import {
  BadRequestException,
  Injectable,
  NotFoundException,
} from '@nestjs/common'
import { randomInt } from 'crypto'
import type { Prisma, InviteReferral, InviteRewardGrant } from '@prisma/client'
import { InviteReferralStatus, MembershipStatus, OrderStatus } from '@mp-pilates/shared'
import type { InviteActivitySummary } from '@mp-pilates/shared'
import { PrismaService } from '../prisma/prisma.service'
import {
  INVITE_REWARD_REQUIRED_COUNT,
  INVITE_REWARD_TIMES,
} from './invite.constants'

@Injectable()
export class InviteService {
  constructor(private readonly prisma: PrismaService) {}

  private isTrialCardType(type: string): boolean {
    return type === 'TRIAL'
  }

  async bindInviterToUser(inviteeId: string, inviterId?: string | null): Promise<void> {
    if (!inviterId || inviterId === inviteeId) {
      return
    }

    const [inviter, inviteeMembershipCount, existingReferral] = await Promise.all([
      this.prisma.user.findUnique({ where: { id: inviterId }, select: { id: true } }),
      this.prisma.membership.count({ where: { userId: inviteeId } }),
      this.prisma.inviteReferral.findUnique({ where: { inviteeId } }),
    ])

    if (!inviter || inviteeMembershipCount > 0 || existingReferral) {
      return
    }

    await this.prisma.inviteReferral.create({
      data: {
        inviterId,
        inviteeId,
      },
    })
  }

  async recordTrialOrderPaid(orderId: string): Promise<void> {
    const order = await this.prisma.order.findUnique({
      where: { id: orderId },
      include: {
        cardType: true,
        user: { select: { id: true } },
      },
    })

    if (!order || order.status !== OrderStatus.PAID || !this.isTrialCardType(order.cardType.type)) {
      return
    }

    await this.prisma.inviteReferral.updateMany({
      where: {
        inviteeId: order.user.id,
        status: InviteReferralStatus.REGISTERED,
        trialOrderId: null,
      },
      data: {
        status: InviteReferralStatus.TRIAL_PURCHASED,
        trialOrderId: order.id,
        trialPurchasedAt: order.paidAt ?? new Date(),
      },
    })
  }

  // Legacy booking callbacks must never qualify trial purchases.
  async recordQualifiedTrialBooking(_bookingId: string): Promise<void> {}

  async ensureCode(userId: string): Promise<string> {
    for (let attempt = 0; attempt < 12; attempt++) {
      const user = await this.prisma.user.findUniqueOrThrow({ where: { id: userId } })
      if (user.inviteCode) return user.inviteCode
      const alphabet = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ'
      const code = Array.from({ length: 6 }, () => alphabet[randomInt(alphabet.length)]).join('')
      try {
        const updated = await this.prisma.user.updateMany({
          where: { id: userId, inviteCode: null }, data: { inviteCode: code },
        })
        if (updated.count) return code
      } catch (error) {
        if ((error as { code?: string }).code !== 'P2002') throw error
      }
    }
    throw new BadRequestException('邀请码生成繁忙，请重试')
  }

  async getCodeStatus(userId: string) {
    const inviteCode = await this.ensureCode(userId)
    const referral = await this.prisma.inviteReferral.findUnique({ where: { inviteeId: userId } })
    return { inviteCode, discountEligible: !!referral }
  }

  async confirmCode(userId: string, code: string) {
    const inviter = await this.prisma.user.findUnique({ where: { inviteCode: code.toUpperCase() } })
    if (!inviter) throw new BadRequestException('邀请码不存在，请检查后重试')
    if (inviter.id === userId) throw new BadRequestException('不能使用自己的邀请码')
    let referral: InviteReferral | null
    try {
      referral = await this.prisma.inviteReferral.upsert({
        where: { inviteeId: userId }, update: {},
        create: { inviterId: inviter.id, inviteeId: userId },
      })
    } catch (error) {
      // MySQL upserts may race on the unique invitee key. Read the winner.
      if ((error as { code?: string }).code !== 'P2002') throw error
      referral = await this.prisma.inviteReferral.findUnique({ where: { inviteeId: userId } })
      if (!referral) throw error
    }
    if (referral.inviterId !== inviter.id) throw new BadRequestException('你已绑定其他好友的邀请码，已享有 95 折优惠')
    return this.getCodeStatus(userId)
  }

  async rewardPaidOrder(tx: Prisma.TransactionClient, order: { userId: string; inviteInviterId: string | null; purchasedCategory: string | null }, now: Date) {
    if (!order.inviteInviterId || !order.purchasedCategory || order.purchasedCategory === 'TRIAL') return
    const claimed = await tx.inviteReferral.updateMany({
      where: { inviteeId: order.userId, inviterId: order.inviteInviterId, status: { not: 'QUALIFIED' } },
      data: { status: 'QUALIFIED', qualifiedAt: now },
    })
    if (!claimed.count) return
    const membership = await tx.membership.create({ data: {
      userId: order.inviteInviterId, cardTypeId: 'invite-reward-card',
      remainingTimes: 1, totalTimes: 1, startDate: now,
      expireDate: new Date(now.getTime() + 365 * 86400000), status: 'ACTIVE',
    } })
    await tx.inviteRewardGrant.create({ data: {
      inviterId: order.inviteInviterId, membershipId: membership.id,
      qualifiedReferralCount: 1, rewardTimes: 1,
    } })
  }

  async getInviteActivitySummary(userId: string): Promise<InviteActivitySummary> {
    const referrals = await this.prisma.inviteReferral.findMany({
      where: { inviterId: userId },
      include: {
        invitee: {
          select: {
            id: true,
            nickname: true,
            avatarUrl: true,
          },
        },
      },
      orderBy: { createdAt: 'desc' },
    })
    const rewardGrants = await this.prisma.inviteRewardGrant.findMany({
      where: { inviterId: userId },
      orderBy: { grantedAt: 'desc' },
    })

    const canInvite = true
    const qualifiedInviteCount = referrals.filter((item: InviteReferral) => item.status === InviteReferralStatus.QUALIFIED).length
    const rewardedTimes = rewardGrants.reduce((sum: number, item: InviteRewardGrant) => sum + item.rewardTimes, 0)
    const pendingRewardGrantCount = Math.max(
      0,
      qualifiedInviteCount - rewardGrants.length * INVITE_REWARD_REQUIRED_COUNT,
    )
    const currentCycleQualifiedCount = qualifiedInviteCount % INVITE_REWARD_REQUIRED_COUNT

    return {
      inviterId: userId,
      canInvite,
      sharePath: `/pages/card/detail?showAll=1&inviteCode=${await this.ensureCode(userId)}`,
      rewardRuleInvitesRequired: INVITE_REWARD_REQUIRED_COUNT,
      rewardRuleTimes: INVITE_REWARD_TIMES,
      qualifiedInviteCount,
      rewardedTimes,
      pendingRewardGrantCount,
      pendingInviteCount: referrals.filter((item: InviteReferral) => item.status !== InviteReferralStatus.QUALIFIED).length,
      currentCycleQualifiedCount,
      nextRewardRemainingCount: currentCycleQualifiedCount === 0
        ? INVITE_REWARD_REQUIRED_COUNT
        : INVITE_REWARD_REQUIRED_COUNT - currentCycleQualifiedCount,
      referrals: referrals.map((item: InviteReferral & { invitee: { nickname: string; avatarUrl: string | null } }) => ({
        id: item.id,
        inviteeId: item.inviteeId,
        inviteeNickname: item.invitee.nickname,
        inviteeAvatarUrl: item.invitee.avatarUrl,
        status: item.status as InviteReferralStatus,
        invitedAt: item.invitedAt.toISOString(),
        trialPurchasedAt: item.trialPurchasedAt?.toISOString() ?? null,
        qualifiedAt: item.qualifiedAt?.toISOString() ?? null,
      })),
      rewardGrants: rewardGrants.map((item: InviteRewardGrant) => ({
        id: item.id,
        membershipId: item.membershipId,
        qualifiedReferralCount: item.qualifiedReferralCount,
        rewardTimes: item.rewardTimes,
        grantedAt: item.grantedAt.toISOString(),
      })),
    }
  }

  async validateInviterForTrialOrder(userId: string, inviterId?: string): Promise<void> {
    if (!inviterId) {
      return
    }

    if (inviterId === userId) {
      throw new BadRequestException('不能邀请自己购买体验课')
    }

    const referral = await this.prisma.inviteReferral.findFirst({
      where: {
        inviterId,
        inviteeId: userId,
      },
    })

    if (!referral) {
      throw new NotFoundException('邀请关系不存在或已失效')
    }
  }

}