//
// Copyright (c) 2013-2016 Vinnie Falco (vinnie dot falco at gmail 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 BEAST_HTTP_IMPL_WRITE_IPP
#define BEAST_HTTP_IMPL_WRITE_IPP

#include <beast/http/chunk_encode.hpp>
#include <beast/http/resume_context.hpp>
#include <beast/http/type_check.hpp>
#include <beast/http/detail/writes.hpp>
#include <beast/http/detail/write_preparation.hpp>
#include <beast/buffer_cat.hpp>
#include <beast/async_completion.hpp>
#include <beast/bind_handler.hpp>
#include <beast/handler_alloc.hpp>
#include <beast/streambuf.hpp>
#include <beast/type_check.hpp>
#include <boost/asio/write.hpp>
#include <boost/logic/tribool.hpp>
#include <condition_variable>
#include <mutex>
#include <type_traits>

namespace beast {
namespace http {

namespace detail {

template<class Stream, class Handler,
    bool isRequest, class Body, class Headers>
class write_op
{
    using alloc_type =
        handler_alloc<char, Handler>;

    struct data
    {
        Stream& s;
        // VFALCO How do we use handler_alloc in write_preparation?
        write_preparation<
            isRequest, Body, Headers> wp;
        Handler h;
        resume_context resume;
        resume_context copy;
        bool cont;
        int state = 0;

        template<class DeducedHandler>
        data(DeducedHandler&& h_, Stream& s_,
                message<isRequest, Body, Headers> const& m_)
            : s(s_)
            , wp(m_)
            , h(std::forward<DeducedHandler>(h_))
            , cont(boost_asio_handler_cont_helpers::
                is_continuation(h))
        {
        }
    };

    std::shared_ptr<data> d_;

public:
    write_op(write_op&&) = default;
    write_op(write_op const&) = default;

    template<class DeducedHandler, class... Args>
    write_op(DeducedHandler&& h, Stream& s, Args&&... args)
        : d_(std::allocate_shared<data>(alloc_type{h},
            std::forward<DeducedHandler>(h), s,
                std::forward<Args>(args)...))
    {
        auto& d = *d_;
        d.resume = {
            [self = *this]() mutable
            {
                self.d_->cont = false;
                auto& ios = self.d_->s.get_io_service();
                ios.dispatch(bind_handler(std::move(self),
                    error_code{}, 0, false));
            }};
        d.copy = d.resume;
        (*this)(error_code{}, 0, false);
    }

    explicit
    write_op(std::shared_ptr<data> d)
        : d_(std::move(d))
    {
    }

    void
    operator()(error_code ec,
        std::size_t bytes_transferred, bool again = true);

    friend
    auto asio_handler_allocate(
        std::size_t size, write_op* op)
    {
        return boost_asio_handler_alloc_helpers::
            allocate(size, op->d_->h);
    }

    friend
    auto asio_handler_deallocate(
        void* p, std::size_t size, write_op* op)
    {
        return boost_asio_handler_alloc_helpers::
            deallocate(p, size, op->d_->h);
    }

    friend
    auto asio_handler_is_continuation(write_op* op)
    {
        return op->d_->cont;
    }

    template <class Function>
    friend
    auto asio_handler_invoke(Function&& f, write_op* op)
    {
        return boost_asio_handler_invoke_helpers::
            invoke(f, op->d_->h);
    }
};

template<class Stream, class Handler,
    bool isRequest, class Body, class Headers>
void
write_op<Stream, Handler, isRequest, Body, Headers>::
operator()(error_code ec, std::size_t, bool again)
{
    auto& d = *d_;
    d.cont = d.cont || again;
    while(! ec && d.state != 99)
    {
        switch(d.state)
        {
        case 0:
        {
            d.wp.init(ec);
            if(ec)
            {
                // call handler
                d.state = 99;
                d.s.get_io_service().post(bind_handler(
                    std::move(*this), ec, 0, false));
                return;
            }
            d.state = 1;
            break;
        }

        case 1:
        {
            auto const result = d.wp.w(std::move(d.copy), ec,
                [&](auto const& buffers)
                {
                    // write headers and body
                    if(d.wp.chunked)
                        boost::asio::async_write(d.s,
                            buffer_cat(d.wp.sb.data(),
                                chunk_encode(buffers)),
                                    std::move(*this));
                    else
                        boost::asio::async_write(d.s,
                            buffer_cat(d.wp.sb.data(),
                                buffers), std::move(*this));
                });
            if(ec)
            {
                // call handler
                d.state = 99;
                d.s.get_io_service().post(bind_handler(
                    std::move(*this), ec, false));
                return;
            }
            if(boost::indeterminate(result))
            {
                // suspend
                d.copy = d.resume;
                return;
            }
            if(result)
                d.state = d.wp.chunked ? 4 : 5;
            else
                d.state = 2;
            return;
        }

        // sent headers and body
        case 2:
            d.wp.sb.consume(d.wp.sb.size());
            d.state = 3;
            break;

        case 3:
        {
            auto const result = d.wp.w(std::move(d.copy), ec,
                [&](auto const& buffers)
                {
                    // write body
                    if(d.wp.chunked)
                        boost::asio::async_write(d.s,
                            chunk_encode(buffers),
                                std::move(*this));
                    else
                        boost::asio::async_write(d.s,
                            buffers, std::move(*this));
                });
            if(ec)
            {
                // call handler
                d.state = 99;
                break;
            }
            if(boost::indeterminate(result))
            {
                // suspend
                d.copy = d.resume;
                return;
            }
            if(result)
                d.state = d.wp.chunked ? 4 : 5;
            else
                d.state = 2;
            return;
        }

        case 4:
            // VFALCO Unfortunately the current interface to the
            //        Writer concept prevents us from using coalescing the
            //        final body chunk with the final chunk delimiter.
            //       
            // write final chunk
            d.state = 5;
            boost::asio::async_write(d.s,
                chunk_encode_final(), std::move(*this));
            return;

        case 5:
            if(d.wp.close)
            {
                // VFALCO TODO Decide on an error code
                ec = boost::asio::error::eof;
            }
            d.state = 99;
            break;
        }
    }
    d.h(ec);
    d.resume = {};
    d.copy = {};
}

} // detail

//------------------------------------------------------------------------------

template<class SyncWriteStream,
    bool isRequest, class Body, class Headers>
void
write(SyncWriteStream& stream,
    message<isRequest, Body, Headers> const& msg,
        boost::system::error_code& ec)
{
    static_assert(is_WritableBody<Body>::value,
        "WritableBody requirements not met");
    detail::write_preparation<isRequest, Body, Headers> wp(msg);
    wp.init(ec);
    if(ec)
        return;
    std::mutex m;
    std::condition_variable cv;
    bool ready = false;
    resume_context resume{
        [&]
        {
            std::lock_guard<std::mutex> lock(m);
            ready = true;
            cv.notify_one();
        }};
    auto copy = resume;
    for(;;)
    {
        {
            auto result = wp.w(std::move(copy), ec,
                [&](auto const& buffers)
                {
                    // write headers and body
                    if(wp.chunked)
                        boost::asio::write(stream, buffer_cat(
                            wp.sb.data(), chunk_encode(buffers)), ec);
                    else
                        boost::asio::write(stream, buffer_cat(
                            wp.sb.data(), buffers), ec);
                });
            if(ec)
                return;
            if(result)
                break;
            if(boost::indeterminate(result))
            {
                boost::asio::write(stream, wp.sb.data(), ec);
                if(ec)
                    return;
                wp.sb.consume(wp.sb.size());
                copy = resume;
                std::unique_lock<std::mutex> lock(m);
                cv.wait(lock, [&]{ return ready; });
                ready = false;
            }
        }
        wp.sb.consume(wp.sb.size());
        for(;;)
        {
            auto result = wp.w(std::move(copy), ec,
                [&](auto const& buffers)
                {
                    // write body
                    if(wp.chunked)
                        boost::asio::write(stream,
                            chunk_encode(buffers), ec);
                    else
                        boost::asio::write(stream, buffers, ec);
                });
            if(ec)
                return;
            if(result)
                break;
            if(boost::indeterminate(result))
            {
                copy = resume;
                std::unique_lock<std::mutex> lock(m);
                cv.wait(lock, [&]{ return ready; });
                ready = false;
            }
        }
    }
    if(wp.chunked)
    {
        // VFALCO Unfortunately the current interface to the
        //        Writer concept prevents us from using coalescing the
        //        final body chunk with the final chunk delimiter.
        //
        // write final chunk
        boost::asio::write(stream, chunk_encode_final(), ec);
        if(ec)
            return;
    }
    if(wp.close)
    {
        // VFALCO TODO Decide on an error code
        ec = boost::asio::error::eof;
    }
}

template<class AsyncWriteStream,
    bool isRequest, class Body, class Headers,
        class CompletionToken>
auto
async_write(AsyncWriteStream& stream,
    message<isRequest, Body, Headers> const& msg,
        CompletionToken&& token)
{
    static_assert(
        is_AsyncWriteStream<AsyncWriteStream>::value,
            "AsyncWriteStream requirements not met");
    static_assert(is_WritableBody<Body>::value,
        "WritableBody requirements not met");
    beast::async_completion<CompletionToken,
        void(error_code)> completion(token);
    detail::write_op<AsyncWriteStream, decltype(completion.handler),
        isRequest, Body, Headers>{completion.handler, stream, msg};
    return completion.result.get();
}

} // http
} // beast

#endif