Draft Abstract Staking logic (#83)

* Draft Abstract Staking logic

* draft implementation

* Modified ValueDistributor and Staking contracts, added natspec comments

* Refactored ValueDistributor and Staking contracts.
Fixed some logic

* Modified ValueDistributor and Staking contracts

* Implemented tests for AbstractStaking and ValueDistributor contracts

* Refactored AbstractStaking and ValueDistributor contracts, added more tests

* Refactored AbstractStaking and ValueDistributor contracts

* Refactored tests and moved events to the AbstractValueDistributor contract

* Added 2 tests for AbstractStaking to reach the full coverage

* Updated the patch version

* Refactored AbstractStaking, AbstractValueDistributor and AbstractValueDistributorMock contracts

* Refactored AbstractStaking and AbstractValueDistributor contracts

---------

Co-authored-by: Artem Chystiakov <[email protected]>

contracts/mock/staking/AbstractStakingMock.sol

@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+import {Multicall} from "@openzeppelin/contracts/utils/Multicall.sol";
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+import {AbstractStaking} from "../../staking/AbstractStaking.sol";
+
+contract AbstractStakingMock is AbstractStaking, Multicall {
+    function __AbstractStakingMock_init(
+        address sharesToken_,
+        address rewardsToken_,
+        uint256 rate_,
+        uint256 stakingStartTime_
+    ) external initializer {
+        __AbstractStaking_init(sharesToken_, rewardsToken_, rate_, stakingStartTime_);
+    }
+
+    function mockInit(
+        address sharesToken_,
+        address rewardsToken_,
+        uint256 rate_,
+        uint256 stakingStartTime_
+    ) external {
+        __AbstractStaking_init(sharesToken_, rewardsToken_, rate_, stakingStartTime_);
+    }
+
+    function setStakingStartTime(uint256 stakingStartTime_) external {
+        _setStakingStartTime(stakingStartTime_);
+    }
+
+    function setRate(uint256 newRate_) external {
+        _setRate(newRate_);
+    }
+
+    function userShares(address user_) external view returns (uint256) {
+        return userDistribution(user_).shares;
+    }
+
+    function userOwedValue(address user_) external view returns (uint256) {
+        return userDistribution(user_).owedValue;
+    }
+}
+
+contract StakersFactory is Multicall {
+    Staker[] public stakers;
+
+    function createStaker() public {
+        Staker staker_ = new Staker();
+        stakers.push(staker_);
+    }
+
+    function stake(
+        address stakingContract_,
+        address staker_,
+        address token_,
+        uint256 amount_
+    ) external {
+        Staker(staker_).stake(stakingContract_, token_, amount_);
+    }
+
+    function unstake(address stakingContract_, address staker_, uint256 amount_) external {
+        Staker(staker_).unstake(stakingContract_, amount_);
+    }
+}
+
+contract Staker {
+    function stake(address stakingContract_, address token_, uint256 amount_) external {
+        IERC20(token_).approve(stakingContract_, amount_);
+        AbstractStakingMock(stakingContract_).stake(amount_);
+    }
+
+    function unstake(address stakingContract_, uint256 amount_) external {
+        AbstractStakingMock(stakingContract_).unstake(amount_);
+    }
+}

contracts/mock/staking/AbstractValueDistributorMock.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+import {Multicall} from "@openzeppelin/contracts/utils/Multicall.sol";
+
+import {AbstractValueDistributor} from "../../staking/AbstractValueDistributor.sol";
+import {DECIMAL} from "../../utils/Globals.sol";
+
+contract AbstractValueDistributorMock is AbstractValueDistributor, Multicall {
+    function addShares(address user_, uint256 amount_) external {
+        _addShares(user_, amount_);
+    }
+
+    function removeShares(address user_, uint256 amount_) external {
+        _removeShares(user_, amount_);
+    }
+
+    function distributeValue(address user_, uint256 amount_) external {
+        _distributeValue(user_, amount_);
+    }
+
+    function userShares(address user_) external view returns (uint256) {
+        return userDistribution(user_).shares;
+    }
+
+    function userOwedValue(address user_) external view returns (uint256) {
+        return userDistribution(user_).owedValue;
+    }
+
+    function _getValueToDistribute(
+        uint256 timeUpTo_,
+        uint256 timeLastUpdate_
+    ) internal view virtual override returns (uint256) {
+        return DECIMAL * (timeUpTo_ - timeLastUpdate_);
+    }
+}

contracts/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@solarity/solidity-lib",
-  "version": "2.6.13",
+  "version": "2.6.14",
   "license": "MIT",
   "author": "Distributed Lab",
   "readme": "README.md",

contracts/staking/AbstractStaking.sol

@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
+
+import {AbstractValueDistributor} from "./AbstractValueDistributor.sol";
+
+/**
+ * @notice The AbstractStaking module
+ *
+ * Contract module for staking tokens and earning rewards based on shares.
+ */
+abstract contract AbstractStaking is AbstractValueDistributor, Initializable {
+    using SafeERC20 for IERC20;
+
+    address private _sharesToken;
+    address private _rewardsToken;
+
+    /**
+     * @dev The rate of rewards distribution per second.
+     *
+     * It determines the rate at which rewards are earned and distributed
+     * to stakers based on their shares.
+     *
+     * Note: Ensure that the `_rate` value is set correctly to match
+     * the decimal precision of the `_rewardsToken` to ensure accurate rewards distribution.
+     */
+    uint256 private _rate;
+
+    uint256 private _stakingStartTime;
+
+    /**
+     * @dev Throws if the staking has not started yet.
+     */
+    modifier stakingStarted() {
+        _checkStakingStarted();
+        _;
+    }
+
+    /**
+     * @notice Initializes the contract setting the values provided as shares token, rewards token, reward rate and staking start time.
+     *
+     * Warning: when shares and rewards tokens are the same, users may accidentally withdraw
+     * other users' shares as a reward if the rewards token balance is improperly handled.
+     *
+     * @param sharesToken_ The address of the shares token.
+     * @param rewardsToken_ The address of the rewards token.
+     * @param rate_ The reward rate.
+     * @param stakingStartTime_ The staking start time
+     */
+    function __AbstractStaking_init(
+        address sharesToken_,
+        address rewardsToken_,
+        uint256 rate_,
+        uint256 stakingStartTime_
+    ) internal onlyInitializing {
+        require(sharesToken_ != address(0), "Staking: zero address cannot be the Shares Token");
+        require(rewardsToken_ != address(0), "Staking: zero address cannot be the Rewards Token");
+
+        _sharesToken = sharesToken_;
+        _rewardsToken = rewardsToken_;
+        _setRate(rate_);
+        _setStakingStartTime(stakingStartTime_);
+    }
+
+    /**
+     * @notice Stakes the specified amount of tokens.
+     * @param amount_ The amount of tokens to stake.
+     */
+    function stake(uint256 amount_) public stakingStarted {
+        _addShares(msg.sender, amount_);
+    }
+
+    /**
+     * @notice Unstakes the specified amount of tokens.
+     * @param amount_ The amount of tokens to unstake.
+     */
+    function unstake(uint256 amount_) public stakingStarted {
+        _removeShares(msg.sender, amount_);
+    }
+
+    /**
+     * @notice Claims the specified amount of rewards.
+     * @param amount_ The amount of rewards to claim.
+     */
+    function claim(uint256 amount_) public stakingStarted {
+        _distributeValue(msg.sender, amount_);
+    }
+
+    /**
+     * @notice Withdraws all the staked tokens together with rewards.
+     *
+     * Note: All the rewards are claimed after the shares are removed.
+     *
+     * @return shares_ The amount of shares being withdrawn.
+     * @return owedValue_ The total value of the rewards owed to the user.
+     */
+    function withdraw() public stakingStarted returns (uint256 shares_, uint256 owedValue_) {
+        shares_ = userDistribution(msg.sender).shares;
+        owedValue_ = getOwedValue(msg.sender);
+
+        unstake(shares_);
+        claim(owedValue_);
+    }
+
+    /**
+     * @notice Returns the shares token.
+     * @return The address of the shares token contract.
+     */
+    function sharesToken() public view returns (address) {
+        return _sharesToken;
+    }
+
+    /**
+     * @notice Returns the rewards token.
+     * @return The address of the rewards token contract.
+     */
+    function rewardsToken() public view returns (address) {
+        return _rewardsToken;
+    }
+
+    /**
+     * @notice Returns the staking start time.
+     * @return The timestamp when staking starts.
+     */
+    function stakingStartTime() public view returns (uint256) {
+        return _stakingStartTime;
+    }
+
+    /**
+     * @notice Returns the rate of rewards distribution.
+     * @return The rate of rewards distribution per second.
+     */
+    function rate() public view returns (uint256) {
+        return _rate;
+    }
+
+    /**
+     * @notice Sets the staking start time.
+     * @param stakingStartTime_ The timestamp when staking will start.
+     */
+    function _setStakingStartTime(uint256 stakingStartTime_) internal {
+        _stakingStartTime = stakingStartTime_;
+    }
+
+    /**
+     * @notice Sets the rate of rewards distribution per second.
+     * @param newRate_ The new rate of rewards distribution.
+     */
+    function _setRate(uint256 newRate_) internal {
+        _update(address(0));
+
+        _rate = newRate_;
+    }
+
+    /**
+     * @notice Hook function that is called after shares have been added to a user's distribution.
+     * @param user_ The address of the user.
+     * @param amount_ The amount of shares added.
+     */
+    function _afterAddShares(address user_, uint256 amount_) internal virtual override {
+        IERC20(_sharesToken).safeTransferFrom(user_, address(this), amount_);
+    }
+
+    /**
+     * @notice Hook function that is called after shares have been removed from a user's distribution.
+     * @param user_ The address of the user.
+     * @param amount_ The amount of shares removed.
+     */
+    function _afterRemoveShares(address user_, uint256 amount_) internal virtual override {
+        IERC20(_sharesToken).safeTransfer(user_, amount_);
+    }
+
+    /**
+     * @notice Hook function that is called after value has been distributed to a user.
+     * @param user_ The address of the user.
+     * @param amount_ The amount of value distributed.
+     */
+    function _afterDistributeValue(address user_, uint256 amount_) internal virtual override {
+        IERC20(_rewardsToken).safeTransfer(user_, amount_);
+    }
+
+    /**
+     * @dev Throws if the staking has not started yet.
+     */
+    function _checkStakingStarted() internal view {
+        require(block.timestamp >= _stakingStartTime, "Staking: staking has not started yet");
+    }
+
+    /**
+     * @notice Gets the value to be distributed for a given time period.
+     * @param timeUpTo_ The end timestamp of the period.
+     * @param timeLastUpdate_ The start timestamp of the period.
+     * @return The value to be distributed for the period.
+     */
+    function _getValueToDistribute(
+        uint256 timeUpTo_,
+        uint256 timeLastUpdate_
+    ) internal view virtual override returns (uint256) {
+        return _rate * (timeUpTo_ - timeLastUpdate_);
+    }
+}