sample.ts

class AptosEvent {
  constructor(
    readonly client: AptosClient,
    readonly eventHandlerOwner: HexString,
    readonly eventOwnerStruct: string,
    readonly eventHandlerName: string,
    readonly pollIntervalMs: number = 1000
  ) {}

  async onTrigger(callback: (e: any) => any) {
    // Get the start sequence number in the EVENT STREAM, defaulting to the latest event.
    const [{ sequence_number }] = await this.client.getEventsByEventHandle(
      this.eventHandlerOwner,
      this.eventOwnerStruct,
      this.eventHandlerName,
      { limit: 1 }
    );

    // type for this is string for some reason
    let lastSequenceNumber = sequence_number;

    setInterval(async () => {
      const events = await this.client.getEventsByEventHandle(
        this.eventHandlerOwner,
        this.eventOwnerStruct,
        this.eventHandlerName,
        {
          start: Number(lastSequenceNumber) + 1,
          limit: 500,
        }
      );
      if (events.length !== 0) {
        // increment sequence number
        lastSequenceNumber = events.at(-1)!.sequence_number;
      }
      for (let e of events) {
        // fire off the callback for all new events
        await callback(e);
      }
    }, this.pollIntervalMs);
  }
}

const onAggregatorOpenRound = (
  client: AptosClient,
  cb: EventCallback,
  pollIntervalMs: number = 1000
) => {
  const event = new AptosEvent(
    client,
    HexString.ensure(SWITCHBOARD_STATE_ADDRESS),
    `${SWITCHBOARD_DEVNET_ADDRESS}::Switchboard::State`,
    "aggregator_open_round_events",
    pollIntervalMs
  );
  event.onTrigger(cb);
  return event;
};

const onAggregatorUpdate = (
  client: AptosClient,
  cb: EventCallback,
  pollIntervalMs: number = 1000
) => {
  const event = new AptosEvent(
    client,
    HexString.ensure(SWITCHBOARD_STATE_ADDRESS),
    `${SWITCHBOARD_DEVNET_ADDRESS}::Switchboard::State`,
    "aggregator_update_events",
    pollIntervalMs
  );
  event.onTrigger(cb);
  return event;
};