import { NextRequest, NextResponse } from 'next/server'
import { prisma } from '@/lib/prisma'
import { createHmac } from 'crypto'

// Polar product IDs → tier flags
const PRODUCT_TIERS: Record<string, { isPremium: boolean; isPro: boolean }> = {
  'a291a3d9-fa82-4e88-ba89-c6005401398f': { isPremium: true, isPro: false },  // Premium
  '7f983017-e1f3-440e-be2a-5a5d19c9c7b0': { isPremium: true, isPro: true },   // Pro
}

function verifySignature(body: string, headers: Headers): boolean {
  const secret = process.env.POLAR_WEBHOOK_SECRET
  if (!secret) return false

  // Polar uses Svix: signature is over "id.timestamp.body"
  const webhookId = headers.get('webhook-id')
  const timestamp = headers.get('webhook-timestamp')
  const signature = headers.get('webhook-signature')
  if (!webhookId || !timestamp || !signature) return false

  const signedContent = `${webhookId}.${timestamp}.${body}`
  const secretBytes = Buffer.from(secret.replace('whsec_', ''), 'base64')
  const computed = createHmac('sha256', secretBytes).update(signedContent).digest('base64')

  // Signature header may contain multiple: "v1,<sig1> v1,<sig2>"
  return signature.split(' ').some(s => s === `v1,${computed}`)
}

export async function POST(req: NextRequest) {
  const body = await req.text()

  if (process.env.POLAR_WEBHOOK_SECRET && !verifySignature(body, req.headers)) {
    return NextResponse.json({ error: 'Invalid signature' }, { status: 400 })
  }

  let event: { type: string; data: any }
  try {
    event = JSON.parse(body)
  } catch {
    return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 })
  }

  const { type, data } = event

  try {
    switch (type) {
      case 'subscription.created':
      case 'subscription.updated': {
        const userId = data.metadata?.userId || data.customer?.metadata?.userId
        if (!userId) break

        const productId = data.product_id || data.product?.id
        const tier = productId ? PRODUCT_TIERS[productId] : null
        const isActive = ['active', 'trialing'].includes(data.status)

        if (isActive && tier) {
          await prisma.user.update({
            where: { id: userId },
            data: tier,
          })
        } else if (!isActive) {
          await prisma.user.update({
            where: { id: userId },
            data: { isPremium: false, isPro: false },
          })
        }
        break
      }

      case 'subscription.revoked':
      case 'subscription.canceled': {
        const userId = data.metadata?.userId || data.customer?.metadata?.userId
        if (!userId) break
        await prisma.user.update({
          where: { id: userId },
          data: { isPremium: false, isPro: false },
        })
        break
      }
    }
  } catch (e) {
    console.error('Polar webhook handler error:', e)
    return NextResponse.json({ error: 'Handler error' }, { status: 500 })
  }

  return NextResponse.json({ received: true })
}