import 'package:intl/intl.dart';
import 'package:timezone/data/latest.dart' as tz_data;
import 'package:timezone/timezone.dart' as tz;

/// Heure métier alignée sur le fuseau du serveur API (pas l'UTC ni le téléphone).
abstract final class ServerTime {
  static const defaultTimezone = 'Europe/Paris';

  static bool _initialized = false;
  static tz.Location _location = tz.UTC;

  static Future<void> initialize({String timezone = defaultTimezone}) async {
    if (!_initialized) {
      tz_data.initializeTimeZones();
      _initialized = true;
    }
    setTimezone(timezone);
  }

  static void setTimezone(String timezone) {
    if (!_initialized) {
      tz_data.initializeTimeZones();
      _initialized = true;
    }
    _location = tz.getLocation(timezone);
  }

  static String get timezone => _location.name;

  static tz.TZDateTime now() => tz.TZDateTime.now(_location);

  static DateTime startOfToday() {
    final current = now();
    return DateTime(current.year, current.month, current.day);
  }

  static DateTime? parse(String? iso) {
    if (iso == null || iso.isEmpty) {
      return null;
    }
    return DateTime.tryParse(iso);
  }

  static tz.TZDateTime toServerTime(DateTime dateTime) {
    return tz.TZDateTime.from(dateTime.toUtc(), _location);
  }

  static String format(
    DateTime? dateTime, {
    required String pattern,
    String locale = 'fr_FR',
  }) {
    if (dateTime == null) {
      return '';
    }

    final server = toServerTime(dateTime);
    return DateFormat(pattern, locale).format(
      DateTime(
        server.year,
        server.month,
        server.day,
        server.hour,
        server.minute,
        server.second,
        server.millisecond,
        server.microsecond,
      ),
    );
  }
}