Crons (Scheduled Functions)

import { Inngest } from "inngest";

const inngest = new Inngest({ id: "signup-flow" });

// This weekly digest function will run at 12:00pm on Friday in the Paris timezone
export const prepareWeeklyDigest = inngest.createFunction(
  { id: "prepare-weekly-digest" },
  { cron: "TZ=Europe/Paris 0 12 * * 5" },
  async ({ step }) => {
    // Load all the users from your database:
    const users = await step.run(
      "load-users",
      async () => await db.load("SELECT * FROM users")
    );

    // 💡 Since we want to send a weekly digest to each one of these users
    // it may take a long time to iterate through each user and send an email.

    // Instead, we'll use this scheduled function to send an event to Inngest
    // for each user then handle the actual sending of the email in a separate
    // function triggered by that event.

    // ✨ This is known as a "fan-out" pattern ✨

    // 1️⃣ First, we'll create an event object for every user return in the query:
    const events = users.map((user) => {
      return {
        name: "app/send.weekly.digest",
        data: {
          user_id: user.id,
          email: user.email,
        },
      };
    });

    // 2️⃣ Now, we'll send all events in a single batch:
    await step.sendEvent("send-digest-events", events);

    // This function can now quickly finish and the rest of the logic will
    // be handled in the function below ⬇️
  }
);

// This is a regular Inngest function that will send the actual email for
// every event that is received (see the above function's inngest.send())

// Since we are "fanning out" with events, these functions can all run in parallel
export const sendWeeklyDigest = inngest.createFunction(
  { id: "send-weekly-digest-email" },
  { event: "app/send.weekly.digest" },
  async ({ event }) => {
    // 3️⃣ We can now grab the email and user id from the event payload
    const { email, user_id } = event.data;

    // 4️⃣ Finally, we send the email itself:
    await email.send("weekly_digest", email, user_id);

    // 🎇 That's it! - We've used two functions to reliably perform a scheduled
    // task for a large list of users!
  }
);