// retoor <retoor@molodetz.nl>
export class Poller {
  constructor(fn, intervalMs, { immediate = false, pauseHidden = true } = {}) {
    this.fn = fn;
    this.intervalMs = intervalMs;
    this.immediate = immediate;
    this.pauseHidden = pauseHidden;
    this.timer = null;
    this.busy = false;
  }

  start() {
    if (this.timer) {
      return this;
    }
    if (this.immediate) {
      this.tick();
    }
    this.timer = setInterval(() => this.tick(), this.intervalMs);
    return this;
  }

  stop() {
    clearInterval(this.timer);
    this.timer = null;
  }

  async tick() {
    if (this.busy || (this.pauseHidden && document.hidden)) {
      return;
    }
    this.busy = true;
    try {
      await this.fn();
    } catch (error) {
      console.debug("poller tick failed", error);
    } finally {
      this.busy = false;
    }
  }
}