// 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 recipient, 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 sender, address recipient, uint256 amount) external returns (bool);
    function safeTransfer(address recipient, uint256 amount) external returns (bool);
    function increaseAllowance(address spender, uint256 addedValue) external returns (bool);
    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract TeTaTokens is IERC20 {
    string public constant _name = "TeTa Capital";
    string public constant _symbol = "TeTa";
    uint8 public constant decimals = 6;
    uint256 private constant _totalSupply = 369000000 * 10 ** decimals;

    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    constructor() {
        _balances[msg.sender] = _totalSupply;
        _owner = msg.sender;
        emit Transfer(address(0), msg.sender, _totalSupply);
        emit OwnershipTransferred(address(0), _owner);
    }

    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }

    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }

    function transfer(address recipient, uint256 amount) external override returns (bool) {
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function approve(address spender, uint256 amount) external override returns (bool) {
        _approve(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) external override returns (bool) {
        require(recipient != address(0), "Transfer to the zero address");
        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][msg.sender];
        require(currentAllowance >= amount, "Transfer amount exceeds allowance");
        _approve(sender, msg.sender, currentAllowance - amount);
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) external override returns (bool) {
        _approve(msg.sender, spender, _allowances[msg.sender][spender] + addedValue);
        return true;
    }

    function decreaseAllowance(address spender, uint256 subtractedValue) external override returns (bool) {
        uint256 currentAllowance = _allowances[msg.sender][spender];
        require(currentAllowance >= subtractedValue, "Decreased allowance below zero");
        _approve(msg.sender, spender, currentAllowance - subtractedValue);
        return true;
    }

    function safeTransfer(address recipient, uint256 amount) external override returns (bool) {
        require(recipient != msg.sender, "Transfer to the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");
        require(_balances[msg.sender] >= amount, "Insufficient balance");
        _transfer(msg.sender, recipient, amount);
        return true;
    }

    function _transfer(address sender, address recipient, uint256 amount) private {
        require(sender != address(0), "Transfer from the zero address");
        require(recipient != address(0), "Transfer to the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");
        require(_balances[sender] >= amount, "Insufficient balance");
        _balances[sender] -= amount;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }

    function _approve(address owner, address spender, uint256 amount) private {
        require(owner != address(0), "Approve from the zero address");
        require(spender != address(0), "Approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function totalSupply() external override pure returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) external override view returns (uint256) {
        return _balances[account];
    }

    function allowance(address owner, address spender) external override view returns (uint256) {
        return _allowances[owner][spender];
    }
}