import 'package:flutter_test/flutter_test.dart';
import 'package:nearle_pos/data/datasources/local_store.dart';
import 'package:nearle_pos/data/datasources/seed_data.dart';
import 'package:nearle_pos/data/local/promo_dao.dart';
import 'package:nearle_pos/data/repositories/product_repository_impl.dart';
import 'package:nearle_pos/data/repositories/customer_repository_impl.dart';
import 'package:nearle_pos/data/repositories/transaction_repository_impl.dart';
import 'package:nearle_pos/domain/entities/cart.dart';
import 'package:nearle_pos/domain/entities/promo.dart';
import 'package:nearle_pos/domain/entities/transaction.dart';
import 'package:nearle_pos/domain/services/promo_engine.dart';
import 'package:nearle_pos/domain/usecases/checkout_sale.dart';

void main() {
  late LocalStore store;
  late PromoDao promos;

  setUpAll(() {
    LocalStore.registerSeed(
      products: SeedData.products,
      customers: SeedData.customers,
    );
  });

  setUp(() async {
    store = LocalStore.instance;
    await store.reset(withCatalogue: true);
    promos = store.promos;
  });

  const weekendSaver = Promo(
    id: '',
    name: 'Weekend Saver',
    type: PromoType.percentOffBill,
    value: 10,
    minBillValue: 500,
    maxDiscount: 200,
    daysOfWeek: {6, 7},
  );

  group('storage', () {
    test('a campaign round-trips with every field intact', () async {
      final saved = await promos.save(weekendSaver.copyWith(
        validFrom: DateTime(2026, 8),
        validTo: DateTime(2026, 8, 31),
      ),);

      final read = await promos.findById(saved.id);

      expect(read!.name, 'Weekend Saver');
      expect(read.type, PromoType.percentOffBill);
      expect(read.value, 10);
      expect(read.minBillValue, 500);
      expect(read.maxDiscount, 200);
      expect(read.daysOfWeek, {6, 7});
      expect(read.validFrom, DateTime(2026, 8));
      expect(read.stackable, isFalse);
      expect(read.isActive, isTrue);
    });

    test('editing keeps the id, so nothing points at a stale row', () async {
      final saved = await promos.save(weekendSaver);
      final edited = await promos.save(saved.copyWith(value: 15));

      expect(edited.id, saved.id);
      expect(await promos.all(), hasLength(1));
      expect(edited.value, 15);
    });

    test('pausing removes it from what the till applies', () async {
      final saved = await promos.save(weekendSaver);

      await promos.setActive(saved.id, active: false);

      expect(await promos.all(), hasLength(1));
      expect(await promos.all(activeOnly: true), isEmpty);
    });
  });

  group('validation', () {
    test('a campaign must give something away', () async {
      await expectLater(
        promos.save(const Promo(
          id: '',
          name: 'Nothing',
          type: PromoType.percentOffBill,
        ),),
        throwsA(isA<PromoException>()),
      );
    });

    test('a percentage over 100 is refused', () async {
      // Over 100% is a refund with extra steps.
      await expectLater(
        promos.save(const Promo(
          id: '',
          name: 'Too much',
          type: PromoType.percentOffBill,
          value: 150,
        ),),
        throwsA(isA<PromoException>()),
      );
    });

    test('a targeted campaign without a target is refused', () async {
      // It would save happily and then silently never fire, which is worse
      // than an error.
      await expectLater(
        promos.save(const Promo(
          id: '',
          name: 'Category promo',
          type: PromoType.percentOffCategory,
          value: 10,
        ),),
        throwsA(isA<PromoException>()),
      );
    });

    test('an end date before the start is refused', () async {
      await expectLater(
        promos.save(weekendSaver.copyWith(
          validFrom: DateTime(2026, 9),
          validTo: DateTime(2026, 8),
        ),),
        throwsA(isA<PromoException>()),
      );
    });

    test('a buy-X-get-Y with no quantities is refused', () async {
      await expectLater(
        promos.save(const Promo(
          id: '',
          name: 'Broken BOGO',
          type: PromoType.buyXGetY,
          targetId: 'p1',
        ),),
        throwsA(isA<PromoException>()),
      );
    });
  });

  group('on a completed sale', () {
    test('the discount given is recorded and read back', () async {
      // A bill stores the amount, not a link to the campaign, so a promo that
      // is later edited or deleted cannot change what a past sale shows.
      final products = ProductRepositoryImpl(store);
      final transactions = TransactionRepositoryImpl(store);
      final checkout = CheckoutSale(
        productRepository: products,
        customerRepository: CustomerRepositoryImpl(store),
        transactionRepository: transactions,
      );

      final milk = (await products.findByBarcode('8901234500011'))!;
      final saved = await promos.save(const Promo(
        id: '',
        name: 'Ten off everything',
        type: PromoType.percentOffBill,
        value: 10,
      ),);

      var cart = Cart(lines: [CartLine(product: milk, quantity: 10)]);
      cart = cart.copyWith(
        appliedPromos: PromoEngine.evaluate(
          cart: cart,
          promos: [saved],
          at: DateTime.now(),
        ),
      );

      expect(cart.appliedPromos, hasLength(1));
      expect(cart.promoDiscountAmount, 62);
      final due = cart.grandTotal;

      await checkout(
        cart: cart,
        payments: [
          PaymentSplit(method: PaymentMethod.cash, amount: due, tendered: due),
        ],
        cashierName: 'Divya',
        terminalId: 'T0TEST',
      );

      final stored = (await transactions.history()).single;

      expect(stored.total, due,
          reason: 'the figure charged must not move in storage',);
      expect(stored.cart.appliedPromos, hasLength(1));
      expect(stored.cart.appliedPromos.single.promo.name, 'Ten off everything');
      expect(stored.cart.appliedPromos.single.amount, 62);
    });

    test('a promo and a manual discount are not double-counted on read-back',
        () async {
      // bill_discount on the row already contains the promo. Restoring both at
      // full value would discount the bill twice on the way back in — the exact
      // shape of the bug that used to overstate synced totals.
      final products = ProductRepositoryImpl(store);
      final transactions = TransactionRepositoryImpl(store);
      final checkout = CheckoutSale(
        productRepository: products,
        customerRepository: CustomerRepositoryImpl(store),
        transactionRepository: transactions,
      );

      final milk = (await products.findByBarcode('8901234500011'))!;
      final saved = await promos.save(const Promo(
        id: '',
        name: 'Fifty off',
        type: PromoType.flatOffBill,
        value: 50,
      ),);

      var cart = Cart(
        lines: [CartLine(product: milk, quantity: 10)],
        billDiscount: const Discount(type: DiscountType.flat, value: 30),
      );
      cart = cart.copyWith(
        appliedPromos: PromoEngine.evaluate(
          cart: cart,
          promos: [saved],
          at: DateTime.now(),
        ),
      );

      expect(cart.billDiscountTotal, 80, reason: '50 promo + 30 manual');
      final due = cart.grandTotal;

      await checkout(
        cart: cart,
        payments: [
          PaymentSplit(method: PaymentMethod.cash, amount: due, tendered: due),
        ],
        cashierName: 'Divya',
        terminalId: 'T0TEST',
      );

      final stored = (await transactions.history()).single;

      expect(stored.cart.billDiscountTotal, 80);
      expect(stored.cart.promoDiscountAmount, 50);
      expect(stored.cart.manualBillDiscountAmount, 30);
      expect(stored.total, due);
    });

    test('deleting a campaign does not change a bill already rung', () async {
      final products = ProductRepositoryImpl(store);
      final transactions = TransactionRepositoryImpl(store);
      final checkout = CheckoutSale(
        productRepository: products,
        customerRepository: CustomerRepositoryImpl(store),
        transactionRepository: transactions,
      );

      final milk = (await products.findByBarcode('8901234500011'))!;
      final saved = await promos.save(const Promo(
        id: '',
        name: 'Doomed campaign',
        type: PromoType.flatOffBill,
        value: 100,
      ),);

      var cart = Cart(lines: [CartLine(product: milk, quantity: 10)]);
      cart = cart.copyWith(
        appliedPromos: PromoEngine.evaluate(
          cart: cart,
          promos: [saved],
          at: DateTime.now(),
        ),
      );
      final due = cart.grandTotal;

      await checkout(
        cart: cart,
        payments: [
          PaymentSplit(method: PaymentMethod.cash, amount: due, tendered: due),
        ],
        cashierName: 'Divya',
        terminalId: 'T0TEST',
      );

      await promos.delete(saved.id);

      final stored = (await transactions.history()).single;
      expect(stored.total, due);
      expect(stored.cart.appliedPromos.single.promo.name, 'Doomed campaign');
      expect(stored.cart.appliedPromos.single.amount, 100);
    });
  });
}