/**
 * Event Bus
 *
 * Internal event routing between state broadcaster middleware and SSE streams.
 */

import { EventEmitter } from "events";
import type { StateChangedEvent, ExecutionLifecycleEvent } from "../types.ts";

/**
 * Create an event bus for internal routing
 *
 * Events flow:
 *   State Broadcaster Middleware -> EventBus -> SSE Route Handler
 */
export function createEventBus(): EventEmitter {
  const emitter = new EventEmitter();

  // Allow many listeners (one per SSE connection)
  emitter.setMaxListeners(1000);

  return emitter;
}

/**
 * Subscribe to state change events
 */
export function onStateChanged(
  bus: EventEmitter,
  handler: (event: StateChangedEvent) => void
): () => void {
  bus.on("state.changed", handler);
  return () => bus.off("state.changed", handler);
}

/**
 * Subscribe to execution lifecycle events
 */
export function onExecutionLifecycle(
  bus: EventEmitter,
  handler: (event: ExecutionLifecycleEvent) => void
): () => void {
  bus.on("execution.lifecycle", handler);
  return () => bus.off("execution.lifecycle", handler);
}

/**
 * Emit a state change event
 */
export function emitStateChanged(
  bus: EventEmitter,
  event: StateChangedEvent
): void {
  bus.emit("state.changed", event);
}

/**
 * Emit an execution lifecycle event
 */
export function emitExecutionLifecycle(
  bus: EventEmitter,
  event: ExecutionLifecycleEvent
): void {
  bus.emit("execution.lifecycle", event);
}