import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import { stripe } from '@/lib/stripe'
import { isBillingEnabled } from '@/lib/billing/stripe-prices'
import {
  isCreditPackId,
  resolvePackPriceId,
  getCreditPack,
} from '@/lib/billing/credit-packs'
import { prisma } from '@/lib/prisma'
import { z } from 'zod'

const bodySchema = z.object({
  packId: z.enum(['S', 'M', 'L']),
})

export async function POST(req: NextRequest) {
  const session = await auth()
  if (!session?.user?.id || !session.user.email) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }

  if (!(await isBillingEnabled())) {
    return NextResponse.json({ error: 'Billing is not enabled' }, { status: 403 })
  }

  const secret = process.env.STRIPE_SECRET_KEY
  if (!secret || secret === 'sk_test_placeholder') {
    return NextResponse.json(
      { error: 'Stripe is not configured (STRIPE_SECRET_KEY missing)' },
      { status: 503 },
    )
  }

  const parsed = bodySchema.safeParse(await req.json())
  if (!parsed.success || !isCreditPackId(parsed.data.packId)) {
    return NextResponse.json({ error: 'Invalid pack' }, { status: 400 })
  }

  const packId = parsed.data.packId
  const pack = getCreditPack(packId)
  const userId = session.user.id
  const userEmail = session.user.email

  try {
    let priceId: string
    try {
      priceId = await resolvePackPriceId(packId)
    } catch (e) {
      console.error('[billing/create-pack-checkout] price resolve failed:', e)
      return NextResponse.json(
        { error: 'Credit pack price IDs not configured. Set them in Admin > Billing.' },
        { status: 503 },
      )
    }

    if (priceId.startsWith('price_mock_')) {
      return NextResponse.json(
        { error: 'Credit pack price IDs not configured. Set them in Admin > Billing.' },
        { status: 503 },
      )
    }

    const subscription = await prisma.subscription.findUnique({ where: { userId } })
    let customerId = subscription?.stripeCustomerId ?? undefined

    if (customerId && customerId.startsWith('cus_mock')) {
      customerId = undefined
    }

    if (!customerId) {
      const customer = await stripe.customers.create({
        email: userEmail,
        metadata: { userId },
      })
      customerId = customer.id

      await prisma.subscription.upsert({
        where: { userId },
        update: { stripeCustomerId: customerId },
        create: {
          userId,
          stripeCustomerId: customerId,
          tier: 'BASIC',
          status: 'ACTIVE',
          currentPeriodStart: new Date(),
          currentPeriodEnd: new Date(Date.now() + 30 * 24 * 3600 * 1000),
        },
      })
    }

    const host = req.headers.get('x-forwarded-host') ?? req.headers.get('host') ?? 'localhost:3000'
    const proto = req.headers.get('x-forwarded-proto') ?? 'http'
    const origin = `${proto}://${host}`

    const checkoutSession = await stripe.checkout.sessions.create({
      customer: customerId,
      mode: 'payment',
      line_items: [{ price: priceId, quantity: 1 }],
      success_url: `${origin}/settings/billing?session_id={CHECKOUT_SESSION_ID}&pack=1`,
      cancel_url: `${origin}/settings/billing?canceled=1`,
      metadata: {
        userId,
        type: 'credit_pack',
        packId,
        credits: String(pack.credits),
      },
      payment_intent_data: {
        metadata: {
          userId,
          type: 'credit_pack',
          packId,
          credits: String(pack.credits),
        },
      },
      customer_update: { address: 'auto' },
      allow_promotion_codes: true,
    })

    if (!checkoutSession.url) {
      return NextResponse.json({ error: 'Checkout session has no URL' }, { status: 500 })
    }

    return NextResponse.json({
      url: checkoutSession.url,
      sessionId: checkoutSession.id,
      packId,
      credits: pack.credits,
    })
  } catch (error) {
    console.error('[billing/create-pack-checkout]', error)
    const msg = error instanceof Error ? error.message : 'Failed to create pack checkout'
    return NextResponse.json({ error: msg }, { status: 500 })
  }
}