QRX Lottery - Audit Report

Summary

QRX Lottery Audit Report The QuiverX intends to take investing to the next level. By utilizing blockchain technology, investors now have the opportunity to own fractional shares of high yielding investments.

We have already audited QuiverX's staking platform, XEarn.capital, and found the platform to be secure. View that audit here. We audited their token as well and came to the same conclusion, which you can view here. For this audit, we analyzed QuiverX's lottery contract.

QRX Lottery is a new luck-based lottery smart contract by the QuiverX team. QuiverX is a crowdfunding investment platform using cryptocurrency to have partial ownership of real world assets, stocks and, digital investments.

Features of the Lottery contract:
  • Users can enter into a time-based lottery in denominations of 0.1eth. The winner off the lottery shall receive an NFT prize from the deployer after the lottery concludes.
  • Users can earn a bonus in QRX by referring others.
  • Owners have the ability to update the lottery enterance fee.
  • Ownership - Some functions are protected and can only be called by the contract owner or appointed operators. The owner can transfer ownership to any address.
  • Utilization of SafeMath and SafeERC20 to prevent overflows and ensure safe transfers.
Audit Findings Summary:
  • The kindaRandom() function relies on predictable environment variables. This is common, albiet not best practice, but the probability of miners maliciously changing these variables is extremley low.
  • No security issues from outside attackers were identified.
  • Date of Lottery Contract Audit: November 18th, 2020.
  • Date of Token Contract Audit: November 22nd, 2020.

We ran over 400,000 transactions interacting with this contract on a test blockchain to determine these results.
Date: November 18th, 2020
Vulnerability Category Notes Result
Arbitrary Storage Write N/A PASS
Arbitrary Jump N/A PASS
Delegate Call to Untrusted Contract N/A PASS
Dependence on Predictable Variables Decisions are made based on the block.timestamp environment variable which can
be manipulated by a malicious miner. This is extremley unlikely to occur.
Warning
Deprecated Opcodes N/A PASS
Ether Thief N/A PASS
Exceptions N/A PASS
External Calls N/A PASS
Integer Over/Underflow N/A PASS
Multiple Sends N/A PASS
Suicide N/A PASS
State Change External Calls N/A Pass
Unchecked Retval N/A PASS
User Supplied Assertion N/A PASS
Critical Solidity Compiler N/A PASS
Overall Contract Safety   PASS

Smart Contract Graph

Contract Inheritance


 ($) = payable function
 # = non-constant function
 
 Int = Internal
 Ext = External
 Pub = Public
 
 + [Lib] Math 
    - [Int] max
    - [Int] min
    - [Int] average

 + [Lib] SafeMath 
    - [Int] add
    - [Int] sub
    - [Int] sub
    - [Int] mul
    - [Int] div
    - [Int] div
    - [Int] mod
    - [Int] mod

 +  Context 
    - [Int]  #
    - [Int] _msgSender
    - [Int] _msgData

 +  Ownable (Context)
    - [Int]  #
    - [Pub] owner
    - [Pub] isOwner
    - [Pub] renounceOwnership #
       - modifiers: onlyOwner
    - [Pub] transferOwnership #
       - modifiers: onlyOwner
    - [Int] _transferOwnership #

 + [Int] IERC20 
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] transfer #
    - [Ext] mint #
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transferFrom #

 + [Lib] Address 
    - [Int] isContract
    - [Int] sendValue #
    - [Int] functionCall #
    - [Int] functionCall #
    - [Int] functionCallWithValue #
    - [Int] functionCallWithValue #
    - [Int] functionStaticCall
    - [Int] functionStaticCall
    - [Int] functionDelegateCall #
    - [Int] functionDelegateCall #
    - [Prv] _verifyCallResult

 + [Lib] SafeERC20 
    - [Int] safeTransfer #
    - [Int] safeTransferFrom #
    - [Int] safeApprove #
    - [Int] safeIncreaseAllowance #
    - [Int] safeDecreaseAllowance #
    - [Prv] callOptionalReturn #

 +  QRXLottery (Ownable)
    - [Pub]  #
    - [Pub] getWeeklyDrawAddressLength
    - [Pub] getWeeklyDrawAddress
    - [Pub] setQRXfee #
       - modifiers: onlyOwner
    - [Pub] withdrawEther #
       - modifiers: onlyOwnerOperator
    - [Int] relayEther #
    - [Pub] drainTokens #
       - modifiers: onlyOwnerOperator
    - [Pub] deposit ($)
    - [Pub] kindaRandom
    - [Pub] returnIndex
    - [Pub] drawWinner #
       - modifiers: onlyOwnerOperator
    - [Int] checkDepositValue
    - [Prv] updateAccount #
							

Click here to download the source code as a .sol file.


pragma solidity ^0.6.12;
pragma experimental ABIEncoderV2;
 
//copyright Flisko https://github.com/flisko
//SPDX-License-Identifier: MIT
// File: @openzeppelin/contracts/math/Math.sol
 
pragma solidity ^0.6.12;
 
/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }
 
    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }
 
    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + (((a % 2) + (b % 2)) / 2);
    }
}
 
// File: @openzeppelin/contracts/math/SafeMath.sol
 
 
 
/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
 
        return c;
    }
 
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }
 
    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     *
     * _Available since v2.4.0._
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;
 
        return c;
    }
 
    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) {
            return 0;
        }
 
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
 
        return c;
    }
 
    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }
 
    /**
     * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
 
        return c;
    }
 
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }
 
    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     *
     * _Available since v2.4.0._
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}
 
// File: @openzeppelin/contracts/GSN/Context.sol
 
pragma solidity ^0.6.12;
 
/*
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with GSN meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
contract Context {
    // Empty internal constructor, to prevent people from mistakenly deploying
    // an instance of this contract, which should be used via inheritance.
    constructor() internal {}
 
    // solhint-disable-previous-line no-empty-blocks
 
    function _msgSender() internal view returns (address payable) {
        return msg.sender;
    }
 
    function _msgData() internal view returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
 
// File: @openzeppelin/contracts/ownership/Ownable.sol
 
pragma solidity ^0.6.12;
 
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
contract Ownable is Context {
    address private _owner;
 
    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );
 
    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() internal {
        _owner = _msgSender();
        emit OwnershipTransferred(address(0), _owner);
    }
 
    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }
 
    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner(), "Ownable: caller is not the owner");
        _;
    }
 
    /**
     * @dev Returns true if the caller is the current owner.
     */
    function isOwner() public view returns (bool) {
        return _msgSender() == _owner;
    }
 
    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }
 
    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }
 
    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     */
    function _transferOwnership(address newOwner) internal {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}
 
// File: @openzeppelin/contracts/token/ERC20/IERC20.sol
 
pragma solidity ^0.6.12;
 
/**
 * @dev Interface of the ERC20 standard as defined in the EIP. Does not include
 * the optional functions; to access them see {ERC20Detailed}.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);
 
    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);
 
    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);
 
    function mint(address account, uint256 amount) external;
 
    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);
 
    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);
 
    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);
 
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);
 
    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}
 
// File: @openzeppelin/contracts/utils/Address.sol
 
pragma solidity ^0.6.12;
 
/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.
 
        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }
 
    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");
 
        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }
 
    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain`call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }
 
    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");
 
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");
 
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }
 
    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.3._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");
 
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }
 
    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
 
                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
 
// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol
 
pragma solidity ^0.6.12;
 
/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;
 
    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }
 
    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }
 
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }
 
    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(
            value
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }
 
    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(
            value,
            "SafeERC20: decreased allowance below zero"
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }
 
    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves.
 
        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");
 
        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");
 
        if (returndata.length > 0) {
            // Return data is optional
            // solhint-disable-next-line max-line-length
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}
 
contract QRXLottery is Ownable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;
    uint256[] denominations = [
        0.1 ether,
        0.2 ether,
        0.3 ether,
        0.4 ether,
        0.5 ether,
        0.6 ether,
        0.7 ether,
        0.8 ether,
        0.9 ether,
        1 ether
    ];
 
    address[] public weeklyDrawAddress;
    uint256 public periodStart = 0;
    uint256 public periodDelay = 7 days; //testing
    uint256 public currentPeriod = 1;
    uint256 public qrxFee = 1000 ether;
    address private operator;
    address private immutable collector = 0x4B8d43576aB86Bf008ECFADfeEAF9793B603EC15; // 0x4B8d43576aB86Bf008ECFADfeEAF9793B603EC15    test 0x8d6Cf44B6cA55550b96C4599B00b47A8EC67C596
    IERC20 qrx;
    struct User {
        address userAddress;
        uint256 depositedAmount;
    }
 
    mapping(address => User) public _weeklyDraw1;
    mapping(address => User) public _weeklyDraw2;
    mapping(address => User) public _weeklyDraw3;
    mapping(address => User) public _weeklyDraw4;
    mapping(address => User) public _weeklyDraw5;
 
    event Deposited(
        address indexed user,
        uint256 amount,
        address indexed referral,
        uint256 points
    );
    event Drawn(uint256 period, address indexed winner, address[] addresses);
    event TransferedReferralReward(address indexed user, uint256 amount);
    event calculatedPoints(User user);
 
   constructor(address _qrxAddress, uint256 _start, address _operator) public {
        qrx = IERC20(_qrxAddress);
        //periodStart = block.timestamp; //testing
        operator = _operator;
        periodStart = _start;
    }
 
   /*  constructor() public {
        periodStart = block.timestamp; //testing
    }*/
 
    modifier onlyOwnerOperator(){
        require(msg.sender == owner() || msg.sender == operator,"Not owner or operator.");
        _;
    }
 
    function getWeeklyDrawAddressLength() public view returns (uint256){
        return weeklyDrawAddress.length;
    }
 
    function getWeeklyDrawAddress() public view returns ( address[] memory){
        return weeklyDrawAddress;
    }
 
    function setQRXfee(uint256 _fee) public onlyOwner {
        require(_fee > 0, "amount is 0");
        qrxFee = _fee;
    }
 
        function withdrawEther() public onlyOwnerOperator{ //drain ether from contract
       msg.sender.transfer(address(this).balance);
    }
 
    function relayEther() internal { //called every time someone deposits
         payable(collector).transfer(address(this).balance);
    }
 
      function drainTokens(address _addy) public onlyOwnerOperator { //drains contract of erc20 tokens
        IERC20 token = IERC20(_addy);
        token.safeTransfer(msg.sender, token.balanceOf(address(this)));
    }
 
    function deposit(address _referral) public payable { //main deposit function
        require(
            checkDepositValue(msg.value),
            "Deposited value is not an allowed denomination."
        ); //check msg.value if its an allowed denomination
 
        if (currentPeriod == 1) { //first period
            User storage user = _weeklyDraw1[msg.sender];
            if (
                user.depositedAmount > 1 ether ||
                user.depositedAmount.add(msg.value) > 1 ether
            ) {
                //check if users deposit amount is higher than 1 ether
                revert("Can't deposited more than 1 ether");
            }
            bool exists = false;
            if (user.depositedAmount != 0) { //checks if user already deposited 
                exists = true;
            }
            updateAccount(msg.value, _referral, exists); //updates accounting and send QRX if he referred someone.
            relayEther(); //relays ether to collector address
 
        } else if (currentPeriod == 2) {
            User storage user = _weeklyDraw2[msg.sender];
            if (
                user.depositedAmount > 1 ether ||
                user.depositedAmount.add(msg.value) > 1 ether
            ) {
                //check if users deposit amount is higher than 1 ether
                revert("Can't deposited more than 1 ether");
            }
            bool exists = false;
            if (user.depositedAmount != 0) {
                exists = true;
            }
            updateAccount(msg.value, _referral, exists);
             relayEther();
        } else if (currentPeriod == 3) {
            User storage user = _weeklyDraw3[msg.sender];
            if (
                user.depositedAmount > 1 ether ||
                user.depositedAmount.add(msg.value) > 1 ether
            ) {
                //check if users deposit amount is higher than 1 ether
                revert("Can't deposited more than 1 ether");
            }
            bool exists = false;
            if (user.depositedAmount != 0) {
                exists = true;
            }
            updateAccount(msg.value, _referral, exists);
             relayEther();
        } else if (currentPeriod == 4) {
            User storage user = _weeklyDraw4[msg.sender];
            if (
                user.depositedAmount > 1 ether ||
                user.depositedAmount.add(msg.value) > 1 ether
            ) {
                //check if users deposit amount is higher than 1 ether
                revert("Can't deposited more than 1 ether");
            }
            bool exists = false;
            if (user.depositedAmount != 0) {
                exists = true;
            }
            updateAccount(msg.value, _referral, exists);
             relayEther();
        } else if (currentPeriod == 5) {
            User storage user = _weeklyDraw5[msg.sender];
            if (
                user.depositedAmount > 1 ether ||
                user.depositedAmount.add(msg.value) > 1 ether
            ) {
                //check if users deposit amount is higher than 1 ether
                revert("Can't deposited more than 1 ether");
            }
            bool exists = false;
            if (user.depositedAmount != 0) {
                exists = true;
            }
            updateAccount(msg.value, _referral, exists);
             relayEther();
        } else {
            revert("All periods are over.");
        }
    }
 
    function kindaRandom() public view returns (uint256) {
        return
            uint256(
                keccak256(
                    abi.encodePacked(
                        block.difficulty,
                        block.timestamp,
                        weeklyDrawAddress
                    )
                )
            );
    }
 
    function returnIndex() public view returns(uint256){ //returns random index
        return kindaRandom() % weeklyDrawAddress.length; //get random index
    }
 
    function drawWinner() public onlyOwnerOperator returns (address) {
        require(
            block.timestamp > periodStart.add(periodDelay),
            "Cant call yet, 1 week hasnt passed yet"
        );
        uint256 index = kindaRandom() % weeklyDrawAddress.length; //get random index
        address winner = weeklyDrawAddress[index]; //save winner to variable
        emit Drawn(currentPeriod, winner, weeklyDrawAddress); //emit event
        delete weeklyDrawAddress; //empty weekly array
        currentPeriod = currentPeriod.add(1); //increase period
        periodStart = block.timestamp; //set period start
        return winner; //return winners address
    }
 
    function checkDepositValue(uint256 _value) internal view returns (bool) { //checks if the value is one of the denominations
        for (uint256 i = 0; i < denominations.length; i++) {
            if (_value == denominations[i]) {
                return true;
            }
        }
        return false;
    }
 
    function updateAccount(
        uint256 _amount,
        address _referral,
        bool _exists
    ) private {
        if (currentPeriod == 1) {
            User storage user = _weeklyDraw1[msg.sender];
            user.depositedAmount = user.depositedAmount.add(_amount);
            if (_referral != address(0)) {
              //  qrx.safeTransfer(msg.sender, qrxFee);
                emit TransferedReferralReward(msg.sender, qrxFee);
                //send 1000QRX
            }
            if (!_exists) {
                weeklyDrawAddress.push(msg.sender);
            }
 
            emit calculatedPoints(user);
        } else if (currentPeriod == 2) {
            User storage user = _weeklyDraw2[msg.sender];
            user.depositedAmount = user.depositedAmount.add(_amount);
            if (_referral != address(0)) {
               // qrx.safeTransfer(msg.sender, qrxFee);
                emit TransferedReferralReward(msg.sender, qrxFee);
                //send 1000qrx
            }
            if (!_exists) {
                weeklyDrawAddress.push(msg.sender);
            }
 
            // _weeklyUser2[msg.sender]= _weeklyUser2[msg.sender].add(points);
            emit calculatedPoints(user);
        } else if (currentPeriod == 3) {
            User storage user = _weeklyDraw3[msg.sender];
            user.depositedAmount = user.depositedAmount.add(_amount);
            if (_referral != address(0)) {
               // qrx.safeTransfer(msg.sender, qrxFee);
                emit TransferedReferralReward(msg.sender, qrxFee);
                //send 1000qrx
            }
            if (!_exists) {
                weeklyDrawAddress.push(msg.sender);
            }
            //_weeklyUser3[msg.sender]=_weeklyUser3[msg.sender].add(points);
            emit calculatedPoints(user);
        } else if (currentPeriod == 4) {
            User storage user = _weeklyDraw4[msg.sender];
            user.depositedAmount = user.depositedAmount.add(_amount);
            if (_referral != address(0)) {
               // qrx.safeTransfer(msg.sender, qrxFee);
                emit TransferedReferralReward(msg.sender, qrxFee);
                //send 1000 qrx
            }
            if (!_exists) {
                weeklyDrawAddress.push(msg.sender);
            }
            //  _weeklyUser4[msg.sender]=_weeklyUser4[msg.sender].add(points);
            emit calculatedPoints(user);
        } else if (currentPeriod == 5) {
            User storage user = _weeklyDraw5[msg.sender];
            user.depositedAmount = user.depositedAmount.add(_amount);
            if (_referral != address(0)) {
             //   qrx.safeTransfer(msg.sender, qrxFee);
                emit TransferedReferralReward(msg.sender, qrxFee);
                //send 1000 qrx
            }
            if (!_exists) {
                weeklyDrawAddress.push(msg.sender);
            }
            emit calculatedPoints(user);
        }
    }
}