fix(frontend/activity_timeline): use SI prefixes

Modifies activity timeline values to be displayed in SI-prefixed
format, e.g. instead of `5100000 B` `5.1 MB`, etc. This change
should improve readability.

Author: dbnk0

frontend/src/components/ActivityTimeline.vue

@@ -8,6 +8,7 @@ import 'chartjs-adapter-date-fns'
 import {
   CHART_COMMON_OPTIONS,
   CHART_SCALE_X_OPTIONS,
+  formatSI,
   resampleTimedData,
   setChartDatetimeRange,
 } from '@/utils/commonCharts.js'
@@ -64,7 +65,7 @@ const chartOptions = computed(() => {
       x: scaleXOptions,
       packets: {
         ticks: {
-          callback: (v) => `${v} ${CHART_UNITS[0]}`,
+          callback: (v) => formatSI(v, CHART_UNITS[0]),
           color: CHART_COLORS[0],
         },
         grid: { tickColor: CHART_COLORS[0], drawOnChartArea: false },
@@ -73,7 +74,7 @@ const chartOptions = computed(() => {
       },
       flows: {
         ticks: {
-          callback: (v) => `${v} ${CHART_UNITS[1]}`,
+          callback: (v) => formatSI(v, CHART_UNITS[1]),
           color: CHART_COLORS[1],
         },
         grid: { tickColor: CHART_COLORS[1], drawOnChartArea: false },
@@ -82,7 +83,7 @@ const chartOptions = computed(() => {
       },
       bytes: {
         ticks: {
-          callback: (v) => `${v} ${CHART_UNITS[2]}`,
+          callback: (v) => formatSI(v, CHART_UNITS[2]),
           color: CHART_COLORS[2],
         },
         grid: { tickColor: CHART_COLORS[2] },
@@ -96,7 +97,7 @@ const chartOptions = computed(() => {
         callbacks: {
           label: (item) => {
             let unit = CHART_UNITS[item.datasetIndex]
-            return `${item.formattedValue} ${unit}`
+            return formatSI(item.parsed.y, unit, 2)
           },
         },
         usePointStyle: true,

frontend/src/utils/commonCharts.js

@@ -110,3 +110,30 @@ export function resampleTimedData(data, dtKey, unitCount, unit, reduceFn, addEmp
   // Ensure correct order of buckets
   return result.sort((a, b) => a[dtKey] - b[dtKey])
 }
+
+/**
+ * Formats a number using SI prefixes (k, M, G, ...)
+ *
+ * Values < 1e3 are not formatted.
+ *
+ * @param {Number} value Value to format
+ * @param {String} unit Unit to append to the formatted value (e.g. 'B', 'Hz')
+ * @param {Number} decimalPlaces Number of decimal places to show (only for values
+ *   >= 1e3). Default is 1.
+ * @returns {String} Formatted string
+ */
+export function formatSI(value, unit = '', decimalPlaces = 1) {
+  const absValue = Math.abs(value)
+  if (absValue < 1e3) return `${value} ${unit}`
+
+  const units = ['', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y']
+  let i = 0
+  let formattedValue = value
+
+  while (i < units.length && Math.abs(formattedValue) >= 1e3) {
+    formattedValue /= 1e3
+    i++
+  }
+
+  return `${formattedValue.toFixed(decimalPlaces)} ${units[i]}${unit}`
+}