Buy a label with EasyPost. Print it where the box is.

import RocketPrint from "@rocketprint/node";

const rocketprint = new RocketPrint({ apiKey: process.env.ROCKETPRINT_KEY });

export async function shipOrder(order, bench) {
  // 1. Buy postage, asking for ZPL because the bench has a thermal printer.
  const shipment = await easypost.Shipment.create({ /* to, from, parcel */ });
  const bought = await shipment.buy(shipment.lowestRate(), { label_format: "ZPL" });

  // 2. Fetch the label server-side. RocketPrint never fetches URLs for you.
  const zpl = await fetch(bought.postage_label.label_zpl_url).then((r) => r.arrayBuffer());

  // 3. Print it where the box actually is.
  const job = await rocketprint.printJobs.create({
    printerId: bench.printerId,
    title: `Label ${bought.tracking_code}`,
    contentType: "raw_base64",
    content: Buffer.from(zpl).toString("base64"),
    source: "easypost",
  }, {
    idempotencyKey: `easypost-${bought.id}-${bench.id}`,
  });

  return { trackingCode: bought.tracking_code, printJobId: job.id };
}