From cb7d8b7b5e5e33ebde37bdb0466d95af7207b655 Mon Sep 17 00:00:00 2001
From: Boog900 <54e72d8a-345f-4599-bd90-c6b9bc7d0ec5@aleeas.com>
Date: Tue, 24 Oct 2023 23:35:24 +0100
Subject: [PATCH] fix cumulative diff calculations + sort timestamps before
 getting median

we were not accounting for the genesis blocks difficulty of 1.
---
 consensus/src/context/difficulty.rs | 36 ++++++++++++++++-------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/consensus/src/context/difficulty.rs b/consensus/src/context/difficulty.rs
index d3d90d1..6d28df5 100644
--- a/consensus/src/context/difficulty.rs
+++ b/consensus/src/context/difficulty.rs
@@ -170,28 +170,32 @@ impl DifficultyCache {
     ///
     /// Will return [`None`] if there aren't enough blocks.
     pub fn median_timestamp(&self, numb_blocks: usize) -> Option<u64> {
-        let timestamps = if self.last_accounted_height + 1 == u64::try_from(numb_blocks).unwrap() {
-            // if the chain height is equal to `numb_blocks` add the genesis block.
-            // otherwise if the chain height is less than `numb_blocks` None is returned
-            // and if its more than it would be excluded from calculations.
-            let mut timestamps = self.timestamps.clone();
-            // all genesis blocks have a timestamp of 0.
-            // https://cuprate.github.io/monero-book/consensus_rules/genesis_block.html
-            timestamps.push_front(0);
-            timestamps.into()
-        } else {
-            self.timestamps
-                .range(self.timestamps.len().checked_sub(numb_blocks)?..)
-                .copied()
-                .collect::<Vec<_>>()
-        };
+        let mut timestamps =
+            if self.last_accounted_height + 1 == u64::try_from(numb_blocks).unwrap() {
+                // if the chain height is equal to `numb_blocks` add the genesis block.
+                // otherwise if the chain height is less than `numb_blocks` None is returned
+                // and if its more than it would be excluded from calculations.
+                let mut timestamps = self.timestamps.clone();
+                // all genesis blocks have a timestamp of 0.
+                // https://cuprate.github.io/monero-book/consensus_rules/genesis_block.html
+                timestamps.push_front(0);
+                timestamps.into()
+            } else {
+                self.timestamps
+                    .range(self.timestamps.len().checked_sub(numb_blocks)?..)
+                    .copied()
+                    .collect::<Vec<_>>()
+            };
+        timestamps.sort_unstable();
+        debug_assert_eq!(timestamps.len(), numb_blocks);
 
         Some(median(&timestamps))
     }
 
     /// Returns the cumulative difficulty of the chain.
     pub fn cumulative_difficulty(&self) -> u128 {
-        self.cumulative_difficulties.back().copied().unwrap_or(0)
+        // the genesis block has a difficulty of 1
+        self.cumulative_difficulties.back().copied().unwrap_or(1)
     }
 
     pub fn top_block_timestamp(&self) -> Option<u64> {