//
// ssl/detail/buffered_handshake_op.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP
#define ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
#pragma once
#endif  // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/config.hpp"

#include "mongo/util/net/ssl/detail/engine.hpp"

#include "asio/detail/push_options.hpp"

namespace asio {
namespace ssl {
namespace detail {

template <typename ConstBufferSequence>
class buffered_handshake_op {
public:
    buffered_handshake_op(stream_base::handshake_type type, const ConstBufferSequence& buffers)
        : type_(type), buffers_(buffers), total_buffer_size_(asio::buffer_size(buffers_)) {}

    engine::want operator()(engine& eng,
                            asio::error_code& ec,
                            std::size_t& bytes_transferred) const {
        return this->process(eng,
                             ec,
                             bytes_transferred,
                             asio::buffer_sequence_begin(buffers_),
                             asio::buffer_sequence_end(buffers_));
    }

    template <typename Handler>
    void call_handler(Handler& handler,
                      const asio::error_code& ec,
                      const std::size_t& bytes_transferred) const {
        handler(ec, bytes_transferred);
    }

private:
    template <typename Iterator>
    engine::want process(engine& eng,
                         asio::error_code& ec,
                         std::size_t& bytes_transferred,
                         Iterator begin,
                         Iterator end) const {
        Iterator iter = begin;
        std::size_t accumulated_size = 0;

        for (;;) {
            engine::want want = eng.handshake(type_, ec);
            if (want != engine::want_input_and_retry || bytes_transferred == total_buffer_size_)
                return want;

            // Find the next buffer piece to be fed to the engine.
            while (iter != end) {
                const_buffer buffer(*iter);

                // Skip over any buffers which have already been consumed by the engine.
                if (bytes_transferred >= accumulated_size + buffer.size()) {
                    accumulated_size += buffer.size();
                    ++iter;
                    continue;
                }

                // The current buffer may have been partially consumed by the engine on
                // a previous iteration. If so, adjust the buffer to point to the
                // unused portion.
                if (bytes_transferred > accumulated_size)
                    buffer = buffer + (bytes_transferred - accumulated_size);

                // Pass the buffer to the engine, and update the bytes transferred to
                // reflect the total number of bytes consumed so far.
                bytes_transferred += buffer.size();
                buffer = eng.put_input(buffer);
                bytes_transferred -= buffer.size();
                break;
            }
        }
    }

    stream_base::handshake_type type_;
    ConstBufferSequence buffers_;
    std::size_t total_buffer_size_;
};

}  // namespace detail
}  // namespace ssl
}  // namespace asio

#include "asio/detail/pop_options.hpp"

#endif  // ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP
