//----------------------------------------------------------------------------- 
//     ___                      __ _       _
//    / _ \__ _ _ __ ___  ___  / /(_)_ __ | | __
//   / /_)/ _` | '__/ __|/ _ \/ / | | '_ \| |/ /
//  / ___/ (_| | |  \__ \  __/ /__| | | | |   <
//  \/    \__,_|_|  |___/\___\____/_|_| |_|_|\_\ .
//
//----------------------------------------------------------------------------- 
// Author: Kurt Sassenrath
// Module: Server
//
// Server implementation. Currently, a monolithic server which:
//     * Communicates with users via TCP (msgpack).
//     * Runs the websocket server for overlays to read.
//
// Copyright (c) 2023 Kurt Sassenrath.
//
// License TBD.
//----------------------------------------------------------------------------- 

#include "parselink/logging.h"
#include "parselink/server.h"

#include <boost/asio/io_context.hpp>
#include <boost/asio/signal_set.hpp>
#include <boost/asio/redirect_error.hpp>
#include <boost/asio/write.hpp>

#include <boost/asio/ip/address.hpp>
#include <boost/asio/ip/tcp.hpp>

#include <boost/asio/co_spawn.hpp>
#include <boost/asio/deferred.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/as_tuple.hpp>

using namespace parselink;

namespace net = boost::asio;
using net::co_spawn;
using net::awaitable;
using net::use_awaitable;
using net::deferred;
using net::detached;

//-----------------------------------------------------------------------------
// TODO(ksassenrath): These are logging formatters for various boost/asio types.
// Not all code is exposed to them, so they cannot be defined inside the
// generic logging/formatters.h header. They should go somewhere else.
//-----------------------------------------------------------------------------
template <>
struct parselink::logging::theme<boost::system::error_code>
        : parselink::logging::static_theme<fmt::color::fire_brick> {};

template <>
struct fmt::formatter<boost::system::error_code>
        : fmt::formatter<std::string_view> {
    template<typename FormatContext>
    constexpr auto format(auto const& v, FormatContext& ctx) const {
        return fmt::formatter<std::string_view>::format(v.message(), ctx);
    }
};

template <typename T>
concept endpoint = requires(T const& t) {
    {t.address()};
    {t.port()};
};

template <endpoint T>
struct parselink::logging::theme<T>
        : parselink::logging::static_theme<fmt::color::coral> {};

template <endpoint T>
struct fmt::formatter<T>
        : fmt::formatter<std::string_view> {
    template<typename FormatContext>
    constexpr auto format(auto const& v, FormatContext& ctx) const {
        return fmt::format_to(ctx.out(), "{}:{}", v.address().to_string(),
                v.port());
    }
};

//-----------------------------------------------------------------------------
// End formatters
//-----------------------------------------------------------------------------

namespace {
    logging::logger logger("server");
    constexpr auto no_ex_coro = net::as_tuple(use_awaitable);
    constexpr auto no_ex_defer = net::as_tuple(deferred);
}

class user_session : public std::enable_shared_from_this<user_session> {
public:
    user_session(net::ip::tcp::socket sock) : socket_(std::move(sock)) {}
    ~user_session() {
        logger.debug("Closing connection to {}", socket_.remote_endpoint());
    }

    void start() {
        logger.debug("New connection from {}", socket_.remote_endpoint());
        co_spawn(socket_.get_executor(), [self = shared_from_this()]{
            return self->reader();
        }, detached);
    }

    awaitable<void> reader() {
        std::array<std::byte, 4096> buffer;
        auto [ec, n] = co_await socket_.async_read_some(
                net::buffer(buffer), no_ex_coro);
        if (ec) {
            logger.error("Reading from user socket failed: {}", ec);
            co_return;
        }
        logger.info("Read {} bytes from client: {}", n,
                std::string_view(reinterpret_cast<char*>(buffer.data()), n));
    }

    enum class state {
        init,
        authenticated,
        active
    };

    net::ip::tcp::socket socket_;
};

class monolithic_server : public server {
public:
    monolithic_server(std::string_view address, std::uint16_t user_port,
            std::uint16_t websocket_port);

    std::error_code run() noexcept override;

private:

    awaitable<void> user_listen();

    net::io_context io_context_;
    net::ip::address addr_;
    std::uint16_t user_port_;
    std::uint16_t websocket_port_;
};


monolithic_server::monolithic_server(std::string_view address,
        std::uint16_t user_port, std::uint16_t websocket_port)
        : io_context_{1}
        , addr_(net::ip::address::from_string(std::string{address}))
        , user_port_{user_port}
        , websocket_port_{websocket_port} {
    logger.debug("Creating monolithic_server(address = {}, user_port = {}, "
            "websocket_port = {})", address, user_port_, websocket_port_);
}

awaitable<void> monolithic_server::user_listen() {
    auto exec = co_await net::this_coro::executor;
    net::ip::tcp::acceptor acceptor{exec, {addr_, user_port_}};
    while (true) {
        std::make_shared<user_session>(
                co_await acceptor.async_accept(use_awaitable))->start();
    }
}

std::error_code monolithic_server::run() noexcept {
    logger.info("Starting server.");

    net::signal_set signals(io_context_, SIGINT, SIGTERM);
    signals.async_wait([&](auto, auto){
        logger.info("Received signal... Shutting down.");
        io_context_.stop();
    });

    co_spawn(io_context_, user_listen(), detached);

    io_context_.run();

    return {};
}

std::unique_ptr<server> parselink::make_server(std::string_view address,
        std::uint16_t user_port, std::uint16_t websocket_port) {
    using impl = monolithic_server;
    return std::make_unique<impl>(address, user_port, websocket_port);
}