// Copyright (c) 2006-2013, Andrey N. Sabelnikov, www.sabelnikov.net
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * 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.
// * Neither the name of the Andrey N. Sabelnikov nor the
// names of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER  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.
// 



#ifndef _LEVIN_BASE_H_
#define _LEVIN_BASE_H_

#include <cstdint>

#include "byte_stream.h"
#include "net_utils_base.h"
#include "span.h"

#define LEVIN_SIGNATURE  0x0101010101012101LL  //Bender's nightmare

namespace epee
{
class byte_slice;
namespace levin
{
#pragma pack(push)
#pragma pack(1)
	struct bucket_head
	{
		uint64_t m_signature;
		uint64_t m_cb;
		bool     m_have_to_return_data;
		uint32_t m_command;
		int32_t  m_return_code;
		uint32_t m_reservedA; //probably some flags in future
		uint32_t m_reservedB; //probably some check sum in future
	};
#pragma pack(pop)


#pragma pack(push)
#pragma pack(1)
  struct bucket_head2
  {
    uint64_t m_signature;
    uint64_t m_cb;
    bool     m_have_to_return_data;
    uint32_t m_command;
    int32_t  m_return_code;
    uint32_t m_flags;
    uint32_t m_protocol_version;
  };
#pragma pack(pop)


#define LEVIN_DEFAULT_TIMEOUT_PRECONFIGURED 0
#define LEVIN_INITIAL_MAX_PACKET_SIZE  256*1024      // 256 KiB before handshake
#define LEVIN_DEFAULT_MAX_PACKET_SIZE 100000000      //100MB by default after handshake

#define LEVIN_PACKET_REQUEST			0x00000001
#define LEVIN_PACKET_RESPONSE		0x00000002
#define LEVIN_PACKET_BEGIN		0x00000004
#define LEVIN_PACKET_END		0x00000008
  

#define LEVIN_PROTOCOL_VER_0         0
#define LEVIN_PROTOCOL_VER_1         1

 
  template<class t_connection_context = net_utils::connection_context_base>
  struct levin_commands_handler
  {
    virtual int invoke(int command, const epee::span<const uint8_t> in_buff, byte_stream& buff_out, t_connection_context& context)=0;
    virtual int notify(int command, const epee::span<const uint8_t> in_buff, t_connection_context& context)=0;
    virtual void callback(t_connection_context& context){};

    virtual void on_connection_new(t_connection_context& context){};
    virtual void on_connection_close(t_connection_context& context){};

    virtual ~levin_commands_handler(){}
  };

#define LEVIN_OK                                        0
#define LEVIN_ERROR_CONNECTION                         -1
#define LEVIN_ERROR_CONNECTION_NOT_FOUND               -2
#define LEVIN_ERROR_CONNECTION_DESTROYED               -3
#define LEVIN_ERROR_CONNECTION_TIMEDOUT                -4
#define LEVIN_ERROR_CONNECTION_NO_DUPLEX_PROTOCOL      -5
#define LEVIN_ERROR_CONNECTION_HANDLER_NOT_DEFINED     -6
#define LEVIN_ERROR_FORMAT                             -7

#define DESCRIBE_RET_CODE(code) case code: return #code;
  inline
  const char* get_err_descr(int err)
  {
    switch(err)
    {
      DESCRIBE_RET_CODE(LEVIN_OK);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION_NOT_FOUND);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION_DESTROYED);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION_TIMEDOUT);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION_NO_DUPLEX_PROTOCOL);
      DESCRIBE_RET_CODE(LEVIN_ERROR_CONNECTION_HANDLER_NOT_DEFINED);
      DESCRIBE_RET_CODE(LEVIN_ERROR_FORMAT);
    default:
      return "unknown code";
    }
  }

  //! Provides space for levin (p2p) header, so that payload can be sent without copy
  class message_writer
  {
    byte_slice finalize(uint32_t command, uint32_t flags, uint32_t return_code, bool expect_response);
  public:
    using header = bucket_head2;

    explicit message_writer(std::size_t reserve = 8192);

    message_writer(const message_writer&) = delete;
    message_writer(message_writer&&) = default;
    ~message_writer() = default;
    message_writer& operator=(const message_writer&) = delete;
    message_writer& operator=(message_writer&&) = default;

    //! \return Size of payload (excludes header size).
    std::size_t payload_size() const noexcept
    {
      return buffer.size() < sizeof(header) ? 0 : buffer.size() - sizeof(header);
    }

    byte_slice finalize_invoke(uint32_t command) { return finalize(command, LEVIN_PACKET_REQUEST, 0, true); }
    byte_slice finalize_notify(uint32_t command) { return finalize(command, LEVIN_PACKET_REQUEST, 0, false); }
    byte_slice finalize_response(uint32_t command, uint32_t return_code)
    {
      return finalize(command, LEVIN_PACKET_RESPONSE, return_code, false);
    }

    //! Has space for levin header until a finalize method is used
    byte_stream buffer;
  };

  //! \return Intialized levin header.
  bucket_head2 make_header(uint32_t command, uint64_t msg_size, uint32_t flags, bool expect_response) noexcept;

  /*! Generate a dummy levin message.

      \param noise_bytes Total size of the returned `byte_slice`.
      \return `nullptr` if `noise_size` is smaller than the levin header.
        Otherwise, a dummy levin message. */
  byte_slice make_noise_notify(std::size_t noise_bytes);

  /*! Generate 1+ levin messages that are identical to the noise message size.

   \param noise_size Each levin message will be identical to this value.
   \return `nullptr` if `noise.size()` is less than the levin header size.
      Otherwise, a levin notification message OR 2+ levin fragment messages.
      Each message is `noise.size()` in length. */
  byte_slice make_fragmented_notify(const std::size_t noise_size, int command, message_writer message);
}
}


#endif //_LEVIN_BASE_H_

