contract KvarkToken {

    string public name = "KVANTOR KVARK token";
    string public symbol = "KVK";
    uint public decimals = 18;

    constructor() public {
        minters.add(msg.sender);
        emit MinterAdded(msg.sender);
        
        owner = msg.sender;
        emit OwnershipTransferred(address(0), owner);
    }

    address private owner;

    event OwnershipTransferred(
      address indexed previousOwner,
      address indexed newOwner
    );

    /**
    * @return the address of the owner.
    */
    function getOwner() public view returns(address) {
        return owner;  
    }

    /**
    * @dev Throws if called by any account other than the owner.
    */
    modifier onlyOwner() {
        require(isOwner());
        _;
    }

    /**
    * @return true if `msg.sender` is the owner of the contract.
    */
    function isOwner() public view returns(bool) {
        return msg.sender == owner;
    }

    /**
    * @dev Allows the current owner to relinquish control of the contract.
    * @notice Renouncing to ownership will leave the contract without an owner.
    * It will not be possible to call the functions with the `onlyOwner`
    * modifier anymore.
    */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(owner, address(0));
        owner = address(0);
    }

    /**
    * @dev Allows the current owner to transfer control of the contract to a newOwner.
    * @param newOwner The address to transfer ownership to.
    */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
    * @dev Transfers control of the contract to a newOwner.
    * @param newOwner The address to transfer ownership to.
    */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

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

    uint256 private _totalSupply;


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

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

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query 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];
    }

    /**
    * @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) {
        _transfer(msg.sender, to, value);
        return true;
    }

    /**
    * @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)
    {
        require(value <= _allowed[from][msg.sender]);

        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
        _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 Transfer token for a specified addresses
    * @param from The address to transfer from.
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function _transfer(address from, address to, uint256 value) internal {
        require(value <= _balances[from]);
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    /**
    * @dev Function to mint tokens
    * @param to The address that will receive the minted tokens.
    * @param value The amount of tokens to mint.
    * @return A boolean that indicates if the operation was successful.
    */
    function mint(address to, uint256 value) public returns (bool)
    {
        require(isMinter(msg.sender));
        _mint(to, value);
        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 value The amount that will be created.
    */
    function _mint(address account, uint256 value) internal {
        require(account != 0);
        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }

      /**
    * @dev Burns a specific amount of tokens.
    * @param value The amount of token to be burned.
    */
    function burn(uint256 value) public {
        _burn(msg.sender, value);
    }

    /**
    * @dev Burns a specific amount of tokens from the target address and decrements allowance
    * @param from address The address which you want to send tokens from
    * @param value uint256 The amount of token to be burned
    */
    function burnFrom(address from, uint256 value) public {
        _burnFrom(from, value);
    }

    /**
    * @dev Internal function that burns an amount of the token of a given
    * account.
    * @param account The account whose tokens will be burnt.
    * @param value The amount that will be burnt.
    */
    function _burn(address account, uint256 value) internal {
        require(account != 0);
        require(value <= _balances[account]);

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
    * @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 value The amount that will be burnt.
    */
    function _burnFrom(address account, uint256 value) internal {
        require(value <= _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(value);
        _burn(account, value);
    }

    using Roles for Roles.Role;

    event MinterAdded(address indexed account);
    event MinterRemoved(address indexed account);

    Roles.Role private minters;

    function isMinter(address account) public view returns (bool) {
        return minters.has(account);
    }

    function addMinter(address account) public onlyOwner {
        minters.add(account);
        emit MinterAdded(account);
    }

    function renounceMinter(address account) public onlyOwner {
        minters.remove(account);
        emit MinterRemoved(account);
    }
}
/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
 * Originally based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(owner, address(0));
        owner = address(0);
    }
/**
 * @dev Allows the current owner to relinquish control of the contract.
 * @notice Renouncing to ownership will leave the contract without an owner.
 * It will not be possible to call the functions with the `onlyOwner`
 * modifier anymore.
 */