/**
 * CartService - Gestión de carritos de compra
 * @module Ecommerce
 */

import { Repository, DeepPartial } from 'typeorm';
import { AppDataSource } from '../../../config/typeorm';
import { Cart, CartStatus } from '../entities/cart.entity';
import { CartItem } from '../entities/cart-item.entity';

interface ServiceResult<T> {
  success: boolean;
  data?: T;
  error?: { code: string; message: string };
}

interface AddItemDTO {
  productId: string;
  productCode: string;
  productName: string;
  productSlug?: string;
  productImage?: string;
  variantId?: string;
  variantName?: string;
  variantSku?: string;
  variantOptions?: { name: string; value: string }[];
  quantity: number;
  unitPrice: number;
  originalPrice: number;
  taxRate?: number;
  taxIncluded?: boolean;
  warehouseId?: string;
}

interface UpdateItemDTO {
  quantity?: number;
  savedForLater?: boolean;
  notes?: string;
}

interface ApplyCouponDTO {
  couponId: string;
  couponCode: string;
  discountAmount: number;
}

interface SetShippingDTO {
  shippingMethodId: string;
  shippingMethodName: string;
  shippingAmount: number;
  shippingAddress: Cart['shippingAddress'];
}

interface SetBillingDTO {
  billingAddress: Cart['billingAddress'];
  billingSameAsShipping?: boolean;
  requiresInvoice?: boolean;
  invoiceRfc?: string;
  invoiceUsoCfdi?: string;
}

class CartService {
  private repository: Repository<Cart>;
  private itemRepository: Repository<CartItem>;

  constructor() {
    this.repository = AppDataSource.getRepository(Cart);
    this.itemRepository = AppDataSource.getRepository(CartItem);
  }

  /**
   * Get or create cart for customer/session
   */
  async getOrCreateCart(
    tenantId: string,
    options: { customerId?: string; sessionId?: string }
  ): Promise<ServiceResult<Cart>> {
    try {
      let cart: Cart | null = null;

      if (options.customerId) {
        cart = await this.repository.findOne({
          where: { tenantId, customerId: options.customerId, status: CartStatus.ACTIVE },
          relations: ['items'],
        });
      } else if (options.sessionId) {
        cart = await this.repository.findOne({
          where: { tenantId, sessionId: options.sessionId, status: CartStatus.ACTIVE },
          relations: ['items'],
        });
      }

      if (!cart) {
        cart = this.repository.create({
          tenantId,
          customerId: options.customerId,
          sessionId: options.sessionId,
          status: CartStatus.ACTIVE,
          currencyCode: 'MXN',
        });
        cart = await this.repository.save(cart);
      }

      return { success: true, data: cart };
    } catch (error: any) {
      return { success: false, error: { code: 'CART_ERROR', message: error.message } };
    }
  }

  /**
   * Get cart by ID
   */
  async getById(tenantId: string, id: string): Promise<ServiceResult<Cart>> {
    try {
      const cart = await this.repository.findOne({
        where: { id, tenantId },
        relations: ['items'],
      });

      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      return { success: true, data: cart };
    } catch (error: any) {
      return { success: false, error: { code: 'CART_ERROR', message: error.message } };
    }
  }

  /**
   * Add item to cart
   */
  async addItem(tenantId: string, cartId: string, data: AddItemDTO): Promise<ServiceResult<CartItem>> {
    try {
      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      // Check if item already exists
      let item = await this.itemRepository.findOne({
        where: {
          tenantId,
          cartId,
          productId: data.productId,
          variantId: data.variantId || undefined,
        },
      });

      if (item) {
        // Update quantity
        item.quantity = Number(item.quantity) + data.quantity;
      } else {
        // Create new item
        item = this.itemRepository.create({
          tenantId,
          cartId,
          ...data,
          taxRate: data.taxRate ?? 0.16,
          taxIncluded: data.taxIncluded ?? true,
        });
      }

      // Calculate totals
      this.calculateItemTotals(item);
      item = await this.itemRepository.save(item);

      // Recalculate cart totals
      await this.recalculateCartTotals(tenantId, cartId);

      return { success: true, data: item };
    } catch (error: any) {
      return { success: false, error: { code: 'ADD_ITEM_ERROR', message: error.message } };
    }
  }

  /**
   * Update cart item
   */
  async updateItem(tenantId: string, cartId: string, itemId: string, data: UpdateItemDTO): Promise<ServiceResult<CartItem>> {
    try {
      const item = await this.itemRepository.findOne({
        where: { id: itemId, tenantId, cartId },
      });

      if (!item) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Item not found' } };
      }

      if (data.quantity !== undefined) {
        if (data.quantity <= 0) {
          // Remove item
          await this.itemRepository.remove(item);
          await this.recalculateCartTotals(tenantId, cartId);
          return { success: true, data: item };
        }
        item.quantity = data.quantity;
      }

      if (data.savedForLater !== undefined) {
        item.savedForLater = data.savedForLater;
      }

      if (data.notes !== undefined) {
        item.notes = data.notes;
      }

      this.calculateItemTotals(item);
      const updatedItem = await this.itemRepository.save(item);
      await this.recalculateCartTotals(tenantId, cartId);

      return { success: true, data: updatedItem };
    } catch (error: any) {
      return { success: false, error: { code: 'UPDATE_ERROR', message: error.message } };
    }
  }

  /**
   * Remove item from cart
   */
  async removeItem(tenantId: string, cartId: string, itemId: string): Promise<ServiceResult<void>> {
    try {
      const item = await this.itemRepository.findOne({
        where: { id: itemId, tenantId, cartId },
      });

      if (!item) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Item not found' } };
      }

      await this.itemRepository.remove(item);
      await this.recalculateCartTotals(tenantId, cartId);

      return { success: true };
    } catch (error: any) {
      return { success: false, error: { code: 'REMOVE_ERROR', message: error.message } };
    }
  }

  /**
   * Apply coupon to cart
   */
  async applyCoupon(tenantId: string, cartId: string, data: ApplyCouponDTO): Promise<ServiceResult<Cart>> {
    try {
      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      cart.couponId = data.couponId;
      cart.couponCode = data.couponCode;
      cart.couponDiscount = data.discountAmount;

      await this.repository.save(cart);
      await this.recalculateCartTotals(tenantId, cartId);

      const updatedCart = await this.repository.findOne({
        where: { id: cartId, tenantId },
        relations: ['items'],
      });

      return { success: true, data: updatedCart! };
    } catch (error: any) {
      return { success: false, error: { code: 'COUPON_ERROR', message: error.message } };
    }
  }

  /**
   * Remove coupon from cart
   */
  async removeCoupon(tenantId: string, cartId: string): Promise<ServiceResult<Cart>> {
    try {
      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      cart.couponId = null as any;
      cart.couponCode = null as any;
      cart.couponDiscount = 0;

      await this.repository.save(cart);
      await this.recalculateCartTotals(tenantId, cartId);

      const updatedCart = await this.repository.findOne({
        where: { id: cartId, tenantId },
        relations: ['items'],
      });

      return { success: true, data: updatedCart! };
    } catch (error: any) {
      return { success: false, error: { code: 'COUPON_ERROR', message: error.message } };
    }
  }

  /**
   * Set shipping information
   */
  async setShipping(tenantId: string, cartId: string, data: SetShippingDTO): Promise<ServiceResult<Cart>> {
    try {
      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      cart.shippingMethodId = data.shippingMethodId;
      cart.shippingMethodName = data.shippingMethodName;
      cart.shippingAmount = data.shippingAmount;
      cart.shippingAddress = data.shippingAddress;

      await this.repository.save(cart);
      await this.recalculateCartTotals(tenantId, cartId);

      const updatedCart = await this.repository.findOne({
        where: { id: cartId, tenantId },
        relations: ['items'],
      });

      return { success: true, data: updatedCart! };
    } catch (error: any) {
      return { success: false, error: { code: 'SHIPPING_ERROR', message: error.message } };
    }
  }

  /**
   * Set billing information
   */
  async setBilling(tenantId: string, cartId: string, data: SetBillingDTO): Promise<ServiceResult<Cart>> {
    try {
      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      cart.billingAddress = data.billingAddress;
      cart.billingSameAsShipping = data.billingSameAsShipping ?? false;
      cart.requiresInvoice = data.requiresInvoice ?? false;
      if (data.invoiceRfc) cart.invoiceRfc = data.invoiceRfc;
      if (data.invoiceUsoCfdi) cart.invoiceUsoCfdi = data.invoiceUsoCfdi;

      const updatedCart = await this.repository.save(cart);

      return { success: true, data: updatedCart };
    } catch (error: any) {
      return { success: false, error: { code: 'BILLING_ERROR', message: error.message } };
    }
  }

  /**
   * Merge guest cart into customer cart
   */
  async mergeCarts(tenantId: string, guestSessionId: string, customerId: string): Promise<ServiceResult<Cart>> {
    try {
      const guestCart = await this.repository.findOne({
        where: { tenantId, sessionId: guestSessionId, status: CartStatus.ACTIVE },
        relations: ['items'],
      });

      if (!guestCart || guestCart.items.length === 0) {
        const customerResult = await this.getOrCreateCart(tenantId, { customerId });
        return customerResult;
      }

      let customerCart = await this.repository.findOne({
        where: { tenantId, customerId, status: CartStatus.ACTIVE },
        relations: ['items'],
      });

      if (!customerCart) {
        // Transfer guest cart to customer
        guestCart.customerId = customerId;
        guestCart.sessionId = null as any;
        const updatedCart = await this.repository.save(guestCart);
        return { success: true, data: updatedCart };
      }

      // Merge items
      for (const guestItem of guestCart.items) {
        const existingItem = customerCart.items.find(
          (i) => i.productId === guestItem.productId && i.variantId === guestItem.variantId
        );

        if (existingItem) {
          existingItem.quantity = Number(existingItem.quantity) + Number(guestItem.quantity);
          this.calculateItemTotals(existingItem);
          await this.itemRepository.save(existingItem);
        } else {
          guestItem.cartId = customerCart.id;
          await this.itemRepository.save(guestItem);
        }
      }

      // Mark guest cart as merged
      guestCart.status = CartStatus.MERGED;
      guestCart.mergedIntoCartId = customerCart.id;
      await this.repository.save(guestCart);

      await this.recalculateCartTotals(tenantId, customerCart.id);

      const mergedCart = await this.repository.findOne({
        where: { id: customerCart.id, tenantId },
        relations: ['items'],
      });

      return { success: true, data: mergedCart! };
    } catch (error: any) {
      return { success: false, error: { code: 'MERGE_ERROR', message: error.message } };
    }
  }

  /**
   * Clear cart (remove all items)
   */
  async clearCart(tenantId: string, cartId: string): Promise<ServiceResult<Cart>> {
    try {
      await this.itemRepository.delete({ tenantId, cartId });

      const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
      if (!cart) {
        return { success: false, error: { code: 'NOT_FOUND', message: 'Cart not found' } };
      }

      cart.itemsCount = 0;
      cart.itemsQuantity = 0;
      cart.subtotal = 0;
      cart.taxAmount = 0;
      cart.discountAmount = 0;
      cart.total = 0;

      const updatedCart = await this.repository.save(cart);
      return { success: true, data: updatedCart };
    } catch (error: any) {
      return { success: false, error: { code: 'CLEAR_ERROR', message: error.message } };
    }
  }

  /**
   * Mark cart as abandoned
   */
  async markAbandoned(tenantId: string, cartId: string): Promise<ServiceResult<void>> {
    try {
      await this.repository.update(
        { id: cartId, tenantId, status: CartStatus.ACTIVE },
        { status: CartStatus.ABANDONED }
      );
      return { success: true };
    } catch (error: any) {
      return { success: false, error: { code: 'UPDATE_ERROR', message: error.message } };
    }
  }

  /**
   * Calculate item totals
   */
  private calculateItemTotals(item: CartItem): void {
    const lineSubtotal = Number(item.quantity) * Number(item.unitPrice);
    const discountAmount = Number(item.discountAmount) || lineSubtotal * (Number(item.discountPercent) / 100);
    const afterDiscount = lineSubtotal - discountAmount;

    let taxAmount: number;
    if (item.taxIncluded) {
      taxAmount = afterDiscount - afterDiscount / (1 + Number(item.taxRate));
    } else {
      taxAmount = afterDiscount * Number(item.taxRate);
    }

    item.subtotal = Number((afterDiscount - (item.taxIncluded ? taxAmount : 0)).toFixed(2));
    item.taxAmount = Number(taxAmount.toFixed(2));
    item.total = Number((afterDiscount + (item.taxIncluded ? 0 : taxAmount)).toFixed(2));
  }

  /**
   * Recalculate cart totals
   */
  private async recalculateCartTotals(tenantId: string, cartId: string): Promise<void> {
    const items = await this.itemRepository.find({
      where: { tenantId, cartId, savedForLater: false },
    });

    const cart = await this.repository.findOne({ where: { id: cartId, tenantId } });
    if (!cart) return;

    let itemsCount = 0;
    let itemsQuantity = 0;
    let subtotal = 0;
    let taxAmount = 0;

    for (const item of items) {
      itemsCount++;
      itemsQuantity += Number(item.quantity);
      subtotal += Number(item.subtotal);
      taxAmount += Number(item.taxAmount);
    }

    cart.itemsCount = itemsCount;
    cart.itemsQuantity = itemsQuantity;
    cart.subtotal = Number(subtotal.toFixed(2));
    cart.taxAmount = Number(taxAmount.toFixed(2));
    cart.discountAmount = Number(cart.couponDiscount) + items.reduce((sum, i) => sum + Number(i.discountAmount), 0);

    const total = subtotal + taxAmount + Number(cart.shippingAmount) - Number(cart.couponDiscount) - Number(cart.loyaltyPointsValue);
    cart.total = Number(Math.max(0, total).toFixed(2));

    await this.repository.save(cart);
  }
}

export const cartService = new CartService();
export { CartService };