Merge branch 'governor-dvp-poc' into dvp-actions-poc

Author: godzillaba

src/L2ArbitrumToken.sol

@@ -44,47 +44,11 @@ contract L2ArbitrumToken is
     /// @notice The time at which the next mint is allowed - timestamp
     uint256 public nextMint;
 
-    /// @dev History of the total amount of delegated tokens
-    ///      The initial value is an estimate of the total delegation at the time of upgrade proposal creation.
-    ///      Another proposal can be made later to update this value if needed.
-    Checkpoints.History private _totalDelegationHistory;
-
-    /// @notice Called at proposal #1
-    /// @param  initialTotalDelegation The initial total delegation at the time of upgrade proposal creation.
-    ///         This is an estimate since it is chosen at proposal creation time and not effective until the proposal is executed.
-    function postUpgradeInit1(uint256 initialTotalDelegation) external onlyOwner {
-        _totalDelegationHistory.push(initialTotalDelegation);
-    }
-
-    /// @notice Called at proposal #2
-    /// @param  initialEstimationErrorAdjustment The amount the initialTotalDelegation was off by, negated. This is added to the current total delegation.
-    function postUpgradeInit2(int256 initialEstimationErrorAdjustment) external onlyOwner {
-        _totalDelegationHistory.push(
-            uint256(int256(_totalDelegationHistory.latest()) + initialEstimationErrorAdjustment)
-        );
-    }
-
-    /// @notice Get the current total delegation
-    /// @return The current total delegation
-    function getTotalDelegation() 
-        external
-        view
-        returns (uint256)
-    {
-        return _totalDelegationHistory.latest();
-    }
-
-    /// @notice Get the total delegation at a specific block number
-    ///         If the blockNumber is prior to the first checkpoint, returns 0
-    /// @param blockNumber The block number to get the total delegation at
-    /// @return The total delegation at the given block number
-    function getTotalDelegationAt(uint256 blockNumber)
-        external
-        view
-        returns (uint256)
-    {
-        return _totalDelegationHistory.getAtBlock(blockNumber);
-    }
+    /// @dev History of the change in total amount of delegated tokens
+    ///      Tracks the delta between total delegation at a given block and the anchor
+    ///      The anchor is set via setTotalDelegationAnchor as a standalone one-time operation
+    Checkpoints.History private _totalDelegationDeltaHistory;
+    uint256 private _totalDelegationAnchor;
 
     constructor() {
         _disableInitializers();
@@ -114,6 +78,11 @@ contract L2ArbitrumToken is
         _transferOwnership(_owner);
     }
 
+    function setTotalDelegationAnchor(uint256 totalDelegationAnchor) external onlyOwner {
+        require(_totalDelegationAnchor == 0, "ARB: ANCHOR_ALREADY_SET");
+        _totalDelegationAnchor = totalDelegationAnchor;
+    }
+
     /// @notice Allows the owner to mint new tokens
     /// @dev    Only allows minting below an inflation cap.
     ///         Set to once per year, and a maximum of 2%.
@@ -129,12 +98,48 @@ contract L2ArbitrumToken is
         _mint(recipient, amount);
     }
 
+    /// @notice Get the current total delegation
+    /// @dev    If the anchor is unset, returns 0
+    /// @return The current total delegation
+    function getTotalDelegation() external view returns (uint256) {
+        uint256 __totalDelegationAnchor = _totalDelegationAnchor;
+        if (__totalDelegationAnchor == 0) {
+            return 0;
+        }
+        return _adjustByAnchor(_totalDelegationDeltaHistory.latest(), __totalDelegationAnchor);
+    }
+
+    /// @notice Get the total delegation at a specific block number
+    /// @dev    If the anchor is unset, or the block number is before the first checkpoint, returns 0
+    /// @param  blockNumber The block number to get the total delegation at
+    /// @return The total delegation at the given block number
+    function getTotalDelegationAt(uint256 blockNumber) external view returns (uint256) {
+        uint256 __totalDelegationAnchor = _totalDelegationAnchor;
+        if (
+            __totalDelegationAnchor == 0
+                || blockNumber < _totalDelegationDeltaHistory._checkpoints[0]._blockNumber
+        ) {
+            return 0;
+        }
+        return _adjustByAnchor(
+            _totalDelegationDeltaHistory.getAtBlock(blockNumber), __totalDelegationAnchor
+        );
+    }
 
-    function _updateDelegationHistory(
-        address fromDelegate,
-        address toDelegate,
-        uint256 amount
-    ) internal {
+    /// @dev Helper function to adjust a delegation delta checkpoint return value by an anchor
+    ///      The checkpoint return value is stored as a uint224, but we treat it as a signed int224.
+    ///      This is why the casting is a bit complex.
+    function _adjustByAnchor(uint256 checkpointReturnValue, uint256 anchor)
+        internal
+        pure
+        returns (uint256)
+    {
+        return uint256(int224(uint224(checkpointReturnValue)) + int256(anchor));
+    }
+
+    function _updateDelegationHistory(address fromDelegate, address toDelegate, uint256 amount)
+        internal
+    {
         if (fromDelegate != toDelegate) {
             int256 delta = 0;
             if (fromDelegate != address(0)) {
@@ -144,32 +149,23 @@ contract L2ArbitrumToken is
                 delta += int256(amount);
             }
             if (delta != 0) {
-                _totalDelegationHistory.push(
-                    uint256(int256(_totalDelegationHistory.latest()) + delta)
-                );
+                int224 latestDelta = int224(uint224(_totalDelegationDeltaHistory.latest()));
+                _totalDelegationDeltaHistory.push(uint256(latestDelta + delta));
             }
         }
     }
 
     function _delegate(address delegator, address delegatee) internal virtual override {
         super._delegate(delegator, delegatee);
-        _updateDelegationHistory(
-            delegates(delegator),
-            delegatee,
-            balanceOf(delegator)
-        );
+        _updateDelegationHistory(delegates(delegator), delegatee, balanceOf(delegator));
     }
 
     function _afterTokenTransfer(address from, address to, uint256 amount)
         internal
         override(ERC20Upgradeable, ERC20VotesUpgradeable)
     {
         super._afterTokenTransfer(from, to, amount);
-        _updateDelegationHistory(
-            delegates(from),
-            delegates(to),
-            amount
-        );
+        _updateDelegationHistory(delegates(from), delegates(to), amount);
     }
 
     function _mint(address to, uint256 amount)