js-waku/packages/core/src/lib/base_protocol.ts

import type { Connection, Stream } from "@libp2p/interface-connection";
import type { PeerId } from "@libp2p/interface-peer-id";
import { Peer, PeerStore } from "@libp2p/interface-peer-store";
import {
  getPeersForProtocol,
  selectConnection,
  selectPeerForProtocol,
} from "@waku/utils/libp2p";

/**
 * A class with predefined helpers, to be used as a base to implement Waku
 * Protocols.
 */
export class BaseProtocol {
  constructor(
    public multicodec: string,
    public peerStore: PeerStore,
    protected getConnections: (peerId?: PeerId) => Connection[]
  ) {}

  /**
   * Returns known peers from the address book (`libp2p.peerStore`) that support
   * the class protocol. Waku may or may not be currently connected to these
   * peers.
   */
  async peers(): Promise<Peer[]> {
    return getPeersForProtocol(this.peerStore, [this.multicodec]);
  }

  protected async getPeer(peerId?: PeerId): Promise<Peer> {
    const { peer } = await selectPeerForProtocol(
      this.peerStore,
      [this.multicodec],
      peerId
    );
    return peer;
  }
  protected async newStream(peer: Peer): Promise<Stream> {
    const connections = this.getConnections(peer.id);
    const connection = selectConnection(connections);
    if (!connection) {
      throw new Error("Failed to get a connection to the peer");
    }

    return connection.newStream(this.multicodec);
  }
}