import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:uuid/uuid.dart';

import '../models/fuel_entry.dart';
import '../models/vehicle.dart';
import 'storage_service.dart';

/// Single source of truth for the app's in-memory data (vehicles + fuel
/// entries), backed by [StorageService] for persistence. Screens read from
/// this via Provider and call its mutating methods, which take care of
/// writing through to disk and notifying listeners.
class AppState extends ChangeNotifier {
  final StorageService storage = StorageService();
  final _uuid = const Uuid();

  List<Vehicle> vehicles = [];
  List<FuelEntry> fuelEntries = [];
  bool isLoading = true;

  Future<void> init() async {
    await storage.init();
    final data = await storage.loadData();
    vehicles = data.vehicles;
    fuelEntries = data.entries;
    isLoading = false;
    notifyListeners();
  }

  Future<void> addVehicle({
    required String make,
    required String model,
    required String color,
    required String licensePlate,
  }) async {
    vehicles.add(Vehicle(
      id: _uuid.v4(),
      make: make,
      model: model,
      color: color,
      licensePlate: licensePlate,
    ));
    await _persist();
  }

  Future<void> updateVehicle(Vehicle updated) async {
    final index = vehicles.indexWhere((v) => v.id == updated.id);
    if (index != -1) {
      vehicles[index] = updated;
      await _persist();
    }
  }

  Future<void> deleteVehicle(String vehicleId) async {
    for (final entry in fuelEntries.where((e) => e.vehicleId == vehicleId)) {
      await storage.deleteReceiptImage(entry.receiptImagePath);
    }
    fuelEntries.removeWhere((e) => e.vehicleId == vehicleId);
    vehicles.removeWhere((v) => v.id == vehicleId);
    await _persist();
  }

  Future<FuelEntry> addFuelEntry({
    required String vehicleId,
    required DateTime date,
    required double gallons,
    required double pricePerGallon,
    required double totalCost,
    File? receiptImage,
  }) async {
    final id = _uuid.v4();
    String? storedImagePath;
    if (receiptImage != null) {
      storedImagePath = await storage.storeReceiptImage(receiptImage, id);
    }

    final entry = FuelEntry(
      id: id,
      vehicleId: vehicleId,
      date: date,
      gallons: gallons,
      pricePerGallon: pricePerGallon,
      totalCost: totalCost,
      receiptImagePath: storedImagePath,
    );
    fuelEntries.add(entry);
    await _persist();
    return entry;
  }

  Future<void> deleteFuelEntry(String entryId) async {
    final entry = fuelEntries.firstWhere((e) => e.id == entryId);
    await storage.deleteReceiptImage(entry.receiptImagePath);
    fuelEntries.removeWhere((e) => e.id == entryId);
    await _persist();
  }

  List<FuelEntry> entriesForVehicle(String vehicleId) {
    final list = fuelEntries.where((e) => e.vehicleId == vehicleId).toList();
    list.sort((a, b) => b.date.compareTo(a.date));
    return list;
  }

  double totalGallonsForVehicle(String vehicleId) => fuelEntries
      .where((e) => e.vehicleId == vehicleId)
      .fold(0.0, (sum, e) => sum + e.gallons);

  double get totalGallonsAllVehicles =>
      fuelEntries.fold(0.0, (sum, e) => sum + e.gallons);

  Vehicle? vehicleById(String id) {
    try {
      return vehicles.firstWhere((v) => v.id == id);
    } catch (_) {
      return null;
    }
  }

  Future<void> changeSaveDirectory(String newPath) async {
    await storage.setSaveDirectory(newPath);
    notifyListeners();
  }

  Future<void> _persist() async {
    await storage.saveData(vehicles: vehicles, entries: fuelEntries);
    notifyListeners();
  }
}