// /components/classes/classService.js
'use strict';

const Class = require('./classModel');
const User = require('../users/userModel');
const AppError = require('../../utils/AppError');
const { calculateMeta } = require('../../utils/pagination');
const { sendClassRegisteredSms } = require('../../utils/senders/smsMessages');
const logger = require('../../utils/logger');

const getAll = async (query) => {
  const page = parseInt(query.page) || 1;
  const limit = Math.min(parseInt(query.limit) || 20, 200);
  const skip = (page - 1) * limit;

  const filter = {};
  if (query.courseId) filter.course = query.courseId;
  if (query.isActive !== undefined) filter.isActive = query.isActive === 'true';

  const [items, total] = await Promise.all([
    Class.find(filter)
      .populate({ path: 'course', select: 'title type price' })
      .populate({ path: 'professor', select: 'name surname' })
      .skip(skip).limit(limit).sort({ createdAt: -1 }).lean(),
    Class.countDocuments(filter)
  ]);

  return { data: items, meta: calculateMeta(total, page, limit) };
};

const getOne = async (id) => {
  const cls = await Class.findById(id)
    .populate({ path: 'course', select: 'title type price' })
    .populate({ path: 'professor', select: 'name surname phoneNumber' })
    .populate({ path: 'students', select: 'name surname phoneNumber' })
    .lean();
  if (!cls) throw new AppError('CLASS_NOT_FOUND');
  return cls;
};

const create = async (body) => {
  const cls = await Class.create(body);
  return getOne(cls._id);
};

const update = async (id, body) => {
  const cls = await Class.findByIdAndUpdate(id, body, { new: true, runValidators: true })
    .populate({ path: 'course', select: 'title' })
    .lean();
  if (!cls) throw new AppError('CLASS_NOT_FOUND');
  return cls;
};

const remove = async (id) => {
  const cls = await Class.findByIdAndDelete(id);
  if (!cls) throw new AppError('CLASS_NOT_FOUND');
};

const registerUsers = async (classId, userIds) => {
  const cls = await Class.findById(classId).populate({ path: 'course', select: 'title' });
  if (!cls) throw new AppError('CLASS_NOT_FOUND');

  const toAdd = (userIds || []).filter(
    (id) => !cls.students.map((s) => s.toString()).includes(id.toString())
  );
  if (toAdd.length === 0) {
    return getOne(classId);
  }

  cls.students.push(...toAdd);
  await cls.save();

  const classLabel = cls.name || cls.course?.title || 'کلاس';
  const users = await User.find({ _id: { $in: toAdd } }).select('phoneNumber').lean();
  await Promise.all(
    users.map(async (user) => {
      if (!user.phoneNumber) return;
      try {
        await sendClassRegisteredSms(user.phoneNumber, classLabel, user._id);
      } catch (err) {
        logger.error(`[registerUsers] SMS failed for ${user.phoneNumber}: ${err.message}`);
      }
    })
  );

  return getOne(classId);
};

const getMyClasses = async (userId, query = {}) => {
  const page = parseInt(query.page) || 1;
  const limit = Math.min(parseInt(query.limit) || 20, 200);
  const skip = (page - 1) * limit;

  const filter = { students: userId };
  if (query.isActive !== undefined) filter.isActive = query.isActive === 'true';

  const [items, total] = await Promise.all([
    Class.find(filter)
      .populate({ path: 'course', select: 'title type price description' })
      .populate({ path: 'professor', select: 'name surname' })
      .skip(skip).limit(limit).sort({ startDate: -1, createdAt: -1 }).lean(),
    Class.countDocuments(filter)
  ]);

  return { data: items, meta: calculateMeta(total, page, limit) };
};

module.exports = { getAll, getOne, create, update, remove, registerUsers, getMyClasses };