VirtualBalanceRewardPool.sol

// SPDX-License-Identifier: MIT
pragma solidity 0.6.12;
/**
 *Submitted for verification at Etherscan.io on 2020-07-17
 */

/*
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  / __/__ __ ___  / /_ / /  ___  / /_ (_)__ __
 _\ \ / // // _ \/ __// _ \/ -_)/ __// / \ \ /
/___/ \_, //_//_/\__//_//_/\__/ \__//_/ /_\_\
     /___/

* Synthetix: VirtualBalanceRewardPool.sol
*
* Docs: https://docs.synthetix.io/
*
*
* MIT License
* ===========
*
* Copyright (c) 2020 Synthetix
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
*/

import "./Interfaces.sol";
import "./interfaces/MathUtil.sol";
import "@openzeppelin/contracts-0.6/math/SafeMath.sol";
import "@openzeppelin/contracts-0.6/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts-0.6/utils/Address.sol";
import "@openzeppelin/contracts-0.6/token/ERC20/SafeERC20.sol";


abstract contract VirtualBalanceWrapper {
    using SafeMath for uint256;
    using SafeERC20 for IERC20;

    IDeposit public immutable deposits;

    constructor(address deposit_) internal {
        deposits = IDeposit(deposit_);
    }

    function totalSupply() public view returns (uint256) {
        return deposits.totalSupply();
    }

    function balanceOf(address account) public view returns (uint256) {
        return deposits.balanceOf(account);
    }
}

/**
 * @title   VirtualBalanceRewardPool
 * @author  ConvexFinance
 * @notice  Reward pool used for ExtraRewards in Booster lockFees (3crv) and
 *          Extra reward stashes
 * @dev     The rewards are sent to this contract for distribution to stakers. This
 *          contract does not hold any of the staking tokens it just maintains a virtual
 *          balance of what a user has staked in the staking pool (BaseRewardPool).
 *          For example the Booster sends veCRV fees (3Crv) to a VirtualBalanceRewardPool
 *          which tracks the virtual balance of cxvCRV stakers and distributes their share
 *          of 3Crv rewards
 */
contract VirtualBalanceRewardPool is VirtualBalanceWrapper {
    using SafeERC20 for IERC20;
    
    IERC20 public immutable rewardToken;
    uint256 public constant duration = 7 days;

    address public immutable operator;

    uint256 public periodFinish = 0;
    uint256 public rewardRate = 0;
    uint256 public lastUpdateTime;
    uint256 public rewardPerTokenStored;
    uint256 public queuedRewards = 0;
    uint256 public currentRewards = 0;
    uint256 public historicalRewards = 0;
    uint256 public constant newRewardRatio = 830;
    mapping(address => uint256) public userRewardPerTokenPaid;
    mapping(address => uint256) public rewards;

    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);

    /**
     * @param deposit_  Parent deposit pool e.g cvxCRV staking in BaseRewardPool
     * @param reward_   The rewards token e.g 3Crv
     * @param op_       Operator contract (Booster)
     */
    constructor(
        address deposit_,
        address reward_,
        address op_
    ) public VirtualBalanceWrapper(deposit_) {
        rewardToken = IERC20(reward_);
        operator = op_;
    }


    /**
     * @notice Update rewards earned by this account
     */
    modifier updateReward(address account) {
        rewardPerTokenStored = rewardPerToken();
        lastUpdateTime = lastTimeRewardApplicable();
        if (account != address(0)) {
            rewards[account] = earned(account);
            userRewardPerTokenPaid[account] = rewardPerTokenStored;
        }
        _;
    }

    function lastTimeRewardApplicable() public view returns (uint256) {
        return MathUtil.min(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
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

    /**
     * @notice  Update reward, emit, call linked reward's stake
     * @dev     Callable by the deposits address which is the BaseRewardPool
     *          this updates the virtual balance of this user as this contract doesn't
     *          actually hold any staked tokens it just diributes reward tokens
     */
    function stake(address _account, uint256 amount)
        external
        updateReward(_account)
    {
        require(msg.sender == address(deposits), "!authorized");
       // require(amount > 0, 'VirtualDepositRewardPool: Cannot stake 0');
        emit Staked(_account, amount);
    }

    /**
     * @notice  Withdraw stake and update reward, emit, call linked reward's stake
     * @dev     See stake
     */
    function withdraw(address _account, uint256 amount)
        public
        updateReward(_account)
    {
        require(msg.sender == address(deposits), "!authorized");
        //require(amount > 0, 'VirtualDepositRewardPool : Cannot withdraw 0');

        emit Withdrawn(_account, amount);
    }

    /**
     * @notice  Get rewards for this account
     * @dev     This can be called directly but it is usually called by the
     *          BaseRewardPool getReward when the BaseRewardPool loops through
     *          it's extraRewards array calling getReward on all of them
     */
    function getReward(address _account) public updateReward(_account){
        uint256 reward = earned(_account);
        if (reward > 0) {
            rewards[_account] = 0;
            rewardToken.safeTransfer(_account, reward);
            emit RewardPaid(_account, reward);
        }
    }

    function getReward() external{
        getReward(msg.sender);
    }

    function donate(uint256 _amount) external returns(bool){
        IERC20(rewardToken).safeTransferFrom(msg.sender, address(this), _amount);
        queuedRewards = queuedRewards.add(_amount);
    }

    function queueNewRewards(uint256 _rewards) external{
        require(msg.sender == operator, "!authorized");

        _rewards = _rewards.add(queuedRewards);

        if (block.timestamp >= periodFinish) {
            notifyRewardAmount(_rewards);
            queuedRewards = 0;
            return;
        }

        //et = now - (finish-duration)
        uint256 elapsedTime = block.timestamp.sub(periodFinish.sub(duration));
        //current at now: rewardRate * elapsedTime
        uint256 currentAtNow = rewardRate * elapsedTime;
        uint256 queuedRatio = currentAtNow.mul(1000).div(_rewards);
        if(queuedRatio < newRewardRatio){
            notifyRewardAmount(_rewards);
            queuedRewards = 0;
        }else{
            queuedRewards = _rewards;
        }
    }

    function notifyRewardAmount(uint256 reward)
        internal
        updateReward(address(0))
    {
        historicalRewards = historicalRewards.add(reward);
        if (block.timestamp >= periodFinish) {
            rewardRate = reward.div(duration);
        } else {
            uint256 remaining = periodFinish.sub(block.timestamp);
            uint256 leftover = remaining.mul(rewardRate);
            reward = reward.add(leftover);
            rewardRate = reward.div(duration);
        }
        currentRewards = reward;
        lastUpdateTime = block.timestamp;
        periodFinish = block.timestamp.add(duration);
        emit RewardAdded(reward);
    }
}