/** 追加式事件通道:全部事件保存在内存,支持多个消费者按 seq 回放 + 实时跟随 */
export class EventChannel<T> {
  private readonly items: T[] = [];
  private waiters: Array<() => void> = [];
  private closed = false;

  push(item: T): void {
    if (this.closed) return;
    this.items.push(item);
    this.wake();
  }

  close(): void {
    this.closed = true;
    this.wake();
  }

  get size(): number {
    return this.items.length;
  }

  snapshot(): T[] {
    return [...this.items];
  }

  async *iterate(fromIndex = 0): AsyncGenerator<T> {
    let i = Math.max(0, fromIndex);
    while (true) {
      while (i < this.items.length) yield this.items[i++] as T;
      if (this.closed) return;
      await new Promise<void>((resolve) => this.waiters.push(resolve));
    }
  }

  private wake(): void {
    const waiters = this.waiters;
    this.waiters = [];
    for (const w of waiters) w();
  }
}