SushiSwap Staking Rewards

Fork of lidofinance/staking-rewards-manager repository.

Contains the implementation of Rewarder for SushiSwap's MasterChefV2 contract and helper RewardsManager contract for simplifying managing it via DAO voting. Rewarder is based on Synthetix's StakingRewards.sol contract which Lido has previously used in Curve's liquidity pool.

Core Contracts

StakingRewards.sol

To use StakingRewards contract as a base contract for SushiRewarder, the following changes have been applied to StakingRewards.sol contract:

• Methods stake(uint256 amount), withdraw(uint256 amount), and exit() have been removed. MasterChefV2 will take control over these operations.
• External method getReward() has been replaced by the internal method _payReward(address user, address recipient) which allows paying user's rewards to another recipient's address.
• Since reward might be paid to address different from user's address, event RewardPaid(address indexed user, uint256 reward) has been changed as follows: RewardPaid(address indexed user, address indexed recipient, uint256 reward).
• Events Staked and Withdrawn have been removed as unnecessary.
• Method totalSupply() has been marked as abstract and it's visibility changed to public.
• Variable _totalSupply has been removed and replaced by totalSupply() view everywhere.
• Constructor of the contract have become internal because the contract is abstract now and can't be deployed.
• Visibility of _balances variable has been changed from private to internal. This is necessary to make it accessible in the child contracts.
• Method updatePeriodFinish(uint timestamp) has been added (method has been also added into original Synthetix's StakingRewards contract after creation of repo lidofinance/staking-rewards-manager). This method might be helpful for emergency stop of reward distribution (periodFinish value might be set to past block, and new rewards will not be distributed.)

The above changes don't involve rewards calculation logic and only modify the interface of the contract to make it possible to use it as a base contract for different rewarder contracts. For example, we can implement the current Lido's Curve contract using the modified StakingRewards contract as a base contract, or implement a rewarder for SushiSwap's liquidity pool.

StakingRewardsSushi.sol

Inherits logic from StakingRewards contract and implements Sushi's IRewarder interface to make it possible to use as a rewarder in MasterChefV2 contract.

To be used in MasterChefV2 contract, it has to implement the following interface:

interface IRewarder {
    function onSushiReward(
        uint256 pid,
        address user,
        address recipient,
        uint256 sushiAmount,
        uint256 newLpAmount
    ) external;

    function pendingTokens(
        uint256 pid,
        address user,
        uint256 sushiAmount
    ) external view returns (IERC20[] memory, uint256[] memory);
}

Method pendingTokens is used by SushiSwap's UI and must return a tuple with a list of rewardTokens distributed by the rewarder and a list of amounts of tokens gained by the user. In current implementation SushiStakingRewards distributes only one rewardsToken, and returns next value from pendingTokens method: ([rewardsToken], [earned(msg.sender)]) if was passed correct pid value. Returns tuple with empty arrays in other cases.

Method onSushiReward is executed on the distribution of rewards with the user and the amount of Sushi given out being specified, or on any change of user's balance of stakingToken. In the current implementation, this method validates that method has been called by MasterChefV2 contract with correct pid value, calls method _payReward(user, recipient) and updates user balance in _balances mapping.

To be deployable, SushiStakingRewards implements abstract method totalSupply() from StakingRewards.sol contract as follows:

function totalSupply() public view returns (uint256) {
    return stakingToken.balanceOf(MASTERCHEF_V2);
}

where MASTERCHEF_V2 is the address of MasterChefV2 contract.

To make StakingRewardsSushi rewarder compatible with SushiSwap's default UI, the next view methods were added:

• rewardPerSecond() - returns rewardRate value from base StakingRewards contract if current reward period hasn't finished yet (current block timestamp is less than periodFinish value) and 0 in other cases.
• rewardToken() - returns value of rewardsToken variable from base StringRewards contract

RewardsManager.vy

This contract simplifies operations with reward periods of StakingRewards contracts for the DAO. Compared to the original repository next changes were applied:

• Was added method period_finish() which returns end of the rewards period of StakingRewards contract. This method will help retrieve all info required to start a new reward period directly from the manager contract.
• Method recover_erc20() now accepts _amount as the second argument to allow recovery of the exact amount of tokens instead of the whole balance.

Project Setup

To use the tools provided by this project, please pull the repository from GitHub and install its dependencies as follows. It is recommended to use a Python virtual environment.

git clone https://github.com/lidofinance/staking-rewards-sushi
cd staking-rewards-sushi
npm install
poetry install
poetry shell

Compile the smart contracts:

brownie compile # add `--size` to see contract compiled sizes

Scripts

deploy.py

Contains script to deploy StakingRewardsSushi and RewardsManager contracts. The script requires DEPLOYER ENV variable be set.