/**
 * AKSRT Section Navs — Article TOC / Scrollspy
 *
 * Auto-generates a table of contents from h1~h4 headings within
 * [data-nav] content areas. Scrollspy highlights the current section.
 * Collapsible sub-items when the TOC is tall.
 *
 * @package AKSRT
 */
(function () {
  'use strict';

  var HEADING_SEL = 'h1, h2, h3, h4';
  var MIN_HEADINGS = 2;
  var SCROLL_OFFSET = 105;
  var MAX_HEIGHT_COLLAPSE = 380;

  function initSectionNavs() {
    var navContainer = document.querySelector('[data-nav]');
    if (!navContainer) return;

    // Single-post TOC is owned by page-template.js (.posts-nav-box .toc-list).
    // Do not invent a second .aksrt-section-nav tree on article singles.
    if (document.querySelector('.posts-nav-box .toc-list, .posts-nav-box.toc-widget')) {
      return;
    }

    var headings = navContainer.querySelectorAll(HEADING_SEL);
    if (headings.length < MIN_HEADINGS) return;

    var tocContainer = document.querySelector('.posts-nav-lists, .aksrt-section-nav');
    if (!tocContainer) {
      // Docs / page-navs only: create a dedicated container. Never inject into single sidebars.
      if (document.body.classList.contains('single') || document.body.classList.contains('single-post')) {
        return;
      }
      tocContainer = document.createElement('nav');
      tocContainer.className = 'aksrt-section-nav';
      tocContainer.setAttribute('aria-label', '文章目录');
      var sidebar = document.querySelector('.content-layout__aside, .sidebar, .widget-area');
      if (sidebar) {
        sidebar.insertBefore(tocContainer, sidebar.firstChild);
      } else if (navContainer.parentNode) {
        navContainer.parentNode.insertBefore(tocContainer, navContainer);
      } else {
        return;
      }
    }

    var list = document.createElement('ul');
    list.className = 'aksrt-section-nav__list';

    var items = [];
    headings.forEach(function (heading, i) {
      if (!heading.id) {
        heading.id = 'section-nav-' + i;
      }

      var level = parseInt(heading.tagName.charAt(1), 10);
      var li = document.createElement('li');
      li.className = 'aksrt-section-nav__item aksrt-section-nav__item--h' + level;

      var link = document.createElement('a');
      link.href = '#' + heading.id;
      link.textContent = heading.textContent.trim();
      link.className = 'aksrt-section-nav__link';

      link.addEventListener('click', function (e) {
        e.preventDefault();
        smoothScrollTo(heading);

        // Expand collapsed panels containing the target
        var panel = heading.closest('[data-collapse], .collapse');
        if (panel) {
          panel.classList.add('show', 'is-open');
          var readMore = panel.previousElementSibling;
          if (readMore && readMore.classList.contains('read-more-open')) readMore.click();
        }
      });

      li.appendChild(link);
      list.appendChild(li);
      items.push({ el: heading, link: link, li: li, level: level });
    });

    tocContainer.innerHTML = '';
    tocContainer.appendChild(list);

    // Collapse sub-items if TOC is tall
    if (tocContainer.scrollHeight > MAX_HEIGHT_COLLAPSE) {
      collapseSubItems(list, items);
    }

    // Scrollspy
    var ticking = false;
    function onScroll() {
      if (ticking) return;
      ticking = true;
      requestAnimationFrame(function () {
        ticking = false;
        var scrollTop = window.pageYOffset + SCROLL_OFFSET;
        var activeIdx = 0;
        for (var i = items.length - 1; i >= 0; i--) {
          if (items[i].el.offsetTop <= scrollTop) {
            activeIdx = i;
            break;
          }
        }
        items.forEach(function (item, idx) {
          item.link.classList.toggle('is-active', idx === activeIdx);
        });
      });
    }

    window.addEventListener('scroll', onScroll, { passive: true });
    onScroll();

    // URL hash auto-scroll
    if (window.location.hash) {
      var target = document.querySelector(window.location.hash);
      if (target) setTimeout(function () { smoothScrollTo(target); }, 100);
    }
  }

  function smoothScrollTo(el) {
    if (window.aksrt && aksrt.scrollTopTo) {
      aksrt.scrollTopTo(el);
    } else {
      var top = el.getBoundingClientRect().top + window.pageYOffset - SCROLL_OFFSET;
      window.scrollTo({ top: Math.max(0, top), behavior: 'smooth' });
    }
  }

  function collapseSubItems(list, items) {
    var parentStack = [];
    items.forEach(function (item) {
      while (parentStack.length && parentStack[parentStack.length - 1].level >= item.level) {
        parentStack.pop();
      }

      if (item.level >= 3 && parentStack.length) {
        item.li.classList.add('yc');
        // Add collapse toggle to parent if not already there
        var parentLi = parentStack[parentStack.length - 1].li;
        if (!parentLi.querySelector('.nav-toggle-collapse')) {
          var toggle = document.createElement('span');
          toggle.className = 'nav-toggle-collapse';
          toggle.innerHTML = '<i class="fas fa-chevron-right"></i>';
          toggle.addEventListener('click', function (e) {
            e.stopPropagation();
            toggle.classList.toggle('fa-rotate-90');
            var next = parentLi.nextElementSibling;
            while (next && next.classList.contains('yc')) {
              next.classList.toggle('yc-open');
              next = next.nextElementSibling;
            }
          });
          parentLi.appendChild(toggle);
        }
      }

      parentStack.push(item);
    });
  }

  if (window.AksrtFrontend) {
    AksrtFrontend.register('aksrt-section-navs', function () { initSectionNavs(); });
  }

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