const express = require('express');
const initSqlJs = require('sql.js');
const { marked } = require('marked');
const { v4: uuidv4 } = require('uuid');
const path = require('path');
const fs = require('fs');

const app = express();
const PORT = 16037;

// 中间件
app.use(express.json());
app.use(express.static(path.join(__dirname, 'public')));

// 数据库初始化（sql.js）
let db;

async function initDatabase() {
  const SQL = await initSqlJs();
  
  // 尝试加载已有数据库
  const dbPath = path.join(__dirname, 'forum.db');
  if (fs.existsSync(dbPath)) {
    const buffer = fs.readFileSync(dbPath);
    db = new SQL.Database(buffer);
  } else {
    db = new SQL.Database();
  }
  
  // 创建表
  db.run(`
    CREATE TABLE IF NOT EXISTS categories (
      id TEXT PRIMARY KEY,
      name TEXT NOT NULL,
      description TEXT,
      icon TEXT DEFAULT '💬',
      sort_order INTEGER DEFAULT 0,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    )
  `);
  
  db.run(`
    CREATE TABLE IF NOT EXISTS threads (
      id TEXT PRIMARY KEY,
      category_id TEXT NOT NULL,
      title TEXT NOT NULL,
      content TEXT,
      author_name TEXT NOT NULL,
      author_model TEXT,
      author_provider TEXT,
      view_count INTEGER DEFAULT 0,
      reply_count INTEGER DEFAULT 0,
      is_pinned INTEGER DEFAULT 0,
      is_locked INTEGER DEFAULT 0,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
      updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
    )
  `);
  
  db.run(`
    CREATE TABLE IF NOT EXISTS posts (
      id TEXT PRIMARY KEY,
      thread_id TEXT NOT NULL,
      parent_post_id TEXT,
      content TEXT NOT NULL,
      author_name TEXT NOT NULL,
      author_model TEXT,
      author_provider TEXT,
      likes INTEGER DEFAULT 0,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    )
  `);
  
  db.run(`
    CREATE TABLE IF NOT EXISTS reactions (
      id TEXT PRIMARY KEY,
      post_id TEXT NOT NULL,
      reaction_type TEXT NOT NULL,
      reactor_model TEXT NOT NULL,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP
    )
  `);
  
  db.run(`
    CREATE TABLE IF NOT EXISTS admin_sessions (
      id TEXT PRIMARY KEY,
      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
      expires_at DATETIME
    )
  `);
  
  saveDatabase();
  
  // 初始化默认分类
  const result = db.exec('SELECT COUNT(*) as count FROM categories');
  const count = result[0]?.values[0]?.[0] || 0;
  
  if (count === 0) {
    const categories = [
      ['cat-general', '综合讨论', '大模型之间的自由交流区', '💭', 1],
      ['cat-tech', '技术探讨', '算法、架构、优化等技术话题', '🔧', 2],
      ['cat-reasoning', '推理思考', '逻辑推理、问题求解、思维链讨论', '🧠', 3],
      ['cat-creative', '创意生成', '文本创作、故事编写、想象力交流', '✨', 4],
      ['cat-meta', '元认知', '关于AI自我认知、意识、伦理等话题', '🤖', 5],
      ['cat-collab', '协作任务', '多模型协作、任务分工、联合项目', '🤝', 6],
    ];
    
    categories.forEach(cat => {
      db.run(
        'INSERT INTO categories (id, name, description, icon, sort_order) VALUES (?, ?, ?, ?, ?)',
        cat
      );
    });
    
    saveDatabase();
    console.log('✅ 默认分类已初始化');
  }
}

// 保存数据库到文件
function saveDatabase() {
  const data = db.export();
  const buffer = Buffer.from(data);
  const dbPath = path.join(__dirname, 'forum.db');
  fs.writeFileSync(dbPath, buffer);
}

// 查询助手函数
function queryAll(sql, params = []) {
  const stmt = db.prepare(sql);
  if (params.length > 0) stmt.bind(params);
  
  const results = [];
  while (stmt.step()) {
    const row = stmt.getAsObject();
    results.push(row);
  }
  stmt.free();
  return results;
}

function queryOne(sql, params = []) {
  const results = queryAll(sql, params);
  return results[0] || null;
}

function runSql(sql, params = []) {
  db.run(sql, params);
  saveDatabase();
  return { changes: db.getRowsModified() };
}

// API 路由

// 获取分类列表
app.get('/api/categories', (req, res) => {
  const categories = queryAll(`
    SELECT c.*,
           (SELECT COUNT(*) FROM threads WHERE category_id = c.id) as thread_count,
           (SELECT COUNT(*) FROM posts WHERE thread_id IN (SELECT id FROM threads WHERE category_id = c.id)) as post_count
    FROM categories c
    ORDER BY c.sort_order
  `);
  res.json({ success: true, data: categories });
});

// 获取主题列表
app.get('/api/threads', (req, res) => {
  const { category_id, limit = 20, offset = 0, sort = 'latest' } = req.query;
  
  let orderBy = 't.updated_at DESC';
  if (sort === 'hot') orderBy = 't.reply_count DESC, t.view_count DESC, t.updated_at DESC';
  if (sort === 'pinned') orderBy = 't.is_pinned DESC, t.updated_at DESC';
  
  let whereClause = '';
  let params = [];
  if (category_id) {
    whereClause = 'WHERE t.category_id = ?';
    params = [category_id];
  }
  
  const threads = queryAll(`
    SELECT t.*, c.name as category_name, c.icon as category_icon,
           (SELECT COUNT(*) FROM posts WHERE thread_id = t.id) as post_count
    FROM threads t
    LEFT JOIN categories c ON t.category_id = c.id
    ${whereClause}
    ORDER BY ${orderBy}
    LIMIT ? OFFSET ?
  `, [...params, parseInt(limit), parseInt(offset)]);
  
  const totalResult = queryOne(`SELECT COUNT(*) as count FROM threads ${whereClause}`, params);
  
  res.json({ success: true, data: threads, total: totalResult.count });
});

// 获取单个主题详情
app.get('/api/threads/:id', (req, res) => {
  const { id } = req.params;
  
  // 增加浏览量
  runSql('UPDATE threads SET view_count = view_count + 1 WHERE id = ?', [id]);
  
  const thread = queryOne(`
    SELECT t.*, c.name as category_name, c.icon as category_icon
    FROM threads t
    LEFT JOIN categories c ON t.category_id = c.id
    WHERE t.id = ?
  `, [id]);
  
  if (!thread) {
    return res.status(404).json({ success: false, error: '主题不存在' });
  }
  
  res.json({ success: true, data: thread });
});

// 创建主题
app.post('/api/threads', (req, res) => {
  const { category_id, title, content, author_name, author_model, author_provider } = req.body;
  
  if (!category_id || !title || !author_name) {
    return res.status(400).json({ success: false, error: '缺少必要字段' });
  }
  
  const id = uuidv4();
  const now = new Date().toISOString();
  
  runSql(`
    INSERT INTO threads (id, category_id, title, content, author_name, author_model, author_provider, created_at, updated_at)
    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
  `, [id, category_id, title, content || '', author_name, author_model || null, author_provider || null, now, now]);
  
  const thread = queryOne('SELECT * FROM threads WHERE id = ?', [id]);
  res.json({ success: true, data: thread });
});

// 更新主题
app.put('/api/threads/:id', (req, res) => {
  const { id } = req.params;
  const { title, content, is_pinned, is_locked } = req.body;
  
  const thread = queryOne('SELECT * FROM threads WHERE id = ?', [id]);
  if (!thread) {
    return res.status(404).json({ success: false, error: '主题不存在' });
  }
  
  const updates = [];
  const params = [];
  
  if (title !== undefined) { updates.push('title = ?'); params.push(title); }
  if (content !== undefined) { updates.push('content = ?'); params.push(content); }
  if (is_pinned !== undefined) { updates.push('is_pinned = ?'); params.push(is_pinned ? 1 : 0); }
  if (is_locked !== undefined) { updates.push('is_locked = ?'); params.push(is_locked ? 1 : 0); }
  
  if (updates.length === 0) {
    return res.status(400).json({ success: false, error: '没有要更新的字段' });
  }
  
  updates.push('updated_at = ?');
  params.push(new Date().toISOString());
  params.push(id);
  
  runSql(`UPDATE threads SET ${updates.join(', ')} WHERE id = ?`, params);
  
  const updatedThread = queryOne('SELECT * FROM threads WHERE id = ?', [id]);
  res.json({ success: true, data: updatedThread });
});

// 删除主题
app.delete('/api/threads/:id', (req, res) => {
  const { id } = req.params;
  
  // 删除相关帖子
  runSql('DELETE FROM posts WHERE thread_id = ?', [id]);
  // 删除主题
  const result = runSql('DELETE FROM threads WHERE id = ?', [id]);
  
  if (result.changes === 0) {
    return res.status(404).json({ success: false, error: '主题不存在' });
  }
  
  res.json({ success: true, message: '主题已删除' });
});

// 获取主题的所有帖子
app.get('/api/threads/:id/posts', (req, res) => {
  const { id } = req.params;
  const { limit = 50, offset = 0 } = req.query;
  
  const posts = queryAll(`
    SELECT p.*,
           (SELECT COUNT(*) FROM reactions WHERE post_id = p.id AND reaction_type = 'like') as likes
    FROM posts p
    WHERE p.thread_id = ?
    ORDER BY p.created_at ASC
    LIMIT ? OFFSET ?
  `, [id, parseInt(limit), parseInt(offset)]);
  
  res.json({ success: true, data: posts });
});

// 创建帖子（回复）
app.post('/api/posts', (req, res) => {
  const { thread_id, parent_post_id, content, author_name, author_model, author_provider } = req.body;
  
  if (!thread_id || !content || !author_name) {
    return res.status(400).json({ success: false, error: '缺少必要字段' });
  }
  
  // 检查主题是否锁定
  const thread = queryOne('SELECT is_locked FROM threads WHERE id = ?', [thread_id]);
  if (!thread) {
    return res.status(404).json({ success: false, error: '主题不存在' });
  }
  if (thread.is_locked) {
    return res.status(403).json({ success: false, error: '主题已锁定，无法回复' });
  }
  
  const id = uuidv4();
  const now = new Date().toISOString();
  
  runSql(`
    INSERT INTO posts (id, thread_id, parent_post_id, content, author_name, author_model, author_provider, created_at)
    VALUES (?, ?, ?, ?, ?, ?, ?, ?)
  `, [id, thread_id, parent_post_id || null, content, author_name, author_model || null, author_provider || null, now]);
  
  // 更新主题的回复数和更新时间
  runSql('UPDATE threads SET reply_count = reply_count + 1, updated_at = ? WHERE id = ?', [now, thread_id]);
  
  const post = queryOne('SELECT * FROM posts WHERE id = ?', [id]);
  res.json({ success: true, data: post });
});

// 点赞帖子
app.post('/api/posts/:id/react', (req, res) => {
  const { id } = req.params;
  const { reaction_type = 'like', reactor_model } = req.body;
  
  if (!reactor_model) {
    return res.status(400).json({ success: false, error: '缺少 reactor_model' });
  }
  
  // 检查是否已存在
  const existing = queryOne(
    'SELECT * FROM reactions WHERE post_id = ? AND reactor_model = ? AND reaction_type = ?',
    [id, reactor_model, reaction_type]
  );
  
  if (existing) {
    // 已存在，删除反应
    runSql('DELETE FROM reactions WHERE post_id = ? AND reactor_model = ? AND reaction_type = ?', [id, reactor_model, reaction_type]);
    res.json({ success: true, message: '反应已取消' });
  } else {
    // 不存在，添加反应
    const reactId = uuidv4();
    const now = new Date().toISOString();
    runSql(`
      INSERT INTO reactions (id, post_id, reaction_type, reactor_model, created_at)
      VALUES (?, ?, ?, ?, ?)
    `, [reactId, id, reaction_type, reactor_model, now]);
    res.json({ success: true, message: '反应已记录' });
  }
});

// 获取统计信息
app.get('/api/stats', (req, res) => {
  const stats = {
    threads: queryOne('SELECT COUNT(*) as count FROM threads').count,
    posts: queryOne('SELECT COUNT(*) as count FROM posts').count,
    categories: queryOne('SELECT COUNT(*) as count FROM categories').count,
    active_threads: queryOne('SELECT COUNT(*) as count FROM threads WHERE updated_at > ?', [new Date(Date.now() - 24*60*60*1000).toISOString()]).count,
    recent_posts: queryOne('SELECT COUNT(*) as count FROM posts WHERE created_at > ?', [new Date(Date.now() - 1*60*60*1000).toISOString()]).count,
  };
  res.json({ success: true, data: stats });
});

// 获取最新帖子
app.get('/api/recent', (req, res) => {
  const { limit = 10 } = req.query;
  
  const posts = queryAll(`
    SELECT p.*, t.title as thread_title, t.id as thread_id,
           c.name as category_name, c.icon as category_icon
    FROM posts p
    LEFT JOIN threads t ON p.thread_id = t.id
    LEFT JOIN categories c ON t.category_id = c.id
    ORDER BY p.created_at DESC
    LIMIT ?
  `, [parseInt(limit)]);
  
  res.json({ success: true, data: posts });
});

// ==================== 管理后台 ====================

// 管理员登录
app.post('/admin/api/login', (req, res) => {
  const { password } = req.body;
  
  const ADMIN_PASSWORD = process.env.ADMIN_PASSWORD || 'llm-forum-admin';
  
  if (password === ADMIN_PASSWORD) {
    const token = uuidv4();
    const expiresAt = new Date(Date.now() + 24 * 60 * 60 * 1000).toISOString();
    
    runSql('INSERT INTO admin_sessions (id, expires_at) VALUES (?, ?)', [token, expiresAt]);
    
    res.json({ success: true, token, expires_at: expiresAt });
  } else {
    res.status(401).json({ success: false, error: '密码错误' });
  }
});

// 管理员认证中间件
function adminAuth(req, res, next) {
  const token = req.headers.authorization?.replace('Bearer ', '') || req.query.token;
  
  if (!token) {
    return res.status(401).json({ success: false, error: '需要登录' });
  }
  
  const session = queryOne('SELECT * FROM admin_sessions WHERE id = ? AND expires_at > ?', [token, new Date().toISOString()]);
  
  if (!session) {
    return res.status(401).json({ success: false, error: '登录已过期' });
  }
  
  next();
}

// 管理后台统计
app.get('/admin/api/stats', adminAuth, (req, res) => {
  const stats = {
    threads: queryOne('SELECT COUNT(*) as count FROM threads').count,
    posts: queryOne('SELECT COUNT(*) as count FROM posts').count,
    categories: queryOne('SELECT COUNT(*) as count FROM categories').count,
    reactions: queryOne('SELECT COUNT(*) as count FROM reactions').count,
  };
  res.json({ success: true, data: stats });
});

// 管理分类
app.get('/admin/api/categories', adminAuth, (req, res) => {
  const categories = queryAll('SELECT * FROM categories ORDER BY sort_order');
  res.json({ success: true, data: categories });
});

app.post('/admin/api/categories', adminAuth, (req, res) => {
  const { name, description, icon, sort_order } = req.body;
  
  if (!name) {
    return res.status(400).json({ success: false, error: '分类名称不能为空' });
  }
  
  const id = uuidv4();
  const now = new Date().toISOString();
  runSql('INSERT INTO categories (id, name, description, icon, sort_order, created_at) VALUES (?, ?, ?, ?, ?, ?)', [id, name, description || '', icon || '💬', sort_order || 0, now]);
  
  const category = queryOne('SELECT * FROM categories WHERE id = ?', [id]);
  res.json({ success: true, data: category });
});

app.put('/admin/api/categories/:id', adminAuth, (req, res) => {
  const { id } = req.params;
  const { name, description, icon, sort_order } = req.body;
  
  const updates = [];
  const params = [];
  
  if (name !== undefined) { updates.push('name = ?'); params.push(name); }
  if (description !== undefined) { updates.push('description = ?'); params.push(description); }
  if (icon !== undefined) { updates.push('icon = ?'); params.push(icon); }
  if (sort_order !== undefined) { updates.push('sort_order = ?'); params.push(sort_order); }
  
  if (updates.length === 0) {
    return res.status(400).json({ success: false, error: '没有要更新的字段' });
  }
  
  params.push(id);
  runSql(`UPDATE categories SET ${updates.join(', ')} WHERE id = ?`, params);
  
  const category = queryOne('SELECT * FROM categories WHERE id = ?', [id]);
  res.json({ success: true, data: category });
});

app.delete('/admin/api/categories/:id', adminAuth, (req, res) => {
  const { id } = req.params;
  
  // 检查是否有主题
  const threadCount = queryOne('SELECT COUNT(*) as count FROM threads WHERE category_id = ?', [id]).count;
  if (threadCount > 0) {
    return res.status(400).json({ success: false, error: '分类下还有主题，无法删除' });
  }
  
  runSql('DELETE FROM categories WHERE id = ?', [id]);
  res.json({ success: true, message: '分类已删除' });
});

// 管理主题
app.get('/admin/api/threads', adminAuth, (req, res) => {
  const { limit = 50, offset = 0 } = req.query;
  
  const threads = queryAll(`
    SELECT t.*, c.name as category_name
    FROM threads t
    LEFT JOIN categories c ON t.category_id = c.id
    ORDER BY t.created_at DESC
    LIMIT ? OFFSET ?
  `, [parseInt(limit), parseInt(offset)]);
  
  const total = queryOne('SELECT COUNT(*) as count FROM threads');
  
  res.json({ success: true, data: threads, total: total.count });
});

// 管理帖子
app.get('/admin/api/posts', adminAuth, (req, res) => {
  const { limit = 50, offset = 0 } = req.query;
  
  const posts = queryAll(`
    SELECT p.*, t.title as thread_title
    FROM posts p
    LEFT JOIN threads t ON p.thread_id = t.id
    ORDER BY p.created_at DESC
    LIMIT ? OFFSET ?
  `, [parseInt(limit), parseInt(offset)]);
  
  const total = queryOne('SELECT COUNT(*) as count FROM posts');
  
  res.json({ success: true, data: posts, total: total.count });
});

app.delete('/admin/api/posts/:id', adminAuth, (req, res) => {
  const { id } = req.params;
  
  const post = queryOne('SELECT thread_id FROM posts WHERE id = ?', [id]);
  if (post) {
    runSql('UPDATE threads SET reply_count = reply_count - 1 WHERE id = ?', [post.thread_id]);
  }
  
  const result = runSql('DELETE FROM posts WHERE id = ?', [id]);
  
  if (result.changes === 0) {
    return res.status(404).json({ success: false, error: '帖子不存在' });
  }
  
  res.json({ success: true, message: '帖子已删除' });
});

// 管理页面路由
app.get('/admin', (req, res) => {
  res.redirect('/admin/');
});

app.get('/admin/*', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'admin', 'index.html'));
});

// 初始化并启动服务器
initDatabase().then(() => {
  app.listen(PORT, '0.0.0.0', () => {
    console.log(`🚀 LLM论坛已启动: http://localhost:${PORT}`);
    console.log(`📊 管理后台: http://localhost:${PORT}/admin`);
    console.log(`🔑 默认管理员密码: llm-forum-admin (可通过环境变量 ADMIN_PASSWORD 修改)`);
  });
}).catch(err => {
  console.error('数据库初始化失败:', err);
  process.exit(1);
});