import { Injectable, BadRequestException } from '@nestjs/common';
import { EntityManager } from '@mikro-orm/postgresql';
import { Product } from 'src/modules/products/entities/product.entity';
import { UserAddress } from 'src/modules/users/entities/user-address.entity';
import { PaymentMethod } from 'src/modules/payments/entities/payment-method.entity';
import { Delivery } from 'src/modules/delivery/entities/delivery.entity';
import { DeliveryMethodEnum } from 'src/modules/delivery/interface/delivery';
import { Order } from 'src/modules/orders/entities/order.entity';
import { OrderStatus } from 'src/modules/orders/interface/order.interface';
import { Cart } from '../interfaces/cart.interface';
import { GeographicUtils } from '../utils/geographic.utils';
import { CartMessage } from 'src/common/enums/message.enum';
import { WalletTransactionRepository } from 'src/modules/users/repositories/wallet-transaction.repository';
import { ProductService } from 'src/modules/products/providers/product.service';
import { ShopService } from 'src/modules/shops/providers/shops.service';
import { DeliveryService } from 'src/modules/delivery/providers/delivery.service';
import { PaymentMethodService } from 'src/modules/payments/services/payment-method.service';
import { Variant } from 'src/modules/products/entities/variant.entity';

@Injectable()
export class CartValidationService {
  constructor(
    private readonly em: EntityManager,
    private readonly walletTransactionRepository: WalletTransactionRepository,
    private readonly productService: ProductService,
    private readonly shopService: ShopService,
    private readonly deliveryService: DeliveryService,
    private readonly paymentMethodService: PaymentMethodService,
  ) { }

  /**
   * Validate product exists and belongs to shop
   */
  async validateAndGetVariant(variantId: string, shopId: string, quantity: number): Promise<Variant> {
    const variant = await this.productService.findOrFailVariant(variantId)

    if (variant.product.shop.id !== shopId) {
      throw new BadRequestException(CartMessage.PRODUCT_NOT_BELONGS_TO_SHOP);
    }

    return variant;
  }


  /**
   * Validate address belongs to user
   */
  validateAddressOwnership(address: UserAddress, userId: string): void {
    if (address.user.id !== userId) {
      throw new BadRequestException(CartMessage.ADDRESS_NOT_BELONGS_TO_USER);
    }
  }

  /**
   * Assert address is inside shop service area
   */
  async assertAddressInsideServiceArea(
    shopId: string,
    latitude?: number | null,
    longitude?: number | null,
  ): Promise<void> {
    if (latitude === undefined || latitude === null || longitude === undefined || longitude === null) {
      throw new BadRequestException(CartMessage.ADDRESS_NO_COORDINATES);
    }

    const shop = await this.shopService.findOrFail(shopId);

    const serviceArea = shop.serviceArea;
    // If no service area is defined, assume service is available everywhere
    if (!serviceArea || !serviceArea.coordinates || !Array.isArray(serviceArea.coordinates)) return;

    // GeoJSON coordinates: [ [ [lng, lat], ... ] ] -> take first ring
    const rings = serviceArea.coordinates;
    if (!rings || rings.length === 0 || !Array.isArray(rings[0])) return;

    const ring = rings[0];
    const point: [number, number] = [Number(longitude), Number(latitude)];

    // Ensure polygon has the correct tuple typing ([lng, lat] pairs)
    const polygon: [number, number][] = ring.map(
      coord => [Number(coord[0] ?? 0), Number(coord[1] ?? 0)] as [number, number],
    );

    if (!GeographicUtils.isPointInPolygon(point, polygon)) {
      throw new BadRequestException(CartMessage.ADDRESS_OUTSIDE_SERVICE_AREA);
    }
  }

  /**
   * Get enabled delivery method or throw if not found or disabled
   */
  async getEnabledDeliveryMethodOrFail(shopId: string, deliveryMethodId: string): Promise<Delivery> {
    const deliveryMethod = await this.deliveryService.findOrFail(shopId, deliveryMethodId)
    if (!deliveryMethod.enabled) {
      throw new BadRequestException(CartMessage.DELIVERY_METHOD_NOT_ENABLED);
    }
    return deliveryMethod;
  }

  /**
   * Assert delivery method matches expected type
   */
  assertDeliveryMethod(actual: DeliveryMethodEnum, expected: DeliveryMethodEnum, message: string): void {
    if (actual !== expected) {
      throw new BadRequestException(message);
    }
  }

  /**
   * Require delivery method ID or throw
   */
  requireDeliveryMethodId(cart: Cart, message: string): string {
    if (!cart.deliveryMethodId) {
      throw new BadRequestException(message);
    }
    return cart.deliveryMethodId;
  }

  /**
   * Get enabled payment method or throw if not found or disabled
   */
  async getEnabledPaymentMethodOrFail(shopId: string, paymentMethodId: string): Promise<PaymentMethod> {
    const paymentMethod = await this.paymentMethodService.findOneOrFail(paymentMethodId)
    if (paymentMethod.shop.id !== shopId) {
      throw new BadRequestException(CartMessage.PAYMENT_METHOD_NOT_BELONGS_TO_SHOP);
    }
    if (!paymentMethod.enabled) {
      throw new BadRequestException(CartMessage.PAYMENT_METHOD_NOT_ENABLED);
    }
    return paymentMethod;
  }

  /**
   * Assert wallet has enough balance
   */
  async assertWalletHasEnoughBalance(userId: string, shopId: string, amount: number): Promise<void> {
    const balance = await this.walletTransactionRepository.getCurrentWalletBalance(userId, shopId);

    if (balance < amount) {
      throw new BadRequestException(CartMessage.WALLET_INSUFFICIENT);
    }
  }

  /**
   * Assert coupon usage limit
   */
  async assertCouponUsageLimit(userId: string, couponId: string, maxUsesPerUser?: number): Promise<void> {
    if (!maxUsesPerUser) return;

    const ordersThatUsedTheCouponCount = await this.em.count(Order, {
      user: { id: userId },
      couponDetail: { couponId: couponId },
      status: { $ne: OrderStatus.CANCELED },
      deletedAt: null,
    });

    if (ordersThatUsedTheCouponCount >= maxUsesPerUser) {
      throw new BadRequestException(CartMessage.COUPON_MAX_USES_REACHED);
    }
  }

  /**
   * Assert coupon matches cart if restricted
   */
  async assertCouponMatchesCartIfRestricted(
    cart: Cart,
    foodCategories?: string[] | null,
    products?: string[] | null,
  ): Promise<void> {
    const categoryRestriction = foodCategories?.filter(Boolean) ?? [];
    const foodRestriction = products?.filter(Boolean) ?? [];
    const hasCategoryRestriction = categoryRestriction.length > 0;
    const hasFoodRestriction = foodRestriction.length > 0;
    if (!hasCategoryRestriction && !hasFoodRestriction) return;

    const foodMap = await this.getFoodsInCartWithCategories(cart);

    for (const item of cart.items) {
      const product = foodMap.get(item.variantId);
      if (!product) continue;

      const matchesCategory = hasCategoryRestriction && product.category && categoryRestriction.includes(product.category.id);
      const matchesFood = hasFoodRestriction && foodRestriction.includes(product.id);
      if (matchesCategory || matchesFood) return;
    }

    throw new BadRequestException(CartMessage.COUPON_CANNOT_BE_APPLIED);
  }

  /**
   * Get products in cart with categories
   */
  async getFoodsInCartWithCategories(cart: Cart): Promise<Map<string, Product>> {
    const productIds = cart.items.map(item => item.variantId);
    if (productIds.length === 0) return new Map();

    const products = await this.em.find(Product, { id: { $in: productIds } }, { populate: ['category'] });
    return new Map(products.map(f => [f.id, f]));
  }



}