Add SnapshotStakingPool and SignedSnapshotStakingPool

src/interfaces/staking/ISignedSnapshotStakingPool.sol

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.0;
+
+import {ISnapshotStakingPool} from "./ISnapshotStakingPool.sol";
+
+interface ISignedSnapshotStakingPool is ISnapshotStakingPool {
+
+    /// @notice Message to sign when staking
+    function message() external view returns (string memory);
+
+    /// @notice Mapping of approved stakers
+    function isApprovedStaker(address) external view returns (bool);
+
+    /// @notice Stake `amount` of stakeToken from `msg.sender` and mint staked tokens.
+    /// @param amount The amount of stakeToken to stake
+    /// @dev Must be an approved staker
+    function stake(uint256 amount) external;
+
+    /// @notice Stake `amount` of stakeToken from `msg.sender` and mint staked tokens.
+    /// @param amount The amount of stakeToken to stake
+    /// @param signature The signature of the message
+    /// @dev Approves the staker if not already approved
+    function stake(uint256 amount, bytes calldata signature) external;
+
+    /// @notice Approve the signer of the message as an approved staker
+    /// @param signature The signature of the message
+    function approveStaker(bytes calldata signature) external;
+
+    /// @notice Get the hashed digest of the message to be signed for staking
+    /// @return The hashed bytes to be signed
+    function getStakeSignatureDigest() external view returns (bytes32);
+}

src/interfaces/staking/ISnapshotStakingPool.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.0;
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+interface ISnapshotStakingPool is IERC20 {
+
+    /// @notice Token to be distributed as rewards
+    function rewardToken() external view returns (IERC20);
+
+    /// @notice Token to be staked
+    function stakeToken() external view returns (IERC20);
+
+    /// @notice Distributor of rewards
+    function distributor() external view returns (address);
+
+    /// @notice Snapshot delay
+    function snapshotDelay() external view returns (uint256);
+
+    /// @notice Last snapshot time
+    function lastSnapshotTime() external view returns (uint256);
+
+    /// @notice Next snapshot id for `account` to claim
+    function nextClaimId(address account) external view returns (uint256);
+
+    /// @notice Reward snapshot at `snapshotId`
+    function rewardSnapshots(uint256) external view returns (uint256);
+
+    /// @notice Get the reward snapshots
+    function getRewardSnapshots() external view returns (uint256[] memory);
+
+    /// @notice Stake `amount` of stakeToken from `msg.sender` and mint staked tokens.
+    /// @param amount The amount of stakeToken to stake
+    function stake(uint256 amount) external;
+
+    /// @notice Unstake `amount` of stakeToken by `msg.sender`.
+    /// @param amount The amount of stakeToken to unstake
+    function unstake(uint256 amount) external;
+
+    /// @notice ONLY DISTRIBUTOR: Accrue rewardToken and update snapshot.
+    /// @param amount The amount of rewardToken to accrue
+    function accrue(uint256 amount) external;
+
+    /// @notice Claim the staking rewards from pending snapshots for `msg.sender`.
+    function claim() external;
+
+    /// @notice Claim partial staking rewards from pending snapshots for `msg.sender` from `_startClaimId` to `_endClaimId`.
+    /// @param startSnapshotId The snapshot id to start the partial claim
+    /// @param endSnapshotId The snapshot id to end the partial claim
+    function claimPartial(uint256 startSnapshotId, uint256 endSnapshotId) external;
+
+    /* ========== Admin Functions ========== */
+
+    /// @notice ONLY OWNER: Update the distributor address.
+    /// @param newDistributor The new distributor address
+    function setDistributor(address newDistributor) external;
+
+    /// @notice ONLY OWNER: Update the snapshot delay. Can set to 0 to disable snapshot delay.
+    /// @param newSnapshotDelay The new snapshot delay
+    function setSnapshotDelay(uint256 newSnapshotDelay) external;
+
+    /* ========== View Functions ========== */
+
+    /// @notice Get the current snapshot id.
+    /// @return The current snapshot id
+    function getCurrentSnapshotId() external view returns (uint256);
+
+    /// @notice Retrieves the rewards pending to be claimed by `account`.
+    /// @param account The account to retrieve pending rewards for
+    /// @return The rewards pending to be claimed by `account`
+    function getPendingRewards(address account) external view returns (uint256);
+
+    /// @notice Retrives the rewards of `account` in the range of `startSnapshotId` to `endSnapshotId`.
+    /// @param account The account to retrieve rewards for
+    /// @param startSnapshotId The start snapshot id
+    /// @param endSnapshotId The end snapshot id
+    /// @return The rewards of `account` in the range of `startSnapshotId` to `endSnapshotId`
+    function rewardOfInRange(address account, uint256 startSnapshotId, uint256 endSnapshotId) external view returns (uint256);
+
+    /// @notice Retrieves the rewards of `account` at the `snapshotId`.
+    /// @param account The account to retrieve rewards for
+    /// @param snapshotId The snapshot id
+    /// @return The rewards of `account` at the `snapshotId`
+    function rewardOfAt(address account, uint256 snapshotId) external view returns (uint256);
+
+    /// @notice Retrieves the total pool reward at the time `snapshotId`.
+    /// @param snapshotId The snapshot id
+    /// @return The total pool reward at the time `snapshotId`
+    function rewardAt(uint256 snapshotId) external view returns (uint256);
+
+    /// @notice Check if rewards can be accrued.
+    /// @return Boolean indicating if rewards can be accrued
+    function canAccrue() external view returns (bool);
+
+    /// @notice Get the time until the next snapshot.
+    /// @return The time until the next snapshot
+    function getTimeUntilNextSnapshot() external view returns (uint256);
+}

src/staking/SignedSnapshotStakingPool.sol

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+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.0;
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import {ISignedSnapshotStakingPool} from "../interfaces/staking/ISignedSnapshotStakingPool.sol";
+
+import {EIP712} from "@openzeppelin/contracts/utils/cryptography/EIP712.sol";
+import {SignatureChecker} from "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";
+import {SnapshotStakingPool} from "./SnapshotStakingPool.sol";
+
+/// @title SignedSnapshotStakingPool
+/// @author Index Cooperative
+/// @notice A contract for staking `stakeToken` and receiving `rewardToken` based 
+/// on snapshots taken when rewards are accrued.
+contract SignedSnapshotStakingPool is ISignedSnapshotStakingPool, SnapshotStakingPool, EIP712 {
+    string private constant MESSAGE_TYPE = "StakeMessage(string message)";
+
+    /* EVENTS */
+
+    event StakerApproved(address indexed staker);
+
+    /* STORAGE */
+
+    /// @inheritdoc ISignedSnapshotStakingPool
+    string public message;
+    /// @inheritdoc ISignedSnapshotStakingPool
+    mapping(address => bool) public isApprovedStaker;
+
+    /* CONSTRUCTOR */
+
+    /// @param eip712Name Name of the EIP712 signing domain
+    /// @param eip712Version Current major version of the EIP712 signing domain
+    /// @param stakeMessage The message to sign when staking
+    /// @param name Name of the staked token
+    /// @param symbol Symbol of the staked token
+    /// @param rewardToken Instance of the reward token
+    /// @param stakeToken Instance of the stake token
+    /// @param distributor Address of the distributor
+    /// @param snapshotDelay The minimum amount of time between snapshots
+    constructor(
+        string memory eip712Name,
+        string memory eip712Version,
+        string memory stakeMessage,
+        string memory name,
+        string memory symbol,
+        IERC20 rewardToken,
+        IERC20 stakeToken,
+        address distributor,
+        uint256 snapshotDelay
+    )
+        EIP712(eip712Name, eip712Version)
+        SnapshotStakingPool(name, symbol, rewardToken, stakeToken, distributor, snapshotDelay)
+    {
+        message = stakeMessage;
+    }
+
+    /* STAKER FUNCTIONS */
+
+    /// @inheritdoc ISignedSnapshotStakingPool
+    function stake(uint256 _amount) external override(SnapshotStakingPool, ISignedSnapshotStakingPool) nonReentrant {
+        require(isApprovedStaker[msg.sender], "Not approved staker");
+        _stake(msg.sender, _amount);
+    }
+
+    /// @inheritdoc ISignedSnapshotStakingPool
+    function stake(uint256 _amount, bytes calldata _signature) external nonReentrant {
+        _approveStaker(msg.sender, _signature);
+        _stake(msg.sender, _amount);
+    }
+
+    /// @inheritdoc ISignedSnapshotStakingPool
+    function approveStaker(bytes calldata _signature) external {
+        _approveStaker(msg.sender, _signature);
+    }
+
+    /* VIEW FUNCTIONS */
+
+    /// @inheritdoc ISignedSnapshotStakingPool
+    function getStakeSignatureDigest() public view returns (bytes32) {
+        return _hashTypedDataV4(
+            keccak256(
+                abi.encode(
+                    keccak256(abi.encodePacked(MESSAGE_TYPE)),
+                    keccak256(bytes(message))
+                )
+            )
+        );
+    }
+
+    /* INTERNAL FUNCTIONS */
+
+    /// @dev Approve the `staker` if the `signature` is valid
+    /// @param staker The staker to approve
+    /// @param signature The signature to verify
+    function _approveStaker(address staker, bytes calldata signature) internal {
+        require(SignatureChecker.isValidSignatureNow(staker, getStakeSignatureDigest(), signature), "Invalid signature");
+        isApprovedStaker[staker] = true;
+        emit StakerApproved(staker);
+    }
+}