// File: contracts/MultiRewards.sol



/**
 * Fork of https://github.com/curvefi/multi-rewards/blob/master/contracts/MultiRewards.sol
 */

pragma solidity 0.5.17;

library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * This test is non-exhaustive, and there may be false-negatives: during the
     * execution of a contract's constructor, its address will be reported as
     * not containing a contract.
     *
     * > It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies in extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }
}

interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

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

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through `transferFrom`. This is
     * zero by default.
     *
     * This value changes when `approve` or `transferFrom` are called.
     */
    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * > Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an `Approval` event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a `Transfer` event.
     */
    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to `approve`. `value` is the new allowance.
     */
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

library Math {
    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a >= b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow, so we distribute
        return (a / 2) + (b / 2) + (((a % 2) + (b % 2)) / 2);
    }
}

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);
}

contract Pausable is Owned {
    uint256 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"
        );
        _;
    }
}

contract ReentrancyGuard {
    /// @dev counter to allow mutex lock with only one SSTORE operation
    uint256 private _guardCounter;

    constructor() internal {
        // The counter starts at one to prevent changing it from zero to a non-zero
        // value, which is a more expensive operation.
        _guardCounter = 1;
    }

    /**
     * @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 make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _guardCounter += 1;
        uint256 localCounter = _guardCounter;
        _;
        require(
            localCounter == _guardCounter,
            "ReentrancyGuard: reentrant call"
        );
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transfer.selector, to, value)
        );
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.transferFrom.selector, from, to, value)
        );
    }

    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(token.approve.selector, spender, value)
        );
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(
            value
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(
            value
        );
        callOptionalReturn(
            token,
            abi.encodeWithSelector(
                token.approve.selector,
                spender,
                newAllowance
            )
        );
    }

    /**
     * @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.

        // A Solidity high level call has three parts:
        //  1. The target address is checked to verify it contains contract code
        //  2. The call itself is made, and success asserted
        //  3. The return value is decoded, which in turn checks the size of the returned data.
        // solhint-disable-next-line max-line-length
        require(address(token).isContract(), "SafeERC20: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = address(token).call(data);
        require(success, "SafeERC20: low-level call failed");

        if (returndata.length > 0) {
            // Return data is optional
            // solhint-disable-next-line max-line-length
            require(
                abi.decode(returndata, (bool)),
                "SafeERC20: ERC20 operation did not succeed"
            );
        }
    }
}

library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        uint256 c = a - b;

        return c;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0, "SafeMath: division by zero");
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0, "SafeMath: modulo by zero");
        return a % b;
    }
}

interface IDigits {
    function claim() external;

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

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

    function triggerDividendDistribution() external;
}

contract MultiRewards is ReentrancyGuard, Pausable {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    uint256 private constant MAXUINT256 = 2**256 - 1;

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

    struct Reward {
        address rewardsDistributor;
        uint256 rewardsDuration;
        uint256 periodFinish;
        uint256 rewardRate;
        uint256 lastUpdateTime;
        uint256 rewardPerTokenStored;
    }
    IERC20 public stakingToken;
    IERC20 public reflectionToken;
    IDigits private _digits;

    mapping(address => Reward) public rewardData;
    address[] public rewardTokens;

    // user -> reward token -> amount
    mapping(address => mapping(address => uint256))
        public userRewardPerTokenPaid;
    mapping(address => mapping(address => uint256)) public rewards;

    uint256 private _reflectionPerToken;
    mapping(address => uint256) private _userReflectionPerTokenPaid;

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

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

    constructor(
        address _owner,
        address _stakingToken,
        address _reflectionToken
    ) public Owned(_owner) {
        stakingToken = IERC20(_stakingToken);
        reflectionToken = IERC20(_reflectionToken);
        _digits = IDigits(_stakingToken);
    }

    function addReward(
        address _rewardsToken,
        address _rewardsDistributor,
        uint256 _rewardsDuration
    ) public onlyOwner {
        require(
            rewardData[_rewardsToken].rewardsDuration == 0,
            "Token was already added"
        );
        require(_rewardsDuration > 0, "Reward duration must be non-zero");
        rewardTokens.push(_rewardsToken);
        rewardData[_rewardsToken].rewardsDistributor = _rewardsDistributor;
        rewardData[_rewardsToken].rewardsDuration = _rewardsDuration;
    }

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

    function rewardTokenLength() external view returns (uint256) {
        return rewardTokens.length;
    }

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

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

    function lastTimeRewardApplicable(address _rewardsToken)
        public
        view
        returns (uint256)
    {
        return
            Math.min(block.timestamp, rewardData[_rewardsToken].periodFinish);
    }

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

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

    function dividendsEarned(address account) public view returns (uint256) {
        return
            _balances[account]
                .mul(
                    _reflectionPerToken.sub(
                        _userReflectionPerTokenPaid[account]
                    )
                )
                .div(1e32);
    }

    function getRewardForDuration(address _rewardsToken)
        external
        view
        returns (uint256)
    {
        return
            rewardData[_rewardsToken].rewardRate.mul(
                rewardData[_rewardsToken].rewardsDuration
            );
    }

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

    function setRewardsDistributor(
        address _rewardsToken,
        address _rewardsDistributor
    ) external onlyOwner {
        rewardData[_rewardsToken].rewardsDistributor = _rewardsDistributor;
    }

    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) {
        for (uint256 i = 0; i < rewardTokens.length; i++) {
            address _rewardsToken = rewardTokens[i];
            uint256 reward = rewards[msg.sender][_rewardsToken];
            if (reward > 0) {
                rewards[msg.sender][_rewardsToken] = 0;
                IERC20(_rewardsToken).safeTransfer(msg.sender, reward);
                emit RewardPaid(msg.sender, _rewardsToken, reward);
            }
        }
    }

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

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

    function notifyRewardAmount(address _rewardsToken, uint256 reward)
        external
        updateReward(address(0))
    {
        require(rewardData[_rewardsToken].rewardsDistributor == msg.sender);
        // Reccomendation from Peckshield's audit of similar contract, they state
        // that too large reward can cause overflow in 'RewardPerToken()' function.
        // https://app.topshelf.finance/PeckShield-Audit-Report-Topshelf-v1.0.pdf
        require(
            reward.div(rewardData[_rewardsToken].rewardsDuration) <
                MAXUINT256.div(1e18),
            "Reward too large, would lock"
        );
        // handle the transfer of reward tokens via `transferFrom` to reduce the number
        // of transactions required and ensure correctness of the reward amount
        IERC20(_rewardsToken).safeTransferFrom(
            msg.sender,
            address(this),
            reward
        );

        if (block.timestamp >= rewardData[_rewardsToken].periodFinish) {
            rewardData[_rewardsToken].rewardRate = reward.div(
                rewardData[_rewardsToken].rewardsDuration
            );
        } else {
            uint256 remaining = rewardData[_rewardsToken].periodFinish.sub(
                block.timestamp
            );
            uint256 leftover = remaining.mul(
                rewardData[_rewardsToken].rewardRate
            );
            rewardData[_rewardsToken].rewardRate = reward.add(leftover).div(
                rewardData[_rewardsToken].rewardsDuration
            );
        }

        rewardData[_rewardsToken].lastUpdateTime = block.timestamp;
        rewardData[_rewardsToken].periodFinish = block.timestamp.add(
            rewardData[_rewardsToken].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 staking token"
        );
        require(
            rewardData[tokenAddress].lastUpdateTime == 0,
            "Cannot withdraw reward token"
        );
        IERC20(tokenAddress).safeTransfer(owner, tokenAmount);
        emit Recovered(tokenAddress, tokenAmount);
    }

    function setRewardsDuration(address _rewardsToken, uint256 _rewardsDuration)
        external
    {
        require(
            block.timestamp > rewardData[_rewardsToken].periodFinish,
            "Reward period still active"
        );
        require(rewardData[_rewardsToken].rewardsDistributor == msg.sender);
        require(_rewardsDuration > 0, "Reward duration must be non-zero");
        rewardData[_rewardsToken].rewardsDuration = _rewardsDuration;
        emit RewardsDurationUpdated(
            _rewardsToken,
            rewardData[_rewardsToken].rewardsDuration
        );
    }

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

    modifier updateReward(address account) {
        for (uint256 i; i < rewardTokens.length; i++) {
            address token = rewardTokens[i];
            rewardData[token].rewardPerTokenStored = rewardPerToken(token);
            rewardData[token].lastUpdateTime = lastTimeRewardApplicable(token);
            if (account != address(0)) {
                rewards[account][token] = earned(account, token);
                userRewardPerTokenPaid[account][token] = rewardData[token]
                    .rewardPerTokenStored;
            }
        }
        // In case something is wrong with claiming process, pausing will enable
        // withdrawals without processing any reflection logic
        if (account != address(0) && _totalSupply > 0 && !paused) {
            _processReflectionReward(account);
        }
        _;
    }

    /* ========== PRIVATE ========== */

    /**
     * Process reflection rewards before each `stake()`, `withdraw()`, `getReward()`.
     */
    function _processReflectionReward(address account) private {
        // Trigger dividend distribution
        _digits.triggerDividendDistribution();
        // We trust Digits implementation that `withdrawableDividendOf()`
        // is equal to amount checked in `processAccount()` in DividendTracker.sol.
        // which is called by `claim()` in Digits.sol
        uint256 reflection = _digits.withdrawableDividendOf(address(this));
        if (reflection > 0) {
            _digits.claim();
            _reflectionPerToken = reflection.mul(1e32).div(_totalSupply).add(
                _reflectionPerToken
            );
        }
        uint256 reward = dividendsEarned(account);
        _userReflectionPerTokenPaid[account] = _reflectionPerToken;
        if (reward > 0) {
            reflectionToken.safeTransfer(account, reward);
            emit ReflectionPaid(account, reward);
        }
    }

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

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