// Daily "don't forget to read" reminders, sent via ntfy.sh (https://ntfy.sh) —
// a free pub/sub push service: POST a message to a topic URL, anyone
// subscribed to that topic (via the ntfy app or a browser) gets notified.
// No API keys or push-subscription plumbing needed.
import { getUsersWithRemindersEnabled, setLastReminderDate, getReadingProgress } from './db.js';

function todayDateString(d = new Date()) {
  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
}

function currentHHMM(d = new Date()) {
  return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
}

async function sendNtfyReminder(user) {
  const base = (user.ntfyUrl || 'https://ntfy.sh').replace(/\/+$/, '');
  const url = `${base}/${encodeURIComponent(user.ntfyTopic)}`;
  const res = await fetch(url, {
    method: 'POST',
    headers: { Title: 'Reading Plan Reminder', Tags: 'open_book' },
    body: "Don't forget today's reading!",
  });
  if (!res.ok) throw new Error(`ntfy responded ${res.status}`);
}

async function checkReminders() {
  const now = new Date();
  const hhmm = currentHHMM(now);
  const today = todayDateString(now);
  const due = getUsersWithRemindersEnabled().filter(
    (u) => u.reminderTime === hhmm && u.lastReminderDate !== today,
  );

  for (const user of due) {
    try {
      const progress = getReadingProgress(user.id);
      const hasActivePlan = Array.isArray(progress?.progress) && progress.progress.some((p) => !p.completedAt);
      if (!hasActivePlan) continue; // nothing to nudge them about
      await sendNtfyReminder(user);
      setLastReminderDate(user.id, today);
    } catch (err) {
      console.error(`Reading reminder failed for user ${user.id}:`, err.message);
    }
  }
}

/** Checks once a minute whether any user's reminder time has arrived. */
export function startReminderScheduler() {
  setInterval(() => {
    checkReminders().catch((err) => console.error('Reminder scheduler error:', err));
  }, 60 * 1000);
}