// Formatting and screen-reader helpers shared by every module. A leaf: it
// imports nothing, so any module can use it without creating a cycle.

export const $ = id => document.getElementById(id);

export const esc = s => String(s)
  .replace(/&/g, '&amp;').replace(/</g, '&lt;')
  .replace(/>/g, '&gt;').replace(/"/g, '&quot;');

export const pad = n => String(n).padStart(2, '0');

export const fmtDur = s => {
  if (s == null) return '—';
  const h = Math.floor(s / 3600), m = Math.floor((s % 3600) / 60), sec = Math.floor(s % 60);
  return h ? `${h}:${pad(m)}:${pad(sec)}` : `${m}:${pad(sec)}`;
};

// "2 h 59 min" — for running text a screen reader speaks, where "2:59:59"
// reads like a clock time
export const fmtDurWords = s => {
  const h = Math.floor(s / 3600), m = Math.floor((s % 3600) / 60);
  if (h) return m ? `${h} h ${m} min` : `${h} h`;
  return m ? `${m} min` : `${Math.round(s)} s`;
};

export const fmtSize = b => {
  if (b < 1024) return b + ' B';
  if (b < 1 << 20) return (b / 1024).toFixed(0) + ' KB';
  if (b < 1 << 30) return (b / (1 << 20)).toFixed(1) + ' MB';
  return (b / (1 << 30)).toFixed(2) + ' GB';
};

// Epoch seconds -> local wall-clock "HH:MM:SS"
export const fmtClock = ts => {
  const d = new Date(ts * 1000);
  return pad(d.getHours()) + ':' + pad(d.getMinutes()) + ':' + pad(d.getSeconds());
};

// Epoch seconds -> local "HH:MM"
export const fmtHM = ts => {
  const d = new Date(ts * 1000);
  return pad(d.getHours()) + ':' + pad(d.getMinutes());
};

// Listing `date` ("YYYY-MM-DD HH:MM:SS", the recording start parsed out of
// the filename server-side) -> epoch seconds, or null for unparseable values
export const fileStartEpoch = date => {
  const t = Date.parse(String(date).replace(' ', 'T'));
  return isNaN(t) ? null : t / 1000;
};

// "1:30", "0:01:30" or "90" -> seconds; null when unparseable
export function parseTime(s) {
  if (!s || !s.trim()) return null;
  const parts = s.trim().split(':').map(v => parseFloat(v));
  if (parts.some(isNaN) || parts.length > 3) return null;
  if (parts.length === 3) return parts[0] * 3600 + parts[1] * 60 + parts[2];
  if (parts.length === 2) return parts[0] * 60 + parts[1];
  return parts[0];
}

// "2026-10-17" -> "Today, Saturday 17 October". Spoken far better than the
// ISO date, which screen readers read digit group by digit group. en-GB to
// match the page's lang="en", so the speech language never switches mid-page.
export function dayLabel(day) {
  const [y, m, d] = day.split('-').map(Number);
  const date = new Date(y, m - 1, d);
  if (isNaN(date)) return day;
  const now = new Date();
  const opts = {weekday: 'long', day: 'numeric', month: 'long'};
  if (y !== now.getFullYear()) opts.year = 'numeric';
  const text = date.toLocaleDateString('en-GB', opts);
  // Math.round absorbs the 23/25 h days around DST switches
  const ago = Math.round((new Date(now.getFullYear(), now.getMonth(), now.getDate()) - date) / 86400000);
  return ago === 0 ? 'Today, ' + text : ago === 1 ? 'Yesterday, ' + text : text;
}

export function announce(msg) {
  const el = $('sr-announce');
  if (!el) return;
  el.textContent = '';                     // clear first so same text re-triggers
  setTimeout(() => { el.textContent = msg; }, 50);
}

// A long chip list is a wall of buttons: hide it behind an aria-expanded
// toggle. Returns the toggle to insert before the chips, or null when the list
// is short enough to show as is. The separator space lives inside the
// aria-hidden arrow — a leading space in the text node reads as an indent.
export function chipToggle(chips, text) {
  if (chips.children.length <= 12) return null;
  chips.hidden = true;
  const tog = document.createElement('button');
  tog.className = 'chip-toggle';
  tog.setAttribute('aria-expanded', 'false');
  const arrow = document.createElement('span');
  arrow.className = 'day-arrow';
  arrow.setAttribute('aria-hidden', 'true');
  arrow.textContent = '▸ ';
  tog.append(arrow, text);
  tog.addEventListener('click', () => {
    const exp = chips.hidden;
    chips.hidden = !exp;
    tog.setAttribute('aria-expanded', exp);
    arrow.textContent = exp ? '▾ ' : '▸ ';
  });
  return tog;
}

// localStorage for per-browser conveniences (pre-roll, auto-advance, whether
// the settings are open). It can be missing or throw (private mode, blocked
// storage), and nothing here may depend on it working.
export const remember = {
  get(key) { try { return localStorage.getItem('isr.' + key); } catch { return null; } },
  set(key, value) { try { localStorage.setItem('isr.' + key, value); } catch { /* not kept */ } },
};