'use client';

import { useEffect, useState } from 'react';
import { format } from 'date-fns';
import Link from 'next/link';

interface Post {
  slug: string;
  title: string;
  date: string;
  tags: string[];
  summary: string;
  content: string;
  createdAt: string;
}

export default function PostPage({ params }: { params: { slug: string[] } }) {
  const [post, setPost] = useState<Post | null>(null);

  // Join the slug array to get the full path
  const slugPath = Array.isArray(params.slug) ? params.slug.join('/') : params.slug;

  useEffect(() => {
    // Initial load
    loadPost();

    // Set up polling for changes
    const interval = setInterval(loadPost, 2000);

    // Cleanup
    return () => clearInterval(interval);
  }, [slugPath]);

  // On post load or update, scroll to anchor in hash if present
  useEffect(() => {
    // Scroll to anchor if hash is present
    const scrollToHash = () => {
      if (window.location.hash) {
        const id = window.location.hash.substring(1);
        const el = document.getElementById(id);
        if (el) {
          el.scrollIntoView({ behavior: 'smooth', block: 'start' });
        }
      }
    };
    // On initial load
    scrollToHash();
    // Listen for hash changes
    window.addEventListener('hashchange', scrollToHash);
    return () => {
      window.removeEventListener('hashchange', scrollToHash);
    };
  }, [post]);

  // Intercept anchor clicks in rendered markdown to ensure smooth scrolling to headings
  useEffect(() => {
    // Find the rendered markdown container
    const prose = document.querySelector('.prose');
    if (!prose) return;
    /**
     * Handles clicks on anchor links (e.g. Table of Contents links) inside the markdown.
     * - If the link is an in-page anchor (starts with #), prevent default navigation.
     * - Try to find an element with the corresponding id and scroll to it.
     * - If not found, search all headings for one whose text matches the anchor (case-insensitive, ignoring spaces/punctuation).
     * - If a match is found, scroll to that heading.
     * - Update the URL hash without reloading the page.
     */
    const handleClick = (e: Event) => {
      if (!(e instanceof MouseEvent)) return;
      let target = e.target as HTMLElement | null;
      // Traverse up to find the closest anchor tag
      while (target && target.tagName !== 'A') {
        target = target.parentElement;
      }
      if (target && target.tagName === 'A' && target.getAttribute('href')?.startsWith('#')) {
        e.preventDefault();
        const id = target.getAttribute('href')!.slice(1);
        let el = document.getElementById(id);
        if (!el) {
          // Try to find a heading whose text matches the id (case-insensitive, ignoring spaces/punctuation)
          const headings = prose.querySelectorAll('h1, h2, h3, h4, h5, h6');
          const normalize = (str: string) => str.toLowerCase().replace(/[^a-z0-9]+/g, '');
          const normId = normalize(id);
          const found = Array.from(headings).find(h => normalize(h.textContent || '') === normId);
          el = (found as HTMLElement) || null;
        }
        if (el) {
          el.scrollIntoView({ behavior: 'smooth', block: 'start' });
          history.replaceState(null, '', `#${id}`);
        }
      }
    };
    prose.addEventListener('click', handleClick);
    return () => {
      prose.removeEventListener('click', handleClick);
    };
  }, [post]);

  const loadPost = async () => {
    try {
      const response = await fetch(`/api/posts/${encodeURIComponent(slugPath)}`);
      const data = await response.json();
      setPost(data);
    } catch (error) {
      console.error('Fehler beim Laden des Beitrags:', error);
    }
  };

  if (!post) {
    return <div>Lädt...</div>;
  }

  return (
    <article className="min-h-screen p-8 max-w-4xl mx-auto">
      <Link href="/" className="text-blue-600 hover:underline mb-8 inline-block">
        ← Zurück zu den Beiträgen
      </Link>
      
      <h1 className="text-4xl font-bold mb-4">{post.title}</h1>
      <div className="text-gray-600 mb-8">
        {post.date ? (
          <div>Veröffentlicht: {format(new Date(post.date), 'd. MMMM yyyy')}</div>
        ) : (
          <div className="flex flex-col items-center">
            <div className="flex">
              <span className="text-2xl animate-spin mr-2">⚙️</span>
              <span className="text-2xl animate-spin-reverse">⚙️</span>
            </div>
            <div className="text-xl font-bold mt-2">In Bearbeitung</div>
          </div>
        )}
        <div>Erstellt: {format(new Date(post.createdAt), 'd. MMMM yyyy HH:mm')}</div>
      </div>
      
      <div className="flex gap-2 mb-8">
        {post.tags.map((tag) => (
          <span
            key={tag}
            className="bg-gray-100 text-gray-800 px-3 py-1 rounded-full text-sm"
          >
            {tag}
          </span>
        ))}
      </div>

      <div
        className="prose prose-lg max-w-none"
        dangerouslySetInnerHTML={{ __html: post.content }}
      />
    </article>
  );
}