From 224eca774092511f6b003bcf7380debd0eb8d1d7 Mon Sep 17 00:00:00 2001
From: Jordan Schalm <jordan@dapperlabs.com>
Date: Sat, 11 Nov 2023 09:52:33 -0800
Subject: [PATCH] add precondition that ref epoch in the past

guarantees time computation doesn't underflow
---
 contracts/epochs/FlowEpoch.cdc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/contracts/epochs/FlowEpoch.cdc b/contracts/epochs/FlowEpoch.cdc
index 10ff8de5e..5e91ee898 100644
--- a/contracts/epochs/FlowEpoch.cdc
+++ b/contracts/epochs/FlowEpoch.cdc
@@ -375,6 +375,9 @@ pub contract FlowEpoch {
         }
 
         pub fun updateEpochTimingConfig(_ newConfig: EpochTimingConfig) {
+            pre {
+                FlowEpoch.currentEpochCounter >= newConfig.refCounter: "Reference epoch must be before next epoch"
+            }
             FlowEpoch.account.load<EpochTimingConfig>(from: /storage/flowEpochTimingConfig)
             FlowEpoch.account.save(newConfig, to: /storage/flowEpochTimingConfig)
         }