/**
 * Reading the moment a preview is asked for.
 *
 * The whole display pipeline is already a function of "now", so showing the
 * panel as it will be next Tuesday costs nothing but passing a different
 * instant. What it does need is a bound: an unparseable or absurd value
 * should not render a screen for the year 3000 and leave someone believing it.
 */

/** As far ahead or behind as a shop plausibly plans. */
export const PREVIEW_RANGE_DAYS = 400;

export type PreviewTime = { at: Date; isNow: boolean };

export function parsePreviewTime(raw: string | null, now: Date): PreviewTime {
  if (!raw) {
    return { at: now, isNow: true };
  }

  const parsed = new Date(raw);
  if (Number.isNaN(parsed.getTime())) {
    return { at: now, isNow: true };
  }

  const limit = PREVIEW_RANGE_DAYS * 86_400_000;
  const distance = parsed.getTime() - now.getTime();
  if (Math.abs(distance) > limit) {
    return { at: now, isNow: true };
  }

  return { at: parsed, isNow: Math.abs(distance) < 60_000 };
}