import {
  Injectable,
  NotFoundException,
  BadRequestException,
} from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';
import { PaginationDto } from '../common/dto/pagination.dto';
import { CreateOrderDto } from './dto/create-order.dto';
import { SmsService } from '../common/services/sms.service';

@Injectable()
export class OrdersService {
  constructor(
    private prisma: PrismaService,
    private smsService: SmsService,
  ) {}

  private generateTrackingNumber(): string {
    const date = new Date();
    const dateStr = `${date.getFullYear()}${String(date.getMonth() + 1).padStart(2, '0')}${String(date.getDate()).padStart(2, '0')}`;
    const random = Math.floor(10000 + Math.random() * 90000);
    return `CN-${dateStr}-${random}`;
  }

  async validateCoupon(code: string, cartTotal: number, userId: string) {
    const coupon = await this.prisma.coupon.findUnique({
      where: { code: code.toUpperCase().trim() },
      include: { targets: true },
    });

    if (!coupon || !coupon.isActive) {
      throw new BadRequestException({
        message: 'کد تخفیف معتبر نیست یا منقضی شده است',
        error: 'COUPON_INVALID',
      });
    }

    if (coupon.expiresAt && new Date() > coupon.expiresAt) {
      throw new BadRequestException({
        message: 'کد تخفیف منقضی شده است',
        error: 'COUPON_EXPIRED',
      });
    }

    if (coupon.maxUses && coupon.usedCount >= coupon.maxUses) {
      throw new BadRequestException({
        message: 'ظرفیت استفاده از این کد تخفیف تکمیل شده است',
        error: 'COUPON_LIMIT_REACHED',
      });
    }

    if (coupon.minCartValue && cartTotal < Number(coupon.minCartValue)) {
      throw new BadRequestException({
        message: `حداقل مبلغ سبد خرید برای استفاده از این کد ${Number(coupon.minCartValue).toLocaleString('fa-IR')} تومان است`,
        error: 'COUPON_MIN_CART',
      });
    }

    // Check user-specific targets
    const userTargets = coupon.targets.filter((t) => t.targetType === 'USER');
    if (
      userTargets.length > 0 &&
      !userTargets.some((t) => t.targetId === userId)
    ) {
      throw new BadRequestException({
        message: 'این کد تخفیف برای حساب کاربری شما فعال نیست',
        error: 'COUPON_USER_MISMATCH',
      });
    }

    let discountAmount = 0;
    if (coupon.type === 'percent' || coupon.type === 'PERCENTAGE') {
      discountAmount = (cartTotal * Number(coupon.value)) / 100;
      if (coupon.maxCartValue && discountAmount > Number(coupon.maxCartValue)) {
        discountAmount = Number(coupon.maxCartValue);
      }
    } else {
      discountAmount = Number(coupon.value);
    }

    return {
      couponId: coupon.id,
      code: coupon.code,
      discountAmount: Math.min(discountAmount, cartTotal),
    };
  }

  async create(userId: string, createOrderDto: CreateOrderDto) {
    if (!createOrderDto.items || createOrderDto.items.length === 0) {
      throw new BadRequestException('سبد خرید خالی است');
    }

    // Verify stock and build items
    let cartTotal = 0;
    const orderItems: Array<{ productId: string; quantity: number; unitPrice: number; totalPrice: number }> = [];

    for (const item of createOrderDto.items) {
      const product = await this.prisma.product.findUnique({
        where: { id: item.productId },
      });
      if (!product) {
        throw new NotFoundException(`محصول یافت نشد`);
      }
      const itemPrice = Number(product.priceValue);
      const totalItemPrice = itemPrice * item.quantity;
      cartTotal += totalItemPrice;
      orderItems.push({
        productId: item.productId,
        quantity: item.quantity,
        unitPrice: itemPrice,
        totalPrice: totalItemPrice,
      });
    }

    let discountAmount = 0;
    let couponId: string | undefined = undefined;

    if (createOrderDto.couponCode) {
      const couponResult = await this.validateCoupon(
        createOrderDto.couponCode,
        cartTotal,
        userId,
      );
      discountAmount = couponResult.discountAmount;
      couponId = couponResult.couponId;
    }

    const charityAmount = createOrderDto.charityDonation || 0;
    const finalAmount = Math.max(0, cartTotal - discountAmount) + charityAmount;

    const trackingNumber = this.generateTrackingNumber();

    // Deduct user wallet balance if payment method is wallet
    if (createOrderDto.paymentMethod === 'wallet' && userId) {
      const user = await this.prisma.user.findUnique({ where: { id: userId } });
      if (!user) {
        throw new NotFoundException('کاربر یافت نشد');
      }
      const userBalance = Number(user.walletBalance || 0);
      if (userBalance < finalAmount) {
        throw new BadRequestException(
          'موجودی کیف پول برای پرداخت این سفارش کافی نیست',
        );
      }
      await this.prisma.user.update({
        where: { id: userId },
        data: {
          walletBalance: { decrement: finalAmount },
        },
      });
      await this.prisma.walletTransaction.create({
        data: {
          userId,
          amount: finalAmount,
          type: 'withdrawal',
          status: 'completed',
          description: `پرداخت سفارش ${trackingNumber}`,
        },
      });
    }

    const createdOrder = await this.prisma.order.create({
      data: {
        userId,
        couponId,
        totalAmount: finalAmount,
        charityDonation: charityAmount,
        isRefill: Boolean(createOrderDto.isRefill),
        refillIntervalDays: createOrderDto.refillIntervalDays || 60,
        trackingNumber,
        status: 'processing',
        orderItems: {
          create: orderItems,
        },
      } as any,
      include: {
        orderItems: {
          include: { product: true },
        },
      },
    });

    // Send Order Confirmation SMS
    if (userId) {
      this.prisma.user.findUnique({ where: { id: userId } }).then((user) => {
        if (user && user.mobile) {
          this.smsService.sendOrderConfirmation(
            user.mobile,
            trackingNumber,
            finalAmount.toLocaleString('fa-IR'),
          ).catch(() => {});
        }
      }).catch(() => {});
    }

    return createdOrder;
  }

  async updateStatus(orderId: string, status: string, trackingCode?: string) {
    const order = await this.prisma.order.findUnique({
      where: { id: orderId },
      include: { user: true },
    });

    if (!order) {
      throw new NotFoundException('سفارش یافت نشد');
    }

    const updatedOrder = await this.prisma.order.update({
      where: { id: orderId },
      data: {
        status,
        ...(trackingCode ? { trackingNumber: trackingCode } : {}),
      },
      include: { user: true },
    });

    // Send Shipping SMS with Tracking Code
    const mobile = updatedOrder.user?.mobile;
    const trackingNum = updatedOrder.trackingNumber || trackingCode || '';
    if (status === 'shipped' && mobile && trackingCode) {
      this.smsService.sendShippingNotification(
        mobile,
        trackingNum,
        trackingCode,
      ).catch(() => {});
    }

    return updatedOrder;
  }

  async findAllByUser(userId: string, filters: PaginationDto) {
    const {
      page = 1,
      limit = 10,
      sortBy = 'createdAt',
      sortOrder = 'desc',
    } = filters;
    const skip = (page - 1) * limit;

    const [data, total] = await Promise.all([
      this.prisma.order.findMany({
        where: { userId },
        skip,
        take: limit,
        orderBy: { [sortBy]: sortOrder },
        include: {
          orderItems: { include: { product: true } },
        },
      }),
      this.prisma.order.count({ where: { userId } }),
    ]);

    return {
      data,
      meta: {
        total,
        page,
        lastPage: Math.ceil(total / limit),
        limit,
      },
    };
  }

  async findOne(id: string, userId: string) {
    const order = await this.prisma.order.findFirst({
      where: { id, userId },
      include: {
        orderItems: { include: { product: true } },
      },
    });

    if (!order) {
      throw new NotFoundException('سفارش یافت نشد');
    }
    return order;
  }
}