'use client';

import { useState, useEffect } from 'react';

interface TableOfContentsProps {
  className?: string;
}

interface Section {
  id: string;
  title: string;
  level: number;
}

export function TableOfContents({ className = '' }: TableOfContentsProps) {
  const [activeSection, setActiveSection] = useState<string>('');
  const [sections, setSections] = useState<Section[]>([]);

  useEffect(() => {
    const extractSections = () => {
      const sectionsWithId = document.querySelectorAll('section[id]');
      const extractedSections: Section[] = Array.from(sectionsWithId).map((section) => {
        const h2 = section.querySelector('h2');
        return {
          id: section.id,
          title: h2?.textContent || section.id,
          level: 2
        };
      });
      
      setSections(extractedSections);
      return sectionsWithId;
    };

    // Fonction pour configurer l'intersection observer
    const setupIntersectionObserver = (sections: NodeListOf<Element>) => {
      const intersectionObserver = new IntersectionObserver(
        (entries) => {
          entries.forEach((entry) => {
            if (entry.isIntersecting) {
              setActiveSection(entry.target.id);
            }
          });
        },
        {
          rootMargin: '-20% 0px -70% 0px',
          threshold: 0
        }
      );

      sections.forEach((section) => intersectionObserver.observe(section));
      return intersectionObserver;
    };

    // Essayer immédiatement
    let sectionsElements = extractSections();
    let intersectionObserver: IntersectionObserver | null = null;

    if (sectionsElements.length > 0) {
      intersectionObserver = setupIntersectionObserver(sectionsElements);
    } else {
      // Utiliser MutationObserver pour surveiller les changements
      const mutationObserver = new MutationObserver((mutations) => {
        let shouldCheck = false;
        
        mutations.forEach((mutation) => {
          if (mutation.type === 'childList') {
            // Vérifier si des sections ont été ajoutées
            mutation.addedNodes.forEach((node) => {
              if (node.nodeType === Node.ELEMENT_NODE) {
                const element = node as Element;
                if (element.tagName === 'SECTION' || element.querySelector('section[id]')) {
                  shouldCheck = true;
                }
              }
            });
          }
        });

        if (shouldCheck) {
          sectionsElements = extractSections();
          if (sectionsElements.length > 0 && !intersectionObserver) {
            intersectionObserver = setupIntersectionObserver(sectionsElements);
            mutationObserver.disconnect();
          }
        }
      });

      // Surveiller le contenu principal
      const mainContent = document.querySelector('.lg\\:col-span-3') || document.body;
      mutationObserver.observe(mainContent, {
        childList: true,
        subtree: true
      });

      // Fallback avec des tentatives périodiques
      const intervalId = setInterval(() => {
        sectionsElements = extractSections();
        if (sectionsElements.length > 0) {
          if (!intersectionObserver) {
            intersectionObserver = setupIntersectionObserver(sectionsElements);
          }
          mutationObserver.disconnect();
          clearInterval(intervalId);
        }
      }, 1000);

      return () => {
        mutationObserver.disconnect();
        clearInterval(intervalId);
        if (intersectionObserver) {
          sectionsElements.forEach((section) => intersectionObserver!.unobserve(section));
        }
      };
    }

    return () => {
      if (intersectionObserver) {
        sectionsElements.forEach((section) => intersectionObserver!.unobserve(section));
      }
    };
  }, []);

  const scrollToSection = (sectionId: string) => {
    const element = document.getElementById(sectionId);
    if (element) {
      element.scrollIntoView({
        behavior: 'smooth',
        block: 'start'
      });
    }
  };

  return (
    <nav className={`sticky top-8 ${className}`}>
      <div className="bg-[var(--card)] border border-[var(--border)] rounded-lg p-4 shadow-sm">
        <h3 className="text-sm font-semibold text-[var(--foreground)] mb-3 flex items-center gap-2">
          <span className="text-[var(--primary)]">📋</span>
          Navigation
        </h3>
        
        {sections.length === 0 ? (
          <div className="text-sm text-[var(--muted-foreground)] py-2">
            Chargement des sections...
          </div>
        ) : (
          <>
            <ul className="space-y-1">
              {sections.map((section) => (
                <li key={section.id}>
                  <button
                    onClick={() => scrollToSection(section.id)}
                    className={`w-full text-left px-2 py-1 rounded text-sm transition-colors ${
                      activeSection === section.id
                        ? 'bg-[var(--primary)] text-[var(--primary-foreground)] font-medium'
                        : 'text-[var(--muted-foreground)] hover:text-[var(--foreground)] hover:bg-[var(--card-hover)]'
                    }`}
                  >
                    {section.title}
                  </button>
                </li>
              ))}
            </ul>
            
            {/* Indicateur de progression */}
            <div className="mt-4 pt-3 border-t border-[var(--border)]">
              <div className="flex items-center justify-between text-xs text-[var(--muted-foreground)]">
                <span>Sections</span>
                <span>{sections.length}</span>
              </div>
            </div>
          </>
        )}
      </div>
    </nav>
  );
}
