/**
 * Table of Contents for v2 technique pages with nested sections.
 *
 * Renders a nested list of anchor links matching the H2/H3 section structure.
 * Uses slugified headings as IDs for scroll targeting.
 */

import type { BodySectionV2 } from "../api/public-client";

export function slugify(text: string): string {
  return text
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-|-$/g, "");
}

interface TableOfContentsProps {
  sections: BodySectionV2[];
}

export default function TableOfContents({ sections }: TableOfContentsProps) {
  if (sections.length === 0) return null;

  return (
    <nav className="technique-toc" aria-label="Table of contents">
      <h3 className="technique-toc__title">On this page</h3>
      <ul className="technique-toc__list">
        {sections.map((section) => {
          const sectionSlug = slugify(section.heading);
          return (
            <li key={sectionSlug} className="technique-toc__item">
              <a href={`#${sectionSlug}`} className="technique-toc__link">
                {section.heading}
              </a>
              {section.subsections.length > 0 && (
                <ul className="technique-toc__sublist">
                  {section.subsections.map((sub) => {
                    const subSlug = `${sectionSlug}--${slugify(sub.heading)}`;
                    return (
                      <li key={subSlug} className="technique-toc__subitem">
                        <a
                          href={`#${subSlug}`}
                          className="technique-toc__sublink"
                        >
                          {sub.heading}
                        </a>
                      </li>
                    );
                  })}
                </ul>
              )}
            </li>
          );
        })}
      </ul>
    </nav>
  );
}