src/utils/email.js

const HttpError = require('./httpError');

const EMAIL_REGEX = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

function normalizeEmail(email) {
  return String(email || '').trim().toLowerCase();
}

function validateEmail(email) {
  const normalizedEmail = normalizeEmail(email);

  if (!EMAIL_REGEX.test(normalizedEmail)) {
    throw new HttpError(
      400,
      'A valid email address is required.',
      'INVALID_EMAIL',
    );
  }

  return normalizedEmail;
}

function maskEmail(email) {
  const normalizedEmail = normalizeEmail(email);
  const [localPart, domainPart] = normalizedEmail.split('@');

  if (!localPart || !domainPart) {
    return normalizedEmail;
  }

  if (localPart.length <= 2) {
    return `${localPart[0] || '*'}*@${domainPart}`;
  }

  return `${localPart[0]}${'*'.repeat(Math.max(localPart.length - 2, 1))}${localPart.slice(-1)}@${domainPart}`;
}

module.exports = {
  maskEmail,
  normalizeEmail,
  validateEmail,
};