const express = require('express');
const router = express.Router();
const contentService = require('../services/content');
const commentService = require('../services/comments');

function renderPost(req, res, next, slug, lang) {
  const post = contentService.getPost(slug, lang);
  if (!post) {
    return next(); // Fall through to standalone pages or 404
  }

  const { prev, next: nextPost } = contentService.getAdjacentPosts(slug);
  const comments = commentService.getCommentsForPost(slug);

  // Set SEO metadata for post
  res.locals.seo = {
    title: `${post.title} - ${res.locals.site.title}`,
    description: post.excerpt || res.locals.site.tagline,
    canonicalUrl: `${res.locals.site.url}/${post.slug}${post.isDefault ? '' : `/${post.lang}`}`,
    ogImage: post.cover ? (post.cover.startsWith('http') ? post.cover : `${res.locals.site.url}${post.cover}`) : res.locals.seo.ogImage,
    type: 'article',
    publishedTime: post.date.toISOString(),
    author: post.author
  };

  res.render('pages/post', {
    title: post.title,
    post,
    currentLang: lang || post.lang,
    comments,
    commentStatus: req.query.comment_status,
    prevPost: prev,
    nextPost
  });
}

// Route for bilingual variant: /<post-slug>/<lang> (e.g. /my-post/zh)
router.get('/:slug/:lang([a-zA-Z]{2,5})', (req, res, next) => {
  const post = contentService.getPost(req.params.slug);
  if (post && post.defaultLang === req.params.lang) {
    return res.redirect(301, `/${req.params.slug}`);
  }
  renderPost(req, res, next, req.params.slug, req.params.lang);
});

// Legacy redirects for multilingual posts
router.get('/ai-can-change-coding-for-kids-en', (req, res) => {
  res.redirect(301, '/ai-can-change-coding-for-kids');
});

// Route for default language: /<post-slug>
router.get('/:slug', (req, res, next) => {
  // Exclude reserved top-level prefixes if any
  const reserved = ['blogs', 'category', 'tag', 'tags', 'search', 'quick-links', 'feed', 'rss.xml', 'sitemap.xml', 'robots.txt', 'api', 'plugins', 'public', 'posts-assets', 'guanli', 'admin'];
  if (reserved.includes(req.params.slug)) {
    return next();
  }
  renderPost(req, res, next, req.params.slug, null);
});

module.exports = router;