fix: prevent metric charts from freezing on page navigation (#7848)

bootstrap/helpers/shared.php

@@ -3416,3 +3416,81 @@ function verifyPasswordConfirmation(mixed $password, ?Livewire\Component $compon
 
     return true;
 }
+
+/**
+ * Downsample metrics using the Largest-Triangle-Three-Buckets (LTTB) algorithm.
+ * This preserves the visual shape of the data better than simple averaging.
+ *
+ * @param  array  $data  Array of [timestamp, value] pairs
+ * @param  int  $threshold  Target number of points
+ * @return array Downsampled data
+ */
+function downsampleLTTB(array $data, int $threshold): array
+{
+    $dataLength = count($data);
+
+    // Return unchanged if threshold >= data length, or if threshold <= 2
+    // (threshold <= 2 would cause division by zero in bucket calculation)
+    if ($threshold >= $dataLength || $threshold <= 2) {
+        return $data;
+    }
+
+    $sampled = [];
+    $sampled[] = $data[0]; // Always keep first point
+
+    $bucketSize = ($dataLength - 2) / ($threshold - 2);
+
+    $a = 0; // Index of previous selected point
+
+    for ($i = 0; $i < $threshold - 2; $i++) {
+        // Calculate bucket range
+        $bucketStart = (int) floor(($i + 1) * $bucketSize) + 1;
+        $bucketEnd = (int) floor(($i + 2) * $bucketSize) + 1;
+        $bucketEnd = min($bucketEnd, $dataLength - 1);
+
+        // Calculate average point for next bucket (used as reference)
+        $nextBucketStart = (int) floor(($i + 2) * $bucketSize) + 1;
+        $nextBucketEnd = (int) floor(($i + 3) * $bucketSize) + 1;
+        $nextBucketEnd = min($nextBucketEnd, $dataLength - 1);
+
+        $avgX = 0;
+        $avgY = 0;
+        $nextBucketCount = $nextBucketEnd - $nextBucketStart + 1;
+
+        if ($nextBucketCount > 0) {
+            for ($j = $nextBucketStart; $j <= $nextBucketEnd; $j++) {
+                $avgX += $data[$j][0];
+                $avgY += $data[$j][1];
+            }
+            $avgX /= $nextBucketCount;
+            $avgY /= $nextBucketCount;
+        }
+
+        // Find point in current bucket with largest triangle area
+        $maxArea = -1;
+        $maxAreaIndex = $bucketStart;
+
+        $pointAX = $data[$a][0];
+        $pointAY = $data[$a][1];
+
+        for ($j = $bucketStart; $j <= $bucketEnd; $j++) {
+            // Triangle area calculation
+            $area = abs(
+                ($pointAX - $avgX) * ($data[$j][1] - $pointAY) -
+                ($pointAX - $data[$j][0]) * ($avgY - $pointAY)
+            ) * 0.5;
+
+            if ($area > $maxArea) {
+                $maxArea = $area;
+                $maxAreaIndex = $j;
+            }
+        }
+
+        $sampled[] = $data[$maxAreaIndex];
+        $a = $maxAreaIndex;
+    }
+
+    $sampled[] = $data[$dataLength - 1]; // Always keep last point
+
+    return $sampled;
+}