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

/// Service handling shared packing lists per trip.
///
/// Uses local `SharedPreferences` for fast offline access. The list can later
/// be synced remotely without changing the calling code.
class PackingService {
  /// Loads packing items for a trip. Returns empty list if none/corrupted.
  Future<List<PackingItem>> loadItems(String tripId) async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_key(tripId));
    if (raw == null) return const [];
    try {
      return PackingItem.decodeList(raw);
    } catch (_) {
      await prefs.remove(_key(tripId));
      return const [];
    }
  }

  /// Saves complete list.
  Future<void> saveItems(String tripId, List<PackingItem> items) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_key(tripId), PackingItem.encodeList(items));
  }

  /// Adds one item.
  Future<List<PackingItem>> addItem(String tripId, PackingItem item) async {
    final current = await loadItems(tripId);
    final updated = [...current, item];
    await saveItems(tripId, updated);
    return updated;
  }

  /// Toggles packed flag.
  Future<List<PackingItem>> toggleItem(String tripId, String itemId) async {
    final current = await loadItems(tripId);
    final updated = current
        .map((i) {
          if (i.id != itemId) return i;
          return i.copyWith(isPacked: !i.isPacked);
        })
        .toList(growable: false);
    await saveItems(tripId, updated);
    return updated;
  }

  /// Deletes an item.
  Future<List<PackingItem>> deleteItem(String tripId, String itemId) async {
    final current = await loadItems(tripId);
    final updated = current.where((i) => i.id != itemId).toList();
    await saveItems(tripId, updated);
    return updated;
  }

  /// Suggests a starter template based on duration/weather (simplified here).
  List<String> suggestedItems({required int nights, required bool cold}) {
    final base = [
      'Passeport/ID',
      'Billets / PNR',
      'Chargeurs et adaptateurs',
      'Trousse de secours',
      'Assurance voyage',
    ];
    if (cold) {
      base.addAll(['Veste chaude', 'Gants', 'Bonnet', 'Chaussettes chaudes']);
    } else {
      base.addAll(['Crème solaire', 'Lunettes de soleil', 'Maillot de bain']);
    }
    if (nights > 4) {
      base.add('Lessive/ziplock');
    }
    return base;
  }

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