import { BadRequestException, Injectable } from "@nestjs/common";
import dayjs from "dayjs";
import Decimal from "decimal.js";

import { SubscriptionMessage } from "../../../common/enums/message.enum";
import { InvoicesService } from "../../invoices/providers/invoices.service";
import { UserSubscription } from "../../subscriptions/entities/user-subscription.entity";
import { UserSubscriptionsRepository } from "../../subscriptions/repositories/user-subscriptions.repository";
import { BuyPremiumPlanDto } from "../DTO/buy-premium-plan.dto";

@Injectable()
export class PremiumService {
  constructor(
    private readonly userSubscriptionsRepository: UserSubscriptionsRepository,
    private readonly invoicesService: InvoicesService,
  ) {}

  async buyPremiumPlan(dto: BuyPremiumPlanDto, userId: string) {
    // Find the user's current subscription
    const userSubscription = await this.userSubscriptionsRepository.findOne({
      where: { id: dto.userSubscriptionId, user: { id: userId } },
      relations: {
        user: true,
        plan: { service: true },
      },
    });

    if (!userSubscription) {
      throw new BadRequestException(SubscriptionMessage.NOT_FOUND);
    }

    // Calculate remaining days
    const remainingDays = this.calculateRemainingDays(userSubscription);

    // Extract duration from current plan and convert to months
    const planDurationInMonths = Math.round(userSubscription.plan.duration / 30);

    // Get premium pricing based on extracted duration
    const premiumPrice = this.getPremiumPrice(planDurationInMonths);

    // Create invoice items for premium purchase
    const invoiceItems = [{
      name: `Premium Plan - ${planDurationInMonths} Months`,
      count: 1,
      unitPrice: premiumPrice.toNumber(),
      discount: 0,
    }];

    // Create invoice directly
    const createInvoiceDto = {
      userId: userSubscription.user.id,
      items: invoiceItems,
      isRecurring: false,
    };

    const invoice = await this.invoicesService.createInvoiceAdmin(createInvoiceDto, {
      ip: '',
      headers: {},
      userId: userSubscription.user.id
    });

    return {
      message: "Premium plan purchased successfully",
      userSubscription,
      invoice,
      remainingDays,
      premiumPrice: premiumPrice.toNumber(),
    };
  }

  //************************************ */
  private calculateRemainingDays(userSubscription: UserSubscription): number {
    const now = dayjs();
    const endDate = dayjs(userSubscription.endDate);

    if (endDate.isBefore(now)) {
      return 0;
    }

    return endDate.diff(now, 'day');
  }

  //************************************ */
  private getPremiumPrice(durationInMonths: number): Decimal {
    switch (durationInMonths) {
      case 6:
        return new Decimal(5000000);
      case 12:
        return new Decimal(10000000);
      default:
        throw new BadRequestException("Invalid premium plan duration. Only 6 and 12 month plans are supported.");
    }
  }
}