// File: contracts/staking/StablzLiquidityMining.sol



//SPDX-License-Identifier: Unlicense
pragma solidity = 0.8.9;

import "@uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol";
import "contracts/staking/common/StablzStaking.sol";
import "contracts/access/OracleManaged.sol";

/// @title Stablz liquidity mining
contract StablzLiquidityMining is StablzStaking, OracleManaged {

    uint public constant MAXIMUM_LIFETIME_PERIOD = 30 days;

    uint public lpPrice;
    uint public lpPriceExpiresAt;

    event LPValueUpdated(uint lpPrice, uint lpPriceExpiresAt);

    /// @param _oracle Oracle address
    /// @param _lpToken LP token address
    /// @param _stablz Stablz token
    /// @param _totalRewards Total rewards allocated for the contract
    /// @param _minimumDeposit Minimum deposit amount
    /// @param _apr1Month APR for 1 month to 1 d.p. e.g. 80 = 8%
    /// @param _apr3Month APR for 3 month to 1 d.p. e.g. 120 = 12%
    /// @param _apr6Month APR for 6 month to 1 d.p. e.g. 200 = 20%
    /// @param _apr12Month APR for 12 month to 1 d.p. e.g. 365 = 36.5%
    constructor(
        address _oracle,
        address _lpToken,
        address _stablz,
        uint _totalRewards,
        uint _minimumDeposit,
        uint _apr1Month,
        uint _apr3Month,
        uint _apr6Month,
        uint _apr12Month
    ) StablzStaking(_lpToken, _stablz, _totalRewards, _minimumDeposit, _apr1Month, _apr3Month, _apr6Month, _apr12Month) {
        _setOracle(_oracle);
        IUniswapV2Pair lpToken = IUniswapV2Pair(_lpToken);
        require(lpToken.token0() == _stablz || lpToken.token1() == _stablz, "StablzLiquidityMining: _lpToken pair does not contain _stablz");
    }

    /// @notice Get value of LP in Stablz based on oracle/owner defined price
    /// @param _amount Amount of LP
    /// @return uint Equivalent value of _amount in Stablz
    function getLPValue(uint _amount) external view returns (uint) {
        if (_isLPPriceValid()) {
            return _getLPValue(_amount);
        }
        return 0;
    }

    /// @notice Set LP price and lifetime for this price
    /// @param _lpPrice Amount of Stablz for 1 LP token
    /// @param _lifeTimePeriod Lifetime period for _lpPrice, in seconds. Cannot be greater than the maximum lifetime period
    function setLPValue(uint _lpPrice, uint _lifeTimePeriod) external onlyOwnerOrOracle {
        require(_lpPrice > 0, "StablzLiquidityMining: _lpPrice cannot be zero");
        require(_lifeTimePeriod <= MAXIMUM_LIFETIME_PERIOD, "StablzLiquidityMining: _lifeTimePeriod is greater than the maximum lifetime period");
        lpPrice = _lpPrice;
        lpPriceExpiresAt = block.timestamp + _lifeTimePeriod;
        emit LPValueUpdated(lpPrice, lpPriceExpiresAt);
    }

    /// @dev Calculate the rewards earned at the end of the lockup period for a given amount of LP, reverts if LP price has expired
    function _calculateReward(uint _amount, uint _lockUpPeriodType) internal override view returns (uint reward) {
        /// @dev convert LP amount to Stablz
        require(_isLPPriceValid(), "StablzLiquidityMining: LP price has expired");
        uint stablzAmount = _getLPValue(_amount);
        uint period = getLockUpPeriod(_lockUpPeriodType);
        uint apr = getAPR(_lockUpPeriodType);
        return stablzAmount * apr * period / (365 days * APR_DENOMINATOR);
    }

    /// @dev get LP amount in Stablz
    function _getLPValue(uint _amount) internal view returns (uint) {
        return _amount * lpPrice / 1 ether;
    }

    /// @dev LP price is valid if the current time is less than or equal to the expiration date
    function _isLPPriceValid() internal view returns (bool) {
        return block.timestamp <= lpPriceExpiresAt;
    }

    /// @dev no receipt token to give
    function _giveReceipt(address, uint) internal override {}

    /// @dev no receipt token to take
    function _takeReceipt(address, uint) internal override {}
}

// File: contracts/access/OracleManaged.sol



//SPDX-License-Identifier: Unlicense
pragma solidity = 0.8.9;

import "@openzeppelin/contracts/access/Ownable.sol";

/// @title OracleManaged
contract OracleManaged is Ownable {

    address private _oracle;

    event OracleUpdated(address indexed prev, address indexed next);

    modifier onlyOracle {
        require(_msgSender() == _oracle, "OracleManaged: caller is not the Oracle");
        _;
    }

    modifier onlyOwnerOrOracle() {
        require(_msgSender() == owner() || _msgSender() == _oracle, "OracleManaged: Only the owner or oracle can call this function");
        _;
    }

    /// @notice Get Oracle address
    /// @return address Oracle address
    function oracle() public view returns (address) {
        return _oracle;
    }

    /// @notice Set Oracle address
    /// @param _newOracle New Oracle address
    function setOracle(address _newOracle) external onlyOwner {
        _setOracle(_newOracle);
    }

    /// @dev Set Oracle address and emit event with previous and new address
    /// @param _newOracle New Oracle address
    function _setOracle(address _newOracle) internal {
        require(_newOracle != address(0), "OracleManaged: _newOracle cannot be the zero address");
        address prev = _oracle;
        _oracle = _newOracle;
        emit OracleUpdated(prev, _newOracle);
    }
}

// File: contracts/staking/common/StablzStaking.sol



//SPDX-License-Identifier: Unlicense
pragma solidity = 0.8.9;

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

/// @title Stablz staking
abstract contract StablzStaking is Ownable, ReentrancyGuard {

    using SafeERC20 for IERC20;

    address public immutable stakingToken;
    address public immutable rewardToken;
    uint public immutable totalRewards;
    uint public totalAvailable;
    bool public initialized;
    bool public isDepositingEnabled;

    uint public minimumDeposit;

    uint public immutable apr1Month;
    uint public immutable apr3Month;
    uint public immutable apr6Month;
    uint public immutable apr12Month;
    uint internal constant APR_DENOMINATOR = 1000;

    struct Stake {
        uint lockUpPeriodType;
        uint stakedAt;
        uint amount;
        uint amountWithdrawn;
        uint allocatedRewards;
        uint claimedRewards;
    }

    mapping(address => Stake[]) private _userStakes;

    /// @param _lockUpPeriodType Lock up period type
    modifier onlyValidLockPeriod(uint _lockUpPeriodType) {
        require(_lockUpPeriodType <= 3, "StablzStaking: Invalid lock period");
        _;
    }

    /// @param _user User address
    /// @param _stakeId Stake ID
    modifier onlyValidStakeId(address _user, uint _stakeId) {
        Stake[] memory stakes = _userStakes[_user];
        require(_stakeId < stakes.length && stakes[_stakeId].amount != 0, "StablzStaking: Invalid stake ID");
        _;
    }

    modifier onlyIfInitialized() {
        require(initialized, "StablzStaking: Contract not initialized");
        _;
    }

    event Deposit(address user, uint stakeId, uint amount, uint lockUpPeriodType);
    event Withdraw(address user, uint stakeId, uint amount);
    event RewardsClaimed(address user, uint stakeId, uint rewards);
    event Initialized();
    event DepositingEnabled();
    event DepositingDisabled();
    event MinimumDepositUpdated(uint minimumDeposit);

    /// @param _stakingToken Token used for staking
    /// @param _rewardToken Token used for rewards
    /// @param _totalRewards Total rewards allocated for the contract
    /// @param _minimumDeposit Minimum deposit amount
    /// @param _apr1Month APR for 1 month to 1 d.p. e.g. 80 = 8%
    /// @param _apr3Month APR for 3 month to 1 d.p. e.g. 120 = 12%
    /// @param _apr6Month APR for 6 month to 1 d.p. e.g. 200 = 20%
    /// @param _apr12Month APR for 12 month to 1 d.p. e.g. 365 = 36.5%
    constructor(address _stakingToken, address _rewardToken, uint _totalRewards, uint _minimumDeposit, uint _apr1Month, uint _apr3Month, uint _apr6Month, uint _apr12Month) {
        require(_stakingToken != address(0), "StablzStaking: _stakingToken cannot be the zero address");
        require(_rewardToken != address(0), "StablzStaking: _rewardToken cannot be the zero address");
        stakingToken = _stakingToken;
        rewardToken = _rewardToken;
        totalRewards = _totalRewards;
        minimumDeposit = _minimumDeposit;
        apr1Month = _apr1Month;
        apr3Month = _apr3Month;
        apr6Month = _apr6Month;
        apr12Month = _apr12Month;
    }

    /// @notice Initialize the contract by funding it with rewards, requires approval prior to calling
    function initialize() external onlyOwner {
        require(!initialized, "StablzStaking: Already initialized");
        initialized = true;
        totalAvailable = totalRewards;
        uint rewardBalance = IERC20(rewardToken).balanceOf(address(this));
        if (rewardBalance < totalRewards) {
            IERC20(rewardToken).safeTransferFrom(_msgSender(), address(this), totalRewards - rewardBalance);
        }
        emit Initialized();
    }

    /// @notice Enable depositing
    function enableDepositing() external onlyOwner onlyIfInitialized {
        isDepositingEnabled = true;
        emit DepositingEnabled();
    }

    /// @notice Disable depositing
    function disableDepositing() external onlyOwner onlyIfInitialized {
        isDepositingEnabled = false;
        emit DepositingDisabled();
    }

    /// @notice Set minimum deposit
    /// @param _minimumDeposit Minimum deposit amount
    function setMinimumDeposit(uint _minimumDeposit) external onlyOwner {
        minimumDeposit = _minimumDeposit;
        emit MinimumDepositUpdated(_minimumDeposit);
    }

    /// @notice Stake tokens for a given lock up period
    /// @param _amount Amount to stake
    /// @param _lockUpPeriodType Lock up period (0 = 30 days, 1 = 90 days, 2 = 180 days, 3 = 365 days)
    function deposit(uint _amount, uint _lockUpPeriodType) external nonReentrant onlyIfInitialized onlyValidLockPeriod(_lockUpPeriodType) {
        require(isDepositingEnabled, "StablzStaking: Depositing is not allowed at this time");
        require(_amount >= minimumDeposit && _amount > 0, "StablzStaking: Amount is not valid");
        uint forecastRewards = _calculateReward(_amount, _lockUpPeriodType);
        require(forecastRewards <= totalAvailable, "StablzStaking: Forecast rewards exceeds available rewards");
        totalAvailable -= forecastRewards;
        uint stakeId = _userStakes[_msgSender()].length;
        _userStakes[_msgSender()].push(
            Stake(
                _lockUpPeriodType,
                block.timestamp,
                _amount,
                0,
                forecastRewards,
                0
            )
        );
        IERC20(stakingToken).safeTransferFrom(_msgSender(), address(this), _amount);
        _giveReceipt(_msgSender(), _amount);
        emit Deposit(_msgSender(), stakeId, _amount, _lockUpPeriodType);
    }

    /// @notice Withdraws specific stake only after the lock up period and claims any unclaimed rewards
    /// @param _stakeId Stake ID
    /// @param _amount Amount of tokens to withdraw
    function withdraw(uint _stakeId, uint _amount) external nonReentrant onlyValidStakeId(_msgSender(), _stakeId) {
        Stake storage stake = _userStakes[_msgSender()][_stakeId];
        uint period = getLockUpPeriod(stake.lockUpPeriodType);
        require(block.timestamp >= stake.stakedAt + period, "StablzStaking: You cannot unstake before the lock up period");
        require(_amount > 0, "StablzStaking: You cannot withdraw zero tokens");
        require(stake.amountWithdrawn < stake.amount, "StablzStaking: Already withdrawn full amount");
        require(_amount <= stake.amount - stake.amountWithdrawn, "StablzStaking: Insufficient stake balance");

        stake.amountWithdrawn += _amount;

        if (stake.claimedRewards < stake.allocatedRewards) {
            uint unclaimedRewards = stake.allocatedRewards - stake.claimedRewards;
            stake.claimedRewards = stake.allocatedRewards;
            IERC20(rewardToken).safeTransfer(_msgSender(), unclaimedRewards);
            emit RewardsClaimed(_msgSender(), _stakeId, unclaimedRewards);
        }
        _takeReceipt(_msgSender(), _amount);
        IERC20(stakingToken).safeTransfer(_msgSender(), _amount);
        emit Withdraw(_msgSender(), _stakeId, _amount);
    }

    /// @notice Claim rewards for a given stake, can be called before or after lockup period ends as long as there are unclaimed rewards
    /// @param _stakeId Stake ID
    function claimRewards(uint _stakeId) external nonReentrant onlyValidStakeId(_msgSender(), _stakeId) {
        Stake storage stake = _userStakes[_msgSender()][_stakeId];
        require(stake.claimedRewards < stake.allocatedRewards, "StablzStaking: You have already claimed your rewards");
        uint period = getLockUpPeriod(stake.lockUpPeriodType);
        uint rewards;
        if (block.timestamp >= stake.stakedAt + period) {
            rewards = stake.allocatedRewards - stake.claimedRewards;
        } else {
            uint timeDifference = block.timestamp - stake.stakedAt;
            uint rewardsToDate = stake.allocatedRewards * timeDifference / period;
            rewards = rewardsToDate - stake.claimedRewards;
        }
        stake.claimedRewards += rewards;
        IERC20(rewardToken).safeTransfer(_msgSender(), rewards);
        emit RewardsClaimed(_msgSender(), _stakeId, rewards);
    }

    /// @notice Get a list of a given user's stakes between two indexes
    /// @param _user User address
    /// @param _startIndex Start index
    /// @param _endIndex End index
    /// @return list Page of user stakes
    function getUserStakes(address _user, uint _startIndex, uint _endIndex) external view returns (Stake[] memory list) {
        uint totalUserStakes = getTotalUserStakes(_user);

        require(_startIndex <= _endIndex, "StablzStaking: Start index must be less than or equal to end index");
        require(_startIndex < totalUserStakes, "StablzStaking: Invalid start index");
        require(_endIndex < totalUserStakes, "StablzStaking: Invalid end index");

        list = new Stake[](_endIndex - _startIndex + 1);
        uint listIndex;
        for (uint stakeId = _startIndex; stakeId <= _endIndex; stakeId++) {
            list[listIndex] = _userStakes[_user][stakeId];
            listIndex++;
        }
        return list;
    }

    /// @notice Get total number of user stakes
    /// @param _user User address
    /// @return uint Total number of user stakes
    function getTotalUserStakes(address _user) public view returns (uint) {
        return _userStakes[_user].length;
    }

    /// @notice Calculate the rewards earned at the end of the lockup period for a given amount
    /// @param _amount Amount to stake
    /// @param _lockUpPeriodType Lock up period (0-3)
    /// @return reward Calculated reward
    function calculateReward(uint _amount, uint _lockUpPeriodType) external view onlyValidLockPeriod(_lockUpPeriodType) returns (uint reward) {
        return _calculateReward(_amount, _lockUpPeriodType);
    }

    /// @notice Get APR for a given lock up period
    /// @param _lockUpPeriodType Lock up period (0-3)
    /// @return apr APR to 1 d.p.
    function getAPR(uint _lockUpPeriodType) public view onlyValidLockPeriod(_lockUpPeriodType) returns (uint apr) {
        if (_lockUpPeriodType == 0) {
            apr = apr1Month;
        } else if (_lockUpPeriodType == 1) {
            apr = apr3Month;
        } else if (_lockUpPeriodType == 2) {
            apr = apr6Month;
        } else {
            apr = apr12Month;
        }
    }

    /// @notice Get the length of a lock up period in seconds
    /// @param _lockUpPeriodType Lock up period (0-3)
    /// @return time Lock up period in seconds
    function getLockUpPeriod(uint _lockUpPeriodType) public pure onlyValidLockPeriod(_lockUpPeriodType) returns (uint time) {
        if (_lockUpPeriodType == 0) {
            time = 30 days;
        } else if (_lockUpPeriodType == 1) {
            time = 90 days;
        } else if (_lockUpPeriodType == 2) {
            time = 180 days;
        } else {
            time = 365 days;
        }
    }

    function _giveReceipt(address _user, uint _amount) internal virtual;

    function _takeReceipt(address _user, uint _amount) internal virtual;

    function _calculateReward(uint _amount, uint _lockPeriodType) internal virtual view returns (uint reward);
}

// File: @uniswap/v2-core/contracts/interfaces/IUniswapV2Pair.sol



pragma solidity >=0.5.0;

interface IUniswapV2Pair {
    event Approval(address indexed owner, address indexed spender, uint value);
    event Transfer(address indexed from, address indexed to, uint value);

    function name() external pure returns (string memory);
    function symbol() external pure returns (string memory);
    function decimals() external pure returns (uint8);
    function totalSupply() external view returns (uint);
    function balanceOf(address owner) external view returns (uint);
    function allowance(address owner, address spender) external view returns (uint);

    function approve(address spender, uint value) external returns (bool);
    function transfer(address to, uint value) external returns (bool);
    function transferFrom(address from, address to, uint value) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);
    function PERMIT_TYPEHASH() external pure returns (bytes32);
    function nonces(address owner) external view returns (uint);

    function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

    event Mint(address indexed sender, uint amount0, uint amount1);
    event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
    event Swap(
        address indexed sender,
        uint amount0In,
        uint amount1In,
        uint amount0Out,
        uint amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint);
    function factory() external view returns (address);
    function token0() external view returns (address);
    function token1() external view returns (address);
    function getReserves() external view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestampLast);
    function price0CumulativeLast() external view returns (uint);
    function price1CumulativeLast() external view returns (uint);
    function kLast() external view returns (uint);

    function mint(address to) external returns (uint liquidity);
    function burn(address to) external returns (uint amount0, uint amount1);
    function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data) external;
    function skim(address to) external;
    function sync() external;

    function initialize(address, address) external;
}

// File: @openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.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 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'
        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) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @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
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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 `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, 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 `from` to `to` 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 from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^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() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

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

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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 {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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");

        (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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/extensions/draft-IERC20Permit.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^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 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) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}