ui phase 10

client/src/utils/date.ts

@@ -41,3 +41,38 @@ export function formatShamsiDateTime(iso: string | Date, locale: string = 'fa'):
 export function formatShamsiMonthYear(iso: string | Date, locale: string = 'fa'): string {
   return formatShamsiDate(iso, locale, { year: 'numeric', month: 'long' });
 }
+
+/** Time only (hh:mm) — a chat bubble's stamp once its date lives on a separator instead (§3.2). */
+export function formatShamsiTime(iso: string | Date, locale: string = 'fa'): string {
+  return formatShamsiDate(iso, locale, { hour: '2-digit', minute: '2-digit' });
+}
+
+/**
+ * Whole calendar days between two timestamps, comparing the **formatted date string** (not raw ms
+ * subtraction, which is wrong across a DST/timezone boundary) — two timestamps format identically iff
+ * they fall on the same calendar day in the active calendar system.
+ */
+function isSameCalendarDay(a: Date, b: Date, locale: string): boolean {
+  return formatShamsiDate(a, locale) === formatShamsiDate(b, locale);
+}
+
+/**
+ * A chat-style day-separator label: the caller's «امروز»/«دیروز» for the last two calendar days, else the
+ * plain Shamsi date (e.g. «۲۵ تیر ۱۴۰۵»). Calendar-agnostic — it never does its own Jalali arithmetic,
+ * only compares already-formatted date strings (see `isSameCalendarDay`).
+ */
+export function formatDaySeparator(
+  iso: string | Date,
+  locale: string,
+  todayLabel: string,
+  yesterdayLabel: string,
+): string {
+  const date = iso instanceof Date ? iso : new Date(iso);
+  if (Number.isNaN(date.getTime())) return '';
+  const now = new Date();
+  if (isSameCalendarDay(date, now, locale)) return todayLabel;
+  const yesterday = new Date(now);
+  yesterday.setDate(yesterday.getDate() - 1);
+  if (isSameCalendarDay(date, yesterday, locale)) return yesterdayLabel;
+  return formatShamsiDate(date, locale);
+}