refactor: share ISO date validation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: asizikov

src/pipeline/aggregators/reportContextAggregator.ts

@@ -1,5 +1,6 @@
 import type { Aggregator } from './base'
 import type { TokenUsageHeader, TokenUsageRecord } from '../parser'
+import { isValidIsoDate } from '../isoDate'
 
 export type ReportContextResult = {
   startDate: string | null
@@ -49,19 +50,3 @@ export class ReportContextAggregator implements Aggregator<TokenUsageRecord, Rep
     }
   }
 }
-
-function isValidIsoDate(value: string): boolean {
-  const match = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value)
-  if (!match) return false
-
-  const year = Number(match[1])
-  const month = Number(match[2])
-  const day = Number(match[3])
-  const normalized = new Date(Date.UTC(year, month - 1, day))
-
-  return (
-    normalized.getUTCFullYear() === year
-    && normalized.getUTCMonth() === month - 1
-    && normalized.getUTCDate() === day
-  )
-}

src/pipeline/includedCreditsPolicy.ts

@@ -1,4 +1,5 @@
 import type { ReportFormat, ReportFormatMetadata } from './reportAdapters'
+import { isValidIsoDate } from './isoDate'
 
 export type QuotaUnit = 'pru' | 'aic'
 export type OrganizationIncludedCreditTier = 'business' | 'enterprise'
@@ -37,7 +38,6 @@ export type ReportPeriod = {
 const COPILOT_BUSINESS_LABEL = 'Copilot Business'
 const COPILOT_ENTERPRISE_LABEL = 'Copilot Enterprise'
 const NATIVE_AI_CREDITS_STANDARD_POLICY_START_DATE = '2026-09-01'
-const ISO_DATE_PATTERN = /^(\d{4})-(\d{2})-(\d{2})$/
 
 export const TRANSITION_PERIOD_INCLUDED_CREDITS_POLICY = {
   id: 'transition-period-billing-preview',
@@ -117,22 +117,6 @@ function getReportFormat(reportMetadataOrFormat: ReportFormat | ReportFormatMeta
     : reportMetadataOrFormat.format
 }
 
-function isValidIsoDate(value: string): boolean {
-  const match = ISO_DATE_PATTERN.exec(value)
-  if (!match) return false
-
-  const year = Number(match[1])
-  const month = Number(match[2])
-  const day = Number(match[3])
-  const date = new Date(Date.UTC(year, month - 1, day))
-
-  return (
-    date.getUTCFullYear() === year
-    && date.getUTCMonth() === month - 1
-    && date.getUTCDate() === day
-  )
-}
-
 function isBeforeIsoDate(value: string | null | undefined, boundary: string): boolean {
   if (!value || !isValidIsoDate(value)) return false
 

src/pipeline/isoDate.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest'
+
+import { isValidIsoDate } from './isoDate'
+
+describe('isValidIsoDate', () => {
+  it('accepts only real YYYY-MM-DD calendar dates', () => {
+    expect(isValidIsoDate('2026-03-01')).toBe(true)
+    expect(isValidIsoDate('2024-02-29')).toBe(true)
+    expect(isValidIsoDate('2026-02-30')).toBe(false)
+    expect(isValidIsoDate('2026-13-01')).toBe(false)
+    expect(isValidIsoDate('03/01/2026')).toBe(false)
+    expect(isValidIsoDate(' 2026-03-01 ')).toBe(false)
+  })
+})

src/pipeline/isoDate.ts

@@ -0,0 +1,17 @@
+const ISO_DATE_PATTERN = /^(\d{4})-(\d{2})-(\d{2})$/
+
+export function isValidIsoDate(value: string): boolean {
+  const match = ISO_DATE_PATTERN.exec(value)
+  if (!match) return false
+
+  const year = Number(match[1])
+  const month = Number(match[2])
+  const day = Number(match[3])
+  const normalized = new Date(Date.UTC(year, month - 1, day))
+
+  return (
+    normalized.getUTCFullYear() === year
+    && normalized.getUTCMonth() === month - 1
+    && normalized.getUTCDate() === day
+  )
+}