feat: optimistic roots smart contracts

packages/deployments/contracts/contracts/messaging/connectors/SpokeConnector.sol

@@ -11,6 +11,7 @@ import {TypeCasts} from "../../shared/libraries/TypeCasts.sol";
 import {MerkleLib} from "../libraries/MerkleLib.sol";
 import {Message} from "../libraries/Message.sol";
 import {RateLimited} from "../libraries/RateLimited.sol";
+import {SnapshotId} from "../libraries/SnapshotId.sol";
 
 import {MerkleTreeManager} from "../MerkleTreeManager.sol";
 import {WatcherClient} from "../WatcherClient.sol";
@@ -54,6 +55,8 @@ abstract contract SpokeConnector is Connector, ConnectorManager, WatcherClient,
 
   event DelayBlocksUpdated(uint256 indexed updated, address caller);
 
+  event SnapshotRootSaved(uint256 indexed snapshotId, bytes32 indexed root, uint256 indexed count);
+
   /**
    * @notice Emitted when funds are withdrawn by the admin
    * @dev See comments in `withdrawFunds`
@@ -161,6 +164,11 @@ abstract contract SpokeConnector is Connector, ConnectorManager, WatcherClient,
    */
   mapping(bytes32 => MessageStatus) public messages;
 
+  /**
+   * @notice Mapping of the snapshot roots for a specific index. Used for data availability for off-chain scripts
+   */
+  mapping(uint256 => bytes32) public snapshotRoots;
+
   // ============ Modifiers ============
 
   modifier onlyAllowlistedSender() {
@@ -323,6 +331,9 @@ abstract contract SpokeConnector is Connector, ConnectorManager, WatcherClient,
    * @dev The root of this tree will eventually be dispatched to mainnet via `send`. On mainnet (the "hub"),
    * it will be combined into a single aggregate root by RootManager (along with outbound roots from other
    * chains). This aggregate root will be redistributed to all destination chains.
+   * @dev This function is also in charge of saving the snapshot root when needed. If the message being added to the
+   * tree is the first of the current period this means the last snapshot finished and its root must be saved. The saving
+   * happens before adding the new message to the tree.
    *
    * NOTE: okay to leave dispatch operational when paused as pause is designed for crosschain interactions
    */
@@ -331,6 +342,15 @@ abstract contract SpokeConnector is Connector, ConnectorManager, WatcherClient,
     bytes32 _recipientAddress,
     bytes memory _messageBody
   ) external onlyAllowlistedSender returns (bytes32, bytes memory) {
+    // Before inserting the new message to the tree we need to check if the last snapshot root must be calculated and set.
+    uint256 _lastCompletedSnapshotId = SnapshotId.getLastCompletedSnapshotId();
+    if (snapshotRoots[_lastCompletedSnapshotId] == 0) {
+      // Saves current tree root as last snapshot root before adding the new message.
+      bytes32 _currentRoot = MERKLE.root();
+      snapshotRoots[_lastCompletedSnapshotId] = _currentRoot;
+      emit SnapshotRootSaved(_lastCompletedSnapshotId, _currentRoot, MERKLE.count());
+    }
+
     // Get the next nonce for the destination domain, then increment it.
     uint32 _nonce = nonces[_destinationDomain]++;
 
@@ -432,6 +452,15 @@ abstract contract SpokeConnector is Connector, ConnectorManager, WatcherClient,
     }
   }
 
+  /**
+   * @notice This function gets the last completed snapshot id
+   * @dev The value is calculated through an internal function to reuse code and save gas
+   * @return _lastCompletedSnapshotId The last completed snapshot id
+   */
+  function getLastCompletedSnapshotId() external view returns (uint256 _lastCompletedSnapshotId) {
+    _lastCompletedSnapshotId = SnapshotId.getLastCompletedSnapshotId();
+  }
+
   // ============ Private Functions ============
 
   /**

packages/deployments/contracts/contracts/messaging/libraries/SnapshotId.sol

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity 0.8.17;
+
+/**
+ * @title SnapshotId library
+ * @notice A library to be used in spoke connector and root manager to calculates the current snapshot id
+ */
+library SnapshotId {
+  /**
+   * @notice Duration of the snapshot
+   * @dev Off-chain agents could change the effective snapshot length by skipping snapshots. This is the
+   * smallest unit of snapshot duration, not just the only option.
+   */
+  uint256 public constant SNAPSHOT_DURATION = 30 minutes;
+
+  /**
+   * @notice This function calculates the last completed snapshot id
+   * @return _lastCompletedSnapshotId The last completed snapshot id
+   */
+  function getLastCompletedSnapshotId() internal view returns (uint256 _lastCompletedSnapshotId) {
+    unchecked {
+      _lastCompletedSnapshotId = block.timestamp / SNAPSHOT_DURATION;
+    }
+  }
+
+  /**
+   * @notice Get the snapshot duration
+   * @return _snapshotDuration The snapshot duration
+   */
+  function getSnapshotDuration() internal pure returns (uint256 _snapshotDuration) {
+    _snapshotDuration = SNAPSHOT_DURATION;
+  }
+}

packages/deployments/contracts/contracts_forge/messaging/PingPong.t.sol

@@ -157,10 +157,18 @@ contract PingPong is ConnectorHelper {
 
     MockSpokeConnector(payable(_destinationConnectors.spoke)).setUpdatesAggregate(true);
 
+    // enroll this as approved watcher to activate slowmode
+    WatcherManager(_watcherManager).addWatcher(address(this));
+    // check setup
+    assertTrue(WatcherManager(_watcherManager).isWatcher(address(this)));
+
     // configure root manager with connectors
     RootManager(_rootManager).addConnector(_originDomain, _originConnectors.hub);
     RootManager(_rootManager).addConnector(_destinationDomain, _destinationConnectors.hub);
+    // set root manager to slow mode
+    RootManager(_rootManager).activateSlowMode();
     // check setup
+    assertFalse(RootManager(_rootManager).optimisticMode());
     assertEq(RootManager(_rootManager).connectors(0), _originConnectors.hub);
     assertEq(RootManager(_rootManager).connectors(1), _destinationConnectors.hub);
     assertEq(RootManager(_rootManager).domains(0), _originDomain);
@@ -317,11 +325,7 @@ contract PingPong is ConnectorHelper {
   }
 
   // Process a given aggregateRoot on a given spoke.
-  function utils_processAggregateRootAndAssert(
-    address connector,
-    address amb,
-    bytes32 aggregateRoot
-  ) public {
+  function utils_processAggregateRootAndAssert(address connector, address amb, bytes32 aggregateRoot) public {
     // Expect MessageProcessed on the target spoke.
     vm.expectEmit(true, true, true, true);
     emit MessageProcessed(abi.encode(aggregateRoot), amb);