// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (utils/Address.sol)

pragma solidity 0.8.18;

/**
 * @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/v0.8.0/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, 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.
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, defaultRevert);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with a
     * `customRevert` function as a fallback when `target` reverts.
     *
     * Requirements:
     *
     * - `customRevert` must be a reverting function.
     */
    function functionCall(address target, bytes memory data, function() internal view customRevert)
        internal
        returns (bytes memory)
    {
        return functionCallWithValue(target, data, 0, customRevert);
    }

    /**
     * @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) {
        return functionCallWithValue(target, data, value, defaultRevert);
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with a `customRevert` function as a fallback revert reason when `target` reverts.
     *
     * Requirements:
     *
     * - `customRevert` must be a reverting function.
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        function() internal view customRevert
    ) 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, customRevert);
    }

    /**
     * @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) {
        return functionStaticCall(target, data, defaultRevert);
    }

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

    /**
     * @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) {
        return functionDelegateCall(target, data, defaultRevert);
    }

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

    /**
     * @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 `customRevert`) in case of unsuccessful call or if target was not a contract.
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        function() internal view customRevert
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // 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 (target.code.length == 0) {
                    revert AddressEmptyCode(target);
                }
            }
            return returndata;
        } else {
            _revert(returndata, customRevert);
        }
    }

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

    /**
     * @dev Same as {xref-Address-verifyCallResult-bool-bytes-}[`verifyCallResult`], but with a
     * `customRevert` function as a fallback when `success` is `false`.
     *
     * Requirements:
     *
     * - `customRevert` must be a reverting function.
     */
    function verifyCallResult(bool success, bytes memory returndata, function() internal view customRevert)
        internal
        view
        returns (bytes memory)
    {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, customRevert);
        }
    }

    /**
     * @dev Default reverting function when no `customRevert` is provided in a function call.
     */
    function defaultRevert() internal pure {
        revert FailedInnerCall();
    }

    function _revert(bytes memory returndata, function() internal view customRevert) private view {
        // 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 {
            customRevert();
            revert FailedInnerCall();
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.18;

contract Governable {
    address public gov;

    constructor() {
        gov = msg.sender;
    }

    modifier onlyGov() {
        require(msg.sender == gov, "Governable: forbidden");
        _;
    }

    function setGov(address _gov) external onlyGov {
        require(_gov != address(0), "Governable: _gov is zero address");
        gov = _gov;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/IERC20.sol)

pragma solidity 0.8.18;

/**
 * @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 v4.9.0) (token/ERC20/extensions/IERC20Permit.sol)

pragma solidity 0.8.18;

/**
 * @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);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.18;

interface IRewardDistributor {
    function rewardToken() external view returns (address);
    function tokensPerInterval() external view returns (uint256);
    function pendingRewards() external view returns (uint256);
    function distribute() external returns (uint256);
    function setTokensPerInterval(uint256 _amount) external;
    function updateLastDistributionTime() external;
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.18;

interface IRewardTracker {
    function depositBalances(address _account, address _depositToken) external view returns (uint256);
    function stakedAmounts(address _account) external view returns (uint256);
    function updateRewards() external;
    function stake(address _depositToken, uint256 _amount) external;
    function stakeForAccount(address _fundingAccount, address _account, address _depositToken, uint256 _amount)
        external;
    function unstake(address _depositToken, uint256 _amount) external;
    function unstakeForAccount(address _account, address _depositToken, uint256 _amount, address _receiver) external;
    function tokensPerInterval() external view returns (uint256);
    function claim(address _receiver) external returns (uint256);
    function claimForAccount(address _account, address _receiver) external returns (uint256);
    function claimable(address _account) external view returns (uint256);
    function averageStakedAmounts(address _account) external view returns (uint256);
    function cumulativeRewards(address _account) external view returns (uint256);
    function setInPrivateTransferMode(bool _inPrivateTransferMode) external;
    function setInPrivateStakingMode(bool _inPrivateStakingMode) external;
    function setInPrivateClaimingMode(bool _inPrivateClaimingMode) external;
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)

pragma solidity 0.8.18;

/**
 * @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

pragma solidity 0.8.18;

import "../libraries/token/IERC20.sol";
import "../libraries/token/SafeERC20.sol";
import "../libraries/utils/ReentrancyGuard.sol";

import "./interfaces/IRewardDistributor.sol";
import "./interfaces/IRewardTracker.sol";
import "../access/Governable.sol";

contract RewardTracker is IERC20, ReentrancyGuard, IRewardTracker, Governable {
    using SafeERC20 for IERC20;

    uint256 public constant BASIS_POINTS_DIVISOR = 10000;
    uint256 public constant PRECISION = 1e30;

    uint8 public constant decimals = 18;

    bool public isInitialized;

    string public name;
    string public symbol;

    address public distributor;
    mapping(address => bool) public isDepositToken;
    mapping(address => mapping(address => uint256)) public override depositBalances;
    mapping(address => uint256) public totalDepositSupply;

    uint256 public override totalSupply;
    mapping(address => uint256) public balances;
    mapping(address => mapping(address => uint256)) public allowances;

    uint256 public cumulativeRewardPerToken;
    mapping(address => uint256) public override stakedAmounts;
    mapping(address => uint256) public claimableReward;
    mapping(address => uint256) public previousCumulatedRewardPerToken;
    mapping(address => uint256) public override cumulativeRewards;
    mapping(address => uint256) public override averageStakedAmounts;

    bool public inPrivateTransferMode;
    bool public inPrivateStakingMode;
    bool public inPrivateClaimingMode;
    mapping(address => bool) public isHandler;

    event Claim(address receiver, uint256 amount);

    constructor(string memory _name, string memory _symbol) {
        name = _name;
        symbol = _symbol;
    }

    function initialize(address[] memory _depositTokens, address _distributor) external onlyGov {
        require(!isInitialized, "RewardTracker: already initialized");
        isInitialized = true;

        for (uint256 i = 0; i < _depositTokens.length; i++) {
            address depositToken = _depositTokens[i];
            isDepositToken[depositToken] = true;
        }

        distributor = _distributor;
    }

    function setDepositToken(address _depositToken, bool _isDepositToken) external onlyGov {
        isDepositToken[_depositToken] = _isDepositToken;
    }

    function setInPrivateTransferMode(bool _inPrivateTransferMode) external onlyGov {
        inPrivateTransferMode = _inPrivateTransferMode;
    }

    function setInPrivateStakingMode(bool _inPrivateStakingMode) external onlyGov {
        inPrivateStakingMode = _inPrivateStakingMode;
    }

    function setInPrivateClaimingMode(bool _inPrivateClaimingMode) external onlyGov {
        inPrivateClaimingMode = _inPrivateClaimingMode;
    }

    function setHandler(address _handler, bool _isActive) external onlyGov {
        isHandler[_handler] = _isActive;
    }

    // to help users who accidentally send their tokens to this contract
    function withdrawToken(address _token, address _account, uint256 _amount) external onlyGov {
        IERC20(_token).safeTransfer(_account, _amount);
    }

    function balanceOf(address _account) external view override returns (uint256) {
        return balances[_account];
    }

    function stake(address _depositToken, uint256 _amount) external override nonReentrant {
        if (inPrivateStakingMode) revert("RewardTracker: action not enabled");
        _stake(msg.sender, msg.sender, _depositToken, _amount);
    }

    function stakeForAccount(address _fundingAccount, address _account, address _depositToken, uint256 _amount)
        external
        override
        nonReentrant
    {
        _validateHandler();
        _stake(_fundingAccount, _account, _depositToken, _amount);
    }

    function unstake(address _depositToken, uint256 _amount) external override nonReentrant {
        if (inPrivateStakingMode) revert("RewardTracker: action not enabled");
        _unstake(msg.sender, _depositToken, _amount, msg.sender);
    }

    function unstakeForAccount(address _account, address _depositToken, uint256 _amount, address _receiver)
        external
        override
        nonReentrant
    {
        _validateHandler();
        _unstake(_account, _depositToken, _amount, _receiver);
    }

    function transfer(address _recipient, uint256 _amount) external override returns (bool) {
        _transfer(msg.sender, _recipient, _amount);
        return true;
    }

    function allowance(address _owner, address _spender) external view override returns (uint256) {
        return allowances[_owner][_spender];
    }

    function approve(address _spender, uint256 _amount) external override returns (bool) {
        _approve(msg.sender, _spender, _amount);
        return true;
    }

    function transferFrom(address _sender, address _recipient, uint256 _amount) external override returns (bool) {
        if (isHandler[msg.sender]) {
            _transfer(_sender, _recipient, _amount);
            return true;
        }

        uint256 nextAllowance = allowances[_sender][msg.sender] - _amount;
        _approve(_sender, msg.sender, nextAllowance);
        _transfer(_sender, _recipient, _amount);
        return true;
    }

    function tokensPerInterval() external view override returns (uint256) {
        return IRewardDistributor(distributor).tokensPerInterval();
    }

    function updateRewards() external override nonReentrant {
        _updateRewards(address(0));
    }

    function claim(address _receiver) external override nonReentrant returns (uint256) {
        if (inPrivateClaimingMode) revert("RewardTracker: action not enabled");
        return _claim(msg.sender, _receiver);
    }

    function claimForAccount(address _account, address _receiver) external override nonReentrant returns (uint256) {
        _validateHandler();
        return _claim(_account, _receiver);
    }

    function claimable(address _account) public view override returns (uint256) {
        uint256 stakedAmount = stakedAmounts[_account];
        if (stakedAmount == 0) {
            return claimableReward[_account];
        }
        uint256 supply = totalSupply;
        uint256 pendingRewards = IRewardDistributor(distributor).pendingRewards() * PRECISION;
        uint256 nextCumulativeRewardPerToken = cumulativeRewardPerToken + (pendingRewards / supply);
        return claimableReward[_account]
            + (stakedAmount * (nextCumulativeRewardPerToken - previousCumulatedRewardPerToken[_account])) / PRECISION;
    }

    function rewardToken() public view returns (address) {
        return IRewardDistributor(distributor).rewardToken();
    }

    function _claim(address _account, address _receiver) private returns (uint256) {
        _updateRewards(_account);

        uint256 tokenAmount = claimableReward[_account];
        claimableReward[_account] = 0;

        if (tokenAmount > 0) {
            IERC20(rewardToken()).safeTransfer(_receiver, tokenAmount);
            emit Claim(_account, tokenAmount);
        }

        return tokenAmount;
    }

    function _mint(address _account, uint256 _amount) internal {
        require(_account != address(0), "RewardTracker: mint to the zero address");

        totalSupply = totalSupply + _amount;
        balances[_account] = balances[_account] + _amount;

        emit Transfer(address(0), _account, _amount);
    }

    function _burn(address _account, uint256 _amount) internal {
        require(_account != address(0), "RewardTracker: burn from the zero address");

        balances[_account] = balances[_account] - _amount;
        totalSupply = totalSupply - _amount;

        emit Transfer(_account, address(0), _amount);
    }

    function _transfer(address _sender, address _recipient, uint256 _amount) private {
        require(_sender != address(0), "RewardTracker: transfer from the zero address");
        require(_recipient != address(0), "RewardTracker: transfer to the zero address");

        if (inPrivateTransferMode) _validateHandler();

        balances[_sender] = balances[_sender] - _amount;
        balances[_recipient] = balances[_recipient] + _amount;

        emit Transfer(_sender, _recipient, _amount);
    }

    function _approve(address _owner, address _spender, uint256 _amount) private {
        require(_owner != address(0), "RewardTracker: approve from the zero address");
        require(_spender != address(0), "RewardTracker: approve to the zero address");

        allowances[_owner][_spender] = _amount;

        emit Approval(_owner, _spender, _amount);
    }

    function _validateHandler() private view {
        require(isHandler[msg.sender], "RewardTracker: forbidden");
    }

    function _stake(address _fundingAccount, address _account, address _depositToken, uint256 _amount) private {
        require(_amount > 0, "RewardTracker: invalid _amount");
        require(isDepositToken[_depositToken], "RewardTracker: invalid _depositToken");

        IERC20(_depositToken).safeTransferFrom(_fundingAccount, address(this), _amount);

        _updateRewards(_account);

        stakedAmounts[_account] = stakedAmounts[_account] + _amount;
        depositBalances[_account][_depositToken] = depositBalances[_account][_depositToken] + _amount;
        totalDepositSupply[_depositToken] = totalDepositSupply[_depositToken] + _amount;

        _mint(_account, _amount);
    }

    function _unstake(address _account, address _depositToken, uint256 _amount, address _receiver) private {
        require(_amount > 0, "RewardTracker: invalid _amount");
        require(isDepositToken[_depositToken], "RewardTracker: invalid _depositToken");

        _updateRewards(_account);

        uint256 stakedAmount = stakedAmounts[_account];
        require(stakedAmounts[_account] >= _amount, "RewardTracker: _amount exceeds stakedAmount");

        stakedAmounts[_account] = stakedAmount - _amount;

        uint256 depositBalance = depositBalances[_account][_depositToken];
        require(depositBalance >= _amount, "RewardTracker: _amount exceeds depositBalance");
        depositBalances[_account][_depositToken] = depositBalance - _amount;
        totalDepositSupply[_depositToken] = totalDepositSupply[_depositToken] - _amount;

        _burn(_account, _amount);
        IERC20(_depositToken).safeTransfer(_receiver, _amount);
    }

    function _updateRewards(address _account) private {
        uint256 blockReward = IRewardDistributor(distributor).distribute();

        uint256 supply = totalSupply;
        uint256 _cumulativeRewardPerToken = cumulativeRewardPerToken;
        if (supply > 0 && blockReward > 0) {
            _cumulativeRewardPerToken = _cumulativeRewardPerToken + ((blockReward * PRECISION) / supply);
            cumulativeRewardPerToken = _cumulativeRewardPerToken;
        }

        // cumulativeRewardPerToken can only increase
        // so if cumulativeRewardPerToken is zero, it means there are no rewards yet
        if (_cumulativeRewardPerToken == 0) {
            return;
        }

        if (_account != address(0)) {
            uint256 stakedAmount = stakedAmounts[_account];
            uint256 accountReward =
                (stakedAmount * (_cumulativeRewardPerToken - previousCumulatedRewardPerToken[_account])) / PRECISION;
            uint256 _claimableReward = claimableReward[_account] + accountReward;

            claimableReward[_account] = _claimableReward;
            previousCumulatedRewardPerToken[_account] = _cumulativeRewardPerToken;

            if (_claimableReward > 0 && stakedAmounts[_account] > 0) {
                uint256 nextCumulativeReward = cumulativeRewards[_account] + accountReward;

                averageStakedAmounts[_account] = (
                    (averageStakedAmounts[_account] * cumulativeRewards[_account]) / nextCumulativeReward
                ) + (stakedAmount * accountReward) / nextCumulativeReward;

                cumulativeRewards[_account] = nextCumulativeReward;
            }
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity 0.8.18;

import {IERC20} from "./IERC20.sol";
import {IERC20Permit} from "./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 Use a ERC-2612 signature to set the `owner` approval toward `spender` on `token`.
     * Revert on invalid signature.
     */
    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);
        if (nonceAfter != nonceBefore + 1) {
            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).
     */
    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": {
    "src/staking/RewardTracker.sol": "RewardTracker"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": [
    ":@chainlink/contracts/=lib/chainlink/contracts/src/v0.6/",
    ":chainlink/=lib/chainlink/",
    ":ds-test/=lib/forge-std/lib/ds-test/src/",
    ":erc4626-tests/=lib/chainlink/contracts/foundry-lib/openzeppelin-contracts/lib/erc4626-tests/",
    ":forge-std/=lib/forge-std/src/"
  ]
}