// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

/*
  ______                     ______                                 
 /      \                   /      \                                
|  ▓▓▓▓▓▓\ ______   ______ |  ▓▓▓▓▓▓\__   __   __  ______   ______  
| ▓▓__| ▓▓/      \ /      \| ▓▓___\▓▓  \ |  \ |  \|      \ /      \ 
| ▓▓    ▓▓  ▓▓▓▓▓▓\  ▓▓▓▓▓▓\\▓▓    \| ▓▓ | ▓▓ | ▓▓ \▓▓▓▓▓▓\  ▓▓▓▓▓▓\
| ▓▓▓▓▓▓▓▓ ▓▓  | ▓▓ ▓▓    ▓▓_\▓▓▓▓▓▓\ ▓▓ | ▓▓ | ▓▓/      ▓▓ ▓▓  | ▓▓
| ▓▓  | ▓▓ ▓▓__/ ▓▓ ▓▓▓▓▓▓▓▓  \__| ▓▓ ▓▓_/ ▓▓_/ ▓▓  ▓▓▓▓▓▓▓ ▓▓__/ ▓▓
| ▓▓  | ▓▓ ▓▓    ▓▓\▓▓     \\▓▓    ▓▓\▓▓   ▓▓   ▓▓\▓▓    ▓▓ ▓▓    ▓▓
 \▓▓   \▓▓ ▓▓▓▓▓▓▓  \▓▓▓▓▓▓▓ \▓▓▓▓▓▓  \▓▓▓▓▓\▓▓▓▓  \▓▓▓▓▓▓▓ ▓▓▓▓▓▓▓ 
         | ▓▓                                             | ▓▓      
         | ▓▓                                             | ▓▓      
          \▓▓                                              \▓▓         
 * App:             https://ApeSwap.finance
 * Medium:          https://ape-swap.medium.com
 * Twitter:         https://twitter.com/ape_swap
 * Telegram:        https://t.me/ape_swap
 * Announcements:   https://t.me/ape_swap_news
 * Discord:         https://ApeSwap.click/discord
 * Reddit:          https://reddit.com/r/ApeSwap
 * Instagram:       https://instagram.com/ApeSwap.finance
 * GitHub:          https://github.com/ApeSwapFinance
 */

import "@openzeppelin/contracts-upgradeable/access/AccessControlEnumerableUpgradeable.sol";
import "./interfaces/ICustomBillRefillable.sol";
import "./CustomBill.sol";

/// @title CustomBillRefillable
/// @author ApeSwap.Finance
/// @notice Provides a method of refilling CustomBill contracts without needing owner rights
/// @dev Extends CustomBill
contract CustomBillRefillable is ICustomBillRefillable, CustomBill, AccessControlEnumerableUpgradeable {
    using SafeERC20Upgradeable for IERC20MetadataUpgradeable;
    
    event BillRefilled(address payoutToken, uint256 amountAdded);

    bytes32 public constant REFILL_ROLE = keccak256("REFILL_ROLE");

    function initialize(
        ICustomTreasury _customTreasury,
        BillCreationDetails memory _billCreationDetails,
        BillTerms memory _billTerms,
        BillAccounts memory _billAccounts,
        address[] memory _billRefillers
    ) external {
        super.initialize(
            _customTreasury,
            _billCreationDetails,
            _billTerms,
            _billAccounts
        );

        for (uint i = 0; i < _billRefillers.length; i++) {
            _grantRole(REFILL_ROLE, _billRefillers[i]);
        }
    }

    /**
     * @notice Grant the ability to refill the CustomBill to whitelisted addresses
     * @param _billRefillers Array of addresses to whitelist as bill refillers
     */
    function grantRefillRole(address[] calldata _billRefillers) external override onlyOwner {
        for (uint i = 0; i < _billRefillers.length; i++) {
            _grantRole(REFILL_ROLE, _billRefillers[i]);
        }
    }

    /**
     * @notice Revoke the ability to refill the CustomBill to whitelisted addresses
     * @param _billRefillers Array of addresses to revoke as bill refillers
     */
    function revokeRefillRole(address[] calldata _billRefillers) external override onlyOwner {
        for (uint i = 0; i < _billRefillers.length; i++) {
            _revokeRole(REFILL_ROLE, _billRefillers[i]);
        }
    }

    /**
     *  @notice Transfer payoutTokens from sender to customTreasury and update maxTotalPayout
     *  @param _refillAmount amount of payoutTokens to refill the CustomBill with 
     */
    function refillPayoutToken(uint256 _refillAmount) external override nonReentrant onlyRole(REFILL_ROLE) {
        require(_refillAmount > 0, "Amount is 0");
        require(customTreasury.billContract(address(this)), "Bill is disabled");
        uint256 balanceBefore = payoutToken.balanceOf(address(customTreasury));
        payoutToken.safeTransferFrom(msg.sender, address(customTreasury), _refillAmount);
        uint256 refillAmount = payoutToken.balanceOf(address(customTreasury)) - balanceBefore;
        require(refillAmount > 0, "No refill made");
        uint256 maxTotalPayout = terms.maxTotalPayout + refillAmount;
        terms.maxTotalPayout = maxTotalPayout;
        emit BillRefilled(address(payoutToken), refillAmount);
        emit MaxTotalPayoutChanged(maxTotalPayout);
    }
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

/// @notice VestingCurve interface to allow for simple updates of vesting release schedules.
interface IVestingCurve {
    /**
     * @notice Returns the vested token amount given the inputs below.
     * @param totalPayout Total payout vested once the vestingTerm is up
     * @param vestingTerm Length of time in seconds that tokens are vesting for
     * @param startTimestamp The timestamp of when vesting starts
     * @param checkTimestamp The timestamp to calculate vested tokens
     * @return vestedPayout Total payoutTokens vested at checkTimestamp
     *
     * Requirements
     * - MUST return 0 if checkTimestamp is less than startTimestamp
     * - MUST return totalPayout if checkTimestamp is greater than startTimestamp + vestingTerm,
     * - MUST return a value including or between 0 and totalPayout
     */
    function getVestedPayoutAtTime(
        uint256 totalPayout,
        uint256 vestingTerm,
        uint256 startTimestamp,
        uint256 checkTimestamp
    ) external view returns (uint256 vestedPayout);
}

// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.0;

/**
 * @title Non-Fungible Vesting Token Standard
 * @notice A non-fungible token standard used to vest ERC-20 tokens over a vesting release curve
 *  scheduled using timestamps.
 * @dev Because this standard relies on timestamps for the vesting schedule, it's important to keep track of the
 *  tokens claimed per Vesting NFT so that a user cannot withdraw more tokens than alloted for a specific Vesting NFT.
 */
interface IERC5725 {
    /**
     *  This event is emitted when the payout is claimed through the claim function
     *  @param tokenId the NFT tokenId of the assets being claimed.
     *  @param recipient The address which is receiving the payout.
     *  @param claimAmount The amount of tokens being claimed.
     */
    event PayoutClaimed(uint256 indexed tokenId, address indexed recipient, uint256 claimAmount);

    /**
     * @notice Claim the pending payout for the NFT
     * @dev MUST grant the claimablePayout value at the time of claim being called
     * MUST revert if not called by the token owner or approved users
     * MUST emit PayoutClaimed
     * SHOULD revert if there is nothing to claim
     * @param tokenId The NFT token id
     */
    function claim(uint256 tokenId) external;

    /**
     * @notice Number of tokens for the NFT which have been claimed at the current timestamp
     * @param tokenId The NFT token id
     * @return payout The total amount of payout tokens claimed for this NFT
     */
    function claimedPayout(uint256 tokenId) external view returns (uint256 payout);

    /**
     * @notice Number of tokens for the NFT which can be claimed at the current timestamp
     * @dev It is RECOMMENDED that this is calculated as the `vestedPayout()` subtracted from `payoutClaimed()`.
     * @param tokenId The NFT token id
     * @return payout The amount of unlocked payout tokens for the NFT which have not yet been claimed
     */
    function claimablePayout(uint256 tokenId) external view returns (uint256 payout);

    /**
     * @notice Total amount of tokens which have been vested at the current timestamp.
     *   This number also includes vested tokens which have been claimed.
     * @dev It is RECOMMENDED that this function calls `vestedPayoutAtTime` with
     *   `block.timestamp` as the `timestamp` parameter.
     * @param tokenId The NFT token id
     * @return payout Total amount of tokens which have been vested at the current timestamp.
     */
    function vestedPayout(uint256 tokenId) external view returns (uint256 payout);

    /**
     * @notice Total amount of vested tokens at the provided timestamp.
     *   This number also includes vested tokens which have been claimed.
     * @dev `timestamp` MAY be both in the future and in the past.
     * Zero MUST be returned if the timestamp is before the token was minted.
     * @param tokenId The NFT token id
     * @param timestamp The timestamp to check on, can be both in the past and the future
     * @return payout Total amount of tokens which have been vested at the provided timestamp
     */
    function vestedPayoutAtTime(uint256 tokenId, uint256 timestamp) external view returns (uint256 payout);

    /**
     * @notice Number of tokens for an NFT which are currently vesting.
     * @dev The sum of vestedPayout and vestingPayout SHOULD always be the total payout.
     * @param tokenId The NFT token id
     * @return payout The number of tokens for the NFT which are vesting until a future date.
     */
    function vestingPayout(uint256 tokenId) external view returns (uint256 payout);

    /**
     * @notice The start and end timestamps for the vesting of the provided NFT
     * MUST return the timestamp where no further increase in vestedPayout occurs for `vestingEnd`.
     * @param tokenId The NFT token id
     * @return vestingStart The beginning of the vesting as a unix timestamp
     * @return vestingEnd The ending of the vesting as a unix timestamp
     */
    function vestingPeriod(uint256 tokenId) external view returns (uint256 vestingStart, uint256 vestingEnd);

    /**
     * @notice Token which is used to pay out the vesting claims
     * @param tokenId The NFT token id
     * @return token The token which is used to pay out the vesting claims
     */
    function payoutToken(uint256 tokenId) external view returns (address token);
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

interface ICustomTreasury {
    function deposit(
        address _principalTokenAddress,
        uint256 _amountPrincipalToken,
        uint256 _amountPayoutToken
    ) external;

    function deposit_FeeInPayout(
        address _principalTokenAddress,
        uint256 _amountPrincipalToken,
        uint256 _amountPayoutToken,
        uint256 _feePayoutToken,
        address _feeReceiver
    ) external;

    function initialize(address _payoutToken, address _initialOwner, address _payoutAddress) external;

    function valueOfToken(address _principalTokenAddress, uint256 _amount)
        external
        view
        returns (uint256 value_);

   function payoutToken()
        external
        view
        returns (address token);
    
    function sendPayoutTokens(uint _amountPayoutToken) external;

    function billContract(address _billContract) external returns (bool _isEnabled);
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

import "./ICustomBill.sol";

interface ICustomBillRefillable is ICustomBill {
    function initialize(
        ICustomTreasury _customTreasury,
        BillCreationDetails memory _billCreationDetails,
        BillTerms memory _billTerms,
        BillAccounts memory _billAccounts,
        address[] memory _billRefillers
    ) external;

    function refillPayoutToken(uint256 _refillAmount) external;

    function grantRefillRole(address[] calldata _billRefillers) external;

    function revokeRefillRole(address[] calldata _billRefillers) external;
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/IERC20MetadataUpgradeable.sol";
import "./ICustomTreasury.sol";
import "./IVestingCurve.sol";

interface ICustomBill {
    /// @notice Info for bill holder
    /// @param payout Total payout value
    /// @param payoutClaimed Amount of payout claimed
    /// @param vesting Seconds left until vesting is complete
    /// @param vestingTerm Length of vesting in seconds
    /// @param vestingStartTimestamp Timestamp at start of vesting
    /// @param lastClaimTimestamp Last timestamp interaction
    /// @param truePricePaid Price paid (principal tokens per payout token) in ten-millionths - 4000000 = 0.4
    struct Bill {
        uint256 payout; 
        uint256 payoutClaimed;
        uint256 vesting;
        uint256 vestingTerm; 
        uint256 vestingStartTimestamp;
        uint256 lastClaimTimestamp; 
        uint256 truePricePaid; 
    }

    struct BillCreationDetails {
        address payoutToken;
        address principalToken;
        address initialOwner;
        IVestingCurve vestingCurve;
        uint256[] tierCeilings;
        uint256[] fees;
        bool feeInPayout;
    }

    struct BillTerms {
        uint256 controlVariable;
        uint256 vestingTerm;
        uint256 minimumPrice;
        uint256 maxPayout;
        uint256 maxDebt;
        uint256 maxTotalPayout;
        uint256 initialDebt;
    }

    /// @notice Important accounts related to a CustomBill 
    /// @param feeTo Account which receives the bill fees
    /// @param DAO Account used to change the treasury address
    /// @param billNft BillNFT contract which mints the NFTs
    struct BillAccounts {
        address feeTo;
        address DAO;
        address billNft;
    }

    function initialize(
        ICustomTreasury _customTreasury,
        BillCreationDetails memory _billCreationDetails,
        BillTerms memory _billTerms,
        BillAccounts memory _billAccounts
    ) external;

    function customTreasury() external returns (ICustomTreasury);

    function claim(uint256 billId) external returns (uint256);

    function pendingVesting(uint256 billId) external view returns (uint256);

    function pendingPayout(uint256 billId) external view returns (uint256);

    function vestingPeriod(uint256 billId) external view returns (uint256 vestingStart_, uint256 vestingEnd_);

    function vestingPayout(uint256 billId) external view returns (uint256 vestingPayout_);

    function vestedPayoutAtTime(uint256 billId, uint256 timestamp) external view returns (uint256 vestedPayout_);

    function claimablePayout(uint256 billId) external view returns (uint256 claimablePayout_);

    function payoutToken() external view returns (IERC20MetadataUpgradeable);
    
    function principalToken() external view returns (IERC20MetadataUpgradeable);

    function getBillInfo(uint256 billId) external view returns (Bill memory);
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

import "@openzeppelin/contracts-upgradeable/token/ERC721/extensions/IERC721EnumerableUpgradeable.sol";
import "./IERC5725.sol";

interface IBillNft is IERC5725, IERC721EnumerableUpgradeable {
    struct TokenData {
        uint256 tokenId;
        address billAddress;
    }

    function addMinter(address minter) external;

    function mint(address to, address billAddress) external returns (uint256);

    function mintMany(uint256 amount, address to, address billAddress) external;

    function lockURI() external;

    function setTokenURI(uint256 tokenId, string memory _tokenURI) external;

    function claimMany(uint256[] calldata _tokenIds) external;

    function pendingPayout(uint256 tokenId) external view returns (uint256 pendingPayoutAmount);

    function pendingVesting(uint256 tokenId) external view returns (uint256 pendingSeconds);

    function allTokensDataOfOwner(address owner) external view returns (TokenData[] memory);

    function getTokensOfOwnerByIndexes(address owner, uint256 start, uint256 end) external view returns (TokenData[] memory);

    function tokenDataOfOwnerByIndex(address owner, uint256 index) external view returns (TokenData memory tokenData);
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

/*
  ______                     ______                                 
 /      \                   /      \                                
|  ▓▓▓▓▓▓\ ______   ______ |  ▓▓▓▓▓▓\__   __   __  ______   ______  
| ▓▓__| ▓▓/      \ /      \| ▓▓___\▓▓  \ |  \ |  \|      \ /      \ 
| ▓▓    ▓▓  ▓▓▓▓▓▓\  ▓▓▓▓▓▓\\▓▓    \| ▓▓ | ▓▓ | ▓▓ \▓▓▓▓▓▓\  ▓▓▓▓▓▓\
| ▓▓▓▓▓▓▓▓ ▓▓  | ▓▓ ▓▓    ▓▓_\▓▓▓▓▓▓\ ▓▓ | ▓▓ | ▓▓/      ▓▓ ▓▓  | ▓▓
| ▓▓  | ▓▓ ▓▓__/ ▓▓ ▓▓▓▓▓▓▓▓  \__| ▓▓ ▓▓_/ ▓▓_/ ▓▓  ▓▓▓▓▓▓▓ ▓▓__/ ▓▓
| ▓▓  | ▓▓ ▓▓    ▓▓\▓▓     \\▓▓    ▓▓\▓▓   ▓▓   ▓▓\▓▓    ▓▓ ▓▓    ▓▓
 \▓▓   \▓▓ ▓▓▓▓▓▓▓  \▓▓▓▓▓▓▓ \▓▓▓▓▓▓  \▓▓▓▓▓\▓▓▓▓  \▓▓▓▓▓▓▓ ▓▓▓▓▓▓▓ 
         | ▓▓                                             | ▓▓      
         | ▓▓                                             | ▓▓      
          \▓▓                                              \▓▓         
 * App:             https://ApeSwap.finance
 * Medium:          https://ape-swap.medium.com
 * Twitter:         https://twitter.com/ape_swap
 * Telegram:        https://t.me/ape_swap
 * Announcements:   https://t.me/ape_swap_news
 * Discord:         https://ApeSwap.click/discord
 * Reddit:          https://reddit.com/r/ApeSwap
 * Instagram:       https://instagram.com/ApeSwap.finance
 * GitHub:          https://github.com/ApeSwapFinance
 */

import "../interfaces/IVestingCurve.sol";

contract LinearVestingCurve is IVestingCurve {
    /**
     * @dev See {IVestingCurve-getVestedPayoutAtTime}.
     */
    function getVestedPayoutAtTime(
        uint256 totalPayout,
        uint256 vestingTerm,
        uint256 startTimestamp,
        uint256 checkTimestamp
    ) external pure returns (uint256 vestedPayout) {
        if (checkTimestamp <= startTimestamp) {
            vestedPayout = 0;
        } else if (checkTimestamp >= (startTimestamp + vestingTerm)) {
            vestedPayout = totalPayout;
        } else {
            /// @dev This is where custom vesting curves can be implemented.
            vestedPayout = (totalPayout * (checkTimestamp - startTimestamp)) / vestingTerm;
        }
    }
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

/*
  ______                     ______                                 
 /      \                   /      \                                
|  ▓▓▓▓▓▓\ ______   ______ |  ▓▓▓▓▓▓\__   __   __  ______   ______  
| ▓▓__| ▓▓/      \ /      \| ▓▓___\▓▓  \ |  \ |  \|      \ /      \ 
| ▓▓    ▓▓  ▓▓▓▓▓▓\  ▓▓▓▓▓▓\\▓▓    \| ▓▓ | ▓▓ | ▓▓ \▓▓▓▓▓▓\  ▓▓▓▓▓▓\
| ▓▓▓▓▓▓▓▓ ▓▓  | ▓▓ ▓▓    ▓▓_\▓▓▓▓▓▓\ ▓▓ | ▓▓ | ▓▓/      ▓▓ ▓▓  | ▓▓
| ▓▓  | ▓▓ ▓▓__/ ▓▓ ▓▓▓▓▓▓▓▓  \__| ▓▓ ▓▓_/ ▓▓_/ ▓▓  ▓▓▓▓▓▓▓ ▓▓__/ ▓▓
| ▓▓  | ▓▓ ▓▓    ▓▓\▓▓     \\▓▓    ▓▓\▓▓   ▓▓   ▓▓\▓▓    ▓▓ ▓▓    ▓▓
 \▓▓   \▓▓ ▓▓▓▓▓▓▓  \▓▓▓▓▓▓▓ \▓▓▓▓▓▓  \▓▓▓▓▓\▓▓▓▓  \▓▓▓▓▓▓▓ ▓▓▓▓▓▓▓ 
         | ▓▓                                             | ▓▓      
         | ▓▓                                             | ▓▓      
          \▓▓                                              \▓▓         
 * App:             https://ApeSwap.finance
 * Medium:          https://ape-swap.medium.com
 * Twitter:         https://twitter.com/ape_swap
 * Telegram:        https://t.me/ape_swap
 * Announcements:   https://t.me/ape_swap_news
 * Discord:         https://ApeSwap.click/discord
 * Reddit:          https://reddit.com/r/ApeSwap
 * Instagram:       https://instagram.com/ApeSwap.finance
 * GitHub:          https://github.com/ApeSwapFinance
 */

import "@openzeppelin/contracts-upgradeable/token/ERC20/utils/SafeERC20Upgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/utils/structs/EnumerableSetUpgradeable.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@ape.swap/contracts/contracts/v0.8/access/PendingOwnableUpgradeable.sol";
import "./interfaces/ICustomBill.sol";
import "./interfaces/ICustomTreasury.sol";
import "./interfaces/IBillNft.sol";
import "./curves/LinearVestingCurve.sol";

/**
 * @title CustomBill (ApeSwap Treasury Bill)
 * @author ApeSwap
 * @custom:version 2.1.0 
 * @notice 
 * - Control Variable is scaled up by 100x compared to v1.X.X.
 * - principalToken MUST NOT be a fee-on-transfer token
 * - payoutToken MAY be a fee-on-transfer, but it is HIGHLY recommended that 
 *     the CustomBill and CustomTreasury contracts are whitelisted from the 
 *     fee-on-transfer. This is because the payoutToken makes multiple hops 
 *     between contracts.
 */
contract CustomBill is Initializable, PendingOwnableUpgradeable, ICustomBill, ReentrancyGuard {
    using SafeERC20Upgradeable for IERC20MetadataUpgradeable;
    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.UintSet;

    /* ======== EVENTS ======== */

    event FeeToChanged(address indexed newFeeTo);
    event MaxTotalPayoutChanged(uint256 newMaxTotalPayout);
    event UpdateClaimApproval(address indexed owner, address indexed approvedAccount, bool approved);
    event BillCreated(uint256 deposit, uint256 payout, uint256 expires, uint256 indexed billId);
    event BillClaimed(uint256 indexed billId, address indexed recipient, uint256 payout, uint256 remaining);
    event BillPriceChanged(uint256 internalPrice, uint256 debtRatio);
    event ControlVariableAdjustment(
        uint256 initialBCV,
        uint256 newBCV,
        uint256 adjustment
    );
    event SetFees(
        uint256[] fees,
        uint256[] tierCeilings
    );
    event SetAdjustment(
        uint256 currentBCV,
        uint256 increment,
        uint256 targetBCV,
        uint256 buffer
    );
    event BillInitialized(BillTerms billTerms, uint256 lastDecay);
    event TermsSet(PARAMETER parameter, uint input);

    /* ======== STRUCTS ======== */

    struct FeeTiers {
        uint256 tierCeilings; // principal billed till next tier
        uint256 fees; // in millionths (i.e. 1e4 = 1%)
    }

    // Info for incremental adjustments to control variable 
    struct Adjust {
        uint256 rate; // increment
        uint256 target; // BCV when adjustment finished
        uint256 buffer; // minimum length (in seconds) between adjustments
        uint256 lastAdjustmentTimestamp; // timestamp when last adjustment made
    }

    /* ======== STATE VARIABLES ======== */

    IERC20MetadataUpgradeable public payoutToken; // token paid for principal
    IERC20MetadataUpgradeable public principalToken; // inflow token
    ICustomTreasury public customTreasury; // pays for and receives principal
    address public feeTo; // receives fee
    address public DAO; // change feeTo address
    IBillNft public billNft;
    EnumerableSetUpgradeable.UintSet private billIssuedIds;
    IVestingCurve public vestingCurve;

    uint256 public totalPrincipalBilled;
    uint256 public totalPayoutGiven;

    BillTerms public terms; // stores terms for new bills
    Adjust public adjustment; // stores adjustment to BCV data
    FeeTiers[] public feeTiers; // stores fee tiers

    mapping(uint256 => Bill) public billInfo; // stores bill information for nfts
    mapping(address => mapping(address => bool)) public redeemerApproved; // Stores user approved redeemers

    uint256 public totalDebt; // total value of outstanding bills; used for pricing
    uint256 public lastDecay; // reference block for debt decay

    bool public feeInPayout;
    uint256 public constant MAX_FEE = 1e6;

    /**
     * "Storage gaps are a convention for reserving storage slots in a base contract, allowing future 
     *  versions of that contract to use up those slots without affecting the storage layout of child contracts."
     *
     *  For more info, see "Storage Gaps" at https://docs.openzeppelin.com/ 
     */
    uint256[50] private __gap;

    /* ======== INITIALIZATION ======== */

    function initialize(
        ICustomTreasury _customTreasury,
        BillCreationDetails memory _billCreationDetails,
        BillTerms memory _billTerms,
        BillAccounts memory _billAccounts
    ) public initializer {
        require(address(_customTreasury) != address(0), "customTreasury cannot be zero");
        customTreasury = _customTreasury;
        require(_billCreationDetails.payoutToken == _customTreasury.payoutToken());
        payoutToken = IERC20MetadataUpgradeable(_billCreationDetails.payoutToken);
        require(_billCreationDetails.principalToken != address(0), "principalToken cannot be zero");
        principalToken = IERC20MetadataUpgradeable(_billCreationDetails.principalToken);
        uint256 currentTimestamp = block.timestamp;
        if(address(_billCreationDetails.vestingCurve) == address(0)) {
            vestingCurve = new LinearVestingCurve();
        } else {
            /// @dev Validate vesting curve
            _billCreationDetails.vestingCurve.getVestedPayoutAtTime(1e18, 4000, currentTimestamp - 2000, currentTimestamp);
            vestingCurve = _billCreationDetails.vestingCurve;
        }
        require(_billAccounts.feeTo != address(0), "feeTo cannot be zero");
        feeTo = _billAccounts.feeTo;
        require(_billAccounts.DAO != address(0), "DAO cannot be zero");
        DAO = _billAccounts.DAO;

        require(_billAccounts.billNft != address(0), "billNft cannot be zero");
        billNft = IBillNft(_billAccounts.billNft);
        require(_billCreationDetails.initialOwner != address(0), "owner cannot be zero");
        __Ownable_init();
        _transferOwnership(_billCreationDetails.initialOwner);

        _setFeeTiers(_billCreationDetails.fees, _billCreationDetails.tierCeilings);
        feeInPayout = _billCreationDetails.feeInPayout;

        // Check and set billTerms
        require(currentDebt() == 0, "Debt must be 0" );
        require(_billTerms.vestingTerm >= 129600, "Vesting must be >= 36 hours");
        require(_billTerms.maxPayout <= 1000, "Payout cannot be above 1 percent");
        require(_billTerms.controlVariable > 0, "CV must be above 1");

        terms = _billTerms;

        totalDebt = _billTerms.initialDebt;
        lastDecay = currentTimestamp;
        emit BillInitialized(_billTerms, currentTimestamp);
    }
    
    /* ======== OWNER FUNCTIONS ======== */

    enum PARAMETER { VESTING, MAX_PAYOUT, MAX_DEBT, MIN_PRICE, MAX_TOTAL_PAYOUT }
    /**
     *  @notice set parameters for new bills
     *  @param _parameter PARAMETER
     *  @param _input uint
     */
    function setBillTerms(PARAMETER _parameter, uint256 _input)
        external
        onlyOwner
    {
        if (_parameter == PARAMETER.VESTING) {
            // 0
            require(_input >= 129600, "Vesting must be >= 36 hours");
            terms.vestingTerm = _input;
        } else if (_parameter == PARAMETER.MAX_PAYOUT) {
            // 1
            require(_input <= 1000, "Payout cannot be above 1 percent");
            terms.maxPayout = _input;
        } else if (_parameter == PARAMETER.MAX_DEBT) {
            // 2
            terms.maxDebt = _input;
        } else if (_parameter == PARAMETER.MIN_PRICE) {
            // 3
            terms.minimumPrice = _input;
        } else if (_parameter == PARAMETER.MAX_TOTAL_PAYOUT) {
            // 4
            require(_input >= totalPayoutGiven, "maxTotalPayout cannot be below totalPayoutGiven");
            terms.maxTotalPayout = _input;
        }
        emit TermsSet(_parameter, _input);
    }

    /**
     *  @notice helper function to view the maxTotalPayout
     *  @dev backward compatibility for V1
     *  @return uint256 max amount of payoutTokens to offer
     */
    function getMaxTotalPayout() external view returns (uint256) {
        return terms.maxTotalPayout;
    }

    /**
     *  @notice set the maxTotalPayout of payoutTokens
     *  @param _maxTotalPayout uint256 max amount of payoutTokens to offer
     */
    function setMaxTotalPayout(uint256 _maxTotalPayout) external onlyOwner {
        require(_maxTotalPayout >= totalPayoutGiven, "maxTotalPayout <= totalPayout");
        terms.maxTotalPayout = _maxTotalPayout;
        emit MaxTotalPayoutChanged(_maxTotalPayout);
    }

    /**
     *  @notice Set fees based on totalPrincipalBilled
     *  @param fees Fee settings which corelate to the tierCeilings
     *  @param tierCeilings totalPrincipalBilled amount used to determine when to move to the next fee
     *
     *  Requirements
     *
     *  - tierCeilings MUST be in ascending order
     */
    function setFeeTiers(uint256[] memory fees, uint256[] memory tierCeilings) external onlyOwner {
        _setFeeTiers(fees, tierCeilings);
    }

    /**
     *  @notice set control variable adjustment
     *  @param _rate Amount to add to/subtract from the BCV to reach the target on each adjustment
     *  @param _target Final BCV to be adjusted to
     *  @param _buffer Time in seconds which must pass before the next incremental adjustment
     */
    function setAdjustment(
        uint256 _rate,
        uint256 _target,
        uint256 _buffer
    ) external onlyOwner {
        require(_target > 0, "Target must be above 0");
        /// @dev This is allowing a max price change of 3% per adjustment
        uint256 maxRate = (terms.controlVariable * 30) / 1000;
        if(maxRate == 0) maxRate = 1;
        require(
            _rate <= maxRate,
            "Increment too large"
        );

        adjustment = Adjust({
            rate: _rate,
            target: _target,
            buffer: _buffer,
            /// @dev Subtracting _buffer to be able to run adjustment on next tx
            lastAdjustmentTimestamp: block.timestamp - _buffer
        });
        emit SetAdjustment(terms.controlVariable, _rate, _target, _buffer);
    }

    /**
     *  @notice change address of Treasury
     *  @param _feeTo address
     */
    function changeFeeTo(address _feeTo) external {
        require(msg.sender == DAO, "Only DAO");
        require(_feeTo != address(0), "Cannot be address(0)");
        feeTo = _feeTo;
        emit FeeToChanged(feeTo);
    }

    /* ======== USER FUNCTIONS ======== */

    /**
     *  @notice Purchase a bill by depositing principalTokens
     *  @param _amount Amount of principalTokens to deposit/purchase a bill
     *  @param _maxPrice Max price willing to pay for for this deposit
     *  @param _depositor Address which will own the bill
     *  @return uint256 payout amount in payoutTokens
     * 
     * Requirements
     * - Only Contracts can deposit on behalf of other accounts. Otherwise msg.sender MUST == _depositor.
     * - principalToken MUST NOT be a reflect token
     */
    function deposit(
        uint256 _amount,
        uint256 _maxPrice,
        address _depositor
    ) external nonReentrant returns (uint256) {
        require(_depositor != address(0), "Invalid address");
        require(msg.sender == _depositor || AddressUpgradeable.isContract(msg.sender), "no deposits to other address");

        _decayDebt();
        uint256 truePrice = trueBillPrice();
        require(_maxPrice >= truePrice, "Slippage more than max price"); // slippage protection
        // Calculate payout and fee
        uint256 depositAmount = _amount;
        uint256 payout; 
        uint256 fee;
        if(feeInPayout) {
            (payout, fee) = payoutFor(_amount); // payout and fee is computed
        } else {
            (payout, fee) = payoutFor(_amount); // payout and fee is computed
            depositAmount -= fee;
        }
        // Increase totalDebt by amount deposited
        totalDebt += _amount;
        require(totalDebt <= terms.maxDebt, "Max capacity reached");
        require(payout >= 10 ** payoutToken.decimals() / 10000, "Bill too small" ); // must be > 0.0001 payout token ( underflow protection )
        require(payout <= maxPayout(), "Bill too large"); // size protection because there is no slippage
        totalPayoutGiven += payout; // total payout increased
        require(totalPayoutGiven <= terms.maxTotalPayout, "Max total payout exceeded");
        totalPrincipalBilled += depositAmount; // total billed increased
        // Transfer principal token to BillContract
        principalToken.safeTransferFrom(msg.sender, address(this), _amount);
        principalToken.approve(address(customTreasury), depositAmount);
        uint256 payoutBalanceBefore = payoutToken.balanceOf(address(this));
        if(feeInPayout) {
            // Deposits principal and receives payout tokens
            customTreasury.deposit_FeeInPayout(address(principalToken), depositAmount, payout, fee, feeTo);
        } else {
            // Deposits principal and receives payout tokens
            customTreasury.deposit(address(principalToken), depositAmount, payout);
            if(fee != 0) { // if fee, send to treasury
                principalToken.safeTransfer(feeTo, fee);
            }
        }
        uint256 payoutBalanceAdded = payoutToken.balanceOf(address(this)) - payoutBalanceBefore;
        // Create BillNFT
        uint256 billId = billNft.mint(_depositor, address(this));
        billInfo[billId] = Bill({
            payout: payoutBalanceAdded,
            payoutClaimed: 0,
            vesting: terms.vestingTerm,
            vestingTerm: terms.vestingTerm,
            vestingStartTimestamp: block.timestamp,
            lastClaimTimestamp: block.timestamp,
            truePricePaid: truePrice
        });
        billIssuedIds.add(billId);
        emit BillCreated(_amount, payoutBalanceAdded, block.timestamp + terms.vestingTerm, billId);
        // Adjust control variable
        _adjust();
        emit BillPriceChanged(_billPrice(), debtRatio());
        return payout;
    }

    /**
     *  @notice Claim bill for user
     *  @dev Can only be redeemed by: Owner, BillNft or Approved Redeemer
     *  @param _billId uint256
     *  @return uint
     *
     * Requirements:
     *
     * - billId MUST be valid
     * - bill for billId MUST have a claimablePayout 
     * - MUST be called by Owner, Approved Claimer of BillNft
     */
    function claim(uint256 _billId) external nonReentrant returns (uint256) {
        return _claim(_billId);
    }

    /**
     *  @notice Claim multiple bills for user
     *  @param _billIds Array of billIds to claim
     *  @return payout Total payout claimed
     */
    function batchClaim(uint256[] calldata _billIds) public nonReentrant returns (uint256 payout) { 
        uint256 length = _billIds.length;
        for (uint i = 0; i < length; i++) { 
            payout += _claim(_billIds[i]);
        }
    }

    /**
     * @notice Claim bill for user
     *
     * See {CustomBill-claim}.
     */
    function _claim(uint256 _billId) internal returns (uint256) {
        Bill storage bill = billInfo[_billId];
        require(bill.lastClaimTimestamp > 0, "not a valid bill id");
        // verify claim approval
        address owner = billNft.ownerOf(_billId);
        require(msg.sender == owner || msg.sender == address(billNft) || redeemerApproved[owner][msg.sender], "not approved");
        // verify payout
        uint256 payout = claimablePayout(_billId);
        require(payout > 0, "nothing to claim");
        // adjust payout values
        bill.payoutClaimed += payout;
        // adjust vesting timestamps
        uint256 timeElapsed = block.timestamp - bill.lastClaimTimestamp;
        bill.vesting = timeElapsed >= bill.vesting ? 0 : bill.vesting - timeElapsed;
        bill.lastClaimTimestamp = block.timestamp;
        // transfer, emit and return payout
        payoutToken.safeTransfer(owner, payout);
        emit BillClaimed(_billId, owner, payout, bill.payout);
        return payout;
    }

    /** 
     *  @notice Allows or disallows a third party address to claim bills on behalf of user
     *  @dev Claims are ALWAYS sent to the owner, regardless of which account redeems 
     *  @param approvedAccount Address of account which can claim on behalf of msg.sender
     *  @param approved Set approval state to true or false
     */
    function setClaimApproval(address approvedAccount, bool approved) external {
        redeemerApproved[msg.sender][approvedAccount] = approved;
        emit UpdateClaimApproval(msg.sender, approvedAccount, approved);
    }

    /**
     * @dev See {CustomBill-claim}.
     * @notice Leaving for backward compatibility for V1
     */
    function redeem(uint256 _billId) external nonReentrant returns (uint256) {
        return _claim(_billId);
    }

    /**
     * @dev See {CustomBill-batchClaim}.
     * @notice Leaving for backward compatibility for V1
     */
    function batchRedeem(uint256[] calldata _billIds) external returns (uint256 payout) { 
        return batchClaim(_billIds);
    }

    /* ======== INTERNAL HELPER FUNCTIONS ======== */

    /**
     *  @notice makes incremental adjustment to control variable
     */
    function _adjust() internal {
        uint256 timestampCanAdjust = adjustment.lastAdjustmentTimestamp + adjustment.buffer;
        if(adjustment.rate != 0 && block.timestamp >= timestampCanAdjust) {
            uint256 initial = terms.controlVariable;
            uint256 bcv = terms.controlVariable;
            uint256 rate = adjustment.rate;
            uint256 target = adjustment.target;
            if(bcv > target) {
                // Pulling bcv DOWN to target
                uint256 diff = bcv - target;
                if(diff > rate) {
                    bcv -= rate;
                } else {
                    bcv = target;
                    adjustment.rate = 0;
                }
            } else {
                // Pulling bcv UP to target
                uint256 diff = target - bcv;
                if(diff > rate) {
                    bcv += rate;
                } else {
                    bcv = target;
                    adjustment.rate = 0;
                }
            }
            adjustment.lastAdjustmentTimestamp = block.timestamp;
            terms.controlVariable = bcv;
            emit ControlVariableAdjustment(initial, bcv, adjustment.rate);
        }
    }

    /**
     *  @notice reduce total debt
     */
    function _decayDebt() internal {
        totalDebt -= debtDecay();
        lastDecay = block.timestamp;
    }

    /**
     *  @notice calculate current bill price and remove floor if above
     *  @return price_ uint Price is denominated with 18 decimals
     */
    function _billPrice() internal returns (uint256 price_) {
        price_ = billPrice();
        if (price_ > terms.minimumPrice && terms.minimumPrice != 0) {
            /// @dev minimumPrice is set to zero as it assumes that market equilibrium has been found at this point.
            /// Moving forward the price should find balance through natural market forces such as demand, arbitrage and others
            terms.minimumPrice = 0;
        } 
    }

    /**
     *  @notice Set fees based on totalPrincipalBilled
     *  @param fees Fee settings which corelate to the tierCeilings
     *  @param tierCeilings totalPrincipalBilled amount used to determine when to move to the next fee
     *
     *  Requirements
     *
     *  - tierCeilings MUST be in ascending order
     */
    function _setFeeTiers(uint256[] memory fees, uint256[] memory tierCeilings) internal {
        require(tierCeilings.length == fees.length, "tier length != fee length");
        // Remove old fees
        if(feeTiers.length > 0) {
            for (uint256 j; j < feeTiers.length; j++) {
                feeTiers.pop();
            }
        }
        // Validate and setup new FeeTiers
        uint256 previousCeiling;
        for (uint256 i; i < tierCeilings.length; i++) {
            require(fees[i] < MAX_FEE, "Invalid fee");
            require(i == 0 || previousCeiling < tierCeilings[i], "only increasing order");
            previousCeiling = tierCeilings[i];
            if(getFeeTierLength() > i) {
                /// @dev feeTiers.pop() appears to leave the first element
                feeTiers[i] = FeeTiers({tierCeilings: tierCeilings[i], fees: fees[i]});
            } else {
                feeTiers.push(FeeTiers({tierCeilings: tierCeilings[i], fees: fees[i]}));
            }
        }
        require(fees.length == getFeeTierLength(), "feeTier mismatch");
        emit SetFees(fees, tierCeilings);
    }

    /* ======== VIEW FUNCTIONS ======== */

    /**
     *  @notice get bill info for given billId
     *  @param billId Id of the bill NFT
     *  @return Bill bill details
     */
    function getBillInfo(uint256 billId) external view returns (Bill memory) {
        return billInfo[billId];
    }

    /**
     *  @notice calculate current bill premium
     *  @return price_ uint Price is denominated using 18 decimals
     */
    function billPrice() public view returns (uint256 price_) {
        /// @dev 1e2 * 1e(principalTokenDecimals) * 1e16 / 1e(principalTokenDecimals) = 1e18
        price_ = terms.controlVariable * debtRatio() * 1e16 / 10 ** principalToken.decimals();
        if (price_ < terms.minimumPrice) {
            price_ = terms.minimumPrice;
        }
    }

    /**
     *  @notice calculate true bill price a user pays including the fee
     *  @return price_ uint
     */
    function trueBillPrice() public view returns (uint256 price_) {
        price_ = (billPrice() * MAX_FEE) / (MAX_FEE - currentFee());
    }

    /**
     *  @notice determine maximum bill size
     *  @return uint
     */
    function maxPayout() public view returns (uint256) {
        return (payoutToken.totalSupply() * terms.maxPayout) / 100000;
    }

    /**
     *  @notice calculate user's expected payout for given principal amount. 
     *  @dev If feeInPayout flag is set, the _fee will be returned in payout tokens
     *  If feeInPayout flag is NOT set, the _fee will be returned in principal tokens  
     *  @param _amount uint Amount of principal tokens to deposit
     *  @return _payout uint Amount of payoutTokens given principal tokens 
     *  @return _fee uint Fee is payout or principal tokens depending on feeInPayout flag
     */
    function payoutFor(uint256 _amount) public view returns (uint256 _payout, uint256 _fee) {
        if(feeInPayout) {
            // Using amount of principalTokens, find the amount of payout tokens by dividing by billPrice.
            uint256 total = customTreasury.valueOfToken(address(principalToken), _amount * 1e18) / billPrice();
            // _fee is denominated in payoutToken decimals
            _fee = total * currentFee() / MAX_FEE;
            _payout = total - _fee;
        } else { // feeInPrincipal
            // _fee is denominated in principalToken decimals
            _fee = _amount * currentFee() / MAX_FEE;
            // Using amount of principalTokens - _fee, find the amount of payout tokens by dividing by billPrice.
            _payout = customTreasury.valueOfToken(address(principalToken), (_amount - _fee) * 1e18) / billPrice();
        }
    }

    /**
     *  @notice calculate current ratio of debt to payout token supply
     *  @notice protocols using this system should be careful when quickly adding large %s to total supply
     *  @return debtRatio_ uint debtRatio denominated in principalToken decimals
     */
    function debtRatio() public view returns (uint256 debtRatio_) {
            debtRatio_ = currentDebt() * 10 ** payoutToken.decimals() / payoutToken.totalSupply();
    }

    /**
     *  @notice calculate debt factoring in decay
     *  @return uint currentDebt denominated in principalToken decimals
     */
    function currentDebt() public view returns (uint256) {
        return totalDebt - debtDecay();
    }

    /**
     *  @notice amount to decay total debt by
     *  @return decay_ uint debtDecay denominated in principalToken decimals
     */
    function debtDecay() public view returns (uint256 decay_) {
        if (terms.vestingTerm == 0)
            return totalDebt;
        uint256 timestampSinceLast = block.timestamp - lastDecay;
        decay_ = (totalDebt * timestampSinceLast) / terms.vestingTerm;
        if (decay_ > totalDebt) {
            decay_ = totalDebt;
        }
    }

    /**
     *  @notice Returns the number of seconds left until fully vested.
     *  @dev backward compatibility for V1
     *  @param _billId ID of Bill
     *  @return pendingVesting_ Number of seconds until vestingEnd timestamp
     */
    function pendingVesting(uint256 _billId) external view returns (uint256 pendingVesting_) {
        ( , uint256 vestingEnd, ) = _billTimestamps(_billId);
        pendingVesting_ = 0;
        if(vestingEnd > block.timestamp) {
            pendingVesting_ = vestingEnd - block.timestamp;
        }
    }

    /**
     *  @notice Returns the total payout left for the billId passed. (i.e. claimablePayout + vestingPayout)
     *  @dev backward compatibility for V1
     *  @param _billId ID of Bill 
     *  @return pendingPayout_ uint Payout value still remaining in bill
     */
    function pendingPayout(uint256 _billId) external view returns (uint256 pendingPayout_) {
        ( , uint256 vestingPayoutCurrent, uint256 claimablePayoutCurrent) = _payoutsCurrent(_billId);
        pendingPayout_ = vestingPayoutCurrent + claimablePayoutCurrent;
    }

    /**
     *  @notice Return the vesting start and end times for a Bill by ID
     *  @dev Helper function for ERC5725
     *  @param _billId ID of Bill
     */
    function vestingPeriod(uint256 _billId) public view returns (uint256 vestingStart_, uint256 vestingEnd_) {
        (vestingStart_, vestingEnd_, ) = _billTimestamps(_billId);
    }

    /**
     *  @notice Return the amount of tokens locked in a Bill at the current block.timestamp
     *  @dev Helper function for ERC5725
     *  @param _billId ID of Bill
     */
    function vestingPayout(uint256 _billId) external view returns (uint256 vestingPayout_) {
        ( , vestingPayout_, ) = _payoutsCurrent(_billId);
    }

    /**
     *  @notice Return the amount of tokens unlocked at a specific timestamp. Includes claimed tokens.
     *  @dev Helper function for ERC5725. 
     *  @param _billId ID of Bill
     *  @param _timestamp timestamp to check
     */
    function vestedPayoutAtTime(uint256 _billId, uint256 _timestamp) external view returns (uint256 vestedPayout_) {
        (vestedPayout_, ,) = _payoutsAtTime(_billId, _timestamp);
    }

    /**
     *  @notice Return the amount of payout tokens which are available to be claimed for a Bill.
     *  @dev Helper function for ERC5725. 
     *  @param _billId ID of Bill
     */
    function claimablePayout(uint256 _billId) public view returns (uint256 claimablePayout_) {
        (,,claimablePayout_) = _payoutsCurrent(_billId);
    }

    /**
     * @notice Calculate payoutsAtTime with current timestamp
     * @dev See {CustomBill-_payoutsAtTime}.
     */
    function _payoutsCurrent(uint256 _billId) internal view returns (uint256 vestedPayout_, uint256 vestingPayout_, uint256 claimablePayout_) {
        return _payoutsAtTime(_billId, block.timestamp);
    }
    
    /**
     *  @notice Return the amount of tokens unlocked at a specific timestamp. Includes claimed tokens.
     *  @dev Helper function for ERC5725. 
     *  @param _billId ID of Bill
     *  @param _timestamp timestamp to check
     */
    function _payoutsAtTime(uint256 _billId, uint256 _timestamp) 
        internal 
        view
        returns (uint256 vestedPayout_, uint256 vestingPayout_, uint256 claimablePayout_) 
    {
        Bill memory bill = billInfo[_billId];
        // Calculate vestedPayout
        uint256 fullPayout = bill.payout;
        vestedPayout_ = vestingCurve.getVestedPayoutAtTime(
            fullPayout, 
            bill.vestingTerm, 
            bill.vestingStartTimestamp, 
            _timestamp
        );
        // Calculate vestingPayout
        vestingPayout_ = fullPayout - vestedPayout_;
        // Calculate claimablePayout
        uint256 payoutClaimed = bill.payoutClaimed;
        claimablePayout_ = 0;
        if(payoutClaimed < vestedPayout_) {
            claimablePayout_ = vestedPayout_ - payoutClaimed;
        }
    }

    function _billTimestamps(uint256 _billId) internal view returns (uint256 vestingStart_, uint256 vestingEnd_, uint256 lastClaimTimestamp_) {
        Bill memory bill = billInfo[_billId];
        vestingStart_ = bill.vestingStartTimestamp;
        vestingEnd_ = vestingStart_ + bill.vestingTerm;
        lastClaimTimestamp_ = bill.lastClaimTimestamp;
    }

    /**
     *  @notice calculate all billNft ids for sender
     *  @return billNftIds uint[]
     */
    function userBillIds()
        external
        view
        returns (uint[] memory)
    {
        return getBillIds(msg.sender);
    }

    /**
     *  @notice calculate all billNft ids for user
     *  @return billNftIds uint[]
     */
    function getBillIds(address user)
        public
        view
        returns (uint[] memory)
    {
        uint balance = billNft.balanceOf(user);
        return getBillIdsInRange(user, 0, balance);
    }

    /**
     *  @notice calculate billNft ids in range for user
     *  @return billNftIds uint[]
     */
    function getBillIdsInRange(address user, uint256 start, uint256 end)
        public
        view
        returns (uint256[] memory)
    {
        uint256[] memory result = new uint[](end - start);
        uint256 resultIndex = 0;
        for (uint256 i = start; i < end; i++) {
            uint256 tokenId = billNft.tokenOfOwnerByIndex(user, i);
            if (billIssuedIds.contains(tokenId)) {
                result[resultIndex] = tokenId;
                resultIndex++;
            }
        }
        // Prune results into condensed array
        uint256[] memory prunedResult = new uint256[](resultIndex);
        for (uint256 j = 0; j < resultIndex; j++) {
            prunedResult[j] = result[j];
        }
        return prunedResult;
    }

    /**
     *  @notice current fee taken of each bill
     *  @return currentFee_ uint
     */
    function currentFee() public view returns (uint256 currentFee_) {
        uint256 tierLength = feeTiers.length;
        for (uint256 i; i < tierLength; i++) {
            if (
                totalPrincipalBilled <= feeTiers[i].tierCeilings ||
                i == tierLength - 1
            ) {
                return feeTiers[i].fees;
            }
        }
    }

    /**
     *  @notice Get the number of fee tiers configured
     *  @return tierLength_ uint
     */
    function getFeeTierLength() public view returns (uint256 tierLength_) {
        tierLength_ = feeTiers.length;
    }

    /**
     * From EnumerableSetUpgradeable...
     * 
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function allIssuedBillIds() external view returns (uint256[] memory) {
        return billIssuedIds.values();
    }
}

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

pragma solidity ^0.8.0;

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

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

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

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

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

        _;

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/structs/EnumerableSet.sol)

pragma solidity ^0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 *
 * [WARNING]
 * ====
 *  Trying to delete such a structure from storage will likely result in data corruption, rendering the structure unusable.
 *  See https://github.com/ethereum/solidity/pull/11843[ethereum/solidity#11843] for more info.
 *
 *  In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an array of EnumerableSet.
 * ====
 */
library EnumerableSetUpgradeable {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            if (lastIndex != toDeleteIndex) {
                bytes32 lastValue = set._values[lastIndex];

                // Move the last value to the index where the value to delete is
                set._values[toDeleteIndex] = lastValue;
                // Update the index for the moved value
                set._indexes[lastValue] = valueIndex; // Replace lastValue's index to valueIndex
            }

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        return set._values[index];
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function _values(Set storage set) private view returns (bytes32[] memory) {
        return set._values;
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
        return _values(set._inner);
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(AddressSet storage set) internal view returns (address[] memory) {
        bytes32[] memory store = _values(set._inner);
        address[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }

    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(UintSet storage set) internal view returns (uint256[] memory) {
        bytes32[] memory store = _values(set._inner);
        uint256[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }
}

// 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 IERC165Upgradeable {
    /**
     * @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);
}

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

pragma solidity ^0.8.0;

import "./IERC165Upgradeable.sol";
import "../../proxy/utils/Initializable.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 ERC165Upgradeable is Initializable, IERC165Upgradeable {
    function __ERC165_init() internal onlyInitializing {
    }

    function __ERC165_init_unchained() internal onlyInitializing {
    }
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165Upgradeable).interfaceId;
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[50] private __gap;
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library StringsUpgradeable {
    bytes16 private constant _HEX_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) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @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] = _HEX_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);
    }
}

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

pragma solidity ^0.8.0;
import "../proxy/utils/Initializable.sol";

/**
 * @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 ContextUpgradeable is Initializable {
    function __Context_init() internal onlyInitializing {
    }

    function __Context_init_unchained() internal onlyInitializing {
    }
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[50] private __gap;
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Address.sol)

pragma solidity ^0.8.1;

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

        return account.code.length > 0;
    }

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

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

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

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

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

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

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

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

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

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

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/extensions/IERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "../IERC721Upgradeable.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721EnumerableUpgradeable is IERC721Upgradeable {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165Upgradeable.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721Upgradeable is IERC165Upgradeable {
    /**
     * @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: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20Upgradeable.sol";
import "../extensions/draft-IERC20PermitUpgradeable.sol";
import "../../../utils/AddressUpgradeable.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 SafeERC20Upgradeable {
    using AddressUpgradeable for address;

    function safeTransfer(
        IERC20Upgradeable token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(
        IERC20Upgradeable 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(
        IERC20PermitUpgradeable 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(IERC20Upgradeable token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

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

// SPDX-License-Identifier: 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 IERC20PermitUpgradeable {
    /**
     * @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);
}

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

pragma solidity ^0.8.0;

import "../IERC20Upgradeable.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20MetadataUpgradeable is IERC20Upgradeable {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

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

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

// SPDX-License-Identifier: 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 IERC20Upgradeable {
    /**
     * @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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (proxy/utils/Initializable.sol)

pragma solidity ^0.8.2;

import "../../utils/AddressUpgradeable.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. Equivalent to `reinitializer(1)`.
     */
    modifier initializer() {
        bool isTopLevelCall = !_initializing;
        require(
            (isTopLevelCall && _initialized < 1) || (!AddressUpgradeable.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.
     *
     * `initializer` is equivalent to `reinitializer(1)`, so 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.
     *
     * 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.
     */
    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.
     */
    function _disableInitializers() internal virtual {
        require(!_initializing, "Initializable: contract is initializing");
        if (_initialized < type(uint8).max) {
            _initialized = type(uint8).max;
            emit Initialized(type(uint8).max);
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/ContextUpgradeable.sol";
import "../proxy/utils/Initializable.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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal onlyInitializing {
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal onlyInitializing {
        _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);
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[49] private __gap;
}

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

pragma solidity ^0.8.0;

/**
 * @dev External interface of AccessControl declared to support ERC165 detection.
 */
interface IAccessControlUpgradeable {
    /**
     * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
     *
     * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
     * {RoleAdminChanged} not being emitted signaling this.
     *
     * _Available since v3.1._
     */
    event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);

    /**
     * @dev Emitted when `account` is granted `role`.
     *
     * `sender` is the account that originated the contract call, an admin role
     * bearer except when using {AccessControl-_setupRole}.
     */
    event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Emitted when `account` is revoked `role`.
     *
     * `sender` is the account that originated the contract call:
     *   - if using `revokeRole`, it is the admin role bearer
     *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
     */
    event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) external view returns (bool);

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {AccessControl-_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) external view returns (bytes32);

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function grantRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     */
    function revokeRole(bytes32 role, address account) external;

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been granted `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     */
    function renounceRole(bytes32 role, address account) external;
}

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

pragma solidity ^0.8.0;

import "./IAccessControlUpgradeable.sol";

/**
 * @dev External interface of AccessControlEnumerable declared to support ERC165 detection.
 */
interface IAccessControlEnumerableUpgradeable is IAccessControlUpgradeable {
    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) external view returns (address);

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) external view returns (uint256);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/AccessControl.sol)

pragma solidity ^0.8.0;

import "./IAccessControlUpgradeable.sol";
import "../utils/ContextUpgradeable.sol";
import "../utils/StringsUpgradeable.sol";
import "../utils/introspection/ERC165Upgradeable.sol";
import "../proxy/utils/Initializable.sol";

/**
 * @dev Contract module that allows children to implement role-based access
 * control mechanisms. This is a lightweight version that doesn't allow enumerating role
 * members except through off-chain means by accessing the contract event logs. Some
 * applications may benefit from on-chain enumerability, for those cases see
 * {AccessControlEnumerable}.
 *
 * Roles are referred to by their `bytes32` identifier. These should be exposed
 * in the external API and be unique. The best way to achieve this is by
 * using `public constant` hash digests:
 *
 * ```
 * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
 * ```
 *
 * Roles can be used to represent a set of permissions. To restrict access to a
 * function call, use {hasRole}:
 *
 * ```
 * function foo() public {
 *     require(hasRole(MY_ROLE, msg.sender));
 *     ...
 * }
 * ```
 *
 * Roles can be granted and revoked dynamically via the {grantRole} and
 * {revokeRole} functions. Each role has an associated admin role, and only
 * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
 *
 * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
 * that only accounts with this role will be able to grant or revoke other
 * roles. More complex role relationships can be created by using
 * {_setRoleAdmin}.
 *
 * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
 * grant and revoke this role. Extra precautions should be taken to secure
 * accounts that have been granted it.
 */
abstract contract AccessControlUpgradeable is Initializable, ContextUpgradeable, IAccessControlUpgradeable, ERC165Upgradeable {
    function __AccessControl_init() internal onlyInitializing {
    }

    function __AccessControl_init_unchained() internal onlyInitializing {
    }
    struct RoleData {
        mapping(address => bool) members;
        bytes32 adminRole;
    }

    mapping(bytes32 => RoleData) private _roles;

    bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;

    /**
     * @dev Modifier that checks that an account has a specific role. Reverts
     * with a standardized message including the required role.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     *
     * _Available since v4.1._
     */
    modifier onlyRole(bytes32 role) {
        _checkRole(role);
        _;
    }

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

    /**
     * @dev Returns `true` if `account` has been granted `role`.
     */
    function hasRole(bytes32 role, address account) public view virtual override returns (bool) {
        return _roles[role].members[account];
    }

    /**
     * @dev Revert with a standard message if `_msgSender()` is missing `role`.
     * Overriding this function changes the behavior of the {onlyRole} modifier.
     *
     * Format of the revert message is described in {_checkRole}.
     *
     * _Available since v4.6._
     */
    function _checkRole(bytes32 role) internal view virtual {
        _checkRole(role, _msgSender());
    }

    /**
     * @dev Revert with a standard message if `account` is missing `role`.
     *
     * The format of the revert reason is given by the following regular expression:
     *
     *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
     */
    function _checkRole(bytes32 role, address account) internal view virtual {
        if (!hasRole(role, account)) {
            revert(
                string(
                    abi.encodePacked(
                        "AccessControl: account ",
                        StringsUpgradeable.toHexString(uint160(account), 20),
                        " is missing role ",
                        StringsUpgradeable.toHexString(uint256(role), 32)
                    )
                )
            );
        }
    }

    /**
     * @dev Returns the admin role that controls `role`. See {grantRole} and
     * {revokeRole}.
     *
     * To change a role's admin, use {_setRoleAdmin}.
     */
    function getRoleAdmin(bytes32 role) public view virtual override returns (bytes32) {
        return _roles[role].adminRole;
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleGranted} event.
     */
    function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _grantRole(role, account);
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * If `account` had been granted `role`, emits a {RoleRevoked} event.
     *
     * Requirements:
     *
     * - the caller must have ``role``'s admin role.
     *
     * May emit a {RoleRevoked} event.
     */
    function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
        _revokeRole(role, account);
    }

    /**
     * @dev Revokes `role` from the calling account.
     *
     * Roles are often managed via {grantRole} and {revokeRole}: this function's
     * purpose is to provide a mechanism for accounts to lose their privileges
     * if they are compromised (such as when a trusted device is misplaced).
     *
     * If the calling account had been revoked `role`, emits a {RoleRevoked}
     * event.
     *
     * Requirements:
     *
     * - the caller must be `account`.
     *
     * May emit a {RoleRevoked} event.
     */
    function renounceRole(bytes32 role, address account) public virtual override {
        require(account == _msgSender(), "AccessControl: can only renounce roles for self");

        _revokeRole(role, account);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * If `account` had not been already granted `role`, emits a {RoleGranted}
     * event. Note that unlike {grantRole}, this function doesn't perform any
     * checks on the calling account.
     *
     * May emit a {RoleGranted} event.
     *
     * [WARNING]
     * ====
     * This function should only be called from the constructor when setting
     * up the initial roles for the system.
     *
     * Using this function in any other way is effectively circumventing the admin
     * system imposed by {AccessControl}.
     * ====
     *
     * NOTE: This function is deprecated in favor of {_grantRole}.
     */
    function _setupRole(bytes32 role, address account) internal virtual {
        _grantRole(role, account);
    }

    /**
     * @dev Sets `adminRole` as ``role``'s admin role.
     *
     * Emits a {RoleAdminChanged} event.
     */
    function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
        bytes32 previousAdminRole = getRoleAdmin(role);
        _roles[role].adminRole = adminRole;
        emit RoleAdminChanged(role, previousAdminRole, adminRole);
    }

    /**
     * @dev Grants `role` to `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleGranted} event.
     */
    function _grantRole(bytes32 role, address account) internal virtual {
        if (!hasRole(role, account)) {
            _roles[role].members[account] = true;
            emit RoleGranted(role, account, _msgSender());
        }
    }

    /**
     * @dev Revokes `role` from `account`.
     *
     * Internal function without access restriction.
     *
     * May emit a {RoleRevoked} event.
     */
    function _revokeRole(bytes32 role, address account) internal virtual {
        if (hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, _msgSender());
        }
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[49] private __gap;
}

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

pragma solidity ^0.8.0;

import "./IAccessControlEnumerableUpgradeable.sol";
import "./AccessControlUpgradeable.sol";
import "../utils/structs/EnumerableSetUpgradeable.sol";
import "../proxy/utils/Initializable.sol";

/**
 * @dev Extension of {AccessControl} that allows enumerating the members of each role.
 */
abstract contract AccessControlEnumerableUpgradeable is Initializable, IAccessControlEnumerableUpgradeable, AccessControlUpgradeable {
    function __AccessControlEnumerable_init() internal onlyInitializing {
    }

    function __AccessControlEnumerable_init_unchained() internal onlyInitializing {
    }
    using EnumerableSetUpgradeable for EnumerableSetUpgradeable.AddressSet;

    mapping(bytes32 => EnumerableSetUpgradeable.AddressSet) private _roleMembers;

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

    /**
     * @dev Returns one of the accounts that have `role`. `index` must be a
     * value between 0 and {getRoleMemberCount}, non-inclusive.
     *
     * Role bearers are not sorted in any particular way, and their ordering may
     * change at any point.
     *
     * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
     * you perform all queries on the same block. See the following
     * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
     * for more information.
     */
    function getRoleMember(bytes32 role, uint256 index) public view virtual override returns (address) {
        return _roleMembers[role].at(index);
    }

    /**
     * @dev Returns the number of accounts that have `role`. Can be used
     * together with {getRoleMember} to enumerate all bearers of a role.
     */
    function getRoleMemberCount(bytes32 role) public view virtual override returns (uint256) {
        return _roleMembers[role].length();
    }

    /**
     * @dev Overload {_grantRole} to track enumerable memberships
     */
    function _grantRole(bytes32 role, address account) internal virtual override {
        super._grantRole(role, account);
        _roleMembers[role].add(account);
    }

    /**
     * @dev Overload {_revokeRole} to track enumerable memberships
     */
    function _revokeRole(bytes32 role, address account) internal virtual override {
        super._revokeRole(role, account);
        _roleMembers[role].remove(account);
    }

    /**
     * @dev This empty reserved space is put in place to allow future versions to add new
     * variables without shifting down storage in the inheritance chain.
     * See https://docs.openzeppelin.com/contracts/4.x/upgradeable#storage_gaps
     */
    uint256[49] private __gap;
}

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.0;

import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";

contract PendingOwnableUpgradeable is OwnableUpgradeable {
    address private _pendingOwner;

    event SetPendingOwner(address indexed pendingOwner);

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

    /**
     * @dev This function is disabled to in place of setPendingOwner()
     */
    function transferOwnership(
        address /*newOwner*/
    ) public view override onlyOwner {
        revert("PendingOwnable: MUST setPendingOwner()");
    }

    /**
     * @dev Sets an account as the pending owner (`newPendingOwner`).
     * Can only be called by the current owner.
     */
    function setPendingOwner(address newPendingOwner) public virtual onlyOwner {
        _pendingOwner = newPendingOwner;
        emit SetPendingOwner(_pendingOwner);
    }

    /**
     * @dev Transfers ownership to the pending owner
     * Can only be called by the pending owner.
     */
    function acceptOwnership() public virtual {
        require(msg.sender == _pendingOwner, "PendingOwnable: MUST be pendingOwner");
        _pendingOwner = address(0);
        _transferOwnership(msg.sender);
    }
}

{
  "remappings": [],
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "evmVersion": "london",
  "libraries": {},
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  }
}

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