chore: import upstream snapshot with attribution

apps/sim/app/api/users/me/usage-logs/shared.ts

@@ -0,0 +1,28 @@
+import type { UsageLogPeriod } from '@/lib/api/contracts/user'
+
+const PERIOD_TO_DAYS: Record<'1d' | '7d' | '30d', number> = { '1d': 1, '7d': 7, '30d': 30 }
+
+interface ResolvedDateRange {
+  startDate: Date | undefined
+  endDate: Date
+}
+
+/** Shared by the list and export routes so their date-filtering can never drift. */
+export function resolveDateRange(
+  period: UsageLogPeriod,
+  customStartDate: string | undefined,
+  customEndDate: string | undefined
+): ResolvedDateRange {
+  if (period === 'custom') {
+    if (!customStartDate) throw new Error('startDate is required when period is "custom"')
+    return {
+      startDate: new Date(customStartDate),
+      endDate: customEndDate ? new Date(customEndDate) : new Date(),
+    }
+  }
+  if (period === 'all') return { startDate: undefined, endDate: new Date() }
+
+  const startDate = new Date()
+  startDate.setDate(startDate.getDate() - PERIOD_TO_DAYS[period])
+  return { startDate, endDate: new Date() }
+}