class Timer {
  constructor(options = {}) {
    this.onTick = options.onTick || (() => {})
    this.onComplete = options.onComplete || (() => {})

    this._duration = 0
    this._remaining = 0
    this._elapsed = 0
    this._startTime = 0
    this._pausedTime = 0
    this._intervalId = null
    this._running = false
    this._paused = false
    this._completed = false
  }

  start(duration) {
    this._duration = duration
    this._remaining = duration
    this._elapsed = 0
    this._completed = false
    this._running = true
    this._paused = false
    this._startTime = Date.now()
    this._tick()
    this._intervalId = setInterval(() => { this._tick() }, 1000)
  }

  pause() {
    if (!this._running || this._paused) return
    this._paused = true
    this._pausedTime = Date.now()
    clearInterval(this._intervalId)
    this._intervalId = null
  }

  resume() {
    if (!this._running || !this._paused) return
    this._startTime += Date.now() - this._pausedTime
    this._paused = false
    this._tick()
    this._intervalId = setInterval(() => { this._tick() }, 1000)
  }

  stop() {
    this._running = false
    this._paused = false
    clearInterval(this._intervalId)
    this._intervalId = null
    return this._elapsed
  }

  _tick() {
    if (!this._running || this._paused) return
    this._elapsed = Math.floor((Date.now() - this._startTime) / 1000)
    this._remaining = Math.max(0, this._duration - this._elapsed)

    this.onTick({
      remaining: this._remaining,
      elapsed: this._elapsed,
      duration: this._duration
    })

    if (this._remaining <= 0 && !this._completed) {
      this._completed = true
      this.onComplete({ elapsed: this._elapsed, duration: this._duration })
    }
  }

  get isRunning() { return this._running && !this._paused }
  get isPaused() { return this._paused }
  get isCompleted() { return this._completed }
  get remaining() { return this._remaining }
  get elapsed() { return this._elapsed }
}

module.exports = Timer