From ac0e7b8736498f189a41bc2abcbac7f4bd265123 Mon Sep 17 00:00:00 2001
From: Dilip Kola <kdilipkola@gmail.com>
Date: Fri, 13 Dec 2024 07:28:00 +0530
Subject: [PATCH] refactor: getAggregationBucketMinute and create floorFactor
 function

---
 enterprise/reporting/util_test.go | 28 ++++++++++++++++++++++++
 enterprise/reporting/utils.go     | 36 ++++++++++++++++++++-----------
 2 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/enterprise/reporting/util_test.go b/enterprise/reporting/util_test.go
index 26df194752..1bd98540a6 100644
--- a/enterprise/reporting/util_test.go
+++ b/enterprise/reporting/util_test.go
@@ -653,6 +653,34 @@ func TestTransformMetricWithEventSamplingWithNilEventSampler(t *testing.T) {
 	require.Equal(t, sampleResponse, transformedMetric.StatusDetail.SampleResponse)
 }
 
+func TestFloorFactor(t *testing.T) {
+	tests := []struct {
+		name       string
+		intervalMs int64
+		expected   int64
+	}{
+		// Edge cases
+		{name: "Smaller than smallest factor", intervalMs: 0, expected: 1},
+		{name: "Exact match for smallest factor", intervalMs: 1, expected: 1},
+		{name: "Exact match for largest factor", intervalMs: 60, expected: 60},
+		{name: "Larger than largest factor", intervalMs: 100, expected: 60},
+
+		// Typical cases
+		{name: "Between 10 and 12", intervalMs: 11, expected: 10},
+		{name: "Between 4 and 6", intervalMs: 5, expected: 5},
+		{name: "Between 20 and 30", intervalMs: 25, expected: 20},
+		{name: "Exact match in the middle", intervalMs: 30, expected: 30},
+		{name: "Exact match at a non-boundary point", intervalMs: 12, expected: 12},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			result := floorFactor(test.intervalMs)
+			require.Equal(t, test.expected, result)
+		})
+	}
+}
+
 func TestTransformMetricWithEventSampling(t *testing.T) {
 	sampleEvent := []byte(`{"event": "2"}`)
 	sampleResponse := "sample response"
diff --git a/enterprise/reporting/utils.go b/enterprise/reporting/utils.go
index 1a416a4b39..682f088043 100644
--- a/enterprise/reporting/utils.go
+++ b/enterprise/reporting/utils.go
@@ -2,6 +2,7 @@ package reporting
 
 import (
 	"encoding/json"
+	"sort"
 	"strings"
 
 	"github.com/rudderlabs/rudder-go-kit/config"
@@ -9,27 +10,38 @@ import (
 	"github.com/rudderlabs/rudder-server/utils/types"
 )
 
+func floorFactor(intervalMs int64) int64 {
+	factors := []int64{1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60}
+
+	// Find the smallest index where factors[i] >= intervalMs
+	index := sort.Search(len(factors), func(i int) bool {
+		return factors[i] >= intervalMs
+	})
+
+	// If index is 0, intervalMs is smaller than the smallest factor
+	if index == 0 {
+		return factors[0]
+	}
+
+	// If factors[index] == intervalMs, return it directly
+	if index < len(factors) && factors[index] == intervalMs {
+		return factors[index]
+	}
+
+	// Otherwise, return the previous factor
+	return factors[index-1]
+}
+
 func getAggregationBucketMinute(timeMs, intervalMs int64) (int64, int64) {
 	// If interval is not a factor of 60, then the bucket start will not be aligned to hour start
 	// For example, if intervalMs is 7, and timeMs is 28891085 (6:05) then the bucket start will be 28891079 (5:59)
 	// and current bucket will contain the data of 2 different hourly buckets, which is should not have happened.
 	// To avoid this, we round the intervalMs to the nearest factor of 60.
 	if intervalMs <= 0 || 60%intervalMs != 0 {
-		factors := []int64{1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60}
-		closestFactor := factors[0]
-		for _, factor := range factors {
-			if factor < intervalMs {
-				closestFactor = factor
-			} else {
-				break
-			}
-		}
-		intervalMs = closestFactor
+		intervalMs = floorFactor(intervalMs)
 	}
-
 	bucketStart := timeMs - (timeMs % intervalMs)
 	bucketEnd := bucketStart + intervalMs
-
 	return bucketStart, bucketEnd
 }