// File: @rarible/staking/contracts/RariMineV3.sol



// SPDX-License-Identifier: MIT

/**
 *Submitted for verification at Etherscan.io on 2020-07-20
 */

pragma solidity 0.7.6;
pragma abicoder v2;

import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/token/ERC20/IERC20Upgradeable.sol";

import "./libs/LibString.sol";
import "./libs/LibAddress.sol";
import "./libs/LibUint.sol";
import "./libs/LibStakingMath.sol";
import "./IRariMine.sol";
import "./IStaking.sol";

contract RariMineV3 is OwnableUpgradeable, IRariMine {
    using SafeMathUpgradeable for uint256;
    using LibString for string;
    using LibUint for uint256;
    using LibAddress for address;

    IERC20Upgradeable public token;
    address public tokenOwner;
    IStaking public staking;

    uint256 public claimFormulaClaim;
    uint256 public claimCliffWeeks;
    uint256 public claimSlopeWeeks;
    uint256 constant CLAIM_FORMULA_DIVIDER = 10000;

    uint8 public constant VERSION = 1;

    mapping(address => uint256) public claimed;

    address public signer;

    event SetClaimFormulaClaim(uint256 indexed newClaimFormulaClaim);
    event SetClaimCliffWeeks(uint256 indexed newClaimCliffWeeks);
    event SetClaimSlopeWeeks(uint256 indexed newClaimSlopeWeeks);
    event SetNewTokenOwner(address indexed newTokenOwner);
    event SetNewStaking(address indexed newStaking);
    event SetNewSigner(address indexed newSigner);

    function __RariMineV3_init(
        IERC20Upgradeable _token,
        address _tokenOwner,
        IStaking _staking,
        uint256 _claimCliffWeeks,
        uint256 _claimSlopeWeeks,
        uint256 _claimFormulaClaim
    ) external initializer {
        __RariMineV3_init_unchained(_token, _tokenOwner, _staking, _claimCliffWeeks, _claimSlopeWeeks, _claimFormulaClaim);
        __Ownable_init_unchained();
        __Context_init_unchained();
    }

    function __RariMineV3_init_unchained(
        IERC20Upgradeable _token,
        address _tokenOwner,
        IStaking _staking,
        uint256 _claimCliffWeeks,
        uint256 _claimSlopeWeeks,
        uint256 _claimFormulaClaim
    ) internal initializer {
        token = _token;
        tokenOwner = _tokenOwner;
        staking = _staking;
        claimCliffWeeks = _claimCliffWeeks;
        claimSlopeWeeks = _claimSlopeWeeks;
        claimFormulaClaim = _claimFormulaClaim;
        signer = _msgSender();
    }

    function claim(
        Balance memory _balance,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public {
        require(prepareMessage(_balance, address(this)).recover(v, r, s) == signer, "signer should sign balances");

        address recipient = _balance.recipient;
        if (_msgSender() == recipient) {
            uint256 toClaim = _balance.value.sub(claimed[recipient], "nothing to claim");
            require(toClaim > 0, "nothing to claim");
            claimed[recipient] = _balance.value;

            // claim rari tokens
            uint256 claimAmount = toClaim.mul(claimFormulaClaim).div(CLAIM_FORMULA_DIVIDER);
            if (claimAmount > 0) {
                require(token.transferFrom(tokenOwner, recipient, claimAmount), "transfer to msg sender is not successful");
                emit Claim(recipient, claimAmount);
                emit Value(recipient, _balance.value);
            }

            // stake some tokens
            uint256 stakeAmount = toClaim.sub(claimAmount);
            if(stakeAmount > 0) {
                require(token.transferFrom(tokenOwner, address(this), stakeAmount), "transfer to RariMine is not successful");
                require(token.approve(address(staking), stakeAmount), "approve is not successful");
                staking.stake(recipient, recipient, stakeAmount, claimSlopeWeeks, claimCliffWeeks);
            }

            return;
        }

        revert("_msgSender() is not the receipient");
    }

    function doOverride(Balance[] memory _balances) public onlyOwner {
        for (uint256 i = 0; i < _balances.length; i++) {
            claimed[_balances[i].recipient] = _balances[i].value;
            emit Value(_balances[i].recipient, _balances[i].value);
        }
    }

    function prepareMessage(Balance memory _balance, address _address) internal pure returns (string memory) {
        uint256 id;
        assembly {
            id := chainid()
        }
        return toString(keccak256(abi.encode(_balance, _address, VERSION, id)));
    }

    function toString(bytes32 value) internal pure returns (string memory) {
        bytes memory alphabet = "0123456789abcdef";
        bytes memory str = new bytes(64);
        for (uint256 i = 0; i < 32; i++) {
            str[i * 2] = alphabet[uint8(value[i] >> 4)];
            str[1 + i * 2] = alphabet[uint8(value[i] & 0x0f)];
        }
        return string(str);
    }

    function setTokenOwner(address newTokenOwner) external onlyOwner {
        tokenOwner = newTokenOwner;
        emit SetNewTokenOwner(newTokenOwner);
    }

    function setClaimFormulaClaim(uint256 newClaimFormulaClaim) external onlyOwner {
        claimFormulaClaim = newClaimFormulaClaim;
        emit SetClaimCliffWeeks(newClaimFormulaClaim);
    }

    function setClaimCliffWeeks(uint256 newClaimCliffWeeks) external onlyOwner {
        claimCliffWeeks = newClaimCliffWeeks;
        emit SetClaimCliffWeeks(newClaimCliffWeeks);
    }

    function setClaimSlopeWeeks(uint256 newClaimSlopeWeeks) external onlyOwner {
        claimSlopeWeeks = newClaimSlopeWeeks;
        emit SetClaimCliffWeeks(newClaimSlopeWeeks);
    }

    function setStaking(address newStaking) external onlyOwner {
        staking = IStaking(newStaking);
        emit SetNewStaking(newStaking);
    }

    function setSigner(address newSigner) external onlyOwner {
        signer = newSigner;
        emit SetNewSigner(newSigner);
    }

    uint256[47] private __gap;
}

// File: @rarible/staking/contracts/libs/LibUint.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;

import "@openzeppelin/contracts-upgradeable/math/SafeMathUpgradeable.sol";

library LibUint {
    using SafeMathUpgradeable for uint256;

    function toString(uint256 _i) internal pure returns (string memory) {
        if (_i == 0) {
            return "0";
        }
        uint j = _i;
        uint len;
        while (j != 0) {
            len++;
            j /= 10;
        }
        bytes memory bstr = new bytes(len);
        uint k = len - 1;
        while (_i != 0) {
            bstr[k--] = byte(uint8(48 + _i % 10));
            _i /= 10;
        }
        return string(bstr);
    }
}
// File: @rarible/staking/contracts/libs/LibString.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;

import "./LibUint.sol";

library LibString {
    using LibUint for uint256;

    function append(string memory _a, string memory _b) internal pure returns (string memory) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory bab = new bytes(_ba.length + _bb.length);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) bab[k++] = _ba[i];
        for (uint i = 0; i < _bb.length; i++) bab[k++] = _bb[i];
        return string(bab);
    }

    function append(string memory _a, string memory _b, string memory _c) internal pure returns (string memory) {
        bytes memory _ba = bytes(_a);
        bytes memory _bb = bytes(_b);
        bytes memory _bc = bytes(_c);
        bytes memory bbb = new bytes(_ba.length + _bb.length + _bc.length);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) bbb[k++] = _ba[i];
        for (uint i = 0; i < _bb.length; i++) bbb[k++] = _bb[i];
        for (uint i = 0; i < _bc.length; i++) bbb[k++] = _bc[i];
        return string(bbb);
    }

    function recover(string memory message, uint8 v, bytes32 r, bytes32 s) internal pure returns (address) {
        bytes memory msgBytes = bytes(message);
        bytes memory fullMessage = concat(
            bytes("\x19Ethereum Signed Message:\n"),
            bytes(msgBytes.length.toString()),
            msgBytes,
            new bytes(0), new bytes(0), new bytes(0), new bytes(0)
        );
        return ecrecover(keccak256(fullMessage), v, r, s);
    }

    function concat(bytes memory _ba, bytes memory _bb, bytes memory _bc, bytes memory _bd, bytes memory _be, bytes memory _bf, bytes memory _bg) internal pure returns (bytes memory) {
        bytes memory resultBytes = new bytes(_ba.length + _bb.length + _bc.length + _bd.length + _be.length + _bf.length + _bg.length);
        uint k = 0;
        for (uint i = 0; i < _ba.length; i++) resultBytes[k++] = _ba[i];
        for (uint i = 0; i < _bb.length; i++) resultBytes[k++] = _bb[i];
        for (uint i = 0; i < _bc.length; i++) resultBytes[k++] = _bc[i];
        for (uint i = 0; i < _bd.length; i++) resultBytes[k++] = _bd[i];
        for (uint i = 0; i < _be.length; i++) resultBytes[k++] = _be[i];
        for (uint i = 0; i < _bf.length; i++) resultBytes[k++] = _bf[i];
        for (uint i = 0; i < _bg.length; i++) resultBytes[k++] = _bg[i];
        return resultBytes;
    }
}
// File: @rarible/staking/contracts/libs/LibStakingMath.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;
pragma abicoder v2;

import "@openzeppelin/contracts-upgradeable/math/SafeMathUpgradeable.sol";

library LibStakingMath {
    using SafeMathUpgradeable for uint;

    function divUp(uint a, uint b) internal pure returns (uint) {
        return ((a.sub(1)).div(b)).add(1);
    }
}

// File: @rarible/staking/contracts/libs/LibAddress.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;

import "@openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol";

library LibAddress {
    using AddressUpgradeable for address;

    function toString(address _addr) internal pure returns (string memory) {
        bytes32 value = bytes32(uint256(_addr));
        bytes memory alphabet = "0123456789abcdef";
        bytes memory str = new bytes(42);
        str[0] = '0';
        str[1] = 'x';
        for (uint256 i = 0; i < 20; i++) {
            str[2+i*2] = alphabet[uint8(value[i + 12] >> 4)];
            str[3+i*2] = alphabet[uint8(value[i + 12] & 0x0f)];
        }
        return string(str);
    }
}
// File: @rarible/staking/contracts/IStaking.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.9 <0.8.0;
pragma abicoder v2;

interface IStaking {
    function stake(
        address account,
        address delegate,
        uint amount,
        uint slope,
        uint cliff
    ) external returns (uint);
}
// File: @rarible/staking/contracts/IRariMine.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.7.6;
pragma abicoder v2;


interface IRariMine {
    event Claim(address indexed owner, uint value);
    event Value(address indexed owner, uint value);

    struct Balance {
        address recipient;
        uint256 value;
    }
}

// File: @openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;
import "../proxy/Initializable.sol";

/*
 * @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 ContextUpgradeable is Initializable {
    function __Context_init() internal initializer {
        __Context_init_unchained();
    }

    function __Context_init_unchained() internal initializer {
    }
    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;
    }
    uint256[50] private __gap;
}

// File: @openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library AddressUpgradeable {
    /**
     * @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);
    }

    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-upgradeable/token/ERC20/IERC20Upgradeable.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 IERC20Upgradeable {
    /**
     * @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/contracts-upgradeable/proxy/Initializable.sol



// SPDX-License-Identifier: MIT

// solhint-disable-next-line compiler-version
pragma solidity >=0.4.24 <0.8.0;

import "../utils/AddressUpgradeable.sol";

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {UpgradeableProxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function _isConstructor() private view returns (bool) {
        return !AddressUpgradeable.isContract(address(this));
    }
}

// File: @openzeppelin/contracts-upgradeable/math/SafeMathUpgradeable.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 SafeMathUpgradeable {
    /**
     * @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/contracts-upgradeable/access/OwnableUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/ContextUpgradeable.sol";
import "../proxy/Initializable.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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal initializer {
        __Context_init_unchained();
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal initializer {
        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;
    }
    uint256[49] private __gap;
}