type EventName = 'process:start' | 'agent:start' | 'step:before' | 'tool:before' | 'tool:after' | 'agent:end';
type Listener = (data: any) => void | Promise<void>;

export class HookBus {
  private listeners = new Map<EventName, Listener[]>();

  on(event: EventName, fn: Listener) {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, []);
    }
    this.listeners.get(event)!.push(fn);
  }

  async emit(event: EventName, data: any) {
    const fns = this.listeners.get(event);
    if (!fns) return;
    for (const fn of fns) {
      await fn(data);
    }
  }
}

export const hooks = new HookBus();