//    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/>.

// A queue of buffers for handling streamed data such as data received
// from or to be sent to a TCP socket

#ifndef OPENVPN_FRAME_MEMQ_STREAM_H
#define OPENVPN_FRAME_MEMQ_STREAM_H

#include <algorithm>

#include <openvpn/common/size.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/buffer/memq.hpp>
#include <openvpn/frame/frame.hpp>

namespace openvpn {

  class MemQStream : public MemQBase {
  public:
    OPENVPN_SIMPLE_EXCEPTION(frame_uninitialized);

    MemQStream() {}
    explicit MemQStream(const Frame::Ptr& frame) : frame_(frame) {}
    void set_frame(const Frame::Ptr& frame) { frame_ = frame; }

    size_t pending() const
    {
      return total_length();
    }

    void write(const unsigned char *data, size_t size)
    {
      if (frame_)
	{
	  const Frame::Context& fc = (*frame_)[Frame::READ_BIO_MEMQ_STREAM];
	  if (size)
	    {
	      ConstBuffer b(data, size, true);
	      // Any residual space remaining in most recently pushed buffer?
	      if (!q.empty())
		{
		  BufferPtr& qb = q.back();
		  const size_t write_size = std::min(b.size(), fc.remaining_payload(*qb));
		  const unsigned char *from = b.read_alloc(write_size);
		  qb->write(from, write_size);
		  length += write_size;
		}

	      // Start a new buffer
	      while (b.size())
		{
		  BufferPtr newbuf(new BufferAllocated);
		  fc.prepare(*newbuf);
		  const size_t write_size = std::min(b.size(), fc.payload());
		  const unsigned char *from = b.read_alloc(write_size);
		  newbuf->write(from, write_size);
		  q.push_back(newbuf);
		  length += write_size;
		}
	    }
	}
      else
	throw frame_uninitialized();
    }

    size_t read(unsigned char *data, size_t len)
    {
      Buffer b(data, len, false);
      while (!q.empty())
	{
	  const size_t remaining = b.remaining();
	  if (!remaining)
	    break;
	  BufferPtr& qf = q.front();
	  const size_t read_size = std::min(remaining, qf->size());
	  unsigned char *to = b.write_alloc(read_size);
	  qf->read(to, read_size);
	  length -= read_size;
	  if (qf->empty())
	    q.pop_front();
	}
      return b.size();
    }

  private:
    Frame::Ptr frame_;
  };

} // namespace openvpn

#endif // OPENVPN_FRAME_MEMQ_STREAM_H