import 'package:intl/intl.dart';

/// The time next to a room in the list: the time today, the weekday this
/// week, the date before that.
String formatListTime(DateTime time, {DateTime? now}) {
  final local = time.toLocal();
  final today = _day(now ?? DateTime.now());
  final day = _day(local);
  final days = today.difference(day).inDays;
  if (days <= 0) return DateFormat.Hm().format(local);
  if (days == 1) return 'Yesterday';
  if (days < 7) return DateFormat.E().format(local);
  if (local.year == today.year) return DateFormat.MMMd().format(local);
  return DateFormat.yMd().format(local);
}

/// The separator above a day's messages.
String formatDay(DateTime day, {DateTime? now}) {
  final today = _day(now ?? DateTime.now());
  final days = today.difference(_day(day)).inDays;
  if (days == 0) return 'Today';
  if (days == 1) return 'Yesterday';
  if (days < 7) return DateFormat.EEEE().format(day);
  if (day.year == today.year) return DateFormat.MMMMEEEEd().format(day);
  return DateFormat.yMMMMEEEEd().format(day);
}

/// The time under a message.
String formatTime(DateTime time) => DateFormat.Hm().format(time.toLocal());

/// A file size for people: 980 B, 12 KB, 3.4 MB.
String formatBytes(int bytes) {
  if (bytes < 1000) return '$bytes B';
  const units = ['KB', 'MB', 'GB'];
  var value = bytes / 1000;
  var unit = 0;
  while (value >= 1000 && unit < units.length - 1) {
    value /= 1000;
    unit++;
  }
  final digits = value < 10 ? 1 : 0;
  return '${value.toStringAsFixed(digits)} ${units[unit]}';
}

DateTime _day(DateTime t) => DateTime(t.year, t.month, t.day);