import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
import { CreateProductDto } from '../dto/create-product.dto';
import { FindProductsDto } from '../dto/find-products.dto';
import { ProductRepository } from '../repositories/product.repository';
import { CategoryRepository } from '../repositories/category.repository';
import { EntityManager } from '@mikro-orm/postgresql';
import { RequiredEntityData, FilterQuery } from '@mikro-orm/core';
import { Product } from '../entities/product.entity';
import { CategoryMessage, ProductMessage, RestMessage } from 'src/common/enums/message.enum';
import { Favorite } from '../entities/favorite.entity';
import { Variant } from '../entities/variant.entity';
import { ShopService } from 'src/modules/shops/providers/shops.service';

@Injectable()
export class ProductService {
  constructor(
    private readonly productRepository: ProductRepository,
    private readonly categoryRepository: CategoryRepository,
     private readonly shopService: ShopService,
    private readonly em: EntityManager,
  ) { }

  async create(shopId: string, dto: CreateProductDto) {
    const { categoryId, variants, ...rest } = dto;
    const shop = await this.shopService.findOrFail(shopId);
    if (!shop) {
      throw new NotFoundException(RestMessage.NOT_FOUND);
    }
    const category = await this.categoryRepository.findOne({ id: categoryId, shop: { id: shopId } });
    if (!category) {
      throw new NotFoundException(CategoryMessage.NOT_FOUND);
    }

    const product = await this.em.transactional(async em => {
      // prepare data with defaults for required fields so repository.create typing is satisfied
      const data: RequiredEntityData<Product> = {
        desc: rest.desc,
        isActive: rest.isActive ?? true,
        discount: rest.discount ?? 0,
        isSpecialOffer: rest.isSpecialOffer ?? false,
        order: rest.order ?? null,
        // map single-title/content DTO to localized fields
        title: rest.title,
        attribute: rest.attribute,
        // numeric/array fields
        price: rest.price ?? 0,
        images: rest.images ?? undefined,
        shop: shop,
        category: category,
      };

      const product = em.create(Product, data);

      em.persist(product)

      for (const variant of variants) {
        const variantRecord = em.create(Variant, {
          product,
          value: variant.value,
          stock: variant.stock,
          price: variant.price,
        })

        em.persist(variantRecord)
      }

      await em.flush();
      return product;
    });



    return product;
  }

  findAll(restId: string, dto: FindProductsDto) {
    return this.productRepository.findAllPaginated(restId, dto);
  }


  async findPublicById(productId: string, userId?: string): Promise<any> {

    const product = await this.findOrFail(productId)

    let isFavorite = false;
    if (userId) {
      isFavorite = (await this.em.count(Favorite, { user: { id: userId }, product: { id: productId } })) > 0;
    }
    return {
      ...product,
      isFavorite,
    };
  }


  async findAdminById(shopId: string, productId: string): Promise<Product> {
    const product = await this.findOrFail(productId)

    if (product.shop.id !== shopId) throw new NotFoundException(ProductMessage.NOT_FOUND);
    return product;
  }


  async findByShop(slug: string): Promise<Product[]> {
    const shop = await this.shopService.findOrFailBySlug( slug );

    const queryFilter: FilterQuery<Product> = {
      shop: { slug },
      isActive: true,
    } as unknown as FilterQuery<Product>;

    return this.productRepository.find(queryFilter, {
      populate: ['category'],
      orderBy: { order: 'asc' }
    });
  }

  async update(restId: string, productId: string, dto: Partial<CreateProductDto>): Promise<Product> {
    const { categoryId, variants, ...rest } = dto;

    const product = await this.findOrFail(productId)

    // attach new categories if provided (adds, does not attempt to preserve/remove existing ones)
    if (categoryId) {
      const category = await this.categoryRepository.findOne({ id: categoryId, shop: { id: restId } });

      if (!category) {
        throw new NotFoundException(CategoryMessage.NOT_FOUND);
      }

      this.em.assign(product, { category: category });
    }

    if (variants) {
      // Get existing variants for this product
      const existingVariants = product.variants

      // Create a map of existing variants by id for easy lookup
      const existingVariantsMap = new Map(existingVariants.map((v: any) => [v.id, v]));

      // Track which existing variants are being updated (to avoid deletion)
      const updatedVariantIds = new Set<string>();

      for (const variant of variants) {
        const { id, value, stock, price } = variant;

        if (id) {
          // Update existing variant
          const existingVariant = existingVariantsMap.get(id);
          if (!existingVariant) {
            throw new NotFoundException('Variant not found');
          }

          // Update the variant fields
          this.em.assign(existingVariant, { value, stock, price });
          updatedVariantIds.add(id);
        } else {
          // Create new variant
          const variantRecord = this.em.create(Variant, {
            product,
            value,
            stock,
            price,
          });
          this.em.persist(variantRecord);
        }
      }

      // Delete variants that exist but were not included in the update
      for (const existingVariant of existingVariants) {
        if (!updatedVariantIds.has((existingVariant as any).id)) {
          this.em.remove(existingVariant);
        }
      }
    }
    // assign other fields from DTO (excluding dailyStock handled below)
    this.em.assign(product, rest);

    await this.em.persistAndFlush(product);


    return product;
  }

  async remove(restId: string, id: string): Promise<void> {
    const product = await this.findOrFail(id)

    if (product.shop.id !== restId) {
      throw new BadRequestException("Product doesnt belongs to you")
    }

    product.deletedAt = new Date();

    await this.em.flush();

  }


  async toggleFavorite(userId: string, productId: string) {

    const favorite = await this.em.findOne(Favorite, { user: userId, product: productId });
    if (favorite) {
      return this.em.removeAndFlush(favorite);
    }
    const newFavorite = this.em.create(Favorite, {
      user: userId,
      product: productId,
    });
    return this.em.persistAndFlush(newFavorite);
  }


  async getMyFavorites(userId: string, restId: string) {
    return this.em.find(Favorite, { user: userId, product: { shop: { id: restId } } }, { populate: ['product'] });
  }
  /**
   * Helper
   */
  async findOrFail(productId: string) {
    const product = await this.productRepository.findOne({ id: productId, isActive: true },
      { populate: ['category', 'variants', 'shop'] });

    if (!product) throw new NotFoundException(ProductMessage.NOT_FOUND);

    return product
  }
}