// File: src/loan/terms/simple/loan/PWNSimpleLoan.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "MultiToken/MultiToken.sol";

import "@pwn/config/PWNConfig.sol";
import "@pwn/hub/PWNHub.sol";
import "@pwn/hub/PWNHubTags.sol";
import "@pwn/loan/lib/PWNFeeCalculator.sol";
import "@pwn/loan/terms/PWNLOANTerms.sol";
import "@pwn/loan/terms/simple/factory/PWNSimpleLoanTermsFactory.sol";
import "@pwn/loan/token/IERC5646.sol";
import "@pwn/loan/token/PWNLOAN.sol";
import "@pwn/loan/PWNVault.sol";
import "@pwn/PWNErrors.sol";


/**
 * @title PWN Simple Loan
 * @notice Contract managing a simple loan in PWN protocol.
 * @dev Acts as a vault for every loan created by this contract.
 */
contract PWNSimpleLoan is PWNVault, IERC5646, IPWNLoanMetadataProvider {

    string internal constant VERSION = "1.1";
    uint256 public constant MAX_EXPIRATION_EXTENSION = 2_592_000; // 30 days

    /*----------------------------------------------------------*|
    |*  # VARIABLES & CONSTANTS DEFINITIONS                     *|
    |*----------------------------------------------------------*/

    PWNHub immutable internal hub;
    PWNLOAN immutable internal loanToken;
    PWNConfig immutable internal config;

    /**
     * @notice Struct defining a simple loan.
     * @param status 0 == none/dead || 2 == running/accepted offer/accepted request || 3 == paid back || 4 == expired.
     * @param borrower Address of a borrower.
     * @param expiration Unix timestamp (in seconds) setting up a default date.
     * @param loanAssetAddress Address of an asset used as a loan credit.
     * @param loanRepayAmount Amount of a loan asset to be paid back.
     * @param collateral Asset used as a loan collateral. For a definition see { MultiToken dependency lib }.
     */
    struct LOAN {
        uint8 status;
        address borrower;
        uint40 expiration;
        address loanAssetAddress;
        uint256 loanRepayAmount;
        MultiToken.Asset collateral;
    }

    /**
     * Mapping of all LOAN data by loan id.
     */
    mapping (uint256 => LOAN) private LOANs;


    /*----------------------------------------------------------*|
    |*  # EVENTS & ERRORS DEFINITIONS                           *|
    |*----------------------------------------------------------*/

    /**
     * @dev Emitted when a new loan in created.
     */
    event LOANCreated(uint256 indexed loanId, PWNLOANTerms.Simple terms, bytes32 indexed factoryDataHash, address indexed factoryAddress);

    /**
     * @dev Emitted when a loan is paid back.
     */
    event LOANPaidBack(uint256 indexed loanId);

    /**
     * @dev Emitted when a repaid or defaulted loan is claimed.
     */
    event LOANClaimed(uint256 indexed loanId, bool indexed defaulted);

    /**
     * @dev Emitted when a LOAN token holder extends loan expiration date.
     */
    event LOANExpirationDateExtended(uint256 indexed loanId, uint40 extendedExpirationDate);


    /*----------------------------------------------------------*|
    |*  # CONSTRUCTOR                                           *|
    |*----------------------------------------------------------*/

    constructor(address _hub, address _loanToken, address _config) {
        hub = PWNHub(_hub);
        loanToken = PWNLOAN(_loanToken);
        config = PWNConfig(_config);
    }


    /*----------------------------------------------------------*|
    |*  # CREATE LOAN                                           *|
    |*----------------------------------------------------------*/

    /**
     * @notice Create a new loan by minting LOAN token for lender, transferring loan asset to a borrower and a collateral to a vault.
     * @dev The function assumes a prior token approval to a contract address or signed permits.
     * @param loanTermsFactoryContract Address of a loan terms factory contract. Need to have `SIMPLE_LOAN_TERMS_FACTORY` tag in PWN Hub.
     * @param loanTermsFactoryData Encoded data for a loan terms factory.
     * @param signature Signed loan factory data. Could be empty if an offer / request has been made via on-chain transaction.
     * @param loanAssetPermit Permit data for a loan asset signed by a lender.
     * @param collateralPermit Permit data for a collateral signed by a borrower.
     * @return loanId Id of a newly minted LOAN token.
     */
    function createLOAN(
        address loanTermsFactoryContract,
        bytes calldata loanTermsFactoryData,
        bytes calldata signature,
        bytes calldata loanAssetPermit,
        bytes calldata collateralPermit
    ) external returns (uint256 loanId) {
        // Check that loan terms factory contract is tagged in PWNHub
        if (hub.hasTag(loanTermsFactoryContract, PWNHubTags.SIMPLE_LOAN_TERMS_FACTORY) == false)
            revert CallerMissingHubTag(PWNHubTags.SIMPLE_LOAN_TERMS_FACTORY);

        // Build PWNLOANTerms.Simple by loan factory
        (PWNLOANTerms.Simple memory loanTerms, bytes32 factoryDataHash) = PWNSimpleLoanTermsFactory(loanTermsFactoryContract).createLOANTerms({
            caller: msg.sender,
            factoryData: loanTermsFactoryData,
            signature: signature
        });

        // Check loan asset validity
        if (MultiToken.isValid(loanTerms.asset) == false)
            revert InvalidLoanAsset();

        // Check collateral validity
        if (MultiToken.isValid(loanTerms.collateral) == false)
            revert InvalidCollateralAsset();

        // Mint LOAN token for lender
        loanId = loanToken.mint(loanTerms.lender);

        // Store loan data under loan id
        LOAN storage loan = LOANs[loanId];
        loan.status = 2;
        loan.borrower = loanTerms.borrower;
        loan.expiration = loanTerms.expiration;
        loan.loanAssetAddress = loanTerms.asset.assetAddress;
        loan.loanRepayAmount = loanTerms.loanRepayAmount;
        loan.collateral = loanTerms.collateral;

        emit LOANCreated(loanId, loanTerms, factoryDataHash, loanTermsFactoryContract);

        // Transfer collateral to Vault
        _permit(loanTerms.collateral, loanTerms.borrower, collateralPermit);
        _pull(loanTerms.collateral, loanTerms.borrower);

        // Permit spending if permit data provided
        _permit(loanTerms.asset, loanTerms.lender, loanAssetPermit);

        uint16 fee = config.fee();
        if (fee > 0) {
            // Compute fee size
            (uint256 feeAmount, uint256 newLoanAmount) = PWNFeeCalculator.calculateFeeAmount(fee, loanTerms.asset.amount);

            if (feeAmount > 0) {
                // Transfer fee amount to fee collector
                loanTerms.asset.amount = feeAmount;
                _pushFrom(loanTerms.asset, loanTerms.lender, config.feeCollector());

                // Set new loan amount value
                loanTerms.asset.amount = newLoanAmount;
            }
        }

        // Transfer loan asset to borrower
        _pushFrom(loanTerms.asset, loanTerms.lender, loanTerms.borrower);
    }


    /*----------------------------------------------------------*|
    |*  # REPAY LOAN                                            *|
    |*----------------------------------------------------------*/

    /**
     * @notice Repay running loan.
     * @dev Any address can repay a running loan, but a collateral will be transferred to a borrower address associated with the loan.
     *      Repay will transfer a loan asset to a vault, waiting on a LOAN token holder to claim it.
     *      The function assumes a prior token approval to a contract address or a signed  permit.
     * @param loanId Id of a loan that is being repaid.
     * @param loanAssetPermit Permit data for a loan asset signed by a borrower.
     */
    function repayLOAN(
        uint256 loanId,
        bytes calldata loanAssetPermit
    ) external {
        LOAN storage loan = LOANs[loanId];
        uint8 status = loan.status;

        // Check that loan is not from a different loan contract
        if (status == 0)
            revert NonExistingLoan();
        // Check that loan is running
        else if (status != 2)
            revert InvalidLoanStatus(status);

        // Check that loan is not expired
        if (loan.expiration <= block.timestamp)
            revert LoanDefaulted(loan.expiration);

        // Move loan to repaid state
        loan.status = 3;

        // Transfer repaid amount of loan asset to Vault
        MultiToken.Asset memory repayLoanAsset = MultiToken.Asset({
            category: MultiToken.Category.ERC20,
            assetAddress: loan.loanAssetAddress,
            id: 0,
            amount: loan.loanRepayAmount
        });

        _permit(repayLoanAsset, msg.sender, loanAssetPermit);
        _pull(repayLoanAsset, msg.sender);

        // Transfer collateral back to borrower
        _push(loan.collateral, loan.borrower);

        emit LOANPaidBack(loanId);
    }


    /*----------------------------------------------------------*|
    |*  # CLAIM LOAN                                            *|
    |*----------------------------------------------------------*/

    /**
     * @notice Claim a repaid or defaulted loan.
     * @dev Only a LOAN token holder can claim a repaid or defaulted loan.
     *      Claim will transfer the repaid loan asset or collateral to a LOAN token holder address and burn the LOAN token.
     * @param loanId Id of a loan that is being claimed.
     */
    function claimLOAN(uint256 loanId) external {
        LOAN storage loan = LOANs[loanId];

        // Check that caller is LOAN token holder
        if (loanToken.ownerOf(loanId) != msg.sender)
            revert CallerNotLOANTokenHolder();

        if (loan.status == 0) {
            revert NonExistingLoan();
        }
        // Loan has been paid back
        else if (loan.status == 3) {
            MultiToken.Asset memory loanAsset = MultiToken.Asset({
                category: MultiToken.Category.ERC20,
                assetAddress: loan.loanAssetAddress,
                id: 0,
                amount: loan.loanRepayAmount
            });

            // Delete loan data & burn LOAN token before calling safe transfer
            _deleteLoan(loanId);

            // Transfer repaid loan to lender
            _push(loanAsset, msg.sender);

            emit LOANClaimed(loanId, false);
        }
        // Loan is running but expired
        else if (loan.status == 2 && loan.expiration <= block.timestamp) {
             MultiToken.Asset memory collateral = loan.collateral;

            // Delete loan data & burn LOAN token before calling safe transfer
            _deleteLoan(loanId);

            // Transfer collateral to lender
            _push(collateral, msg.sender);

            emit LOANClaimed(loanId, true);
        }
        // Loan is in wrong state or from a different loan contract
        else {
            revert InvalidLoanStatus(loan.status);
        }
    }

    function _deleteLoan(uint256 loanId) private {
        loanToken.burn(loanId);
        delete LOANs[loanId];
    }


    /*----------------------------------------------------------*|
    |*  # EXTEND LOAN EXPIRATION DATE                           *|
    |*----------------------------------------------------------*/

    /**
     * @notice Enable lender to extend loans expiration date.
     * @dev Only LOAN token holder can call this function.
     *      Extending the expiration date of a repaid loan is allowed, but considered a lender mistake.
     *      The extended expiration date has to be in the future, be later than the current expiration date, and cannot be extending the date by more than `MAX_EXPIRATION_EXTENSION`.
     * @param loanId Id of a LOAN to extend its expiration date.
     * @param extendedExpirationDate New LOAN expiration date.
     */
    function extendLOANExpirationDate(uint256 loanId, uint40 extendedExpirationDate) external {
        // Check that caller is LOAN token holder
        // This prevents from extending non-existing loans
        if (loanToken.ownerOf(loanId) != msg.sender)
            revert CallerNotLOANTokenHolder();

        LOAN storage loan = LOANs[loanId];

        // Check extended expiration date
        if (extendedExpirationDate > uint40(block.timestamp + MAX_EXPIRATION_EXTENSION)) // to protect lender
            revert InvalidExtendedExpirationDate();
        if (extendedExpirationDate <= uint40(block.timestamp)) // have to extend expiration futher in time
            revert InvalidExtendedExpirationDate();
        if (extendedExpirationDate <= loan.expiration) // have to be later than current expiration date
            revert InvalidExtendedExpirationDate();

        // Extend expiration date
        loan.expiration = extendedExpirationDate;

        emit LOANExpirationDateExtended(loanId, extendedExpirationDate);
    }


    /*----------------------------------------------------------*|
    |*  # GET LOAN                                              *|
    |*----------------------------------------------------------*/

    /**
     * @notice Return a LOAN data struct associated with a loan id.
     * @param loanId Id of a loan in question.
     * @return loan LOAN data struct or empty struct if the LOAN doesn't exist.
     */
    function getLOAN(uint256 loanId) external view returns (LOAN memory loan) {
        loan = LOANs[loanId];
        loan.status = _getLOANStatus(loanId);
    }

    function _getLOANStatus(uint256 loanId) private view returns (uint8) {
        LOAN storage loan = LOANs[loanId];
        return (loan.status == 2 && loan.expiration <= block.timestamp) ? 4 : loan.status;
    }


    /*----------------------------------------------------------*|
    |*  # IPWNLoanMetadataProvider                              *|
    |*----------------------------------------------------------*/

    /**
     * @notice See { IPWNLoanMetadataProvider.sol }.
     */
    function loanMetadataUri() override external view returns (string memory) {
        return config.loanMetadataUri(address(this));
    }


    /*----------------------------------------------------------*|
    |*  # ERC5646                                               *|
    |*----------------------------------------------------------*/

    /**
     * @dev See {IERC5646-getStateFingerprint}.
     */
    function getStateFingerprint(uint256 tokenId) external view virtual override returns (bytes32) {
        LOAN storage loan = LOANs[tokenId];

        if (loan.status == 0)
            return bytes32(0);

        // The only mutable state properties are:
        // - status, expiration
        // Status is updated for expired loans based on block.timestamp.
        // Others don't have to be part of the state fingerprint as it does not act as a token identification.
        return keccak256(abi.encode(
            _getLOANStatus(tokenId),
            loan.expiration
        ));
    }

}

// File: lib/MultiToken/src/MultiToken.sol



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

import "@openzeppelin/interfaces/IERC20.sol";
import "@openzeppelin/interfaces/IERC721.sol";
import "@openzeppelin/interfaces/IERC1155.sol";
import "@openzeppelin/token/ERC20/extensions/draft-IERC20Permit.sol";
import "@openzeppelin/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/utils/introspection/ERC165Checker.sol";

import "@MT/interfaces/ICryptoKitties.sol";


library MultiToken {
    using ERC165Checker for address;
    using SafeERC20 for IERC20;

    bytes4 public constant ERC20_INTERFACE_ID = 0x36372b07;
    bytes4 public constant ERC721_INTERFACE_ID = 0x80ac58cd;
    bytes4 public constant ERC1155_INTERFACE_ID = 0xd9b67a26;
    bytes4 public constant CRYPTO_KITTIES_INTERFACE_ID = 0x9a20483d;

    /**
     * @title Category
     * @dev Enum representation Asset category.
     */
    enum Category {
        ERC20,
        ERC721,
        ERC1155,
        CryptoKitties
    }

    /**
     * @title Asset
     * @param category Corresponding asset category.
     * @param assetAddress Address of the token contract defining the asset.
     * @param id TokenID of an NFT or 0.
     * @param amount Amount of fungible tokens or 0 -> 1.
     */
    struct Asset {
        Category category;
        address assetAddress;
        uint256 id;
        uint256 amount;
    }


    /*----------------------------------------------------------*|
    |*  # TRANSFER ASSET                                        *|
    |*----------------------------------------------------------*/

    /**
     * transferAssetFrom
     * @dev Wrapping function for `transferFrom` calls on various token interfaces.
     *      If `source` is `address(this)`, function `transfer` is called instead of `transferFrom` for ERC20 category.
     * @param asset Struct defining all necessary context of a token.
     * @param source Account/address that provided the allowance.
     * @param dest Destination address.
     */
    function transferAssetFrom(Asset memory asset, address source, address dest) internal {
        _transferAssetFrom(asset, source, dest, false);
    }

    /**
     * safeTransferAssetFrom
     * @dev Wrapping function for `safeTransferFrom` calls on various token interfaces.
     *      If `source` is `address(this)`, function `transfer` is called instead of `transferFrom` for ERC20 category.
     * @param asset Struct defining all necessary context of a token.
     * @param source Account/address that provided the allowance.
     * @param dest Destination address.
     */
    function safeTransferAssetFrom(Asset memory asset, address source, address dest) internal {
        _transferAssetFrom(asset, source, dest, true);
    }

    function _transferAssetFrom(Asset memory asset, address source, address dest, bool isSafe) private {
        if (asset.category == Category.ERC20) {
            if (source == address(this))
                IERC20(asset.assetAddress).safeTransfer(dest, asset.amount);
            else
                IERC20(asset.assetAddress).safeTransferFrom(source, dest, asset.amount);

        } else if (asset.category == Category.ERC721) {
            if (!isSafe)
                IERC721(asset.assetAddress).transferFrom(source, dest, asset.id);
            else
                IERC721(asset.assetAddress).safeTransferFrom(source, dest, asset.id, "");

        } else if (asset.category == Category.ERC1155) {
            IERC1155(asset.assetAddress).safeTransferFrom(source, dest, asset.id, asset.amount == 0 ? 1 : asset.amount, "");

        } else if (asset.category == Category.CryptoKitties) {
            if (source == address(this))
                ICryptoKitties(asset.assetAddress).transfer(dest, asset.id);
            else
                ICryptoKitties(asset.assetAddress).transferFrom(source, dest, asset.id);

        } else {
            revert("MultiToken: Unsupported category");
        }
    }

    /**
     * getTransferAmount
     * @dev Get amount of asset that would be transferred.
     *      NFTs (ERC721, CryptoKitties & ERC1155 with amount 0) with return 1.
     *      Fungible tokens will return its amount (ERC20 with 0 amount is valid state).
     *      In combination with `MultiToken.balanceOf`, `getTransferAmount` can be used to check successful asset transfer.
     * @param asset Struct defining all necessary context of a token.
     * @return Number of tokens that would be transferred of the asset.
     */
    function getTransferAmount(Asset memory asset) internal pure returns (uint256) {
        if (asset.category == Category.ERC20)
            return asset.amount;
        else if (asset.category == Category.ERC1155 && asset.amount > 0)
            return asset.amount;
        else // Return 1 for ERC721, CryptoKitties and ERC1155 used as NFTs (amount = 0)
            return 1;
    }


    /*----------------------------------------------------------*|
    |*  # TRANSFER ASSET CALLDATA                               *|
    |*----------------------------------------------------------*/

    /**
     * transferAssetFromCalldata
     * @dev Wrapping function for `transferFrom` calladata on various token interfaces.
     *      If `fromSender` is true, function `transfer` is returned instead of `transferFrom` for ERC20 category.
     * @param asset Struct defining all necessary context of a token.
     * @param source Account/address that provided the allowance.
     * @param dest Destination address.
     */
    function transferAssetFromCalldata(Asset memory asset, address source, address dest, bool fromSender) pure internal returns (bytes memory) {
        return _transferAssetFromCalldata(asset, source, dest, fromSender, false);
    }

    /**
     * safeTransferAssetFromCalldata
     * @dev Wrapping function for `safeTransferFrom` calladata on various token interfaces.
     *      If `fromSender` is true, function `transfer` is returned instead of `transferFrom` for ERC20 category.
     * @param asset Struct defining all necessary context of a token.
     * @param source Account/address that provided the allowance.
     * @param dest Destination address.
     */
    function safeTransferAssetFromCalldata(Asset memory asset, address source, address dest, bool fromSender) pure internal returns (bytes memory) {
        return _transferAssetFromCalldata(asset, source, dest, fromSender, true);
    }

    function _transferAssetFromCalldata(Asset memory asset, address source, address dest, bool fromSender, bool isSafe) pure private returns (bytes memory) {
        if (asset.category == Category.ERC20) {
            if (fromSender) {
                return abi.encodeWithSignature(
                    "transfer(address,uint256)", dest, asset.amount
                );
            } else {
                return abi.encodeWithSignature(
                    "transferFrom(address,address,uint256)", source, dest, asset.amount
                );
            }
        } else if (asset.category == Category.ERC721) {
            if (!isSafe) {
                return abi.encodeWithSignature(
                    "transferFrom(address,address,uint256)", source, dest, asset.id
                );
            } else {
                return abi.encodeWithSignature(
                    "safeTransferFrom(address,address,uint256,bytes)", source, dest, asset.id, ""
                );
            }

        } else if (asset.category == Category.ERC1155) {
            return abi.encodeWithSignature(
                "safeTransferFrom(address,address,uint256,uint256,bytes)", source, dest, asset.id, asset.amount == 0 ? 1 : asset.amount, ""
            );

        } else if (asset.category == Category.CryptoKitties) {
            if (fromSender) {
                return abi.encodeWithSignature(
                    "transfer(address,uint256)", dest, asset.id
                );
            } else {
                return abi.encodeWithSignature(
                    "transferFrom(address,address,uint256)", source, dest, asset.id
                );
            }

        } else {
            revert("MultiToken: Unsupported category");
        }
    }


    /*----------------------------------------------------------*|
    |*  # PERMIT                                                *|
    |*----------------------------------------------------------*/

    /**
     * permit
     * @dev Wrapping function for granting approval via permit signature.
     * @param asset Struct defining all necessary context of a token.
     * @param owner Account/address that signed the permit.
     * @param spender Account/address that would be granted approval to `asset`.
     * @param permitData Data about permit deadline (uint256) and permit signature (64/65 bytes).
     *                   Deadline and signature should be pack encoded together.
     *                   Signature can be standard (65 bytes) or compact (64 bytes) defined in EIP-2098.
     */
    function permit(Asset memory asset, address owner, address spender, bytes memory permitData) internal {
        if (asset.category == Category.ERC20) {

            // Parse deadline and permit signature parameters
            uint256 deadline;
            bytes32 r;
            bytes32 s;
            uint8 v;

            // Parsing signature parameters used from OpenZeppelins ECDSA library
            // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/83277ff916ac4f58fec072b8f28a252c1245c2f1/contracts/utils/cryptography/ECDSA.sol

            // Deadline (32 bytes) + standard signature data (65 bytes) -> 97 bytes
            if (permitData.length == 97) {
                assembly {
                    deadline := mload(add(permitData, 0x20))
                    r := mload(add(permitData, 0x40))
                    s := mload(add(permitData, 0x60))
                    v := byte(0, mload(add(permitData, 0x80)))
                }
            }
            // Deadline (32 bytes) + compact signature data (64 bytes) -> 96 bytes
            else if (permitData.length == 96) {
                bytes32 vs;

                assembly {
                    deadline := mload(add(permitData, 0x20))
                    r := mload(add(permitData, 0x40))
                    vs := mload(add(permitData, 0x60))
                }

                s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
                v = uint8((uint256(vs) >> 255) + 27);
            } else {
                revert("MultiToken::Permit: Invalid permit length");
            }

            // Call permit with parsed parameters
            IERC20Permit(asset.assetAddress).permit(owner, spender, asset.amount, deadline, v, r, s);

        } else {
            // Currently supporting only ERC20 signed approvals via ERC2612
            revert("MultiToken::Permit: Unsupported category");
        }
    }


    /*----------------------------------------------------------*|
    |*  # BALANCE OF                                            *|
    |*----------------------------------------------------------*/

    /**
     * balanceOf
     * @dev Wrapping function for checking balances on various token interfaces.
     * @param asset Struct defining all necessary context of a token.
     * @param target Target address to be checked.
     */
    function balanceOf(Asset memory asset, address target) internal view returns (uint256) {
        if (asset.category == Category.ERC20) {
            return IERC20(asset.assetAddress).balanceOf(target);

        } else if (asset.category == Category.ERC721) {
            return IERC721(asset.assetAddress).ownerOf(asset.id) == target ? 1 : 0;

        } else if (asset.category == Category.ERC1155) {
            return IERC1155(asset.assetAddress).balanceOf(target, asset.id);

        } else if (asset.category == Category.CryptoKitties) {
            return ICryptoKitties(asset.assetAddress).ownerOf(asset.id) == target ? 1 : 0;

        } else {
            revert("MultiToken: Unsupported category");
        }
    }


    /*----------------------------------------------------------*|
    |*  # APPROVE ASSET                                         *|
    |*----------------------------------------------------------*/

    /**
     * approveAsset
     * @dev Wrapping function for `approve` calls on various token interfaces.
     *      By using `safeApprove` for ERC20, caller can set allowance to 0 or from 0.
     *      Cannot set non-zero value if allowance is also non-zero.
     * @param asset Struct defining all necessary context of a token.
     * @param target Account/address that would be granted approval to `asset`.
     */
    function approveAsset(Asset memory asset, address target) internal {
        if (asset.category == Category.ERC20) {
            IERC20(asset.assetAddress).safeApprove(target, asset.amount);

        } else if (asset.category == Category.ERC721) {
            IERC721(asset.assetAddress).approve(target, asset.id);

        } else if (asset.category == Category.ERC1155) {
            IERC1155(asset.assetAddress).setApprovalForAll(target, true);

        } else if (asset.category == Category.CryptoKitties) {
            ICryptoKitties(asset.assetAddress).approve(target, asset.id);

        } else {
            revert("MultiToken: Unsupported category");
        }
    }


    /*----------------------------------------------------------*|
    |*  # ASSET CHECKS                                          *|
    |*----------------------------------------------------------*/

    /**
     * isValid
     * @dev Checks that provided asset is contract, has correct format and stated category.
     *      Fungible tokens (ERC20) have to have id = 0.
     *      NFT (ERC721, CryptoKitties) tokens have to have amount = 0.
     *      Correct asset category is determined via ERC165.
     *      The check assumes, that asset contract implements only one token standard at a time.
     * @param asset Asset that is examined.
     * @return True if assets amount and id is valid in stated category.
     */
    function isValid(Asset memory asset) internal view returns (bool) {
        if (asset.category == Category.ERC20) {
            // Check format
            if (asset.id != 0)
                return false;

            // ERC20 has optional ERC165 implementation
            if (asset.assetAddress.supportsERC165()) {
                // If ERC20 implements ERC165, it has to return true for its interface id
                return asset.assetAddress.supportsERC165InterfaceUnchecked(ERC20_INTERFACE_ID);

            } else {
                // In case token doesn't implement ERC165, its safe to assume that provided category is correct,
                // because any other category have to implement ERC165.

                // Check that asset address is contract
                // Tip: asset address will return code length 0, if this code is called from the asset constructor
                return asset.assetAddress.code.length > 0;
            }

        } else if (asset.category == Category.ERC721) {
            // Check format
            if (asset.amount != 0)
                return false;

            // Check it's ERC721 via ERC165
            return asset.assetAddress.supportsInterface(ERC721_INTERFACE_ID);

        } else if (asset.category == Category.ERC1155) {
            // Check it's ERC1155 via ERC165
            return asset.assetAddress.supportsInterface(ERC1155_INTERFACE_ID);

        } else if (asset.category == Category.CryptoKitties) {
            // Check format
            if (asset.amount != 0)
                return false;

            // Check it's CryptoKitties via ERC165
            return asset.assetAddress.supportsInterface(CRYPTO_KITTIES_INTERFACE_ID);

        } else {
            revert("MultiToken: Unsupported category");
        }
    }

    /**
     * isSameAs
     * @dev Compare two assets, ignoring their amounts.
     * @param asset First asset to examine.
     * @param otherAsset Second asset to examine.
     * @return True if both structs represents the same asset.
     */
    function isSameAs(Asset memory asset, Asset memory otherAsset) internal pure returns (bool) {
        return
            asset.category == otherAsset.category &&
            asset.assetAddress == otherAsset.assetAddress &&
            asset.id == otherAsset.id;
    }
}

// File: src/config/PWNConfig.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "openzeppelin-contracts/contracts/access/Ownable2Step.sol";
import "openzeppelin-contracts/contracts/proxy/utils/Initializable.sol";

import "@pwn/PWNErrors.sol";


/**
 * @title PWN Config
 * @notice Contract holding configurable values of PWN protocol.
 * @dev Is intendet to be used as a proxy via `TransparentUpgradeableProxy`.
 */
contract PWNConfig is Ownable2Step, Initializable {

    string internal constant VERSION = "1.0";

    /*----------------------------------------------------------*|
    |*  # VARIABLES & CONSTANTS DEFINITIONS                     *|
    |*----------------------------------------------------------*/

    uint16 public constant MAX_FEE = 1000; // 10%

    /**
     * @notice Protocol fee value in basis points.
     * @dev Value of 100 is 1% fee.
     */
    uint16 public fee;

    /**
     * @notice Address that collects protocol fees.
     */
    address public feeCollector;

    /**
     * @notice Mapping of a loan contract address to LOAN token metadata uri.
     * @dev LOAN token minted by a loan contract will return metadata uri stored in this mapping.
     */
    mapping (address => string) public loanMetadataUri;


    /*----------------------------------------------------------*|
    |*  # EVENTS & ERRORS DEFINITIONS                           *|
    |*----------------------------------------------------------*/

    /**
     * @dev Emitted when new fee value is set.
     */
    event FeeUpdated(uint16 oldFee, uint16 newFee);

    /**
     * @dev Emitted when new fee collector address is set.
     */
    event FeeCollectorUpdated(address oldFeeCollector, address newFeeCollector);

    /**
     * @dev Emitted when new LOAN token metadata uri is set.
     */
    event LoanMetadataUriUpdated(address indexed loanContract, string newUri);


    /*----------------------------------------------------------*|
    |*  # CONSTRUCTOR                                           *|
    |*----------------------------------------------------------*/

    constructor() Ownable2Step() {

    }

    function initialize(address _owner, uint16 _fee, address _feeCollector) initializer external {
        require(_owner != address(0), "Owner is zero address");
        _transferOwnership(_owner);

        require(_feeCollector != address(0), "Fee collector is zero address");
        _setFeeCollector(_feeCollector);

        _setFee(_fee);
    }


    /*----------------------------------------------------------*|
    |*  # FEE MANAGEMENT                                        *|
    |*----------------------------------------------------------*/

    /**
     * @notice Set new protocol fee value.
     * @dev Only contract owner can call this function.
     * @param _fee New fee value in basis points. Value of 100 is 1% fee.
     */
    function setFee(uint16 _fee) external onlyOwner {
        _setFee(_fee);
    }

    function _setFee(uint16 _fee) private {
        if (_fee > MAX_FEE)
            revert InvalidFeeValue();

        uint16 oldFee = fee;
        fee = _fee;
        emit FeeUpdated(oldFee, _fee);
    }

    /**
     * @notice Set new fee collector address.
     * @dev Only contract owner can call this function.
     * @param _feeCollector New fee collector address.
     */
    function setFeeCollector(address _feeCollector) external onlyOwner {
        _setFeeCollector(_feeCollector);
    }

    function _setFeeCollector(address _feeCollector) private {
        if (_feeCollector == address(0))
            revert InvalidFeeCollector();

        address oldFeeCollector = feeCollector;
        feeCollector = _feeCollector;
        emit FeeCollectorUpdated(oldFeeCollector, _feeCollector);
    }


    /*----------------------------------------------------------*|
    |*  # LOAN METADATA MANAGEMENT                              *|
    |*----------------------------------------------------------*/

    /**
     * @notice Set a LOAN token metadata uri for a specific loan contract.
     * @param loanContract Address of a loan contract.
     * @param metadataUri New value of LOAN token metadata uri for given `loanContract`.
     */
    function setLoanMetadataUri(address loanContract, string memory metadataUri) external onlyOwner {
        loanMetadataUri[loanContract] = metadataUri;
        emit LoanMetadataUriUpdated(loanContract, metadataUri);
    }

}

// File: src/hub/PWNHub.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "openzeppelin-contracts/contracts/access/Ownable2Step.sol";

import "@pwn/PWNErrors.sol";


/**
 * @title PWN Hub
 * @notice Connects PWN contracts together into protocol via tags.
 */
contract PWNHub is Ownable2Step {

    /*----------------------------------------------------------*|
    |*  # VARIABLES & CONSTANTS DEFINITIONS                     *|
    |*----------------------------------------------------------*/

    /**
     * @dev Mapping of address tags. (contract address => tag => is tagged)
     */
    mapping (address => mapping (bytes32 => bool)) private tags;


    /*----------------------------------------------------------*|
    |*  # EVENTS & ERRORS DEFINITIONS                           *|
    |*----------------------------------------------------------*/

    /**
     * @dev Emitted when tag is set for an address.
     */
    event TagSet(address indexed _address, bytes32 indexed tag, bool hasTag);


    /*----------------------------------------------------------*|
    |*  # CONSTRUCTOR                                           *|
    |*----------------------------------------------------------*/

    constructor() Ownable2Step() {

    }


    /*----------------------------------------------------------*|
    |*  # TAG MANAGEMENT                                        *|
    |*----------------------------------------------------------*/

    /**
     * @notice Set tag to an address.
     * @dev Tag can be added or removed via this functions. Only callable by contract owner.
     * @param _address Address to which a tag is set.
     * @param tag Tag that is set to an `_address`.
     * @param _hasTag Bool value if tag is added or removed.
     */
    function setTag(address _address, bytes32 tag, bool _hasTag) public onlyOwner {
        tags[_address][tag] = _hasTag;
        emit TagSet(_address, tag, _hasTag);
    }

    /**
     * @notice Set list of tags to an address.
     * @dev Tags can be added or removed via this functions. Only callable by contract owner.
     * @param _addresses List of addresses to which tags are set.
     * @param _tags List of tags that are set to an `_address`.
     * @param _hasTag Bool value if tags are added or removed.
     */
    function setTags(address[] memory _addresses, bytes32[] memory _tags, bool _hasTag) external onlyOwner {
        if (_addresses.length != _tags.length)
            revert InvalidInputData();

        uint256 length = _tags.length;
        for (uint256 i; i < length;) {
            setTag(_addresses[i], _tags[i], _hasTag);
            unchecked { ++i; }
        }
    }


    /*----------------------------------------------------------*|
    |*  # TAG GETTER                                            *|
    |*----------------------------------------------------------*/

    /**
     * @dev Return if an address is associated with a tag.
     * @param _address Address that is examined for a `tag`.
     * @param tag Tag that should an `_address` be associated with.
     * @return True if given address has a tag.
     */
    function hasTag(address _address, bytes32 tag) external view returns (bool) {
        return tags[_address][tag];
    }

}

// File: src/hub/PWNHubTags.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

library PWNHubTags {

    string internal constant VERSION = "1.0";

    /// @dev Address can mint LOAN tokens and create LOANs via loan factory contracts.
    bytes32 internal constant ACTIVE_LOAN = keccak256("PWN_ACTIVE_LOAN");

    /// @dev Address can be used as a loan terms factory for creating simple loans.
    bytes32 internal constant SIMPLE_LOAN_TERMS_FACTORY = keccak256("PWN_SIMPLE_LOAN_TERMS_FACTORY");

    /// @dev Address can revoke loan request nonces.
    bytes32 internal constant LOAN_REQUEST = keccak256("PWN_LOAN_REQUEST");
    /// @dev Address can revoke loan offer nonces.
    bytes32 internal constant LOAN_OFFER = keccak256("PWN_LOAN_OFFER");

}

// File: src/loan/lib/PWNFeeCalculator.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;


/**
 * @title PWN Fee Calculator
 * @notice Library that calculates fee amount for given loan amount.
 */
library PWNFeeCalculator {

    string internal constant VERSION = "1.0";

    /**
     * @notice Compute fee amount.
     * @param fee Fee value in basis points. Value of 100 is 1% fee.
     * @param loanAmount Amount of an asset used as a loan credit.
     * @return feeAmount Amount of a loan asset that represents a protocol fee.
     * @return newLoanAmount New amount of a loan credit asset, after deducting protocol fee.
     */
    function calculateFeeAmount(uint16 fee, uint256 loanAmount) internal pure returns (uint256 feeAmount, uint256 newLoanAmount) {
        if (fee == 0)
            return (0, loanAmount);

        unchecked {
            if ((loanAmount * fee) / fee == loanAmount)
                feeAmount = loanAmount * uint256(fee) / 1e4;
            else
                feeAmount = loanAmount / 1e4 * uint256(fee);
        }
        newLoanAmount = loanAmount - feeAmount;
    }

}

// File: src/loan/terms/PWNLOANTerms.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "MultiToken/MultiToken.sol";


library PWNLOANTerms {

    /**
     * @notice Struct defining a simple loan terms.
     * @dev This struct is created by loan factories and never stored.
     * @param lender Address of a lender.
     * @param borrower Address of a borrower.
     * @param expiration Unix timestamp (in seconds) setting up a default date.
     * @param collateral Asset used as a loan collateral. For a definition see { MultiToken dependency lib }.
     * @param asset Asset used as a loan credit. For a definition see { MultiToken dependency lib }.
     * @param loanRepayAmount Amount of a loan asset to be paid back.
     */
    struct Simple {
        address lender;
        address borrower;
        uint40 expiration;
        MultiToken.Asset collateral;
        MultiToken.Asset asset;
        uint256 loanRepayAmount;
    }

}

// File: src/loan/terms/simple/factory/PWNSimpleLoanTermsFactory.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "@pwn/loan/terms/PWNLOANTerms.sol";


/**
 * @title PWN Simple Loan Terms Factory Interface
 * @notice Interface of a loan factory contract that builds a simple loan terms.
 */
abstract contract PWNSimpleLoanTermsFactory {

    uint32 public constant MIN_LOAN_DURATION = 600; // 10 min

    /**
     * @notice Build a simple loan terms from given data.
     * @dev This function should be called only by contracts working with simple loan terms.
     * @param caller Caller of a create loan function on a loan contract.
     * @param factoryData Encoded data for a loan terms factory.
     * @param signature Signed loan factory data.
     * @return loanTerms Simple loan terms struct created from a loan factory data.
     * @return factoryDataHash Hash of a loan offer / request that is signed by a lender / borrower. Used to uniquely identify a loan offer / request.
     */
    function createLOANTerms(
        address caller,
        bytes calldata factoryData,
        bytes calldata signature
    ) external virtual returns (PWNLOANTerms.Simple memory loanTerms, bytes32 factoryDataHash);

}

// File: src/loan/token/IERC5646.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

/**
 * @dev Interface of the ERC5646 standard, as defined in the https://eips.ethereum.org/EIPS/eip-5646.
 */
interface IERC5646 {

    /**
     * @notice Function to return current token state fingerprint.
     * @param tokenId Id of a token state in question.
     * @return Current token state fingerprint.
     */
    function getStateFingerprint(uint256 tokenId) external view returns (bytes32);

}

// File: src/loan/token/PWNLOAN.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "openzeppelin-contracts/contracts/token/ERC721/ERC721.sol";

import "@pwn/hub/PWNHubAccessControl.sol";
import "@pwn/loan/token/IERC5646.sol";
import "@pwn/loan/token/IPWNLoanMetadataProvider.sol";
import "@pwn/PWNErrors.sol";


/**
 * @title PWN LOAN token
 * @notice A LOAN token representing a loan in PWN protocol.
 * @dev Token doesn't hold any loan logic, just an address of a loan contract that minted the LOAN token.
 *      PWN LOAN token is shared between all loan contracts.
 */
contract PWNLOAN is PWNHubAccessControl, IERC5646, ERC721 {

    /*----------------------------------------------------------*|
    |*  # VARIABLES & CONSTANTS DEFINITIONS                     *|
    |*----------------------------------------------------------*/

    /**
     * @dev Last used LOAN id. First LOAN id is 1. This value is incremental.
     */
    uint256 public lastLoanId;

    /**
     * @dev Mapping of a LOAN id to a loan contract that minted the LOAN token.
     */
    mapping (uint256 => address) public loanContract;


    /*----------------------------------------------------------*|
    |*  # EVENTS DEFINITIONS                                    *|
    |*----------------------------------------------------------*/

    /**
     * @dev Emitted when a new LOAN token is minted.
     */
    event LOANMinted(uint256 indexed loanId, address indexed loanContract, address indexed owner);

    /**
     * @dev Emitted when a LOAN token is burned.
     */
    event LOANBurned(uint256 indexed loanId);


    /*----------------------------------------------------------*|
    |*  # CONSTRUCTOR                                           *|
    |*----------------------------------------------------------*/

    constructor(address hub) PWNHubAccessControl(hub) ERC721("PWN LOAN", "LOAN") {

    }


    /*----------------------------------------------------------*|
    |*  # TOKEN LIFECYCLE                                       *|
    |*----------------------------------------------------------*/

    /**
     * @notice Mint a new LOAN token.
     * @dev Only an address with associated `ACTIVE_LOAN` tag in PWN Hub can call this function.
     * @param owner Address of a LOAN token receiver.
     * @return loanId Id of a newly minted LOAN token.
     */
    function mint(address owner) external onlyActiveLoan returns (uint256 loanId) {
        loanId = ++lastLoanId;
        loanContract[loanId] = msg.sender;
        _mint(owner, loanId);
        emit LOANMinted(loanId, msg.sender, owner);
    }

    /**
     * @notice Burn a LOAN token.
     * @dev Any address that is associated with given loan id can call this function.
     *      It is enabled to let deprecated loan contracts repay and claim existing loans.
     * @param loanId Id of a LOAN token to be burned.
     */
    function burn(uint256 loanId) external {
        if (loanContract[loanId] != msg.sender)
            revert InvalidLoanContractCaller();

        delete loanContract[loanId];
        _burn(loanId);
        emit LOANBurned(loanId);
    }


    /*----------------------------------------------------------*|
    |*  # METADATA                                              *|
    |*----------------------------------------------------------*/

    /**
     * @notice Return a LOAN token metadata uri base on a loan contract that minted the token.
     * @param tokenId Id of a LOAN token.
     * @return Metadata uri for given token id (loan id).
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        _requireMinted(tokenId);

        return IPWNLoanMetadataProvider(loanContract[tokenId]).loanMetadataUri();
    }


    /*----------------------------------------------------------*|
    |*  # ERC5646                                               *|
    |*----------------------------------------------------------*/

    /**
     * @dev See {IERC5646-getStateFingerprint}.
     */
    function getStateFingerprint(uint256 tokenId) external view virtual override returns (bytes32) {
        address _loanContract = loanContract[tokenId];

        if (_loanContract == address(0))
            return bytes32(0);

        return IERC5646(_loanContract).getStateFingerprint(tokenId);
    }


    /*----------------------------------------------------------*|
    |*  # ERC165                                                *|
    |*----------------------------------------------------------*/

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return super.supportsInterface(interfaceId) ||
            interfaceId == type(IERC5646).interfaceId;
    }

}

// File: src/loan/PWNVault.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "MultiToken/MultiToken.sol";

import "openzeppelin-contracts/contracts/token/ERC721/IERC721Receiver.sol";
import "openzeppelin-contracts/contracts/token/ERC1155/IERC1155Receiver.sol";

import "@pwn/PWNErrors.sol";


/**
 * @title PWN Vault
 * @notice Base contract for transferring and managing collateral and loan assets in PWN protocol.
 * @dev Loan contracts inherits PWN Vault to act as a Vault for its loan type.
 */
abstract contract PWNVault is IERC721Receiver, IERC1155Receiver {
    using MultiToken for MultiToken.Asset;

    /*----------------------------------------------------------*|
    |*  # EVENTS DEFINITIONS                                    *|
    |*----------------------------------------------------------*/

    /**
     * @dev Emitted when asset transfer happens from an `origin` address to a vault.
     */
    event VaultPull(MultiToken.Asset asset, address indexed origin);

    /**
     * @dev Emitted when asset transfer happens from a vault to a `beneficiary` address.
     */
    event VaultPush(MultiToken.Asset asset, address indexed beneficiary);

    /**
     * @dev Emitted when asset transfer happens from an `origin` address to a `beneficiary` address.
     */
    event VaultPushFrom(MultiToken.Asset asset, address indexed origin, address indexed beneficiary);


    /*----------------------------------------------------------*|
    |*  # TRANSFER FUNCTIONS                                    *|
    |*----------------------------------------------------------*/

    /**
     * pull
     * @dev Function accessing an asset and pulling it INTO a vault.
     *      The function assumes a prior token approval was made to a vault address.
     * @param asset An asset construct - for a definition see { MultiToken dependency lib }.
     * @param origin Borrower address that is transferring collateral to Vault or repaying a loan.
     */
    function _pull(MultiToken.Asset memory asset, address origin) internal {
        uint256 originalBalance = asset.balanceOf(address(this));

        asset.transferAssetFrom(origin, address(this));
        _checkTransfer(asset, originalBalance, address(this));

        emit VaultPull(asset, origin);
    }

    /**
     * push
     * @dev Function pushing an asset FROM a vault TO a defined recipient.
     *      This is used for claiming a paid back loan or a defaulted collateral, or returning collateral to a borrower.
     * @param asset An asset construct - for a definition see { MultiToken dependency lib }.
     * @param beneficiary An address of a recipient of an asset.
     */
    function _push(MultiToken.Asset memory asset, address beneficiary) internal {
        uint256 originalBalance = asset.balanceOf(beneficiary);

        asset.safeTransferAssetFrom(address(this), beneficiary);
        _checkTransfer(asset, originalBalance, beneficiary);

        emit VaultPush(asset, beneficiary);
    }

    /**
     * pushFrom
     * @dev Function pushing an asset FROM a lender TO a borrower.
     *      The function assumes a prior token approval was made to a vault address.
     * @param asset An asset construct - for a definition see { MultiToken dependency lib }.
     * @param origin An address of a lender who is providing a loan asset.
     * @param beneficiary An address of the recipient of an asset.
     */
    function _pushFrom(MultiToken.Asset memory asset, address origin, address beneficiary) internal {
        uint256 originalBalance = asset.balanceOf(beneficiary);

        asset.safeTransferAssetFrom(origin, beneficiary);
        _checkTransfer(asset, originalBalance, beneficiary);

        emit VaultPushFrom(asset, origin, beneficiary);
    }

    function _checkTransfer(MultiToken.Asset memory asset, uint256 originalBalance, address recipient) private view {
        if (originalBalance + asset.getTransferAmount() != asset.balanceOf(recipient))
            revert IncompleteTransfer();
    }


    /*----------------------------------------------------------*|
    |*  # PERMIT                                                *|
    |*----------------------------------------------------------*/

    /**
     * permit
     * @dev Function uses signed permit data to set vaults allowance for an asset.
     * @param asset An asset construct - for a definition see { MultiToken dependency lib }.
     * @param origin An address who is approving an asset.
     * @param permit Data about permit deadline (uint256) and permit signature (64/65 bytes).
     *               Deadline and signature should be pack encoded together.
     *               Signature can be standard (65 bytes) or compact (64 bytes) defined in EIP-2098.
     */
    function _permit(MultiToken.Asset memory asset, address origin, bytes memory permit) internal {
        if (permit.length > 0)
            asset.permit(origin, address(this), permit);
    }


    /*----------------------------------------------------------*|
    |*  # ERC721/1155 RECEIVED HOOKS                            *|
    |*----------------------------------------------------------*/

    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * @return `IERC721Receiver.onERC721Received.selector` if transfer is allowed
     */
    function onERC721Received(
        address operator,
        address /*from*/,
        uint256 /*tokenId*/,
        bytes calldata /*data*/
    ) override external view returns (bytes4) {
        if (operator != address(this))
            revert UnsupportedTransferFunction();

        return IERC721Receiver.onERC721Received.selector;
    }

    /**
     * @dev Handles the receipt of a single ERC1155 token type. This function is
     * called at the end of a `safeTransferFrom` after the balance has been updated.
     * To accept the transfer, this must return
     * `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
     * (i.e. 0xf23a6e61, or its own function selector).
     * @return `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))` if transfer is allowed
     */
    function onERC1155Received(
        address operator,
        address /*from*/,
        uint256 /*id*/,
        uint256 /*value*/,
        bytes calldata /*data*/
    ) override external view returns (bytes4) {
        if (operator != address(this))
            revert UnsupportedTransferFunction();

        return IERC1155Receiver.onERC1155Received.selector;
    }

    /**
     * @dev Handles the receipt of a multiple ERC1155 token types. This function
     * is called at the end of a `safeBatchTransferFrom` after the balances have
     * been updated. To accept the transfer(s), this must return
     * `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
     * (i.e. 0xbc197c81, or its own function selector).
     * @return `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))` if transfer is allowed
     */
    function onERC1155BatchReceived(
        address /*operator*/,
        address /*from*/,
        uint256[] calldata /*ids*/,
        uint256[] calldata /*values*/,
        bytes calldata /*data*/
    ) override external pure returns (bytes4) {
        revert UnsupportedTransferFunction();
    }


    /*----------------------------------------------------------*|
    |*  # SUPPORTED INTERFACES                                  *|
    |*----------------------------------------------------------*/

    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external pure virtual override returns (bool) {
        return
            interfaceId == type(IERC165).interfaceId ||
            interfaceId == type(IERC721Receiver).interfaceId ||
            interfaceId == type(IERC1155Receiver).interfaceId;
    }

}

// File: src/PWNErrors.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;


// Access control
error CallerMissingHubTag(bytes32);

// Loan contract
error LoanDefaulted(uint40);
error InvalidLoanStatus(uint256);
error NonExistingLoan();
error CallerNotLOANTokenHolder();
error InvalidExtendedExpirationDate();

// Invalid asset
error InvalidLoanAsset();
error InvalidCollateralAsset();

// LOAN token
error InvalidLoanContractCaller();

// Vault
error UnsupportedTransferFunction();
error IncompleteTransfer();

// Nonce
error NonceAlreadyRevoked();
error InvalidMinNonce();

// Signature checks
error InvalidSignatureLength(uint256);
error InvalidSignature();

// Offer
error CallerIsNotStatedBorrower(address);
error OfferExpired();
error CollateralIdIsNotWhitelisted();

// Request
error CallerIsNotStatedLender(address);
error RequestExpired();

// Request & Offer
error InvalidDuration();

// Input data
error InvalidInputData();

// Config
error InvalidFeeValue();
error InvalidFeeCollector();

// File: lib/openzeppelin-contracts/contracts/interfaces/IERC20.sol



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

pragma solidity ^0.8.0;

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

// File: lib/openzeppelin-contracts/contracts/interfaces/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC721.sol)

pragma solidity ^0.8.0;

import "../token/ERC721/IERC721.sol";

// File: lib/openzeppelin-contracts/contracts/interfaces/IERC1155.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (interfaces/IERC1155.sol)

pragma solidity ^0.8.0;

import "../token/ERC1155/IERC1155.sol";

// File: lib/openzeppelin-contracts/contracts/token/ERC20/extensions/draft-IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// File: lib/openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.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));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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");
        }
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/introspection/ERC165Checker.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/introspection/ERC165Checker.sol)

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Library used to query support of an interface declared via {IERC165}.
 *
 * Note that these functions return the actual result of the query: they do not
 * `revert` if an interface is not supported. It is up to the caller to decide
 * what to do in these cases.
 */
library ERC165Checker {
    // As per the EIP-165 spec, no interface should ever match 0xffffffff
    bytes4 private constant _INTERFACE_ID_INVALID = 0xffffffff;

    /**
     * @dev Returns true if `account` supports the {IERC165} interface.
     */
    function supportsERC165(address account) internal view returns (bool) {
        // Any contract that implements ERC165 must explicitly indicate support of
        // InterfaceId_ERC165 and explicitly indicate non-support of InterfaceId_Invalid
        return
            supportsERC165InterfaceUnchecked(account, type(IERC165).interfaceId) &&
            !supportsERC165InterfaceUnchecked(account, _INTERFACE_ID_INVALID);
    }

    /**
     * @dev Returns true if `account` supports the interface defined by
     * `interfaceId`. Support for {IERC165} itself is queried automatically.
     *
     * See {IERC165-supportsInterface}.
     */
    function supportsInterface(address account, bytes4 interfaceId) internal view returns (bool) {
        // query support of both ERC165 as per the spec and support of _interfaceId
        return supportsERC165(account) && supportsERC165InterfaceUnchecked(account, interfaceId);
    }

    /**
     * @dev Returns a boolean array where each value corresponds to the
     * interfaces passed in and whether they're supported or not. This allows
     * you to batch check interfaces for a contract where your expectation
     * is that some interfaces may not be supported.
     *
     * See {IERC165-supportsInterface}.
     *
     * _Available since v3.4._
     */
    function getSupportedInterfaces(address account, bytes4[] memory interfaceIds)
        internal
        view
        returns (bool[] memory)
    {
        // an array of booleans corresponding to interfaceIds and whether they're supported or not
        bool[] memory interfaceIdsSupported = new bool[](interfaceIds.length);

        // query support of ERC165 itself
        if (supportsERC165(account)) {
            // query support of each interface in interfaceIds
            for (uint256 i = 0; i < interfaceIds.length; i++) {
                interfaceIdsSupported[i] = supportsERC165InterfaceUnchecked(account, interfaceIds[i]);
            }
        }

        return interfaceIdsSupported;
    }

    /**
     * @dev Returns true if `account` supports all the interfaces defined in
     * `interfaceIds`. Support for {IERC165} itself is queried automatically.
     *
     * Batch-querying can lead to gas savings by skipping repeated checks for
     * {IERC165} support.
     *
     * See {IERC165-supportsInterface}.
     */
    function supportsAllInterfaces(address account, bytes4[] memory interfaceIds) internal view returns (bool) {
        // query support of ERC165 itself
        if (!supportsERC165(account)) {
            return false;
        }

        // query support of each interface in interfaceIds
        for (uint256 i = 0; i < interfaceIds.length; i++) {
            if (!supportsERC165InterfaceUnchecked(account, interfaceIds[i])) {
                return false;
            }
        }

        // all interfaces supported
        return true;
    }

    /**
     * @notice Query if a contract implements an interface, does not check ERC165 support
     * @param account The address of the contract to query for support of an interface
     * @param interfaceId The interface identifier, as specified in ERC-165
     * @return true if the contract at account indicates support of the interface with
     * identifier interfaceId, false otherwise
     * @dev Assumes that account contains a contract that supports ERC165, otherwise
     * the behavior of this method is undefined. This precondition can be checked
     * with {supportsERC165}.
     * Interface identification is specified in ERC-165.
     */
    function supportsERC165InterfaceUnchecked(address account, bytes4 interfaceId) internal view returns (bool) {
        // prepare call
        bytes memory encodedParams = abi.encodeWithSelector(IERC165.supportsInterface.selector, interfaceId);

        // perform static call
        bool success;
        uint256 returnSize;
        uint256 returnValue;
        assembly {
            success := staticcall(30000, account, add(encodedParams, 0x20), mload(encodedParams), 0x00, 0x20)
            returnSize := returndatasize()
            returnValue := mload(0x00)
        }

        return success && returnSize >= 0x20 && returnValue > 0;
    }
}

// File: lib/MultiToken/src/interfaces/ICryptoKitties.sol



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

interface ICryptoKitties {
    // Required methods
    function totalSupply() external view returns (uint256 total);
    function balanceOf(address _owner) external view returns (uint256 balance);
    function ownerOf(uint256 _tokenId) external view returns (address owner);
    function approve(address _to, uint256 _tokenId) external;
    function transfer(address _to, uint256 _tokenId) external;
    function transferFrom(address _from, address _to, uint256 _tokenId) external;

    // Optional
    function name() external view returns (string memory name);
    function symbol() external view returns (string memory symbol);
    function tokensOfOwner(address _owner) external view returns (uint256[] memory tokenIds);
    function tokenMetadata(uint256 _tokenId, string memory _preferredTransport) external view returns (string memory infoUrl);

    // Events
    event Transfer(address from, address to, uint256 tokenId);
    event Approval(address owner, address approved, uint256 tokenId);

    // ERC-165 Compatibility (https://github.com/ethereum/EIPs/issues/165)
    // Is not part of the interface id
    function supportsInterface(bytes4 _interfaceID) external view returns (bool);
}

// File: lib/openzeppelin-contracts/contracts/access/Ownable2Step.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (access/Ownable2Step.sol)

pragma solidity ^0.8.0;

import "./Ownable.sol";

/**
 * @dev Contract module which provides 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} and {acceptOwnership}.
 *
 * This module is used through inheritance. It will make available all functions
 * from parent (Ownable).
 */
abstract contract Ownable2Step is Ownable {
    address private _pendingOwner;

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

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

    /**
     * @dev Starts the ownership transfer of the contract to a new account. Replaces the pending transfer if there is one.
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual override onlyOwner {
        _pendingOwner = newOwner;
        emit OwnershipTransferStarted(owner(), newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`) and deletes any pending owner.
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual override {
        delete _pendingOwner;
        super._transferOwnership(newOwner);
    }

    /**
     * @dev The new owner accepts the ownership transfer.
     */
    function acceptOwnership() external {
        address sender = _msgSender();
        require(pendingOwner() == sender, "Ownable2Step: caller is not the new owner");
        _transferOwnership(sender);
    }
}

// File: lib/openzeppelin-contracts/contracts/proxy/utils/Initializable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (proxy/utils/Initializable.sol)

pragma solidity ^0.8.2;

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

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since proxied contracts do not make use of a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * The initialization functions use a version number. Once a version number is used, it is consumed and cannot be
 * reused. This mechanism prevents re-execution of each "step" but allows the creation of new initialization steps in
 * case an upgrade adds a module that needs to be initialized.
 *
 * For example:
 *
 * [.hljs-theme-light.nopadding]
 * ```
 * contract MyToken is ERC20Upgradeable {
 *     function initialize() initializer public {
 *         __ERC20_init("MyToken", "MTK");
 *     }
 * }
 * contract MyTokenV2 is MyToken, ERC20PermitUpgradeable {
 *     function initializeV2() reinitializer(2) public {
 *         __ERC20Permit_init("MyToken");
 *     }
 * }
 * ```
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {ERC1967Proxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 *
 * [CAUTION]
 * ====
 * Avoid leaving a contract uninitialized.
 *
 * An uninitialized contract can be taken over by an attacker. This applies to both a proxy and its implementation
 * contract, which may impact the proxy. To prevent the implementation contract from being used, you should invoke
 * the {_disableInitializers} function in the constructor to automatically lock it when it is deployed:
 *
 * [.hljs-theme-light.nopadding]
 * ```
 * /// @custom:oz-upgrades-unsafe-allow constructor
 * constructor() {
 *     _disableInitializers();
 * }
 * ```
 * ====
 */
abstract contract Initializable {
    /**
     * @dev Indicates that the contract has been initialized.
     * @custom:oz-retyped-from bool
     */
    uint8 private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Triggered when the contract has been initialized or reinitialized.
     */
    event Initialized(uint8 version);

    /**
     * @dev A modifier that defines a protected initializer function that can be invoked at most once. In its scope,
     * `onlyInitializing` functions can be used to initialize parent contracts.
     *
     * Similar to `reinitializer(1)`, except that functions marked with `initializer` can be nested in the context of a
     * constructor.
     *
     * Emits an {Initialized} event.
     */
    modifier initializer() {
        bool isTopLevelCall = !_initializing;
        require(
            (isTopLevelCall && _initialized < 1) || (!Address.isContract(address(this)) && _initialized == 1),
            "Initializable: contract is already initialized"
        );
        _initialized = 1;
        if (isTopLevelCall) {
            _initializing = true;
        }
        _;
        if (isTopLevelCall) {
            _initializing = false;
            emit Initialized(1);
        }
    }

    /**
     * @dev A modifier that defines a protected reinitializer function that can be invoked at most once, and only if the
     * contract hasn't been initialized to a greater version before. In its scope, `onlyInitializing` functions can be
     * used to initialize parent contracts.
     *
     * A reinitializer may be used after the original initialization step. This is essential to configure modules that
     * are added through upgrades and that require initialization.
     *
     * When `version` is 1, this modifier is similar to `initializer`, except that functions marked with `reinitializer`
     * cannot be nested. If one is invoked in the context of another, execution will revert.
     *
     * Note that versions can jump in increments greater than 1; this implies that if multiple reinitializers coexist in
     * a contract, executing them in the right order is up to the developer or operator.
     *
     * WARNING: setting the version to 255 will prevent any future reinitialization.
     *
     * Emits an {Initialized} event.
     */
    modifier reinitializer(uint8 version) {
        require(!_initializing && _initialized < version, "Initializable: contract is already initialized");
        _initialized = version;
        _initializing = true;
        _;
        _initializing = false;
        emit Initialized(version);
    }

    /**
     * @dev Modifier to protect an initialization function so that it can only be invoked by functions with the
     * {initializer} and {reinitializer} modifiers, directly or indirectly.
     */
    modifier onlyInitializing() {
        require(_initializing, "Initializable: contract is not initializing");
        _;
    }

    /**
     * @dev Locks the contract, preventing any future reinitialization. This cannot be part of an initializer call.
     * Calling this in the constructor of a contract will prevent that contract from being initialized or reinitialized
     * to any version. It is recommended to use this to lock implementation contracts that are designed to be called
     * through proxies.
     *
     * Emits an {Initialized} event the first time it is successfully executed.
     */
    function _disableInitializers() internal virtual {
        require(!_initializing, "Initializable: contract is initializing");
        if (_initialized < type(uint8).max) {
            _initialized = type(uint8).max;
            emit Initialized(type(uint8).max);
        }
    }

    /**
     * @dev Returns the highest version that has been initialized. See {reinitializer}.
     */
    function _getInitializedVersion() internal view returns (uint8) {
        return _initialized;
    }

    /**
     * @dev Returns `true` if the contract is currently initializing. See {onlyInitializing}.
     */
    function _isInitializing() internal view returns (bool) {
        return _initializing;
    }
}

// File: lib/openzeppelin-contracts/contracts/token/ERC721/ERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/ERC721.sol)

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/Strings.sol";
import "../../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: address zero is not a valid owner");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _ownerOf(tokenId);
        require(owner != address(0), "ERC721: invalid token ID");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        _requireMinted(tokenId);

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overridden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not token owner or approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        _requireMinted(tokenId);

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        _setApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner or approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner or approved");
        _safeTransfer(from, to, tokenId, data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns the owner of the `tokenId`. Does NOT revert if token doesn't exist
     */
    function _ownerOf(uint256 tokenId) internal view virtual returns (address) {
        return _owners[tokenId];
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _ownerOf(tokenId) != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || isApprovedForAll(owner, spender) || getApproved(tokenId) == spender);
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId, 1);

        // Check that tokenId was not minted by `_beforeTokenTransfer` hook
        require(!_exists(tokenId), "ERC721: token already minted");

        unchecked {
            // Will not overflow unless all 2**256 token ids are minted to the same owner.
            // Given that tokens are minted one by one, it is impossible in practice that
            // this ever happens. Might change if we allow batch minting.
            // The ERC fails to describe this case.
            _balances[to] += 1;
        }

        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);

        _afterTokenTransfer(address(0), to, tokenId, 1);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     * This is an internal function that does not check if the sender is authorized to operate on the token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId, 1);

        // Update ownership in case tokenId was transferred by `_beforeTokenTransfer` hook
        owner = ERC721.ownerOf(tokenId);

        // Clear approvals
        delete _tokenApprovals[tokenId];

        unchecked {
            // Cannot overflow, as that would require more tokens to be burned/transferred
            // out than the owner initially received through minting and transferring in.
            _balances[owner] -= 1;
        }
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);

        _afterTokenTransfer(owner, address(0), tokenId, 1);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId, 1);

        // Check that tokenId was not transferred by `_beforeTokenTransfer` hook
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");

        // Clear approvals from the previous owner
        delete _tokenApprovals[tokenId];

        unchecked {
            // `_balances[from]` cannot overflow for the same reason as described in `_burn`:
            // `from`'s balance is the number of token held, which is at least one before the current
            // transfer.
            // `_balances[to]` could overflow in the conditions described in `_mint`. That would require
            // all 2**256 token ids to be minted, which in practice is impossible.
            _balances[from] -= 1;
            _balances[to] += 1;
        }
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);

        _afterTokenTransfer(from, to, tokenId, 1);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits an {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Approve `operator` to operate on all of `owner` tokens
     *
     * Emits an {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @dev Reverts if the `tokenId` has not been minted yet.
     */
    function _requireMinted(uint256 tokenId) internal view virtual {
        require(_exists(tokenId), "ERC721: invalid token ID");
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    /// @solidity memory-safe-assembly
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting and burning. If {ERC721Consecutive} is
     * used, the hook may be called as part of a consecutive (batch) mint, as indicated by `batchSize` greater than 1.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s tokens will be transferred to `to`.
     * - When `from` is zero, the tokens will be minted for `to`.
     * - When `to` is zero, ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     * - `batchSize` is non-zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256, /* firstTokenId */
        uint256 batchSize
    ) internal virtual {
        if (batchSize > 1) {
            if (from != address(0)) {
                _balances[from] -= batchSize;
            }
            if (to != address(0)) {
                _balances[to] += batchSize;
            }
        }
    }

    /**
     * @dev Hook that is called after any token transfer. This includes minting and burning. If {ERC721Consecutive} is
     * used, the hook may be called as part of a consecutive (batch) mint, as indicated by `batchSize` greater than 1.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s tokens were transferred to `to`.
     * - When `from` is zero, the tokens were minted for `to`.
     * - When `to` is zero, ``from``'s tokens were burned.
     * - `from` and `to` are never both zero.
     * - `batchSize` is non-zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 firstTokenId,
        uint256 batchSize
    ) internal virtual {}
}

// File: src/hub/PWNHubAccessControl.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

import "@pwn/hub/PWNHub.sol";
import "@pwn/hub/PWNHubTags.sol";
import "@pwn/PWNErrors.sol";


/**
 * @title PWN Hub Access Control
 * @notice Implement modifiers for PWN Hub access control.
 */
abstract contract PWNHubAccessControl {

    /*----------------------------------------------------------*|
    |*  # VARIABLES & CONSTANTS DEFINITIONS                     *|
    |*----------------------------------------------------------*/

    PWNHub immutable internal hub;


    /*----------------------------------------------------------*|
    |*  # MODIFIERS                                             *|
    |*----------------------------------------------------------*/

    modifier onlyActiveLoan() {
        if (hub.hasTag(msg.sender, PWNHubTags.ACTIVE_LOAN) == false)
            revert CallerMissingHubTag(PWNHubTags.ACTIVE_LOAN);
        _;
    }

    modifier onlyWithTag(bytes32 tag) {
        if (hub.hasTag(msg.sender, tag) == false)
            revert CallerMissingHubTag(tag);
        _;
    }


    /*----------------------------------------------------------*|
    |*  # CONSTRUCTOR                                           *|
    |*----------------------------------------------------------*/

    constructor(address pwnHub) {
        hub = PWNHub(pwnHub);
    }

}

// File: src/loan/token/IPWNLoanMetadataProvider.sol



// SPDX-License-Identifier: GPL-3.0-only
pragma solidity 0.8.16;

/**
 * @title PWN Loan Metadata Provider
 * @notice Interface for a provider of a LOAN token metadata.
 * @dev Loan contracts should implement this interface.
 */
interface IPWNLoanMetadataProvider {

    /**
     * @notice Get a loan metadata uri for a LOAN token minted by this contract.
     * @return LOAN token metadata uri.
     */
    function loanMetadataUri() external view returns (string memory);

}

// File: lib/openzeppelin-contracts/contracts/token/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721Receiver.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: lib/openzeppelin-contracts/contracts/token/ERC1155/IERC1155Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC1155/IERC1155Receiver.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev _Available since v3.1._
 */
interface IERC1155Receiver is IERC165 {
    /**
     * @dev Handles the receipt of a single ERC1155 token type. This function is
     * called at the end of a `safeTransferFrom` after the balance has been updated.
     *
     * NOTE: To accept the transfer, this must return
     * `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))`
     * (i.e. 0xf23a6e61, or its own function selector).
     *
     * @param operator The address which initiated the transfer (i.e. msg.sender)
     * @param from The address which previously owned the token
     * @param id The ID of the token being transferred
     * @param value The amount of tokens being transferred
     * @param data Additional data with no specified format
     * @return `bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)"))` if transfer is allowed
     */
    function onERC1155Received(
        address operator,
        address from,
        uint256 id,
        uint256 value,
        bytes calldata data
    ) external returns (bytes4);

    /**
     * @dev Handles the receipt of a multiple ERC1155 token types. This function
     * is called at the end of a `safeBatchTransferFrom` after the balances have
     * been updated.
     *
     * NOTE: To accept the transfer(s), this must return
     * `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))`
     * (i.e. 0xbc197c81, or its own function selector).
     *
     * @param operator The address which initiated the batch transfer (i.e. msg.sender)
     * @param from The address which previously owned the token
     * @param ids An array containing ids of each token being transferred (order and length must match values array)
     * @param values An array containing amounts of each token being transferred (order and length must match ids array)
     * @param data Additional data with no specified format
     * @return `bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))` if transfer is allowed
     */
    function onERC1155BatchReceived(
        address operator,
        address from,
        uint256[] calldata ids,
        uint256[] calldata values,
        bytes calldata data
    ) external returns (bytes4);
}

// File: lib/openzeppelin-contracts/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

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

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

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

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

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

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

// File: lib/openzeppelin-contracts/contracts/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Note that the caller is responsible to confirm that the recipient is capable of receiving ERC721
     * or else they may be permanently lost. Usage of {safeTransferFrom} prevents loss, though the caller must
     * understand this adds an external call which potentially creates a reentrancy vulnerability.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

// File: lib/openzeppelin-contracts/contracts/token/ERC1155/IERC1155.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC1155/IERC1155.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC1155 compliant contract, as defined in the
 * https://eips.ethereum.org/EIPS/eip-1155[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155 is IERC165 {
    /**
     * @dev Emitted when `value` tokens of token type `id` are transferred from `from` to `to` by `operator`.
     */
    event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);

    /**
     * @dev Equivalent to multiple {TransferSingle} events, where `operator`, `from` and `to` are the same for all
     * transfers.
     */
    event TransferBatch(
        address indexed operator,
        address indexed from,
        address indexed to,
        uint256[] ids,
        uint256[] values
    );

    /**
     * @dev Emitted when `account` grants or revokes permission to `operator` to transfer their tokens, according to
     * `approved`.
     */
    event ApprovalForAll(address indexed account, address indexed operator, bool approved);

    /**
     * @dev Emitted when the URI for token type `id` changes to `value`, if it is a non-programmatic URI.
     *
     * If an {URI} event was emitted for `id`, the standard
     * https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[guarantees] that `value` will equal the value
     * returned by {IERC1155MetadataURI-uri}.
     */
    event URI(string value, uint256 indexed id);

    /**
     * @dev Returns the amount of tokens of token type `id` owned by `account`.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function balanceOf(address account, uint256 id) external view returns (uint256);

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {balanceOf}.
     *
     * Requirements:
     *
     * - `accounts` and `ids` must have the same length.
     */
    function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids)
        external
        view
        returns (uint256[] memory);

    /**
     * @dev Grants or revokes permission to `operator` to transfer the caller's tokens, according to `approved`,
     *
     * Emits an {ApprovalForAll} event.
     *
     * Requirements:
     *
     * - `operator` cannot be the caller.
     */
    function setApprovalForAll(address operator, bool approved) external;

    /**
     * @dev Returns true if `operator` is approved to transfer ``account``'s tokens.
     *
     * See {setApprovalForAll}.
     */
    function isApprovedForAll(address account, address operator) external view returns (bool);

    /**
     * @dev Transfers `amount` tokens of token type `id` from `from` to `to`.
     *
     * Emits a {TransferSingle} event.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - If the caller is not `from`, it must have been approved to spend ``from``'s tokens via {setApprovalForAll}.
     * - `from` must have a balance of tokens of type `id` of at least `amount`.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
     * acceptance magic value.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes calldata data
    ) external;

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {safeTransferFrom}.
     *
     * Emits a {TransferBatch} event.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
     * acceptance magic value.
     */
    function safeBatchTransferFrom(
        address from,
        address to,
        uint256[] calldata ids,
        uint256[] calldata amounts,
        bytes calldata data
    ) external;
}

// File: lib/openzeppelin-contracts/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or 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 {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: lib/openzeppelin-contracts/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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);
    }
}

// File: lib/openzeppelin-contracts/contracts/token/ERC721/extensions/IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

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

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: lib/openzeppelin-contracts/contracts/utils/Context.sol



// 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;
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

import "./math/Math.sol";

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        unchecked {
            uint256 length = Math.log10(value) + 1;
            string memory buffer = new string(length);
            uint256 ptr;
            /// @solidity memory-safe-assembly
            assembly {
                ptr := add(buffer, add(32, length))
            }
            while (true) {
                ptr--;
                /// @solidity memory-safe-assembly
                assembly {
                    mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                }
                value /= 10;
                if (value == 0) break;
            }
            return buffer;
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        unchecked {
            return toHexString(value, Math.log256(value) + 1);
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// File: lib/openzeppelin-contracts/contracts/utils/math/Math.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    enum Rounding {
        Down, // Toward negative infinity
        Up, // Toward infinity
        Zero // Toward zero
    }

    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a > b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a == 0 ? 0 : (a - 1) / b + 1;
    }

    /**
     * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
     * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
     * with further edits by Uniswap Labs also under MIT license.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator
    ) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
            // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2^256 + prod0.
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(x, y, not(0))
                prod0 := mul(x, y)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division.
            if (prod1 == 0) {
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1);

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0].
            uint256 remainder;
            assembly {
                // Compute remainder using mulmod.
                remainder := mulmod(x, y, denominator)

                // Subtract 256 bit number from 512 bit number.
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
            // See https://cs.stackexchange.com/q/138556/92363.

            // Does not overflow because the denominator cannot be zero at this stage in the function.
            uint256 twos = denominator & (~denominator + 1);
            assembly {
                // Divide denominator by twos.
                denominator := div(denominator, twos)

                // Divide [prod1 prod0] by twos.
                prod0 := div(prod0, twos)

                // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                twos := add(div(sub(0, twos), twos), 1)
            }

            // Shift in bits from prod1 into prod0.
            prod0 |= prod1 * twos;

            // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
            // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
            // four bits. That is, denominator * inv = 1 mod 2^4.
            uint256 inverse = (3 * denominator) ^ 2;

            // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
            // in modular arithmetic, doubling the correct bits in each step.
            inverse *= 2 - denominator * inverse; // inverse mod 2^8
            inverse *= 2 - denominator * inverse; // inverse mod 2^16
            inverse *= 2 - denominator * inverse; // inverse mod 2^32
            inverse *= 2 - denominator * inverse; // inverse mod 2^64
            inverse *= 2 - denominator * inverse; // inverse mod 2^128
            inverse *= 2 - denominator * inverse; // inverse mod 2^256

            // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
            // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
            // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inverse;
            return result;
        }
    }

    /**
     * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator,
        Rounding rounding
    ) internal pure returns (uint256) {
        uint256 result = mulDiv(x, y, denominator);
        if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
            result += 1;
        }
        return result;
    }

    /**
     * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
     *
     * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
     */
    function sqrt(uint256 a) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
        //
        // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
        // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
        //
        // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
        // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
        // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
        //
        // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
        uint256 result = 1 << (log2(a) >> 1);

        // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
        // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
        // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
        // into the expected uint128 result.
        unchecked {
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            return min(result, a / result);
        }
    }

    /**
     * @notice Calculates sqrt(a), following the selected rounding direction.
     */
    function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = sqrt(a);
            return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 2, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 128;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 64;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 32;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 16;
            }
            if (value >> 8 > 0) {
                value >>= 8;
                result += 8;
            }
            if (value >> 4 > 0) {
                value >>= 4;
                result += 4;
            }
            if (value >> 2 > 0) {
                value >>= 2;
                result += 2;
            }
            if (value >> 1 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log2(value);
            return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 10, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >= 10**64) {
                value /= 10**64;
                result += 64;
            }
            if (value >= 10**32) {
                value /= 10**32;
                result += 32;
            }
            if (value >= 10**16) {
                value /= 10**16;
                result += 16;
            }
            if (value >= 10**8) {
                value /= 10**8;
                result += 8;
            }
            if (value >= 10**4) {
                value /= 10**4;
                result += 4;
            }
            if (value >= 10**2) {
                value /= 10**2;
                result += 2;
            }
            if (value >= 10**1) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log10(value);
            return result + (rounding == Rounding.Up && 10**result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 256, rounded down, of a positive value.
     * Returns 0 if given 0.
     *
     * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
     */
    function log256(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 16;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 8;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 4;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 2;
            }
            if (value >> 8 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log256(value);
            return result + (rounding == Rounding.Up && 1 << (result * 8) < value ? 1 : 0);
        }
    }
}