class EventBus {
  constructor() {
    this.listeners = new Map();
  }

  on(event, handler) {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, []);
    }
    this.listeners.get(event).push(handler);
  }

  off(event, handler) {
    if (!handler) {
      this.listeners.delete(event);
      return;
    }
    const handlers = this.listeners.get(event);
    if (handlers) {
      const idx = handlers.indexOf(handler);
      if (idx !== -1) handlers.splice(idx, 1);
    }
  }

  emit(event, payload) {
    const handlers = this.listeners.get(event);
    if (!handlers) return;
    for (const handler of handlers) {
      try {
        handler(payload);
      } catch (err) {
        console.error(`[EventBus] Error in handler for "${event}":`, err);
      }
    }
  }

  hasHandler(event) {
    const handlers = this.listeners.get(event);
    return handlers !== undefined && handlers !== null && handlers.length > 0;
  }
}

module.exports = { EventBus };