import invariant from 'invariant';
import qs from 'qs';

export function buildQueryString(input: Record<string, string>): string {
  return qs.stringify(input);
}

export function getQueryParams(url: string): {
  errorCode: string | null;
  params: { [key: string]: string };
} {
  const parts = url.split('#');
  const hash = parts[1];
  const partsWithoutHash = parts[0].split('?');
  const queryString = partsWithoutHash[partsWithoutHash.length - 1];

  // Get query string (?hello=world)
  const parsedSearch = qs.parse(queryString, { parseArrays: false });

  // Pull errorCode off of params
  const errorCode = (parsedSearch.errorCode ?? null) as string | null;
  invariant(
    typeof errorCode === 'string' || errorCode === null,
    `The "errorCode" parameter must be a string if specified`
  );
  delete parsedSearch.errorCode;

  // Get hash (#abc=example)
  let parsedHash = {};
  if (parts[1]) {
    parsedHash = qs.parse(hash);
  }

  // Merge search and hash
  const params = {
    ...parsedSearch,
    ...parsedHash,
  };

  return {
    errorCode,
    params,
  };
}