import 'package:shared_preferences/shared_preferences.dart';
import 'package:travel_mate/models/emergency_contact.dart';

/// Stores emergency contacts per trip for offline access.
///
/// Data is persisted locally in `SharedPreferences` under the key
/// `emergency_<tripId>`. Corrupted payloads are cleaned up automatically to
/// avoid crashing the UI during critical usage.
class EmergencyService {
  /// Loads contacts for [tripId]. Returns an empty list if none or corrupted.
  Future<List<EmergencyContact>> loadContacts(String tripId) async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_key(tripId));
    if (raw == null) return const [];
    try {
      return EmergencyContact.decodeList(raw);
    } catch (_) {
      await prefs.remove(_key(tripId));
      return const [];
    }
  }

  /// Saves the complete contact list.
  Future<void> saveContacts(
    String tripId,
    List<EmergencyContact> contacts,
  ) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_key(tripId), EmergencyContact.encodeList(contacts));
  }

  /// Adds a contact and returns updated list.
  Future<List<EmergencyContact>> addContact(
    String tripId,
    EmergencyContact contact,
  ) async {
    final current = await loadContacts(tripId);
    final updated = [...current, contact];
    await saveContacts(tripId, updated);
    return updated;
  }

  /// Deletes a contact.
  Future<List<EmergencyContact>> deleteContact(
    String tripId,
    String contactId,
  ) async {
    final current = await loadContacts(tripId);
    final updated = current.where((c) => c.id != contactId).toList();
    await saveContacts(tripId, updated);
    return updated;
  }

  String _key(String tripId) => 'emergency_$tripId';
}