feat: Add distribution data history and rebate on distribution (#382)

script/DeployBase.s.sol

@@ -168,7 +168,8 @@ abstract contract DeployBase is Script {
             CSFeeDistributor feeDistributorImpl = new CSFeeDistributor({
                 stETH: locator.lido(),
                 accounting: address(accounting),
-                oracle: address(oracle)
+                oracle: address(oracle),
+                rebateRecipient: config.aragonAgent
             });
             feeDistributor = CSFeeDistributor(
                 _deployProxy(config.proxyAdmin, address(feeDistributorImpl))

script/DeployImplementationsBase.s.sol

@@ -62,7 +62,8 @@ abstract contract DeployImplementationsBase is DeployBase {
             CSFeeDistributor feeDistributorImpl = new CSFeeDistributor({
                 stETH: locator.lido(),
                 accounting: address(accounting),
-                oracle: address(oracle)
+                oracle: address(oracle),
+                rebateRecipient: config.aragonAgent
             });
 
             verifier = new CSVerifier({

src/CSFeeDistributor.sol

@@ -24,14 +24,15 @@ contract CSFeeDistributor is
     IStETH public immutable STETH;
     address public immutable ACCOUNTING;
     address public immutable ORACLE;
+    address public immutable REBATE_RECIPIENT;
 
-    /// @notice Merkle Tree root
+    /// @notice The latest Merkle Tree root
     bytes32 public treeRoot;
 
-    /// @notice CID of the published Merkle tree
+    /// @notice CID of the last published Merkle tree
     string public treeCid;
 
-    /// @notice CID of the file with log of the last frame reported
+    /// @notice CID of the file with log for the last frame reported
     string public logCid;
 
     /// @notice Amount of stETH shares sent to the Accounting in favor of the NO
@@ -40,14 +41,27 @@ contract CSFeeDistributor is
     /// @notice Total Amount of stETH shares available for claiming by NOs
     uint256 public totalClaimableShares;
 
-    constructor(address stETH, address accounting, address oracle) {
+    /// @notice Array of the distribution data history
+    mapping(uint256 => DistributionData) internal _distributionDataHistory;
+
+    /// @notice The number of _distributionDataHistory records
+    uint256 public distributionDataHistoryCount;
+
+    constructor(
+        address stETH,
+        address accounting,
+        address oracle,
+        address rebateRecipient
+    ) {
         if (accounting == address(0)) revert ZeroAccountingAddress();
         if (oracle == address(0)) revert ZeroOracleAddress();
         if (stETH == address(0)) revert ZeroStEthAddress();
+        if (rebateRecipient == address(0)) revert ZeroRebateRecipientAddress();
 
         ACCOUNTING = accounting;
         STETH = IStETH(stETH);
         ORACLE = oracle;
+        REBATE_RECIPIENT = rebateRecipient;
 
         _disableInitializers();
     }
@@ -90,11 +104,14 @@ contract CSFeeDistributor is
         bytes32 _treeRoot,
         string calldata _treeCid,
         string calldata _logCid,
-        uint256 distributed
+        uint256 distributed,
+        uint256 rebate,
+        uint256 refSlot
     ) external {
         if (msg.sender != ORACLE) revert NotOracle();
         if (
-            totalClaimableShares + distributed > STETH.sharesOf(address(this))
+            totalClaimableShares + distributed + rebate >
+            STETH.sharesOf(address(this))
         ) {
             revert InvalidShares();
         }
@@ -123,6 +140,11 @@ contract CSFeeDistributor is
 
         emit ModuleFeeDistributed(distributed);
 
+        if (rebate > 0) {
+            STETH.transferShares(REBATE_RECIPIENT, rebate);
+            emit RebateTransferred(rebate);
+        }
+
         // NOTE: Make sure off-chain tooling provides a distinct CID of a log even for empty reports, e.g. by mixing
         // in a frame identifier such as reference slot to a file.
         if (bytes(_logCid).length == 0) revert InvalidLogCID();
@@ -131,6 +153,21 @@ contract CSFeeDistributor is
 
         logCid = _logCid;
         emit DistributionLogUpdated(_logCid);
+
+        _distributionDataHistory[
+            distributionDataHistoryCount
+        ] = DistributionData({
+            refSlot: refSlot,
+            treeRoot: treeRoot,
+            treeCid: treeCid,
+            logCid: _logCid,
+            distributed: distributed,
+            rebate: rebate
+        });
+
+        unchecked {
+            ++distributionDataHistoryCount;
+        }
     }
 
     /// @inheritdoc AssetRecoverer
@@ -147,6 +184,13 @@ contract CSFeeDistributor is
         return STETH.sharesOf(address(this)) - totalClaimableShares;
     }
 
+    /// @inheritdoc ICSFeeDistributor
+    function getHistoricalDistributionData(
+        uint256 index
+    ) external view returns (DistributionData memory) {
+        return _distributionDataHistory[index];
+    }
+
     /// @inheritdoc ICSFeeDistributor
     function getFeesToDistribute(
         uint256 nodeOperatorId,

src/CSFeeOracle.sol

@@ -138,12 +138,14 @@ contract CSFeeOracle is
     }
 
     function _handleConsensusReportData(ReportData calldata data) internal {
-        feeDistributor.processOracleReport(
-            data.treeRoot,
-            data.treeCid,
-            data.logCid,
-            data.distributed
-        );
+        feeDistributor.processOracleReport({
+            _treeRoot: data.treeRoot,
+            _treeCid: data.treeCid,
+            _logCid: data.logCid,
+            distributed: data.distributed,
+            rebate: data.rebate,
+            refSlot: data.refSlot
+        });
     }
 
     function _checkMsgSenderIsAllowedToSubmitData() internal view {

src/interfaces/ICSFeeDistributor.sol

@@ -7,6 +7,24 @@ import { IStETH } from "./IStETH.sol";
 pragma solidity 0.8.24;
 
 interface ICSFeeDistributor is IAssetRecovererLib {
+    struct DistributionData {
+        /// @dev Reference slot for which the report was calculated. If the slot
+        /// contains a block, the state being reported should include all state
+        /// changes resulting from that block. The epoch containing the slot
+        /// should be finalized prior to calculating the report.
+        uint256 refSlot;
+        /// @notice Merkle Tree root.
+        bytes32 treeRoot;
+        /// @notice CID of the published Merkle tree.
+        string treeCid;
+        /// @notice CID of the file with log of the frame reported.
+        string logCid;
+        /// @notice Total amount of fees distributed in the report.
+        uint256 distributed;
+        /// @notice Amount of the rebate shares in the report
+        uint256 rebate;
+    }
+
     /// @dev Emitted when fees are distributed
     event OperatorFeeDistributed(
         uint256 indexed nodeOperatorId,
@@ -26,10 +44,14 @@ interface ICSFeeDistributor is IAssetRecovererLib {
     /// @dev It logs how many shares were distributed in the latest report
     event ModuleFeeDistributed(uint256 shares);
 
+    /// @dev Emitted when rebate is transferred
+    event RebateTransferred(uint256 shares);
+
     error ZeroAccountingAddress();
     error ZeroStEthAddress();
     error ZeroAdminAddress();
     error ZeroOracleAddress();
+    error ZeroRebateRecipientAddress();
     error NotAccounting();
     error NotOracle();
 
@@ -49,6 +71,8 @@ interface ICSFeeDistributor is IAssetRecovererLib {
 
     function ORACLE() external view returns (address);
 
+    function REBATE_RECIPIENT() external view returns (address);
+
     function treeRoot() external view returns (bytes32);
 
     function treeCid() external view returns (string calldata);
@@ -85,17 +109,28 @@ interface ICSFeeDistributor is IAssetRecovererLib {
     /// @param _treeRoot Root of the Merkle tree
     /// @param _treeCid an IPFS CID of the tree
     /// @param _logCid an IPFS CID of the log
+    /// @param distributed an amount of the distributed shares
+    /// @param rebate an amount of the rebate shares
+    /// @param refSlot refSlot of the report
     function processOracleReport(
         bytes32 _treeRoot,
         string calldata _treeCid,
         string calldata _logCid,
-        uint256 _distributedShares
+        uint256 distributed,
+        uint256 rebate,
+        uint256 refSlot
     ) external;
 
     /// @notice Get the Amount of stETH shares that are pending to be distributed
     /// @return pendingShares Amount shares that are pending to distribute
     function pendingSharesToDistribute() external view returns (uint256);
 
+    /// @notice Get the historical record of distribution data
+    /// @return index Historical entry index
+    function getHistoricalDistributionData(
+        uint256 index
+    ) external view returns (DistributionData memory);
+
     /// @notice Get a hash of a leaf
     /// @param nodeOperatorId ID of the Node Operator
     /// @param shares Amount of stETH shares

src/interfaces/ICSFeeOracle.sol

@@ -20,10 +20,12 @@ interface ICSFeeOracle is IAssetRecovererLib {
         bytes32 treeRoot;
         /// @notice CID of the published Merkle tree.
         string treeCid;
-        /// @notice CID of the file with log of the last frame reported.
+        /// @notice CID of the file with log of the frame reported.
         string logCid;
         /// @notice Total amount of fees distributed in the report.
         uint256 distributed;
+        /// @notice Amount of the rebate shares in the report
+        uint256 rebate;
     }
 
     /// @dev Emitted when a new fee distributor contract is set