/**
 * utils.js
 * --------
 * Pure utility functions with no DOM or state dependencies.
 * Safe to import anywhere without side-effects.
 */

/**
 * Escape a string for safe insertion into HTML.
 * @param {*} str
 * @returns {string}
 */
export function esc(str) {
  if (!str) return '';
  return String(str)
    .replace(/&/g, '&')
    .replace(/</g,  '&lt;')
    .replace(/>/g,  '&gt;')
    .replace(/"/g,  '&quot;')
    .replace(/'/g,  '&#39;');
}

/**
 * Format a duration in seconds as M:SS or H:MM:SS.
 * @param {number} seconds
 * @returns {string}
 */
export function fmtTime(seconds) {
  const s   = Math.floor(seconds);
  const h   = Math.floor(s / 3600);
  const m   = Math.floor((s % 3600) / 60);
  const sec = s % 60;
  return h > 0
    ? `${h}:${pad(m)}:${pad(sec)}`
    : `${m}:${pad(sec)}`;
}

/**
 * Zero-pad a number to at least 2 digits.
 * @param {number} n
 * @returns {string}
 */
export function pad(n) {
  return String(n).padStart(2, '0');
}