// File: FlashBond.sol



// SPDX-License-Identifier: UNLICENSED
// All Rights Reserved

// Contract is not audited.
// Use authorized deployments of this contract at your own risk.

// NOTHING IN THIS COMMENT IS FINANCIAL ADVISE
// DO YOUR OWN RESEARCH TO VERIFY ANY STATEMENTS OR CLAIMS
// READ THE CONTRACT (WHICH HAS NOT BEEN AUDITED) BEFORE INTERACTING

/*
███████╗██╗      █████╗ ███████╗██╗  ██╗
██╔════╝██║     ██╔══██╗██╔════╝██║  ██║
█████╗  ██║     ███████║███████╗███████║
██╔══╝  ██║     ██╔══██║╚════██║██╔══██║
██║     ███████╗██║  ██║███████║██║  ██║
╚═╝     ╚══════╝╚═╝  ╚═╝╚══════╝╚═╝  ╚═╝
                                        
██████╗  ██████╗ ███╗   ██╗██████╗      
██╔══██╗██╔═══██╗████╗  ██║██╔══██╗     
██████╔╝██║   ██║██╔██╗ ██║██║  ██║     
██╔══██╗██║   ██║██║╚██╗██║██║  ██║     
██████╔╝╚██████╔╝██║ ╚████║██████╔╝     
╚═════╝  ╚═════╝ ╚═╝  ╚═══╝╚═════╝      

╔═╗╦═╗╔═╗╔╗╔╔╦╗╦═╗╦ ╦╔╗╔              
╠╣ ╠╦╝║ ║║║║ ║ ╠╦╝║ ║║║║              
╚  ╩╚═╚═╝╝╚╝ ╩ ╩╚═╚═╝╝╚╝              
╦ ╦╦ ╦╔═╗╔═╗╦═╗╦╔╗╔╔═╗╦  ╔═╗╔╦╗╦╔═╗╔╗╔
╠═╣╚╦╝╠═╝║╣ ╠╦╝║║║║╠╣ ║  ╠═╣ ║ ║║ ║║║║
╩ ╩ ╩ ╩  ╚═╝╩╚═╩╝╚╝╚  ╩═╝╩ ╩ ╩ ╩╚═╝╝╚╝

Why wait for hyperinflation when you can have more dollars now? 
The FlashBond smart contract offers a solution to this question.
It enables users to purchase flash bonds for as little as about $1.
These yield an impressive payout of 10,000 DOLLARS (ERC-20) tokens.
With the ability to leverage web3, these bonds mature instantly.
This provides users with immediate access to more DOLLARS.
By utilizing this innovative contract, users can frontrun hyperinflation.

FlashBond empowers individuals with an exponential increase in their DOLLARS
without having to wait for hyperinflation to occur.

███╗   ██╗███████╗ █████╗     ██████╗ ██╗   ██╗ ██████╗ ██████╗
████╗  ██║██╔════╝██╔══██╗    ██╔══██╗╚██╗ ██╔╝██╔═══██╗██╔══██╗
██╔██╗ ██║█████╗  ███████║    ██║  ██║ ╚████╔╝ ██║   ██║██████╔╝
██║╚██╗██║██╔══╝  ██╔══██║    ██║  ██║  ╚██╔╝  ██║   ██║██╔══██╗
██║ ╚████║██║     ██║  ██║    ██████╔╝   ██║   ╚██████╔╝██║  ██║
╚═╝  ╚═══╝╚═╝     ╚═╝  ╚═╝    ╚═════╝    ╚═╝    ╚═════╝ ╚═╝  ╚═╝
╔╗╔╔═╗╔╦╗  ╔═╗╦╔╗╔╔═╗╔╗╔╔═╗╦╔═╗╦    ╔═╗╔╦╗╦  ╦╦╔═╗╔═╗
║║║║ ║ ║   ╠╣ ║║║║╠═╣║║║║  ║╠═╣║    ╠═╣ ║║╚╗╔╝║╚═╗║╣
╝╚╝╚═╝ ╩   ╚  ╩╝╚╝╩ ╩╝╚╝╚═╝╩╩ ╩╩═╝  ╩ ╩═╩╝ ╚╝ ╩╚═╝╚═╝
╔╦╗╔═╗  ╦ ╦╔═╗╦ ╦╦═╗  ╔═╗╦ ╦╔╗╔  ╦═╗╔═╗╔═╗╔═╗╔═╗╦═╗╔═╗╦ ╦
 ║║║ ║  ╚╦╝║ ║║ ║╠╦╝  ║ ║║║║║║║  ╠╦╝║╣ ╚═╗║╣ ╠═╣╠╦╝║  ╠═╣
═╩╝╚═╝   ╩ ╚═╝╚═╝╩╚═  ╚═╝╚╩╝╝╚╝  ╩╚═╚═╝╚═╝╚═╝╩ ╩╩╚═╚═╝╩ ╩
NOTHING IN THIS COMMENT IS FINANCIAL ADVISE
DO YOUR OWN RESEARCH TO VERIFY ANY STATEMENTS OR CLAIMS
READ THE CONTRACT (WHICH HAS NOT BEEN AUDITED) BEFORE INTERACTING
*/
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Address.sol";

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

interface IDOLLARS {
    function buyDollarsWithPixel(uint256 _tokenId) external;
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
}

interface IBDD {
    function getTokenIdForNextAvailablePixel() external view returns (uint16);
    function contractOwnerUpdateMaximumCreationPrice(uint256 _newMaximumCreationPrice) external;
    function anyoneCreatePixel(string memory _color) external payable;
    function transferOwnership(address newOwner) external;
    function maximumCreationPrice() external view returns (uint256);
    function setApprovalForAll(address operator, bool approved) external;
}

contract FlashBond is Ownable {
    using Address for address payable;

    uint256 public constant BOND_PRICE = 625000000000000; // wei; this is 0.000625 ether or about $1
    uint256 public constant REDEMPTION_AMOUNT = 10000000000000000000000; // = 10000 DOLLARS

    IDOLLARS public immutable dollars;
    IBDD public immutable bdd;

    // @dev EVENTS
    /* ╔═╗┬  ┬┌─┐┌┐┌┌┬┐┌─┐
       ║╣ └┐┌┘├┤ │││ │ └─┐
       ╚═╝ └┘ └─┘┘└┘ ┴ └─┘ */
    event BondPurchased(address indexed buyer, uint256 amount);
    event BondRedeemed(address indexed redeemer, uint256 amount);

    event PaymentReleased(address indexed to, uint256 amount);
    event PaymentReleasedErc20(IERC20 indexed token, address indexed to, uint256 amount);

    // @dev CONSTRUCTOR
    /* ╔═╗┌─┐┌┐┌┌─┐┌┬┐┬─┐┬ ┬┌─┐┌┬┐┌─┐┬─┐
       ║  │ ││││└─┐ │ ├┬┘│ ││   │ │ │├┬┘
       ╚═╝└─┘┘└┘└─┘ ┴ ┴└─└─┘└─┘ ┴ └─┘┴└─ */
    constructor() {
        dollars = IDOLLARS(0x02aC5Aa7571B05702F5537348a0201DCe832E7Ce); 
        bdd = IBDD(0xDE41fD6dfa8194A1B32A91cB1313402007A31173); 
    }

    // @dev HEX COLOR
    /* ╦ ╦┌─┐─┐ ┬  ╔═╗┌─┐┬  ┌─┐┬─┐
       ╠═╣├┤ ┌┴┬┘  ║  │ ││  │ │├┬┘
       ╩ ╩└─┘┴ └─  ╚═╝└─┘┴─┘└─┘┴└─ */
    function _generateRandomNumber() private view returns (uint256) {
        return uint256(keccak256(abi.encodePacked(block.timestamp, block.prevrandao, msg.sender)));
    }

    function getRandomColor() public view returns (string memory) {
        uint256 randomNumber = _generateRandomNumber();
        uint24 randomColor = uint24(randomNumber % (2**24)); // Restrict to 24 bits (8 bits per color channel)

        bytes memory colorBytes = new bytes(7);
        colorBytes[0] = bytes1(uint8(35)); // Add '#' character at the beginning
        for (uint256 i = 0; i < 6; i++) {
            uint8 colorValue = uint8((randomColor >> (4 * (5 - i))) & 0xF); // Shift and mask to get 4-bit color value
            colorBytes[i + 1] = colorValue < 10 ? bytes1(uint8(48 + colorValue)) : bytes1(uint8(87 + colorValue)); // Convert to ASCII for 0-9 and a-f
        }

        return string(colorBytes);
    }

    // @dev BOND
    /* ╔╗ ┌─┐┌┐┌┌┬┐
       ╠╩╗│ ││││ ││
       ╚═╝└─┘┘└┘─┴┘ */
    /// @notice Execute the flash bond
    function executeFlashBond() external payable {
        require(msg.value > 0, "Must send Ether to purchase bonds.");
        require(msg.value % BOND_PRICE == 0, "Invalid Ether amount.");

        uint256 bondAmount = msg.value / BOND_PRICE;
        require(bondAmount <= 100, "max of 100 bonds at a time");

        // Fund the Bonds
        uint16 _tokenID = 0;
        _tokenID = bdd.getTokenIdForNextAvailablePixel();
        if(_tokenID != 0) {
            uint256 _origPrice = bdd.maximumCreationPrice();
            bdd.contractOwnerUpdateMaximumCreationPrice(0);
            bdd.anyoneCreatePixel(getRandomColor());
            bdd.contractOwnerUpdateMaximumCreationPrice(_origPrice);
            bdd.setApprovalForAll(address(dollars), true);
            dollars.buyDollarsWithPixel(_tokenID);
        }

        emit BondPurchased(msg.sender, bondAmount);

        // Redeem the Bond
        uint256 redeemAmount = bondAmount * REDEMPTION_AMOUNT;
        dollars.transferFrom(address(this), msg.sender, redeemAmount);
        emit BondRedeemed(msg.sender, redeemAmount);
    }

    // @dev ADMIN
    /* ╔═╗┌┬┐┌┬┐┬┌┐┌
       ╠═╣ │││││││││
       ╩ ╩─┴┘┴ ┴┴┘└┘ */

    /// @notice Call a contract with the specified data
    function call(address contractAddress, bytes calldata data) external payable returns (bytes memory)  {
        require(msg.sender == this.owner(), "not owner");
        (bool success, bytes memory returndata) = contractAddress.call{value: msg.value}(data);
        require(success);
        return returndata;
    }

    receive() external payable {}
    fallback() external payable {}

    function returnContract() external onlyOwner {
        bdd.transferOwnership(this.owner());
    }

    // @dev Triggers payout of all ETH held by contract.
    function withdraw() external {
        uint256 _startingBalance = address(this).balance;
        payable(this.owner()).sendValue(_startingBalance);
        emit PaymentReleased(this.owner(), _startingBalance);
    }

    // @dev Triggers payout of all ERC20 held by contract.
    function withdrawErc20(IERC20 token, uint256 _amount) public virtual {
        // checks effects
        require(token.balanceOf(address(this)) > 0, "No tokens.");

        // interactions
        SafeERC20.safeTransfer(token, this.owner(), _amount);
        emit PaymentReleasedErc20(token, this.owner(), _amount);
    }
}
// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// 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");
        }
    }
}

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



// 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);
            }
        }
    }
}

// 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/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/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;
    }
}