pragma solidity ^0.4.22;

/**
 * @title SafeMath
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a * b;
    assert(a == 0 || 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 c;
  }

  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) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
  }
}

/**
 * @title ERC20Basic
 * @dev Simpler version of ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/179
 */
contract ERC20Basic {
  uint256 public totalSupply;
  function balanceOf(address who) constant returns (uint256);
  function transfer(address to, uint256 value) 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) constant returns (uint256);
  function transferFrom(address from, address to, uint256 value) returns (bool);
  function approve(address spender, uint256 value) returns (bool);
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title Basic token
 * @dev Basic version of StandardToken, with no allowances. 
 */
contract BasicToken is ERC20Basic {
  using SafeMath for uint256;

  mapping(address => uint256) balances;

  /**
  * @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) returns (bool) {
    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) constant returns (uint256 balance) {
    return balances[_owner];
  }

}

/**
 * @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 {

  mapping (address => mapping (address => uint256)) 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 amout of tokens to be transfered
   */
  function transferFrom(address _from, address _to, uint256 _value) returns (bool) {
    var _allowance = allowed[_from][msg.sender];

    // Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
    // require (_value <= _allowance);

    balances[_to] = balances[_to].add(_value);
    balances[_from] = balances[_from].sub(_value);
    allowed[_from][msg.sender] = _allowance.sub(_value);
    emit Transfer(_from, _to, _value);
    return true;
  }

  /**
   * @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
   * @param _spender The address which will spend the funds.
   * @param _value The amount of tokens to be spent.
   */
  function approve(address _spender, uint256 _value) returns (bool) {

    // To change the approve amount you first have to reduce the addresses`
    //  allowance to zero by calling `approve(_spender, 0)` if it is not
    //  already 0 to mitigate the race condition described here:
    //  https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
    require((_value == 0) || (allowed[msg.sender][_spender] == 0));

    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 address The address which owns the funds.
   * @param _spender address The address which will spend the funds.
   * @return A uint256 specifing the amount of tokens still avaible for the spender.
   */
  function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
    return allowed[_owner][_spender];
  }

}


/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
  address public owner;


  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() {
    owner = msg.sender;
  }


  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }


  /**
   * @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) onlyOwner {
    if (newOwner != address(0)) {
      owner = newOwner;
    }
  }

}

contract DBXTTest4 is Ownable,StandardToken {
    using SafeMath for uint256;

    string public name = "DBXTTest4";
    string public symbol = "DBXTTest4";
    uint256 public decimals = 18;
    uint256 public INITIAL_SUPPLY = 100000 * 1 ether;

    
    address public beneficiary;

    uint256 public priceETH;
    uint256 public priceDT;

    uint256 public weiRaised = 0;
    uint256 public investorCount = 0;

    uint public startTime;
    uint public endTime;

    bool public crowdsaleFinished = false;

    event Burn(address indexed from, uint256 value);
    event GoalReached(uint amountRaised);
    event NewContribution(address indexed holder, uint256 tokenAmount, uint256 etherAmount);

    modifier onlyAfter(uint time) {
        require(now > time);
        _;
    }

    modifier onlyBefore(uint time) {
        require(now < time);
        _;
    }

    constructor (
        address _beneficiary,
        uint256 _priceETH,
        uint256 _priceDT,
        uint _startTime,
        uint _duration) public {
        totalSupply = INITIAL_SUPPLY;
        balances[msg.sender] = INITIAL_SUPPLY;
        beneficiary = _beneficiary;
        priceETH = _priceETH;
        priceDT = _priceDT;

        startTime = _startTime;
        endTime = _startTime + _duration * 1 weeks;
    }

    function () payable {
        require(msg.value >= 0.01 * 1 ether);
        doPurchase(msg.sender, msg.value);
    }

    function withdraw(uint256 _value) onlyOwner {
        beneficiary.transfer(_value);
    }

    function finishCrowdsale() onlyOwner {
        transfer(beneficiary, balanceOf(this));
        crowdsaleFinished = true;
    }

    function doPurchase(address _sender, uint256 _value) private onlyAfter(startTime) onlyBefore(endTime) {
        
        require(!crowdsaleFinished);

        uint256 dtCount = _value.mul(priceDT).div(priceETH);

        require(balanceOf(this) >= dtCount);

        if (balanceOf(_sender) == 0) investorCount++;

        transfer(_sender, dtCount);

        weiRaised = weiRaised.add(_value);

        emit NewContribution(_sender, dtCount, _value);

        if (balanceOf(this) == 0) {
            emit GoalReached(weiRaised);
        }
    }

    function burn(uint256 _value) returns (bool success) {
        require(balances[msg.sender] >= _value);
        balances[msg.sender] = balances[msg.sender].sub(_value);
        totalSupply = totalSupply.sub(_value);
        emit Burn(msg.sender, _value);
        return true;
  }
}