var express = require('express');
var cors = require('cors');
var http = require('http');
var os = require('os');

var app = express();
var PORT = process.env.PORT || 3000;

// 启用 CORS
app.use(cors());
app.use(express.json());

/**
 * 获取真实客户端 IP（跨平台兼容）
 */
function getClientIP(req) {
  var headers = req.headers;
  
  // 优先级：X-Forwarded-For > X-Real-IP > 直连 IP
  var forwarded = headers['x-forwarded-for'];
  if (forwarded) {
    var ips = forwarded.split(',');
    return ips[0].trim();
  }
  
  var realIP = headers['x-real-ip'];
  if (realIP) {
    return realIP.trim();
  }
  
  var remoteAddr = req.socket.remoteAddress || 
                   req.connection.remoteAddress ||
                   req.ip;
  
  // IPv6 转 IPv4（兼容 Windows/Linux）
  if (remoteAddr && remoteAddr.indexOf('::ffff:') === 0) {
    return remoteAddr.substring(7);
  }
  
  return remoteAddr || 'unknown';
}

/**
 * 只返回 IP（最高效）
 */
app.get('/api/get-ip', function(req, res) {
  var ip = getClientIP(req);
  res.json({ 
    ip: ip, 
    timestamp: new Date().getTime(),
    server: os.platform()
  });
});

/**
 * 返回 IP + 地理位置（带缓存）
 */
var ipCache = {};
var CACHE_TTL = 10 * 60 * 1000; // 10 分钟

app.get('/api/get-ip-info', function(req, res) {
  var ip = getClientIP(req);
  var now = new Date().getTime();
  
  // 检查缓存
  var cached = ipCache[ip];
  if (cached && (now - cached.timestamp) < CACHE_TTL) {
    var result = JSON.parse(JSON.stringify(cached.data)); // 深拷贝
    result.fromCache = true;
    return res.json(result);
  }
  
  // 使用原生 http 模块请求（无需额外依赖）
  var options = {
    hostname: 'ip-api.com',
    port: 80,
    path: '/json/' + encodeURIComponent(ip) + '?lang=zh-CN',
    method: 'GET',
    timeout: 5000
  };
  
  var request = http.request(options, function(response) {
    var chunks = [];
    
    response.on('data', function(chunk) {
      chunks.push(chunk);
    });
    
    response.on('end', function() {
      var body = Buffer.concat(chunks).toString();
      
      try {
        var data = JSON.parse(body);
        
        var result = {
          ip: ip,
          country: data.country || '',
          region: data.regionName || '',
          city: data.city || '',
          isp: data.isp || '',
          timezone: data.timezone || '',
          query_time: now,
          fromCache: false
        };
        
        // 写入缓存
        ipCache[ip] = {
          data: result,
          timestamp: now
        };
        
        // 清理过期缓存（防止内存泄漏）
        cleanupCache();
        
        res.json(result);
      } catch (e) {
        res.json({ ip: ip, error: 'Parse failed', fromCache: false });
      }
    });
  });
  
  request.on('error', function(e) {
    res.json({ ip: ip, error: e.message, fromCache: false });
  });
  
  request.on('timeout', function() {
    request.destroy();
    res.json({ ip: ip, error: 'Request timeout', fromCache: false });
  });
  
  request.end();
});

/**
 * 清理过期缓存
 */
function cleanupCache() {
  var now = new Date().getTime();
  var keys = Object.keys(ipCache);
  
  for (var i = 0; i < keys.length; i++) {
    var key = keys[i];
    if ((now - ipCache[key].timestamp) > CACHE_TTL * 2) {
      delete ipCache[key];
    }
  }
}

/**
 * 健康检查
 */
app.get('/health', function(req, res) {
  res.json({ 
    status: 'ok', 
    uptime: process.uptime(),
    platform: os.platform(),
    memory: process.memoryUsage()
  });
});

// 启动服务器
var server = app.listen(PORT, function() {
  console.log('🚀 Server running on port ' + PORT);
  console.log('   Platform: ' + os.platform());
  console.log('   Test: http://localhost:' + PORT + '/api/get-ip');
});

// 优雅关闭（兼容 Windows/Linux）
process.on('SIGTERM', function() {
  console.log('SIGTERM received, shutting down...');
  server.close(function() {
    process.exit(0);
  });
});

process.on('SIGINT', function() {
  console.log('SIGINT received, shutting down...');
  server.close(function() {
    process.exit(0);
  });
});