import 'package:anyway/domain/entities/trip.dart';
import 'package:geocoding/geocoding.dart';

class TripLocationUtils {
  const TripLocationUtils._();

  static List<double>? startCoordinates(Trip trip) {
    if (trip.landmarks.isEmpty) {
      return null;
    }
    final coords = trip.landmarks.first.location;
    if (coords.length < 2) {
      return null;
    }
    return coords;
  }

  static Future<TripLocaleInfo> resolveLocaleInfo(Trip trip) async {
    final coords = startCoordinates(trip);
    if (coords == null) {
      return const TripLocaleInfo();
    }

    if (GeocodingPlatform.instance == null) {
      final fallbackCity = '${coords[0].toStringAsFixed(2)}, ${coords[1].toStringAsFixed(2)}';
      return TripLocaleInfo(cityName: fallbackCity, coordinates: coords);
    }

    try {
      final placemarks = await placemarkFromCoordinates(coords[0], coords[1]);
      if (placemarks.isEmpty) {
        return TripLocaleInfo(coordinates: coords);
      }
      final placemark = placemarks.first;
      final city = placemark.locality ?? placemark.subAdministrativeArea;
      final country = placemark.country;
      final isoCountryCode = placemark.isoCountryCode;
      return TripLocaleInfo(cityName: city, countryName: country, countryCode: isoCountryCode, flagEmoji: _flagEmoji(isoCountryCode), coordinates: coords);
    } catch (_) {
      return TripLocaleInfo(coordinates: coords);
    }
  }

  static Future<String> resolveCityName(Trip trip) async {
    final localeInfo = await resolveLocaleInfo(trip);
    return localeInfo.cityName ?? 'Unknown';
  }

  static String? _flagEmoji(String? countryCode) {
    if (countryCode == null || countryCode.length != 2) {
      return null;
    }
    final upper = countryCode.toUpperCase();
    final first = upper.codeUnitAt(0);
    final second = upper.codeUnitAt(1);
    if (!_isAsciiLetter(first) || !_isAsciiLetter(second)) {
      return null;
    }
    const base = 0x1F1E6;
    final firstFlag = base + (first - 0x41);
    final secondFlag = base + (second - 0x41);
    return String.fromCharCodes([firstFlag, secondFlag]);
  }

  static bool _isAsciiLetter(int codeUnit) => codeUnit >= 0x41 && codeUnit <= 0x5A;
}

class TripLocaleInfo {
  const TripLocaleInfo({this.cityName, this.countryName, this.countryCode, this.flagEmoji, this.coordinates});

  final String? cityName;
  final String? countryName;
  final String? countryCode;
  final String? flagEmoji;
  final List<double>? coordinates;

  bool get hasResolvedCity => cityName != null && cityName!.trim().isNotEmpty && cityName != 'Unknown';
}