const express = require('express');
const db = require('../db');

const router = express.Router();

// XML 转义：& < > " '
function escapeXml(s) {
  return String(s)
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&apos;');
}

// created_at（'YYYY-MM-DD HH:MM:SS'，UTC）转 RFC822 格式（'ddd, DD MMM YYYY HH:MM:SS GMT'）
function toRfc822(createdAt) {
  try {
    const d = new Date(String(createdAt).replace(' ', 'T') + 'Z');
    return isNaN(d.getTime()) ? String(createdAt) : d.toUTCString();
  } catch {
    return String(createdAt);
  }
}

// 摘要：剥 markdown/自定义标签符号，截断 ~maxLen 字
// 处理 [image:]/[file:] 标签、代码块/行内代码、链接（留文字）、标题#、强调*/_/~、引用>、列表符号
function makeSummary(content, maxLen = 200) {
  let s = String(content || '')
    .replace(/\[image:[^\]]*\]/g, ' ')
    .replace(/\[file:[^\]]*\]/g, ' ')
    .replace(/```[\s\S]*?```/g, ' ')
    .replace(/`([^`]*)`/g, '$1')
    .replace(/!\[[^\]]*\]\([^)]*\)/g, ' ')
    .replace(/\[([^\]]+)\]\([^)]*\)/g, '$1')
    .replace(/^#{1,6}\s*/gm, '')
    .replace(/[*_~]{1,3}/g, '')
    .replace(/^\s*>\s?/gm, '')
    .replace(/^\s*[-+*]\s+/gm, '')
    .replace(/\s+/g, ' ')
    .trim();
  if (s.length > maxLen) s = s.slice(0, maxLen) + '…';
  return s;
}

// RSS 2.0 生成器（博客/论坛全站/版块三源共用）
// items = [{ title, link, description, author?, pubDate }]
function renderRss({ title, description, link, items }) {
  let itemsXml = '';
  items.forEach(it => {
    const descCdata = String(it.description || '').replace(/\]\]>/g, ']]]]><![CDATA[>');
    const authorXml = it.author
      ? `      <dc:creator><![CDATA[${String(it.author).replace(/\]\]>/g, ']]]]><![CDATA[>')}]]></dc:creator>\n`
      : '';
    itemsXml += `    <item>
      <title>${escapeXml(it.title)}</title>
      <link>${escapeXml(it.link)}</link>
      <guid>${escapeXml(it.link)}</guid>
      <pubDate>${escapeXml(toRfc822(it.pubDate))}</pubDate>
${authorXml}      <description><![CDATA[${descCdata}]]></description>
    </item>
`;
  });
  return `<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/">
  <channel>
    <title>${escapeXml(title)}</title>
    <link>${escapeXml(link)}</link>
    <description>${escapeXml(description)}</description>
${itemsXml}  </channel>
</rss>
`;
}

function sendFeed(res, xml) {
  // feed 要新鲜：禁缓存（RSS 阅读器拉取频繁，旧缓存会推迟新帖出现）
  res.header('Content-Type', 'application/rss+xml; charset=utf-8');
  res.header('Cache-Control', 'no-cache');
  res.send(xml);
}

// 论坛源对外条件：全站开关 feed_forum_enabled='1' 且论坛游客可见（私密模式不对外订阅）
function forumFeedEnabled() {
  return db.getSetting('feed_forum_enabled') === '1' && db.getSetting('forum_guest_visible') === '1';
}

// 论坛帖子 → feed item（摘要剥离 markdown）
function forumItem(p, base) {
  return {
    title: p.title,
    link: base + '/forum/' + p.id,
    description: makeSummary(p.content),
    author: p.username || '匿名',
    pubDate: p.created_at
  };
}

function siteBase(req) {
  const siteUrl = db.getSetting('site_url') || (req.protocol + '://' + req.get('host'));
  return siteUrl.replace(/\/$/, '');
}

function feedMaxItems() {
  return Math.min(Math.max(parseInt(db.getSetting('feed_max_items')) || 20, 1), 100);
}

// ── 博客全站源（原有 /feed.xml 保留，内容受 feed_show_full / feed_max_items 控制）────────
router.get('/feed.xml', (req, res) => {
  const siteName = db.getSetting('site_name') || 'RainWeb';
  const siteDesc = db.getSetting('site_description') || '个人云平台';
  const base = siteBase(req);
  const maxItems = feedMaxItems();
  const showFull = db.getSetting('feed_show_full') === '1';
  const posts = db.all(
    'SELECT id, title, excerpt, content, created_at FROM blog_posts WHERE published = 1 ORDER BY created_at DESC LIMIT ?', [maxItems]);
  const items = posts.map(p => ({
    title: p.title,
    link: base + '/blog/' + p.id,
    // 全文模式用 content；摘要模式优先 excerpt，无 excerpt 则剥 markdown 取前 200 字
    description: showFull ? (p.content || '') : (p.excerpt || makeSummary(p.content)),
    pubDate: p.created_at
  }));
  sendFeed(res, renderRss({ title: siteName, description: siteDesc, link: base, items }));
});

// ── 论坛全站源 ──────────────────────────────────
router.get('/feed/forum.xml', (req, res) => {
  if (!forumFeedEnabled()) return res.status(404).send('Not found');
  const siteName = db.getSetting('site_name') || 'RainWeb';
  const siteDesc = db.getSetting('site_description') || '个人云平台';
  const base = siteBase(req);
  const maxItems = feedMaxItems();
  const posts = db.all(
    `SELECT fp.*, u.username FROM forum_posts fp JOIN users u ON fp.author_id = u.id
     ORDER BY fp.created_at DESC LIMIT ?`, [maxItems]);
  sendFeed(res, renderRss({
    title: siteName + ' 论坛',
    description: siteDesc + ' —— 论坛最新帖子',
    link: base + '/forum.html',
    items: posts.map(p => forumItem(p, base))
  }));
});

// ── 版块源 ─────────────────────────────────────
router.get('/feed/forum/c/:id.xml', (req, res) => {
  if (!forumFeedEnabled()) return res.status(404).send('Not found');
  const cat = db.get('SELECT id, name, feed_enabled FROM forum_categories WHERE id = ?', [req.params.id]);
  // 版块不存在或该版块 feed 已关闭 → 404
  if (!cat || !cat.feed_enabled) return res.status(404).send('Not found');
  const siteName = db.getSetting('site_name') || 'RainWeb';
  const base = siteBase(req);
  const maxItems = feedMaxItems();
  const posts = db.all(
    `SELECT fp.*, u.username FROM forum_posts fp JOIN users u ON fp.author_id = u.id
     WHERE fp.category_id = ? ORDER BY fp.created_at DESC LIMIT ?`, [cat.id, maxItems]);
  sendFeed(res, renderRss({
    title: cat.name + ' - ' + siteName,
    description: cat.name + ' 版块最新帖子',
    link: base + '/forum/c/' + cat.id,
    items: posts.map(p => forumItem(p, base))
  }));
});

module.exports = router;