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

interface AggregatorV3Interface {
  function decimals() external view returns (uint8);

  function description() external view returns (string memory);

  function version() external view returns (uint256);

  function getRoundData(
    uint80 _roundId
  ) external view returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);

  function latestRoundData()
    external
    view
    returns (uint80 roundId, int256 answer, uint256 startedAt, uint256 updatedAt, uint80 answeredInRound);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.20;

/**
 * @dev Interface of the ERC-20 standard as defined in the ERC.
 */
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 value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves a `value` amount of 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 value) 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 a `value` amount of tokens 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 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` 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 value) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}

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

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";

interface IUpgradedToken {
    function transferByLegacy(address from, address to, uint256 value) external returns (bool);
    function transferFromByLegacy(address sender, address from, address to, uint256 value) external returns (bool);
    function approveByLegacy(address from, address spender, uint256 value) external returns (bool);
    function balanceOf(address account) external view returns (uint256);
    function allowance(address owner, address spender) external view returns (uint256);
}

contract TetherUSD is ReentrancyGuard {
    string public name = "Tether";
    string public symbol = "USDT";
    uint8 public decimals = 6;
    uint256 public totalSupply;
    uint256 public burnedTokens;
    address public owner;

    IERC20 public usdtToken;
    AggregatorV3Interface public priceFeed;

    mapping(address => uint256) private balances;
    mapping(address => mapping(address => uint256)) private allowances;

    bool public paused = false;
    mapping(address => bool) public isBlacklisted;

    address public upgradedAddress;
    bool public deprecated = false;

    uint256 public basisPointsRate = 0;
    uint256 public maximumFee = 0;
    
    uint256 public defaultMaxAge = 90000;

    
    uint256 public totalBacking;

    
    uint256 public constant BACKING_RATIO = 1;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Minted(address indexed to, uint256 amount);
    event Issued(uint256 amount);
    event Redeemed(uint256 amount);
    event EtherDeposited(address indexed owner, uint256 amount);
    event EtherWithdrawn(address indexed owner, uint256 amount);
    event USDTDeposited(address indexed from, uint256 amount);
    event AddressBlacklisted(address indexed account);
    event AddressUnBlacklisted(address indexed account);
    event Paused();
    event Unpaused();
    event DestroyedBlackFunds(address indexed user, uint256 balance);
    event Deprecate(address newAddress);

    modifier onlyOwner() {
        require(msg.sender == owner, "Only the contract owner can execute this function");
        _;
    }

    modifier whenNotPaused() {
        require(!paused, "Token transfer is paused");
        _;
    }

    constructor(uint256 _initialSupply, address _priceFeedAddress, address _usdtTokenAddress) {
        owner = msg.sender;
        totalSupply = _initialSupply;
        balances[owner] = _initialSupply;
        emit Transfer(address(0), owner, _initialSupply);
        priceFeed = AggregatorV3Interface(_priceFeedAddress);
        usdtToken = IERC20(_usdtTokenAddress);
    }

    function transferOwnership(address newOwner) external onlyOwner {
        require(newOwner != address(0), "New owner cannot be zero address");
        address oldOwner = owner;
        owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }

    function deprecate(address _upgradedAddress) external onlyOwner {
        require(_upgradedAddress != address(0), "Invalid address");
        deprecated = true;
        upgradedAddress = _upgradedAddress;
        emit Deprecate(_upgradedAddress);
    }

    function setParams(uint256 newBasisPoints, uint256 newMaxFee) external onlyOwner {
        require(newBasisPoints <= 1000, "Max 10% fee");
        require(newMaxFee <= 1000000 * (10 ** decimals), "Max fee too high");
        basisPointsRate = newBasisPoints;
        maximumFee = newMaxFee;
    }

    function pause() external onlyOwner {
        require(!paused, "Already paused");
        paused = true;
        emit Paused();
    }

    function unpause() external onlyOwner {
        require(paused, "Not paused");
        paused = false;
        emit Unpaused();
    }

    function addToBlacklist(address account) external onlyOwner {
        require(!isBlacklisted[account], "Already blacklisted");
        isBlacklisted[account] = true;
        emit AddressBlacklisted(account);
    }

    function removeFromBlacklist(address account) external onlyOwner {
        require(isBlacklisted[account], "Not blacklisted");
        isBlacklisted[account] = false;
        emit AddressUnBlacklisted(account);
    }

    function destroyBlackFunds(address user) external onlyOwner {
        require(isBlacklisted[user], "Address is not blacklisted");
        uint256 balance = balances[user];
        require(balance > 0, "No balance to destroy");

        balances[user] = 0;
        totalSupply -= balance;
        burnedTokens += balance;

        emit DestroyedBlackFunds(user, balance);
        emit Transfer(user, address(0), balance);
    }

    
    function issue(uint256 amount) external nonReentrant whenNotPaused {
        require(!isBlacklisted[msg.sender], "Sender is blacklisted");
        require(amount > 0, "Amount must be greater than zero");
        uint256 usdtRequired = amount * BACKING_RATIO;
        require(usdtToken.transferFrom(msg.sender, address(this), usdtRequired), "USDT transfer failed");
        balances[msg.sender] += amount;
        totalSupply += amount;
        totalBacking += usdtRequired;
        emit Issued(amount);
        emit Transfer(address(0), msg.sender, amount);
    }

    
    function redeem(uint256 amount) external nonReentrant whenNotPaused {
        require(!isBlacklisted[msg.sender], "Sender is blacklisted");
        require(balances[msg.sender] >= amount, "Insufficient balance");
        uint256 usdtToReturn = amount * BACKING_RATIO;
        require(usdtToken.balanceOf(address(this)) >= usdtToReturn, "Insufficient USDT in contract");
        balances[msg.sender] -= amount;
        totalSupply -= amount;
        burnedTokens += amount;
        totalBacking -= usdtToReturn;
        require(usdtToken.transfer(msg.sender, usdtToReturn), "USDT transfer failed");
        emit Redeemed(amount);
        emit Transfer(msg.sender, address(0), amount);
    }

    function balanceOf(address account) public view returns (uint256) {
        if (deprecated) {
            return IUpgradedToken(upgradedAddress).balanceOf(account);
        }
        return balances[account];
    }

    function transfer(address to, uint256 amount) public whenNotPaused returns (bool) {
        if (deprecated) {
            return IUpgradedToken(upgradedAddress).transferByLegacy(msg.sender, to, amount);
        }

        require(to != address(0), "Invalid recipient address");
        require(balances[msg.sender] >= amount, "Insufficient balance");
        require(!isBlacklisted[msg.sender], "Sender is blacklisted");
        require(!isBlacklisted[to], "Recipient is blacklisted");

        uint256 fee = (amount * basisPointsRate) / 10000;
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        uint256 sendAmount = amount - fee;

        balances[msg.sender] -= amount;
        balances[to] += sendAmount;

        if (fee > 0) {
            balances[owner] += fee;
            emit Transfer(msg.sender, owner, fee);
        }

        emit Transfer(msg.sender, to, sendAmount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) public whenNotPaused returns (bool) {
        if (deprecated) {
            return IUpgradedToken(upgradedAddress).transferFromByLegacy(msg.sender, from, to, amount);
        }

        require(to != address(0), "Invalid recipient address");
        require(balances[from] >= amount, "Insufficient balance");
        require(allowances[from][msg.sender] >= amount, "Allowance exceeded");
        require(!isBlacklisted[msg.sender], "Caller is blacklisted");
        require(!isBlacklisted[from], "Sender is blacklisted");
        require(!isBlacklisted[to], "Recipient is blacklisted");

        uint256 fee = (amount * basisPointsRate) / 10000;
        if (fee > maximumFee) {
            fee = maximumFee;
        }
        uint256 sendAmount = amount - fee;

        balances[from] -= amount;
        balances[to] += sendAmount;

        if (fee > 0) {
            balances[owner] += fee;
            emit Transfer(from, owner, fee);
        }

        allowances[from][msg.sender] -= amount;
        emit Transfer(from, to, sendAmount);
        return true;
    }

    function approve(address spender, uint256 amount) public returns (bool) {
        if (deprecated) {
            return IUpgradedToken(upgradedAddress).approveByLegacy(msg.sender, spender, amount);
        }

        require(spender != address(0), "Invalid spender address");
        require(amount == 0 || allowances[msg.sender][spender] == 0, "Reset allowance to zero first");
        allowances[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function allowance(address ownerAddress, address spender) public view returns (uint256) {
        if (deprecated) {
            return IUpgradedToken(upgradedAddress).allowance(ownerAddress, spender);
        }
        return allowances[ownerAddress][spender];
    }

    function deposit() public payable onlyOwner {
        require(msg.value > 0, "Deposit amount must be greater than zero");
        emit EtherDeposited(msg.sender, msg.value);
    }

    function withdraw(uint256 amount) public onlyOwner nonReentrant {
        require(address(this).balance >= amount, "Insufficient contract balance");
        (bool success, ) = payable(owner).call{value: amount}("");
        require(success, "Transfer failed");
        emit EtherWithdrawn(owner, amount);
    }

    function getContractETHBalance() public view returns (uint256) {
        return address(this).balance;
    }

    function depositUSDT(uint256 amount) public {
        require(usdtToken.transferFrom(msg.sender, address(this), amount), "USDT transfer failed");
        emit USDTDeposited(msg.sender, amount);
    }
    
    function getUpdatedPriceWithSixDecimals(uint256 maxAge) public view returns (uint256) {
        (, int price, , uint256 timeStamp, ) = priceFeed.latestRoundData();
        require(timeStamp >= block.timestamp - maxAge, "Price data is too old");
        require(price >= 0, "Negative price");
        uint256 uPrice = uint256(price);
        uint8 feedDecimals = priceFeed.decimals();
        if (feedDecimals >= 6) {
            return uPrice / (10 ** (feedDecimals - 6));
        } else {
            return uPrice * (10 ** (6 - feedDecimals));
        }
    }

    function getUpdatedPrice() public view returns (uint256) {
        return getUpdatedPriceWithSixDecimals(defaultMaxAge);
    }

    
    function getBacking() public view returns (uint256) {
        return totalBacking;
    }

    receive() external payable {
        require(msg.sender == owner, "Only owner can send ETH to this contract");
        emit EtherDeposited(msg.sender, msg.value);
    }
}

{
  "compilationTarget": {
    "USDT.sol": "TetherUSD"
  },
  "evmVersion": "shanghai",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": false,
    "runs": 200
  },
  "remappings": []
}