js-waku/src/lib/discovery/index.ts

import axios from 'axios';
import debug from 'debug';
import { shuffle } from 'libp2p-gossipsub/src/utils';

const dbg = debug('waku:discovery');

const DefaultWantedNumber = 1;

/**
 * GET list of nodes from remote HTTP host.
 *
 * Default behavior is to return nodes hosted by Status.
 *
 * @param path The property path to access the node list. The result should be
 * a string, a string array or an object. If the result is an object then the
 * values of the objects are used as multiaddresses. For example, if the GET
 * request returns `{ foo: { bar: [address1, address2] } }` then `path` should be
 * `[ "foo", "bar" ]`.
 * @param url Remote host containing bootstrap peers in JSON format.
 * @param wantedNumber The number of connections desired. Defaults to [DefaultWantedNumber].
 *
 * @returns An array of multiaddresses.
 * @throws If the remote host is unreachable or the response cannot be parsed
 * according to the passed _path_.
 */
export async function getBootstrapNodes(
  path: string[] = ['fleets', 'wakuv2.prod', 'waku-websocket'],
  url = 'https://fleets.status.im/',
  wantedNumber: number = DefaultWantedNumber
): Promise<string[]> {
  if (wantedNumber <= 0) {
    return [];
  }

  const res = await axios.get(url, {
    headers: { 'Content-Type': 'application/json' },
  });

  let nodes = res.data;

  for (const prop of path) {
    if (nodes[prop] === undefined) {
      dbg(
        `Failed to retrieve bootstrap nodes: ${prop} does not exist on `,
        nodes
      );
      throw `Failed to retrieve bootstrap nodes: ${prop} does not exist on ${JSON.stringify(
        nodes
      )}`;
    }
    nodes = nodes[prop];
  }

  if (Array.isArray(nodes)) {
    return getPseudoRandomSubset(nodes, wantedNumber);
  }

  if (typeof nodes === 'string') {
    return [nodes];
  }

  if (typeof nodes === 'object') {
    nodes = Object.values(nodes);
    return getPseudoRandomSubset(nodes, wantedNumber);
  }

  throw `Failed to retrieve bootstrap nodes: response format is not supported: ${JSON.stringify(
    nodes
  )}`;
}

export function getPseudoRandomSubset(
  values: string[],
  wantedNumber: number
): string[] {
  if (values.length <= wantedNumber) {
    return values;
  }

  return shuffle(values).slice(0, wantedNumber);
}