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staking-rewards-updates

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pragma solidity ^0.5.16;

// Inheritance

// SPDX-License-Identifier: MIT AND AGPL-3.0-or-later

// This program is free software: you can redistribute it and/or modify

// it under the terms of the GNU Affero General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

// GNU Affero General Public License for more details.

// You should have received a copy of the GNU Affero General Public License

// along with this program. If not, see <https://www.gnu.org/licenses/>.

pragma solidity 0.8.19;

// https://docs.synthetix.io/contracts/source/interfaces/istakingrewards

interface IStakingRewards {

// Views

function balanceOf(address account) external view returns (uint256);

function earned(address account) external view returns (uint256);

function getRewardForDuration() external view returns (uint256);

function lastTimeRewardApplicable() external view returns (uint256);

function rewardPerToken() external view returns (uint256);

function rewardsDistribution() external view returns (address);

function rewardsToken() external view returns (address);

function rewardsToken() external view returns (IERC20);

function stakingToken() external view returns (IERC20);

function totalSupply() external view returns (uint256);

// Mutative

function exit() external;

function getReward() external;

function stake(uint256 amount) external;

function stake(uint256 amount, uint16 referral) external;

function withdraw(uint256 amount) external;

function notifyRewardAmount(uint256 reward) external;

function setRewardsDistribution(address _rewardsDistribution) external;

}

// SPDX-License-Identifier: MIT AND AGPL-3.0-or-later

// This program is free software: you can redistribute it and/or modify

// it under the terms of the GNU Affero General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

// GNU Affero General Public License for more details.

// You should have received a copy of the GNU Affero General Public License

// along with this program. If not, see <https://www.gnu.org/licenses/>.

// Inheritance

// SPDX-License-Identifier: MIT AND AGPL-3.0-or-later

// This program is free software: you can redistribute it and/or modify

// it under the terms of the GNU Affero General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

// GNU Affero General Public License for more details.

// You should have received a copy of the GNU Affero General Public License

// along with this program. If not, see <https://www.gnu.org/licenses/>.

// https://docs.synthetix.io/contracts/source/contracts/owned

contract Owned {

address public owner;

address public nominatedOwner;

constructor(address _owner) public {

constructor(address _owner) {

require(_owner != address(0), "Owner address cannot be 0");

owner = _owner;

emit OwnerChanged(address(0), _owner);

}

function nominateNewOwner(address _owner) external onlyOwner {

nominatedOwner = _owner;

emit OwnerNominated(_owner);

}

function acceptOwnership() external {

require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");

emit OwnerChanged(owner, nominatedOwner);

owner = nominatedOwner;

nominatedOwner = address(0);

}

modifier onlyOwner {

modifier onlyOwner() {

_onlyOwner();

}

function _onlyOwner() private view {

require(msg.sender == owner, "Only the contract owner may perform this action");

}

event OwnerNominated(address newOwner);

event OwnerChanged(address oldOwner, address newOwner);

}

// https://docs.synthetix.io/contracts/source/contracts/rewardsdistributionrecipient

contract RewardsDistributionRecipient is Owned {

address public rewardsDistribution;

function notifyRewardAmount(uint256 reward) external;

Text moved to lines 324-328

modifier onlyRewardsDistribution() {

require(msg.sender == rewardsDistribution, "Caller is not RewardsDistribution contract");

}

function setRewardsDistribution(address _rewardsDistribution) external onlyOwner {

rewardsDistribution = _rewardsDistribution;

}

// Inheritance

// https://docs.synthetix.io/contracts/source/contracts/pausable

contract Pausable is Owned {

abstract contract Pausable is Owned {

uint public lastPauseTime;

bool public paused;

constructor() internal {

constructor(address _owner) Owned(_owner) {}

// This contract is abstract, and thus cannot be instantiated directly

require(owner != address(0), "Owner must be set");

// Paused will be false, and lastPauseTime will be 0 upon initialisation

}

/**

* @notice Change the paused state of the contract

* @dev Only the contract owner may call this.

function setPaused(bool _paused) external onlyOwner {

// Ensure we're actually changing the state before we do anything

if (_paused == paused) {

return;

}

// Set our paused state.

paused = _paused;

// If applicable, set the last pause time.

if (paused) {

lastPauseTime = now;

lastPauseTime = block.timestamp;

}

// Let everyone know that our pause state has changed.

emit PauseChanged(paused);

}

event PauseChanged(bool isPaused);

modifier notPaused {

modifier notPaused() {

require(!paused, "This action cannot be performed while the contract is paused");

}

// https://docs.synthetix.io/contracts/source/contracts/stakingrewards

contract StakingRewards is IStakingRewards, RewardsDistributionRecipient, ReentrancyGuard, Pausable {

contract StakingRewards is IStakingRewards, Pausable, ReentrancyGuard {

using SafeMath for uint256;

using SafeERC20 for IERC20;

/* ========== STATE VARIABLES ========== */

IERC20 public rewardsToken;

IERC20 public immutable rewardsToken;

IERC20 public stakingToken;

IERC20 public immutable stakingToken;

address public rewardsDistribution;

uint256 public periodFinish = 0;

uint256 public rewardRate = 0;

uint256 public rewardsDuration = 7 days;

uint256 public lastUpdateTime;

uint256 public rewardPerTokenStored;

mapping(address => uint256) public userRewardPerTokenPaid;

mapping(address => uint256) public rewards;

uint256 private _totalSupply;

mapping(address => uint256) private _balances;

/* ========== CONSTRUCTOR ========== */

constructor(

address _owner,

address _rewardsDistribution,

address _rewardsToken,

address _stakingToken

) public Owned(_owner) {

) Pausable(_owner) {

rewardsToken = IERC20(_rewardsToken);

stakingToken = IERC20(_stakingToken);

rewardsDistribution = _rewardsDistribution;

}

/* ========== VIEWS ========== */

function totalSupply() external view returns (uint256) {

return _totalSupply;

}

function balanceOf(address account) external view returns (uint256) {

return _balances[account];

}

function lastTimeRewardApplicable() public view returns (uint256) {

return block.timestamp < periodFinish ? block.timestamp : periodFinish;

}

function rewardPerToken() public view returns (uint256) {

if (_totalSupply == 0) {

return rewardPerTokenStored;

}

return

rewardPerTokenStored.add(

rewardPerTokenStored + (((lastTimeRewardApplicable() - lastUpdateTime) * rewardRate * 1e18) / _totalSupply);

lastTimeRewardApplicable().sub(lastUpdateTime).mul(rewardRate).mul(1e18).div(_totalSupply)

);

}

function earned(address account) public view returns (uint256) {

return _balances[account].mul(rewardPerToken().sub(userRewardPerTokenPaid[account])).div(1e18).add(rewards[account]);

return (_balances[account] * (rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18 + rewards[account];

}

function getRewardForDuration() external view returns (uint256) {

return rewardRate.mul(rewardsDuration);

return rewardRate * rewardsDuration;

}

/* ========== MUTATIVE FUNCTIONS ========== */

function stake(uint256 amount) external nonReentrant notPaused updateReward(msg.sender) {

function stake(uint256 amount) public nonReentrant notPaused updateReward(msg.sender) {

require(amount > 0, "Cannot stake 0");

_totalSupply = _totalSupply.add(amount);

_totalSupply = _totalSupply + amount;

_balances[msg.sender] = _balances[msg.sender].add(amount);

_balances[msg.sender] = _balances[msg.sender] + amount;

stakingToken.safeTransferFrom(msg.sender, address(this), amount);

emit Staked(msg.sender, amount);

}

function stake(uint256 amount, uint16 referral) external {

stake(amount);

emit Referral(referral, msg.sender, amount);

}

function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) {

require(amount > 0, "Cannot withdraw 0");

_totalSupply = _totalSupply.sub(amount);

_totalSupply = _totalSupply - amount;

_balances[msg.sender] = _balances[msg.sender].sub(amount);

_balances[msg.sender] = _balances[msg.sender] - amount;

stakingToken.safeTransfer(msg.sender, amount);

emit Withdrawn(msg.sender, amount);

}

function getReward() public nonReentrant updateReward(msg.sender) {

uint256 reward = rewards[msg.sender];

if (reward > 0) {

rewards[msg.sender] = 0;

rewardsToken.safeTransfer(msg.sender, reward);

emit RewardPaid(msg.sender, reward);

}

function exit() external {

withdraw(_balances[msg.sender]);

getReward();

}

/* ========== RESTRICTED FUNCTIONS ========== */

function notifyRewardAmount(uint256 reward) external onlyRewardsDistribution updateReward(address(0)) {

function notifyRewardAmount(uint256 reward) external override onlyRewardsDistribution updateReward(address(0)) {

if (block.timestamp >= periodFinish) {

rewardRate = reward.div(rewardsDuration);

rewardRate = reward / rewardsDuration;

} else {

uint256 remaining = periodFinish.sub(block.timestamp);

uint256 remaining = periodFinish - block.timestamp;

uint256 leftover = remaining.mul(rewardRate);

uint256 leftover = remaining * rewardRate;

rewardRate = reward.add(leftover).div(rewardsDuration);

rewardRate = (reward + leftover) / rewardsDuration;

}

// Ensure the provided reward amount is not more than the balance in the contract.

// This keeps the reward rate in the right range, preventing overflows due to

// very high values of rewardRate in the earned and rewardsPerToken functions;

// Reward + leftover must be less than 2^256 / 10^18 to avoid overflow.

uint balance = rewardsToken.balanceOf(address(this));

require(rewardRate <= balance.div(rewardsDuration), "Provided reward too high");

require(rewardRate <= balance / rewardsDuration, "Provided reward too high");

lastUpdateTime = block.timestamp;

periodFinish = block.timestamp.add(rewardsDuration);

periodFinish = block.timestamp + rewardsDuration;

emit RewardAdded(reward);

}

// Added to support recovering LP Rewards from other systems such as BAL to be distributed to holders

function recoverERC20(address tokenAddress, uint256 tokenAmount) external onlyOwner {

require(tokenAddress != address(stakingToken), "Cannot withdraw the staking token");

IERC20(tokenAddress).safeTransfer(owner, tokenAmount);

emit Recovered(tokenAddress, tokenAmount);

}

function setRewardsDuration(uint256 _rewardsDuration) external onlyOwner {

require(

block.timestamp > periodFinish,

"Previous rewards period must be complete before changing the duration for the new period"

);

rewardsDuration = _rewardsDuration;

emit RewardsDurationUpdated(rewardsDuration);

}

function setRewardsDistribution(address _rewardsDistribution) external onlyOwner {

rewardsDistribution = _rewardsDistribution;

emit RewardsDistributionUpdated(rewardsDistribution);

}

/* ========== MODIFIERS ========== */

modifier updateReward(address account) {

rewardPerTokenStored = rewardPerToken();

lastUpdateTime = lastTimeRewardApplicable();

if (account != address(0)) {

rewards[account] = earned(account);

userRewardPerTokenPaid[account] = rewardPerTokenStored;

}

Text moved from lines 80-84

modifier onlyRewardsDistribution() {

require(msg.sender == rewardsDistribution, "Caller is not RewardsDistribution contract");

}

/* ========== EVENTS ========== */

event RewardAdded(uint256 reward);

event Staked(address indexed user, uint256 amount);

event Referral(uint16 indexed referral, address indexed user, uint256 amount);

event Withdrawn(address indexed user, uint256 amount);

event RewardPaid(address indexed user, uint256 reward);

event RewardsDurationUpdated(uint256 newDuration);

event RewardsDistributionUpdated(address newRewardsDistribution);

event Recovered(address token, uint256 amount);

}

Saved diffs

Original text

Open file

pragma solidity ^0.5.16;

// Inheritance

// https://docs.synthetix.io/contracts/source/interfaces/istakingrewards
interface IStakingRewards {
    // Views

function balanceOf(address account) external view returns (uint256);

function earned(address account) external view returns (uint256);

function getRewardForDuration() external view returns (uint256);

function lastTimeRewardApplicable() external view returns (uint256);

function rewardPerToken() external view returns (uint256);

function rewardsDistribution() external view returns (address);

function rewardsToken() external view returns (address);

function totalSupply() external view returns (uint256);

// Mutative

function exit() external;

function getReward() external;

function stake(uint256 amount) external;

function withdraw(uint256 amount) external;
}

// Inheritance

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

constructor(address _owner) public {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

function acceptOwnership() external {
        require(msg.sender == nominatedOwner, "You must be nominated before you can accept ownership");
        emit OwnerChanged(owner, nominatedOwner);
        owner = nominatedOwner;
        nominatedOwner = address(0);
    }

modifier onlyOwner {
        _onlyOwner();
        _;
    }

function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}

// https://docs.synthetix.io/contracts/source/contracts/rewardsdistributionrecipient
contract RewardsDistributionRecipient is Owned {
    address public rewardsDistribution;

function notifyRewardAmount(uint256 reward) external;

modifier onlyRewardsDistribution() {
        require(msg.sender == rewardsDistribution, "Caller is not RewardsDistribution contract");
        _;
    }

function setRewardsDistribution(address _rewardsDistribution) external onlyOwner {
        rewardsDistribution = _rewardsDistribution;
    }
}

// Inheritance

// https://docs.synthetix.io/contracts/source/contracts/pausable
contract Pausable is Owned {
    uint public lastPauseTime;
    bool public paused;

constructor() internal {
        // This contract is abstract, and thus cannot be instantiated directly
        require(owner != address(0), "Owner must be set");
        // Paused will be false, and lastPauseTime will be 0 upon initialisation
    }

/**
     * @notice Change the paused state of the contract
     * @dev Only the contract owner may call this.
     */
    function setPaused(bool _paused) external onlyOwner {
        // Ensure we're actually changing the state before we do anything
        if (_paused == paused) {
            return;
        }

// Set our paused state.
        paused = _paused;

// If applicable, set the last pause time.
        if (paused) {
            lastPauseTime = now;
        }

// Let everyone know that our pause state has changed.
        emit PauseChanged(paused);
    }

event PauseChanged(bool isPaused);

modifier notPaused {
        require(!paused, "This action cannot be performed while the contract is paused");
        _;
    }
}

// https://docs.synthetix.io/contracts/source/contracts/stakingrewards
contract StakingRewards is IStakingRewards, RewardsDistributionRecipient, ReentrancyGuard, Pausable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

/* ========== STATE VARIABLES ========== */

IERC20 public rewardsToken;
    IERC20 public stakingToken;
    uint256 public periodFinish = 0;
    uint256 public rewardRate = 0;
    uint256 public rewardsDuration = 7 days;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;

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

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

/* ========== CONSTRUCTOR ========== */

constructor(
        address _owner,
        address _rewardsDistribution,
        address _rewardsToken,
        address _stakingToken
    ) public Owned(_owner) {
        rewardsToken = IERC20(_rewardsToken);
        stakingToken = IERC20(_stakingToken);
        rewardsDistribution = _rewardsDistribution;
    }

/* ========== VIEWS ========== */

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

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

function lastTimeRewardApplicable() public view returns (uint256) {
        return block.timestamp < periodFinish ? block.timestamp : periodFinish;
    }

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

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

function getRewardForDuration() external view returns (uint256) {
        return rewardRate.mul(rewardsDuration);
    }

/* ========== MUTATIVE FUNCTIONS ========== */

function stake(uint256 amount) external nonReentrant notPaused updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        _totalSupply = _totalSupply.add(amount);
        _balances[msg.sender] = _balances[msg.sender].add(amount);
        stakingToken.safeTransferFrom(msg.sender, address(this), amount);
        emit Staked(msg.sender, amount);
    }

function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply = _totalSupply.sub(amount);
        _balances[msg.sender] = _balances[msg.sender].sub(amount);
        stakingToken.safeTransfer(msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }

function getReward() public nonReentrant updateReward(msg.sender) {
        uint256 reward = rewards[msg.sender];
        if (reward > 0) {
            rewards[msg.sender] = 0;
            rewardsToken.safeTransfer(msg.sender, reward);
            emit RewardPaid(msg.sender, reward);
        }
    }

function exit() external {
        withdraw(_balances[msg.sender]);
        getReward();
    }

/* ========== RESTRICTED FUNCTIONS ========== */

function notifyRewardAmount(uint256 reward) external onlyRewardsDistribution updateReward(address(0)) {
        if (block.timestamp >= periodFinish) {
            rewardRate = reward.div(rewardsDuration);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRate);
            rewardRate = reward.add(leftover).div(rewardsDuration);
        }

// Ensure the provided reward amount is not more than the balance in the contract.
        // This keeps the reward rate in the right range, preventing overflows due to
        // very high values of rewardRate in the earned and rewardsPerToken functions;
        // Reward + leftover must be less than 2^256 / 10^18 to avoid overflow.
        uint balance = rewardsToken.balanceOf(address(this));
        require(rewardRate <= balance.div(rewardsDuration), "Provided reward too high");

lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(rewardsDuration);
        emit RewardAdded(reward);
    }

// Added to support recovering LP Rewards from other systems such as BAL to be distributed to holders
    function recoverERC20(address tokenAddress, uint256 tokenAmount) external onlyOwner {
        require(tokenAddress != address(stakingToken), "Cannot withdraw the staking token");
        IERC20(tokenAddress).safeTransfer(owner, tokenAmount);
        emit Recovered(tokenAddress, tokenAmount);
    }

function setRewardsDuration(uint256 _rewardsDuration) external onlyOwner {
        require(
            block.timestamp > periodFinish,
            "Previous rewards period must be complete before changing the duration for the new period"
        );
        rewardsDuration = _rewardsDuration;
        emit RewardsDurationUpdated(rewardsDuration);
    }

/* ========== MODIFIERS ========== */

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

/* ========== EVENTS ========== */

event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    event RewardsDurationUpdated(uint256 newDuration);
    event Recovered(address token, uint256 amount);
}

Changed text

Open file

// SPDX-FileCopyrightText: © 2019-2021 Synthetix
// SPDX-FileCopyrightText: © 2023 Dai Foundation <www.daifoundation.org>
// SPDX-License-Identifier: MIT AND AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
pragma solidity 0.8.19;

// https://docs.synthetix.io/contracts/source/interfaces/istakingrewards
interface IStakingRewards {
    // Views

function balanceOf(address account) external view returns (uint256);

function earned(address account) external view returns (uint256);

function getRewardForDuration() external view returns (uint256);

function lastTimeRewardApplicable() external view returns (uint256);

function rewardPerToken() external view returns (uint256);

function rewardsDistribution() external view returns (address);

function rewardsToken() external view returns (IERC20);

function stakingToken() external view returns (IERC20);

function totalSupply() external view returns (uint256);

// Mutative

function exit() external;

function getReward() external;

function stake(uint256 amount) external;

function stake(uint256 amount, uint16 referral) external;

function withdraw(uint256 amount) external;

function notifyRewardAmount(uint256 reward) external;

function setRewardsDistribution(address _rewardsDistribution) external;
}

// Inheritance
// SPDX-FileCopyrightText: © 2019-2021 Synthetix
// SPDX-FileCopyrightText: © 2023 Dai Foundation <www.daifoundation.org>
// SPDX-License-Identifier: MIT AND AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

// https://docs.synthetix.io/contracts/source/contracts/owned
contract Owned {
    address public owner;
    address public nominatedOwner;

constructor(address _owner) {
        require(_owner != address(0), "Owner address cannot be 0");
        owner = _owner;
        emit OwnerChanged(address(0), _owner);
    }

function nominateNewOwner(address _owner) external onlyOwner {
        nominatedOwner = _owner;
        emit OwnerNominated(_owner);
    }

modifier onlyOwner() {
        _onlyOwner();
        _;
    }

function _onlyOwner() private view {
        require(msg.sender == owner, "Only the contract owner may perform this action");
    }

event OwnerNominated(address newOwner);
    event OwnerChanged(address oldOwner, address newOwner);
}

// https://docs.synthetix.io/contracts/source/contracts/pausable
abstract contract Pausable is Owned {
    uint public lastPauseTime;
    bool public paused;

constructor(address _owner) Owned(_owner) {}

// Set our paused state.
        paused = _paused;

// If applicable, set the last pause time.
        if (paused) {
            lastPauseTime = block.timestamp;
        }

// Let everyone know that our pause state has changed.
        emit PauseChanged(paused);
    }

event PauseChanged(bool isPaused);

modifier notPaused() {
        require(!paused, "This action cannot be performed while the contract is paused");
        _;
    }
}

// https://docs.synthetix.io/contracts/source/contracts/stakingrewards
contract StakingRewards is IStakingRewards, Pausable, ReentrancyGuard {
    using SafeERC20 for IERC20;

/* ========== STATE VARIABLES ========== */

IERC20 public immutable rewardsToken;
    IERC20 public immutable stakingToken;

address public rewardsDistribution;
    uint256 public periodFinish = 0;
    uint256 public rewardRate = 0;
    uint256 public rewardsDuration = 7 days;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;

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

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

/* ========== CONSTRUCTOR ========== */

constructor(
        address _owner,
        address _rewardsDistribution,
        address _rewardsToken,
        address _stakingToken
    ) Pausable(_owner) {
        rewardsToken = IERC20(_rewardsToken);
        stakingToken = IERC20(_stakingToken);
        rewardsDistribution = _rewardsDistribution;
    }

/* ========== VIEWS ========== */

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

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

function lastTimeRewardApplicable() public view returns (uint256) {
        return block.timestamp < periodFinish ? block.timestamp : periodFinish;
    }

function rewardPerToken() public view returns (uint256) {
        if (_totalSupply == 0) {
            return rewardPerTokenStored;
        }
        return
            rewardPerTokenStored + (((lastTimeRewardApplicable() - lastUpdateTime) * rewardRate * 1e18) / _totalSupply);
    }

function earned(address account) public view returns (uint256) {
        return (_balances[account] * (rewardPerToken() - userRewardPerTokenPaid[account])) / 1e18 + rewards[account];
    }

function getRewardForDuration() external view returns (uint256) {
        return rewardRate * rewardsDuration;
    }

/* ========== MUTATIVE FUNCTIONS ========== */

function stake(uint256 amount) public nonReentrant notPaused updateReward(msg.sender) {
        require(amount > 0, "Cannot stake 0");
        _totalSupply = _totalSupply + amount;
        _balances[msg.sender] = _balances[msg.sender] + amount;
        stakingToken.safeTransferFrom(msg.sender, address(this), amount);
        emit Staked(msg.sender, amount);
    }

function stake(uint256 amount, uint16 referral) external {
        stake(amount);
        emit Referral(referral, msg.sender, amount);
    }

function withdraw(uint256 amount) public nonReentrant updateReward(msg.sender) {
        require(amount > 0, "Cannot withdraw 0");
        _totalSupply = _totalSupply - amount;
        _balances[msg.sender] = _balances[msg.sender] - amount;
        stakingToken.safeTransfer(msg.sender, amount);
        emit Withdrawn(msg.sender, amount);
    }

function exit() external {
        withdraw(_balances[msg.sender]);
        getReward();
    }

/* ========== RESTRICTED FUNCTIONS ========== */

function notifyRewardAmount(uint256 reward) external override onlyRewardsDistribution updateReward(address(0)) {
        if (block.timestamp >= periodFinish) {
            rewardRate = reward / rewardsDuration;
        } else {
            uint256 remaining = periodFinish - block.timestamp;
            uint256 leftover = remaining * rewardRate;
            rewardRate = (reward + leftover) / rewardsDuration;
        }

lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp + rewardsDuration;
        emit RewardAdded(reward);
    }

function setRewardsDistribution(address _rewardsDistribution) external onlyOwner {
        rewardsDistribution = _rewardsDistribution;
        emit RewardsDistributionUpdated(rewardsDistribution);
    }

/* ========== MODIFIERS ========== */

modifier onlyRewardsDistribution() {
        require(msg.sender == rewardsDistribution, "Caller is not RewardsDistribution contract");
        _;
    }

/* ========== EVENTS ========== */

event RewardAdded(uint256 reward);
    event Staked(address indexed user, uint256 amount);
    event Referral(uint16 indexed referral, address indexed user, uint256 amount);
    event Withdrawn(address indexed user, uint256 amount);
    event RewardPaid(address indexed user, uint256 reward);
    event RewardsDurationUpdated(uint256 newDuration);
    event RewardsDistributionUpdated(address newRewardsDistribution);
    event Recovered(address token, uint256 amount);
}