Email System

import Resend from "resend";
import Mailgen from "mailgen";
import config from "./index.js";

let resendClient = null;
let mailGenerator = null;

if (config.mail.apiKey) {
  resendClient = new Resend(config.mail.apiKey);
}

mailGenerator = new Mailgen({
  theme: "default",
  product: {
    name: config.mail.appName,
    link: process.env.APP_URL || "http://localhost:3000",
  },
});

sendVerificationEmail(email, otp);

sendWelcomeEmail(email, name);

sendPasswordResetEmail(email, otp);

const emailContent = mailGenerator.generate({
  body: {
    action: {
      instructions: "Use the following OTP to verify your email:",
      button: {
        color: "#22BC66",
        text: otp,
      },
    },
  },
});

const emailContent = mailGenerator.generate({
  body: {
    intro: `Welcome ${name}! We're glad to have you on board.`,
    outro: "Feel free to reach out if you have any questions.",
  },
});

await resendClient.emails.send({
  from: config.mail.from,
  to: email,
  subject: "Verify Your Email",
  html: emailContent.html,
  text: emailContent.plaintext,
});

export async function sendVerificationEmail(email, otp) {
  if (!resendClient) return;  // Graceful no-op

  try {
    // Generate template + send
    const emailContent = mailGenerator.generate({ ... });
    await resendClient.emails.send({ ... });
    loggerService.info(`Verification email sent to ${email}`);
  } catch (error) {
    loggerService.error(`Failed to send verification email: ${error.message}`);
    throw error;  // Don't swallow - caller should handle
  }
}

// backend/src/routes/webhook.js
import { sendWelcomeEmail } from "../services/mail.service.js";

router.post("/webhooks/clerk", async (req, res) => {
  const event = verifyWebhook(req);

  if (event.type === "user.created") {
    const { email_addresses, first_name } = event.data;
    const primaryEmail = email_addresses[0]?.email_address;

    if (primaryEmail) {
      await sendWelcomeEmail(primaryEmail, first_name || "there");
    }
  }

  res.json({ received: true });
});

// tests/services/mail.service.test.js
it("should send verification email successfully", async () => {
  mockResend.emails.send.mockResolvedValue({ id: "test-id" });
  await sendVerificationEmail("user@test.com", "123456");
  expect(mockResend.emails.send).toHaveBeenCalled();
});

it("should throw error when sending fails", async () => {
  mockResend.emails.send.mockRejectedValue(new Error("API error"));
  await expect(
    sendVerificationEmail("user@test.com", "123456"),
  ).rejects.toThrow("API error");
});

// tests/services/mail.no-config.test.js
it("should return early when resendClient is null", async () => {
  const result = await sendVerificationEmail("user@test.com", "123456");
  expect(result).toBeUndefined(); // No-op
});