৮। Helper ফাইল তৈরি করা (userHelper.js)

// helpers/userHelper.js

const  User  = require("../models/User");
const ApiError = require("../utils/ApiError");
const HTTP_STATUS_CODES = require("../constants/httpStatus.js");

/**
 * Check if a user with the given email exists
 * @param {string} email - User's email
 * @returns {Promise<boolean>}
 */
const isUserExistsByEmail = async (email) => {
  const user = await User.findOne({ where: { email } });
  return !!user;
};

/**
 * Find a user by ID
 * @param {number} userId - User ID
 * @returns {Promise<User>}
 */
const findUserById = async (userId) => {
  const user = await User.findByPk(userId);
  if (!user) {
    throw new ApiError(HTTP_STATUS_CODES.NOT_FOUND, "User not found");
  }
  return user;
};

/**
 * Validate if the user can be updated or deleted
 * @param {number} userId - User ID
 * @returns {Promise<void>}
 */
const validateUserUpdateOrDelete = async (userId) => {
  const userExists = await User.findByPk(userId);
  if (!userExists) {
    throw new ApiError(HTTP_STATUS_CODES.NOT_FOUND, "User not found for update/delete");
  }
};

module.exports = {
  isUserExistsByEmail,
  findUserById,
  validateUserUpdateOrDelete,
};