const http = require('http');
const https = require('https');
const fs = require('fs');
const path = require('path');

const MAX_BODY_SIZE = 10 * 1024 * 1024; // 10MB

// 读取配置文件
function loadConfig() {
  const configPath = path.join(__dirname, 'config.json');
  if (!fs.existsSync(configPath)) {
    console.error('❌ 未找到 config.json，请创建配置文件');
    process.exit(1);
  }
  const config = JSON.parse(fs.readFileSync(configPath, 'utf-8'));
  const apiKey = config.api_key;
  if (!apiKey || apiKey === 'sk-你的API密钥') {
    console.warn('⚠️  请在 config.json 中配置真实的 API Key（当前为占位值）');
    console.warn('⚠️  API 请求将会失败，但界面可以正常访问\n');
  }
  return { apiKey: apiKey || '', baseUrl: config.base_url || 'https://yibuapi.com/v1' };
}

const CONFIG = loadConfig();
console.log(`✅ API Key 已加载: ${CONFIG.apiKey.slice(0, 8)}...`);
console.log(`🌐 API Base URL: ${CONFIG.baseUrl}`);

// MIME 类型映射
const MIME_TYPES = {
  '.html': 'text/html; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'application/javascript; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.png': 'image/png',
  '.svg': 'image/svg+xml',
  '.ico': 'image/x-icon',
};

const PORT = 8080;
const TARGET_URL = new URL(CONFIG.baseUrl);

// 读取请求体，带大小限制
function readBody(req, limit, callback) {
  const chunks = [];
  let size = 0;
  req.on('data', chunk => {
    size += chunk.length;
    if (size > limit) {
      req.destroy();
      return callback(new Error('请求体超过大小限制'));
    }
    chunks.push(chunk);
  });
  req.on('end', () => callback(null, Buffer.concat(chunks)));
  req.on('error', err => callback(err));
}

// 代理 API 请求
function proxyRequest(req, res) {
  readBody(req, MAX_BODY_SIZE, (err, body) => {
    if (err) {
      res.writeHead(413, { 'Content-Type': 'application/json; charset=utf-8' });
      return res.end(JSON.stringify({ error: { message: err.message } }));
    }

    const options = {
      hostname: TARGET_URL.hostname,
      port: TARGET_URL.port || 443,
      path: req.url,
      method: req.method,
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${CONFIG.apiKey}`,
        'Content-Length': Buffer.byteLength(body),
      },
    };

    const proxyReq = https.request(options, proxyRes => {
      res.writeHead(proxyRes.statusCode, proxyRes.headers);
      proxyRes.pipe(res);

      proxyRes.on('error', err => {
        console.error('[代理] 响应流错误:', err.message);
        if (!res.writableEnded) res.end();
      });
    });

    proxyReq.on('error', err => {
      console.error('[代理] 请求失败:', err.message);
      if (!res.headersSent) {
        res.writeHead(502, { 'Content-Type': 'application/json; charset=utf-8' });
      }
      res.end(JSON.stringify({ error: { message: `API 请求失败: ${err.message}` } }));
    });

    proxyReq.setTimeout(180000, () => {
      proxyReq.destroy();
      if (!res.headersSent) {
        res.writeHead(504, { 'Content-Type': 'application/json; charset=utf-8' });
      }
      res.end(JSON.stringify({ error: { message: '请求超时，请重试' } }));
    });

    res.on('close', () => {
      if (!proxyReq.destroyed) proxyReq.destroy();
    });

    proxyReq.write(body);
    proxyReq.end();
  });
}

// 对话数据存储
const DATA_DIR = path.join(__dirname, 'data');
const CONV_FILE = path.join(DATA_DIR, 'conversations.json');
const CONV_TMP = CONV_FILE + '.tmp';

function loadConversations() {
  try {
    if (fs.existsSync(CONV_FILE)) {
      return JSON.parse(fs.readFileSync(CONV_FILE, 'utf-8'));
    }
  } catch(e) { console.error('读取对话数据失败:', e.message); }
  return [];
}

// 原子写：先写 .tmp 再 rename，避免写盘崩溃导致文件损坏
function saveConversations(data) {
  if (!fs.existsSync(DATA_DIR)) fs.mkdirSync(DATA_DIR, { recursive: true });
  fs.writeFileSync(CONV_TMP, JSON.stringify(data), 'utf-8');
  fs.renameSync(CONV_TMP, CONV_FILE);
}

// 静态文件服务
function serveStatic(req, res) {
  let filePath = req.url === '/' ? '/index.html' : req.url;
  filePath = path.join(__dirname, filePath);

  // 安全检查：防止目录遍历（__dirname 追加 path.sep 避免前缀匹配绕过）
  const root = __dirname + path.sep;
  if (!path.resolve(filePath).startsWith(root)) {
    res.writeHead(403);
    res.end('403 Forbidden');
    return;
  }

  const ext = path.extname(filePath);
  const contentType = MIME_TYPES[ext] || 'application/octet-stream';

  fs.readFile(filePath, (err, data) => {
    if (err) {
      if (err.code === 'ENOENT') {
        res.writeHead(404);
        res.end('404 Not Found');
      } else {
        res.writeHead(500);
        res.end('500 Internal Server Error');
      }
      return;
    }
    res.writeHead(200, { 'Content-Type': contentType });
    res.end(data);
  });
}

// 创建服务器
const server = http.createServer((req, res) => {
  // 使用 WHATWG URL API（url.parse 在 Node 24 已弃用）
  const parsed = new URL(req.url, 'http://localhost');

  // API 代理
  if (parsed.pathname.startsWith('/v1/')) {
    return proxyRequest(req, res);
  }

  // 对话数据接口
  if (parsed.pathname === '/api/conversations') {
    if (req.method === 'GET') {
      const data = loadConversations();
      res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8' });
      return res.end(JSON.stringify(data));
    }
    if (req.method === 'POST') {
      readBody(req, MAX_BODY_SIZE, (err, raw) => {
        if (err) {
          res.writeHead(413, { 'Content-Type': 'application/json; charset=utf-8' });
          return res.end(JSON.stringify({ ok: false, error: err.message }));
        }
        try {
          const data = JSON.parse(raw.toString());
          saveConversations(data);
          res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8' });
          res.end(JSON.stringify({ ok: true }));
        } catch(e) {
          res.writeHead(400, { 'Content-Type': 'application/json; charset=utf-8' });
          res.end(JSON.stringify({ ok: false, error: e.message }));
        }
      });
      return;
    }
  }

  // 静态文件
  serveStatic(req, res);
});

server.listen(PORT, () => {
  const convs = loadConversations();
  console.log(`💬 已加载 ${convs.length} 个对话`);
  console.log(`🚀 聊天工具已启动: http://localhost:${PORT}`);
  console.log('📋 按 Ctrl+C 停止服务\n');
});