js-waku/packages/sdk/src/protocols/base_protocol.ts

import type { Peer, PeerId } from "@libp2p/interface";
import { ConnectionManager } from "@waku/core";
import { BaseProtocol } from "@waku/core/lib/base_protocol";
import { IBaseProtocolSDK, SendOptions } from "@waku/interfaces";
import { delay, Logger } from "@waku/utils";

interface Options {
  numPeersToUse?: number;
  maintainPeersInterval?: number;
}

const DEFAULT_NUM_PEERS_TO_USE = 3;
const DEFAULT_MAINTAIN_PEERS_INTERVAL = 30_000;

export class BaseProtocolSDK implements IBaseProtocolSDK {
  public readonly numPeersToUse: number;
  private peers: Peer[] = [];
  private maintainPeersIntervalId: ReturnType<
    typeof window.setInterval
  > | null = null;
  log: Logger;

  private maintainPeersLock = false;

  constructor(
    protected core: BaseProtocol,
    private connectionManager: ConnectionManager,
    options: Options
  ) {
    this.log = new Logger(`sdk:${core.multicodec}`);
    this.numPeersToUse = options?.numPeersToUse ?? DEFAULT_NUM_PEERS_TO_USE;
    const maintainPeersInterval =
      options?.maintainPeersInterval ?? DEFAULT_MAINTAIN_PEERS_INTERVAL;

    void this.startMaintainPeersInterval(maintainPeersInterval);
  }

  get connectedPeers(): Peer[] {
    return this.peers;
  }

  /**
   * Disconnects from a peer and tries to find a new one to replace it.
   * @param peerToDisconnect The peer to disconnect from.
   */
  public async renewPeer(peerToDisconnect: PeerId): Promise<void> {
    this.log.info(`Renewing peer ${peerToDisconnect}`);
    try {
      await this.connectionManager.dropConnection(peerToDisconnect);
      this.peers = this.peers.filter((peer) => peer.id !== peerToDisconnect);
      this.log.info(
        `Peer ${peerToDisconnect} disconnected and removed from the peer list`
      );

      await this.findAndAddPeers(1);
    } catch (error) {
      this.log.info(
        "Peer renewal failed, relying on the interval to find a new peer"
      );
    }
  }

  /**
   * Stops the maintain peers interval.
   */
  public stopMaintainPeersInterval(): void {
    if (this.maintainPeersIntervalId) {
      clearInterval(this.maintainPeersIntervalId);
      this.maintainPeersIntervalId = null;
      this.log.info("Maintain peers interval stopped");
    }
  }

  /**
   * Checks if there are peers to send a message to.
   * If `forceUseAllPeers` is `false` (default) and there are connected peers, returns `true`.
   * If `forceUseAllPeers` is `true` or there are no connected peers, tries to find new peers from the ConnectionManager.
   * If `autoRetry` is `false`, returns `false` if no peers are found.
   * If `autoRetry` is `true`, tries to find new peers from the ConnectionManager with exponential backoff.
   * Returns `true` if peers are found, `false` otherwise.
   * @param options Optional options object
   * @param options.autoRetry Optional flag to enable auto-retry with exponential backoff (default: false)
   * @param options.forceUseAllPeers Optional flag to force using all available peers (default: false)
   * @param options.initialDelay Optional initial delay in milliseconds for exponential backoff (default: 10)
   * @param options.maxAttempts Optional maximum number of attempts for exponential backoff (default: 3)
   * @param options.maxDelay Optional maximum delay in milliseconds for exponential backoff (default: 100)
   */
  protected hasPeers = async (
    options: Partial<SendOptions> = {}
  ): Promise<boolean> => {
    const {
      autoRetry = false,
      forceUseAllPeers = false,
      initialDelay = 10,
      maxAttempts = 3,
      maxDelay = 100
    } = options;

    if (!forceUseAllPeers && this.connectedPeers.length > 0) return true;

    let attempts = 0;
    while (attempts < maxAttempts) {
      attempts++;
      if (await this.maintainPeers()) {
        if (this.peers.length < this.numPeersToUse) {
          this.log.warn(
            `Found only ${this.peers.length} peers, expected ${this.numPeersToUse}`
          );
        }
        return true;
      }
      if (!autoRetry) return false;
      const delayMs = Math.min(
        initialDelay * Math.pow(2, attempts - 1),
        maxDelay
      );
      await delay(delayMs);
    }

    this.log.error("Failed to find peers to send message to");
    return false;
  };

  /**
   * Starts an interval to maintain the peers list to `numPeersToUse`.
   * @param interval The interval in milliseconds to maintain the peers.
   */
  private async startMaintainPeersInterval(interval: number): Promise<void> {
    this.log.info("Starting maintain peers interval");
    try {
      await this.maintainPeers();
      this.maintainPeersIntervalId = setInterval(() => {
        this.maintainPeers().catch((error) => {
          this.log.error("Error during maintain peers interval:", error);
        });
      }, interval);
      this.log.info(
        `Maintain peers interval started with interval ${interval}ms`
      );
    } catch (error) {
      this.log.error("Error starting maintain peers interval:", error);
      throw error;
    }
  }

  /**
   * Maintains the peers list to `numPeersToUse`.
   */
  private async maintainPeers(): Promise<boolean> {
    if (this.maintainPeersLock) {
      return false;
    }

    this.maintainPeersLock = true;
    this.log.info(`Maintaining peers, current count: ${this.peers.length}`);
    try {
      const numPeersToAdd = this.numPeersToUse - this.peers.length;
      if (numPeersToAdd > 0) {
        await this.findAndAddPeers(numPeersToAdd);
      }
      this.log.info(
        `Peer maintenance completed, current count: ${this.peers.length}`
      );
    } finally {
      this.maintainPeersLock = false;
    }
    return true;
  }

  /**
   * Finds and adds new peers to the peers list.
   * @param numPeers The number of peers to find and add.
   */
  private async findAndAddPeers(numPeers: number): Promise<void> {
    this.log.info(`Finding and adding ${numPeers} new peers`);
    try {
      const additionalPeers = await this.findAdditionalPeers(numPeers);
      this.peers = [...this.peers, ...additionalPeers];
      this.log.info(
        `Added ${additionalPeers.length} new peers, total peers: ${this.peers.length}`
      );
    } catch (error) {
      this.log.error("Error finding and adding new peers:", error);
      throw error;
    }
  }

  /**
   * Finds additional peers.
   * Attempts to find peers without using bootstrap peers first,
   * If no peers are found,
   * tries with bootstrap peers.
   * @param numPeers The number of peers to find.
   */
  private async findAdditionalPeers(numPeers: number): Promise<Peer[]> {
    this.log.info(`Finding ${numPeers} additional peers`);
    try {
      let newPeers = await this.core.getPeers({
        maxBootstrapPeers: 0,
        numPeers: numPeers
      });

      if (newPeers.length === 0) {
        this.log.warn("No new peers found, trying with bootstrap peers");
        newPeers = await this.core.getPeers({
          maxBootstrapPeers: numPeers,
          numPeers: numPeers
        });
      }

      newPeers = newPeers.filter(
        (peer) => this.peers.some((p) => p.id === peer.id) === false
      );
      return newPeers;
    } catch (error) {
      this.log.error("Error finding additional peers:", error);
      throw error;
    }
  }
}