pragma solidity ^0.4.24;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
  function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
    if (_a == 0) {
      return 0;
    }
    c = _a * _b;
    assert(c / _a == _b);
    return c;
  }

  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 _a / _b;
  }

  function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
    assert(_b <= _a);
    return _a - _b;
  }

  function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
    c = _a + _b;
    assert(c >= _a);
    return c;
  }
}

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);
}

/**
 * @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);
}

contract BasicToken is ERC20Basic {
  using SafeMath for uint256;
  mapping(address => uint256) internal balances;
  uint256 internal totalSupply_;

  /**
  * @dev Total number of tokens in existence
  */
  function totalSupply() public view returns (uint256) {
    return totalSupply_;
  }

  /**
  * @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) {
    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;
  }

  /**
  * @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];
  }

}

contract StandardToken is ERC20, BasicToken {

  mapping (address => mapping (address => uint256)) internal allowed;


  /**
   * @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 <= 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;
  }


  function approve(address _spender, uint256 _value) public returns (bool) {
    allowed[msg.sender][_spender] = _value;
    emit Approval(msg.sender, _spender, _value);
    return true;
  }

 
  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,
    uint256 _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,
    uint256 _subtractedValue
  )
    public
    returns (bool)
  {
    uint256 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;
  }

}

// ERC20 standard token
contract NBE is StandardToken {
    address public admin;
    string public name = "NBE";
    string public symbol = "NBE"; 
    uint8 public decimals = 18; 
    uint256 public INITIAL_SUPPLY = 10000000000000000000000000000;
    
    mapping (address => uint256) public frozenTimestamp; 

    bool public exchangeFlag = true; 
   
    uint256 public minWei = 1;  // 1 wei  1eth = 1*10^18 wei
    uint256 public maxWei = 20000000000000000000000; // 20000 eth
    uint256 public maxRaiseAmount = 500000000000000000000000; //  500000 eth
    uint256 public raisedAmount = 0; //  0 eth
    uint256 public raiseRatio = 10000; //  1eth = 10000

    constructor() public {
        totalSupply_ = INITIAL_SUPPLY;
        admin = msg.sender;
        balances[msg.sender] = INITIAL_SUPPLY;
    }

    function()
    public payable {
        require(msg.value > 0);
        if (exchangeFlag) {
            if (msg.value >= minWei && msg.value <= maxWei){
                if (raisedAmount < maxRaiseAmount) {
                    uint256 valueNeed = msg.value;
                    raisedAmount = raisedAmount.add(msg.value);
                    if (raisedAmount > maxRaiseAmount) {
                        uint256 valueLeft = raisedAmount.sub(maxRaiseAmount);
                        valueNeed = msg.value.sub(valueLeft);
                        msg.sender.transfer(valueLeft);
                        raisedAmount = maxRaiseAmount;
                    }
                    if (raisedAmount >= maxRaiseAmount) {
                        exchangeFlag = false;
                    }
                   
                    uint256 _value = valueNeed.mul(raiseRatio);

                    require(_value <= balances[admin]);
                    balances[admin] = balances[admin].sub(_value);
                    balances[msg.sender] = balances[msg.sender].add(_value);

                    emit Transfer(admin, msg.sender, _value);

                }
            } else {
                msg.sender.transfer(msg.value);
            }
        } else {
            msg.sender.transfer(msg.value);
        }
    }

    /**
    * admin
    */
    function changeAdmin(
        address _newAdmin
    )
    public
    returns (bool)  {
        require(msg.sender == admin);
        require(_newAdmin != address(0));
        balances[_newAdmin] = balances[_newAdmin].add(balances[admin]);
        balances[admin] = 0;
        admin = _newAdmin;
        return true;
    }

    // withdraw admin
    function withdraw (
        uint256 _amount
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        msg.sender.transfer(_amount);
        return true;
    }

    /**
    * 
    */
    function freezeWithTimestamp(
        address _target,
        uint256 _timestamp
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        require(_target != address(0));
        frozenTimestamp[_target] = _timestamp;
        return true;
    }

    
    /**
    * 
    */
    function transfer(
        address _to,
        uint256 _value
    )
    public
    returns (bool) {
        // require(!frozenAccount[msg.sender]);
        require(now > frozenTimestamp[msg.sender]);
        require(_to != address(0));
        require(_value <= balances[msg.sender]);

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);

        emit Transfer(msg.sender, _to, _value);
        return true;
    }
    
    //********************************************************************************
    //
    function getFrozenTimestamp(
        address _target
    )
    public view
    returns (uint256) {
        require(_target != address(0));
        return frozenTimestamp[_target];
    }
  
    //
    function getBalance()
    public view
    returns (uint256) {
        return address(this).balance;
    }
    

    // change flag
    function setExchangeFlag (
        bool _flag
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        exchangeFlag = _flag;
        return true;

    }

    // change ratio
    function setRaiseRatio (
        uint256 _value
    )
    public
    returns (bool) {
        require(msg.sender == admin);
        raiseRatio = _value;
        return true;
    }


}