(function () {
  const DESKTOP_COLLAPSE_LIMIT = 10;
  const MOBILE_COLLAPSE_LIMIT = 8;

  function initApplicationPage() {
    const page = document.querySelector(".application-page");
    if (!page) return;

    const tabsNav = page.querySelector(".app-category-tabs");
    const tabs = page.querySelectorAll(".app-category-tab");
    const sections = page.querySelectorAll(".app-list-section[data-total]");
    if (!tabs.length || !sections.length) return;

    let isProgrammaticScroll = false;
    let scrollTimer = null;

    function isDesktop() {
      return window.matchMedia("(min-width: 768px)").matches;
    }

    function getCollapseLimit() {
      return isDesktop() ? DESKTOP_COLLAPSE_LIMIT : MOBILE_COLLAPSE_LIMIT;
    }

    function getScrollOffset() {
      const header = document.querySelector(".site-header");
      const barHeight = (header && header.getBoundingClientRect().height) || (isDesktop() ? 72 : 56);
      return barHeight + (isDesktop() ? 24 : 12);
    }

    function getSectionAnchor(section) {
      return section.querySelector(".app-list-section__head") || section;
    }

    function setActiveTab(activeTab) {
      tabs.forEach((tab) => {
        const isActive = tab === activeTab;
        tab.classList.toggle("app-category-tab--active", isActive);
        tab.setAttribute("aria-selected", isActive ? "true" : "false");
      });
    }

    function updateActionButton(button, expanded, limit) {
      const label = button.querySelector(".app-list-section__more-label");
      const icon = button.querySelector(".app-list-section__more-icon");
      const total = Number(button.dataset.total) || 0;
      const hiddenCount = Math.max(total - limit, 0);

      if (label) {
        label.textContent = expanded ? "收起" : `显示全部${hiddenCount}个站点`;
      }
      if (icon) {
        icon.classList.toggle("app-list-section__more-icon--up", expanded);
      }
      button.setAttribute("aria-expanded", expanded ? "true" : "false");
    }

    function updateCollapseSections() {
      const limit = getCollapseLimit();

      page.querySelectorAll(".app-list-section[data-total]").forEach((section) => {
        const total = Number(section.dataset.total) || 0;
        const button = section.querySelector(".app-list-section__more");
        const needsCollapse = total > limit;

        section.classList.toggle("app-list-section--collapsible", needsCollapse);

        if (!needsCollapse) {
          section.classList.remove("app-list-section--expanded");
        }

        if (button) {
          button.hidden = !needsCollapse;
          if (needsCollapse) {
            updateActionButton(button, section.classList.contains("app-list-section--expanded"), limit);
          }
        }
      });
    }

    function scrollTabIntoView(tab) {
      if (!tabsNav || !tab) return;
      const navRect = tabsNav.getBoundingClientRect();
      const tabRect = tab.getBoundingClientRect();
      const nextLeft = tabsNav.scrollLeft + (tabRect.left - navRect.left) - (navRect.width - tabRect.width) / 2;
      tabsNav.scrollTo({ left: Math.max(0, nextLeft), behavior: "smooth" });
    }

    function scrollToSection(section) {
      if (!section) return;
      const anchor = getSectionAnchor(section);
      const top = anchor.getBoundingClientRect().top + window.scrollY - getScrollOffset();
      isProgrammaticScroll = true;
      clearTimeout(scrollTimer);
      window.scrollTo({ top: Math.max(0, top), behavior: "smooth" });
      scrollTimer = window.setTimeout(() => {
        isProgrammaticScroll = false;
      }, 800);
    }

    tabs.forEach((tab, index) => {
      if (!tab.hasAttribute("aria-selected")) {
        tab.setAttribute("aria-selected", index === 0 ? "true" : "false");
      }

      tab.addEventListener("click", () => {
        const targetId = tab.dataset.target;
        if (!targetId) return;

        setActiveTab(tab);
        scrollTabIntoView(tab);
        scrollToSection(document.getElementById(targetId));
      });
    });

    page.querySelectorAll(".app-list-section__more").forEach((button) => {
      button.addEventListener("click", () => {
        const section = button.closest(".app-list-section");
        if (!section || button.hidden) return;

        const expanded = section.classList.toggle("app-list-section--expanded");
        updateActionButton(button, expanded, getCollapseLimit());
      });
    });

    updateCollapseSections();
    window.addEventListener("resize", updateCollapseSections);

    if (!("IntersectionObserver" in window)) return;

    const observer = new IntersectionObserver(
      (entries) => {
        if (isProgrammaticScroll) return;

        const visible = entries
          .filter((entry) => entry.isIntersecting)
          .sort((a, b) => b.intersectionRatio - a.intersectionRatio);

        if (!visible.length) return;

        const activeTab = page.querySelector(`.app-category-tab[data-target="${visible[0].target.id}"]`);
        if (activeTab) {
          setActiveTab(activeTab);
        }
      },
      {
        rootMargin: `-${getScrollOffset()}px 0px -55% 0px`,
        threshold: [0, 0.25, 0.5, 0.75, 1],
      }
    );

    sections.forEach((section) => observer.observe(section));
  }

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", initApplicationPage);
  } else {
    initApplicationPage();
  }
})();