VL_RESERVE_FROZEN = "303"; // 'Action cannot be performed because the reserve is frozen'
  string public constant VL_NOT_ENOUGH_AVAILABLE_USER_BALANCE = "304"; // 'User cannot withdraw more than the available balance'
  string public constant VL_BORROWING_NOT_ENABLED = "305"; // 'Borrowing is not enabled'
  string public constant VL_COLLATERAL_BALANCE_IS_0 = "306"; // 'The collateral balance is 0'
  string public constant VL_HEALTH_FACTOR_LOWER_THAN_LIQUIDATION_THRESHOLD = "307"; // 'Health factor is lesser than the liquidation threshold'
  string public constant VL_COLLATERAL_CANNOT_COVER_NEW_BORROW = "308"; // 'There is not enough collateral to cover a new borrow'
  string public constant VL_NO_DEBT_OF_SELECTED_TYPE = "309"; // 'for repayment of stable debt, the user needs to have stable debt, otherwise, he needs to have variable debt'
  string public constant VL_NO_ACTIVE_NFT = "310";
  string public constant VL_NFT_FROZEN = "311";
  string public constant VL_SPECIFIED_CURRENCY_NOT_BORROWED_BY_USER = "312"; // 'User did not borrow the specified currency'
  string public constant VL_INVALID_HEALTH_FACTOR = "313";
  string public constant VL_INVALID_ONBEHALFOF_ADDRESS = "314";
  string public constant VL_INVALID_TARGET_ADDRESS = "315";
  string public constant VL_INVALID_RESERVE_ADDRESS = "316";
  string public constant VL_SPECIFIED_LOAN_NOT_BORROWED_BY_USER = "317";
  string public constant VL_SPECIFIED_RESERVE_NOT_BORROWED_BY_USER = "318";
  string public constant VL_HEALTH_FACTOR_HIGHER_THAN_LIQUIDATION_THRESHOLD = "319";

  //lend pool errors
  string public constant LP_CALLER_NOT_LEND_POOL_CONFIGURATOR = "400"; // 'The caller of the function is not the lending pool configurator'
  string public constant LP_IS_PAUSED = "401"; // 'Pool is paused'
  string public constant LP_NO_MORE_RESERVES_ALLOWED = "402";
  string public constant LP_NOT_CONTRACT = "403";
  string public constant LP_BORROW_NOT_EXCEED_LIQUIDATION_THRESHOLD = "404";
  string public constant LP_BORROW_IS_EXCEED_LIQUIDATION_PRICE = "405";
  string public constant LP_NO_MORE_NFTS_ALLOWED = "406";
  string public constant LP_INVALIED_USER_NFT_AMOUNT = "407";
  string public constant LP_INCONSISTENT_PARAMS = "408";
  string public constant LP_NFT_IS_NOT_USED_AS_COLLATERAL = "409";
  string public constant LP_CALLER_MUST_BE_AN_BTOKEN = "410";
  string public constant LP_INVALIED_NFT_AMOUNT = "411";
  string public constant LP_NFT_HAS_USED_AS_COLLATERAL = "412";
  string public constant LP_DELEGATE_CALL_FAILED = "413";
  string public constant LP_AMOUNT_LESS_THAN_EXTRA_DEBT = "414";
  string public constant LP_AMOUNT_LESS_THAN_REDEEM_THRESHOLD = "415";

  //lend pool loan errors
  string public constant LPL_INVALID_LOAN_STATE = "480";
  string public constant LPL_INVALID_LOAN_AMOUNT = "481";
  string public constant LPL_INVALID_TAKEN_AMOUNT = "482";
  string public constant LPL_AMOUNT_OVERFLOW = "483";
  string public constant LPL_BID_PRICE_LESS_THAN_LIQUIDATION_PRICE = "484";
  string public constant LPL_BID_PRICE_LESS_THAN_HIGHEST_PRICE = "485";
  string public constant LPL_BID_REDEEM_DURATION_HAS_END = "486";
  string public constant LPL_BID_USER_NOT_SAME = "487";
  string public constant LPL_BID_REPAY_AMOUNT_NOT_ENOUGH = "488";
  string public constant LPL_BID_AUCTION_DURATION_HAS_END = "489";
  string public constant LPL_BID_AUCTION_DURATION_NOT_END = "490";
  string public constant LPL_BID_PRICE_LESS_THAN_BORROW = "491";
  string public constant LPL_INVALID_BIDDER_ADDRESS = "492";
  string public constant LPL_AMOUNT_LESS_THAN_BID_FINE = "493";

  //common token errors
  string public constant CT_CALLER_MUST_BE_LEND_POOL = "500"; // 'The caller of this function must be a lending pool'
  string public constant CT_INVALID_MINT_AMOUNT = "501"; //invalid amount to mint
  string public constant CT_INVALID_BURN_AMOUNT = "502"; //invalid amount to burn

  //reserve logic errors
  string public constant RL_RESERVE_ALREADY_INITIALIZED = "601"; // 'Reserve has already been initialized'
  string public constant RL_LIQUIDITY_INDEX_OVERFLOW = "602"; //  Liquidity index overflows uint128
  string public constant RL_VARIABLE_BORROW_INDEX_OVERFLOW = "603"; //  Variable borrow index overflows uint128
  string public constant RL_LIQUIDITY_RATE_OVERFLOW = "604"; //  Liquidity rate overflows uint128
  string public constant RL_VARIABLE_BORROW_RATE_OVERFLOW = "605"; //  Variable borrow rate overflows uint128

  //configure errors
  string public constant LPC_RESERVE_LIQUIDITY_NOT_0 = "700"; // 'The liquidity of the reserve needs to be 0'
  string public constant LPC_INVALID_CONFIGURATION = "701"; // 'Invalid risk parameters for the reserve'
  string public constant LPC_CALLER_NOT_EMERGENCY_ADMIN = "702"; // 'The caller must be the emergency admin'
  string public constant LPC_INVALIED_BNFT_ADDRESS = "703";
  string public constant LPC_INVALIED_LOAN_ADDRESS = "704";
  string public constant LPC_NFT_LIQUIDITY_NOT_0 = "705";

  //reserve config errors
  string public constant RC_INVALID_LTV = "730";
  string public constant RC_INVALID_LIQ_THRESHOLD = "731";
  string public constant RC_INVALID_LIQ_BONUS = "732";
  string public constant RC_INVALID_DECIMALS = "733";
  string public constant RC_INVALID_RESERVE_FACTOR = "734";
  string public constant RC_INVALID_REDEEM_DURATION = "735";
  string public constant RC_INVALID_AUCTION_DURATION = "736";
  string public constant RC_INVALID_REDEEM_FINE = "737";
  string public constant RC_INVALID_REDEEM_THRESHOLD = "738";

  //address provider erros
  string public constant LPAPR_PROVIDER_NOT_REGISTERED = "760"; // 'Provider is not registered'
  string public constant LPAPR_INVALID_ADDRESSES_PROVIDER_ID = "761";
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/ERC1967/ERC1967Proxy.sol)

pragma solidity ^0.8.0;

import "../Proxy.sol";
import "./ERC1967Upgrade.sol";

/**
 * @dev This contract implements an upgradeable proxy. It is upgradeable because calls are delegated to an
 * implementation address that can be changed. This address is stored in storage in the location specified by
 * https://eips.ethereum.org/EIPS/eip-1967[EIP1967], so that it doesn't conflict with the storage layout of the
 * implementation behind the proxy.
 */
contract ERC1967Proxy is Proxy, ERC1967Upgrade {
    /**
     * @dev Initializes the upgradeable proxy with an initial implementation specified by `_logic`.
     *
     * If `_data` is nonempty, it's used as data in a delegate call to `_logic`. This will typically be an encoded
     * function call, and allows initializating the storage of the proxy like a Solidity constructor.
     */
    constructor(address _logic, bytes memory _data) payable {
        assert(_IMPLEMENTATION_SLOT == bytes32(uint256(keccak256("eip1967.proxy.implementation")) - 1));
        _upgradeToAndCall(_logic, _data, false);
    }

    /**
     * @dev Returns the current implementation address.
     */
    function _implementation() internal view virtual override returns (address impl) {
        return ERC1967Upgrade._getImplementation();
    }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/Proxy.sol)

pragma solidity ^0.8.0;

/**
 * @dev This abstract contract provides a fallback function that delegates all calls to another contract using the EVM
 * instruction `delegatecall`. We refer to the second contract as the _implementation_ behind the proxy, and it has to
 * be specified by overriding the virtual {_implementation} function.
 *
 * Additionally, delegation to the implementation can be triggered manually through the {_fallback} function, or to a
 * different contract through the {_delegate} function.
 *
 * The success and return data of the delegated call will be returned back to the caller of the proxy.
 */
abstract contract Proxy {
    /**
     * @dev Delegates the current call to `implementation`.
     *
     * This function does not return to its internall call site, it will return directly to the external caller.
     */
    function _delegate(address implementation) internal virtual {
        assembly {
            // Copy msg.data. We take full control of memory in this inline assembly
            // block because it will not return to Solidity code. We overwrite the
            // Solidity scratch pad at memory position 0.
            calldatacopy(0, 0, calldatasize())

            // Call the implementation.
            // out and outsize are 0 because we don't know the size yet.
            let result := delegatecall(gas(), implementation, 0, calldatasize(), 0, 0)

            // Copy the returned data.
            returndatacopy(0, 0, returndatasize())

            switch result
            // delegatecall returns 0 on error.
            case 0 {
                revert(0, returndatasize())
            }
            default {
                return(0, returndatasize())
            }
        }
    }

    /**
     * @dev This is a virtual function that should be overriden so it returns the address to which the fallback function
     * and {_fallback} should delegate.
     */
    function _implementation() internal view virtual returns (address);

    /**
     * @dev Delegates the current call to the address returned by `_implementation()`.
     *
     * This function does not return to its internall call site, it will return directly to the external caller.
     */
    function _fallback() internal virtual {
        _beforeFallback();
        _delegate(_implementation());
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if no other
     * function in the contract matches the call data.
     */
    fallback() external payable virtual {
        _fallback();
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if call data
     * is empty.
     */
    receive() external payable virtual {
        _fallback();
    }

    /**
     * @dev Hook that is called before falling back to the implementation. Can happen as part of a manual `_fallback`
     * call, or as part of the Solidity `fallback` or `receive` functions.
     *
     * If overriden should call `super._beforeFallback()`.
     */
    function _beforeFallback() internal virtual {}
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/ERC1967/ERC1967Upgrade.sol)

pragma solidity ^0.8.2;

import "../beacon/IBeacon.sol";
import "../../utils/Address.sol";
import "../../utils/StorageSlot.sol";

/**
 * @dev This abstract contract provides getters and event emitting update functions for
 * https://eips.ethereum.org/EIPS/eip-1967[EIP1967] slots.
 *
 * _Available since v4.1._
 *
 * @custom:oz-upgrades-unsafe-allow delegatecall
 */
abstract contract ERC1967Upgrade {
    // This is the keccak-256 hash of "eip1967.proxy.rollback" subtracted by 1
    bytes32 private constant _ROLLBACK_SLOT = 0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;

    /**
     * @dev Storage slot with the address of the current implementation.
     * This is the keccak-256 hash of "eip1967.proxy.implementation" subtracted by 1, and is
     * validated in the constructor.
     */
    bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

    /**
     * @dev Emitted when the implementation is upgraded.
     */
    event Upgraded(address indexed implementation);

    /**
     * @dev Returns the current implementation address.
     */
    function _getImplementation() internal view returns (address) {
        return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
    }

    /**
     * @dev Stores a new address in the EIP1967 implementation slot.
     */
    function _setImplementation(address newImplementation) private {
        require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
        StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
    }

    /**
     * @dev Perform implementation upgrade
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeTo(address newImplementation) internal {
        _setImplementation(newImplementation);
        emit Upgraded(newImplementation);
    }

    /**
     * @dev Perform implementation upgrade with additional setup call.
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeToAndCall(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        _upgradeTo(newImplementation);
        if (data.length > 0 || forceCall) {
            Address.functionDelegateCall(newImplementation, data);
        }
    }

    /**
     * @dev Perform implementation upgrade with security checks for UUPS proxies, and additional setup call.
     *
     * Emits an {Upgraded} event.
     */
    function _upgradeToAndCallSecure(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        address oldImplementation = _getImplementation();

        // Initial upgrade and setup call
        _setImplementation(newImplementation);
        if (data.length > 0 || forceCall) {
            Address.functionDelegateCall(newImplementation, data);
        }

        // Perform rollback test if not already in progress
        StorageSlot.BooleanSlot storage rollbackTesting = StorageSlot.getBooleanSlot(_ROLLBACK_SLOT);
        if (!rollbackTesting.value) {
            // Trigger rollback using upgradeTo from the new implementation
            rollbackTesting.value = true;
            Address.functionDelegateCall(
                newImplementation,
                abi.encodeWithSignature("upgradeTo(address)", oldImplementation)
            );
            rollbackTesting.value = false;
            // Check rollback was effective
            require(oldImplementation == _getImplementation(), "ERC1967Upgrade: upgrade breaks further upgrades");
            // Finally reset to the new implementation and log the upgrade
            _upgradeTo(newImplementation);
        }
    }

    /**
     * @dev Storage slot with the admin of the contract.
     * This is the keccak-256 hash of "eip1967.proxy.admin" subtracted by 1, and is
     * validated in the constructor.
     */
    bytes32 internal constant _ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;

    /**
     * @dev Emitted when the admin account has changed.
     */
    event AdminChanged(address previousAdmin, address newAdmin);

    /**
     * @dev Returns the current admin.
     */
    function _getAdmin() internal view returns (address) {
        return StorageSlot.getAddressSlot(_ADMIN_SLOT).value;
    }

    /**
     * @dev Stores a new address in the EIP1967 admin slot.
     */
    function _setAdmin(address newAdmin) private {
        require(newAdmin != address(0), "ERC1967: new admin is the zero address");
        StorageSlot.getAddressSlot(_ADMIN_SLOT).value = newAdmin;
    }

    /**
     * @dev Changes the admin of the proxy.
     *
     * Emits an {AdminChanged} event.
     */
    function _changeAdmin(address newAdmin) internal {
        emit AdminChanged(_getAdmin(), newAdmin);
        _setAdmin(newAdmin);
    }

    /**
     * @dev The storage slot of the UpgradeableBeacon contract which defines the implementation for this proxy.
     * This is bytes32(uint256(keccak256('eip1967.proxy.beacon')) - 1)) and is validated in the constructor.
     */
    bytes32 internal constant _BEACON_SLOT = 0xa3f0ad74e5423aebfd80d3ef4346578335a9a72aeaee59ff6cb3582b35133d50;

    /**
     * @dev Emitted when the beacon is upgraded.
     */
    event BeaconUpgraded(address indexed beacon);

    /**
     * @dev Returns the current beacon.
     */
    function _getBeacon() internal view returns (address) {
        return StorageSlot.getAddressSlot(_BEACON_SLOT).value;
    }

    /**
     * @dev Stores a new beacon in the EIP1967 beacon slot.
     */
    function _setBeacon(address newBeacon) private {
        require(Address.isContract(newBeacon), "ERC1967: new beacon is not a contract");
        require(
            Address.isContract(IBeacon(newBeacon).implementation()),
            "ERC1967: beacon implementation is not a contract"
        );
        StorageSlot.getAddressSlot(_BEACON_SLOT).value = newBeacon;
    }

    /**
     * @dev Perform beacon upgrade with additional setup call. Note: This upgrades the address of the beacon, it does
     * not upgrade the implementation contained in the beacon (see {UpgradeableBeacon-_setImplementation} for that).
     *
     * Emits a {BeaconUpgraded} event.
     */
    function _upgradeBeaconToAndCall(
        address newBeacon,
        bytes memory data,
        bool forceCall
    ) internal {
        _setBeacon(newBeacon);
        emit BeaconUpgraded(newBeacon);
        if (data.length > 0 || forceCall) {
            Address.functionDelegateCall(IBeacon(newBeacon).implementation(), data);
        }
    }
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (proxy/beacon/IBeacon.sol)

pragma solidity ^0.8.0;

/**
 * @dev This is the interface that {BeaconProxy} expects of its beacon.
 */
interface IBeacon {
    /**
     * @dev Must return an address that can be used as a delegate call target.
     *
     * {BeaconProxy} will check that this address is a contract.
     */
    function implementation() external view returns (address);
}
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Address.sol)

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 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
// OpenZeppelin Contracts v4.4.1 (utils/StorageSlot.sol)

pragma solidity ^0.8.0;

/**
 * @dev Library for reading and writing primitive types to specific storage slots.
 *
 * Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts.
 * This library helps with reading and writing to such slots without the need for inline assembly.
 *
 * The functions in this library return Slot structs that contain a `value` member that can be used to read or write.
 *
 * Example usage to set ERC1967 implementation slot:
 * ```
 * contract ERC1967 {
 *     bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
 *
 *     function _getImplementation() internal view returns (address) {
 *         return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
 *     }
 *
 *     function _setImplementation(address newImplementation) internal {
 *         require(Address.isContract(newImplementation), "ERC1967: new implementation is not a contract");
 *         StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
 *     }
 * }
 * ```
 *
 * _Available since v4.1 for `address`, `bool`, `bytes32`, and `uint256`._
 */
library StorageSlot {
    struct AddressSlot {
        address value;
    }

    struct BooleanSlot {
        bool value;
    }

    struct Bytes32Slot {
        bytes32 value;
    }

    struct Uint256Slot {
        uint256 value;
    }

    /**
     * @dev Returns an `AddressSlot` with member `value` located at `slot`.
     */
    function getAddressSlot(bytes32 slot) internal pure returns (AddressSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `BooleanSlot` with member `value` located at `slot`.
     */
    function getBooleanSlot(bytes32 slot) internal pure returns (BooleanSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `Bytes32Slot` with member `value` located at `slot`.
     */
    function getBytes32Slot(bytes32 slot) internal pure returns (Bytes32Slot storage r) {
        assembly {
            r.slot := slot
        }
    }

    /**
     * @dev Returns an `Uint256Slot` with member `value` located at `slot`.
     */
    function getUint256Slot(bytes32 slot) internal pure returns (Uint256Slot storage r) {
        assembly {
            r.slot := slot
        }
    }
}
 <