Tether USD (USDT)

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

/*
  تعليمي: ERC20 بسيط مع ملكية (Ownable) وسكّ (mint) مبدئي.
  ⚠️ لا تستخدم اسم/رمز يوهم المستخدمين أنه USDT الرسمي.
*/

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
}

contract Ownable is Context {
    address private _owner;
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
    constructor() {
        _owner = _msgSender();
        emit OwnershipTransferred(address(0), _owner);
    }
    function owner() public view returns (address) { return _owner; }
    modifier onlyOwner() { require(_owner == _msgSender(), "Ownable: caller is not the owner"); _; }
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is zero");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
}

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 USDT is Context, IERC20, Ownable {
    string public name = "Tether USD";
    string public symbol = "USDT";
    uint8 public decimals = 18;

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


    event Mint(address indexed to, uint256 amount);
    event Burn(address indexed from, uint256 amount);

    constructor(string memory _name, string memory _symbol, uint256 initialSupply, address receiver) {
        name = _name;
        symbol = _symbol;
        if (initialSupply > 0) {
            _mint(receiver, 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(_msgSender(), 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(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) public override returns (bool) {
        uint256 currentAllowance = _allowances[from][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        _transfer(from, to, amount);
        _approve(from, _msgSender(), currentAllowance - amount);
        return true;
    }

    // وظائف اختيارية
    function mint(address to, uint256 amount) public onlyOwner {
        _mint(to, amount);
    }
    function burn(uint256 amount) public {
        _burn(_msgSender(), amount);
    }

    // داخلي
    function _transfer(address from, address to, uint256 amount) internal {
        require(from != address(0), "ERC20: transfer from zero");
        require(to != address(0), "ERC20: transfer to zero");
        require(_balances[from] >= amount, "ERC20: balance too low");
        _balances[from] -= amount;
        _balances[to] += amount;
        emit Transfer(from, to, amount);
    }
    function _mint(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: mint to zero");
        _totalSupply += amount;
        _balances[account] += amount;
        emit Mint(account, amount);
        emit Transfer(address(0), account, amount);
    }
    function _burn(address account, uint256 amount) internal {
        require(account != address(0), "ERC20: burn from zero");
        require(_balances[account] >= amount, "ERC20: burn amount exceeds balance");
        _balances[account] -= amount;
        _totalSupply -= amount;
        emit Burn(account, amount);
        emit Transfer(account, address(0), amount);
    }
    function _approve(address owner_, address spender, uint256 amount) internal {
        require(owner_ != address(0), "ERC20: approve from zero");
        require(spender != address(0), "ERC20: approve to zero");
        _allowances[owner_][spender] = amount;
        emit Approval(owner_, spender, amount);
    }
}