/**
 * AKSRT Section Navs — legacy section_navs parity (posts-nav-lists + scrollspy).
 *
 * Builds TOC from [data-nav] h1–h4 into .posts-nav-box / .posts-nav-lists.
 *
 * @package AKSRT
 */
(function () {
  'use strict';

  var HEADING_SEL = 'h1, h2, h3, h4';
  var MIN_HEADINGS = 2;
  var NAVBOX = '.posts-nav-box';
  var NAV_CLASS = 'posts-nav-lists';

  function isExcluded(el) {
    return el.classList.contains('item-heading') || !!el.closest('.no-nav');
  }

  function ensureId(el, index) {
    if (!el.id) {
      el.id = 'section-nav-' + index;
    }
    return el.id;
  }

  function buildLists(root) {
    var headings = root.querySelectorAll(HEADING_SEL);
    var html = '';
    var count = 0;
    headings.forEach(function (h, i) {
      if (isExcluded(h)) return;
      var id = ensureId(h, i);
      var tag = h.tagName.toUpperCase();
      var text = (h.textContent || '').trim();
      if (!text) return;
      html += '<li class="n-' + tag + '"><a href="#' + id + '">' + text + '</a></li>';
      count++;
    });
    return count >= MIN_HEADINGS ? html : '';
  }

  function fillBoxes(listsHtml) {
    document.querySelectorAll(NAVBOX).forEach(function (box) {
      var existing = box.querySelector('.' + NAV_CLASS);
      if (existing) {
        existing.innerHTML = listsHtml;
        return;
      }
      var title = box.getAttribute('data-title') || '';
      var titleHtml = title
        ? '<div class="box-body notop"><div class="title-theme">' + title + '</div></div>'
        : '';
      box.insertAdjacentHTML(
        'beforeend',
        titleHtml +
          '<div class="aksrt-panel"><div class="' +
          NAV_CLASS +
          ' scroll-y mini-scrollbar list-unstyled">' +
          listsHtml +
          '</div></div>'
      );
    });
  }

  function smoothTo(hash) {
    var el = document.querySelector(hash);
    if (!el) return;
    var offset = 0;
    var header = document.querySelector('.header');
    if (document.body.classList.contains('nav-fixed') && header) {
      offset = header.offsetHeight + 12;
    }
    var top = el.getBoundingClientRect().top + window.pageYOffset - offset;
    window.scrollTo({ top: top, behavior: 'smooth' });
  }

  function bindClicks() {
    document.addEventListener('click', function (e) {
      var a = e.target && e.target.closest ? e.target.closest('.' + NAV_CLASS + ' a[href^="#"]') : null;
      if (!a) return;
      var href = a.getAttribute('href');
      if (!href || href.length < 2) return;
      e.preventDefault();
      history.replaceState(null, '', href);
      smoothTo(href);
    });
  }

  function scrollspy() {
    var links = document.querySelectorAll('.' + NAV_CLASS + ' a[href^="#"]');
    if (!links.length) return;
    var map = [];
    links.forEach(function (a) {
      var id = a.getAttribute('href').slice(1);
      var el = document.getElementById(id);
      if (el) map.push({ el: el, a: a, li: a.parentElement });
    });
    function update() {
      var y = window.scrollY + 110;
      var current = null;
      for (var i = 0; i < map.length; i++) {
        if (map[i].el.offsetTop <= y) current = map[i];
      }
      map.forEach(function (m) {
        if (m.li) m.li.classList.toggle('active', m === current);
      });
    }
    window.addEventListener('scroll', update, { passive: true });
    update();
  }

  function autoHash() {
    if (window.location.hash) {
      setTimeout(function () {
        smoothTo(window.location.hash);
      }, 40);
    }
  }

  function init() {
    if (document.querySelector('.posts-nav-box .toc-list, .posts-nav-box.toc-widget .toc-list')) {
      return;
    }
    var root = document.querySelector('[data-nav], .article-content, .entry-content, main.article');
    if (!root) return;
    var listsHtml = buildLists(root);
    if (!listsHtml) return;
    if (!document.querySelector(NAVBOX) && !document.querySelector('.' + NAV_CLASS)) {
      return;
    }
    fillBoxes(listsHtml);
    bindClicks();
    scrollspy();
    autoHash();
  }

  if (window.AksrtFrontend && typeof window.AksrtFrontend.register === 'function') {
    window.AksrtFrontend.register('aksrt-section-navs', function () {
      init();
    });
  } else if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', init);
  } else {
    init();
  }
})();