export const CURRENT_DISPLAY_SPEEDS = Object.freeze([0.5, 1, 1.5, 2]);

export function formatPlaybackTime(valueMs) {
  const milliseconds = Math.max(0, Math.floor(Number(valueMs) || 0));
  const minutes = Math.floor(milliseconds / 60000);
  const seconds = Math.floor((milliseconds % 60000) / 1000);
  const hundredths = Math.floor((milliseconds % 1000) / 10);
  return `${minutes}:${String(seconds).padStart(2, "0")}.${String(hundredths).padStart(2, "0")}`;
}

export function projectPlaybackPosition(playback, elapsedMs = 0) {
  if (!playback?.active || !Number.isFinite(Number(playback.total_duration_ms))) return null;
  const total = Math.max(1, Number(playback.total_duration_ms));
  const base = Math.max(0, Number(playback.position_ms) || 0);
  if (playback.paused) return Math.min(total - 1, base);
  const speed = Number(playback.speed) || 1;
  const projected = base + Math.max(0, Number(elapsedMs) || 0) * speed;
  return Math.min(total - 1, projected % total);
}

export class LatestSeekDispatcher {
  constructor(send, {
    intervalMs = 100,
    now = () => performance.now(),
    setTimer = (callback, delay) => window.setTimeout(callback, delay),
    clearTimer = (timer) => window.clearTimeout(timer),
    onError = () => {},
  } = {}) {
    this.send = send;
    this.intervalMs = intervalMs;
    this.now = now;
    this.setTimer = setTimer;
    this.clearTimer = clearTimer;
    this.onError = onError;
    this.inFlight = false;
    this.lastStartedAt = Number.NEGATIVE_INFINITY;
    this.queued = null;
    this.timer = null;
  }

  enqueue(positionMs, { flush = false } = {}) {
    this.queued = { positionMs, flush: flush || Boolean(this.queued?.flush) };
    this.#drain();
  }

  clear() {
    this.queued = null;
    if (this.timer !== null) this.clearTimer(this.timer);
    this.timer = null;
  }

  #drain() {
    if (this.inFlight || this.queued === null) return;
    const waitMs = this.intervalMs - (this.now() - this.lastStartedAt);
    if (!this.queued.flush && waitMs > 0) {
      if (this.timer === null) {
        this.timer = this.setTimer(() => {
          this.timer = null;
          this.#drain();
        }, waitMs);
      }
      return;
    }
    if (this.timer !== null) this.clearTimer(this.timer);
    this.timer = null;
    const item = this.queued;
    this.queued = null;
    this.inFlight = true;
    this.lastStartedAt = this.now();
    Promise.resolve()
      .then(() => this.send(item.positionMs))
      .catch((error) => this.onError(error, item.positionMs))
      .finally(() => {
        this.inFlight = false;
        this.#drain();
      });
  }
}