/**
 * Pure formatting helpers for the admission queue UI (spec `docs/QUEUE_SPECIFICATION.md` §7.2, §7.3).
 * Deliberately framework- and DOM-free so they can be unit tested without a browser; the DOM
 * wiring and polling state machine live in app.js.
 */

export const QUEUE_POLL_INTERVAL_MS = 2000;

/**
 * English ordinal suffix for a 1-based rank: 1st, 2nd, 3rd, 4th, 11th-13th, 21st, ...
 * @param {number} n
 * @returns {string}
 */
export function ordinal(n) {
  const rem100 = n % 100;
  if (rem100 >= 11 && rem100 <= 13) return `${n}th`;
  switch (n % 10) {
    case 1: return `${n}st`;
    case 2: return `${n}nd`;
    case 3: return `${n}rd`;
    default: return `${n}th`;
  }
}

/**
 * Formats the estimate clause: "estimating…" when unknown, "under a minute" below 60s,
 * otherwise "about N min" rounded up (spec §5, §7.2).
 * @param {number|null|undefined} etaSeconds
 * @returns {string}
 */
export function formatEta(etaSeconds) {
  if (etaSeconds === null || etaSeconds === undefined) return 'estimating…';
  if (etaSeconds < 60) return 'under a minute';
  const minutes = Math.ceil(etaSeconds / 60);
  return `about ${minutes} min`;
}

/**
 * Formats the queued sub-state status line (spec §7.2 table, `queued` row).
 * Position 1 reads as "You're next" instead of "You're 1st in line".
 * @param {{ position: number, eta_seconds: number|null }} status
 * @returns {string}
 */
export function formatQueuedStatus({ position, eta_seconds: etaSeconds }) {
  const place = position === 1 ? "You're next" : `You're ${ordinal(position)} in line`;
  return `${place} · ${formatEta(etaSeconds)}`;
}

/**
 * Formats the "Exit queue" button's visible label based on time waited since the join
 * response (spec §7.3). The button's `aria-label` stays "Leave the queue" regardless.
 * @param {number} waitedMs
 * @returns {string}
 */
export function formatExitQueueLabel(waitedMs) {
  const waitedMinutes = waitedMs / 60000;
  if (waitedMinutes < 1) return 'I will try next time';
  if (waitedMinutes <= 3) return "Ohhh, it's so long";
  return "I'm dying in this queue";
}