fix: ensure getAverageInterval and getMedianInterval do not mutate intervals state

Author: Grotax

src/FeedIo/Reader/Result/UpdateStats.php

@@ -133,23 +133,24 @@ public function getMaxInterval(): int
      */
     public function getAverageInterval(): int
     {
-        sort($this->intervals);
+        $intervals = $this->intervals;
+        sort($intervals);
 
-        $count = count($this->intervals);
+        $count = count($intervals);
         if ($count === 0) {
             return 0;
         }
 
         // some feeds could have very old historic
         // articles so eliminate them with statistic
-        $q1 = $this->intervals[(int) floor($count * 0.25)];
-        $q3 = $this->intervals[(int) floor($count * 0.75)];
+        $q1 = $intervals[(int) floor($count * 0.25)];
+        $q3 = $intervals[(int) floor($count * 0.75)];
         $iqr = $q3 - $q1;
 
         $lower_bound = $q1 - 1.5 * $iqr;
         $upper_bound = $q3 + 1.5 * $iqr;
 
-        $result = array_filter($this->intervals, function($value) use ($lower_bound, $upper_bound) {
+        $result = array_filter($intervals, function($value) use ($lower_bound, $upper_bound) {
             return $value >= $lower_bound && $value <= $upper_bound;
         });
 
@@ -163,19 +164,20 @@ public function getAverageInterval(): int
      */
     public function getMedianInterval(): int
     {
-        sort($this->intervals);
+        $intervals = $this->intervals;
+        sort($intervals);
 
-        $count = count($this->intervals);
+        $count = count($intervals);
         if ($count === 0) {
             return 0;
         }
 
         $num = (int) floor($count / 2);
 
         if ($count % 2 === 0) {
-            return intval(floor(($this->intervals[$num - 1] + $this->intervals[$num]) / 2));
+            return intval(floor(($intervals[$num - 1] + $intervals[$num]) / 2));
         } else {
-            return $this->intervals[$num];
+            return $intervals[$num];
         }
     }
 

tests/FeedIo/Reader/Result/UpdateStatsTest.php

@@ -426,6 +426,57 @@ public function testAverageIntervalWhenAllValuesFiltered()
         $this->assertGreaterThanOrEqual(0, $average);
     }
 
+    /**
+     * Test that getAverageInterval and getMedianInterval don't mutate $this->intervals
+     * This ensures calling these methods doesn't have side effects on other methods
+     */
+    public function testIntervalMethodsDoNotMutateState()
+    {
+        $feed = new Feed();
+        $feed->setLastModified(new \DateTime('-1 day'));
+        
+        $dates = [
+            '-5 days',
+            '-1 day',
+            '-3 days',
+            '-2 days',
+            '-4 days',
+        ];
+        
+        foreach ($dates as $date) {
+            $item = new Feed\Item();
+            $item->setLastModified(new \DateTime($date));
+            $feed->add($item);
+        }
+
+        $stats = new UpdateStats($feed);
+        
+        // Get the original intervals (should be in chronological order based on how they're computed)
+        $originalIntervals = $stats->getIntervals();
+        
+        // Call methods that need to sort the intervals
+        $average = $stats->getAverageInterval();
+        $median = $stats->getMedianInterval();
+        
+        // Get intervals again - they should still be in the original order
+        $intervalsAfter = $stats->getIntervals();
+        
+        $this->assertEquals($originalIntervals, $intervalsAfter, 
+            'Calling getAverageInterval() and getMedianInterval() should not mutate the intervals array');
+        
+        // Call again to verify no mutation on subsequent calls
+        $average2 = $stats->getAverageInterval();
+        $median2 = $stats->getMedianInterval();
+        $intervalsAfter2 = $stats->getIntervals();
+        
+        $this->assertEquals($originalIntervals, $intervalsAfter2,
+            'Multiple calls to statistical methods should not mutate the intervals array');
+        
+        // Results should be consistent
+        $this->assertEquals($average, $average2);
+        $this->assertEquals($median, $median2);
+    }
+
     private function getDates(): array
     {
         return [