const MAX_UPDATES_BANKED: number = 20.0;

// always run physics at 240 hz
const UPDATES_PER_MS: number = 1/(1000.0/240.0);

class Clock {
  #lastTimestamp: number | undefined;
  #updatesBanked: number

  constructor() {
    this.#lastTimestamp = undefined;
    this.#updatesBanked = 0.0
  }


  recordTimestamp(timestamp: number) {
    if (this.#lastTimestamp) {
      let delta = timestamp - this.#lastTimestamp;
      this.#bankDelta(delta);
    }
    this.#lastTimestamp = timestamp;
  }

  popUpdate() {
    // return true if we should do an update right now
    // and remove one draw from the bank
    if (this.#updatesBanked > 1) {
      this.#updatesBanked -= 1;
      return true
    }
    return false;
  }
  #bankDelta(delta: number) {
    this.#updatesBanked = Math.min(delta * UPDATES_PER_MS, MAX_UPDATES_BANKED);
  }
}

let active: Clock = new Clock();

export function getClock(): Clock {
  return active;
}