class ApiGateway {
      private $routes = [
          '/user/*' => ['host' => ['http://user-service-1', 'http://user-service-2']],
          '/order/*' => ['host' => ['http://order-service-1', 'http://order-service-2']],
          '/product/*' => ['host' => ['http://product-service']],
      ];

      // 路由转发 + 负载均衡(轮询)
      function route($path) {
          foreach ($this->routes as $pattern => $config) {
              if (fnmatch($pattern, $path)) {
                  $hosts = $config['host'];
                  $index = crc32($path) % count($hosts); // 简单轮询
                  return $hosts[$index];
              }
          }
          throw new Exception("Route not found");
      }

      // 请求处理
      function handle($method, $path, $body = null) {
          // 1. 认证
          if (!$this->authenticate()) {
              return ['code' => 401, 'msg' => 'Unauthorized'];
          }

          // 2. 限流
          if (!$this->rateLimit($path)) {
              return ['code' => 429, 'msg' => 'Too Many Requests'];
          }

          // 3. 路由到微服务
          $service_url = $this->route($path);

          // 4. 转发请求
          $ch = curl_init("$service_url$path");
          curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $method);
          curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
          curl_setopt($ch, CURLOPT_TIMEOUT, 3); // 超时3s
          if ($body) curl_setopt($ch, CURLOPT_POSTFIELDS, $body);

          $response = curl_exec($ch);
          $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
          curl_close($ch);

          return ['code' => $http_code, 'data' => $response];
      }

      // 简单限流(令牌桶)
      private $tokens = [];
      function rateLimit($path, $limit = 100) {
          $key = md5($path);
          $now = time();

          if (!isset($this->tokens[$key])) {
              $this->tokens[$key] = ['count' => $limit, 'time' => $now];
          }

          // 每秒恢复10个token
          $elapsed = $now - $this->tokens[$key]['time'];
          $this->tokens[$key]['count'] = min($limit, $this->tokens[$key]['count'] + $elapsed * 10);
          $this->tokens[$key]['time'] = $now;

          if ($this->tokens[$key]['count'] >= 1) {
              $this->tokens[$key]['count']--;
              return true;
          }
          return false;
      }

      function authenticate() {
          return isset($_SERVER['HTTP_AUTHORIZATION']); // 简化
      }
  }

  // 使用
  $gateway = new ApiGateway();

  // 请求分发
  $result = $gateway->handle('GET', '/user/123');
  // -> http://user-service-1/user/123 (轮询)

  $result = $gateway->handle('POST', '/order/create', json_encode(['amount' => 100]));
  // -> http://order-service-2/order/create

  echo "路由: /user/* -> user-service (2节点负载均衡)\n";
  echo "限流: 100req/s 令牌桶\n";
  echo "认证: JWT/OAuth\n";

  大白话: 网关统一入口，负责路由、负载均衡、限流、认证，转发到后端微服务。

  输出:
  请求流程:
  客户端 -> 网关(认证+限流) -> 路由选择 -> 后端服务

  /user/123 -> user-service-1 (负载均衡)
  /order/1  -> order-service-2 (轮询)

  网关功能:
  - 路由匹配(fnmatch)
  - 负载均衡(轮询/hash)
  - 限流(令牌桶 100req/s)
  - 认证(JWT)
  - 超时控制(3s)