text: /*
   * Copyright (c) 2016-20017 Max Cong <savagecm@qq.com>
   * this code can be found at https://github.com/maxcong001/translib_on_top_of_0mq
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  #pragma once
  #include <functional>
  #include <chrono>
  #include <list>
  #include <mutex>
  #include <condition_variable>
  class dns_service_interface
  {
  public:
    typedef std::function<void(std::list<std::string> &)> DNS_CB_FUNC_SERVER;
    typedef std::function<void(std::string)> DNS_CB_FUNC_APP;
    bool set_dns_cb(DNS_CB_FUNC_SERVER cb)
    {
      if (cb)
      {
        dns_cb_server = cb;
        return true;
      }
      else
      {
        return false;
      }
    }
    DNS_CB_FUNC_SERVER get_dns_cb()
    {
      return dns_cb_server;
    }
  
    bool getIPList()
    {
      dns_cb_app(remote_fqdn);
  
      std::unique_lock<std::mutex> dnsLock(dnsMutex);
      if (dnsCond.wait_for(dnsLock, std::chrono::seconds(5)) == std::cv_status::timeout)
      {
        if (IpList.empty())
        {
          return false;
        }
        (IpList);
      }
      else
      {
        return false;
      }
    }
    void setIPList(std::list<std::string> list)
    {
      IpList = list;
    }
  
    bool set_remote_fqdn(std::string fqdn)
    {
      remote_fqdn = fqdn;
      return true;
    }
    std::string get_remote_fqdn()
    {
      return remote_fqdn;
    }
  
  private:
    // this is the function which server register to DNS service.
    // when IPlist come back, should call this function
    DNS_CB_FUNC_SERVER dns_cb_server;
    // this function is provide by application
    // the input is FQND string.
    DNS_CB_FUNC_APP dns_cb_app;
    std::list<std::string> IpList;
    std::string remote_fqdn;
  
    std::mutex dnsMutex;
    std::condition_variable dnsCond;
  };