This script decodes Google News generated encoded, internal URLs for RSS items

decodeGoogleNewsUrl.ts

/**
 * Google News started generate encoded, internal URLs for RSS items
 * https://news.google.com/rss/search?q=New%20York%20when%3A30d&hl=en-US&gl=US&ceid=US:en
 *
 * This script decodes URLs into original one, for example URL
 * https://news.google.com/__i/rss/rd/articles/CBMiSGh0dHBzOi8vdGVjaGNydW5jaC5jb20vMjAyMi8xMC8yNy9uZXcteW9yay1wb3N0LWhhY2tlZC1vZmZlbnNpdmUtdHdlZXRzL9IBAA?oc=5
 *
 * contains this
 * https://techcrunch.com/2022/10/27/new-york-post-hacked-offensive-tweets/
 *
 * In path after articles/ goes Base64 encoded binary data
 *
 * Format is the following:
 * <prefix> <len bytes> <URL bytes> <len bytes> <amp URL bytes> [<suffix>]
 *
 * <prefix> - 0x08, 0x13, 0x22
 * <suffix> - 0xd2, 0x01, 0x00 (sometimes missing??)
 * <len bytes> - formatted as 0x40 or 0x81 0x01 sometimes
 *
 * FIXME: What will happen if URL more than 255 bytes??
 */
const decodeGoogleNewsUrl = (sourceUrl: string) => {
  const url = new URL(sourceUrl);
  const path = url.pathname.split("/");
  if (
    url.hostname === "news.google.com" &&
    path.length > 1 &&
    path[path.length - 2] === "articles"
  ) {
    const base64 = path[path.length - 1];
    let str = atob(base64);

    const prefix = Buffer.from([0x08, 0x13, 0x22]).toString("binary");
    if (str.startsWith(prefix)) {
      str = str.substring(prefix.length);
    }

    const suffix = Buffer.from([0xd2, 0x01, 0x00]).toString("binary");
    if (str.endsWith(suffix)) {
      str = str.substring(0, str.length - suffix.length);
    }

    // One or two bytes to skip
    const bytes = Uint8Array.from(str, c => c.charCodeAt(0));
    const len = bytes.at(0)!;
    if (len >= 0x80) {
      str = str.substring(2, len + 1);
    } else {
      str = str.substring(1, len + 1);
    }

    return str;
  } else {
    return sourceUrl;
  }
};