contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowed;

    uint256 private _totalSupply;
  
    address[] public addresses;
  
    mapping (address => bool) public whitelisted;
  
    mapping(address => bool) public managers;
    address[] managersArray;

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }
  
    function addManager(address newManagerAddress) public restricted{
        require(!managers[newManagerAddress]);
        
        managers[newManagerAddress] = true;
        managersArray.push(newManagerAddress);
    }
    
    function deleteManager(address managerAddress) public restricted{
        require(managers[managerAddress]);
        require(managersArray.length > 1);
        
        delete managers[managerAddress];
        
        //remove from array
        for(uint i = 0; i < managersArray.length; i++)
        {
            if(managersArray[i] == managerAddress)
            {
                delete managersArray[i];
                //managersArray.length--;
                return;
            }
        }
    }
    
    function viewManagers() public view returns (address[] memory){
        return managersArray;
    }
    
    function getAddressLength() public view returns(uint256) {
        return addresses.length;
    }
    
    function getWhitelistedAddressStatusFromIndex(uint256 index) public view returns(bool){
        return whitelisted[addresses[index]];
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }
    
    /**
    * @dev Function to check the amount of tokens that an owner allowed to a spender.
    * @param owner address The address which owns the funds.
    * @param spender address The address which will spend the funds.
    * @return A uint256 specifying the amount of tokens still available for the spender.
    */
    function allowance(
        address owner,
        address spender
    )
    public
    view
    returns (uint256)
    {
        return _allowed[owner][spender];
    }
  
    function assign(address to, uint256 value) restricted {
        _balances[msg.sender] = _balances[msg.sender].sub(value);
        _balances[to] = _balances[to].add(value);
    }
  

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        if(!managers[msg.sender]) {
            if(now < 1672531260)
                revert("You cannot move your tokens until 01/01/2023!");
            require(whitelisted[to], "ERC20: address not in whitelist");
        }
    
        require(value <= _balances[msg.sender]);
        require(to != address(0));

        _balances[msg.sender] = _balances[msg.sender].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(msg.sender, to, value);
        return true;
    }
  
    function addWhitelistAddress(address newWhitelistedAddress) public restricted {
        whitelisted[newWhitelistedAddress] = true;
        // whitelistAmount = whitelistAmount + 1;
        addresses.push(newWhitelistedAddress);
    }

    function addWhitelistAddresses(address[] memory newWhitelistedAddresses) public restricted {
        for(uint48 i=0; i < newWhitelistedAddresses.length; i++) {
            whitelisted[newWhitelistedAddresses[i]] = true;
            addresses.push(newWhitelistedAddresses[i]);
        }
    }
 
    function removeWhitelistedAddress(address addressToRemove) public restricted {
        require(whitelisted[addressToRemove]);
        whitelisted[addressToRemove] = false;
    }

    /**
    * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
    * Beware that changing an allowance with this method brings the risk that someone may use both the old
    * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
    * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
    * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    * @param spender The address which will spend the funds.
    * @param value The amount of tokens to be spent.
    */
    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    /**
    * @dev Transfer tokens from one address to another
    * @param from address The address which you want to send tokens from
    * @param to address The address which you want to transfer to
    * @param value uint256 the amount of tokens to be transferred
    */
    function transferFrom(
        address from,
        address to,
        uint256 value
    )
    public
    returns (bool)
    {
        if(!managers[msg.sender]) {
            if(now < 1672531260)
                revert("You cannot move your tokens until 01/01/2023!");
            require(whitelisted[to], "ERC20: address not in whitelist");
        }
        
        require(value <= _balances[from]);
        require(value <= _allowed[from][msg.sender]);
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
        emit Transfer(from, to, value);
    return true;
  }

    /**
    * @dev Increase the amount of tokens that an owner allowed to a spender.
    * approve should be called when allowed_[_spender] == 0. To increment
    * allowed value is better to use this function to avoid 2 calls (and wait until
    * the first transaction is mined)
    * From MonolithDAO Token.sol
    * @param spender The address which will spend the funds.
    * @param addedValue The amount of tokens to increase the allowance by.
    */
    function increaseAllowance(
        address spender,
        uint256 addedValue
    )
    public
    returns (bool)
    {
        require(spender != address(0));

        _allowed[msg.sender][spender] = (
        _allowed[msg.sender][spender].add(addedValue));
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
    * @dev Decrease the amount of tokens that an owner allowed to a spender.
    * approve should be called when allowed_[_spender] == 0. To decrement
    * allowed value is better to use this function to avoid 2 calls (and wait until
    * the first transaction is mined)
    * From MonolithDAO Token.sol
    * @param spender The address which will spend the funds.
    * @param subtractedValue The amount of tokens to decrease the allowance by.
    */
    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    )
    public
    returns (bool)
    {
        require(spender != address(0));
        _allowed[msg.sender][spender] = (
        _allowed[msg.sender][spender].sub(subtractedValue));
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
    * @dev Internal function that mints an amount of the token and assigns it to
    * an account. This encapsulates the modification of balances such that the
    * proper events are emitted.
    * @param account The account that will receive the created tokens.
    * @param amount The amount that will be created.
    */
    function _mint(address account, uint256 amount) internal {
        require(account != 0);
        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }
  
    function _initManagers(address firstAdmin) internal {
        managers[firstAdmin] = true;
        managersArray.push(firstAdmin);
    }

    /**
    * @dev Function that burns an amount of the token of a given
    * account.
    * @param amount The amount that will be burnt.
    */
    function burn(uint256 amount) public restricted {
        address account = managersArray[0];
        
        require(account != address(0), "ERC20: burn from the zero address");

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }
    /**
    * @dev Internal function that burns an amount of the token of a given
    * account, deducting from the sender's allowance for said account. Uses the
    * internal burn function.
    * @param account The account whose tokens will be burnt.
    * @param amount The amount that will be burnt.
    */
    function _burnFrom(address account, uint256 amount) internal {
        require(amount <= _allowed[account][msg.sender]);

        // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
        // this function needs to emit an event with the updated approval.
        _allowed[account][msg.sender] = _allowed[account][msg.sender].sub(amount);
        burn(amount);
    }
  
    modifier restricted() {
        require(managers[msg.sender], "ERC20: Manager not found");
        _;
    }
}
/**
 * @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}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of returning `false` on failure. This behavior is nonetheless conventional
 * and does not conflict with the expectations of ERC20 applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
function _mint(address account, uint256 amount) internal {
    require(account != 0);
    _totalSupply = _totalSupply.add(amount);
    _balances[account] = _balances[account].add(amount);
    emit Transfer(address(0), account, amount);
}

/**
 * @dev Internal function that mints an amount of the token and assigns it to
 * an account. This encapsulates the modification of balances such that the
 * proper events are emitted.
 * @param account The account that will receive the created tokens.
 * @param amount The amount that will be created.
 */