// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/Address.sol)

pragma solidity ^0.8.20;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev The ETH balance of the account is not enough to perform the operation.
     */
    error AddressInsufficientBalance(address account);

    /**
     * @dev There's no code at `target` (it is not a contract).
     */
    error AddressEmptyCode(address target);

    /**
     * @dev A call to an address target failed. The target may have reverted.
     */
    error FailedInnerCall();

    /**
     * @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://consensys.net/diligence/blog/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/v0.8.20/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        if (address(this).balance < amount) {
            revert AddressInsufficientBalance(address(this));
        }

        (bool success, ) = recipient.call{value: amount}("");
        if (!success) {
            revert FailedInnerCall();
        }
    }

    /**
     * @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 or custom error, it is bubbled
     * up by this function (like regular Solidity function calls). However, if
     * the call reverted with no returned reason, this function reverts with a
     * {FailedInnerCall} error.
     *
     * 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.
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0);
    }

    /**
     * @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`.
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        if (address(this).balance < value) {
            revert AddressInsufficientBalance(address(this));
        }
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and reverts if the target
     * was not a contract or bubbling up the revert reason (falling back to {FailedInnerCall}) in case of an
     * unsuccessful call.
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata
    ) internal view returns (bytes memory) {
        if (!success) {
            _revert(returndata);
        } else {
            // only check if target is a contract if the call was successful and the return data is empty
            // otherwise we already know that it was a contract
            if (returndata.length == 0 && target.code.length == 0) {
                revert AddressEmptyCode(target);
            }
            return returndata;
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and reverts if it wasn't, either by bubbling the
     * revert reason or with a default {FailedInnerCall} error.
     */
    function verifyCallResult(bool success, bytes memory returndata) internal pure returns (bytes memory) {
        if (!success) {
            _revert(returndata);
        } else {
            return returndata;
        }
    }

    /**
     * @dev Reverts with returndata if present. Otherwise reverts with {FailedInnerCall}.
     */
    function _revert(bytes memory returndata) 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 FailedInnerCall();
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)

pragma solidity ^0.8.20;

/**
 * @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;
    }

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.20;

/**
 * @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 value of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the value of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves a `value` amount of 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 value) 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 a `value` amount of tokens 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 value) external returns (bool);

    /**
     * @dev Moves a `value` amount of tokens from `from` to `to` using the
     * allowance mechanism. `value` 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 value) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity ^0.8.20;

/**
 * @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.
 *
 * ==== Security Considerations
 *
 * There are two important considerations concerning the use of `permit`. The first is that a valid permit signature
 * expresses an allowance, and it should not be assumed to convey additional meaning. In particular, it should not be
 * considered as an intention to spend the allowance in any specific way. The second is that because permits have
 * built-in replay protection and can be submitted by anyone, they can be frontrun. A protocol that uses permits should
 * take this into consideration and allow a `permit` call to fail. Combining these two aspects, a pattern that may be
 * generally recommended is:
 *
 * ```solidity
 * function doThingWithPermit(..., uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s) public {
 *     try token.permit(msg.sender, address(this), value, deadline, v, r, s) {} catch {}
 *     doThing(..., value);
 * }
 *
 * function doThing(..., uint256 value) public {
 *     token.safeTransferFrom(msg.sender, address(this), value);
 *     ...
 * }
 * ```
 *
 * Observe that: 1) `msg.sender` is used as the owner, leaving no ambiguity as to the signer intent, and 2) the use of
 * `try/catch` allows the permit to fail and makes the code tolerant to frontrunning. (See also
 * {SafeERC20-safeTransferFrom}).
 *
 * Additionally, note that smart contract wallets (such as Argent or Safe) are not able to produce permit signatures, so
 * contracts should have entry points that don't rely on permit.
 */
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].
     *
     * CAUTION: See Security Considerations above.
     */
    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);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.21;

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

contract LendsStake is Ownable, ReentrancyGuard {
    using SafeERC20 for IERC20;

    event Stake(address indexed wallet, uint256 amount, uint256 date);
    event Withdraw(address indexed wallet, uint256 amount, uint256 date);
    event Claimed(
        address indexed wallet,
        address indexed rewardToken,
        uint256 amount
    );

    event RewardTokenChanged(
        address indexed oldRewardToken,
        uint256 returnedAmount,
        address indexed newRewardToken
    );
    event GovernanceTokenChanged(
        address indexed oldGovernanceToken,
        address indexed newGovernanceToken
    );
    event LockTimePeriodChanged(uint48 lockTimePeriod);
    event StakeRewardFactorChanged(uint256 stakeRewardFactor);
    event StakeRewardEndTimeChanged(uint48 stakeRewardEndTime);
    event RewardsBurned(address indexed staker, uint256 amount);
    event ERC20TokensRemoved(
        address indexed tokenAddress,
        address indexed receiver,
        uint256 amount
    );

    uint48 public constant MAX_TIME = type(uint48).max; // = 2^48 - 1

    struct User {
        uint48 stakeTime;
        uint48 unlockTime;
        uint160 stakeAmount;
        uint256 accumulatedRewards;
    }

    mapping(address => User) public userMap;

    uint256 public tokenTotalStaked; // sum of all staked tokens

    address public immutable stakingToken; // address of token which can be staked into this contract
    address public governanceToken; // address of governance token
    address public rewardToken; // address of reward token

    /**
     * Using block.timestamp instead of block.number for reward calculation
     * 1) Easier to handle for users
     * 2) Should result in same rewards across different chain with different block times
     * 3) "The current block timestamp must be strictly larger than the timestamp of the last block, ...
     *     but the only guarantee is that it will be somewhere between the timestamps ...
     *     of two consecutive blocks in the canonical chain."
     *    https://docs.soliditylang.org/en/v0.7.6/cheatsheet.html?highlight=block.timestamp#global-variables
     */

    uint48 public lockTimePeriod; // time in seconds a user has to wait after calling unlock until staked token can be withdrawn
    uint48 public stakeRewardEndTime; // unix time in seconds when the reward scheme will end
    uint256 public stakeRewardFactor; // time in seconds * amount of staked token to receive 1 reward token

    constructor(
        address _stakingToken,
        address _governanceToken,
        address _rewardToken,
        uint48 _lockTimePeriod
    ) Ownable(msg.sender) {
        require(_stakingToken != address(0), "stakingToken.address == 0");
        require(_governanceToken != address(0), "governanceToken.address == 0");
        require(_rewardToken != address(0), "rewardToken.address == 0");

        require(_lockTimePeriod < 366 days, "lockTimePeriod >= 366 days");

        stakingToken = _stakingToken;
        governanceToken = _governanceToken;
        rewardToken = _rewardToken;

        lockTimePeriod = _lockTimePeriod;
        // set some defaults
        stakeRewardFactor = 2439 * 1 days; // default : a user has to stake 2439 token for 1 day to receive 1 reward token i.e. 15% APY
        stakeRewardEndTime = uint48(block.timestamp + 366 days); // default : reward scheme ends in 1 year
    }

    /**
     * based on OpenZeppelin SafeCast v4.3
     * https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.3/contracts/utils/math/SafeCast.sol
     */

    function toUint48(uint256 value) internal pure returns (uint48) {
        require(value <= type(uint48).max, "value doesn't fit in 48 bits");
        return uint48(value);
    }

    function toUint160(uint256 value) internal pure returns (uint160) {
        require(value <= type(uint160).max, "value doesn't fit in 160 bits");
        return uint160(value);
    }

    /**
     * External API functions
     */

    function stakeTime(
        address _staker
    ) external view returns (uint48 dateTime) {
        return userMap[_staker].stakeTime;
    }

    function stakeAmount(
        address _staker
    ) external view returns (uint256 balance) {
        return userMap[_staker].stakeAmount;
    }

    // redundant with stakeAmount() for compatibility
    function balanceOf(
        address _staker
    ) external view returns (uint256 balance) {
        return userMap[_staker].stakeAmount;
    }

    function userAccumulatedRewards(
        address _staker
    ) external view returns (uint256 rewards) {
        return userMap[_staker].accumulatedRewards;
    }

    /**
     * @dev return unix epoch time when staked tokens will be unlocked
     * @dev return MAX_INT_UINT48 = 2**48-1 if user has no token staked
     * @dev this always allows an easy check with : require(block.timestamp > getUnlockTime(account));
     * @return unlockTime unix epoch time in seconds
     */
    function getUnlockTime(
        address _staker
    ) public view returns (uint48 unlockTime) {
        return
            userMap[_staker].stakeAmount > 0
                ? userMap[_staker].unlockTime
                : MAX_TIME;
    }

    /**
     * @return balance of reward tokens held by this contract
     */
    function getRewardTokenBalance() public view returns (uint256 balance) {
        if (rewardToken == address(0)) return 0;
        balance = IERC20(rewardToken).balanceOf(address(this));
        if (stakingToken == rewardToken) {
            balance -= tokenTotalStaked;
        }
    }

    // onlyOwner --------------------------------------------------

    /**
     * @notice setting rewardToken to address(0) disables claim/mint
     * @notice if there was a reward token set before, return remaining tokens to msg.sender/admin
     * @param newRewardToken address
     */
    function setRewardToken(
        address newRewardToken
    ) external nonReentrant onlyOwner {
        address oldRewardToken = rewardToken;
        uint256 rewardBalance = getRewardTokenBalance(); // balance of oldRewardToken
        if (rewardBalance > 0) {
            IERC20(oldRewardToken).safeTransfer(msg.sender, rewardBalance);
        }
        rewardToken = newRewardToken;
        emit RewardTokenChanged(oldRewardToken, rewardBalance, newRewardToken);
    }

    /**
     * @notice setting governanceToken to address(0) disables staking/unstaking
     * @param newGovernanceToken address
     */
    function setGovernanceToken(
        address newGovernanceToken
    ) external nonReentrant onlyOwner {
        address oldGovernanceToken = governanceToken;
        governanceToken = newGovernanceToken;
        emit GovernanceTokenChanged(oldGovernanceToken, governanceToken);
    }

    /**
     * @notice set time a user has to wait after calling unlock until staked token can be withdrawn
     * @param _lockTimePeriod time in seconds
     */
    function setLockTimePeriod(uint48 _lockTimePeriod) external onlyOwner {
        lockTimePeriod = _lockTimePeriod;
        emit LockTimePeriodChanged(_lockTimePeriod);
    }

    /**
     * @notice see calculateUserClaimableReward() docs
     * @dev requires that reward token has the same decimals as stake token
     * @param _stakeRewardFactor time in seconds * amount of staked token to receive 1 reward token
     */
    function setStakeRewardFactor(
        uint256 _stakeRewardFactor
    ) external onlyOwner {
        stakeRewardFactor = _stakeRewardFactor;
        emit StakeRewardFactorChanged(_stakeRewardFactor);
    }

    /**
     * @notice set block time when stake reward scheme will end
     * @param _stakeRewardEndTime unix time in seconds
     */
    function setStakeRewardEndTime(
        uint48 _stakeRewardEndTime
    ) external onlyOwner {
        require(
            stakeRewardEndTime > block.timestamp,
            "time has to be in the future"
        );
        stakeRewardEndTime = _stakeRewardEndTime;
        emit StakeRewardEndTimeChanged(_stakeRewardEndTime);
    }

    /**
     * ADMIN_ROLE has to set BURNER_ROLE
     * allows an external (lottery token sale) contract to substract rewards
     */
    function burnRewards(address _staker, uint256 _amount) external onlyOwner {
        User storage user = _updateRewards(_staker);

        if (_amount < user.accumulatedRewards) {
            user.accumulatedRewards -= _amount; // safe
        } else {
            user.accumulatedRewards = 0; // burn at least all what's there
        }
        emit RewardsBurned(_staker, _amount);
    }

    /** msg.sender external view convenience functions *********************************/

    function stakeAmount_msgSender() public view returns (uint256) {
        return userMap[msg.sender].stakeAmount;
    }

    function stakeTime_msgSender() external view returns (uint48) {
        return userMap[msg.sender].stakeTime;
    }

    function getUnlockTime_msgSender()
        external
        view
        returns (uint48 unlockTime)
    {
        return getUnlockTime(msg.sender);
    }

    function userClaimableRewards_msgSender() external view returns (uint256) {
        return userClaimableRewards(msg.sender);
    }

    function userAccumulatedRewards_msgSender()
        external
        view
        returns (uint256)
    {
        return userMap[msg.sender].accumulatedRewards;
    }

    function userTotalRewards_msgSender() external view returns (uint256) {
        return userTotalRewards(msg.sender);
    }

    function getEarnedRewardTokens_msgSender() external view returns (uint256) {
        return getEarnedRewardTokens(msg.sender);
    }

    /** public external view functions (also used internally) **************************/

    /**
     * calculates unclaimed rewards
     * unclaimed rewards = expired time since last stake/unstake transaction * current staked amount
     *
     * We have to cover 6 cases here :
     * 1) block time < stake time < end time   : should never happen => error
     * 2) block time < end time   < stake time : should never happen => error
     * 3) end time   < block time < stake time : should never happen => error
     * 4) end time   < stake time < block time : staked after reward period is over => no rewards
     * 5) stake time < block time < end time   : end time in the future
     * 6) stake time < end time   < block time : end time in the past & staked before
     * @param _staker address
     * @return claimableRewards = timePeriod * stakeAmount
     */
    function userClaimableRewards(
        address _staker
    ) public view returns (uint256) {
        User storage user = userMap[_staker];
        // case 1) 2) 3)
        // stake time in the future - should never happen - actually an (internal ?) error
        if (block.timestamp <= user.stakeTime) return 0;

        // case 4)
        // staked after reward period is over => no rewards
        // end time < stake time < block time
        if (stakeRewardEndTime <= user.stakeTime) return 0;

        uint256 timePeriod;

        // case 5
        // we have not reached the end of the reward period
        // stake time < block time < end time
        if (block.timestamp <= stakeRewardEndTime) {
            timePeriod = block.timestamp - user.stakeTime; // covered by case 1) 2) 3) 'if'
        } else {
            // case 6
            // user staked before end of reward period , but that is in the past now
            // stake time < end time < block time
            timePeriod = stakeRewardEndTime - user.stakeTime; // covered case 4)
        }

        return timePeriod * user.stakeAmount;
    }

    function userTotalRewards(address _staker) public view returns (uint256) {
        return
            userClaimableRewards(_staker) + userMap[_staker].accumulatedRewards;
    }

    function getEarnedRewardTokens(
        address _staker
    ) public view returns (uint256 claimableRewardTokens) {
        if (address(rewardToken) == address(0) || stakeRewardFactor == 0) {
            return 0;
        } else {
            return userTotalRewards(_staker) / stakeRewardFactor; // safe
        }
    }

    /**
     *  @dev whenver the staked balance changes do ...
     *
     *  @dev calculate userClaimableRewards = previous staked amount * (current time - last stake time)
     *  @dev add userClaimableRewards to userAccumulatedRewards
     *  @dev reset userClaimableRewards to 0 by setting stakeTime to current time
     *  @dev not used as doing it inline, local, within a function consumes less gas
     *
     *  @return user reference pointer for further processing
     */
    function _updateRewards(
        address _staker
    ) internal returns (User storage user) {
        // calculate reward credits using previous staking amount and previous time period
        // add new reward credits to already accumulated reward credits
        user = userMap[_staker];
        user.accumulatedRewards += userClaimableRewards(_staker);

        // update stake Time to current time (start new reward period)
        // will also reset userClaimableRewards()
        user.stakeTime = toUint48(block.timestamp);
    }

    /**
     * add stake token to staking pool
     * @dev requires the token to be approved for transfer
     * @dev we assume that (our) stake token is not malicious, so no special checks
     * @param _amount of token to be staked
     */
    function _stake(uint256 _amount) internal returns (uint256) {
        require(_amount > 0, "stake amount must be > 0");
        require(
            IERC20(governanceToken).balanceOf(address(this)) >= _amount,
            "staking limit has been reached"
        );

        User storage user = _updateRewards(msg.sender); // update rewards and return reference to user

        user.stakeAmount = toUint160(user.stakeAmount + _amount);
        tokenTotalStaked += _amount;

        user.unlockTime = toUint48(block.timestamp + lockTimePeriod);

        // using SafeERC20 for IERC20 => will revert in case of error
        IERC20(stakingToken).safeTransferFrom(
            msg.sender,
            address(this),
            _amount
        );
        IERC20(governanceToken).safeTransfer(msg.sender, _amount);

        emit Stake(msg.sender, _amount, toUint48(block.timestamp)); // = user.stakeTime
        return _amount;
    }

    /**
     * withdraw staked token, ...
     * do not withdraw rewards token (it might not be worth the gas)
     * @return amount of tokens sent to user's account
     */
    function _withdraw(uint256 amount) internal returns (uint256) {
        require(amount > 0, "amount to withdraw not > 0");
        require(
            block.timestamp > getUnlockTime(msg.sender),
            "staked tokens are still locked"
        );
        require(
            IERC20(governanceToken).balanceOf(msg.sender) >= amount,
            "not enough staked tokens"
        );

        User storage user = _updateRewards(msg.sender); // update rewards and return reference to user

        require(amount <= user.stakeAmount, "withdraw amount > staked amount");
        user.stakeAmount -= toUint160(amount);
        tokenTotalStaked -= amount;

        // using SafeERC20 for IERC20 => will revert in case of error
        IERC20(stakingToken).safeTransfer(msg.sender, amount);
        IERC20(governanceToken).safeTransferFrom(
            msg.sender,
            address(this),
            amount
        );

        emit Withdraw(msg.sender, amount, toUint48(block.timestamp)); // = user.stakeTime
        return amount;
    }

    /**
     * claim reward tokens for accumulated reward credits
     * ... but do not unstake staked token
     */
    function _claim() internal returns (uint256) {
        require(rewardToken != address(0), "no reward token contract");
        uint256 earnedRewardTokens = getEarnedRewardTokens(msg.sender);
        require(earnedRewardTokens > 0, "no tokens to claim");

        // like _updateRewards() , but reset all rewards to 0
        User storage user = userMap[msg.sender];
        user.accumulatedRewards = 0;
        user.stakeTime = toUint48(block.timestamp); // will reset userClaimableRewards to 0
        // user.stakeAmount = unchanged

        require(
            earnedRewardTokens <= getRewardTokenBalance(),
            "not enough reward tokens"
        ); // redundant but dedicated error message
        IERC20(rewardToken).safeTransfer(msg.sender, earnedRewardTokens);

        emit Claimed(msg.sender, rewardToken, earnedRewardTokens);
        return earnedRewardTokens;
    }

    function stake(uint256 _amount) external nonReentrant returns (uint256) {
        return _stake(_amount);
    }

    function claim() external nonReentrant returns (uint256) {
        return _claim();
    }

    function withdraw(uint256 amount) external nonReentrant returns (uint256) {
        return _withdraw(amount);
    }

    function withdrawAll() external nonReentrant returns (uint256) {
        return _withdraw(stakeAmount_msgSender());
    }

    /**
     * Do not accept accidently sent ETH :
     * If neither a receive Ether nor a payable fallback function is present,
     * the contract cannot receive Ether through regular transactions and throws an exception.
     * https://docs.soliditylang.org/en/v0.8.7/contracts.html#receive-ether-function
     */

    /**
     * @notice withdraw accidently sent ERC20 tokens
     * @param _tokenAddress address of token to withdraw
     */
    function removeOtherERC20Tokens(address _tokenAddress) external onlyOwner {
        uint256 balance = IERC20(_tokenAddress).balanceOf(address(this));
        IERC20(_tokenAddress).safeTransfer(msg.sender, balance);
        emit ERC20TokensRemoved(_tokenAddress, msg.sender, balance);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity ^0.8.20;

import {Context} from "../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.
 *
 * The initial owner is set to the address provided by the deployer. 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;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

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

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @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 {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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 {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _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);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (utils/ReentrancyGuard.sol)

pragma solidity ^0.8.20;

/**
 * @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;

    /**
     * @dev Unauthorized reentrant call.
     */
    error ReentrancyGuardReentrantCall();

    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
        if (_status == ENTERED) {
            revert ReentrancyGuardReentrantCall();
        }

        // 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;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.20;

import {IERC20} from "../IERC20.sol";
import {IERC20Permit} from "../extensions/IERC20Permit.sol";
import {Address} from "../../../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;

    /**
     * @dev An operation with an ERC20 token failed.
     */
    error SafeERC20FailedOperation(address token);

    /**
     * @dev Indicates a failed `decreaseAllowance` request.
     */
    error SafeERC20FailedDecreaseAllowance(address spender, uint256 currentAllowance, uint256 requestedDecrease);

    /**
     * @dev Transfer `value` amount of `token` from the calling contract to `to`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeCall(token.transfer, (to, value)));
    }

    /**
     * @dev Transfer `value` amount of `token` from `from` to `to`, spending the approval given by `from` to the
     * calling contract. If `token` returns no value, non-reverting calls are assumed to be successful.
     */
    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeCall(token.transferFrom, (from, to, value)));
    }

    /**
     * @dev Increase the calling contract's allowance toward `spender` by `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful.
     */
    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 oldAllowance = token.allowance(address(this), spender);
        forceApprove(token, spender, oldAllowance + value);
    }

    /**
     * @dev Decrease the calling contract's allowance toward `spender` by `requestedDecrease`. If `token` returns no
     * value, non-reverting calls are assumed to be successful.
     */
    function safeDecreaseAllowance(IERC20 token, address spender, uint256 requestedDecrease) internal {
        unchecked {
            uint256 currentAllowance = token.allowance(address(this), spender);
            if (currentAllowance < requestedDecrease) {
                revert SafeERC20FailedDecreaseAllowance(spender, currentAllowance, requestedDecrease);
            }
            forceApprove(token, spender, currentAllowance - requestedDecrease);
        }
    }

    /**
     * @dev Set the calling contract's allowance toward `spender` to `value`. If `token` returns no value,
     * non-reverting calls are assumed to be successful. Meant to be used with tokens that require the approval
     * to be set to zero before setting it to a non-zero value, such as USDT.
     */
    function forceApprove(IERC20 token, address spender, uint256 value) internal {
        bytes memory approvalCall = abi.encodeCall(token.approve, (spender, value));

        if (!_callOptionalReturnBool(token, approvalCall)) {
            _callOptionalReturn(token, abi.encodeCall(token.approve, (spender, 0)));
            _callOptionalReturn(token, approvalCall);
        }
    }

    /**
     * @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);
        if (returndata.length != 0 && !abi.decode(returndata, (bool))) {
            revert SafeERC20FailedOperation(address(token));
        }
    }

    /**
     * @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).
     *
     * This is a variant of {_callOptionalReturn} that silents catches all reverts and returns a bool instead.
     */
    function _callOptionalReturnBool(IERC20 token, bytes memory data) private returns (bool) {
        // 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 cannot use {Address-functionCall} here since this should return false
        // and not revert is the subcall reverts.

        (bool success, bytes memory returndata) = address(token).call(data);
        return success && (returndata.length == 0 || abi.decode(returndata, (bool))) && address(token).code.length > 0;
    }
}

{
  "compilationTarget": {
    "contracts/LendsStake.sol": "LendsStake"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}