//------------------------------------------------------------------------------
/*
    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/Assert.hpp"
#include "util/Taggable.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/WsConnection.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/asio/ssl/stream_base.hpp>
#include <boost/beast/core/basic_stream.hpp>
#include <boost/beast/core/error.hpp>
#include <boost/beast/core/flat_buffer.hpp>
#include <boost/beast/core/tcp_stream.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/http/message.hpp>
#include <boost/beast/http/string_body.hpp>
#include <boost/beast/websocket.hpp>

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

namespace web::ng::impl {

class UpgradableConnection : public Connection {
public:
    using Connection::Connection;

    virtual std::expected<bool, Error>
    isUpgradeRequested(boost::asio::yield_context yield) = 0;

    virtual std::expected<ConnectionPtr, Error>
    upgrade(util::TagDecoratorFactory const& tagDecoratorFactory, boost::asio::yield_context yield) = 0;

    virtual std::optional<Error>
    sendRaw(
        boost::beast::http::response<boost::beast::http::string_body> response,
        boost::asio::yield_context yield
    ) = 0;
};

using UpgradableConnectionPtr = std::unique_ptr<UpgradableConnection>;

template <typename StreamType>
class HttpConnection : public UpgradableConnection {
    StreamType stream_;
    std::optional<boost::beast::http::request<boost::beast::http::string_body>> request_;
    std::chrono::steady_clock::duration timeout_{kDEFAULT_TIMEOUT};
    bool closed_{false};

public:
    HttpConnection(
        boost::asio::ip::tcp::socket socket,
        std::string ip,
        boost::beast::flat_buffer buffer,
        util::TagDecoratorFactory const& tagDecoratorFactory
    )
        requires IsTcpStream<StreamType>
        : UpgradableConnection(std::move(ip), std::move(buffer), tagDecoratorFactory), stream_{std::move(socket)}
    {
    }

    HttpConnection(
        boost::asio::ip::tcp::socket socket,
        std::string ip,
        boost::beast::flat_buffer buffer,
        boost::asio::ssl::context& sslCtx,
        util::TagDecoratorFactory const& tagDecoratorFactory
    )
        requires IsSslTcpStream<StreamType>
        : UpgradableConnection(std::move(ip), std::move(buffer), tagDecoratorFactory)
        , stream_{std::move(socket), sslCtx}
    {
    }

    std::optional<Error>
    sslHandshake(boost::asio::yield_context yield)
        requires IsSslTcpStream<StreamType>
    {
        boost::system::error_code error;
        boost::beast::get_lowest_layer(stream_).expires_after(timeout_);
        auto const bytesUsed =
            stream_.async_handshake(boost::asio::ssl::stream_base::server, buffer_.cdata(), yield[error]);
        if (error)
            return error;

        buffer_.consume(bytesUsed);

        return std::nullopt;
    }

    bool
    wasUpgraded() const override
    {
        return false;
    }

    std::optional<Error>
    sendRaw(boost::beast::http::response<boost::beast::http::string_body> response, boost::asio::yield_context yield)
        override
    {
        boost::system::error_code error;
        boost::beast::get_lowest_layer(stream_).expires_after(timeout_);
        boost::beast::http::async_write(stream_, response, yield[error]);
        if (error)
            return error;
        return std::nullopt;
    }

    void
    setTimeout(std::chrono::steady_clock::duration newTimeout) override
    {
        timeout_ = newTimeout;
    }

    std::optional<Error>
    send(Response response, boost::asio::yield_context yield) override
    {
        auto httpResponse = std::move(response).intoHttpResponse();
        return sendRaw(std::move(httpResponse), yield);
    }

    std::expected<Request, Error>
    receive(boost::asio::yield_context yield) override
    {
        if (request_.has_value()) {
            Request result{std::move(request_).value()};
            request_.reset();
            return result;
        }
        auto expectedRequest = fetch(yield);
        if (expectedRequest.has_value())
            return Request{std::move(expectedRequest).value()};

        return std::unexpected{std::move(expectedRequest).error()};
    }

    void
    close(boost::asio::yield_context yield) override
    {
        // This is needed because calling async_shutdown() multiple times may lead to hanging coroutines.
        // See WsConnection for more details.
        if (closed_)
            return;

        closed_ = true;

        [[maybe_unused]] boost::system::error_code error;
        if constexpr (IsSslTcpStream<StreamType>) {
            boost::beast::get_lowest_layer(stream_).expires_after(timeout_);
            stream_.async_shutdown(yield[error]);  // Close the SSL connection gracefully
        }
        boost::beast::get_lowest_layer(stream_).socket().shutdown(
            boost::asio::ip::tcp::socket::shutdown_type::shutdown_both, error
        );
    }

    std::expected<bool, Error>
    isUpgradeRequested(boost::asio::yield_context yield) override
    {
        auto expectedRequest = fetch(yield);
        if (not expectedRequest.has_value())
            return std::unexpected{std::move(expectedRequest).error()};

        request_ = std::move(expectedRequest).value();

        return boost::beast::websocket::is_upgrade(request_.value());
    }

    std::expected<ConnectionPtr, Error>
    upgrade(util::TagDecoratorFactory const& tagDecoratorFactory, boost::asio::yield_context yield) override
    {
        ASSERT(request_.has_value(), "Request must be present to upgrade the connection");

        return makeWsConnection(
            std::move(stream_),
            std::move(ip_),
            std::move(buffer_),
            std::move(request_).value(),
            tagDecoratorFactory,
            yield
        );
    }

private:
    std::expected<boost::beast::http::request<boost::beast::http::string_body>, Error>
    fetch(boost::asio::yield_context yield)
    {
        boost::beast::http::request<boost::beast::http::string_body> request{};
        boost::system::error_code error;
        boost::beast::get_lowest_layer(stream_).expires_after(timeout_);
        boost::beast::http::async_read(stream_, buffer_, request, yield[error]);
        if (error)
            return std::unexpected{error};
        return request;
    }
};

using PlainHttpConnection = HttpConnection<boost::beast::tcp_stream>;

using SslHttpConnection = HttpConnection<boost::asio::ssl::stream<boost::beast::tcp_stream>>;

}  // namespace web::ng::impl