// File: contracts/CounterfeitMoney.sol



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

import "./utils/Ownable.sol";
import "./tokens/ERC20Permit.sol";
import "./interfaces/ICounterfeitMoney.sol";

error UnauthorizedWorker();

/// @title Counterfeit Money is just as good as "real" money
/// @dev ERC20 Token with dynamic supply, supporting EIP-2612 signatures for token approvals
contract CounterfeitMoney is ICounterfeitMoney, Ownable, ERC20Permit {
	/// @notice Mapping from an authorized minter address to their authorization state
	mapping(address => bool) public workers;

	constructor(address _owner) Ownable(_owner) ERC20Permit("CounterfeitMoney", "CNTF") {}

	/// @notice Sets addresses that are authorized to mint and burn tokens
	/// @dev Can only be called by the contract owner and emits a ShiftChange event
	/// @param _worker Address of contract that can mint and burn tokens
	/// @param _working Address of contract that can burn tokens
	function setWorker(address _worker, bool _working) external onlyOwner {
		workers[_worker] = _working;
		emit ShiftChange(_worker, _working);
	}

	/// @inheritdoc ICounterfeitMoney
	function print(address to, uint256 amount) external {
		// StakingHideout prints, CriminalRecords rewards
		if (!workers[msg.sender]) revert UnauthorizedWorker();
		_mint(to, amount);
	}

	/// @inheritdoc ICounterfeitMoney
	function burn(address from, uint256 amount) external {
		//CriminalRecords takes bribes
		if (!workers[msg.sender]) revert UnauthorizedWorker();
		_spendAllowance(from, msg.sender, amount);
		_burn(from, amount);
	}

	/// @notice Emitted when new a minter / burner is set
	/// @param _worker New address of contract that can mint and burn tokens
	/// @param _working Whether access is granted or revoked
	event ShiftChange(address indexed _worker, bool _working);
}

// File: contracts/utils/Ownable.sol



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

pragma solidity ^0.8.0;

error CallerNotTheOwner();
error NewOwnerIsZeroAddress();

/**
 * @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 {
	address private _contractOwner;

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

	/**
	 * @dev Initializes the given owner as the initial owner.
	 */
	constructor(address contractOwner_) {
		_transferOwnership(contractOwner_);
	}

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

	/**
	 * @dev Throws if called by any account other than the owner.
	 */
	modifier onlyOwner() {
		if (owner() != msg.sender) revert CallerNotTheOwner();
		_;
	}

	/**
	 * @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 {
		if (newOwner == address(0)) revert NewOwnerIsZeroAddress();
		_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 = _contractOwner;
		_contractOwner = newOwner;
		emit OwnershipTransferred(oldOwner, newOwner);
	}
}

// File: contracts/tokens/ERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-ERC20Permit.sol)

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol";
import "./ERC20.sol";
import "../utils/EIP712.sol";
import "../utils/ECDSA.sol";

error PermitToOwner();
error PermitDeadLineExpired();

/**
 * @dev Implementation 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.
 *
 * _Available since v3.4._
 */
abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
	mapping(address => uint256) private _nonces;

	// solhint-disable-next-line var-name-mixedcase
	bytes32 private immutable _PERMIT_TYPEHASH =
		keccak256(
			"Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
		);

	/**
	 * @dev Initializes the {EIP712} domain separator using the `name` parameter, and setting `version` to `"1"`.
	 *
	 * It's a good idea to use the same `name` that is defined as the ERC20 token name.
	 */
	constructor(string memory _name, string memory _symbol)
		ERC20(_name, _symbol)
		EIP712(_name, "1")
	{}

	/**
	 * @dev See {IERC20Permit-permit}.
	 */
	function permit(
		address owner,
		address spender,
		uint256 value,
		uint256 deadline,
		uint8 v,
		bytes32 r,
		bytes32 s
	) public virtual override {
		if (spender == owner) revert PermitToOwner();
		if (block.timestamp > deadline) revert PermitDeadLineExpired();

		bytes32 structHash = keccak256(
			abi.encode(_PERMIT_TYPEHASH, owner, spender, value, _useNonce(owner), deadline)
		);

		bytes32 hash = _hashTypedDataV4(structHash);

		address signer = ECDSA.recover(hash, v, r, s);
		if (signer != owner) revert InvalidSignature();

		_approve(owner, spender, value);
	}

	/**
	 * @dev See {IERC20Permit-nonces}.
	 */
	function nonces(address owner) public view virtual override returns (uint256) {
		return _nonces[owner];
	}

	/**
	 * @dev See {IERC20Permit-DOMAIN_SEPARATOR}.
	 */
	// solhint-disable-next-line func-name-mixedcase
	function DOMAIN_SEPARATOR() external view override returns (bytes32) {
		return _domainSeparatorV4();
	}

	/**
	 * @dev "Consume a nonce": return the current value and increment.
	 *
	 * _Available since v4.1._
	 */
	function _useNonce(address owner) internal virtual returns (uint256 current) {
		current = _nonces[owner];
		unchecked {
			_nonces[owner] = current + 1;
		}
	}
}

// File: contracts/interfaces/ICounterfeitMoney.sol



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

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol";

/// @title Counterfeit Money is just as good as "real" money
/// @dev ERC20 Token with dynamic supply, supporting EIP-2612 signatures for token approvals
interface ICounterfeitMoney is IERC20, IERC20Permit {
	/// @notice Prints and sends a certain amount of CounterfeitMoney to an user
	/// @dev Emits an Transfer event from zero-address
	/// @param to The address receiving the freshly printed money
	/// @param amount The amount of money that will be printed
	function print(address to, uint256 amount) external;

	/// @notice Burns and removes an approved amount of CounterfeitMoney from an user
	/// @dev Emits an Transfer event to zero-address
	/// @param from The address losing the CounterfeitMoney
	/// @param amount The amount of money that will be removed from the account
	function burn(address from, uint256 amount) external;
}

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



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

pragma solidity ^0.8.0;

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

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

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

// File: contracts/tokens/ERC20.sol



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

pragma solidity ^0.8.0;

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

error DecreasingAllowanceBelowZero();
error TransferToZeroAddress();
error TransferFromZeroAddress();
error TransferAmountExceedsBalance();
error MintToZeroAddress();
error BurnFromZeroAddress();
error BurnAmountExceedsBalance();
error ApproveFromZeroAddress();
error ApproveToZeroAddress();
error InsufficientAllowance();

/**
 * @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 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) {
		_transfer(msg.sender, 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) {
		_approve(msg.sender, 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) {
		_spendAllowance(from, msg.sender, 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 = msg.sender;
		_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 = msg.sender;
		uint256 currentAllowance = _allowances[owner][spender];
		if (currentAllowance < subtractedValue) revert DecreasingAllowanceBelowZero();
		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 {
		if (from == address(0)) revert TransferFromZeroAddress();
		if (to == address(0)) revert TransferToZeroAddress();

		_beforeTokenTransfer(from, to, amount);

		uint256 fromBalance = _balances[from];
		if (fromBalance < amount) revert TransferAmountExceedsBalance();
		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 {
		if (account == address(0)) revert MintToZeroAddress();

		_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 {
		if (account == address(0)) revert BurnFromZeroAddress();

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

		uint256 accountBalance = _balances[account];
		if (accountBalance < amount) revert BurnAmountExceedsBalance();
		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 {
		if (owner == address(0)) revert ApproveFromZeroAddress();
		if (spender == address(0)) revert ApproveToZeroAddress();

		_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) {
			if (currentAllowance < amount) revert InsufficientAllowance();
			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: contracts/utils/EIP712.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/cryptography/draft-EIP712.sol)

pragma solidity ^0.8.0;

import "./ECDSA.sol";

/**
 * @dev https://eips.ethereum.org/EIPS/eip-712[EIP 712] is a standard for hashing and signing of typed structured data.
 *
 * The encoding specified in the EIP is very generic, and such a generic implementation in Solidity is not feasible,
 * thus this contract does not implement the encoding itself. Protocols need to implement the type-specific encoding
 * they need in their contracts using a combination of `abi.encode` and `keccak256`.
 *
 * This contract implements the EIP 712 domain separator ({_domainSeparatorV4}) that is used as part of the encoding
 * scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA
 * ({_hashTypedDataV4}).
 *
 * The implementation of the domain separator was designed to be as efficient as possible while still properly updating
 * the chain id to protect against replay attacks on an eventual fork of the chain.
 *
 * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
 * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
 *
 * _Available since v3.4._
 */
abstract contract EIP712 {
	/* solhint-disable var-name-mixedcase */
	// Cache the domain separator as an immutable value, but also store the chain id that it corresponds to, in order to
	// invalidate the cached domain separator if the chain id changes.
	bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
	uint256 private immutable _CACHED_CHAIN_ID;
	address private immutable _CACHED_THIS;

	bytes32 private immutable _HASHED_NAME;
	bytes32 private immutable _HASHED_VERSION;
	bytes32 private immutable _TYPE_HASH;

	/* solhint-enable var-name-mixedcase */

	/**
	 * @dev Initializes the domain separator and parameter caches.
	 *
	 * The meaning of `name` and `version` is specified in
	 * https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator[EIP 712]:
	 *
	 * - `name`: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.
	 * - `version`: the current major version of the signing domain.
	 *
	 * NOTE: These parameters cannot be changed except through a xref:learn::upgrading-smart-contracts.adoc[smart
	 * contract upgrade].
	 */
	constructor(string memory name, string memory version) {
		bytes32 hashedName = keccak256(bytes(name));
		bytes32 hashedVersion = keccak256(bytes(version));
		bytes32 typeHash = keccak256(
			"EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
		);
		_HASHED_NAME = hashedName;
		_HASHED_VERSION = hashedVersion;
		_CACHED_CHAIN_ID = block.chainid;
		_CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(typeHash, hashedName, hashedVersion);
		_CACHED_THIS = address(this);
		_TYPE_HASH = typeHash;
	}

	/**
	 * @dev Returns the domain separator for the current chain.
	 */
	function _domainSeparatorV4() internal view returns (bytes32) {
		if (address(this) == _CACHED_THIS && block.chainid == _CACHED_CHAIN_ID) {
			return _CACHED_DOMAIN_SEPARATOR;
		} else {
			return _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME, _HASHED_VERSION);
		}
	}

	function _buildDomainSeparator(
		bytes32 typeHash,
		bytes32 nameHash,
		bytes32 versionHash
	) private view returns (bytes32) {
		return
			keccak256(abi.encode(typeHash, nameHash, versionHash, block.chainid, address(this)));
	}

	/**
	 * @dev Given an already https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct[hashed struct], this
	 * function returns the hash of the fully encoded EIP712 message for this domain.
	 *
	 * This hash can be used together with {ECDSA-recover} to obtain the signer of a message. For example:
	 *
	 * ```solidity
	 * bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
	 *     keccak256("Mail(address to,string contents)"),
	 *     mailTo,
	 *     keccak256(bytes(mailContents))
	 * )));
	 * address signer = ECDSA.recover(digest, signature);
	 * ```
	 */
	function _hashTypedDataV4(bytes32 structHash) internal view virtual returns (bytes32) {
		return ECDSA.toTypedDataHash(_domainSeparatorV4(), structHash);
	}
}

// File: contracts/utils/ECDSA.sol



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

pragma solidity ^0.8.0;

error InvalidSignature();
error InvalidSignatureLength();
error InvalidSignatureSValue();
error InvalidSignatureVValue();

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
	/**
	 * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
	 * `r` and `s` signature fields separately.
	 *
	 * _Available since v4.3._
	 */
	function recover(
		bytes32 hash,
		uint8 v,
		bytes32 r,
		bytes32 s
	) internal pure returns (address) {
		// EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
		// unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
		// the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
		// signatures from current libraries generate a unique signature with an s-value in the lower half order.
		//
		// If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
		// with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
		// vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
		// these malleable signatures as well.
		if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
			revert InvalidSignatureSValue();
		}
		if (v != 27 && v != 28) {
			revert InvalidSignatureVValue();
		}

		// If the signature is valid (and not malleable), return the signer address
		address signer = ecrecover(hash, v, r, s);
		if (signer == address(0)) {
			revert InvalidSignature();
		}

		return signer;
	}

	/**
	 * @dev Returns an Ethereum Signed Typed Data, created from a
	 * `domainSeparator` and a `structHash`. This produces hash corresponding
	 * to the one signed with the
	 * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
	 * JSON-RPC method as part of EIP-712.
	 *
	 * See {recover}.
	 */
	function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash)
		internal
		pure
		returns (bytes32)
	{
		return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
	}
}

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



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

pragma solidity ^0.8.0;

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

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

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

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

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

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

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

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

// File: @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);
}