downsampling for traffic chart #987

service/stats.go

@@ -1,6 +1,7 @@
 package service
 
 import (
+	"sort"
 	"time"
 
 	"github.com/alireza0/s-ui/database"
@@ -93,9 +94,56 @@ func (s *StatsService) GetStats(resource string, tag string, limit int) ([]model
 	if err != nil {
 		return nil, err
 	}
+
+	result = s.downsampleStats(result, 60) // 60 rows for 30 buckets
 	return result, nil
 }
 
+// downsampleStats reduces stats to maxRows rows.
+// Each bucket outputs two rows (direction false and true) with average Traffic.
+func (s *StatsService) downsampleStats(stats []model.Stats, maxRows int) []model.Stats {
+	if len(stats) <= maxRows {
+		return stats
+	}
+	numBuckets := int(maxRows / 2)
+	sort.Slice(stats, func(i, j int) bool { return stats[i].DateTime < stats[j].DateTime })
+	timeMin, timeMax := stats[0].DateTime, stats[len(stats)-1].DateTime
+	bucketSpan := (timeMax - timeMin) / int64(numBuckets)
+	if bucketSpan == 0 {
+		bucketSpan = 1
+	}
+	downsampled := make([]model.Stats, 0, maxRows)
+	for i := 0; i < numBuckets; i++ {
+		bucketStart := timeMin + int64(i)*bucketSpan
+		bucketEnd := timeMin + int64(i+1)*bucketSpan
+		if i == numBuckets-1 {
+			bucketEnd = timeMax + 1
+		}
+		for _, dir := range []bool{false, true} {
+			var sum int64
+			var count int
+			for _, r := range stats {
+				if r.DateTime >= bucketStart && r.DateTime < bucketEnd && r.Direction == dir {
+					sum += r.Traffic
+					count++
+				}
+			}
+			avg := int64(0)
+			if count > 0 {
+				avg = sum / int64(count)
+			}
+			downsampled = append(downsampled, model.Stats{
+				DateTime:  bucketStart,
+				Resource:  stats[0].Resource,
+				Tag:       stats[0].Tag,
+				Direction: dir,
+				Traffic:   avg,
+			})
+		}
+	}
+	return downsampled
+}
+
 func (s *StatsService) GetOnlines() (onlines, error) {
 	return *onlineResources, nil
 }