​
Overview

Let’s set up a script that sends one of Paul Graham’s top essays to our inbox every Monday, Wednesday, and Friday.

Here’s how we’ll tackle it:

  1. Write the script to fetch a random essay from Paul Graham’s most popular essays
  2. Set up an email to be sent with the essay every Monday/Wednesday/Friday
  3. Configure the schedule so that it “remembers” which essays have already been sent through

​
Fetching essay data

We’ll use the cheerio library to parse the essay page HTML. Here’s what that function might look like:

const fetchEssayHtml = async (slug) => {
  const response = await fetch(`http://www.paulgraham.com/${slug}.html`);
  const html = await response.text();
  const $ = cheerio.load(html);
  const essay = $('td[width="435"]');

  return {
    title: $("title").text(),
    text: essay.text(),
    html: essay.html(),
  };
};

Here’s what the output of that might look like:

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Triggering an email with the essay

First, let’s define a helper function to pick a random essay:

const getRandomEssay = (excluding = []) => {
  // Add as many as you like
  const slugs = ["avg", "say", "nerds", "taste", "gh", "road", "wealth"];
  const options = slugs.filter((s) => !excluding.includes(s));
  const index = Math.floor(Math.random() * options.length);

  return slugs[index];
};

Now, all we have to do is trigger the email.

Here we handle that in a NextJS API endpoint:

export default async function handler(req, res) {
  // Get your free Resend API key at https://resend.com/api-keys
  const resendApiKey = req.body.resend_api_key || process.env.RESEND_API_KEY;
  const recipient = req.body.recipient || "me@example.com";
  const exclude = req.body.exclude || [];
  const essay = req.body.essay || getRandomEssay(exclude);
  const { title, text, markdown, html } = await fetchEssayHtml(essay);
  const payload = {
    from: `pg@resend.dev`,
    to: recipient,
    subject: title,
    text: markdown || text,
    // Wrap the email in a max-width for better readability
    html: `<div style="max-width: 480px">${html}</div>`,
  };
  const resend = new Resend(resendApiKey);
  const email = await resend.sendEmail(payload);

  return res.json({ email });
}

​
Keeping track of alert history

When you create a job on a schedule, the scheduler will pass in some metadata into the body of each request. Included in the metadata is the schedule’s state, which can be accessed at req.body.$state and set or updated in the response.

Let’s modify the API handler to take advantage of $state:

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

  const exclude = req.body.$state?.sent || [];
  const essay = req.body.essay || getRandomEssay(exclude);

  // ...

  const email = await resend.sendEmail({...});

  return res.json({ email, $set: { sent: [...exclude, essay] } });
}

We can clean this up a bit by taking advantage of dynamic values in our job schedule configuration. When we set the request body for our job, we can write it like this:

{
  // Pass in `req.body.$state?.sent` as `req.body.exclude`
  "exclude": "$state.sent"
}

If we do this, we can change the line above from this:

const exclude = req.body.$state?.sent || [];

To this:

const exclude = req.body.exclude || [];

Now, assuming you’ve deployed your API endpoint to https://yourdomain.com/api/pg, you can create your scheduled job by running the following script in your terminal with your BOOPER_API_KEY set, and the url modified to the appropriate domain:

# 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 $BOOPER_API_KEY" \
--data-raw '{
    "method": "post",
    "url": "https://yourdomain.com/api/pg",
    "body": {
      "recipient": YOUR_EMAIL_ADDRESS,
      "resend_api_key": YOUR_RESEND_API_KEY,
      "exclude": "$state.sent"
    },
    "cron": "0 10 * * MON,WED,FRI"
}'