import { URL } from 'url';

type PageData = Pick<URL, 'host' | 'pathname'>;

/**
 * Given a list of paths, provides a minimal list of paths that would serve
 * as prefixes for all of the provided paths.
 *
 */
export const getMinimumCommonPath = (paths: string[]): string => {
  if (paths.length === 0) {
    return '/';
  }
  return paths.reduce((prev, path) => {
    const segments = path.split('/');
    const prevSegments = prev.split('/');
    const commonSegments = new Array<string>();
    prevSegments.forEach((segment, index) => {
      if (segments[index] == segment && commonSegments.length === index) {
        commonSegments.push(segment);
      }
    }, []);
    const commonSegmentsAsString = commonSegments.join('/');
    return commonSegmentsAsString.length === 0 ? '/' : commonSegmentsAsString;
  }, paths[0]);
};

/**
 * Takes a list of urls and provides a minimal set of hosts and pathnames that
 * could be used to determine the minimal path to capture all of the paths,
 * grouped by hostname.
 */
export const getMinimumPageURLs = (urls: PageData[]): PageData[] => {
  const hosts = Array.from(new Set(urls.map(({ host }) => host)));
  return hosts.map((host) => {
    const allPathnames = Array.from(
      new Set(
        urls.filter((url) => host === url.host).map(({ pathname }) => pathname)
      )
    );
    const pathname = getMinimumCommonPath(allPathnames);
    return { host, pathname };
  });
};