// /components/professors/professorService.js

const Professor = require('./professorModel');
const AppError = require('../../utils/AppError');
const eventEmitter = require('../../events/eventEmitter');
const EVENT_NAMES = require('../../constants/eventNames');
const { parsePaginationAndSort, buildFilterQuery, calculateMeta } = require('../../utils/pagination');

const createProfessor = async (data) => {
  const existing = await Professor.findOne({
    $or: [
      { nationalIdCode: data.nationalIdCode },
      { phoneNumber: data.phoneNumber },
      ...(data.email ? [{ email: data.email }] : [])
    ]
  });
  if (existing) {
    throw new AppError('PROFESSOR_ALREADY_EXISTS');
  }

  const professor = await Professor.create(data);
  eventEmitter.emit(EVENT_NAMES.PROFESSOR_CREATED, { professorId: professor._id, name: `${professor.name} ${professor.surname}` });
  return professor;
};

const getProfessorById = async (id) => {
  const professor = await Professor.findById(id).populate('courses', 'title type price');
  if (!professor) {
    throw new AppError('PROFESSOR_NOT_FOUND');
  }
  return professor;
};

const getAllProfessors = async (queryParams) => {
  const { page, limit, skip, sort } = parsePaginationAndSort(queryParams);
  const filter = buildFilterQuery(queryParams, ['name', 'surname', 'nationalIdCode', 'phoneNumber', 'email', 'expertise']);

  const [professors, totalCount] = await Promise.all([
    Professor.find(filter).populate('courses', 'title').sort(sort).skip(skip).limit(limit),
    Professor.countDocuments(filter)
  ]);

  const meta = calculateMeta(totalCount, page, limit);
  return { data: professors, meta };
};

const updateProfessor = async (id, updateData) => {
  const professor = await Professor.findById(id);
  if (!professor) {
    throw new AppError('PROFESSOR_NOT_FOUND');
  }

  Object.assign(professor, updateData);
  await professor.save();
  return professor;
};

const deleteProfessor = async (id) => {
  const professor = await Professor.findById(id);
  if (!professor) {
    throw new AppError('PROFESSOR_NOT_FOUND');
  }

  await Professor.findByIdAndDelete(id);
  return null;
};

const searchProfessors = async (queryParams) => {
  return getAllProfessors(queryParams);
};

module.exports = {
  createProfessor,
  getProfessorById,
  getAllProfessors,
  updateProfessor,
  deleteProfessor,
  searchProfessors
};