import 'package:drift/drift.dart';
import 'package:uuid/uuid.dart';

import '../database/app_database.dart';
import '../models/product.dart';

class InsufficientStockException implements Exception {
  const InsufficientStockException();

  @override
  String toString() => 'Not enough stock';
}

abstract class ProductService {
  Future<List<Product>> getProducts();

  Future<Product?> getProductById(String id);

  Future<void> createProduct({
    required String name,
    required String category,
    required int stockQuantity,
    required int lowStockThreshold,
    required int priceInCents,
    required String? imagePath,
  });

  Future<void> updateProduct(Product product);

  Future<void> deleteProduct(String id);

  Future<void> decreaseStock(String productId, int amount);

  Future<void> increaseStock(String productId, int amount);
}

class DriftProductService implements ProductService {
  final AppDatabase database;
  final _uuid = const Uuid();

  DriftProductService({required this.database});

  Product _mapRowToProduct(ProductRow row) {
    return Product(
      id: row.id,
      name: row.name,
      category: row.category,
      stockQuantity: row.stockQuantity,
      lowStockThreshold: row.lowStockThreshold,
      priceInCents: row.priceInCents,
      imagePath: row.imagePath,
      active: row.active,
    );
  }

  @override
  Future<List<Product>> getProducts() async {
    final query = database.select(database.products)
      ..where((product) => product.active.equals(true))
      ..orderBy([(product) => OrderingTerm.asc(product.name)]);

    final rows = await query.get();

    return rows.map(_mapRowToProduct).toList();
  }

  @override
  Future<Product?> getProductById(String id) async {
    final query = database.select(database.products)
      ..where((product) => product.id.equals(id));

    final row = await query.getSingleOrNull();

    if (row == null) {
      return null;
    }

    return _mapRowToProduct(row);
  }

  @override
  Future<void> createProduct({
    required String name,
    required String category,
    required int stockQuantity,
    required int lowStockThreshold,
    required int priceInCents,
    required String? imagePath,
  }) async {
    await database
        .into(database.products)
        .insert(
          ProductsCompanion.insert(
            id: _uuid.v4(),
            name: name,
            category: category,
            stockQuantity: stockQuantity,
            lowStockThreshold: lowStockThreshold,
            priceInCents: priceInCents,
            imagePath: Value(imagePath),
          ),
        );
  }

  @override
  Future<void> updateProduct(Product product) async {
    final query = database.update(database.products)
      ..where((row) => row.id.equals(product.id));

    await query.write(
      ProductsCompanion(
        name: Value(product.name),
        category: Value(product.category),
        stockQuantity: Value(product.stockQuantity),
        lowStockThreshold: Value(product.lowStockThreshold),
        priceInCents: Value(product.priceInCents),
        imagePath: Value(product.imagePath),
        active: Value(product.active),
      ),
    );
  }

  @override
  Future<void> deleteProduct(String id) async {
    final query = database.delete(database.products)
      ..where((product) => product.id.equals(id));

    await query.go();
  }

  @override
  Future<void> decreaseStock(String productId, int amount) async {
    final product = await getProductById(productId);

    if (product == null) {
      throw Exception('Product not found');
    }

    if (product.stockQuantity < amount) {
      throw const InsufficientStockException();
    }

    await updateProduct(
      product.copyWith(stockQuantity: product.stockQuantity - amount),
    );
  }

  @override
  Future<void> increaseStock(String productId, int amount) async {
    final product = await getProductById(productId);

    if (product == null) {
      throw Exception('Product not found');
    }

    await updateProduct(
      product.copyWith(stockQuantity: product.stockQuantity + amount),
    );
  }
}