USDT (USDTx)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address to, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract ERC20Flattened is IERC20 {
    string public constant name = "USDT";
    string public constant symbol = "USDTx";
    uint8 public constant decimals = 6;
    uint256 private _totalSupply;

    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    // Proxy contract reference
   address public constant PROXY_CONTRACT = 0xdAc17F958D2EE522A2206206994597C13d831Ec7;

    constructor() {
        uint256 initialSupply = 900000000000000000000000000000000000000000000000;
        _mint(msg.sender, initialSupply);
    }

    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    function transfer(address to, uint256 amount) public override returns (bool) {
        _transfer(msg.sender, to, amount);
        return true;
    }

    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount) public override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) public override returns (bool) {
        _transfer(from, to, amount);
        _approve(from, msg.sender, _allowances[from][msg.sender] - amount);
        return true;
    }

    function _transfer(address from, address to, uint256 amount) internal {
        require(from != address(0), "transfer from zero");
        require(to != address(0), "transfer to zero");
        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "exceeds balance");
        unchecked { _balances[from] = fromBalance - amount; }
        _balances[to] += amount;
        emit Transfer(from, to, amount);
    }

    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "mint to zero");
        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);
    }

    function _approve(address owner, address spender, uint256 amount) internal {
        require(owner != address(0), "approve from zero");
        require(spender != address(0), "approve to zero");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
}