svrjs-nextjs-website/app/api/newsletter/send/route.ts

import { NextRequest, NextResponse } from "next/server";
import nodemailer from "nodemailer";
import clientPromise from "@/lib/db";

const transporter = nodemailer.createTransport({
  host: "smtp.ethereal.email", //replace this also comment this if u not using etheral
  // service: "gmail", // uncomment if u using gmail
  port: 587,
  auth: {
    user: process.env.EMAIL,
    pass: process.env.EMAIL_PASS
  }
});

const sendEmail = async (to: string[], subject: string, html: string) => {
  try {
    await transporter.sendMail({
      from: process.env.EMAIL_USER,
      to: to.join(", "),
      subject: subject,
      html: html
    });
  } catch (error) {
    console.error("Error sending email:", error);
    throw new Error("Failed to send email");
  }
};

export async function POST(req: NextRequest) {
  try {
    const { subject, html } = await req.json();

    const client = await clientPromise;
    const db = client.db("newsletter");
    const collection = db.collection("subscribers");

    const subscribers = await collection
      .find({}, { projection: { email: 1 } })
      .toArray();

    if (subscribers.length === 0) {
      console.error("No subscribers found in the database.");
      return NextResponse.json(
        { message: "No subscribers found." },
        { status: 404 }
      );
    }

    const emails = subscribers.map((subscriber) => subscriber.email);

    if (emails.length === 0) {
      console.error("No email addresses found.");
      return NextResponse.json(
        { message: "No email addresses found." },
        { status: 404 }
      );
    }

    await sendEmail(emails, subject, html);
    return NextResponse.json({ message: "Emails sent successfully" });
  } catch (error) {
    console.error("Error handling POST request:", error);
    return NextResponse.error();
  }
}