Method on

packages/db/src/event-emitter.ts:17–29

* Subscribe to an event * @param event - Event name to listen for * @param callback - Function to call when event is emitted * @returns Unsubscribe function

(
    event: T,
    callback: (event: TEvents[T]) => void,
  )

   * @returns Unsubscribe function
   */
  on<T extends keyof TEvents>(
    event: T,
    callback: (event: TEvents[T]) => void,
  ): () => void {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, new Set())
    }
    this.listeners.get(event)!.add(callback as (event: any) => void)

    return () => {
      this.listeners.get(event)?.delete(callback as (event: any) => void)
    }
  }

  /**
   * Subscribe to an event once (automatically unsubscribes after first emission)