pragma solidity ^0.4.24;

/**
 * @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 c) {
    if (a == 0) {
      return 0;
    }
    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 a / b;
  }

  /**
  * @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 c) {
    c = a + b;
    assert(c >= a);
    return c;
  }
}

/**
 * @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;

  event OwnershipRenounced(address indexed previousOwner);
  event OwnershipTransferred(
    address indexed previousOwner,
    address indexed newOwner
  );

  /**
   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
   * account.
   */
  function Ownable() public {
    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) public onlyOwner {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }

  /**
   * @dev Allows the current owner to relinquish control of the contract.
   */
  function renounceOwnership() public onlyOwner {
    emit OwnershipRenounced(owner);
    owner = address(0);
  }
}


interface BittechToken {
    function balanceOf(address who) external view returns (uint256);
    function transfer(address receiver, uint amount) external;
    function burn(uint256 _value) external;
}


contract BittechSale is Ownable {
    using SafeMath for uint256;
    
    BittechToken public token;
    uint256 public minimalPriceUSD = 10000; // 10 usd
    uint256 public ETHUSD = 300;
    uint256 public tokenPricePerUSD = 100; // 1 usd
    
    address public constant fundsWallet = 0x1ba99f4F5Aa56684423a122D72990A7851AaFD9e;
    uint256 public startTime;
    uint256 public constant weekTime = 604800;
    
    constructor() public {
       token = BittechToken(0x6EE2EE1a5a257E6E7AdE7fe537617EaD9C7BD3D2);
       startTime = now;
    }
    
    function getBonus() public view returns (uint256) {
        
        if (now >= startTime.add(weekTime.mul(8))) {
            return 104;
        } else if (now >= startTime.add(weekTime.mul(7))) {
            return 106;
        } else if (now >= startTime.add(weekTime.mul(6))) {
            return 108;
        } else if (now >= startTime.add(weekTime.mul(5))) {
            return 110;
        } else if (now >= startTime.add(weekTime.mul(4))) {
            return 112;
        } else if (now >= startTime.add(weekTime.mul(3))) {
            return 114;
        } else if (now >= startTime.add(weekTime.mul(2))) {
            return 116;
        } else if (now >= startTime.add(weekTime)) {
            return 118;
        } else {
            return 120;
        }
        
    }
    
    function () external payable {
        require(msg.sender != address(0));
        require(msg.value.mul(ETHUSD) >= minimalPriceUSD.mul(10 ** 18).div(1000));
        
        uint256 tokens = msg.value.mul(ETHUSD).mul(getBonus()).mul(tokenPricePerUSD).div(100).div(100);
        token.transfer(msg.sender, tokens);
        
        if (now >= startTime.add(weekTime.mul(8))) {
            fundsWallet.transfer(address(this).balance);
            token.burn(token.balanceOf(address(this)));
        }
    }
    
    function sendTokens(address _to, uint256 _amount) external onlyOwner {
        token.transfer(_to, _amount);
    }
    
    function updatePrice(uint256 _ETHUSD) onlyOwner public {
        ETHUSD = _ETHUSD;
    }

    function updateMinimal(uint256 _minimalPriceUSD) onlyOwner public {
        minimalPriceUSD = _minimalPriceUSD;
    }

    function updateTokenPricePerUSD(uint256 _tokenPricePerUSD) onlyOwner public {
        tokenPricePerUSD = _tokenPricePerUSD;
    }
    
}