source: frontend/node_modules/webpack-dev-server/client/utils/createSocketURL.js

/**
 * @param {{ protocol?: string, auth?: string, hostname?: string, port?: string, pathname?: string, search?: string, hash?: string, slashes?: boolean }} objURL
 * @returns {string}
 */
function format(objURL) {
  var protocol = objURL.protocol || "";
  if (protocol && protocol.substr(-1) !== ":") {
    protocol += ":";
  }
  var auth = objURL.auth || "";
  if (auth) {
    auth = encodeURIComponent(auth);
    auth = auth.replace(/%3A/i, ":");
    auth += "@";
  }
  var host = "";
  if (objURL.hostname) {
    host = auth + (objURL.hostname.indexOf(":") === -1 ? objURL.hostname : "[".concat(objURL.hostname, "]"));
    if (objURL.port) {
      host += ":".concat(objURL.port);
    }
  }
  var pathname = objURL.pathname || "";
  if (objURL.slashes) {
    host = "//".concat(host || "");
    if (pathname && pathname.charAt(0) !== "/") {
      pathname = "/".concat(pathname);
    }
  } else if (!host) {
    host = "";
  }
  var search = objURL.search || "";
  if (search && search.charAt(0) !== "?") {
    search = "?".concat(search);
  }
  var hash = objURL.hash || "";
  if (hash && hash.charAt(0) !== "#") {
    hash = "#".concat(hash);
  }
  pathname = pathname.replace(/[?#]/g,
  /**
   * @param {string} match
   * @returns {string}
   */
  function (match) {
    return encodeURIComponent(match);
  });
  search = search.replace("#", "%23");
  return "".concat(protocol).concat(host).concat(pathname).concat(search).concat(hash);
}

/**
 * @param {URL & { fromCurrentScript?: boolean }} parsedURL
 * @returns {string}
 */
function createSocketURL(parsedURL) {
  var hostname = parsedURL.hostname;

  // Node.js module parses it as `::`
  // `new URL(urlString, [baseURLString])` parses it as '[::]'
  var isInAddrAny = hostname === "0.0.0.0" || hostname === "::" || hostname === "[::]";

  // why do we need this check?
  // hostname n/a for file protocol (example, when using electron, ionic)
  // see: https://github.com/webpack/webpack-dev-server/pull/384
  if (isInAddrAny && self.location.hostname && self.location.protocol.indexOf("http") === 0) {
    hostname = self.location.hostname;
  }
  var socketURLProtocol = parsedURL.protocol || self.location.protocol;

  // When https is used in the app, secure web sockets are always necessary because the browser doesn't accept non-secure web sockets.
  if (socketURLProtocol === "auto:" || hostname && isInAddrAny && self.location.protocol === "https:") {
    socketURLProtocol = self.location.protocol;
  }
  socketURLProtocol = socketURLProtocol.replace(/^(?:http|.+-extension|file)/i, "ws");
  var socketURLAuth = "";

  // `new URL(urlString, [baseURLstring])` doesn't have `auth` property
  // Parse authentication credentials in case we need them
  if (parsedURL.username) {
    socketURLAuth = parsedURL.username;

    // Since HTTP basic authentication does not allow empty username,
    // we only include password if the username is not empty.
    if (parsedURL.password) {
      // Result: <username>:<password>
      socketURLAuth = socketURLAuth.concat(":", parsedURL.password);
    }
  }

  // In case the host is a raw IPv6 address, it can be enclosed in
  // the brackets as the brackets are needed in the final URL string.
  // Need to remove those as url.format blindly adds its own set of brackets
  // if the host string contains colons. That would lead to non-working
  // double brackets (e.g. [[::]]) host
  //
  // All of these web socket url params are optionally passed in through resourceQuery,
  // so we need to fall back to the default if they are not provided
  var socketURLHostname = (hostname || self.location.hostname || "localhost").replace(/^\[(.*)\]$/, "$1");
  var socketURLPort = parsedURL.port;
  if (!socketURLPort || socketURLPort === "0") {
    socketURLPort = self.location.port;
  }

  // If path is provided it'll be passed in via the resourceQuery as a
  // query param so it has to be parsed out of the querystring in order for the
  // client to open the socket to the correct location.
  var socketURLPathname = "/ws";
  if (parsedURL.pathname && !parsedURL.fromCurrentScript) {
    socketURLPathname = parsedURL.pathname;
  }
  return format({
    protocol: socketURLProtocol,
    auth: socketURLAuth,
    hostname: socketURLHostname,
    port: socketURLPort,
    pathname: socketURLPathname,
    slashes: true
  });
}
export default createSocketURL;