/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
/**
 * Copyright (C) 2013 Regents of the University of California.
 * @author: Jeff Thompson <jefft0@remap.ucla.edu>
 * See COPYING for copyright and distribution information.
 */

#include "common.hpp"

#include "tcp-transport.hpp"

#if NDN_CPP_HAVE_CXX11
// In the std library, the placeholders are in a different namespace than boost.
using namespace ndn::func_lib::placeholders;
#endif

using namespace std;
typedef boost::asio::ip::tcp protocol;

namespace ndn {

const size_t MAX_LENGTH = 9000;

class TcpTransport::Impl
{
public:
  Impl(TcpTransport &transport)
    : transport_(transport)
    , socket_(*transport_.ioService_)
    , partialDataSize_(0)
    , connectionInProgress_(false)
    , connectTimer_(*transport_.ioService_)
  {
  }

  void
  connectHandler(const boost::system::error_code& error)
  {
    connectionInProgress_ = false;
    connectTimer_.cancel();

    if (!error)
      {
        partialDataSize_ = 0;
        socket_.async_receive(boost::asio::buffer(inputBuffer_, MAX_LENGTH), 0,
                              func_lib::bind(&Impl::handle_async_receive, this, _1, _2));

        transport_.isConnected_ = true;

        for (std::list<Block>::iterator i = sendQueue_.begin(); i != sendQueue_.end(); ++i)
          socket_.async_send(boost::asio::buffer(i->wire(), i->size()),
                             func_lib::bind(&Impl::handle_async_send, this, _1, *i));

        sendQueue_.clear();
      }
    else
      {
        // may need to throw exception
        transport_.isConnected_ = false;
        transport_.close();
        throw Transport::Error(error, "error while connecting to the forwarder");
      }
  }

  void
  connectTimeoutHandler(const boost::system::error_code& error)
  {
    if (error) // e.g., cancelled timer
      return;

    connectionInProgress_ = false;
    transport_.isConnected_ = false;
    socket_.close();
    throw Transport::Error(error, "error while connecting to the forwarder");
  }

  void
  resolveHandler(const boost::system::error_code& error,
                 boost::asio::ip::tcp::resolver::iterator endpoint,
                 const ptr_lib::shared_ptr<boost::asio::ip::tcp::resolver>&)
  {
    if (error)
      {
        if (error == boost::system::errc::operation_canceled)
          return;
        
        throw Transport::Error(error, "Error during resolution of host or port [" + transport_.host_ + ":" + transport_.port_ + "]");
      }
    
    boost::asio::ip::tcp::resolver::iterator end;
    if (endpoint == end)
      {
        connectionInProgress_ = false;
        transport_.isConnected_ = false;
        socket_.close();
        throw Transport::Error(error, "Unable to connect because host or port [" + transport_.host_ + ":" + transport_.port_ + "] cannot be resolved");
      }

    socket_.async_connect(*endpoint,
                          func_lib::bind(&Impl::connectHandler, this, _1));
  }
  
  void
  connect()
  {
    if (!connectionInProgress_) {
      connectionInProgress_ = true;

      // Wait at most 4 seconds to connect
      /// @todo Decide whether this number should be configurable
      connectTimer_.expires_from_now(boost::posix_time::seconds(4));
      connectTimer_.async_wait(func_lib::bind(&Impl::connectTimeoutHandler, this, _1));
      
      using boost::asio::ip::tcp;
      
      ptr_lib::shared_ptr<tcp::resolver> resolver =
        ptr_lib::make_shared<tcp::resolver>(boost::ref(*transport_.ioService_));

      tcp::resolver::query query(transport_.host_, transport_.port_);

      resolver->async_resolve(query, func_lib::bind(&Impl::resolveHandler, this, _1, _2, resolver));
    }
  }

  void 
  close()
  {
    connectTimer_.cancel();
    socket_.close();
    transport_.isConnected_ = false;
  }

  void 
  send(const Block &wire)
  {
    if (!transport_.isConnected_)
      sendQueue_.push_back(wire);
    else
      socket_.async_send(boost::asio::buffer(wire.wire(), wire.size()),
                         func_lib::bind(&Impl::handle_async_send, this, _1, wire));
  }

  inline void
  processAll(uint8_t *buffer, size_t &offset, size_t availableSize)
  {
    while(offset < availableSize)
      {
        Block element(buffer + offset, availableSize - offset);
        transport_.receive(element);

        offset += element.size();
      }
  }
  
  void
  handle_async_receive(const boost::system::error_code& error, std::size_t bytes_recvd)
  {
    /// @todo The socket is not datagram, so need to have internal buffer to handle partial data reception

    if (error)
      {
        if (error == boost::system::errc::operation_canceled) {
          // async receive has been explicitly cancelled (e.g., socket close)
          return;
        }
        
        socket_.close(); // closing at this point may not be that necessary
        transport_.isConnected_ = true;
        throw Transport::Error(error, "error while receiving data from socket");
      }
    
    if (!error && bytes_recvd > 0)
      {
        // inputBuffer_ has bytes_recvd received bytes of data
        if (partialDataSize_ > 0)
          {
            size_t newDataSize = std::min(bytes_recvd, MAX_LENGTH-partialDataSize_);
            std::copy(inputBuffer_, inputBuffer_ + newDataSize, partialData_ + partialDataSize_);

            partialDataSize_ += newDataSize;
              
            size_t offset = 0;
            try
              {
                processAll(partialData_, offset, partialDataSize_);

                // no exceptions => processed the whole thing
                if (bytes_recvd - newDataSize > 0)
                  {
                    // there is a little bit more data available
                        
                    offset = 0;
                    partialDataSize_ = bytes_recvd - newDataSize;
                    std::copy(inputBuffer_ + newDataSize, inputBuffer_ + newDataSize + partialDataSize_, partialData_);

                    processAll(partialData_, offset, partialDataSize_);

                    // no exceptions => processed the whole thing
                    partialDataSize_ = 0;
                  }
                else
                  {
                    // done processing
                    partialDataSize_ = 0;
                  }
              }
            catch(Tlv::Error &)
              {
                if (offset > 0)
                  {
                    partialDataSize_ -= offset;
                    std::copy(partialData_ + offset, partialData_ + offset + partialDataSize_, partialData_);
                  }
                else if (offset == 0 && partialDataSize_ == MAX_LENGTH)
                  {
                    // very bad... should close connection
                    socket_.close();
                    transport_.isConnected_ = true;
                    throw Transport::Error(boost::system::error_code(), "input buffer full, but a valid TLV cannot be decoded");
                  }
              }
          }
        else
          {
            size_t offset = 0;
            try
              {
                processAll(inputBuffer_, offset, bytes_recvd);
              }
            catch(Tlv::Error &error)
              {
                if (offset > 0)
                  {
                    partialDataSize_ = bytes_recvd - offset;
                    std::copy(inputBuffer_ + offset, inputBuffer_ + offset + partialDataSize_, partialData_);
                  }
              }
          }
      }

    socket_.async_receive(boost::asio::buffer(inputBuffer_, MAX_LENGTH), 0,
                          func_lib::bind(&Impl::handle_async_receive, this, _1, _2));
  }

  void
  handle_async_send(const boost::system::error_code& error, const Block &wire)
  {
    // pass (needed to keep data block alive during the send)
  }
  
private:
  TcpTransport &transport_;
  
  protocol::socket socket_;
  uint8_t inputBuffer_[MAX_LENGTH];

  uint8_t partialData_[MAX_LENGTH];
  size_t partialDataSize_;

  std::list< Block > sendQueue_;
  bool connectionInProgress_;

  boost::asio::deadline_timer connectTimer_;
};

TcpTransport::TcpTransport(const std::string& host, const std::string& port/* = "6363"*/)
  : host_(host)
  , port_(port)
{
}

TcpTransport::~TcpTransport()
{
}

void 
TcpTransport::connect(boost::asio::io_service &ioService,
                      const ReceiveCallback &receiveCallback)
{
  if (!static_cast<bool>(impl_)) {
    Transport::connect(ioService, receiveCallback);
  
    impl_ = ptr_lib::make_shared<TcpTransport::Impl> (ptr_lib::ref(*this));
  }
  impl_->connect();
}

void 
TcpTransport::send(const Block &wire)
{
  impl_->send(wire);
}

void 
TcpTransport::close()
{
  impl_->close();
}

}