@solsdk/jito-ts/src/sdk/geyser/geyser.ts

## What is it and why do you need it?

import {
  ChannelCredentials,
  ChannelOptions,
  ClientReadableStream,
  ServiceError,
} from '@grpc/grpc-js';
import {PublicKey} from '@solana/web3.js';

import {authInterceptor} from './auth';
import {
  GetHeartbeatIntervalResponse,
  GeyserClient as GeyserClientStub,
  TimestampedAccountUpdate,
  TimestampedBlockUpdate,
} from '../../gen/geyser/geyser';

export class GeyserClient {
  private client: GeyserClientStub;

  constructor(client: GeyserClientStub) {
    this.client = client;
  }

  /**
   * Retrieves the heartbeat interval in milliseconds from the server.
   *
   * @returns A Promise that resolves to a number representing the heartbeat interval in milliseconds.
   * @throws A ServiceError if there's an issue with the server while fetching the heartbeat interval.

   */
  async getHeartbeatIntervalMillis(): Promise<number> {
    return new Promise((resolve, reject) => {
      this.client.getHeartbeatInterval(
        {},
        async (e: ServiceError | null, resp: GetHeartbeatIntervalResponse) => {
          if (e) {
            reject(e);
          } else {
            resolve(resp.heartbeatIntervalMs);
          }
        }
      );
    });
  }

  /**
   * Triggers the supplied callback on an update of the provided accounts of interest.
   *
   * @param accountsOfInterest - An array of PublicKeys of the accounts to subscribe for updates.
   * @param successCallback - A callback function that receives a TimestampedAccountUpdate object whenever updates are available.
   * @param errorCallback - A callback function that is triggered whenever an error occurs during the subscription process.
   * @returns A function that can be called to cancel the subscription.
   */
  onAccountUpdate(
    accountsOfInterest: PublicKey[],
    successCallback: (resp: TimestampedAccountUpdate) => void,
    errorCallback: (e: Error) => void
  ): () => void {
    const accounts = accountsOfInterest.map(a => a.toBytes());
    const stream: ClientReadableStream<TimestampedAccountUpdate> =
      this.client.subscribeAccountUpdates({accounts});

    stream.on('readable', () => {
      const msg = stream.read(1);
      if (msg) {
        successCallback(msg);
      }
    });

    stream.on('error', e =>
      errorCallback(new Error(`Stream error: ${e.message}`))
    );

    return () => stream.cancel();
  }

  /**
   * Triggers the supplied callback on an account update owned by the provided programs of interest.
   *
   * @param programsOfInterest - An array of PublicKeys of the programs to subscribe for updates.
   * @param successCallback - A callback function that receives a TimestampedAccountUpdate object whenever updates are available.
   * @param errorCallback - A callback function that is triggered whenever an error occurs during the subscription process.
   * @returns A function that can be called to cancel the subscription.
   */
  onProgramUpdate(
    programsOfInterest: PublicKey[],
    successCallback: (resp: TimestampedAccountUpdate) => void,
    errorCallback: (e: Error) => void
  ): () => void {
    const programs = programsOfInterest.map(a => a.toBytes());
    const stream: ClientReadableStream<TimestampedAccountUpdate> =
      this.client.subscribeProgramUpdates({programs});

    stream.on('readable', () => {
      const msg = stream.read(1);
      if (msg) {
        successCallback(msg);
      }
    });

    stream.on('error', e =>
      errorCallback(new Error(`Stream error: ${e.message}`))
    );

    return () => stream.cancel();
  }

  /**
   * Triggers the supplied callback for every processed block.
   *
   * @param successCallback - A callback function that receives a TimestampedBlockUpdate object whenever a block update is available.
   * @param errorCallback - A callback function that is triggered whenever an error occurs during the subscription process.
   * @returns A function that can be called to cancel the subscription.
   */
  onProcessedBlock(
    successCallback: (resp: TimestampedBlockUpdate) => void,
    errorCallback: (e: Error) => void
  ): () => void {
    const stream: ClientReadableStream<TimestampedBlockUpdate> =
      this.client.subscribeBlockUpdates({});

    stream.on('readable', () => {
      const msg = stream.read(1);
      if (msg) {
        successCallback(msg);
      }
    });

    stream.on('error', e =>
      errorCallback(new Error(`Stream error: ${e.message}`))
    );

    return () => stream.cancel();
  }
}

/**
 * Creates and returns a new GeyserClient instance.
 *
 * @param url - The gRPC server endpoint URL.
 * @param accessToken - The access token required for authentication.
 * @param grpcOptions - Optional configuration options for the gRPC client
 * @returns A GeyserClient instance with the specified configuration.
 */
export const geyserClient = (
  url: string,
  accessToken: string,
  grpcOptions?: Partial<ChannelOptions>
): GeyserClient => {
  const client = new GeyserClientStub(url, ChannelCredentials.createSsl(), {
    interceptors: [authInterceptor(accessToken)],
    ...grpcOptions,
  });

  return new GeyserClient(client);
};