import { randomBytes } from "node:crypto";

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

import { ReferralMessage, UserMessage } from "../../../common/enums/message.enum";
import { User } from "../../users/entities/user.entity";
import { UseReferralCodeDto } from "../DTO/use-referral-code.dto";
import { ReferralStatus } from "../enums/referral-status.enum";
import { ReferralCodesRepository } from "../repositories/referral-codes.repository";
import { ReferralRewardsRepository } from "../repositories/referral-rewards.repository";
import { ReferralsRepository } from "../repositories/referrals.repository";
@Injectable()
export class ReferralsService {
  private MAX_ATTEMPTS = 10;
  constructor(
    private readonly referralsRepository: ReferralsRepository,
    private readonly referralCodesRepository: ReferralCodesRepository,
    private readonly referralRewardsRepository: ReferralRewardsRepository,
  ) {}

  async generateReferralCode(userId: string, queryRunner: QueryRunner) {
    const existReferralCode = await queryRunner.manager.findOneBy(this.referralCodesRepository.target, { user: { id: userId } });

    if (existReferralCode) throw new BadRequestException(ReferralMessage.CODE_EXIST_FOR_USER);

    let attempts = 0;
    let code: string;
    let existCode;

    do {
      if (attempts >= this.MAX_ATTEMPTS) {
        throw new BadRequestException(ReferralMessage.CODE_GENERATION_FAILED);
      }

      code = this.generateRandomCode();
      existCode = await queryRunner.manager.findOneBy(this.referralCodesRepository.target, { code });
      attempts++;
    } while (existCode);

    const referralCode = queryRunner.manager.create(this.referralCodesRepository.target, {
      code,
      user: { id: userId },
    });

    await queryRunner.manager.save(referralCode);
    return code;
  }

  //*********************************** */
  async useReferralCode(dto: UseReferralCodeDto, queryRunner: QueryRunner) {
    const referredUser = await queryRunner.manager.findOne(User, { where: { id: dto.userId } });
    if (!referredUser) throw new BadRequestException(UserMessage.USER_NOT_FOUND);

    const referralCode = await queryRunner.manager.findOne(this.referralCodesRepository.target, {
      where: { code: dto.referralCode, isActive: true },
      relations: { user: true },
    });
    if (!referralCode || !referralCode.user) throw new BadRequestException(ReferralMessage.INVALID_OR_INACTIVE_REFERRAL_CODE);

    const existingReferral = await queryRunner.manager.findOne(this.referralsRepository.target, {
      where: { referredUser: { id: referredUser.id } },
    });
    if (existingReferral) throw new BadRequestException(ReferralMessage.USER_ALREADY_REFERRED);

    const referral = queryRunner.manager.create(this.referralsRepository.target, {
      referrer: { id: referralCode.user.id },
      referredUser: { id: referredUser.id },
      referralCode: { id: referralCode.id },
    });

    await queryRunner.manager.save(referral);

    referralCode.usedCount += 1;
    await queryRunner.manager.save(referralCode);

    // const reward = queryRunner.manager.create(this.referralRewardsRepository.target, {
    //   user: { id: referralCode.user.id },
    //   referral: { id: referral.id },
    // });

    // await queryRunner.manager.save(reward);

    return referral;
  }

  //*********************************** */
  async getPendingReferral(userId: string, queryRunner: QueryRunner) {
    return queryRunner.manager.findOne(this.referralsRepository.target, {
      where: {
        referredUser: { id: userId },
        status: ReferralStatus.PENDING,
      },
      relations: { referrer: true },
    });
  }
  //*********************************** */

  async createReferral(userId: string, queryRunner: QueryRunner) {
    const referral = queryRunner.manager.create(this.referralsRepository.target, {
      referrer: { id: userId },
      referredUser: { id: userId },
    });
    await queryRunner.manager.save(referral);
  }

  //*********************************** */

  async createReferralReward(userId: string, referralId: string, amount: Decimal, queryRunner: QueryRunner) {
    const reward = queryRunner.manager.create(this.referralRewardsRepository.target, {
      user: { id: userId },
      referral: { id: referralId },
      amount,
    });
    await queryRunner.manager.save(reward);

    return reward;
  }

  //*********************************** */
  private generateRandomCode(): string {
    return randomBytes(6).toString("hex");
  }
}