//------------------------------------------------------------------------------
/*
    This file is part of clio: https://github.com/XRPLF/clio
    Copyright (c) 2024, the clio developers.

    Permission to use, copy, modify, and 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.
*/
//==============================================================================

#pragma once

#include "util/OverloadSet.hpp"
#include "util/Taggable.hpp"
#include "util/build/Build.hpp"
#include "web/ng/Connection.hpp"
#include "web/ng/Error.hpp"
#include "web/ng/Request.hpp"
#include "web/ng/Response.hpp"
#include "web/ng/impl/Concepts.hpp"
#include "web/ng/impl/SendingQueue.hpp"

#include <boost/asio/buffer.hpp>
#include <boost/asio/ip/tcp.hpp>
#include <boost/asio/spawn.hpp>
#include <boost/asio/ssl/context.hpp>
#include <boost/asio/ssl/stream.hpp>
#include <boost/beast/core/buffers_to_string.hpp>
#include <boost/beast/core/flat_buffer.hpp>
#include <boost/beast/core/role.hpp>
#include <boost/beast/core/tcp_stream.hpp>
#include <boost/beast/http/field.hpp>
#include <boost/beast/http/message.hpp>
#include <boost/beast/http/string_body.hpp>
#include <boost/beast/ssl.hpp>
#include <boost/beast/websocket/rfc6455.hpp>
#include <boost/beast/websocket/stream.hpp>
#include <boost/beast/websocket/stream_base.hpp>

#include <chrono>
#include <memory>
#include <optional>
#include <string>
#include <utility>
#include <variant>

namespace web::ng::impl {

class WsConnectionBase : public Connection {
public:
    using Connection::Connection;

    virtual std::expected<void, Error>
    sendShared(std::shared_ptr<std::string> message, boost::asio::yield_context yield) = 0;
};

template <typename StreamType>
class WsConnection : public WsConnectionBase {
    boost::beast::websocket::stream<StreamType> stream_;
    boost::beast::http::request<boost::beast::http::string_body> initialRequest_;

    using MessageType = std::variant<Response, std::shared_ptr<std::string>>;
    SendingQueue<MessageType> sendingQueue_;

    bool closed_{false};

public:
    WsConnection(
        StreamType&& stream,
        std::string ip,
        boost::beast::flat_buffer buffer,
        boost::beast::http::request<boost::beast::http::string_body> initialRequest,
        util::TagDecoratorFactory const& tagDecoratorFactory
    )
        : WsConnectionBase(std::move(ip), std::move(buffer), tagDecoratorFactory)
        , stream_(std::move(stream))
        , initialRequest_(std::move(initialRequest))
        , sendingQueue_{[this](MessageType const& message, auto&& yield) {
            boost::asio::const_buffer const buffer = std::visit(
                util::OverloadSet{
                    [](Response const& r) -> boost::asio::const_buffer { return r.asWsResponse(); },
                    [](std::shared_ptr<std::string> const& m) -> boost::asio::const_buffer {
                        return boost::asio::buffer(*m);
                    }
                },
                message
            );
            stream_.async_write(buffer, yield);
        }}
    {
        setupWsStream();
    }

    ~WsConnection() override = default;
    WsConnection(WsConnection&&) = delete;
    WsConnection&
    operator=(WsConnection&&) = delete;
    WsConnection(WsConnection const&) = delete;
    WsConnection&
    operator=(WsConnection const&) = delete;

    std::expected<void, Error>
    performHandshake(boost::asio::yield_context yield)
    {
        Error error;
        stream_.async_accept(initialRequest_, yield[error]);
        if (error)
            return std::unexpected{error};
        return {};
    }

    bool
    wasUpgraded() const override
    {
        return true;
    }

    std::expected<void, Error>
    sendShared(std::shared_ptr<std::string> message, boost::asio::yield_context yield) override
    {
        return sendingQueue_.send(std::move(message), yield);
    }

    void
    setTimeout(std::chrono::steady_clock::duration newTimeout) override
    {
        boost::beast::websocket::stream_base::timeout wsTimeout =
            boost::beast::websocket::stream_base::timeout::suggested(boost::beast::role_type::server);
        wsTimeout.idle_timeout = newTimeout;
        wsTimeout.handshake_timeout = newTimeout;
        stream_.set_option(wsTimeout);
    }

    std::expected<void, Error>
    send(Response response, boost::asio::yield_context yield) override
    {
        return sendingQueue_.send(std::move(response), yield);
    }

    std::expected<Request, Error>
    receive(boost::asio::yield_context yield) override
    {
        Error error;
        stream_.async_read(buffer_, yield[error]);
        if (error)
            return std::unexpected{error};

        auto request = boost::beast::buffers_to_string(buffer_.data());
        buffer_.consume(buffer_.size());

        return Request{std::move(request), initialRequest_};
    }

    void
    close(boost::asio::yield_context yield) override
    {
        if (closed_)
            return;

        // This should be set before the async_close(). Otherwise there is a possibility to have multiple coroutines
        // waiting on async_close(), but only one will be woken up after the actual close happened, others will hang.
        closed_ = true;

        boost::system::error_code error;  // unused
        stream_.async_close(boost::beast::websocket::close_code::normal, yield[error]);
    }

private:
    void
    setupWsStream()
    {
        // Disable the timeout. The websocket::stream uses its own timeout settings.
        boost::beast::get_lowest_layer(stream_).expires_never();
        setTimeout(kDEFAULT_TIMEOUT);
        stream_.set_option(
            boost::beast::websocket::stream_base::decorator([](boost::beast::websocket::response_type& res) {
                res.set(boost::beast::http::field::server, util::build::getClioFullVersionString());
            })
        );
    }
};

using PlainWsConnection = WsConnection<boost::beast::tcp_stream>;
using SslWsConnection = WsConnection<boost::asio::ssl::stream<boost::beast::tcp_stream>>;

template <typename StreamType>
std::expected<std::unique_ptr<WsConnection<StreamType>>, Error>
makeWsConnection(
    StreamType&& stream,
    std::string ip,
    boost::beast::flat_buffer buffer,
    boost::beast::http::request<boost::beast::http::string_body> request,
    util::TagDecoratorFactory const& tagDecoratorFactory,
    boost::asio::yield_context yield
)
{
    auto connection = std::make_unique<WsConnection<StreamType>>(
        std::forward<StreamType>(stream), std::move(ip), std::move(buffer), std::move(request), tagDecoratorFactory
    );
    auto const expectedSuccess = connection->performHandshake(yield);
    if (not expectedSuccess.has_value())
        return std::unexpected{expectedSuccess.error()};
    return connection;
}

}  // namespace web::ng::impl