import type { Subscriber, Unsubscriber } from "svelte/store";

export class Standalone {
  private static instance: Standalone;
  private _standalone = $state(false);
  private subscribers = new Set<Subscriber<boolean>>();

  private constructor() {}

  public static getInstance(): Standalone {
    if (!Standalone.instance) {
      Standalone.instance = new Standalone();
    }
    return Standalone.instance;
  }

  public setStandalone(value: boolean) {
    this._standalone = value;
    this.subscribers.forEach((subscriber) => subscriber(value));
  }

  public get standalone() {
    return this._standalone;
  }

  public subscribe(run: Subscriber<boolean>): Unsubscriber {
    this.subscribers.add(run);
    run(this._standalone);

    return () => {
      this.subscribers.delete(run);
    };
  }
}

export const standalone = Standalone.getInstance();