//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

// Create a special transport factory that persists an existing
// transport client.  This is used to preserve the transport
// socket when other client components are restarted after
// a RELAY message is received from the server.

#ifndef OPENVPN_TRANSPORT_CLIENT_RELAY_H
#define OPENVPN_TRANSPORT_CLIENT_RELAY_H

#include <memory>

#include <openvpn/transport/client/transbase.hpp>

namespace openvpn {
  class TransportRelayFactory : public TransportClientFactory
  {
  public:
    TransportRelayFactory(openvpn_io::io_context& io_context,
			  TransportClient::Ptr transport,
			  TransportClientParent* old_parent)
      : io_context_(io_context),
	transport_(std::move(transport)),
	null_parent_(new NullParent(old_parent))
    {
      // Temporarily point transport to our null parent
      transport_->transport_reparent(null_parent_.get());
    }

    class TransportClientNull : public TransportClient
    {
    public:
      TransportClientNull(TransportClient* old)
	: endpoint_(old->server_endpoint_addr()),
	  protocol_(old->transport_protocol())
      {
	old->server_endpoint_info(host_, port_, proto_, ip_addr_);
      }

    private:
      virtual void transport_start() {}
      virtual void stop() {}
      virtual bool transport_send_const(const Buffer& buf) { return false; }
      virtual bool transport_send(BufferAllocated& buf) { return false; }
      virtual bool transport_send_queue_empty() { return false; }
      virtual bool transport_has_send_queue() { return false; }
      virtual unsigned int transport_send_queue_size() { return 0; }
      virtual void transport_stop_requeueing() { }
      virtual void reset_align_adjust(const size_t align_adjust) {}
      virtual void transport_reparent(TransportClientParent* parent) {}

      virtual IP::Addr server_endpoint_addr() const
      {
	return endpoint_;
      }

      virtual Protocol transport_protocol() const
      {
	return protocol_;
      }

      virtual void server_endpoint_info(std::string& host, std::string& port, std::string& proto, std::string& ip_addr) const
      {
	host = host_;
	port = port_;
	proto = proto_;
	ip_addr = ip_addr_;
      }

      IP::Addr endpoint_;
      Protocol protocol_;
      std::string host_;
      std::string port_;
      std::string proto_;
      std::string ip_addr_;
    };

  private:
    class NullParent : public TransportClientParent
    {
    public:
      NullParent(TransportClientParent* old_parent)
	: is_openvpn_protocol(old_parent->transport_is_openvpn_protocol())
      {
      }

    private:
      virtual void transport_recv(BufferAllocated& buf) {}
      virtual void transport_needs_send() {}

      virtual void transport_error(const Error::Type fatal_err, const std::string& err_text)
      {
	OPENVPN_LOG("TransportRelayFactory: Transport Error in null parent: " << Error::name(fatal_err) << " : " << err_text);
      }

      virtual void proxy_error(const Error::Type fatal_err, const std::string& err_text)
      {
	OPENVPN_LOG("TransportRelayFactory: Proxy Error in null parent: " << Error::name(fatal_err) << " : " << err_text);
      }

      // Return true if we are transporting OpenVPN protocol
      virtual bool transport_is_openvpn_protocol() { return is_openvpn_protocol; }

      // progress notifications
      virtual void transport_pre_resolve() {}
      virtual void transport_wait_proxy() {}
      virtual void transport_wait() {}
      virtual void transport_connecting() {}

      // Return true if keepalive parameter(s) are enabled.
      virtual bool is_keepalive_enabled() const { return false; }

      // Disable keepalive for rest of session, but fetch
      // the keepalive parameters (in seconds).
      virtual void disable_keepalive(unsigned int& keepalive_ping, unsigned int& keepalive_timeout)
      {
	keepalive_ping = 0;
	keepalive_timeout = 0;
      }

      bool is_openvpn_protocol;
    };

    virtual TransportClient::Ptr new_transport_client_obj(openvpn_io::io_context& io_context,
							  TransportClientParent* parent) override
    {
      // io_context MUST stay consistent
      if (&io_context != &io_context_)
	throw Exception("TransportRelayFactory: inconsistent io_context");

      transport_->transport_reparent(parent);
      return transport_;
    }

    virtual bool is_relay() override
    {
      return true;
    }

    openvpn_io::io_context& io_context_;                        // only used to verify consistency
    TransportClient::Ptr transport_;                      // the persisted transport
    std::unique_ptr<TransportClientParent> null_parent_;  // placeholder for TransportClient parent before reparenting
  };
}

#endif