import * as errors from '@@/custom-errors';

export function validateUsername(username: string | undefined): string {
  if (!username || !username.trim()) {
    throw errors.BAD_REQUEST('Username is required');
  }

  const trimmed = username.trim();

  if (trimmed.includes('@')) {
    throw errors.BAD_REQUEST('Username cannot be an email address');
  }

  if (trimmed.length < 2 || trimmed.length > 32) {
    throw errors.BAD_REQUEST('Username must be between 2 and 32 characters');
  }

  if (!/^[a-zA-Z0-9._-]+$/.test(trimmed)) {
    throw errors.BAD_REQUEST('Username can only contain letters, numbers, dots, hyphens, and underscores');
  }

  return trimmed;
}