quic_server.cpp

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// BSD 3-Clause License
// Copyright (c) 2024, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#include <kcenon/network/detail/config/feature_flags.h>
 
#define NETWORK_USE_EXPERIMENTAL
#include "internal/experimental/quic_server.h"
 
#include "internal/integration/logger_integration.h"
#include "kcenon/network/detail/metrics/network_metrics.h"
#include "internal/protocols/quic/packet.h"
#include "kcenon/network/detail/session/quic_session.h"
#include "internal/quic_socket.h"
 
#include <random>
#include <sstream>
 
namespace kcenon::network::core
{
 
messaging_quic_server::messaging_quic_server(std::string_view server_id)
    : server_id_(server_id)
{
}
 
messaging_quic_server::~messaging_quic_server() noexcept
{
    if (lifecycle_.is_running())
    {
        (void)stop_server(); // Ignore result in destructor
    }
}
 
auto messaging_quic_server::server_id() const -> const std::string&
{
    return server_id_;
}
 
auto messaging_quic_server::is_running() const -> bool
{
    return lifecycle_.is_running();
}
 
auto messaging_quic_server::wait_for_stop() -> void
{
    lifecycle_.wait_for_stop();
}
 
auto messaging_quic_server::start_server(unsigned short port) -> VoidResult
{
    // Use default config with no TLS (for development/testing only)
    return start_server(port, quic_server_config{});
}
 
auto messaging_quic_server::start_server(unsigned short port,
                                         const quic_server_config& config)
    -> VoidResult
{
    if (lifecycle_.is_running())
    {
        return error_void(
            error_codes::network_system::server_already_running,
            "QUIC server is already running",
            "messaging_quic_server::start_server");
    }
 
    config_ = config;
    lifecycle_.set_running();
 
    auto result = do_start_impl(port);
    if (result.is_err())
    {
        lifecycle_.mark_stopped();
    }
 
    return result;
}
 
auto messaging_quic_server::stop_server() -> VoidResult
{
    if (!lifecycle_.is_running())
    {
        return error_void(
            error_codes::network_system::server_not_started,
            "QUIC server is not running",
            "messaging_quic_server::stop_server");
    }
 
    if (!lifecycle_.prepare_stop())
    {
        return error_void(
            error_codes::network_system::server_not_started,
            "QUIC server is already stopping",
            "messaging_quic_server::stop_server");
    }
 
    auto result = do_stop_impl();
    lifecycle_.mark_stopped();
 
    return result;
}
 
auto messaging_quic_server::start(uint16_t port) -> VoidResult
{
    return start_server(port);
}
 
auto messaging_quic_server::stop() -> VoidResult
{
    return stop_server();
}
 
auto messaging_quic_server::connection_count() const -> size_t
{
    return session_count();
}
 
auto messaging_quic_server::do_start_impl(unsigned short port) -> VoidResult
{
    try
    {
        // A previous bind failure can leave a work guard tied to the old
        // context. Destroy every dependent object before replacing it.
        if (io_context_)
        {
            auto cleanup = do_stop_impl();
            if (cleanup.is_err()) return cleanup;
        }
        // Create io_context
        io_context_ = std::make_unique<asio::io_context>();
        work_guard_ = std::make_unique<
            asio::executor_work_guard<asio::io_context::executor_type>>(
            asio::make_work_guard(*io_context_));
 
        // Create UDP socket
        udp_socket_ = std::make_unique<asio::ip::udp::socket>(
            *io_context_,
            asio::ip::udp::endpoint(asio::ip::udp::v4(), port));
 
        // Create cleanup timer
        cleanup_timer_ = std::make_unique<asio::steady_timer>(*io_context_);
 
        // Start receiving packets
        start_receive();
 
        // Start periodic cleanup timer
        start_cleanup_timer();
 
        // Get thread pool from network context
        thread_pool_ = network_context::instance().get_thread_pool();
        if (!thread_pool_)
        {
            thread_pool_ = std::make_shared<integration::basic_thread_pool>(2);
        }
 
        // Submit io_context run task to thread pool
        io_context_future_ = thread_pool_->submit(
            [this]()
            {
                try
                {
                    NETWORK_LOG_INFO(
                        "[messaging_quic_server] Starting io_context on thread pool");
                    io_context_->run();
                    NETWORK_LOG_INFO(
                        "[messaging_quic_server] io_context stopped");
                }
                catch (const std::exception& e)
                {
                    NETWORK_LOG_ERROR(
                        "[messaging_quic_server] Exception in io_context: "
                        + std::string(e.what()));
                }
            });
 
        NETWORK_LOG_INFO("[messaging_quic_server] Started listening on port "
                         + std::to_string(port));
        return ok();
    }
    catch (const std::system_error& e)
    {
        if (e.code() == asio::error::address_in_use ||
            e.code() == std::errc::address_in_use)
        {
            return error_void(error_codes::network_system::bind_failed,
                              "Failed to bind to port: address already in use",
                              "messaging_quic_server::do_start_impl",
                              "Port: " + std::to_string(port));
        }
        else if (e.code() == asio::error::access_denied ||
                 e.code() == std::errc::permission_denied)
        {
            return error_void(error_codes::network_system::bind_failed,
                              "Failed to bind to port: permission denied",
                              "messaging_quic_server::do_start_impl",
                              "Port: " + std::to_string(port));
        }
 
        return error_void(error_codes::common_errors::internal_error,
                          "Failed to start server: " + std::string(e.what()),
                          "messaging_quic_server::do_start_impl",
                          "Port: " + std::to_string(port));
    }
    catch (const std::exception& e)
    {
        return error_void(error_codes::common_errors::internal_error,
                          "Failed to start server: " + std::string(e.what()),
                          "messaging_quic_server::do_start_impl",
                          "Port: " + std::to_string(port));
    }
}
 
auto messaging_quic_server::do_stop_impl() -> VoidResult
{
    try
    {
        // Release work guard
        if (work_guard_)
        {
            work_guard_.reset();
        }
 
        // Stop io_context
        if (io_context_)
        {
            io_context_->stop();
        }
 
        // Wait for io_context task
        if (io_context_future_.valid())
        {
            io_context_future_.wait();
        }
 
        // The worker may rearm receives or the cleanup timer until run() exits.
        // Cancel and close their ASIO objects only after it has stopped.
        if (cleanup_timer_)
        {
            cleanup_timer_->cancel();
        }
 
        // Close UDP socket
        if (udp_socket_)
        {
            asio::error_code ec;
            udp_socket_->cancel(ec);
            if (udp_socket_->is_open())
            {
                udp_socket_->close(ec);
            }
        }
 
        // No receive handler can add another session after this point.
        // Close sessions while their socket and timer context still exists.
        disconnect_all(0);
 
        // Release resources
        udp_socket_.reset();
        cleanup_timer_.reset();
        thread_pool_.reset();
        io_context_.reset();
 
        NETWORK_LOG_INFO("[messaging_quic_server] Stopped.");
        return ok();
    }
    catch (const std::exception& e)
    {
        return error_void(error_codes::common_errors::internal_error,
                          "Failed to stop server: " + std::string(e.what()),
                          "messaging_quic_server::do_stop_impl",
                          "Server ID: " + server_id_);
    }
}
 
auto messaging_quic_server::sessions() const
    -> std::vector<std::shared_ptr<session::quic_session>>
{
    std::shared_lock<std::shared_mutex> lock(sessions_mutex_);
    std::vector<std::shared_ptr<session::quic_session>> result;
    result.reserve(sessions_.size());
    for (const auto& [id, session] : sessions_)
    {
        result.push_back(session);
    }
    return result;
}
 
auto messaging_quic_server::get_session(const std::string& session_id)
    -> std::shared_ptr<session::quic_session>
{
    std::shared_lock<std::shared_mutex> lock(sessions_mutex_);
    auto it = sessions_.find(session_id);
    if (it != sessions_.end())
    {
        return it->second;
    }
    return nullptr;
}
 
auto messaging_quic_server::session_count() const -> size_t
{
    std::shared_lock<std::shared_mutex> lock(sessions_mutex_);
    return sessions_.size();
}
 
auto messaging_quic_server::disconnect_session(const std::string& session_id,
                                               uint64_t error_code)
    -> VoidResult
{
    std::shared_ptr<session::quic_session> session;
    {
        std::unique_lock<std::shared_mutex> lock(sessions_mutex_);
        auto it = sessions_.find(session_id);
        if (it == sessions_.end())
        {
            return error_void(error_codes::common_errors::not_found,
                              "Session not found",
                              "messaging_quic_server::disconnect_session",
                              "Session ID: " + session_id);
        }
        session = it->second;
        sessions_.erase(it);
    }
 
    if (session)
    {
        return session->close(error_code);
    }
    return ok();
}
 
auto messaging_quic_server::disconnect_all(uint64_t error_code) -> void
{
    std::vector<std::shared_ptr<session::quic_session>> sessions_to_close;
    {
        std::unique_lock<std::shared_mutex> lock(sessions_mutex_);
        sessions_to_close.reserve(sessions_.size());
        for (auto& [id, session] : sessions_)
        {
            sessions_to_close.push_back(session);
        }
        sessions_.clear();
    }
 
    for (auto& session : sessions_to_close)
    {
        if (session)
        {
            auto result = session->close(error_code);
            (void)result;
        }
    }
}
 
auto messaging_quic_server::broadcast(std::vector<uint8_t>&& data)
    -> VoidResult
{
    auto sessions_list = sessions();
    for (auto& session : sessions_list)
    {
        if (session && session->is_active())
        {
            std::vector<uint8_t> data_copy(data);
            auto result = session->send(std::move(data_copy));
            if (result.is_err())
            {
                NETWORK_LOG_WARN("[messaging_quic_server] Failed to send to session "
                                 + session->session_id() + ": "
                                 + result.error().message);
            }
        }
    }
    return ok();
}
 
auto messaging_quic_server::multicast(
    const std::vector<std::string>& session_ids,
    std::vector<uint8_t>&& data) -> VoidResult
{
    for (const auto& session_id : session_ids)
    {
        auto session = get_session(session_id);
        if (session && session->is_active())
        {
            std::vector<uint8_t> data_copy(data);
            auto result = session->send(std::move(data_copy));
            if (result.is_err())
            {
                NETWORK_LOG_WARN("[messaging_quic_server] Failed to send to session "
                                 + session_id + ": " + result.error().message);
            }
        }
    }
    return ok();
}
 
#if KCENON_WITH_COMMON_SYSTEM
auto messaging_quic_server::set_monitor(
    kcenon::common::interfaces::IMonitor* monitor) -> void
{
    monitor_ = monitor;
}
 
auto messaging_quic_server::get_monitor() const
    -> kcenon::common::interfaces::IMonitor*
{
    return monitor_;
}
#endif
 
auto messaging_quic_server::start_receive() -> void
{
    if (!is_running() || !udp_socket_)
    {
        return;
    }
 
    auto self = shared_from_this();
    udp_socket_->async_receive_from(
        asio::buffer(recv_buffer_),
        recv_endpoint_,
        [this, self](std::error_code ec, std::size_t bytes_received)
        {
            if (!is_running())
            {
                return;
            }
 
            if (ec)
            {
                if (ec != asio::error::operation_aborted)
                {
                    NETWORK_LOG_ERROR(
                        "[messaging_quic_server] Receive error: " + ec.message());
 
                    invoke_error_callback(ec);
                }
                return;
            }
 
            // Handle the received packet
            std::span<const uint8_t> packet_data(recv_buffer_.data(),
                                                 bytes_received);
            handle_packet(packet_data, recv_endpoint_);
 
            // Continue receiving
            start_receive();
        });
}
 
auto messaging_quic_server::handle_packet(std::span<const uint8_t> data,
                                          const asio::ip::udp::endpoint& from)
    -> void
{
    if (data.empty())
    {
        return;
    }
 
    // Parse packet header to get destination connection ID
    auto header_result = protocols::quic::packet_parser::parse_header(data);
    if (header_result.is_err())
    {
        NETWORK_LOG_DEBUG("[messaging_quic_server] Invalid packet from "
                          + from.address().to_string());
        return;
    }
 
    // Extract destination connection ID from header
    protocols::quic::connection_id dcid;
    std::visit(
        [&dcid](auto&& hdr)
        {
            dcid = hdr.dest_conn_id;
        },
        header_result.value().first);
 
    // Find or create session for this connection
    auto session = find_or_create_session(dcid, from);
    if (!session)
    {
        NETWORK_LOG_DEBUG(
            "[messaging_quic_server] Could not find or create session for packet");
        return;
    }
 
    // Delegate packet handling to session
    session->handle_packet(data);
}
 
auto messaging_quic_server::find_or_create_session(
    const protocols::quic::connection_id& dcid,
    const asio::ip::udp::endpoint& endpoint)
    -> std::shared_ptr<session::quic_session>
{
    // First, check existing sessions
    {
        std::shared_lock<std::shared_mutex> lock(sessions_mutex_);
        for (const auto& [id, session] : sessions_)
        {
            if (session->matches_connection_id(dcid))
            {
                return session;
            }
        }
    }
 
    // Check connection limit
    if (session_count() >= config_.max_connections)
    {
        NETWORK_LOG_WARN(
            "[messaging_quic_server] Connection limit reached, rejecting new connection");
        return nullptr;
    }
 
    // Create new session for this connection
    auto session_id = generate_session_id();
 
    // Create QUIC socket for the new session
    asio::ip::udp::socket session_socket(
        *io_context_, asio::ip::udp::endpoint(asio::ip::udp::v4(), 0));
    session_socket.connect(endpoint);
 
    auto quic_socket = std::make_shared<internal::quic_socket>(
        std::move(session_socket), internal::quic_role::server);
 
    // Accept the connection with TLS config
    if (!config_.cert_file.empty() && !config_.key_file.empty())
    {
        auto accept_result =
            quic_socket->accept(config_.cert_file, config_.key_file);
        if (accept_result.is_err())
        {
            NETWORK_LOG_ERROR(
                "[messaging_quic_server] Failed to accept connection: "
                + accept_result.error().message);
            return nullptr;
        }
    }
 
    auto session =
        std::make_shared<session::quic_session>(quic_socket, session_id);
 
    // Set up session callbacks
    auto self = weak_from_this();
 
    session->set_receive_callback(
        [self, session_id](const std::vector<uint8_t>& data)
        {
            if (auto server = self.lock())
            {
                auto sess = server->get_session(session_id);
                if (sess)
                {
                    server->invoke_receive_callback(sess, data);
                }
            }
        });
 
    session->set_stream_receive_callback(
        [self, session_id](uint64_t stream_id,
                           const std::vector<uint8_t>& data,
                           bool fin)
        {
            if (auto server = self.lock())
            {
                auto sess = server->get_session(session_id);
                if (sess)
                {
                    server->invoke_stream_receive_callback(sess, stream_id, data, fin);
                }
            }
        });
 
    session->set_close_callback(
        [self, session_id]()
        {
            if (auto server = self.lock())
            {
                server->on_session_close(session_id);
            }
        });
 
    // Add session to map
    {
        std::unique_lock<std::shared_mutex> lock(sessions_mutex_);
        sessions_[session_id] = session;
    }
 
    // Start the session
    session->start_session();
 
    // Report metrics
    metrics::metric_reporter::report_connection_accepted();
    metrics::metric_reporter::report_active_connections(session_count());
 
    // Invoke connection callback
    invoke_connection_callback(session);
 
#if KCENON_WITH_COMMON_SYSTEM
    if (monitor_)
    {
        monitor_->record_metric("active_connections",
                                static_cast<double>(session_count()));
    }
#endif
 
    NETWORK_LOG_INFO("[messaging_quic_server] New session created: "
                     + session_id + " from " + endpoint.address().to_string());
 
    return session;
}
 
auto messaging_quic_server::generate_session_id() -> std::string
{
    auto counter = session_counter_.fetch_add(1);
    std::ostringstream oss;
    oss << server_id_ << "-" << counter;
    return oss.str();
}
 
auto messaging_quic_server::on_session_close(const std::string& session_id)
    -> void
{
    std::shared_ptr<session::quic_session> session;
    {
        std::unique_lock<std::shared_mutex> lock(sessions_mutex_);
        auto it = sessions_.find(session_id);
        if (it != sessions_.end())
        {
            session = it->second;
            sessions_.erase(it);
        }
    }
 
    if (session)
    {
        // Report metrics
        metrics::metric_reporter::report_active_connections(session_count());
 
        // Invoke disconnection callback
        invoke_disconnection_callback(session);
 
#if KCENON_WITH_COMMON_SYSTEM
        if (monitor_)
        {
            monitor_->record_metric("active_connections",
                                    static_cast<double>(session_count()));
        }
#endif
 
        NETWORK_LOG_INFO("[messaging_quic_server] Session closed: "
                         + session_id);
    }
}
 
auto messaging_quic_server::start_cleanup_timer() -> void
{
    if (!cleanup_timer_ || !is_running())
    {
        return;
    }
 
    // Schedule cleanup every 30 seconds
    cleanup_timer_->expires_after(std::chrono::seconds(30));
 
    auto self = shared_from_this();
    cleanup_timer_->async_wait(
        [this, self](const std::error_code& ec)
        {
            if (!ec && is_running())
            {
                cleanup_dead_sessions();
                start_cleanup_timer(); // Reschedule
            }
        });
}
 
auto messaging_quic_server::cleanup_dead_sessions() -> void
{
    std::vector<std::string> dead_session_ids;
 
    {
        std::shared_lock<std::shared_mutex> lock(sessions_mutex_);
        for (const auto& [id, session] : sessions_)
        {
            if (!session || !session->is_active())
            {
                dead_session_ids.push_back(id);
            }
        }
    }
 
    for (const auto& id : dead_session_ids)
    {
        on_session_close(id);
    }
 
    if (!dead_session_ids.empty())
    {
        NETWORK_LOG_DEBUG(
            "[messaging_quic_server] Cleaned up "
            + std::to_string(dead_session_ids.size())
            + " dead sessions. Active: " + std::to_string(session_count()));
    }
}
 
// =============================================================================
// Callback invocation helpers
// =============================================================================
 
auto messaging_quic_server::invoke_connection_callback(
    std::shared_ptr<session::quic_session> session) -> void
{
    callbacks_.invoke<to_index(callback_index::connection)>(session);
}
 
auto messaging_quic_server::invoke_disconnection_callback(
    std::shared_ptr<session::quic_session> session) -> void
{
    callbacks_.invoke<to_index(callback_index::disconnection)>(session);
}
 
auto messaging_quic_server::invoke_receive_callback(
    std::shared_ptr<session::quic_session> session,
    const std::vector<uint8_t>& data) -> void
{
    callbacks_.invoke<to_index(callback_index::receive)>(session, data);
}
 
auto messaging_quic_server::invoke_stream_receive_callback(
    std::shared_ptr<session::quic_session> session,
    uint64_t stream_id,
    const std::vector<uint8_t>& data,
    bool fin) -> void
{
    callbacks_.invoke<to_index(callback_index::stream_receive)>(session, stream_id, data, fin);
}
 
auto messaging_quic_server::invoke_error_callback(std::error_code ec) -> void
{
    callbacks_.invoke<to_index(callback_index::error)>(ec);
}
 
// =============================================================================
// Legacy callback setters
// =============================================================================
 
auto messaging_quic_server::set_connection_callback(connection_callback_t callback) -> void
{
    callbacks_.set<to_index(callback_index::connection)>(std::move(callback));
}
 
auto messaging_quic_server::set_disconnection_callback(disconnection_callback_t callback) -> void
{
    callbacks_.set<to_index(callback_index::disconnection)>(std::move(callback));
}
 
auto messaging_quic_server::set_receive_callback(receive_callback_t callback) -> void
{
    callbacks_.set<to_index(callback_index::receive)>(std::move(callback));
}
 
auto messaging_quic_server::set_stream_receive_callback(stream_receive_callback_t callback) -> void
{
    callbacks_.set<to_index(callback_index::stream_receive)>(std::move(callback));
}
 
auto messaging_quic_server::set_error_callback(error_callback_t callback) -> void
{
    callbacks_.set<to_index(callback_index::error)>(std::move(callback));
}
 
// =============================================================================
// i_quic_server interface callback implementations
// =============================================================================
 
auto messaging_quic_server::set_connection_callback(
    interfaces::i_quic_server::connection_callback_t callback) -> void
{
    // Convert callback to internal type (quic_session to i_quic_session)
    set_connection_callback(
        [cb = std::move(callback)](std::shared_ptr<session::quic_session> session) {
            if (cb && session)
            {
                // quic_session implements i_quic_session, so we can pass it directly
                cb(session);
            }
        });
}
 
auto messaging_quic_server::set_disconnection_callback(
    interfaces::i_quic_server::disconnection_callback_t callback) -> void
{
    set_disconnection_callback(
        [cb = std::move(callback)](std::shared_ptr<session::quic_session> session) {
            if (cb && session)
            {
                cb(session->session_id());
            }
        });
}
 
auto messaging_quic_server::set_receive_callback(
    interfaces::i_quic_server::receive_callback_t callback) -> void
{
    set_receive_callback(
        [cb = std::move(callback)](std::shared_ptr<session::quic_session> session,
                                    const std::vector<uint8_t>& data) {
            if (cb && session)
            {
                cb(session->session_id(), data);
            }
        });
}
 
auto messaging_quic_server::set_stream_callback(
    interfaces::i_quic_server::stream_callback_t callback) -> void
{
    set_stream_receive_callback(
        [cb = std::move(callback)](std::shared_ptr<session::quic_session> session,
                                    uint64_t stream_id,
                                    const std::vector<uint8_t>& data,
                                    bool fin) {
            if (cb && session)
            {
                cb(session->session_id(), stream_id, data, fin);
            }
        });
}
 
auto messaging_quic_server::set_error_callback(
    interfaces::i_quic_server::error_callback_t callback) -> void
{
    // Store the interface callback and wrap it for base class
    // Note: Base class error_callback_t only takes error_code, not session
    // We need to store the interface callback separately and invoke it from
    // the receive side where we have session context
    interface_error_cb_ = std::move(callback);
}
 
} // namespace kcenon::network::core