import 'dart:async';

import 'package:flutter_test/flutter_test.dart';
import 'package:kooltap/models/product.dart';
import 'package:kooltap/services/product_service.dart';
import 'package:kooltap/viewmodels/inventory_view_model.dart';
import 'package:mocktail/mocktail.dart';

class MockProductService extends Mock implements ProductService {}

void main() {
  late MockProductService mockService;
  late StreamController<List<Product>> products;
  late InventoryViewModel viewModel;

  const beer = Product(
    id: 'prod-1',
    name: 'Beer',
    category: 'Drinks',
    stockQuantity: 20,
    lowStockThreshold: 5,
    priceInCents: 400,
  );

  setUp(() {
    mockService = MockProductService();
    products = StreamController<List<Product>>.broadcast();
    when(() => mockService.watchProducts()).thenAnswer((_) => products.stream);

    viewModel = InventoryViewModel(productService: mockService);
  });

  tearDown(() async {
    viewModel.dispose();
    await products.close();
  });

  group('InventoryViewModel', () {
    test('is loading until the first emission', () async {
      viewModel.ensureLoaded();
      expect(viewModel.isLoading, true);

      products.add([beer]);
      await pumpEventQueue();

      expect(viewModel.isLoading, false);
      expect(viewModel.products, [beer]);
    });

    test('follows stock changes from the database', () async {
      viewModel.ensureLoaded();
      products.add([beer]);
      await pumpEventQueue();

      products.add([beer.copyWith(stockQuantity: 19)]);
      await pumpEventQueue();

      expect(viewModel.products.single.stockQuantity, 19);
    });

    test('subscribes only once', () async {
      viewModel.ensureLoaded();
      viewModel.ensureLoaded();

      verify(() => mockService.watchProducts()).called(1);
    });

    test('notifies listeners on every emission', () async {
      var notifyCount = 0;
      viewModel.addListener(() => notifyCount++);
      viewModel.ensureLoaded();

      products
        ..add([beer])
        ..add([]);
      await pumpEventQueue();

      expect(notifyCount, 2);
    });

    test('exposes a load error when the stream fails', () async {
      viewModel.ensureLoaded();
      products.addError(StateError('database closed'));
      await pumpEventQueue();

      expect(viewModel.loadError, isNotNull);
    });
  });
}