Enrich a contact list

import { setTimeout as sleep } from "node:timers/promises";

const BATCH_SIZE = 50;

function toItem(contact) {
  const base = { id: contact.id };
  if (contact.country) base.country = contact.country;
  if (contact.firstName) return { ...base, type: "name", value: contact.firstName };
  if (contact.email) return { ...base, type: "email", value: contact.email };
  return { ...base, type: "username", value: contact.username };
}

async function enrich(contacts) {
  const items = contacts.filter((c) => c.firstName || c.email || c.username).map(toItem);

  for (let start = 0; start < items.length; start += BATCH_SIZE) {
    const batch = items.slice(start, start + BATCH_SIZE);
    const response = await fetch("https://api.finowl.co/v1/gender/batch", {
      method: "POST",
      headers: {
        Authorization: `Bearer ${process.env.FINOWL_API_KEY}`,
        "Content-Type": "application/json",
      },
      body: JSON.stringify({ items: batch }),
      signal: AbortSignal.timeout(40_000),
    });

    const body = await response.json();

    if (response.status === 429 && body.error?.code === "rate_limited") {
      await sleep(Number(response.headers.get("Retry-After") ?? 60) * 1000);
      start -= BATCH_SIZE; // Not charged, so resend the same batch.
      continue;
    }
    if (!Array.isArray(body.data)) {
      // quota_exceeded, invalid_input or a service error. Stop and investigate.
      throw new Error(body.error?.code ?? `http_${response.status}`);
    }

    for (const result of body.data) {
      if (result.error) {
        await markFailed(result.id, result.error.code);
      } else {
        await saveGender(result.id, result.data);
      }
    }

    await sleep(1000); // Leave room in the rate limit for live traffic.
  }
}