MATIC Price: $1.01 (+2.52%)
Gas: 105 GWei

Contract Diff Checker

Contract Name:
HFunds

Contract Source Code:

// 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/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: 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

pragma solidity ^0.8.0;

abstract contract Config {
    // function signature of "postProcess()"
    bytes4 public constant POSTPROCESS_SIG = 0xc2722916;

    // The base amount of percentage function
    uint256 public constant PERCENTAGE_BASE = 1 ether;

    // Handler post-process type. Others should not happen now.
    enum HandlerType {
        Token,
        Custom,
        Others,
        Initial
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {LibCache} from "./lib/LibCache.sol";
import {LibStack} from "./lib/LibStack.sol";
import {IFurucomboRegistry} from "./interfaces/IFurucomboRegistry.sol";

/// @notice A cache structure composed by a bytes32 array
abstract contract Storage {
    using LibCache for mapping(bytes32 => bytes32);
    using LibStack for bytes32[];

    IFurucomboRegistry public registry;

    bytes32[] public stack;
    mapping(bytes32 => bytes32) public cache;

    // keccak256 hash of "msg.sender"
    // prettier-ignore
    bytes32 public constant MSG_SENDER_KEY = 0xb2f2618cecbbb6e7468cc0f2aa43858ad8d153e0280b22285e28e853bb9d453a;

    modifier isStackEmpty() {
        require(stack.length == 0, "Stack not empty");
        _;
    }

    modifier isInitialized() {
        require(_getSender() != address(0), "Sender is not initialized");
        _;
    }

    modifier isNotInitialized() {
        require(_getSender() == address(0), "Sender is initialized");
        _;
    }

    function _setSender() internal isNotInitialized {
        cache.setAddress(MSG_SENDER_KEY, msg.sender);
    }

    function _resetSender() internal {
        cache.setAddress(MSG_SENDER_KEY, address(0));
    }

    function _getSender() internal view returns (address) {
        return cache.getAddress(MSG_SENDER_KEY);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {SafeERC20, IERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import {IERC20Usdt} from "../../interfaces/IERC20Usdt.sol";
import {Config} from "../Config.sol";
import {Storage, LibStack} from "../Storage.sol";

abstract contract HandlerBase is Storage, Config {
    using SafeERC20 for IERC20;
    using LibStack for bytes32[];

    // prettier-ignore
    address public constant NATIVE_TOKEN_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
    // prettier-ignore
    address private constant MATIC_TOKEN = 0x0000000000000000000000000000000000001010;

    modifier validCallee(
        string memory functionName,
        address handler,
        address callee
    ) {
        _requireMsg(registry.handlerCalleeWhiteList(handler, callee), functionName, "invalid callee");
        _;
    }

    function postProcess() external payable virtual {
        revert("Invalid post process");
        /* Implementation template
        bytes4 sig = stack.getSig();
        if (sig == bytes4(keccak256(bytes("handlerFunction_1()")))) {
            // Do something
        } else if (sig == bytes4(keccak256(bytes("handlerFunction_2()")))) {
            bytes32 temp = stack.get();
            // Do something
        } else revert("Invalid post process");
        */
    }

    function _updateToken(address token) internal {
        _notMaticToken(token);
        stack.setAddress(token);
        // Ignore token type to fit old handlers
        // stack.setHandlerType(uint256(HandlerType.Token));
    }

    function _updateInitialToken(address token) internal {
        _notMaticToken(token);
        stack.setAddress(token);
        stack.setHandlerType(HandlerType.Initial);
    }

    function _updatePostProcess(bytes32[] memory params) internal {
        for (uint256 i = params.length; i > 0; i--) {
            stack.set(params[i - 1]);
        }
        stack.set(msg.sig);
        stack.setHandlerType(HandlerType.Custom);
    }

    function getContractName() public pure virtual returns (string memory);

    function _revertMsg(string memory functionName, string memory reason) internal pure {
        revert(string(abi.encodePacked(getContractName(), "_", functionName, ": ", reason)));
    }

    function _revertMsg(string memory functionName) internal pure {
        _revertMsg(functionName, "Unspecified");
    }

    function _requireMsg(
        bool condition,
        string memory functionName,
        string memory reason
    ) internal pure {
        if (!condition) _revertMsg(functionName, reason);
    }

    function _uint2String(uint256 n) internal pure returns (string memory) {
        if (n == 0) {
            return "0";
        } else {
            uint256 len = 0;
            for (uint256 temp = n; temp > 0; temp /= 10) {
                len++;
            }
            bytes memory str = new bytes(len);
            for (uint256 i = len; i > 0; i--) {
                str[i - 1] = bytes1(uint8(48 + (n % 10)));
                n /= 10;
            }
            return string(str);
        }
    }

    function _getBalance(address token, uint256 amount) internal view returns (uint256) {
        if (amount != type(uint256).max) {
            return amount;
        }

        // ETH case
        if (token == address(0) || token == NATIVE_TOKEN_ADDRESS) {
            return address(this).balance;
        }
        // ERC20 token case
        return IERC20(token).balanceOf(address(this));
    }

    function _tokenApprove(
        address token,
        address spender,
        uint256 amount
    ) internal {
        try IERC20Usdt(token).approve(spender, amount) {} catch {
            IERC20(token).safeApprove(spender, 0);
            IERC20(token).safeApprove(spender, amount);
        }
    }

    function _tokenApproveZero(address token, address spender) internal {
        if (IERC20Usdt(token).allowance(address(this), spender) > 0) {
            try IERC20Usdt(token).approve(spender, 0) {} catch {
                IERC20Usdt(token).approve(spender, 1);
            }
        }
    }

    // Do not support matic token (0x0000...1010)
    function _notMaticToken(address token) internal pure {
        require(token != MATIC_TOKEN, "Not support matic token");
    }

    function _notMaticToken(address[] memory tokens) internal pure {
        for (uint256 i = 0; i < tokens.length; i++) {
            require(tokens[i] != MATIC_TOKEN, "Not support matic token");
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.10;

import {SafeERC20, IERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import {HandlerBase} from "../HandlerBase.sol";

contract HFunds is HandlerBase {
    using SafeERC20 for IERC20;

    function getContractName() public pure override returns (string memory) {
        return "HFunds";
    }

    function updateTokens(address[] calldata tokens) external payable returns (uint256[] memory) {
        uint256[] memory balances = new uint256[](tokens.length);
        for (uint256 i = 0; i < tokens.length; i++) {
            address token = tokens[i];
            _notMaticToken(token);
            // Update involved token
            _updateInitialToken(token);
            balances[i] = _getBalance(token, type(uint256).max);
        }
        return balances;
    }

    function addFunds(address[] calldata tokens, uint256[] calldata amounts)
        external
        payable
        returns (uint256[] memory)
    {
        _requireMsg(tokens.length == amounts.length, "addFunds", "token and amount does not match");
        address sender = _getSender();
        for (uint256 i = 0; i < tokens.length; i++) {
            _notMaticToken(tokens[i]);
            IERC20(tokens[i]).safeTransferFrom(sender, address(this), amounts[i]);

            // Update involved token
            _updateToken(tokens[i]);
        }
        return amounts;
    }

    function returnFunds(address[] calldata tokens, uint256[] calldata amounts) external payable {
        _requireMsg(tokens.length == amounts.length, "returnFunds", "token and amount do not match");

        address payable receiver = payable(_getSender());
        for (uint256 i = 0; i < tokens.length; i++) {
            // token can't be matic token
            _notMaticToken(tokens[i]);

            uint256 amount = _getBalance(tokens[i], amounts[i]);
            if (amount > 0) {
                IERC20(tokens[i]).safeTransfer(receiver, amount);
            }
        }
    }

    function checkSlippage(address[] calldata tokens, uint256[] calldata amounts) external payable {
        _requireMsg(tokens.length == amounts.length, "checkSlippage", "token and amount do not match");

        for (uint256 i = 0; i < tokens.length; i++) {
            // token can't be matic token
            _notMaticToken(tokens[i]);

            uint256 balance = IERC20(tokens[i]).balanceOf(address(this));
            if (balance < amounts[i]) {
                string memory errMsg = string(abi.encodePacked("error: ", _uint2String(i), "_", _uint2String(balance)));
                _revertMsg("checkSlippage", errMsg);
            }
        }
    }

    function getBalance(address token) external payable returns (uint256) {
        return _getBalance(token, type(uint256).max);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IFurucomboRegistry {
    function handlers(address) external view returns (bytes32);

    function callers(address) external view returns (bytes32);

    function bannedAgents(address) external view returns (uint256);

    function fHalt() external view returns (bool);

    function isValidHandler(address handler) external view returns (bool);

    function isValidCaller(address handler) external view returns (bool);

    function handlerCalleeWhiteList(address handler, address callee) external view returns (bool);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

library LibCache {
    function set(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        bytes32 _value
    ) internal {
        _cache[_key] = _value;
    }

    function setAddress(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        address _value
    ) internal {
        _cache[_key] = bytes32(uint256(uint160(_value)));
    }

    function setUint256(
        mapping(bytes32 => bytes32) storage _cache,
        bytes32 _key,
        uint256 _value
    ) internal {
        _cache[_key] = bytes32(_value);
    }

    function getAddress(mapping(bytes32 => bytes32) storage _cache, bytes32 _key) internal view returns (address ret) {
        ret = address(uint160(uint256(_cache[_key])));
    }

    function getUint256(mapping(bytes32 => bytes32) storage _cache, bytes32 _key) internal view returns (uint256 ret) {
        ret = uint256(_cache[_key]);
    }

    function get(mapping(bytes32 => bytes32) storage _cache, bytes32 _key) internal view returns (bytes32 ret) {
        ret = _cache[_key];
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import {Config} from "../Config.sol";

library LibStack {
    function setAddress(bytes32[] storage _stack, address _input) internal {
        _stack.push(bytes32(uint256(uint160(_input))));
    }

    function set(bytes32[] storage _stack, bytes32 _input) internal {
        _stack.push(_input);
    }

    function setHandlerType(bytes32[] storage _stack, Config.HandlerType _input) internal {
        _stack.push(bytes12(uint96(_input)));
    }

    function getAddress(bytes32[] storage _stack) internal returns (address ret) {
        ret = address(uint160(uint256(peek(_stack))));
        _stack.pop();
    }

    function getSig(bytes32[] storage _stack) internal returns (bytes4 ret) {
        ret = bytes4(peek(_stack));
        _stack.pop();
    }

    function get(bytes32[] storage _stack) internal returns (bytes32 ret) {
        ret = peek(_stack);
        _stack.pop();
    }

    function peek(bytes32[] storage _stack) internal view returns (bytes32 ret) {
        uint256 length = _stack.length;
        require(length > 0, "stack empty");
        ret = _stack[length - 1];
    }

    function peek(bytes32[] storage _stack, uint256 _index) internal view returns (bytes32 ret) {
        uint256 length = _stack.length;
        require(length > 0, "stack empty");
        require(length > _index, "not enough elements in stack");
        ret = _stack[length - _index - 1];
    }
}

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

interface IERC20Usdt {
    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external;

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external;

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external;

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}

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