/**
 * 简单版 发布订阅
 */

type Listender = (state: any) => void;

class ObserverStateManagerClass {
  private listeners: Array<Listender> = [];
  private state!: any;

  public attach(listener: Listender) {
    this.listeners.push(listener);
  }

  public detach(listenerToRemove: Listender) {
    this.listeners = this.listeners.filter(
      listener => listener !== listenerToRemove,
    );
  }

  public update<T>(state: T) {
    this.state = state;
    this.notify<T>(state);
  }

  private notify<T>(state: T) {
    this.listeners.forEach(listener => listener(state));
  }
}

export const ObserverStateManager = new ObserverStateManagerClass();