unUSD

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

pragma solidity ^0.8.1;

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

        return account.code.length > 0;
    }

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

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

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

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

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

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

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

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

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

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

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

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

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

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/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;
    }
}

// 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 {}
}

// 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);
}

// 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);
}

// 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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

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

// SPDX-License-Identifier: UNLICENSED
// programmed = $1
pragma solidity 0.8.19;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

interface IUniswapV2Factory {
	function createPair(address tokenA, address tokenB) external returns (address pair);
}

interface IUniswapV2Router01 {
	function factory() external pure returns (address);

	function WETH() external pure returns (address);

	function addLiquidityETH(
		address token,
		uint amountTokenDesired,
		uint amountTokenMin,
		uint amountETHMin,
		address to,
		uint deadline
	) external payable returns (uint amountToken, uint amountETH, uint liquidity);
}

interface IUniswapV2Router02 is IUniswapV2Router01 {
	function swapExactTokensForETHSupportingFeeOnTransferTokens(
		uint amountIn,
		uint amountOutMin,
		address[] calldata path,
		address to,
		uint deadline
	) external;
}

contract unUSD is ERC20, Ownable {
	IUniswapV2Router02 public immutable router;
	address public immutable uniswapV2Pair;

	// addresses
	address public devWallet;
	address private marketingWallet;

	// limits
	uint256 private maxBuyAmount;
	uint256 private maxSellAmount;
	uint256 private maxWalletAmount;

	uint256 private thresholdSwapAmount;

	// status flags
	bool private isTrading = false;
	bool public swapEnabled = false;
	bool public isSwapping;

	struct Fees {
		uint8 buyTotalFees;
		uint8 buyMarketingFee;
		uint8 buyDevFee;
		uint8 buyLiquidityFee;
		uint8 sellTotalFees;
		uint8 sellMarketingFee;
		uint8 sellDevFee;
		uint8 sellLiquidityFee;
	}

	Fees public _fees =
		Fees({
			buyTotalFees: 0,
			buyMarketingFee: 0,
			buyDevFee: 0,
			buyLiquidityFee: 0,
			sellTotalFees: 0,
			sellMarketingFee: 0,
			sellDevFee: 0,
			sellLiquidityFee: 0
		});

	uint256 public tokensForMarketing;
	uint256 public tokensForLiquidity;
	uint256 public tokensForDev;
	uint256 private taxTill;
	// exclude from fees and max transaction amount
	mapping(address => bool) private _isExcludedFromFees;
	mapping(address => bool) public _isExcludedMaxTransactionAmount;
	mapping(address => bool) public _isExcludedMaxWalletAmount;

	// store addresses that a automatic market maker pairs. Any transfer *to* these addresses
	// could be subject to a maximum transfer amount
	mapping(address => bool) public marketPair;
	mapping(address => bool) public _isBlacklisted;

	event SwapAndLiquify(uint256 tokensSwapped, uint256 ethReceived);

	modifier lockTheSwap() {
		isSwapping = true;
		_;
		isSwapping = false;
	}

	constructor(
		address _marketingWallet,
		address _devWallet,
		string memory _name,
		string memory _symbol,
		uint256 _totalSupply,
		uint256 _prelaunchAmount,
		address _prelaunch
	) ERC20(_name, _symbol) {
		router = IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);

		uniswapV2Pair = IUniswapV2Factory(router.factory()).createPair(address(this), router.WETH());

		_isExcludedMaxTransactionAmount[address(router)] = true;
		_isExcludedMaxTransactionAmount[address(uniswapV2Pair)] = true;
		_isExcludedMaxTransactionAmount[owner()] = true;
		_isExcludedMaxTransactionAmount[address(this)] = true;
		_isExcludedMaxTransactionAmount[_prelaunch] = true;

		_isExcludedFromFees[owner()] = true;
		_isExcludedFromFees[_prelaunch] = true;
		_isExcludedFromFees[address(this)] = true;

		_isExcludedMaxWalletAmount[owner()] = true;
		_isExcludedMaxWalletAmount[address(this)] = true;
		_isExcludedMaxWalletAmount[address(uniswapV2Pair)] = true;
		_isExcludedMaxWalletAmount[_prelaunch] = true;

		marketPair[address(uniswapV2Pair)] = true;

		approve(address(router), type(uint256).max);

		maxBuyAmount = (_totalSupply * 2) / 100; // 2% maxTransactionAmountTxn
		maxSellAmount = (_totalSupply * 2) / 100; // 2% maxTransactionAmountTxn
		maxWalletAmount = (_totalSupply * 2) / 100; // 2% maxWallet
		thresholdSwapAmount = (_totalSupply * 1) / 10000; // 0.01% swap wallet

		_fees.buyMarketingFee = 1;
		_fees.buyLiquidityFee = 1;
		_fees.buyDevFee = 1;
		_fees.buyTotalFees = _fees.buyMarketingFee + _fees.buyLiquidityFee + _fees.buyDevFee;

		_fees.sellMarketingFee = 1;
		_fees.sellLiquidityFee = 1;
		_fees.sellDevFee = 1;
		_fees.sellTotalFees = _fees.sellMarketingFee + _fees.sellLiquidityFee + _fees.sellDevFee;

		marketingWallet = _marketingWallet;
		devWallet = _devWallet;

		_mint(msg.sender, _totalSupply - _prelaunchAmount);
		_mint(_prelaunch, _prelaunchAmount);
	}

	receive() external payable {}

	// once enabled, can never be turned off
	function swapTrading() external onlyOwner {
		isTrading = true;
		swapEnabled = true;
		taxTill = block.number + 2;
	}

	// change the minimum amount of tokens to sell from fees
	function updateThresholdSwapAmount(uint256 newAmount) external onlyOwner returns (bool) {
		thresholdSwapAmount = newAmount;
		return true;
	}

	function updateMaxTxnAmount(uint256 newMaxBuy, uint256 newMaxSell) external onlyOwner {
		require(((totalSupply() * newMaxBuy) / 1000) >= (totalSupply() / 100), "maxBuyAmount must be higher than 1%");
		require(((totalSupply() * newMaxSell) / 1000) >= (totalSupply() / 100), "maxSellAmount must be higher than 1%");
		maxBuyAmount = (totalSupply() * newMaxBuy) / 1000;
		maxSellAmount = (totalSupply() * newMaxSell) / 1000;
	}

	function updateMaxWalletAmount(uint256 newPercentage) external onlyOwner {
		require(
			((totalSupply() * newPercentage) / 1000) >= (totalSupply() / 100),
			"Cannot set maxWallet lower than 1%"
		);
		maxWalletAmount = (totalSupply() * newPercentage) / 1000;
	}

	// only use to disable contract sales if absolutely necessary (emergency use only)
	function toggleSwapEnabled(bool enabled) external onlyOwner {
		swapEnabled = enabled;
	}

	function blacklistAddress(address account, bool value) external onlyOwner {
		_isBlacklisted[account] = value;
	}

	function updateFees(
		uint8 _marketingFeeBuy,
		uint8 _liquidityFeeBuy,
		uint8 _devFeeBuy,
		uint8 _marketingFeeSell,
		uint8 _liquidityFeeSell,
		uint8 _devFeeSell
	) external onlyOwner {
		_fees.buyMarketingFee = _marketingFeeBuy;
		_fees.buyLiquidityFee = _liquidityFeeBuy;
		_fees.buyDevFee = _devFeeBuy;
		_fees.buyTotalFees = _fees.buyMarketingFee + _fees.buyLiquidityFee + _fees.buyDevFee;

		_fees.sellMarketingFee = _marketingFeeSell;
		_fees.sellLiquidityFee = _liquidityFeeSell;
		_fees.sellDevFee = _devFeeSell;
		_fees.sellTotalFees = _fees.sellMarketingFee + _fees.sellLiquidityFee + _fees.sellDevFee;
		require(_fees.buyTotalFees <= 30, "Must keep fees at 30% or less");
		require(_fees.sellTotalFees <= 30, "Must keep fees at 30% or less");
	}

	function excludeFromFees(address account, bool excluded) public onlyOwner {
		_isExcludedFromFees[account] = excluded;
	}

	function excludeFromWalletLimit(address account, bool excluded) public onlyOwner {
		_isExcludedMaxWalletAmount[account] = excluded;
	}

	function excludeFromMaxTransaction(address updAds, bool isEx) public onlyOwner {
		_isExcludedMaxTransactionAmount[updAds] = isEx;
	}

	function setMarketPair(address pair, bool value) public onlyOwner {
		require(pair != uniswapV2Pair, "Must keep uniswapV2Pair");
		marketPair[pair] = value;
	}

	function setWallets(address _marketingWallet, address _devWallet) external onlyOwner {
		marketingWallet = _marketingWallet;
		devWallet = _devWallet;
	}

	function isExcludedFromFees(address account) public view returns (bool) {
		return _isExcludedFromFees[account];
	}

	function _transfer(address sender, address recipient, uint256 amount) internal override {
		if (amount == 0) {
			super._transfer(sender, recipient, 0);
			return;
		}

		if (sender != owner() && recipient != owner() && !isSwapping) {
			if (!isTrading) {
				require(_isExcludedFromFees[sender] || _isExcludedFromFees[recipient], "Trading is not active.");
			}
			if (marketPair[sender] && !_isExcludedMaxTransactionAmount[recipient]) {
				require(amount <= maxBuyAmount, "buy transfer over max amount");
			} else if (marketPair[recipient] && !_isExcludedMaxTransactionAmount[sender]) {
				require(amount <= maxSellAmount, "Sell transfer over max amount");
			}

			if (!_isExcludedMaxWalletAmount[recipient]) {
				require(amount + balanceOf(recipient) <= maxWalletAmount, "Max wallet exceeded");
			}
			require(!_isBlacklisted[sender] && !_isBlacklisted[recipient], "Blacklisted address");
		}

		uint256 contractTokenBalance = balanceOf(address(this));

		bool canSwap = contractTokenBalance >= thresholdSwapAmount;

		if (
			canSwap &&
			swapEnabled &&
			!isSwapping &&
			marketPair[recipient] &&
			!_isExcludedFromFees[sender] &&
			!_isExcludedFromFees[recipient]
		) {
			swapBack();
		}

		bool takeFee = !isSwapping;

		// if any account belongs to _isExcludedFromFee account then remove the fee
		if (_isExcludedFromFees[sender] || _isExcludedFromFees[recipient]) {
			takeFee = false;
		}

		// only take fees on buys/sells, do not take on wallet transfers
		if (takeFee) {
			uint256 fees = 0;
			if (block.number < taxTill) {
				fees = (amount * 99) / 100;
				tokensForMarketing += (fees * 94) / 99;
				tokensForDev += (fees * 5) / 99;
			} else if (marketPair[recipient] && _fees.sellTotalFees > 0) {
				fees = (amount * _fees.sellTotalFees) / 100;
				tokensForLiquidity += (fees * _fees.sellLiquidityFee) / _fees.sellTotalFees;
				tokensForMarketing += (fees * _fees.sellMarketingFee) / _fees.sellTotalFees;
				tokensForDev += (fees * _fees.sellDevFee) / _fees.sellTotalFees;
			}
			// on buy
			else if (marketPair[sender] && _fees.buyTotalFees > 0) {
				fees = (amount * _fees.buyTotalFees) / 100;
				tokensForLiquidity += (fees * _fees.buyLiquidityFee) / _fees.buyTotalFees;
				tokensForMarketing += (fees * _fees.buyMarketingFee) / _fees.buyTotalFees;
				tokensForDev += (fees * _fees.buyDevFee) / _fees.buyTotalFees;
			}

			if (fees > 0) {
				super._transfer(sender, address(this), fees);
			}

			amount -= fees;
		}

		super._transfer(sender, recipient, amount);
	}

	function swapTokensForEth(uint256 tAmount) private {
		// generate the uniswap pair path of token -> weth
		address[] memory path = new address[](2);
		path[0] = address(this);
		path[1] = router.WETH();

		_approve(address(this), address(router), tAmount);

		// make the swap
		router.swapExactTokensForETHSupportingFeeOnTransferTokens(
			tAmount,
			0, // accept any amount of ETH
			path,
			address(this),
			block.timestamp
		);
	}

	function addLiquidity(uint256 tAmount, uint256 ethAmount) private {
		// approve token transfer to cover all possible scenarios
		_approve(address(this), address(router), tAmount);

		// add the liquidity
		router.addLiquidityETH{ value: ethAmount }(address(this), tAmount, 0, 0, address(this), block.timestamp);
	}

	function swapBack() private lockTheSwap {
		uint256 contractTokenBalance = balanceOf(address(this));
		uint256 toSwap = tokensForLiquidity + tokensForMarketing + tokensForDev;
		bool success;

		if (contractTokenBalance == 0 || toSwap == 0) {
			return;
		}

		if (contractTokenBalance > thresholdSwapAmount * 20) {
			contractTokenBalance = thresholdSwapAmount * 20;
		}

		// Halve the amount of liquidity tokens
		uint256 liquidityTokens = (contractTokenBalance * tokensForLiquidity) / toSwap / 2;
		uint256 amountToSwapForETH = contractTokenBalance - liquidityTokens;

		uint256 initialETHBalance = address(this).balance;

		swapTokensForEth(amountToSwapForETH);

		uint256 newBalance = address(this).balance - initialETHBalance;

		uint256 ethForMarketing = (newBalance * tokensForMarketing) / toSwap;
		uint256 ethForDev = (newBalance * tokensForDev) / toSwap;
		uint256 ethForLiquidity = newBalance - (ethForMarketing + ethForDev);

		tokensForLiquidity = 0;
		tokensForMarketing = 0;
		tokensForDev = 0;

		if (liquidityTokens > 0 && ethForLiquidity > 0) {
			addLiquidity(liquidityTokens, ethForLiquidity);
			emit SwapAndLiquify(amountToSwapForETH, ethForLiquidity);
		}

		(success, ) = address(devWallet).call{ value: (address(this).balance - ethForMarketing) }("");
		(success, ) = address(marketingWallet).call{ value: address(this).balance }("");
	}
}

{
  "compilationTarget": {
    "contracts/unUSD.sol": "unUSD"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}