xOGN staking contract

contracts/ExponentialStaking.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.10;
+
+import {ERC20Votes} from "OpenZeppelin/openzeppelin-contracts@4.6.0/contracts/token/ERC20/extensions/ERC20Votes.sol";
+import {ERC20Permit} from
+    "OpenZeppelin/openzeppelin-contracts@4.6.0/contracts/token/ERC20/extensions/draft-ERC20Permit.sol";
+import {ERC20} from "OpenZeppelin/openzeppelin-contracts@4.6.0/contracts/token/ERC20/ERC20.sol";
+import {PRBMathUD60x18} from "paulrberg/prb-math@2.5.0/contracts/PRBMathUD60x18.sol";
+import {RewardsSource} from "./RewardsSource.sol";
+
+/// @title ExponentialStaking
+/// @author Daniel Von Fange
+/// @notice Provides staking, vote power history, vote delegation, and rewards
+/// distribution.
+///
+/// The balance received for staking (and thus the voting power and rewards
+/// distribution) goes up exponentially by the end of the staked period.
+contract ExponentialStaking is ERC20Votes {
+    uint256 public immutable epoch; // Start of staking program - timestamp
+    ERC20 public immutable asset; // Must not allow reentrancy
+    RewardsSource public immutable rewardsSource;
+    uint256 public immutable minStakeDuration; // in seconds
+    uint256 public constant maxStakeDuration = 365 days;
+    uint256 constant YEAR_BASE = 14e17;
+    int256 constant NEW_STAKE = -1;
+
+    // 2. Staking and Lockup Storage
+    struct Lockup {
+        uint128 amount;
+        uint128 end;
+        uint256 points;
+    }
+
+    mapping(address => Lockup[]) public lockups;
+
+    // 3. Reward Storage
+    mapping(address => uint256) public rewardDebtPerShare;
+    uint256 public accRewardPerShare;
+
+    // Events
+    event Stake(address indexed user, uint256 lockupId, uint256 amount, uint256 end, uint256 points);
+    event Unstake(address indexed user, uint256 lockupId, uint256 amount, uint256 end, uint256 points);
+    event Reward(address indexed user, uint256 amount);
+    event Penalty(address indexed user, uint256 amount);
+
+    // Core ERC20 Functions
+
+    constructor(address asset_, uint256 epoch_, uint256 minStakeDuration_, address rewardsSource_)
+        ERC20("", "")
+        ERC20Permit("xOGN")
+    {
+        asset = ERC20(asset_);
+        epoch = epoch_;
+        minStakeDuration = minStakeDuration_;
+        rewardsSource = RewardsSource(rewardsSource_);
+    }
+
+    function name() public pure override returns (string memory) {
+        return "Staked OGN";
+    }
+
+    function symbol() public pure override returns (string memory) {
+        return "xOGN";
+    }
+
+    function transfer(address, uint256) public override returns (bool) {
+        revert("Staking: Transfers disabled");
+    }
+
+    function transferFrom(address, address, uint256) public override returns (bool) {
+        revert("Staking: Transfers disabled");
+    }
+
+    // Staking Functions
+
+    /// @notice Stake asset to an address that may not be the same as the
+    /// sender of the funds. This can be used to give staked funds to someone
+    /// else.
+    ///
+    /// If staking before the start of staking (epoch), then the lockup start
+    /// and end dates are shifted forward so that the lockup starts at the
+    /// epoch.
+    ///
+    /// Any rewards previously earned will be paid out or rolled into the stake.
+    ///
+    /// @param amountIn asset to lockup in the stake
+    /// @param duration in seconds for the stake
+    /// @param to address to receive ownership of the stake
+    /// @param stakeRewards should pending user rewards be added to the stake
+    /// @param lockupId previous stake to extend / add funds to. -1 to create a new stake.
+    function stake(uint256 amountIn, uint256 duration, address to, bool stakeRewards, int256 lockupId) external {
+        require(to != address(0), "Staking: To the zero address");
+        require(duration >= minStakeDuration, "Staking: Too short");
+        // Too long checked in preview points
+
+        uint256 newAmount = amountIn;
+        uint256 oldPoints = 0;
+        uint256 oldEnd = 0;
+        Lockup memory lockup;
+
+        // Allow gifts, but not control of other's accounts
+        if (to != msg.sender) {
+            require(stakeRewards == false, "Staking: Self only");
+            require(lockupId == NEW_STAKE, "Staking: Self only");
+        }
+
+        // Collect funds from user
+        if (amountIn > 0) {
+            // Important that `msg.sender` aways pays, not the `to` address.
+            asset.transferFrom(msg.sender, address(this), amountIn);
+            // amountIn already added into newAmount during initialization
+        }
+
+        // Collect funds from old stake (optional)
+        if (lockupId != NEW_STAKE) {
+            lockup = lockups[to][uint256(lockupId)];
+            uint256 oldAmount = lockup.amount;
+            oldEnd = lockup.end;
+            oldPoints = lockup.points;
+            require(oldAmount > 1, "Staking: Already closed stake");
+            emit Unstake(to, uint256(lockupId), oldAmount, oldEnd, oldPoints);
+            newAmount += oldAmount;
+        }
+
+        // Collect funds from rewards (optional)
+        newAmount += _collectRewards(to, stakeRewards);
+
+        // Caculate Points and lockup
+        require(newAmount > 0, "Staking: Not enough");
+        require(newAmount <= type(uint128).max, "Staking: Too much");
+        (uint256 newPoints, uint256 newEnd) = previewPoints(newAmount, duration);
+        require(newPoints + totalSupply() <= type(uint192).max, "Staking: Max points exceeded");
+        lockup.end = uint128(newEnd);
+        lockup.amount = uint128(newAmount); // max checked in require above
+        lockup.points = newPoints;
+
+        // Update or create lockup
+        if (lockupId != NEW_STAKE) {
+            require(newEnd >= oldEnd, "Staking: New lockup must not be shorter");
+            require(newPoints > oldPoints, "Staking: Must have increased amount or duration");
+            lockups[to][uint256(lockupId)] = lockup;
+        } else {
+            lockups[to].push(lockup);
+            uint256 numLockups = lockups[to].length;
+            require(numLockups < uint256(type(int256).max), "Staking: Too many lockups");
+            lockupId = int256(numLockups - 1);
+            // Delegate voting power to the receiver, if unregistered and first stake
+            if (numLockups == 1 && delegates(to) == address(0)) {
+                _delegate(to, to);
+            }
+        }
+        _mint(to, newPoints - oldPoints);
+        emit Stake(to, uint256(lockupId), newAmount, newEnd, newPoints);
+    }
+
+    /// @notice Collect staked asset for a lockup and any earned rewards.
+    /// @param lockupId the id of the lockup to unstake
+    function unstake(uint256 lockupId) external {
+        Lockup memory lockup = lockups[msg.sender][lockupId];
+        uint256 amount = lockup.amount;
+        uint256 end = lockup.end;
+        uint256 points = lockup.points;
+        require(end != 0, "Staking: Already unstaked this lockup");
+        _collectRewards(msg.sender, false);
+
+        uint256 withdrawAmount = previewWithdraw(amount, end);
+        uint256 penalty = amount - withdrawAmount;
+
+        delete lockups[msg.sender][lockupId]; // Keeps empty in array, so indexes are stable
+        _burn(msg.sender, points);
+        if (penalty > 0) {
+            asset.transfer(address(rewardsSource), penalty);
+            emit Penalty(msg.sender, penalty);
+        }
+        asset.transfer(msg.sender, withdrawAmount);
+        emit Unstake(msg.sender, lockupId, withdrawAmount, end, points);
+    }
+
+    // 3. Reward functions
+
+    /// @notice Collect all earned asset rewards.
+    function collectRewards() external {
+        _collectRewards(msg.sender, false);
+    }
+
+    /// @dev Internal function to handle rewards accounting.
+    ///
+    /// 1. Collect new rewards for everyone
+    /// 2. Calculate this user's rewards and accounting
+    /// 3. Distribute this user's rewards
+    ///
+    /// This function *must* be called before any user balance changes.
+    ///
+    /// This will always update the user's rewardDebtPerShare to match
+    /// accRewardPerShare, which is essential to the accounting.
+    ///
+    /// @param user to collect rewards for
+    /// @param shouldRetainRewards if true user's rewards kept in this contract rather than sent
+    /// @return retainedRewards amount of rewards not sent to user
+    function _collectRewards(address user, bool shouldRetainRewards) internal returns (uint256) {
+        uint256 supply = totalSupply();
+        if (supply > 0) {
+            uint256 preBalance = asset.balanceOf(address(this));
+            try rewardsSource.collectRewards() {}
+            catch {
+                // Governance staking should continue, even if rewards fail
+            }
+            uint256 collected = asset.balanceOf(address(this)) - preBalance;
+            accRewardPerShare += (collected * 1e12) / supply;
+        }
+        uint256 netRewardsPerShare = accRewardPerShare - rewardDebtPerShare[user];
+        uint256 netRewards = (balanceOf(user) * netRewardsPerShare) / 1e12;
+        rewardDebtPerShare[user] = accRewardPerShare;
+        if (netRewards == 0) {
+            return 0;
+        }
+        emit Reward(user, netRewards);
+        if (shouldRetainRewards) {
+            return netRewards;
+        } else {
+            asset.transfer(user, netRewards);
+        }
+    }
+
+    /// @notice Preview the number of points that would be returned for the
+    /// given amount and duration.
+    ///
+    /// @param amount asset to be staked
+    /// @param duration number of seconds to stake for
+    /// @return points staking points that would be returned
+    /// @return end staking period end date
+    function previewPoints(uint256 amount, uint256 duration) public view returns (uint256, uint256) {
+        require(duration <= maxStakeDuration, "Staking: Too long");
+        uint256 start = block.timestamp > epoch ? block.timestamp : epoch;
+        uint256 end = start + duration;
+        uint256 endYearpoc = ((end - epoch) * 1e18) / 365 days;
+        uint256 multiplier = PRBMathUD60x18.pow(YEAR_BASE, endYearpoc);
+        return ((amount * multiplier) / 1e18, end);
+    }
+
+    /// @notice Preview the amount of asset a user would receive if they collected
+    /// rewards at this time.
+    ///
+    /// @param user to preview rewards for
+    /// @return asset rewards amount
+    function previewRewards(address user) external view returns (uint256) {
+        uint256 supply = totalSupply();
+        if (supply == 0) {
+            return 0; // No one has any points to even get rewards
+        }
+        uint256 _accRewardPerShare = accRewardPerShare;
+        _accRewardPerShare += (rewardsSource.previewRewards() * 1e12) / supply;
+        uint256 netRewardsPerShare = _accRewardPerShare - rewardDebtPerShare[user];
+        return (balanceOf(user) * netRewardsPerShare) / 1e12;
+    }
+
+    /// @notice Preview the amount that a user would receive if they withdraw now.
+    /// This amount is after any early withdraw fees are removed for early withdraws.
+    /// @param amount staked asset amount to be withdrawn
+    /// @param end stake end date to be withdrawn from.
+    /// @return withdrawAmount amount of assets that the user will receive from withdraw
+    function previewWithdraw(uint256 amount, uint256 end) public view returns (uint256) {
+        if (block.timestamp >= end) {
+            return amount;
+        }
+        uint256 fullDuration = end - block.timestamp;
+        (uint256 fullPoints,) = previewPoints(1e18, fullDuration);
+        (uint256 currentPoints,) = previewPoints(1e36, 0); // 1e36 saves a later multiplication
+        return amount * ((currentPoints / fullPoints)) / 1e18;
+    }
+
+    /// @notice Returns the total number of lockups the user has
+    ///         created so far (including expired & unstaked ones)
+    /// @param user Address
+    /// @return asset Number of lockups the user has had
+    function lockupsCount(address user) external view returns (uint256) {
+        return lockups[user].length;
+    }
+}