// /jobs/classReminderJob.js
'use strict';

const cron = require('node-cron');
const Session = require('../components/sessions/sessionModel');
const User = require('../components/users/userModel');
const { sendClassReminderSms } = require('../utils/senders/smsMessages');
const { buildClassScheduleContext } = require('../utils/classSchedule');
const logger = require('../utils/logger');

const parseStartDateTime = (session) => {
  const day = new Date(session.day);
  if (Number.isNaN(day.getTime())) return null;

  const [hoursRaw, minutesRaw = '0'] = String(session.startTime || '00:00').split(':');
  const hours = Number(hoursRaw);
  const minutes = Number(minutesRaw);
  if (Number.isNaN(hours) || Number.isNaN(minutes)) return null;

  const start = new Date(day);
  start.setHours(hours, minutes, 0, 0);
  return start;
};

const runClassReminderJob = async () => {
  try {
    const now = Date.now();
    const windowStart = new Date(now + 29 * 60 * 1000);
    const windowEnd = new Date(now + 31 * 60 * 1000);

    // Load scheduled sessions for today ± 1 day, then filter by exact start window
    const dayFrom = new Date(now - 24 * 60 * 60 * 1000);
    const dayTo = new Date(now + 24 * 60 * 60 * 1000);

    const sessions = await Session.find({
      status: 'scheduled',
      reminderSentAt: null,
      day: { $gte: dayFrom, $lte: dayTo },
    })
      .populate({ path: 'class', select: 'name students startDate' })
      .populate({ path: 'course', select: 'title' })
      .lean();

    for (const session of sessions) {
      const startAt = parseStartDateTime(session);
      if (!startAt || startAt < windowStart || startAt > windowEnd) continue;

      const classDoc = session.class;
      const studentIds = classDoc?.students || [];
      if (studentIds.length === 0) {
        await Session.updateOne({ _id: session._id }, { reminderSentAt: new Date() });
        continue;
      }

      const classLabel = classDoc?.name || session.course?.title || 'کلاس';
      const timeLabel = session.startTime;
      const placeLabel = session.place || '-';
      const classSessions = classDoc?._id
        ? await Session.find({ class: classDoc._id }).select('day startTime endTime').sort({ day: 1 }).lean()
        : [];
      const schedule = buildClassScheduleContext(classDoc, classSessions, session);

      const users = await User.find({ _id: { $in: studentIds } }).select('phoneNumber').lean();
      await Promise.all(
        users.map(async (user) => {
          if (!user.phoneNumber) return;
          try {
            await sendClassReminderSms(
              user.phoneNumber,
              classLabel,
              timeLabel,
              placeLabel,
              user._id,
              {
                courseName: session.course?.title || classLabel,
                ...schedule
              }
            );
          } catch (err) {
            logger.error(`[ClassReminderJob] SMS failed for ${user.phoneNumber}: ${err.message}`);
          }
        })
      );

      await Session.updateOne({ _id: session._id }, { reminderSentAt: new Date() });
      logger.info(`[ClassReminderJob] Reminders sent for session ${session._id}`);
    }
  } catch (error) {
    logger.error(`[ClassReminderJob ERROR]: ${error.message}`);
  }
};

const startClassReminderJob = () => {
  // Every minute — catches sessions ~30 minutes before start
  cron.schedule('* * * * *', async () => {
    await runClassReminderJob();
  });
  logger.info('[ClassReminderJob] Scheduled to run every minute.');
};

module.exports = {
  startClassReminderJob,
  runClassReminderJob,
};