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Overview

We can use a scheduled job to run every Monday morning to send out a product announcement email if any new release is detected. For the sake of simplicity, we’re going to use the public GitHub API to check the latest published release of an open source project to demonstrate how this might work.

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Checking a project’s latest release

We can use use the following API endpoint to get the latest release for a project, given the GitHub owner and repo names: 
https://api.github.com/repos/{owner}/{repo}/releases/latest
For this example, we’re going to use Supabase’s main repository: https://github.com/supabase/supabase We can see the latest release data here: https://api.github.com/repos/supabase/supabase/releases/latest We’re going to use the name and body markdown field for our email notification, and the release id to reference the last notification that was sent. Here’s how we could retrieve that data in TypeScript: 
const fetchLatestRelease = async (owner: string, repo: string) => {
  const url = `https://api.github.com/repos/${owner}/${repo}/releases/latest`;

  return fetch(url).then((r) => r.json());
};

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Triggering emails for new releases

Now what we want to do is:
  1. Fetch the latest release of the repository using the fetchLatestRelease function above.
  2. Use the schedule’s state to store the ID of last sent release, which we check against the current latest release.
  3. If the current latest release is different from the last sent release, we trigger an email to be sent out to the recipients of our choosing.
Here we handle that in a NextJS API endpoint, using Resend to as our email API: 
import { Resend } from "resend";

export default async function handler(req, res) {
  const { owner, repo, recipients, last_sent_release } = req.body;
  const release = await fetchLatestRelease(owner, repo);

  if (!release || !release.name || !release.body) {
    return res.status(404).json({ error: "Not found." });
  } else if (release.id === last_sent_release) {
    return res.status(200).json({ message: "This release was already sent." });
  }

  // Get your free Resend API key at https://resend.com/api-keys
  const resend = new Resend(process.env.RESEND_API_KEY);
  const email = await resend.sendEmail({
    from: `${repo}@resend.dev`,
    to: recipients,
    subject: release.name,
    text: release.body,
  });

  // Use the special keyword `$set` to cache the the `last_sent_release`
  // on the schedule's state for reference in future jobs
  return res.json({ email, $set: { last_sent_release: release.id } });
}
Note that in the reponse we use the special $set key to update the state of the job schedule, so that we can reference the last_sent_release ID in future jobs.
The code above will trigger an email of plaintext/markdown, which isn’t ideal. Let’s use react-email and react-markdown to send a prettier email!

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Formatting the email HTML

Right now our email is just getting sent in plaintext markdown:
If we want to send some nicer HTML, we can use react-markdown to handle parsing the markdown to React, and react-email to handle rendering a React component as the email. First, let’s define a React component to render our markdown email:
/components/emails/MarkdownEmail.tsx
import * as React from "react";
import {
  Body,
  Container,
  Head,
  Heading,
  Hr,
  Html,
  Img,
  Link,
  Tailwind,
  Text,
} from "@react-email/components";
import ReactMarkdown from "react-markdown";

export const MarkdownEmail = ({ markdown }: { markdown: string }) => {
  return (
    <Html>
      <Head />
      <Tailwind>
        <Body className="mx-auto my-auto bg-white font-sans">
          <Container className="max-w-[40em]">
            <ReactMarkdown
              components={{
                // Render tags as react-email components
                h1: ({ node, ...props }) => <Heading as="h1" {...props} />,
                h2: ({ node, ...props }) => <Heading as="h2" {...props} />,
                h3: ({ node, ...props }) => <Heading as="h3" {...props} />,
                h4: ({ node, ...props }) => <Heading as="h4" {...props} />,
                a: ({ node, ...props }) => <Link {...props} />,
                p: ({ node, ...props }) => <Text {...props} />,
                li: ({ node, children, ...props }) => (
                  <li {...props}>
                    <Text className="my-2">{children}</Text>
                  </li>
                ),
                hr: ({ node, ...props }) => <Hr {...props} />,
                img: ({ className, ...props }) => {
                  return (
                    <Img className={`${className} max-w-full`} {...props} />
                  );
                },
              }}
            >
              {markdown}
            </ReactMarkdown>
          </Container>
        </Body>
      </Tailwind>
    </Html>
  );
};

export default MarkdownEmail;
Now, all we have to do is update our original route to use this component: 
// pages/api/announcements.ts

import { render } from "@react-email/render";
import MarkdownEmail from "@/components/emails/MarkdownEmail";

export default async function handler(req, res) {
  // ...

  const email = await resend.sendEmail({
    from: `${repo}@resend.dev`,
    to: recipients,
    subject: release.name,
    text: release.body,
    html: render(MarkdownEmail({ markdown: release.body })),
  });

  // ...
}
Now, when we trigger the email, it should look more like this:
Much better!

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Creating the scheduled job

Using our new API endpoint, we can schedule a job to run it every Monday at 10am using a cron expression, using the schedule $state to reference the last sent release ID: 
# This assumes your API key is set in the current env
# BOOPER_API_KEY=sk_...

curl --location --request POST 'https://scheduler.booper.dev/api/jobs' \
--header "Content-Type: application/json" \
--header "Authorization: Bearer $BOOPER_API_KEY" \
--data-raw '{
    "method": "post",
    "url": "https://yourdomain.com/api/announcements",
    "body": {
      "owner": "supabase",
      "repo": "supabase",
      "recipients": "me@booper.dev",
      "last_sent_release": "$state.last_sent_release"
    },
    "cron": "0 10 * * MON"
}'