export async function register() {
  console.log('[instrumentation] register() called, NEXT_RUNTIME =', process.env.NEXT_RUNTIME)
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const fs = await import('fs')
    const path = await import('path')
    const journal = path.join(process.cwd(), 'lib/db/migrations/meta/_journal.json')

    if (!fs.existsSync(journal)) {
      console.warn('[migrations] No journal found at', journal, '— skipping')
      return
    }

    console.log('[migrations] Applying migrations...')
    try {
      const postgres = (await import('postgres')).default
      const { drizzle } = await import('drizzle-orm/postgres-js')
      const { migrate } = await import('drizzle-orm/postgres-js/migrator')

      // Dedicated single connection for migrations — never share with the app pool
      const client = postgres(process.env.DATABASE_URL!, { max: 1, connect_timeout: 10 })
      const db = drizzle(client)
      await migrate(db, { migrationsFolder: './lib/db/migrations' })
      console.log('[migrations] Done')

      // Seed admin user from ADMIN_EMAIL if not already present
      const adminEmail = process.env.ADMIN_EMAIL
      if (adminEmail) {
        const { user } = await import('./lib/db/schema')
        const { eq } = await import('drizzle-orm')
        const existing = await db.select({ id: user.id }).from(user).where(eq(user.email, adminEmail)).limit(1)
        if (existing.length === 0) {
          const { default: crypto } = await import('crypto')
          await db.insert(user).values({
            id:            crypto.randomUUID(),
            email:         adminEmail,
            name:          adminEmail.split('@')[0],
            emailVerified: true,
            createdAt:     new Date(),
            updatedAt:     new Date(),
          })
          console.log('[seed] Admin user created:', adminEmail)
        }
      }

      await client.end()
    } catch (err) {
      console.error('[migrations] Failed:', err)
    }
  }
}