/// Small formatting helpers shared across screens.
library;

String greetingForNow([DateTime? now]) {
  final h = (now ?? DateTime.now()).hour;
  if (h < 12) return 'Good morning';
  if (h < 17) return 'Good afternoon';
  return 'Good evening';
}

/// "Just now" / "18 min ago" / "3 hr ago" / "5 d ago"
String relativeTime(DateTime? at, [DateTime? now]) {
  if (at == null) return '';
  final mins = (now ?? DateTime.now()).difference(at).inMinutes;
  if (mins < 1) return 'Just now';
  if (mins < 60) return '$mins min ago';
  final hrs = (mins / 60).round();
  if (hrs < 24) return '$hrs hr ago';
  return '${(hrs / 24).round()} d ago';
}

const _months = [
  'Jan',
  'Feb',
  'Mar',
  'Apr',
  'May',
  'Jun',
  'Jul',
  'Aug',
  'Sep',
  'Oct',
  'Nov',
  'Dec',
];

/// "Today" / "Yesterday" / "29 Aug"
String dateLabel(DateTime date, [DateTime? now]) {
  final today = now ?? DateTime.now();
  bool sameDay(DateTime a, DateTime b) =>
      a.year == b.year && a.month == b.month && a.day == b.day;

  if (sameDay(date, today)) return 'Today';
  final yesterday = today.subtract(const Duration(days: 1));
  if (sameDay(date, yesterday)) return 'Yesterday';
  return '${date.day} ${_months[date.month - 1]}';
}

/// "SEPTEMBER 2026" — the eyebrow over a tab root's title. Spelled in full
/// rather than abbreviated: it is read once, at the top of the screen, and
/// "SEP 2026" saves four characters nobody needed saved.
String monthLabel(DateTime date) => '${_monthsFull[date.month - 1]} ${date.year}';

const _monthsFull = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December',
];

/// Initials for an avatar, e.g. "Joe Oommen" -> "JO".
String initialsOf(String? name) {
  final n = (name ?? '').trim();
  if (n.isEmpty) return 'DM';
  final letters = n
      .split(RegExp(r'\s+'))
      .map((p) => p.isEmpty ? '' : p[0])
      .join();
  return letters
      .substring(0, letters.length < 2 ? letters.length : 2)
      .toUpperCase();
}