class Timer {
  debug: boolean
  callback: (delta: number) => void
  boundTick_: FrameRequestCallback
  lastGameLoopFrame: number
  requestID_: number | undefined
  constructor(callback: (delta: number) => void, debug: boolean) {
    if (typeof callback !== 'function') {
      throw new Error('param \'callback\' has to be a function.')
    }
    this.debug = debug

    this.callback = callback
    this.boundTick_ = this.tick.bind(this)
  }

  start(): void {
    if (!this.requestID_) {
      this.lastGameLoopFrame = new Date().getTime()
      this.tick()
      if (this.debug) console.log('[astrology.Timer] start')
    }
  }

  stop(): void {
    if (this.requestID_) {
      window.cancelAnimationFrame(this.requestID_)
      this.requestID_ = undefined
      if (this.debug) console.log('[astrology.Timer] stop')
    }
  }

  isRunning(): boolean {
    return !!this.requestID_
  }

  tick(): void {
    const now = new Date().getTime()
    this.requestID_ = window.requestAnimationFrame(this.boundTick_)
    this.callback(now - this.lastGameLoopFrame)
    this.lastGameLoopFrame = now
  }
}

export default Timer