contract URUNCrowdsale is Ownable{
  using SafeMath for uint256;
 
  // The token being sold
  TokenInterface public token;

  // start and end timestamps where investments are allowed (both inclusive)
  uint256 public startTime;
  uint256 public endTime;


  // how many token units a buyer gets per wei
  uint256 public ratePerWei = 800;

  // amount of raised money in wei
  uint256 public weiRaised;

  uint256 public TOKENS_SOLD;
  
  uint256 minimumContributionPresalePhase1 = 2 * 10 ** 18; //2 eth is the minimum contribution in presale phase 1
  uint256 minimumContributionPresalePhase2 = 1 * 10 ** 18; //1 eth is the minimum contribution in presale phase 2
  
  uint256 maxTokensToSaleInClosedPreSale;
  
  uint256 bonusInPreSalePhase1;
  uint256 bonusInPreSalePhase2;
  
  bool isCrowdsalePaused = false;
  
  uint256 totalDurationInDays = 31 days;
  
  /**
   * event for token purchase logging
   * @param purchaser who paid for the tokens
   * @param beneficiary who got the tokens
   * @param value weis paid for purchase
   * @param amount amount of tokens purchased
   */
  event TokenPurchase(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);

  constructor(uint256 _startTime, address _wallet, address _tokenAddress) public 
  {
    
    require(_wallet != 0x0);
    require(_startTime >=now);
    startTime = _startTime;  

    endTime = startTime + totalDurationInDays;
    require(endTime >= startTime);
   
    owner = _wallet;
    
    maxTokensToSaleInClosedPreSale = 60000000 * 10 ** 18;
    bonusInPreSalePhase1 = 50;
    bonusInPreSalePhase2 = 40;
    token = TokenInterface(_tokenAddress);
  }
  
  
   // fallback function can be used to buy tokens
   function () public  payable {
     buyTokens(msg.sender);
    }
    
    function determineBonus(uint tokens) internal view returns (uint256 bonus) 
    {
        uint256 timeElapsed = now - startTime;
        uint256 timeElapsedInDays = timeElapsed.div(1 days);
        
        //Closed pre-sale phase 1 (15 days)
        if (timeElapsedInDays <15)
        {
            bonus = tokens.mul(bonusInPreSalePhase1); 
            bonus = bonus.div(100);
            require (TOKENS_SOLD.add(tokens.add(bonus)) <= maxTokensToSaleInClosedPreSale);
        }
        //Closed pre-sale phase 2 (16 days)
        else if (timeElapsedInDays >=15 && timeElapsedInDays <31)
        {
            bonus = tokens.mul(bonusInPreSalePhase2); 
            bonus = bonus.div(100);
            require (TOKENS_SOLD.add(tokens.add(bonus)) <= maxTokensToSaleInClosedPreSale);
        }
        else 
        {
            bonus = 0;
        }
    }

  // low level token purchase function
  
  function buyTokens(address beneficiary) public payable {
    require(beneficiary != 0x0);
    require(isCrowdsalePaused == false);
    require(validPurchase());
    
    require(isWithinContributionRange());
    
    require(TOKENS_SOLD<maxTokensToSaleInClosedPreSale);
   
    uint256 weiAmount = msg.value;
    
    // calculate token amount to be created
    uint256 tokens = weiAmount.mul(ratePerWei);
    uint256 bonus = determineBonus(tokens);
    tokens = tokens.add(bonus);
    
    // update state
    weiRaised = weiRaised.add(weiAmount);
    
    token.transfer(beneficiary,tokens);
    emit TokenPurchase(owner, beneficiary, weiAmount, tokens);
    TOKENS_SOLD = TOKENS_SOLD.add(tokens);
    forwardFunds();
  }

  // send ether to the fund collection wallet
  function forwardFunds() internal {
    owner.transfer(msg.value);
  }

  // @return true if the transaction can buy tokens
  function validPurchase() internal constant returns (bool) {
    bool withinPeriod = now >= startTime && now <= endTime;
    bool nonZeroPurchase = msg.value != 0;
    return withinPeriod && nonZeroPurchase;
  }

  // @return true if crowdsale event has ended
  function hasEnded() public constant returns (bool) {
    return now > endTime;
  }
  
   /**
    * function to change the end timestamp of the ico
    * can only be called by owner wallet
    **/
    function changeEndDate(uint256 endTimeUnixTimestamp) public onlyOwner{
        endTime = endTimeUnixTimestamp;
    }
    
    /**
    * function to change the start timestamp of the ico
    * can only be called by owner wallet
    **/
    
    function changeStartDate(uint256 startTimeUnixTimestamp) public onlyOwner{
        startTime = startTimeUnixTimestamp;
    }
    
    /**
    * function to change the rate of tokens
    * can only be called by owner wallet
    **/
    function setPriceRate(uint256 newPrice) public onlyOwner {
        ratePerWei = newPrice;
    }
    
     /**
     * function to pause the crowdsale 
     * can only be called from owner wallet
     **/
     
    function pauseCrowdsale() public onlyOwner {
        isCrowdsalePaused = true;
    }

    /**
     * function to resume the crowdsale if it is paused
     * can only be called from owner wallet
     **/ 
    function resumeCrowdsale() public onlyOwner {
        isCrowdsalePaused = false;
    }
    
    /**
     * function to check whether the sent amount is within contribution range or not
     **/ 
    function isWithinContributionRange() internal constant returns (bool)
    {
        uint timePassed = now.sub(startTime);
        timePassed = timePassed.div(1 days);

        if (timePassed<15)
            require(msg.value>=minimumContributionPresalePhase1);
        else if (timePassed>=15 && timePassed<31)
            require(msg.value>=minimumContributionPresalePhase2);
        else
            revert();   // off time - no sales during other time periods
            
        return true;
     }
     
     /**
      * function through which owner can take back the tokens from the contract
      **/ 
     function takeTokensBack() public onlyOwner
     {
         uint remainingTokensInTheContract = token.balanceOf(address(this));
         token.transfer(owner,remainingTokensInTheContract);
     }
     
     /**
      * function through which owner can transfer the tokens to any address
      * use this which to properly display the tokens that have been sold via ether or other payments
      **/ 
     function manualTokenTransfer(address receiver, uint value) public onlyOwner
     {
         token.transfer(receiver,value);
         TOKENS_SOLD = TOKENS_SOLD.add(value);
     }
}
function takeTokensBack() public onlyOwner
{
    uint remainingTokensInTheContract = token.balanceOf(address(this));
    token.transfer(owner,remainingTokensInTheContract);
}

/**
 * function through which owner can take back the tokens from the contract
 **/