/**
 * Pure helpers for keeping the player's position variable honest.
 *
 * TRACES: UR-004, UR-041 | DR-265 | UT-245
 *
 * `VideoPlayer.svelte` tracks the absolute playback position in its own
 * `currentTime` variable rather than reading `videoElement.currentTime` at the
 * point of use — transcoded HLS resets the element to 0 on every segment
 * rebuild, so only the component's running total is meaningful. Everything
 * downstream reads that variable: the seek bar, the progress reports, the
 * position mirrored into Rust, and the background-audio handoff.
 *
 * Which makes "who is allowed to write it" a correctness question, not a
 * rendering detail — hence a pure module with tests rather than a condition
 * buried in an event handler.
 */

export interface TimeUpdateGate {
  /**
   * Deliberately does NOT gate the update, and is accepted only to say so.
   *
   * `timeupdate` was written as a fallback "for when RAF isn't running" and so
   * excluded itself whenever `isPlaying` was true. But RAF is driven by the
   * document being rendered, and an Android activity behind a picture-in-picture
   * window is paused: the loop stops while the element plays on, and the one
   * remaining position source had switched itself off. Both writing the same
   * derived value costs nothing — the element is the authority either way.
   */
  isPlaying?: boolean;
  isSeeking: boolean;
  isDraggingSeekBar: boolean;
  readyState: number;
}

/**
 * Whether a `timeupdate` event may write the component's position.
 *
 * Kept free of Svelte/DOM so the rule is unit-testable without mounting the
 * player.
 */
export function shouldApplyTimeUpdate(opts: TimeUpdateGate): boolean {
  // An in-flight seek or a drag owns the position until it settles, and an
  // element with no current data reads 0, which would rewind it.
  return !opts.isSeeking && !opts.isDraggingSeekBar && opts.readyState >= 2;
}