---
import { type Lang } from '@/types/i18n';
import { ScrollArea } from '@/components/ui/scroll-area';

interface Props {
  lang: Lang;
}

const { lang } = Astro.props;
const title = lang === 'zh' ? '目录' : 'Table of Contents';
---

<div>
  <div id="nav-content" class="sticky xl:w-72 w-full top-14">
    <div class="flex flex-col gap-3 p-4">
      <h3 class="dark:text-zinc-200 text-blacktext font-bold tracking-wide text-sm sm:text-base uppercase flex items-center">
        <svg class="w-4 h-4 sm:w-5 sm:h-5 mr-2 text-primary" fill="none" stroke="currentColor" viewBox="0 0 24 24">
          <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 6h16M4 10h16M4 14h16M4 18h16" />
        </svg>
        {title}
      </h3>
      <ScrollArea className="w-full" client:load>
        <div class="text-neutral-500 dark:text-neutral-300 pr-4">
          <ul id="toc-list" class="leading-relaxed text-sm sm:text-base border-l dark:border-neutral-500/20 border-blacktext/20 mt-4">
          </ul>
        </div>
      </ScrollArea>
    </div>
  </div>
</div>

<script>
  /**
   * Initialize table of contents functionality
   * Extracts headings from article content and creates navigation links
   */
  document.addEventListener("DOMContentLoaded", function () {
    const tocList = document.getElementById("toc-list");
    const content = document.querySelector("article");

    if (!tocList || !content) return;

    // Extract h1, h2, h3, h4 headings from article content
    const headers = content.querySelectorAll("h1, h2, h3, h4");
    let currentUl = tocList;

    /**
     * Process each heading and create corresponding TOC entry
     */
    headers.forEach((header, index) => {
      // Generate ID if not present
      if (!header.id) {
        header.id = header.textContent?.trim().toLowerCase().replace(/\s+/g, "-") + "-" + index;
      }

      const li = document.createElement("li");
      const link = document.createElement("a");
      link.href = `#${header.id}`;
      link.textContent = header.textContent?.trim() || header.id;

      // Apply styling based on heading level
      const level = parseInt(header.tagName.charAt(1));
      link.classList.add(
        "block", "w-full", "text-left", "py-1.5", "px-3", "text-sm", 
        "transition-all", "duration-200", "border-l-2", "border-transparent", 
        "text-muted-foreground", "hover:text-foreground", "hover:bg-muted/30"
      );

      // Add indentation based on heading level
      if (level === 1) {
        link.classList.add("font-semibold");
      } else if (level === 2) {
        link.classList.add("ml-2");
      } else if (level === 3) {
        link.classList.add("ml-4");
      } else if (level === 4) {
        link.classList.add("ml-6");
      }

      li.appendChild(link);
      tocList.appendChild(li);

      /**
       * Handle smooth scroll on link click
       */
      link.addEventListener("click", function (e) {
        e.preventDefault();
        const targetElement = document.getElementById(header.id);
        if (targetElement) {
          targetElement.scrollIntoView({ behavior: "smooth", block: "start" });
        }
      });
    });

    /**
     * Set up intersection observer for active section tracking
     * Only highlights the active section without auto-scrolling
     */
    const observer = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          const id = entry.target.getAttribute("id");
          const link = document.querySelector(`#toc-list a[href="#${id}"]`);

          if (entry.isIntersecting) {
            // Remove active state from all links
            document.querySelectorAll("#toc-list a").forEach((el) => {
              el.classList.remove(
                "bg-primary/10", "text-primary", "border-l-primary", "font-medium"
              );
              el.classList.add("text-muted-foreground", "border-transparent");
            });

            // Add active state to current link
            if (link) {
              link.classList.remove("text-muted-foreground", "border-transparent");
              link.classList.add(
                "bg-primary/10", "text-primary", "border-l-primary", "font-medium"
              );
            }
          }
        });
      },
      {
        rootMargin: "-20% 0% -35% 0%",
        threshold: 0
      }
    );

    // Observe all headings for intersection
    headers.forEach((header) => observer.observe(header));
  });
</script>

<style>
  /* Additional styling for smooth transitions */
  #toc-list a:hover {
    transform: translateX(2px);
    background-color: rgba(168, 85, 247, 0.05);
  }
  
  #toc-list a:focus {
    outline: 2px solid rgba(168, 85, 247, 0.3);
    outline-offset: 1px;
  }

  /* Smooth transition for active state */
  #toc-list a {
    position: relative;
    transition: all 0.2s ease;
  }
</style>