//------------------------------------------------------------------------------
/*
    This file is part of Beast: https://github.com/vinniefalco/Beast

    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef BEAST_HTTP_WRITE_IPP_INCLUDED
#define BEAST_HTTP_WRITE_IPP_INCLUDED

#include <beast/http/chunk_encode.h>
#include <beast/http/resume_context.h>
#include <beast/http/type_check.h>
#include <beast/http/detail/writes.h>
#include <beast/http/detail/write_preparation.h>
#include <beast/asio/append_buffers.h>
#include <beast/asio/async_completion.h>
#include <beast/asio/bind_handler.h>
#include <beast/asio/handler_alloc.h>
#include <beast/asio/streambuf.h>
#include <beast/asio/type_check.h>
#include <boost/asio/write.hpp>
#include <boost/logic/tribool.hpp>
#include <condition_variable>
#include <mutex>
#include <beast/cxx17/type_traits.h> // <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,
                            append_buffers(d.wp.sb.data(),
                                chunk_encode(buffers)),
                                    std::move(*this));
                    else
                        boost::asio::async_write(d.s,
                            append_buffers(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, append_buffers(
                            wp.sb.data(), chunk_encode(buffers)), ec);
                    else
                        boost::asio::write(stream, append_buffers(
                            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