pragma solidity 0.5.11;

/**
 * @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;
    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 Crowdsale
 * @dev Crowdsale is a base contract for managing a token crowdsale.
 * Crowdsales have a start and end timestamps, where investors can make
 * token purchases and the crowdsale will assign them tokens based
 * on a token per ETH rate. Funds collected are forwarded 
 to a wallet
 * as they arrive.
 */
interface token { function transfer(address receiver, uint amount) external ; }
contract Crowdsale {
  using SafeMath for uint256;


  // address where funds are collected
  address payable public wallet;
  // token address
  address public addressOfTokenUsedAsReward;

  uint256 public price = 2000;

  token tokenReward;

  // amount of raised money in wei
  uint256 public weiRaised;

  /**
   * 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 () public {
    //You will change this to your wallet where you need the ETH 
    wallet = 0xec7f796Db78203A2692b382AFA8356A05B6DAB8F;
    
    //Here will come the checksum address we got
    addressOfTokenUsedAsReward =  0x64Ac6Dfd5D74C5A255c970F173Feb37aF6d6D04B;

    tokenReward = token(addressOfTokenUsedAsReward);
  }

  bool public started = true;

  function startSale() public {
    require (msg.sender == wallet);
    started = true;
  }

  function stopSale() public {
    require(msg.sender == wallet);
    started = false;
  }

  function setPrice(uint256 _price) public {
    require(msg.sender == wallet);
    price = _price;
  }
  function changeWallet(address payable _wallet) public {
    require (msg.sender == wallet);
    wallet = _wallet;
  }


  // fallback function can be used to buy tokens
  function () external payable  {
    buyTokens(msg.sender);
  }

  // low level token purchase function
  function buyTokens(address payable beneficiary) payable public {
    require(beneficiary != address(0));
    require(validPurchase());

    uint256 weiAmount = msg.value;


    // calculate token amount to be sent
    uint256 tokens = (weiAmount) * price;//weiamount * price 
    // uint256 tokens = (weiAmount/10**(18-decimals)) * price;//weiamount * price 

    // update state
    weiRaised = weiRaised.add(weiAmount);

    tokenReward.transfer(beneficiary, tokens);
    emit TokenPurchase(msg.sender, beneficiary, weiAmount, tokens);
    forwardFunds();
  }

  // send ether to the fund collection wallet
  // override to create custom fund forwarding mechanisms
  function forwardFunds() internal {
     wallet.transfer(msg.value);
  }

  // @return true if the transaction can buy tokens
  function validPurchase() internal view returns (bool) {
    bool withinPeriod = started;
    bool nonZeroPurchase = msg.value != 0;
    return withinPeriod && nonZeroPurchase;
  }

  function withdrawTokens(uint256 _amount) public {
    require (msg.sender == wallet);
    tokenReward.transfer(wallet,_amount);
  }
}