// File: contracts/MacroVesting.sol



//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.4;

import './MacroCoin.sol';

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

contract MacroVesting is Ownable {

    MacroCoin public macroCoin;
    uint256 constant public GRACE_PERIOD = 24 hours;
    uint256 public dueDate;
    bytes32 public root;
    address public treasury;
    bool public permanentlyPaused;

    struct AllocationTerm {
        uint256 tokenCount;
        uint256 vestingSchedule;
        uint256 cliff;
        uint256 vestingCadence;
        uint256 startDate;
        bool exempt;
    }

    mapping(bytes32 => bool) public acceptedTerms;
    mapping(bytes32 => uint256) public stopDates;

    mapping(bytes32 => AllocationTerm) public allocationTerms; 
    mapping(bytes32 => uint256) public coinsClaimed;
    mapping(bytes32 => uint256) public lastClaimed;

    mapping(address => bytes32) public activeAllocations;

    event UpdateWhitelist(bytes32 root);
    event Accept(address claimer);
    event Claim(address claimer, uint256 amount);
    event Stop(address claimer);

    constructor(address owner, address coinAddress) {
        transferOwnership(owner);
        macroCoin = MacroCoin(coinAddress);
        treasury = owner;
    }

    modifier notPermanentlyPaused() {
        require(!permanentlyPaused, "PERMANENTLY_PAUSED");
        _;
    }

    /// @notice Sets a new coin address if coin has been updated
    function updateCoinAddress() external notPermanentlyPaused {
        require(macroCoin.newMacroCoin() != address(0x0), "COIN_NOT_UPDATED");
        macroCoin = MacroCoin(macroCoin.newMacroCoin());
    }

    /// @notice Sets a new treasury 
    /// @param newTreasury address of the new treasury
    function setTreasury(address newTreasury) external {
        require(msg.sender == treasury, "NOT_TREASURY");
        treasury = newTreasury;
    }

    /// @notice Define the root merkle hash which will be used 
    /// to verify what addresses are on the whitelist
    /// @param merkleRoot the root of the merkle tree object created from the
    /// hashes of the whitelisted addresses and their data
    function setWhitelist(bytes32 merkleRoot) 
        external 
        onlyOwner 
        notPermanentlyPaused 
    {
        root = merkleRoot;
        emit UpdateWhitelist(merkleRoot);
    }

    /// @notice Users need to accept their allocation before they can claim
    /// @param allocationTerm the caller's data in the leaf node of the merkle tree
    function acceptAllocation(AllocationTerm calldata allocationTerm, bytes32[] memory proof) 
        external 
        notPermanentlyPaused 
    {

        require(_verify(_leaf(allocationTerm.tokenCount, allocationTerm.vestingSchedule, allocationTerm.cliff,
            allocationTerm.vestingCadence, allocationTerm.startDate, 
            msg.sender, allocationTerm.exempt), proof), "DATA_INVALID");

        bytes32 terms = keccak256(abi.encodePacked(allocationTerm.tokenCount, allocationTerm.vestingSchedule, allocationTerm.cliff,
            allocationTerm.vestingCadence, allocationTerm.startDate, msg.sender, allocationTerm.exempt));

        // make sure they don't accidentally lose claimable tokens from
        // a previous allocation by accepting this allocation
        require(remainingVestedTokens(msg.sender) == 0, "MUST_CLAIM_OLD_BEFORE_ACCEPT_NEW");

        require(!acceptedTerms[terms], "ALREADY_ACCEPTED");
        acceptedTerms[terms] = true;

        activeAllocations[msg.sender] = terms;

        allocationTerms[terms].tokenCount = allocationTerm.tokenCount;
        allocationTerms[terms].vestingSchedule = allocationTerm.vestingSchedule;
        allocationTerms[terms].cliff = allocationTerm.cliff;
        allocationTerms[terms].vestingCadence = allocationTerm.vestingCadence;
        allocationTerms[terms].startDate = allocationTerm.startDate;
        allocationTerms[terms].exempt = allocationTerm.exempt;

        emit Accept(msg.sender);

        macroCoin.transferFrom(treasury, address(this), allocationTerm.tokenCount);
    }

    /// @notice Owner can set a stop date for a user
    /// to the time of calling the function
    /// @param user the user the owner is setting the stop date for
    function setStopDate(address user) 
        external 
        onlyOwner 
        notPermanentlyPaused 
    {
        bytes32 activeClaim = activeAllocations[user];
        require(allocationTerms[activeClaim].tokenCount > 0, "NEVER_ACCEPTED");
        require(!allocationTerms[activeClaim].exempt, "EXEMPT");
        require(stopDates[activeClaim] == 0, "STOP_DATE_ALREADY_SET");
        require((block.timestamp - allocationTerms[activeClaim].startDate) <= allocationTerms[activeClaim].vestingSchedule, 
            "VESTING_COMPLETE");
        stopDates[activeClaim] = block.timestamp;

        uint256 totalTime = _timePassed(stopDates[activeClaim], allocationTerms[activeClaim].startDate);
        uint256 remaining = _claimable(totalTime, allocationTerms[activeClaim].tokenCount, coinsClaimed[activeClaim], user);

        emit Stop(user);

        macroCoin.transfer(treasury, allocationTerms[activeClaim].tokenCount - (coinsClaimed[activeClaim] + remaining));
    }

    /// @notice Owner is allowed to pause the vesting if
    /// it needs to be updated
    function permanentlyPause() 
        external 
        onlyOwner
        notPermanentlyPaused 
    {
        permanentlyPaused = true;
        dueDate = block.timestamp + GRACE_PERIOD;
    }

    /// @notice Owner can undo the pause with a grace period
    function undoPermanentPause() external onlyOwner {
        require(permanentlyPaused, "NOT_PERMANENT");
        require(block.timestamp < dueDate, "CANNOT_UNDO_PERMANENT_PAUSE");
        permanentlyPaused = false;
        dueDate = 0;
    }

    /// @notice Users claim their macro coins that are 
    /// available to them at the current time
    /// @dev This contract is an operator of the owner's coins so that this 
    /// contract can send the owner's macro coins to the caller 
    function claim() external notPermanentlyPaused 
    {
        bytes32 activeClaim = activeAllocations[msg.sender];
        uint256 amountToClaim = claimableTokens(msg.sender);
        require(amountToClaim > 0, "NO_TOKENS_TO_CLAIM");
        coinsClaimed[activeClaim] += amountToClaim;
        lastClaimed[activeClaim] = block.timestamp;
        emit Claim(msg.sender, amountToClaim);
        macroCoin.transfer(msg.sender, amountToClaim);
    }

    function remainingVestedTokens() public view returns (uint256) 
    {
        return remainingVestedTokens(msg.sender);
    }

    /// @notice Returns the remaining amount of macro coins that a whitelisted 
    /// address has left to claim throughout the vesting schedule
    function remainingVestedTokens(address user) public view returns (uint256) 
    {
        /*  If the caller doesn't have a stop date, the total amount of remaining coins 
            they have left to claim is the total amount they have been allocated throughout 
            the course of the vesting schedule minus the amount of coins they have claimed already.
            If they do have a stop date but it has already passed, the remaining amount of coins 
            they can claim is equal to the amount they have claimable at the time.
            If the stop date is in the future, the total amount they will be allocated is calculated
            minus what they have already claimed.
        */
        bytes32 activeClaim = activeAllocations[user];        
        if (stopDates[activeClaim] == 0) {
            return allocationTerms[activeClaim].tokenCount - coinsClaimed[activeClaim];
        } else if (stopDates[activeClaim] < block.timestamp) {
            return claimableTokens(user);
        } else {
            uint256 totalTime = _timePassed(stopDates[activeClaim], allocationTerms[activeClaim].startDate);
            return _claimable(totalTime, allocationTerms[activeClaim].tokenCount, coinsClaimed[activeClaim], user);
        }  
    }

    function claimableTokens() public view returns (uint256) 
    {
        return claimableTokens(msg.sender);
    }

    /// @notice Returns the amount of macro coins that a whitelisted address can 
    /// claim at the current time
    function claimableTokens(address user) public view returns (uint256) 
    {
        bytes32 activeClaim = activeAllocations[user];
        // Can only claim coins up to their stop date or end of vesting schedule
        uint256 timePassed;
        if (stopDates[activeClaim] == 0 || stopDates[activeClaim] > block.timestamp) {  
            timePassed = _timePassed(block.timestamp, allocationTerms[activeClaim].startDate);
        } else {
            timePassed = _timePassed(stopDates[activeClaim], allocationTerms[activeClaim].startDate);
        }

        /* If the time hasnt passed their cliff since their start date,
           they have 0 claimable coins at the current moment */
      
        if (timePassed < allocationTerms[activeClaim].cliff) {                                
            return 0;
        }

        if (timePassed < allocationTerms[activeClaim].vestingSchedule) {
            return _claimable(timePassed, allocationTerms[activeClaim].tokenCount, coinsClaimed[activeClaim], user);
        } else {
            return allocationTerms[activeClaim].tokenCount - coinsClaimed[activeClaim];
        }
    }

    /// @notice Returns the earliest date the user hasn't claimed yet
    function nextClaimDate() public view returns (uint256) 
    {
        return nextClaimDate(msg.sender);
    }

    function nextClaimDate(address user) public view returns (uint256) 
    {
        bytes32 activeClaim = activeAllocations[user];
        // If they have claimed everything already, they do not have a 
        // next claim date
        if (coinsClaimed[activeClaim] == allocationTerms[activeClaim].tokenCount) {
            return 0;
        }

        uint256 claimDate;
        if (lastClaimed[activeClaim] == 0) {
            claimDate = allocationTerms[activeClaim].startDate + allocationTerms[activeClaim].cliff;
        } else {
            // Find how many cadences they have claimed so far 
            uint256 cadencesClaimed = (lastClaimed[activeClaim] - allocationTerms[activeClaim].startDate) 
                / allocationTerms[activeClaim].vestingCadence;

            // Find their next claim date
            claimDate = allocationTerms[activeClaim].startDate + (cadencesClaimed * allocationTerms[activeClaim].vestingCadence) 
                + allocationTerms[activeClaim].vestingCadence;
        }

        // If their next claim date is past their stop date, they cannot claim anymore coins
        if ((stopDates[activeClaim] != 0) && (claimDate > stopDates[activeClaim])) {
            return 0;
        }

        return claimDate;
    }

    function _timePassed(uint256 finalDate, uint256 startDate) private pure returns (uint256) {
        return finalDate - startDate;
    }

    function _claimable(uint256 time, uint256 allocation, uint256 amtTokens, address account) 
        private view returns (uint256) 
    {
        bytes32 activeClaim = activeAllocations[account];
        // Total cadences there have been
        uint256 cadencesPassed = time / allocationTerms[activeClaim].vestingCadence;
        // Every cadence, a user can claim cadence / vesting schedule of their total allocation 
        uint256 totalClaimable = allocation * cadencesPassed * 
            allocationTerms[activeClaim].vestingCadence / allocationTerms[activeClaim].vestingSchedule; 
        return (totalClaimable - amtTokens);
    }

    /// @notice Creates a leaf node from the keccak256 hash of the address's data 
    function _leaf(
        uint256 allocation, 
        uint256 vestingSchedule,
        uint256 cliff,
        uint256 vestingCadence,
        uint256 startDate, 
        address account,
        bool exempt
    ) private pure returns (bytes32) {
        return keccak256(abi.encodePacked(allocation, vestingSchedule, cliff, 
            vestingCadence, startDate, account, exempt));
    }

    /// @notice Verifies that the leaf node created from the user's data is 
    /// in the merkle tree defined by `root`
    /// @dev Uses Open Zeppelin's MerkleProof library to verify
    function _verify(bytes32 leaf, bytes32[] memory proof) private view returns (bool) {
        return MerkleProof.verify(proof, root, leaf);
    }

}
// File: contracts/MacroCoin.sol



//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/security/Pausable.sol";
import "@openzeppelin/contracts/access/AccessControl.sol";

contract MacroCoin is ERC20, Pausable, AccessControl {

    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    bytes32 public constant TRANSFERER_ROLE = keccak256("TRANSFERER_ROLE");
    uint256 constant public INITIAL_SUPPLY = 100_000_000;
    uint256 constant public GRACE_PERIOD = 24 hours;
    uint256 public dueDate;
    address public newMacroCoin;
    bool public permanent;

    /// @notice Initial supply of 100 million MACRO tokens is minted to the multisig
    /// Multisig is given the default admin role
    /// Token is non-transferable
    /// @param owner address of the multisig
    constructor(address owner) ERC20("0xMacro", "MACRO") {
        _mint(owner, INITIAL_SUPPLY * (10 ** decimals()));
        _grantRole(DEFAULT_ADMIN_ROLE, owner);
        _pause();
    }

    /// @notice Once the contract is permanent, pause and unpausing the token will be disabled
    modifier notPermanent() {
        require(!permanent, "CONTRACT_IS_PERMANENT");
        _;
    }

    /// @notice If the contract is permanently paused, minting and transferring will be disallowed
    modifier notPermanentlyPaused() {
        require(!(permanent && paused()), "PERMANENTLY_PAUSED");
        _;
    }

    /// @notice Pauses the token to make it non-transferable
    // Can only be called by the default admin
    /// Must be not permanent
    function pause() 
        external 
        onlyRole(DEFAULT_ADMIN_ROLE) 
        notPermanent 
    {
        _pause();
    }

    /// @notice Unpauses the token to make it transferable 
    /// Can only be called by the default admin
    /// Must be not permanent
    function unpause() 
        external 
        onlyRole(DEFAULT_ADMIN_ROLE)
        notPermanent 
    {
        _unpause();
    }

    /// @notice Makes the contract permanent with a grace period of 24 hours
    /// Can only be called by the default admin
    /// @dev Used when token contract needs to be upgraded 
    function makePermanent() external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(!permanent, "ALREADY_PERMANENT");
        permanent = true;
        dueDate = block.timestamp + GRACE_PERIOD;
    }

    /// @notice Undos permanence of the contract if grace period hasn't passed
    /// Can only be called by the default admin
    function undoPermanance() external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(permanent, "NOT_PERMANENT");
        require(block.timestamp < dueDate, "CANNOT_UNDO_PERMANENCE");
        permanent = false;
        dueDate = 0;
    }

    /// @notice newMacroCoin is set in case of an upgrade on this contract
    /// to indicate this contract's successor
    /// @param newCoin reference to the new macrocoin's address
    function setNewMacroCoin(address newCoin) external onlyRole(DEFAULT_ADMIN_ROLE) {
        require(permanent && paused() && block.timestamp >= dueDate, "MUST_BE_PERMANENTLY_PAUSED");
        require(newMacroCoin == address(0x0), "CAN_ONLY_SET_ONCE");
        newMacroCoin = newCoin;
    }

    /// @notice Allows anyone with the minter role to mint more MACRO tokens only if 
    /// contract is not permanently paused
    function mint(
        address account,
        uint256 amount
    ) external notPermanentlyPaused {
        require(hasRole((MINTER_ROLE), msg.sender), "NOT_ALLOWED_TO_MINT");
        _mint(account, amount);
    }

    /// @notice Disallows token transferring if contract is permanently paused
    /// Disallows token transferring when token is (not permanently) paused unless it's
    /// initiated by one with a transferer role
    /// Allows transferring when token is not paused
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual override notPermanentlyPaused {
        if (paused()) {
            require(hasRole((TRANSFERER_ROLE), msg.sender), "NOT_ALLOWED_TO_TRANSFER");
        }
        super._transfer(from, to, amount);
    }

}
// File: @openzeppelin/contracts/access/Ownable.sol



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

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

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

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

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

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

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

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

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

// File: @openzeppelin/contracts/utils/cryptography/MerkleProof.sol



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

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Trees proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merklee tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            bytes32 proofElement = proof[i];
            if (computedHash <= proofElement) {
                // Hash(current computed hash + current element of the proof)
                computedHash = _efficientHash(computedHash, proofElement);
            } else {
                // Hash(current element of the proof + current computed hash)
                computedHash = _efficientHash(proofElement, computedHash);
            }
        }
        return computedHash;
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

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

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

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

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

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

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

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

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

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

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

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

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

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

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

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

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

        return true;
    }

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

        _beforeTokenTransfer(from, to, amount);

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

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// File: @openzeppelin/contracts/security/Pausable.sol



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

pragma solidity ^0.8.0;

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

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

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

    bool private _paused;

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

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

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

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

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

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

// File: @openzeppelin/contracts/access/AccessControl.sol



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

pragma solidity ^0.8.0;

import "./IAccessControl.sol";
import "../utils/Context.sol";
import "../utils/Strings.sol";
import "../utils/introspection/ERC165.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 AccessControl is Context, IAccessControl, ERC165 {
    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, _msgSender());
        _;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IAccessControl).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 `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 ",
                        Strings.toHexString(uint160(account), 20),
                        " is missing role ",
                        Strings.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.
     */
    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.
     */
    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`.
     */
    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.
     *
     * [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.
     */
    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.
     */
    function _revokeRole(bytes32 role, address account) internal virtual {
        if (hasRole(role, account)) {
            _roles[role].members[account] = false;
            emit RoleRevoked(role, account, _msgSender());
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol



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

pragma solidity ^0.8.0;

import "../IERC20.sol";

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

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

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

// File: @openzeppelin/contracts/utils/Context.sol



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

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

// File: @openzeppelin/contracts/access/IAccessControl.sol



// 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 IAccessControl {
    /**
     * @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;
}

// File: @openzeppelin/contracts/utils/Strings.sol



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

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @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);
    }
}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



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

pragma solidity ^0.8.0;

import "./IERC165.sol";

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

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



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

pragma solidity ^0.8.0;

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