import { inject, injectable } from "inversify";
import { ClientSession, Types, startSession } from "mongoose";

import { CartRepository, CartShipItemRepo } from "./cart.repository";
import { AddToCartDTO } from "./DTO/addToCart.dto";
import { BulkAddToCartDTO } from "./DTO/bulkAddToCart.dto";
import { CartDTO } from "./DTO/cart.dto";
import { RemoveFromCartDTO } from "./DTO/removeFromCart.dto";
import { UpdateCartDTO } from "./DTO/updateCart.dto";
import { CartMessage, ProductMessage } from "../../common/enums/message.enum";
import { BadRequestError, InternalError } from "../../core/app/app.errors";
import { IOCTYPES } from "../../IOC/ioc.types";
import { ICart } from "./models/Abstraction/ICart";
import { IProduct } from "../product/models/Abstraction/IProduct";
import { ProductRepository } from "../product/Repository/product";
import { ProductVariantRepository } from "../product/Repository/productVarinat";

@injectable()
class CartService {
  @inject(IOCTYPES.CartRepository) cartRepo: CartRepository;
  @inject(IOCTYPES.CartShipItemRepo) cartShipItemRepo: CartShipItemRepo;
  @inject(IOCTYPES.ProductRepository) productRepo: ProductRepository;
  @inject(IOCTYPES.ProductVariantRepository) productVariantRepo: ProductVariantRepository;

  async getCartS(userId: string) {
    const doc = (await this.cartRepo.getCartWithAggregate(userId))[0] as ICart;
    if (!doc) {
      throw new BadRequestError(CartMessage.CartNotFound);
    }
    const cart = CartDTO.transformCart(doc);

    const cartShipmentItems = await this.cartShipItemRepo.getCartShipmentItems(doc._id.toString());
    const recommended = await this.getRecommendedProducts(doc);
    return { cart: { ...cart, cartShipmentItems }, recommended };
  }

  async clearCart(userId: string) {
    const deletedCart = await this.cartRepo.model.findOneAndDelete({ user: userId });
    if (!deletedCart) throw new BadRequestError(CartMessage.CartNotFound);
    return {
      message: CartMessage.ItemDeleted,
    };
  }

  async addToCartS(addToCartDto: AddToCartDTO, userId: string) {
    const session = await startSession();
    session.startTransaction();
    try {
      const { productId, variantId } = addToCartDto;

      // Get or create cart
      let cart = await this.cartRepo.model.findOne({ user: userId });
      if (!cart) {
        cart = (await this.cartRepo.model.create([{ user: userId }], { session }))[0];
      }

      const existingCartItem = cart.items.find((item) => item.product === productId && item.variant.toString() === variantId);
      const existingQuantity = existingCartItem ? existingCartItem.quantity : 0;

      await this.validateProduct(productId, variantId, existingQuantity + 1);

      if (existingCartItem) {
        // Update quantity if item already exists in the cart
        existingCartItem.quantity += 1;
      } else {
        // Add new item to the cart
        cart.items.push({ product: productId, quantity: 1, variant: new Types.ObjectId(variantId) });
      }

      await cart.save({ session });

      // Commit the transaction
      await session.commitTransaction();
      session.endSession();

      return {
        message: CartMessage.ItemAdded,
        cart: await this.getCartS(userId),
      };
    } catch (error) {
      // Rollback any changes made in the transaction
      await session.abortTransaction();
      session.endSession();
      throw error; // Re-throw the error to be handled by the calling errorHandler
    }
  }

  async bulkAddToCartS(bulkAddToCartDto: BulkAddToCartDTO, userId: string) {
    const session = await startSession();
    session.startTransaction();
    try {
      const { items } = bulkAddToCartDto;

      // Get or create cart
      let cart = await this.cartRepo.model.findOne({ user: userId });
      if (!cart) {
        cart = (await this.cartRepo.model.create([{ user: userId }], { session }))[0];
      }

      // Validate all products before making any changes
      for (const item of items) {
        const existingCartItem = cart.items.find(
          (cartItem) => cartItem.product === item.productId && cartItem.variant.toString() === item.variantId,
        );
        const existingQuantity = existingCartItem ? existingCartItem.quantity : 0;

        await this.validateProduct(item.productId, item.variantId, existingQuantity + item.quantity);
      }

      // Process each item
      for (const item of items) {
        const existingCartItem = cart.items.find(
          (cartItem) => cartItem.product === item.productId && cartItem.variant.toString() === item.variantId,
        );

        if (existingCartItem) {
          // Update quantity if item already exists in the cart
          existingCartItem.quantity += item.quantity;
        } else {
          // Add new item to the cart
          cart.items.push({
            product: item.productId,
            quantity: item.quantity,
            variant: new Types.ObjectId(item.variantId),
          });
        }
      }

      await cart.save({ session });

      // Commit the transaction
      await session.commitTransaction();
      session.endSession();

      return {
        message: CartMessage.ItemAdded,
        cart: await this.getCartS(userId),
      };
    } catch (error) {
      // Rollback any changes made in the transaction
      await session.abortTransaction();
      session.endSession();
      throw error; // Re-throw the error to be handled by the calling errorHandler
    }
  }

  async updateCartS(updateCartDto: UpdateCartDTO, userId: string) {
    const { productId, variantId, quantity } = updateCartDto;

    const cart = await this.cartRepo.model.findOne({ user: userId });
    if (!cart) throw new BadRequestError(CartMessage.CartNotFound);

    const existItem = cart.items.find((item) => item.product === productId && item.variant.toString() === variantId.toString());
    if (!existItem) throw new BadRequestError(CartMessage.ItemNotFound);

    // validate the stock
    await this.validateProduct(productId, variantId, quantity);

    // update the quantity
    existItem.quantity = quantity;
    await cart.save();

    return {
      message: CartMessage.CartUpdated,
      cart: await this.getCartS(userId),
    };
  }

  async removeFromCartS(removeFromCartDto: RemoveFromCartDTO, userId: string) {
    const { productId, variantId } = removeFromCartDto;

    await this.validateProduct(productId, variantId);

    // Find the cart for the user
    const cart = await this.cartRepo.model.findOne({ user: userId });
    if (!cart) throw new BadRequestError(CartMessage.CartNotFound);

    // Find the item in the cart
    const itemIndex = cart.items.findIndex((item) => item.product === productId && item.variant.toString() === variantId.toString());
    if (itemIndex === -1) throw new BadRequestError(CartMessage.ItemNotFound);

    // Remove the item from the cart
    cart.items.splice(itemIndex, 1);
    await cart.save();

    return {
      message: CartMessage.ItemDeleted,
      cart: await this.getCartS(userId),
    };
  }

  async clearCartAndShipmentItems(userId: string, session: ClientSession) {
    const cart = await this.cartRepo.model.findOneAndDelete({ user: userId }, { session });

    if (cart) {
      await this.cartShipItemRepo.model.deleteMany({ cart: cart._id }, { session });
    } else {
      throw new InternalError();
    }
  }

  async getRecommendedProducts(cart: ICart) {
    if (!cart) return;
    const items = cart.items as unknown as { product: IProduct }[];

    const productIds = items.map((item) => item.product._id);
    const categoryIds = items.map((item) => item.product.category.toString());
    const tags = items.flatMap((item) => item.product.tags);

    const recommendedProducts = await this.productRepo.getRecommendedProducts(productIds, categoryIds, tags);

    return recommendedProducts;
  }

  ///==============================> helper methods
  // Helper method to check if the product exists and if the stock is sufficient
  private async validateProduct(productId: number, variantId: string, totalQuantity?: number) {
    // Check if product exists
    const product = await this.productRepo.findById(productId);
    if (!product) throw new BadRequestError(ProductMessage.ProductNotFound);

    // Check if product variant exists
    const productVariant = await this.productVariantRepo.findById(variantId);
    if (!productVariant) throw new BadRequestError(ProductMessage.ProductNotFound);

    if (!product.variants.includes(productVariant._id)) throw new BadRequestError(CartMessage.ProductNotBelongToVariant);
    if (productVariant.product !== product._id) throw new BadRequestError(CartMessage.ProductNotBelongToVariant);

    if (totalQuantity && totalQuantity > productVariant.price.order_limit) {
      // Validate order limit
      throw new BadRequestError(CartMessage.OrderLimitExceeded);
    }

    if (totalQuantity && productVariant.stock < totalQuantity) {
      // Validate stock
      throw new BadRequestError(CartMessage.StockNotEnough);
    }

    return {
      product,
      productVariant,
    };
  }
}

export { CartService };