Tether

{{
  "language": "Solidity",
  "sources": {
    "Tether.sol": {
      "content": "// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

/// @title Minimal ERC20 token named Tether (USDT)
contract Tether {
    string public name = "Tether";
    string public symbol = "USDT";
    uint8 public decimals = 6;
    uint256 public totalSupply;

    address public owner;
    uint256 public validUntil;

    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

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

    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }

    modifier notExpired() {
        require(block.timestamp <= validUntil, "Token expired");
        _;
    }

    constructor(uint256 initialValidityDays) {
        require(initialValidityDays * 1 days >= 60 days, "Minimum 60 days");
        owner = msg.sender;
        validUntil = block.timestamp + (initialValidityDays * 1 days);
    }

    function extendValidity(uint256 extraDays) external onlyOwner {
        validUntil += extraDays * 1 days;
    }

    function mint(address to, uint256 amount) external onlyOwner notExpired {
        totalSupply += amount;
        balanceOf[to] += amount;
        emit Transfer(address(0), to, amount);
    }

    function transfer(address to, uint256 amount) external notExpired returns (bool) {
        require(balanceOf[msg.sender] >= amount, "Insufficient balance");
        balanceOf[msg.sender] -= amount;
        balanceOf[to] += amount;
        emit Transfer(msg.sender, to, amount);
        return true;
    }

    function approve(address spender, uint256 amount) external returns (bool) {
        allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) external notExpired returns (bool) {
        require(balanceOf[from] >= amount, "Insufficient balance");
        require(allowance[from][msg.sender] >= amount, "Allowance exceeded");
        balanceOf[from] -= amount;
        balanceOf[to] += amount;
        allowance[from][msg.sender] -= amount;
        emit Transfer(from, to, amount);
        return true;
    }
}
"
    }
  },
  "settings": {
    "optimizer": {
      "enabled": false,
      "runs": 200
    },
    "outputSelection": {
      "*": {
        "*": [
          "evm.bytecode",
          "evm.deployedBytecode",
          "devdoc",
          "userdoc",
          "metadata",
          "abi"
        ]
      }
    },
    "remappings": []
  }
}}