Next.js 15 App Router in Production: Server Actions, Streaming & Parallel Routing

'use server';

import { z } from 'zod';
import { revalidatePath } from 'next/cache';

const EmailSchema = z.string().email('Please enter a valid business email.');

export async function subscribeNewsletterAction(prevState: any, formData: FormData) {
  const emailInput = formData.get('email');
  const validation = EmailSchema.safeParse(emailInput);

  if (!validation.success) {
    return { success: false, error: validation.error.errors[0].message };
  }

  try {
    await db.subscribers.insert({ email: validation.data, createdAt: new Date() });
    revalidatePath('/blog');
    return { success: true, message: 'Subscribed to engineering blueprints successfully!' };
  } catch (err) {
    return { success: false, error: 'Database write failed. Please retry.' };
  }
}