type Listener = (...args: any[]) => void;

/**
 * 轻量事件总线（可替换）：默认本地发布订阅
 * - 迁移到有全局 EventBus 的项目时，可替换为项目总线
 */
export class PortableEventBus {
  private listeners: Map<string, Set<Listener>> = new Map();

  on(event: string, listener: Listener) {
    if (!this.listeners.has(event)) this.listeners.set(event, new Set());
    this.listeners.get(event)!.add(listener);
  }

  once(event: string, listener: Listener) {
    const wrap: Listener = (...args: any[]) => {
      this.off(event, wrap);
      listener(...args);
    };
    this.on(event, wrap);
  }

  off(event: string, listener: Listener) {
    this.listeners.get(event)?.delete(listener);
  }

  emit(event: string, ...args: any[]) {
    const set = this.listeners.get(event);
    if (!set) return;
    for (const l of Array.from(set)) {
      try { l(...args); } catch { /* swallow */ }
    }
  }
}

export const BulletEvents = {
  BULLET_CREATE_REQUEST: 'BULLET_CREATE_REQUEST',
  BULLET_HIT: 'BULLET_HIT',
  BULLET_DESTROY: 'BULLET_DESTROY'
} as const;