feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/features/channels/date_formatters.dart

@@ -0,0 +1,189 @@
+import 'package:flutter/foundation.dart';
+import 'package:intl/intl.dart';
+
+import '../../shared/l10n/l10n.dart';
+
+// Re-export shortPubkey so existing callers continue to compile.
+export '../../shared/utils/string_utils.dart' show shortPubkey;
+
+final _fullDateFormat = DateFormat('EEEE, MMMM d, y');
+final _shortMonthFormat = DateFormat('MMM');
+final _messageTimeFormat = DateFormat('h:mm a', 'en_US');
+
+/// Returns "Today", "Yesterday", or a full date like "Monday, March 31, 2026".
+///
+/// [now] is exposed for testing; production callers should omit it.
+String formatDayHeading(
+  int unixSeconds, {
+  @visibleForTesting DateTime? now,
+  AppLocalizations? l10n,
+}) {
+  final date = DateTime.fromMillisecondsSinceEpoch(
+    unixSeconds * 1000,
+    isUtc: true,
+  ).toLocal();
+  now ??= DateTime.now();
+  final today = DateTime(now.year, now.month, now.day);
+  final messageDay = DateTime(date.year, date.month, date.day);
+
+  if (today.year == messageDay.year &&
+      today.month == messageDay.month &&
+      today.day == messageDay.day) {
+    return l10n?.timeToday ?? 'Today';
+  }
+  final yesterday = DateTime(now.year, now.month, now.day - 1);
+  if (yesterday.year == messageDay.year &&
+      yesterday.month == messageDay.month &&
+      yesterday.day == messageDay.day) {
+    return l10n?.timeYesterday ?? 'Yesterday';
+  }
+  if (l10n != null) {
+    return l10n.fullDate(
+      _weekdayLabel(l10n, date.weekday),
+      _monthLabel(l10n, date.month),
+      date.day,
+      date.year,
+    );
+  }
+  return _fullDateFormat.format(date);
+}
+
+/// Whether two unix-second timestamps fall on the same calendar day (local time).
+bool isSameDay(int a, int b) {
+  final dtA = DateTime.fromMillisecondsSinceEpoch(
+    a * 1000,
+    isUtc: true,
+  ).toLocal();
+  final dtB = DateTime.fromMillisecondsSinceEpoch(
+    b * 1000,
+    isUtc: true,
+  ).toLocal();
+  return dtA.year == dtB.year && dtA.month == dtB.month && dtA.day == dtB.day;
+}
+
+/// Returns a compact relative time string like "just now", "5m ago", "3h ago",
+/// "2d ago", or a short date for older timestamps.
+String relativeTime(int unixSeconds, {AppLocalizations? l10n}) {
+  final now = DateTime.now();
+  final time = DateTime.fromMillisecondsSinceEpoch(
+    unixSeconds * 1000,
+    isUtc: true,
+  ).toLocal();
+  final diff = now.difference(time);
+
+  if (diff.inMinutes < 1) return l10n?.timeJustNow ?? 'just now';
+  if (diff.inMinutes < 60) {
+    return l10n == null
+        ? '${diff.inMinutes}m ago'
+        : l10n.relativeMinutesAgo(diff.inMinutes);
+  }
+  if (diff.inHours < 24) {
+    return l10n == null
+        ? '${diff.inHours}h ago'
+        : l10n.relativeHoursAgo(diff.inHours);
+  }
+  if (diff.inDays < 7) {
+    return l10n == null
+        ? '${diff.inDays}d ago'
+        : l10n.relativeDaysAgo(diff.inDays);
+  }
+  if (l10n != null) {
+    return l10n.shortDate(
+      _monthLabel(l10n, time.month),
+      time.day,
+    );
+  }
+  return '${time.month}/${time.day}/${time.year}';
+}
+
+/// Returns desktop-parity thread activity copy such as "just now",
+/// "3 hours ago", or "on May 19th".
+String formatThreadSummaryLastReplyTime(
+  int unixSeconds, {
+  @visibleForTesting int? nowSeconds,
+  AppLocalizations? l10n,
+}) {
+  nowSeconds ??= DateTime.now().millisecondsSinceEpoch ~/ 1000;
+  var diff = nowSeconds - unixSeconds;
+  if (diff < 0) diff = 0;
+
+  if (diff < 60) return l10n?.timeJustNow ?? 'just now';
+  if (diff < 3600) {
+    final value = diff ~/ 60;
+    return l10n == null ? _formatAgo(value, 'minute') : l10n.relativeMinutesAgo(value);
+  }
+  if (diff < 86400) {
+    final value = diff ~/ 3600;
+    return l10n == null ? _formatAgo(value, 'hour') : l10n.relativeHoursAgo(value);
+  }
+  if (diff < 604800) {
+    final value = diff ~/ 86400;
+    return l10n == null ? _formatAgo(value, 'day') : l10n.relativeDaysAgo(value);
+  }
+
+  final date = DateTime.fromMillisecondsSinceEpoch(
+    unixSeconds * 1000,
+    isUtc: true,
+  ).toLocal();
+  if (l10n != null) {
+    return l10n.threadOnDate(
+      _monthLabel(l10n, date.month),
+      date.day,
+      l10n.localeName == 'zh_CN' ? '' : _ordinalSuffix(date.day),
+    );
+  }
+  return 'on ${_shortMonthFormat.format(date)} '
+      '${date.day}${_ordinalSuffix(date.day)}';
+}
+
+String _formatAgo(int value, String unit) =>
+    '$value $unit${value == 1 ? '' : 's'} ago';
+
+String _ordinalSuffix(int day) {
+  final lastTwoDigits = day % 100;
+  if (lastTwoDigits >= 11 && lastTwoDigits <= 13) return 'th';
+  return switch (day % 10) {
+    1 => 'st',
+    2 => 'nd',
+    3 => 'rd',
+    _ => 'th',
+  };
+}
+
+/// Desktop-parity message clock time, e.g. "2:34 PM".
+String formatMessageTime(int unixSeconds, {AppLocalizations? l10n}) {
+  final date = DateTime.fromMillisecondsSinceEpoch(
+    unixSeconds * 1000,
+    isUtc: true,
+  ).toLocal();
+  if (l10n == null) return _messageTimeFormat.format(date);
+  final hour = date.hour % 12 == 0 ? 12 : date.hour % 12;
+  final minute = date.minute.toString().padLeft(2, '0');
+  final period = date.hour < 12 ? l10n.timeAm : l10n.timePm;
+  return l10n.messageTime('$hour', minute, period);
+}
+
+String _monthLabel(AppLocalizations l10n, int month) => switch (month) {
+  1 => l10n.monthJan,
+  2 => l10n.monthFeb,
+  3 => l10n.monthMar,
+  4 => l10n.monthApr,
+  5 => l10n.monthMay,
+  6 => l10n.monthJun,
+  7 => l10n.monthJul,
+  8 => l10n.monthAug,
+  9 => l10n.monthSep,
+  10 => l10n.monthOct,
+  11 => l10n.monthNov,
+  _ => l10n.monthDec,
+};
+
+String _weekdayLabel(AppLocalizations l10n, int weekday) => switch (weekday) {
+  DateTime.monday => l10n.weekdayMonday,
+  DateTime.tuesday => l10n.weekdayTuesday,
+  DateTime.wednesday => l10n.weekdayWednesday,
+  DateTime.thursday => l10n.weekdayThursday,
+  DateTime.friday => l10n.weekdayFriday,
+  DateTime.saturday => l10n.weekdaySaturday,
+  _ => l10n.weekdaySunday,
+};