/**
 * About Page Animator
 * Cycles an is-active highlight through feature rows in .features-stage.
 * Respects prefers-reduced-motion and pauses via IntersectionObserver.
 * Mirrors the patterns and conventions of solutions-animator.js.
 */
(function () {
  'use strict';

  if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) return;

  var CYCLE_MS = 2000;

  function initFeatures(stage) {
    var items = stage.querySelectorAll('.feat-item');
    if (!items.length) return;

    var state = { idx: 0, timer: null };

    function advance() {
      items[state.idx].classList.remove('is-active');
      state.idx = (state.idx + 1) % items.length;
      items[state.idx].classList.add('is-active');
    }

    function startTimer() {
      if (state.timer) return;
      state.timer = setInterval(advance, CYCLE_MS);
    }

    function stopTimer() {
      clearInterval(state.timer);
      state.timer = null;
    }

    items[0].classList.add('is-active');

    if ('IntersectionObserver' in window) {
      new IntersectionObserver(function (entries) {
        for (var i = 0; i < entries.length; i++) {
          entries[i].isIntersecting ? startTimer() : stopTimer();
        }
      }, { rootMargin: '200px', threshold: 0.05 }).observe(stage);
    } else {
      startTimer();
    }
  }

  function boot() {
    var stages = document.querySelectorAll('.features-stage');
    if (!stages.length) return;
    for (var i = 0; i < stages.length; i++) {
      if (stages[i]._featAnim) continue;
      stages[i]._featAnim = true;
      initFeatures(stages[i]);
    }
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', boot);
  } else {
    boot();
  }
})();