/**
 * Sends the daily review reminder to every stored push subscription.
 *
 * Meant for cron or a systemd timer, e.g.:
 *   0 18 * * *  cd /path/to/freezmo && node scripts/send-reminders.mjs
 *
 * Silently does nothing when VAPID keys are not configured (the whole
 * reminder feature stays hidden in the UI in that case).
 */
import { readFile, rename, writeFile } from "node:fs/promises";
import path from "node:path";
import webpush from "web-push";

const dir = process.env.PUSH_DIR?.trim() || path.join(process.cwd(), ".freezmo", "push");
const publicKey = process.env.VAPID_PUBLIC_KEY?.trim();
const privateKey = process.env.VAPID_PRIVATE_KEY?.trim();
const subject = process.env.VAPID_SUBJECT?.trim() || "mailto:freezmo@localhost";
const title = process.env.PUSH_REMINDER_TITLE?.trim() || "Time to review";
const body =
  process.env.PUSH_REMINDER_BODY?.trim() ||
  "Your decks are waiting — a few due cards keep the streak alive.";

if (!publicKey || !privateKey) {
  console.log("[freezmo] VAPID keys are not configured — nothing to send.");
  process.exit(0);
}

const file = path.join(dir, "subscriptions.json");
let subscriptions = [];
try {
  subscriptions = JSON.parse(await readFile(file, "utf8"));
} catch {
  subscriptions = [];
}

if (!Array.isArray(subscriptions) || subscriptions.length === 0) {
  console.log("[freezmo] no push subscriptions stored.");
  process.exit(0);
}

webpush.setVapidDetails(subject, publicKey, privateKey);

let sent = 0;
let removed = 0;
const remaining = [];
for (const entry of subscriptions) {
  try {
    await webpush.sendNotification(
      { endpoint: entry.endpoint, keys: entry.keys },
      JSON.stringify({ title, body, url: "/" }),
    );
    sent += 1;
    remaining.push(entry);
  } catch (error) {
    const status = error?.statusCode;
    if (status === 404 || status === 410) removed += 1;
    else remaining.push(entry);
  }
}

if (removed > 0) {
  const temporary = `${file}.${Date.now()}.tmp`;
  await writeFile(temporary, JSON.stringify(remaining, null, 2), "utf8");
  await rename(temporary, file);
}

console.log(`[freezmo] reminders sent: ${sent}, dead subscriptions removed: ${removed}`);