import {compose, EventEmitter, Property} from '@avocado/core';
import {Ticker} from '@avocado/timing';

const decorate = compose(
  EventEmitter,
  Property('count', {
    track: true,
  }),
  Property('jitter', {
    track: true,
  }),
);

export class CycleTracker extends decorate(class {}) {

  constructor(targetFrequency) {
    super();
    this.count = 0;
    this.jitter = [0, 0];
    this.targetFrequency = targetFrequency;
    this.ticker = new Ticker(.25);
    this.trackCount = 0;
    this.trackJitter = [0, 0];
    this.ticker.on('tick', this.onTick, this);
  }

  onTick() {
    this.count = this.trackCount * 4;
    this.trackCount = 0;
    this.jitter = this.trackJitter;
    this.trackJitter = [0, 0];
    this.emit('updated');
  }

  sample(elapsed) {
    this.trackCount += 1;
    const jitter = elapsed - this.targetFrequency;
    if (jitter < 0 && elapsed < this.trackJitter[0]) {
      this.trackJitter[0] = Math.round(1000 * jitter) / 1000;
    }
    if (jitter > 0 && elapsed > this.trackJitter[1]) {
      this.trackJitter[1] = Math.round(1000 * jitter) / 1000;
    }
    this.ticker.tick(elapsed);
  }
}