From d215bbb236560b3f34c445c353b5665b588c1d66 Mon Sep 17 00:00:00 2001
From: JK <jk@fantom.foundation>
Date: Thu, 7 Nov 2024 15:41:34 +0100
Subject: [PATCH] Add deactivation procedure for minAverageUptime

---
 contracts/sfc/ConstantsManager.sol   | 12 +++++++-----
 contracts/sfc/NetworkInitializer.sol |  4 ++--
 contracts/sfc/SFC.sol                | 21 +++++++++++++++++----
 3 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/contracts/sfc/ConstantsManager.sol b/contracts/sfc/ConstantsManager.sol
index 0f15c2a..b3fabcd 100644
--- a/contracts/sfc/ConstantsManager.sol
+++ b/contracts/sfc/ConstantsManager.sol
@@ -29,10 +29,12 @@ contract ConstantsManager is Ownable {
     uint256 public targetGasPowerPerSecond;
     uint256 public gasPriceBalancingCounterweight;
 
-    // the number of epochs for counting the average uptime of validators
-    uint32 public averageUptimeEpochsWindow;
+    // Epoch threshold for stop counting alive epochs (avoid diminishing impact of new uptimes).
+    // Is also the minimum number of epochs necessary for deactivation of offline validators.
+    uint32 public averageUptimeEpochsThreshold;
 
-    // minimum average uptime
+    // Minimum average uptime in Q1.30 format; acceptable bounds [0,0.9]
+    // Zero to disable validators deactivation by this metric.
     uint32 public minAverageUptime;
 
     /**
@@ -160,14 +162,14 @@ contract ConstantsManager is Ownable {
         gasPriceBalancingCounterweight = v;
     }
 
-    function updateAverageUptimeEpochsWindow(uint32 v) external virtual onlyOwner {
+    function updateAverageUptimeEpochsThreshold(uint32 v) external virtual onlyOwner {
         if (v < 10) {
             revert ValueTooSmall();
         }
         if (v > 87600) {
             revert ValueTooLarge();
         }
-        averageUptimeEpochsWindow = v;
+        averageUptimeEpochsThreshold = v;
     }
 
     function updateMinAverageUptime(uint32 v) external virtual onlyOwner {
diff --git a/contracts/sfc/NetworkInitializer.sol b/contracts/sfc/NetworkInitializer.sol
index 92d4f8f..4763239 100644
--- a/contracts/sfc/NetworkInitializer.sol
+++ b/contracts/sfc/NetworkInitializer.sol
@@ -37,8 +37,8 @@ contract NetworkInitializer {
         consts.updateOfflinePenaltyThresholdBlocksNum(1000);
         consts.updateTargetGasPowerPerSecond(2000000);
         consts.updateGasPriceBalancingCounterweight(3600);
-        consts.updateAverageUptimeEpochsWindow(20);
-        consts.updateMinAverageUptime(0);
+        consts.updateAverageUptimeEpochsThreshold(100);
+        consts.updateMinAverageUptime(0); // check disabled by default
         consts.transferOwnership(_owner);
 
         ISFC(_sfc).initialize(sealedEpoch, totalSupply, _auth, address(consts), _owner);
diff --git a/contracts/sfc/SFC.sol b/contracts/sfc/SFC.sol
index 1e29c4c..9069d47 100644
--- a/contracts/sfc/SFC.sol
+++ b/contracts/sfc/SFC.sol
@@ -17,6 +17,7 @@ contract SFC is Initializable, Ownable, Version {
     uint256 internal constant OK_STATUS = 0;
     uint256 internal constant WITHDRAWN_BIT = 1;
     uint256 internal constant OFFLINE_BIT = 1 << 3;
+    uint256 internal constant OFFLINE_AVG_BIT = 1 << 4;
     uint256 internal constant DOUBLESIGN_BIT = 1 << 7;
     uint256 internal constant CHEATER_MASK = DOUBLESIGN_BIT;
 
@@ -929,16 +930,28 @@ contract SFC is Initializable, Ownable, Version {
     ) internal {
         for (uint256 i = 0; i < validatorIDs.length; i++) {
             uint256 validatorID = validatorIDs[i];
+            // compute normalised uptime as a percentage in the Q1.30 fixed-point format
             uint256 normalisedUptime = (uptimes[i] * (1 << 30)) / epochDuration;
             if (normalisedUptime > 1 << 30) {
                 normalisedUptime = 1 << 30;
             }
-            AverageUptime memory previousAverage = prevSnapshot.averageUptime[validatorID];
-            snapshot.averageUptime[validatorID] = _addElementIntoAverageUptime(normalisedUptime, previousAverage);
+            AverageUptime memory previous = prevSnapshot.averageUptime[validatorID];
+            AverageUptime memory current = _addElementIntoAverageUptime(uint32(normalisedUptime), previous);
+            snapshot.averageUptime[validatorID] = current;
+
+            // remove validator if average uptime drops below min average uptime
+            // (by setting minAverageUptime to zero, this check is ignored)
+            if (current.averageUptime < c.minAverageUptime() && current.epochs >= c.averageUptimeEpochsThreshold()) {
+                _setValidatorDeactivated(validatorID, OFFLINE_AVG_BIT);
+                _syncValidator(validatorID, false);
+            }
         }
     }
 
-    function _addElementIntoAverageUptime(uint32 newValue, AverageUptime memory prev) private returns (AverageUptime memory) {
+    function _addElementIntoAverageUptime(
+        uint32 newValue,
+        AverageUptime memory prev
+    ) private view returns (AverageUptime memory) {
         AverageUptime memory cur;
         if (prev.epochs == 0) {
             // the only element for the average
@@ -963,7 +976,7 @@ contract SFC is Initializable, Ownable, Version {
         if (cur.averageUptime > 1 << 30) {
             cur.averageUptime = 1 << 30;
         }
-        if (prev.epochs < c.averageUptimeEpochsWindow()) {
+        if (prev.epochs < c.averageUptimeEpochsThreshold()) {
             cur.epochs = prev.epochs + 1;
         } else {
             cur.epochs = prev.epochs;