'use server'

import prisma from '@/lib/prisma'
import { auth } from '@/auth'
import { SubscriptionTier } from '@prisma/client'
import { VALID_FEATURES, getCurrentPeriodKey } from '@/lib/quota-utils'
import {
  getAllEntitlementsForAdmin,
  invalidateEntitlementCache,
  type SubscriptionTier as TierType,
} from '@/lib/plan-entitlements'
import { logAuditEventAsync } from '@/lib/audit-log'
import { revalidatePath } from 'next/cache'

const BILLING_CONFIG_KEYS = [
  'BILLING_ENABLED',
  'STRIPE_PRICE_PRO_MONTHLY',
  'STRIPE_PRICE_PRO_ANNUAL',
  'STRIPE_PRICE_BUSINESS_MONTHLY',
  'STRIPE_PRICE_BUSINESS_ANNUAL',
] as const

const TIERS: TierType[] = ['BASIC', 'PRO', 'BUSINESS', 'ENTERPRISE']

async function checkAdmin() {
  const session = await auth()
  if (!session?.user?.id || (session.user as { role?: string }).role !== 'ADMIN') {
    throw new Error('Unauthorized: Admin access required')
  }
  return session
}

function assertValidFeature(feature: string) {
  if (!(VALID_FEATURES as readonly string[]).includes(feature)) {
    throw new Error(`Invalid feature: ${feature}`)
  }
}

function assertValidTier(tier: string): asserts tier is TierType {
  if (!TIERS.includes(tier as TierType)) {
    throw new Error(`Invalid tier: ${tier}`)
  }
}

export async function getBillingAdminData() {
  await checkAdmin()
  const { getSystemConfig } = await import('@/lib/config')
  const config = await getSystemConfig()
  const entitlements = await getAllEntitlementsForAdmin()
  const usageOverview = await getUsageOverviewInternal()

  const billingConfig = Object.fromEntries(
    BILLING_CONFIG_KEYS.map((key) => [key, config[key] ?? '']),
  )

  return { entitlements, billingConfig, usageOverview, features: [...VALID_FEATURES], tiers: TIERS }
}

export async function updatePlanEntitlement(
  tier: string,
  feature: string,
  mode: 'unavailable' | 'unlimited' | 'limited',
  limitValue?: number,
) {
  const session = await checkAdmin()
  assertValidTier(tier)
  assertValidFeature(feature)

  if (mode === 'limited') {
    if (limitValue === undefined || !Number.isFinite(limitValue) || limitValue < 0) {
      throw new Error('Limit must be a non-negative number')
    }
  }

  if (mode === 'unavailable') {
    await prisma.planEntitlement.deleteMany({
      where: { tier: tier as SubscriptionTier, feature },
    })
  } else {
    await prisma.planEntitlement.upsert({
      where: {
        tier_feature: {
          tier: tier as SubscriptionTier,
          feature,
        },
      },
      update: {
        limitValue: mode === 'unlimited' ? null : Math.round(limitValue!),
      },
      create: {
        tier: tier as SubscriptionTier,
        feature,
        limitValue: mode === 'unlimited' ? null : Math.round(limitValue!),
      },
    })
  }

  invalidateEntitlementCache()

  await logAuditEventAsync({
    userId: session.user?.id,
    action: 'PLAN_ENTITLEMENT_UPDATED',
    resource: `${tier}:${feature}`,
    metadata: { tier, feature, mode, limitValue: mode === 'limited' ? limitValue : mode },
  })

  revalidatePath('/admin/billing')
  return { success: true }
}

export async function updateBillingConfig(data: Record<string, string>) {
  const session = await checkAdmin()

  const filtered = Object.fromEntries(
    Object.entries(data).filter(([key, value]) =>
      (BILLING_CONFIG_KEYS as readonly string[]).includes(key)
      && value !== ''
      && !value.includes('sk_')
      && !value.includes('whsec_'),
    ),
  )

  if (filtered.BILLING_ENABLED === 'true') {
    const required = [
      'STRIPE_PRICE_PRO_MONTHLY',
      'STRIPE_PRICE_PRO_ANNUAL',
      'STRIPE_PRICE_BUSINESS_MONTHLY',
      'STRIPE_PRICE_BUSINESS_ANNUAL',
    ] as const
    for (const key of required) {
      if (!filtered[key] && !process.env[key]) {
        throw new Error(`Missing ${key} when billing is enabled`)
      }
    }
  }

  const operations = Object.entries(filtered).map(([key, value]) =>
    prisma.systemConfig.upsert({
      where: { key },
      update: { value },
      create: { key, value },
    }),
  )

  await prisma.$transaction(operations)

  await logAuditEventAsync({
    userId: session.user?.id,
    action: 'BILLING_CONFIG_UPDATED',
    resource: 'billing',
    metadata: { keys: Object.keys(filtered) },
  })

  revalidatePath('/admin/billing')
  revalidatePath('/settings/billing')
  return { success: true }
}

async function getUsageOverviewInternal() {
  const period = getCurrentPeriodKey()
  const periodStart = new Date(`${period}-01`)

  const aggregated = await prisma.usageLog.groupBy({
    by: ['feature'],
    where: { periodStart },
    _sum: { requestsCount: true, tokensUsed: true },
    _count: { userId: true },
  })

  const lastSync = await prisma.usageLog.findFirst({
    where: { periodStart },
    orderBy: { syncedAt: 'desc' },
    select: { syncedAt: true },
  })

  const topUsers = await prisma.usageLog.groupBy({
    by: ['userId'],
    where: { periodStart },
    _sum: { requestsCount: true },
    orderBy: { _sum: { requestsCount: 'desc' } },
    take: 10,
  })

  const userIds = topUsers.map((u) => u.userId)
  const users = userIds.length
    ? await prisma.user.findMany({
        where: { id: { in: userIds } },
        select: { id: true, email: true, name: true },
      })
    : []

  const userMap = Object.fromEntries(users.map((u) => [u.id, u]))

  return {
    period,
    lastSyncedAt: lastSync?.syncedAt?.toISOString() ?? null,
    byFeature: aggregated.map((row) => ({
      feature: row.feature,
      requests: row._sum.requestsCount ?? 0,
      tokens: row._sum.tokensUsed ?? 0,
      users: row._count.userId,
    })),
    topUsers: topUsers.map((row) => ({
      userId: row.userId,
      email: userMap[row.userId]?.email ?? row.userId,
      name: userMap[row.userId]?.name ?? null,
      requests: row._sum.requestsCount ?? 0,
    })),
  }
}

export async function getUsageOverview() {
  await checkAdmin()
  return getUsageOverviewInternal()
}