pragma solidity 0.5.8;

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
    function totalSupply() public view returns (uint256);
    function balanceOf(address who) public view returns (uint256);
    function transfer(address to, uint256 value) public returns (bool);
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Burn(address indexed burner, uint256 value);
}

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
    /**
     * @dev Multiplies two numbers, throws on overflow
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    /**
     * @dev Integer division of two numbers, truncating the quotient
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return c;
    }

    /**
     * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend)
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    /**
     * @dev Adds two numbers, throws on overflow
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances
 */
contract BasicToken is ERC20Basic {
    using SafeMath for uint256;
    
    mapping(address => uint256) balances;
    uint256 totalSupply_;
    uint256 burnedTotalNum_;

    /**
     * @dev Total number of tokens in existence
     */
    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    /**
     * @dev Total number of tokens already burned
     */
    function totalBurned() public view returns (uint256) {
        return burnedTotalNum_;
    }

    /**
     * @dev Burn tokens for sender
     * @param _value The amount to be burned
     */
    function burn(uint256 _value) public returns (bool) {
        require(_value <= balances[msg.sender]);

        address burner = msg.sender;
        balances[burner] = balances[burner].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        burnedTotalNum_ = burnedTotalNum_.add(_value);

        emit Burn(burner, _value);

        return true;
    }

    /**
     * @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 _to is address(0), invoke burn function
        if (_to == address(0)) {
            return burn(_value);
        }

        require(_value <= balances[msg.sender]);
        // SafeMath.sub will throw if there is not enough balance
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);

        emit Transfer(msg.sender, _to, _value);

        return true;
    }

    /**
     * @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];
    }
}

/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
contract ERC20 is ERC20Basic {
    function allowance(address owner, address spender) public view returns (uint256);
    function transferFrom(address from, address to, uint256 value) public returns (bool);
    function approve(address spender, uint256 value) public returns (bool);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token
 * @dev https://github.com/ethereum/EIPs/issues/20
 * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 */
contract StandardToken is ERC20, BasicToken {
    using SafeMath for uint256;

    uint private constant MAX_UINT = 2**256 - 1;

    mapping (address => mapping (address => uint256)) internal allowed;

    /**
     * @dev Burn tokens for a specified address
     * @param _owner The address which you want to burn
     * @param _value the amount of tokens to be burned
     */
    function burnFrom(address _owner, uint256 _value) public returns (bool) {
        require(_owner != address(0));
        require(_value <= balances[_owner]);
        require(_value <= allowed[_owner][msg.sender]);

        balances[_owner] = balances[_owner].sub(_value);
        if (allowed[_owner][msg.sender] < MAX_UINT) {
            allowed[_owner][msg.sender] = allowed[_owner][msg.sender].sub(_value);
        }
        totalSupply_ = totalSupply_.sub(_value);
        burnedTotalNum_ = burnedTotalNum_.add(_value);

        emit Burn(_owner, _value);

        return true;
    }

    /**
     * @dev Transfer tokens from one address to another
     * @param _from The address which you want to send tokens from
     * @param _to The address which you want to transfer to
     * @param _value The amount of tokens to be transferred
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        if (_to == address(0)) {
            return burnFrom(_from, _value);
        }

        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);

        /// an allowance of MAX_UINT represents an unlimited allowance
        /// @dev see https://github.com/ethereum/EIPs/issues/717
        if (allowed[_from][msg.sender] < MAX_UINT) {
            allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        }

        emit Transfer(_from, _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) {
        allowed[msg.sender][_spender] = _value;

        emit Approval(msg.sender, _spender, _value);

        return true;
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender
     * @param _owner The address which owns the funds
     * @param _spender 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 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 increaseApproval(address _spender, uint _addedValue) public returns (bool) {
        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 decreaseApproval(address _spender, uint _subtractedValue) public returns (bool) {
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }

        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);

        return true;
    }
}

contract HBBToken is StandardToken {
    using SafeMath for uint256;

    string     public name = "HBB";
    string     public symbol = "HBB";
    uint8      public decimals = 18;

    constructor() public {
        totalSupply_ = 33333333333000000000000000000;

        balances[msg.sender] = totalSupply_;
    }

    function () payable external {
        revert();
    }

    function batchTransfer(address[] calldata accounts, uint256[] calldata amounts) external returns (bool) {
        require(accounts.length == amounts.length);
        for (uint i = 0; i < accounts.length; i++) {
            require(transfer(accounts[i], amounts[i]), "transfer failed");
        }

        return true;
    }
}