Secury Wallet (SECURY)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.30;

contract SecuryWalletToken {
    string public constant name = "Secury Wallet";
    string public constant symbol = "SECURY";
    uint8 public constant decimals = 18;
    uint256 private _totalSupply;

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

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

    constructor() {
        owner = msg.sender;
        _mint(msg.sender, 1_000_000_000 * 10**decimals);
    }

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

    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0), "Zero address");
        owner = newOwner;
    }

    // --- ERC20 Core ---
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

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

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

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

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

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

    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
    }

    // --- Internals ---
    function _transfer(address from, address to, uint256 amount) internal {
        require(from != address(0), "Transfer from zero");
        require(to != address(0), "Transfer to zero");
        require(_balances[from] >= amount, "Insufficient balance");
        _balances[from] -= 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 _burn(address account, uint256 amount) internal {
        require(account != address(0), "Burn from zero");
        require(_balances[account] >= amount, "Insufficient balance");
        _balances[account] -= amount;
        _totalSupply -= amount;
        emit Transfer(account, address(0), amount);
    }

    // Fixed: Renamed parameter from `owner` to `_owner`
    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);
    }

    // Fixed: Updated to use `_owner`
    function _spendAllowance(address _owner, address spender, uint256 amount) internal {
        uint256 currentAllowance = allowance(_owner, spender);
        require(currentAllowance >= amount, "Insufficient allowance");
        _approve(_owner, spender, currentAllowance - amount);
    }
}