// File: contracts/TokenDistribution/BasedRewards.sol



// SPDX-License-Identifier: MIT
import "openzeppelin-solidity/contracts/math/Math.sol";
import "./IERC20Detailed.sol";
import "./IRewardDistributionRecipient.sol";
import "./LPTokenWrapper.sol";

// solhint-enable max-line-length
pragma solidity >=0.6.0 <0.8.0;

contract BasedRewards is LPTokenWrapper, IRewardDistributionRecipient {
    IERC20Detailed public blo;
    uint256 public duration;

    uint256 public initreward;
    uint256 public starttime;
    uint256 public periodFinish = 0;
    uint256 public rewardRate = 0;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    uint256 public totalRewards = 0;

    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);

    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }
        _;
    }

    constructor (
        address _b, // staking token address
        address _blo, // reward token address
        uint256 _duration, // reward duration (endTimestamp - startTimestamp)
        uint256 _initreward, // total reward amount
        uint256 _starttime // reward start time
    ) public LPTokenWrapper(_b) {
        blo = IERC20Detailed(_blo);

        duration = _duration;
        starttime = _starttime;
        notifyRewardAmount(_initreward);
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        if (block.timestamp > starttime) {
            return Math.min(block.timestamp, periodFinish);
        }
        return starttime;
    }

    function rewardPerToken() public view returns (uint256) {
        if (totalSupply() == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored.add(
                lastTimeRewardApplicable()
                    .sub(lastUpdateTime)
                    .mul(rewardRate)
                    .mul(1e18)
                    .div(totalSupply())
            );
    }

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

    // stake visibility is public as overriding LPTokenWrapper's stake() function
    function stake(uint256 amount) public override updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        super.stake(amount);
        emit Staked(msg.sender, amount);
    }

    function withdraw(uint256 amount) public override updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        super.withdraw(amount);
        emit Withdrawn(msg.sender, amount);
    }

    function exit() external {
        withdraw(balanceOf(msg.sender));
        getReward();
    }

    function getReward() public updateReward(msg.sender) checkStart {
        uint256 reward = earned(msg.sender);
        if (reward > 0) {
            rewards[msg.sender] = 0;
            blo.safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
            totalRewards = totalRewards.add(reward);
        }
    }

    modifier checkStart(){
        require(block.timestamp > starttime, "Not started");
        _;
    }

    function notifyRewardAmount(uint256 reward)
        internal
        override
        updateReward(address(0))
    {
        rewardRate = reward.div(duration);
        initreward = reward;
        lastUpdateTime = starttime;
        periodFinish = starttime.add(duration);
        emit RewardAdded(reward);
    }
}

// File: openzeppelin-solidity/contracts/math/Math.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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: contracts/TokenDistribution/IERC20Detailed.sol



// SPDX-License-Identifier: MIT

import "openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP including optional functions.
 */
interface IERC20Detailed is IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function name() external view returns (string memory);
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function symbol() external view returns (string memory);
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function decimals() external view returns (uint8);
}
// File: contracts/TokenDistribution/IRewardDistributionRecipient.sol



// SPDX-License-Identifier: MIT

import "openzeppelin-solidity/contracts/access/Ownable.sol";

pragma solidity >=0.6.0 <0.8.0;

abstract contract IRewardDistributionRecipient is Ownable {
    address rewardDistribution;

    function notifyRewardAmount(uint256 reward) internal virtual;

    modifier onlyRewardDistribution() {
        require(_msgSender() == rewardDistribution, "Caller is not reward distribution");
        _;
    }

    function setRewardDistribution(address _rewardDistribution)
        external
        onlyOwner
    {
        rewardDistribution = _rewardDistribution;
    }
}
// File: contracts/TokenDistribution/LPTokenWrapper.sol



// SPDX-License-Identifier: MIT

import "openzeppelin-solidity/contracts/math/SafeMath.sol";
import "openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol";
import "./IERC20Detailed.sol";

pragma solidity >=0.6.0 <0.8.0;

contract LPTokenWrapper {
    using SafeMath for uint256;
    using SafeERC20 for IERC20Detailed;

    IERC20Detailed public b;

    uint256 private _totalSupply;
    mapping(address => uint256) private _balances;

    constructor (address _b) internal {
        b = IERC20Detailed(_b);
    }

    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address account) public view returns (uint256) {
        return _balances[account];
    }

    function stake(uint256 amount) public virtual {
        _totalSupply = _totalSupply.add(amount);
        _balances[msg.sender] = _balances[msg.sender].add(amount);
        b.safeTransferFrom(msg.sender, address(this), amount);
    }

    function withdraw(uint256 amount) public virtual {
        _totalSupply = _totalSupply.sub(amount);
        _balances[msg.sender] = _balances[msg.sender].sub(amount);
        b.safeTransfer(msg.sender, amount);
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
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);

    /**
     * @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-solidity/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/Context.sol";
/**
 * @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.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * 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.
 */
abstract 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 {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the 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 virtual 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 virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: openzeppelin-solidity/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/*
 * @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.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: openzeppelin-solidity/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @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, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, 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 (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @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) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @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) {
        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, reverting 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) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting 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) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * 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, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// File: openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @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 IERC20;` 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));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    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. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "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");
        }
    }
}

// File: openzeppelin-solidity/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @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 v3.4._
     */
    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 v3.4._
     */
    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: contracts/TokenDistribution/TokenVesting.sol



// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;

import "openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol";
import "openzeppelin-solidity/contracts/access/Ownable.sol";
import "openzeppelin-solidity/contracts/math/SafeMath.sol";

/**
 * @title TokenVesting
 * @dev A token holder contract that can release its token balance gradually like a
 * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
 * owner.
 */
contract TokenVesting is Ownable {
    // The vesting schedule is time-based (i.e. using block timestamps as opposed to e.g. block numbers), and is
    // therefore sensitive to timestamp manipulation (which is something miners can do, to a certain degree). Therefore,
    // it is recommended to avoid using short time durations (less than a minute). Typical vesting schemes, with a
    // cliff period of a year and a duration of four years, are safe to use.
    // solhint-disable not-rely-on-time

    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    event TokensReleased(address token, uint256 amount);
    event TokenVestingRevoked(address token);

    // beneficiary of tokens after they are released
    address private _beneficiary;

    // Durations and timestamps are expressed in UNIX time, the same units as block.timestamp.
    uint256 private _cliff;
    uint256 private _start;
    uint256 private _duration;

    bool private _revocable;

    mapping (address => uint256) private _released;
    mapping (address => bool) private _revoked;

    /**
     * @dev Creates a vesting contract that vests its balance of any ERC20 token to the
     * beneficiary, gradually in a linear fashion until start + duration. By then all
     * of the balance will have vested.
     * @param beneficiary address of the beneficiary to whom vested tokens are transferred
     * @param cliffDuration duration in seconds of the cliff in which tokens will begin to vest
     * @param start the time (as Unix time) at which point vesting starts
     * @param duration duration in seconds of the period in which the tokens will vest
     * @param revocable whether the vesting is revocable or not
     */
    constructor (address beneficiary, uint256 start, uint256 cliffDuration, uint256 duration, bool revocable) public {
        require(beneficiary != address(0), "TokenVesting: beneficiary is the zero address");
        // solhint-disable-next-line max-line-length
        require(cliffDuration <= duration, "TokenVesting: cliff is longer than duration");
        require(duration > 0, "TokenVesting: duration is 0");
        // solhint-disable-next-line max-line-length
        require(start.add(duration) > block.timestamp, "TokenVesting: final time is before current time");

        _beneficiary = beneficiary;
        _revocable = revocable;
        _duration = duration;
        _cliff = start.add(cliffDuration);
        _start = start;
    }

    /**
     * @return the beneficiary of the tokens.
     */
    function beneficiary() public view returns (address) {
        return _beneficiary;
    }

    /**
     * @return the cliff time of the token vesting.
     */
    function cliff() public view returns (uint256) {
        return _cliff;
    }

    /**
     * @return the start time of the token vesting.
     */
    function start() public view returns (uint256) {
        return _start;
    }

    /**
     * @return the duration of the token vesting.
     */
    function duration() public view returns (uint256) {
        return _duration;
    }

    /**
     * @return true if the vesting is revocable.
     */
    function revocable() public view returns (bool) {
        return _revocable;
    }

    /**
     * @return the amount of the token released.
     */
    function released(address token) public view returns (uint256) {
        return _released[token];
    }

    /**
     * @return true if the token is revoked.
     */
    function revoked(address token) public view returns (bool) {
        return _revoked[token];
    }

    /**
     * @notice Transfers vested tokens to beneficiary.
     * @param token ERC20 token which is being vested
     */
    function release(IERC20 token) public {
        uint256 unreleased = _releasableAmount(token);

        require(unreleased > 0, "TokenVesting: no tokens are due");

        _released[address(token)] = _released[address(token)].add(unreleased);

        token.safeTransfer(_beneficiary, unreleased);

        emit TokensReleased(address(token), unreleased);
    }

    /**
     * @notice Allows the owner to revoke the vesting. Tokens already vested
     * remain in the contract, the rest are returned to the owner.
     * @param token ERC20 token which is being vested
     */
    function revoke(IERC20 token) public onlyOwner {
        require(_revocable, "TokenVesting: cannot revoke");
        require(!_revoked[address(token)], "TokenVesting: token already revoked");

        uint256 balance = token.balanceOf(address(this));

        uint256 unreleased = _releasableAmount(token);
        uint256 refund = balance.sub(unreleased);

        _revoked[address(token)] = true;

        token.safeTransfer(owner(), refund);

        emit TokenVestingRevoked(address(token));
    }

    /**
     * @dev Calculates the amount that has already vested but hasn't been released yet.
     * @param token ERC20 token which is being vested
     */
    function _releasableAmount(IERC20 token) private view returns (uint256) {
        return _vestedAmount(token).sub(_released[address(token)]);
    }

    /**
     * @dev Calculates the amount that has already vested.
     * @param token ERC20 token which is being vested
     */
    function _vestedAmount(IERC20 token) private view returns (uint256) {
        uint256 currentBalance = token.balanceOf(address(this));
        uint256 totalBalance = currentBalance.add(_released[address(token)]);

        if (block.timestamp < _cliff) {
            return 0;
        } else if (block.timestamp >= _start.add(_duration) || _revoked[address(token)]) {
            return totalBalance;
        } else {
            return totalBalance.mul(block.timestamp.sub(_start)).div(_duration);
        }
    }
}

// File: contracts/UniswapOracle/UniswapConfig.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

import "openzeppelin-solidity/contracts/access/Ownable.sol";

interface CErc20 {
    function underlying() external view returns (address);
}

contract UniswapConfig is Ownable {
    /// @dev Describe how to interpret the fixedPrice in the TokenConfig.
    enum PriceSource {
        FIXED_ETH, /// implies the fixedPrice is a constant multiple of the ETH price (which varies)
        FIXED_USD, /// implies the fixedPrice is a constant multiple of the USD price (which is 1)
        REPORTER   /// implies the price is set by the reporter
    }

    /// @dev Describe how the USD price should be determined for an asset.
    ///  There should be 1 TokenConfig object for each supported asset, passed in the constructor.
    struct TokenConfig {
        address cToken;
        address underlying;
        bytes32 symbolHash;
        uint256 baseUnit;
        PriceSource priceSource;
        uint256 fixedPrice;
        address uniswapMarket;
        bool isUniswapReversed;
    }

    mapping(uint => TokenConfig) public tokens;
    mapping(address => uint) public cTokenIndex;
    mapping(address => uint) public underlyingIndex;
    mapping(bytes32 => uint) public symbolHashIndex;

    /// @notice The number of tokens this contract actually supports
    uint public numTokens;

    function _addTokensInternal(TokenConfig[] memory configs) internal {
        for (uint i = 0; i < configs.length; i++) {
            // +1 so index 0 stays empty
            uint index = i + numTokens + 1;
            tokens[index] = configs[i];
            cTokenIndex[configs[i].cToken] = index;
            underlyingIndex[configs[i].underlying] = index;
            symbolHashIndex[configs[i].symbolHash] = index;
        }

        numTokens = numTokens + configs.length;
    }

    function getCTokenIndex(address cToken) internal view returns (uint) {
        return cTokenIndex[cToken];
    }

    function getUnderlyingIndex(address underlying) internal view returns (uint) {
        return underlyingIndex[underlying];
    }

    function getSymbolHashIndex(bytes32 symbolHash) internal view returns (uint) {
        return symbolHashIndex[symbolHash];
    }

    /**
     * @notice Get the i-th config, according to the order they were passed in originally
     * @param i The index of the config to get
     * @return The config object
     */
    function getTokenConfig(uint i) public view returns (TokenConfig memory) {
        require(i <= numTokens, "token config not found");

        return tokens[i];
    }

    /**
     * @notice Get the config for symbol
     * @param symbol The symbol of the config to get
     * @return The config object
     */
    function getTokenConfigBySymbol(string memory symbol) public view returns (TokenConfig memory) {
        return getTokenConfigBySymbolHash(keccak256(abi.encodePacked(symbol)));
    }

    /**
     * @notice Get the config for the symbolHash
     * @param symbolHash The keccack256 of the symbol of the config to get
     * @return The config object
     */
    function getTokenConfigBySymbolHash(bytes32 symbolHash) public view returns (TokenConfig memory) {
        uint index = getSymbolHashIndex(symbolHash);
        if (index != 0) {
            return getTokenConfig(index);
        }

        revert("token config not found");
    }

    /**
     * @notice Get the config for the cToken
     * @dev If a config for the cToken is not found, falls back to searching for the underlying.
     * @param cToken The address of the cToken of the config to get
     * @return The config object
     */
    function getTokenConfigByCToken(address cToken) public view returns (TokenConfig memory) {
        uint index = getCTokenIndex(cToken);
        if (index != 0) {
            return getTokenConfig(index);
        }

        return getTokenConfigByUnderlying(CErc20(cToken).underlying());
    }

    /**
     * @notice Get the config for an underlying asset
     * @param underlying The address of the underlying asset of the config to get
     * @return The config object
     */
    function getTokenConfigByUnderlying(address underlying) public view returns (TokenConfig memory) {
        uint index = getUnderlyingIndex(underlying);
        if (index != 0) {
            return getTokenConfig(index);
        }

        revert("token config not found");
    }
}

// File: contracts/UniswapOracle/UniswapAnchoredView.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;
pragma experimental ABIEncoderV2;

import "./UniswapConfig.sol";
import "./UniswapLib.sol";

struct Observation {
    uint timestamp;
    uint acc;
}

contract UniswapAnchoredView is UniswapConfig {
    using FixedPoint for *;

    /// @notice The number of wei in 1 ETH
    uint public constant ethBaseUnit = 1e18;

    /// @notice A common scaling factor to maintain precision
    uint public constant expScale = 1e18;

    /// @notice The minimum amount of time in seconds required for the old uniswap price accumulator to be replaced
    uint public immutable anchorPeriod;

    /// @notice Official prices by symbol hash
    mapping(bytes32 => uint) public prices;

    /// @notice The old observation for each symbolHash
    mapping(bytes32 => Observation) public oldObservations;

    /// @notice The new observation for each symbolHash
    mapping(bytes32 => Observation) public newObservations;

    /// @notice The event emitted when anchor price is updated
    event AnchorPriceUpdated(address cToken, uint anchorPrice, uint oldTimestamp, uint newTimestamp);

    /// @notice The event emitted when the uniswap window changes
    event UniswapWindowUpdated(bytes32 indexed symbolHash, uint oldTimestamp, uint newTimestamp, uint oldPrice, uint newPrice);

    bytes32 public immutable nativeTokenHash;
    bytes32 constant rotateHash = keccak256(abi.encodePacked("rotate"));

    /**
     * @notice Construct a uniswap anchored view for a set of token configurations
     * @dev Note that to avoid immature TWAPs, the system must run for at least a single anchorPeriod before using.
     * @param anchorPeriod_ The minimum amount of time required for the old uniswap price accumulator to be replaced
     */
    constructor(uint anchorPeriod_, string memory nativeTokenSymbol_) public {
        anchorPeriod = anchorPeriod_;
        nativeTokenHash = keccak256(abi.encodePacked(nativeTokenSymbol_));
    }

    function addTokens(TokenConfig[] memory configs) public onlyOwner {
        for (uint i = 0; i < configs.length; i++) {
            TokenConfig memory config = configs[i];
            bytes32 symbolHash = config.symbolHash;
            require(config.baseUnit > 0, "baseUnit must be greater than zero");
            require(newObservations[symbolHash].timestamp == uint(0), "cannot change current token");
            address uniswapMarket = config.uniswapMarket;
            if (config.priceSource == PriceSource.REPORTER) {
                require(uniswapMarket != address(0), "reported prices must have an anchor");
                uint cumulativePrice = currentCumulativePrice(config);
                oldObservations[symbolHash].timestamp = block.timestamp;
                newObservations[symbolHash].timestamp = block.timestamp;
                oldObservations[symbolHash].acc = cumulativePrice;
                newObservations[symbolHash].acc = cumulativePrice;
                emit UniswapWindowUpdated(symbolHash, block.timestamp, block.timestamp, cumulativePrice, cumulativePrice);
            } else {
                require(uniswapMarket == address(0), "only reported prices utilize an anchor");
            }
        }

        _addTokensInternal(configs);
    }

    /**
     * @notice Get the official price for a symbol
     * @param symbol The symbol to fetch the price of
     * @return Price denominated in USD, with 6 decimals
     */
    function price(string memory symbol) external view returns (uint) {
        TokenConfig memory config = getTokenConfigBySymbol(symbol);
        if (config.priceSource == PriceSource.REPORTER) return prices[config.symbolHash];
        if (config.priceSource == PriceSource.FIXED_USD) return config.fixedPrice;
        if (config.priceSource == PriceSource.FIXED_ETH) {
            uint usdPerEth = prices[nativeTokenHash];
            require(usdPerEth > 0, "ETH price not set, cannot convert to dollars");
            return mul(usdPerEth, config.fixedPrice) / ethBaseUnit;
        }
        return 0;
    }

    function priceInternal(TokenConfig memory config) internal returns (uint) {
        if (config.priceSource == PriceSource.REPORTER) {
            Observation memory newObservation = newObservations[config.symbolHash];
            // Update new and old observations if elapsed time is greater than or equal to anchor period
            uint timeElapsed = block.timestamp - newObservation.timestamp;
            if (timeElapsed >= anchorPeriod || prices[config.symbolHash] == 0) {
                postPriceInternal(config);
            }
            return prices[config.symbolHash];
        }
        if (config.priceSource == PriceSource.FIXED_USD) return config.fixedPrice;
        if (config.priceSource == PriceSource.FIXED_ETH) {
            uint usdPerEth = prices[nativeTokenHash];
            require(usdPerEth > 0, "ETH price not set, cannot convert to dollars");
            return mul(usdPerEth, config.fixedPrice) / ethBaseUnit;
        }
    }

    /**
     * @notice Get the underlying price of a cToken
     * @dev Implements the PriceOracle interface for Compound v2.
     * @param cToken The cToken address for price retrieval
     * @return Price denominated in USD, with 18 decimals, for the given cToken address
     */
    function getUnderlyingPriceView(address cToken) external view returns (uint) {
        TokenConfig memory config = getTokenConfigByCToken(cToken);
        uint price;
        if (config.priceSource == PriceSource.REPORTER) price = prices[config.symbolHash];
        if (config.priceSource == PriceSource.FIXED_USD) price = config.fixedPrice;
        if (config.priceSource == PriceSource.FIXED_ETH) {
            uint usdPerEth = prices[nativeTokenHash];
            require(usdPerEth > 0, "ETH price not set, cannot convert to dollars");
            price = mul(usdPerEth, config.fixedPrice) / ethBaseUnit;
        }
         // Comptroller needs prices in the format: ${raw price} * 1e(36 - baseUnit)
         // Since the prices in this view have 6 decimals, we must scale them by 1e(36 - 6 - baseUnit)
        return mul(1e30, price) / config.baseUnit;
    }

    /**
     * @notice Get the underlying price of a cToken
     * @dev Implements the PriceOracle interface for Compound v2.
     * @param cToken The cToken address for price retrieval
     * @return Price denominated in USD, with 18 decimals, for the given cToken address
     */
    function getUnderlyingPrice(address cToken) external returns (uint) {
        TokenConfig memory config = getTokenConfigByCToken(cToken);
         // Comptroller needs prices in the format: ${raw price} * 1e(36 - baseUnit)
         // Since the prices in this view have 6 decimals, we must scale them by 1e(36 - 6 - baseUnit)
        return mul(1e30, priceInternal(config)) / config.baseUnit;
    }

    function postPriceInternal(TokenConfig memory config) internal {
        uint ethPrice = fetchEthPrice();

        uint anchorPrice;
        if (config.symbolHash == nativeTokenHash) {
            anchorPrice = ethPrice;
        } else {
            anchorPrice = fetchAnchorPrice(config, ethPrice);
        }

        prices[config.symbolHash] = anchorPrice;
    }

    /**
     * @dev Fetches the current token/eth price accumulator from uniswap.
     */
    function currentCumulativePrice(TokenConfig memory config) internal view returns (uint) {
        (uint cumulativePrice0, uint cumulativePrice1,) = UniswapV2OracleLibrary.currentCumulativePrices(config.uniswapMarket);
        if (config.isUniswapReversed) {
            return cumulativePrice1;
        } else {
            return cumulativePrice0;
        }
    }

    /**
     * @dev Fetches the current eth/usd price from uniswap, with 6 decimals of precision.
     *  Conversion factor is 1e18 for eth/usdc market, since we decode uniswap price statically with 18 decimals.
     */
    function fetchEthPrice() internal returns (uint) {
        return fetchAnchorPrice(getTokenConfigBySymbolHash(nativeTokenHash), ethBaseUnit);
    }

    /**
     * @dev Fetches the current token/usd price from uniswap, with 6 decimals of precision.
     * @param conversionFactor 1e18 if seeking the ETH price, and a 6 decimal ETH-USDC price in the case of other assets
     */
    function fetchAnchorPrice(TokenConfig memory config, uint conversionFactor) internal virtual returns (uint) {
        (uint nowCumulativePrice, uint oldCumulativePrice, uint oldTimestamp) = pokeWindowValues(config);

        // This should be impossible, but better safe than sorry
        require(block.timestamp > oldTimestamp, "now must come after before");
        uint timeElapsed = block.timestamp - oldTimestamp;

        // Calculate uniswap time-weighted average price
        // Underflow is a property of the accumulators: https://uniswap.org/audit.html#orgc9b3190
        FixedPoint.uq112x112 memory priceAverage = FixedPoint.uq112x112(uint224((nowCumulativePrice - oldCumulativePrice) / timeElapsed));
        uint rawUniswapPriceMantissa = priceAverage.decode112with18();
        uint unscaledPriceMantissa = mul(rawUniswapPriceMantissa, conversionFactor);
        uint anchorPrice;

        // Adjust rawUniswapPrice according to the units of the non-ETH asset
        // In the case of ETH, we would have to scale by 1e6 / USDC_UNITS, but since baseUnit2 is 1e6 (USDC), it cancels
        anchorPrice = mul(unscaledPriceMantissa, config.baseUnit) / ethBaseUnit / expScale;

        emit AnchorPriceUpdated(config.cToken, anchorPrice, oldTimestamp, block.timestamp);

        return anchorPrice;
    }

    /**
     * @dev Get time-weighted average prices for a token at the current timestamp.
     *  Update new and old observations of lagging window if period elapsed.
     */
    function pokeWindowValues(TokenConfig memory config) internal returns (uint, uint, uint) {
        bytes32 symbolHash = config.symbolHash;
        uint cumulativePrice = currentCumulativePrice(config);

        Observation memory newObservation = newObservations[symbolHash];

        // Update new and old observations if elapsed time is greater than or equal to anchor period
        uint timeElapsed = block.timestamp - newObservation.timestamp;
        if (timeElapsed >= anchorPeriod) {
            oldObservations[symbolHash].timestamp = newObservation.timestamp;
            oldObservations[symbolHash].acc = newObservation.acc;

            newObservations[symbolHash].timestamp = block.timestamp;
            newObservations[symbolHash].acc = cumulativePrice;
            emit UniswapWindowUpdated(config.symbolHash, newObservation.timestamp, block.timestamp, newObservation.acc, cumulativePrice);
        }
        return (cumulativePrice, oldObservations[symbolHash].acc, oldObservations[symbolHash].timestamp);
    }

    /// @dev Overflow proof multiplication
    function mul(uint a, uint b) internal pure returns (uint) {
        if (a == 0) return 0;
        uint c = a * b;
        require(c / a == b, "multiplication overflow");
        return c;
    }
}

// File: contracts/UniswapOracle/UniswapLib.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;
// Based on code from https://github.com/Uniswap/uniswap-v2-periphery

// a library for handling binary fixed point numbers (https://en.wikipedia.org/wiki/Q_(number_format))
library FixedPoint {
    // range: [0, 2**112 - 1]
    // resolution: 1 / 2**112
    struct uq112x112 {
        uint224 _x;
    }

    // returns a uq112x112 which represents the ratio of the numerator to the denominator
    // equivalent to encode(numerator).div(denominator)
    function fraction(uint112 numerator, uint112 denominator) internal pure returns (uq112x112 memory) {
        require(denominator > 0, "FixedPoint: DIV_BY_ZERO");
        return uq112x112((uint224(numerator) << 112) / denominator);
    }

    // decode a uq112x112 into a uint with 18 decimals of precision
    function decode112with18(uq112x112 memory self) internal pure returns (uint) {
        // we only have 256 - 224 = 32 bits to spare, so scaling up by ~60 bits is dangerous
        // instead, get close to:
        //  (x * 1e18) >> 112
        // without risk of overflowing, e.g.:
        //  (x) / 2 ** (112 - lg(1e18))
        return uint(self._x) / 5192296858534827;
    }
}

// library with helper methods for oracles that are concerned with computing average prices
library UniswapV2OracleLibrary {
    using FixedPoint for *;

    // helper function that returns the current block timestamp within the range of uint32, i.e. [0, 2**32 - 1]
    function currentBlockTimestamp() internal view returns (uint32) {
        return uint32(block.timestamp % 2 ** 32);
    }

    // produces the cumulative price using counterfactuals to save gas and avoid a call to sync.
    function currentCumulativePrices(
        address pair
    ) internal view returns (uint price0Cumulative, uint price1Cumulative, uint32 blockTimestamp) {
        blockTimestamp = currentBlockTimestamp();
        price0Cumulative = IUniswapV2Pair(pair).price0CumulativeLast();
        price1Cumulative = IUniswapV2Pair(pair).price1CumulativeLast();

        // if time has elapsed since the last update on the pair, mock the accumulated price values
        (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast) = IUniswapV2Pair(pair).getReserves();
        if (blockTimestampLast != blockTimestamp) {
            // subtraction overflow is desired
            uint32 timeElapsed = blockTimestamp - blockTimestampLast;
            // addition overflow is desired
            // counterfactual
            price0Cumulative += uint(FixedPoint.fraction(reserve1, reserve0)._x) * timeElapsed;
            // counterfactual
            price1Cumulative += uint(FixedPoint.fraction(reserve0, reserve1)._x) * timeElapsed;
        }
    }
}

interface IUniswapV2Pair {
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
}