/*
 * Copyright (c) 2015 Cryptonomex, Inc., and contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 * 1. Any modified source or binaries are used only with the BitShares network.
 *
 * 2. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *
 * 3. 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.
 *
 * 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 HOLDER OR
 * CONTRIBUTORS 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.
 *
 */
#include <assert.h>

#include <algorithm>

#include <fc/crypto/hex.hpp>
#include <fc/crypto/aes.hpp>
#include <fc/crypto/city.hpp>
#include <fc/log/logger.hpp>
#include <fc/network/ip.hpp>
#include <fc/exception/exception.hpp>

#include <graphene/p2p/stcp_socket.hpp>

namespace graphene { namespace p2p {

stcp_socket::stcp_socket()
//:_buf_len(0)
#ifndef NDEBUG
   : _read_buffer_in_use(false),
     _write_buffer_in_use(false)
#endif
{
}
stcp_socket::~stcp_socket()
{
}

void stcp_socket::do_key_exchange()
{
  _priv_key = fc::ecc::private_key::generate();
  fc::ecc::public_key pub = _priv_key.get_public_key();
  fc::ecc::public_key_data s = pub.serialize();
  std::shared_ptr<char> serialized_key_buffer(new char[sizeof(fc::ecc::public_key_data)], [](char* p){ delete[] p; });
  memcpy(serialized_key_buffer.get(), (char*)&s, sizeof(fc::ecc::public_key_data));
  _sock.write( serialized_key_buffer, sizeof(fc::ecc::public_key_data) );
  _sock.read( serialized_key_buffer, sizeof(fc::ecc::public_key_data) );
  fc::ecc::public_key_data rpub;
  memcpy((char*)&rpub, serialized_key_buffer.get(), sizeof(fc::ecc::public_key_data));

  _shared_secret = _priv_key.get_shared_secret( rpub );
//    ilog("shared secret ${s}", ("s", shared_secret) );
  _send_aes.init( fc::sha256::hash( (char*)&_shared_secret, sizeof(_shared_secret) ), 
                  fc::city_hash_crc_128((char*)&_shared_secret,sizeof(_shared_secret) ) );
  _recv_aes.init( fc::sha256::hash( (char*)&_shared_secret, sizeof(_shared_secret) ), 
                  fc::city_hash_crc_128((char*)&_shared_secret,sizeof(_shared_secret) ) );
}


void stcp_socket::connect_to( const fc::ip::endpoint& remote_endpoint )
{
  _sock.connect_to( remote_endpoint );
  do_key_exchange();
}

void stcp_socket::bind( const fc::ip::endpoint& local_endpoint )
{
  _sock.bind(local_endpoint);
}

/**
 *   This method must read at least 16 bytes at a time from
 *   the underlying TCP socket so that it can decrypt them. It
 *   will buffer any left-over.
 */
size_t stcp_socket::readsome( char* buffer, size_t len )
{ try {
    assert( len > 0 && (len % 16) == 0 );

#ifndef NDEBUG
    // This code was written with the assumption that you'd only be making one call to readsome 
    // at a time so it reuses _read_buffer.  If you really need to make concurrent calls to 
    // readsome(), you'll need to prevent reusing _read_buffer here
    struct check_buffer_in_use {
      bool& _buffer_in_use;
      check_buffer_in_use(bool& buffer_in_use) : _buffer_in_use(buffer_in_use) { assert(!_buffer_in_use); _buffer_in_use = true; }
      ~check_buffer_in_use() { assert(_buffer_in_use); _buffer_in_use = false; }
    } buffer_in_use_checker(_read_buffer_in_use);
#endif

    const size_t read_buffer_length = 4096;
    if (!_read_buffer)
      _read_buffer.reset(new char[read_buffer_length], [](char* p){ delete[] p; });

    len = std::min<size_t>(read_buffer_length, len);

    size_t s = _sock.readsome( _read_buffer, len, 0 );
    if( s % 16 ) 
    {
      _sock.read(_read_buffer, 16 - (s%16), s);
      s += 16-(s%16);
    }
    _recv_aes.decode( _read_buffer.get(), s, buffer );
    return s;
} FC_RETHROW_EXCEPTIONS( warn, "", ("len",len) ) }

size_t stcp_socket::readsome( const std::shared_ptr<char>& buf, size_t len, size_t offset ) 
{
  return readsome(buf.get() + offset, len);
}

bool stcp_socket::eof()const
{
  return _sock.eof();
}

size_t stcp_socket::writesome( const char* buffer, size_t len )
{ try {
    assert( len > 0 && (len % 16) == 0 );

#ifndef NDEBUG
    // This code was written with the assumption that you'd only be making one call to writesome
    // at a time so it reuses _write_buffer.  If you really need to make concurrent calls to 
    // writesome(), you'll need to prevent reusing _write_buffer here
    struct check_buffer_in_use {
      bool& _buffer_in_use;
      check_buffer_in_use(bool& buffer_in_use) : _buffer_in_use(buffer_in_use) { assert(!_buffer_in_use); _buffer_in_use = true; }
      ~check_buffer_in_use() { assert(_buffer_in_use); _buffer_in_use = false; }
    } buffer_in_use_checker(_write_buffer_in_use);
#endif

    const std::size_t write_buffer_length = 4096;
    if (!_write_buffer)
      _write_buffer.reset(new char[write_buffer_length], [](char* p){ delete[] p; });
    len = std::min<size_t>(write_buffer_length, len);
    memset(_write_buffer.get(), 0, len); // just in case aes.encode screws up
    /**
     * every sizeof(crypt_buf) bytes the aes channel
     * has an error and doesn't decrypt properly...  disable
     * for now because we are going to upgrade to something
     * better.
     */
    uint32_t ciphertext_len = _send_aes.encode( buffer, len, _write_buffer.get() );
    assert(ciphertext_len == len);
    _sock.write( _write_buffer, ciphertext_len );
    return ciphertext_len;
} FC_RETHROW_EXCEPTIONS( warn, "", ("len",len) ) }

size_t stcp_socket::writesome( const std::shared_ptr<const char>& buf, size_t len, size_t offset )
{
  return writesome(buf.get() + offset, len);
}

void stcp_socket::flush()
{
  _sock.flush();
}


void stcp_socket::close()
{
  try 
  {
    _sock.close();
  }FC_RETHROW_EXCEPTIONS( warn, "error closing stcp socket" );
}

void stcp_socket::accept()
{
  do_key_exchange();
}


}} // namespace graphene::p2p