http2_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 "internal/protocols/http2/http2_server.h"
 
#include <algorithm>
#include <stdexcept>
 
namespace kcenon::network::protocols::http2
{
    // =========================================================================
    // http2_server implementation
    // =========================================================================
 
    http2_server::http2_server(std::string_view server_id)
        : server_id_(server_id)
        , stop_future_(stop_promise_.get_future())
        , encoder_(std::make_shared<hpack_encoder>(settings_.header_table_size))
        , decoder_(std::make_shared<hpack_decoder>(settings_.header_table_size))
    {
    }
 
    http2_server::~http2_server()
    {
        if (is_running_) {
            stop();
        }
    }
 
    auto http2_server::start(unsigned short port) -> VoidResult
    {
        if (is_running_) {
            return error_void(
                error_codes::common_errors::already_exists,
                "Server already running",
                "http2_server");
        }
 
        try {
            io_context_ = std::make_unique<asio::io_context>();
            work_guard_ = std::make_unique<asio::executor_work_guard<asio::io_context::executor_type>>(
                io_context_->get_executor());
 
            acceptor_ = std::make_unique<asio::ip::tcp::acceptor>(
                *io_context_,
                asio::ip::tcp::endpoint(asio::ip::tcp::v4(), port));
 
            use_tls_ = false;
            is_running_ = true;
 
            // Start I/O thread
            io_future_ = std::async(std::launch::async, [this]() { run_io(); });
 
            // Start accepting connections
            do_accept();
            start_cleanup_timer();
 
            return ok();
        } catch (const std::exception& e) {
            return error_void(
                error_codes::network_system::bind_failed,
                std::string("Failed to start server: ") + e.what(),
                "http2_server");
        }
    }
 
    auto http2_server::start_tls(unsigned short port, const tls_config& config) -> VoidResult
    {
        if (is_running_) {
            return error_void(
                error_codes::common_errors::already_exists,
                "Server already running",
                "http2_server");
        }
 
        try {
            io_context_ = std::make_unique<asio::io_context>();
            work_guard_ = std::make_unique<asio::executor_work_guard<asio::io_context::executor_type>>(
                io_context_->get_executor());
 
            // Setup TLS context
            ssl_context_ = std::make_unique<asio::ssl::context>(asio::ssl::context::tls_server);
            ssl_context_->set_options(
                asio::ssl::context::default_workarounds |
                asio::ssl::context::no_sslv2 |
                asio::ssl::context::no_sslv3 |
                asio::ssl::context::no_tlsv1 |
                asio::ssl::context::no_tlsv1_1);
 
            ssl_context_->use_certificate_file(config.cert_file, asio::ssl::context::pem);
            ssl_context_->use_private_key_file(config.key_file, asio::ssl::context::pem);
 
            if (!config.ca_file.empty()) {
                ssl_context_->load_verify_file(config.ca_file);
            }
 
            if (config.verify_client) {
                ssl_context_->set_verify_mode(asio::ssl::verify_peer | asio::ssl::verify_fail_if_no_peer_cert);
            }
 
            // Set ALPN callback for HTTP/2
            SSL_CTX_set_alpn_select_cb(
                ssl_context_->native_handle(),
                [](SSL* /*ssl*/, const unsigned char** out, unsigned char* outlen,
                   const unsigned char* in, unsigned int inlen, void* /*arg*/) -> int {
                    // Look for "h2" in client's ALPN list
                    const unsigned char* client = in;
                    const unsigned char* end = in + inlen;
                    while (client < end) {
                        unsigned char len = *client++;
                        if (len == 2 && client + 2 <= end &&
                            client[0] == 'h' && client[1] == '2') {
                            *out = client;
                            *outlen = 2;
                            return SSL_TLSEXT_ERR_OK;
                        }
                        client += len;
                    }
                    return SSL_TLSEXT_ERR_NOACK;
                },
                nullptr);
 
            acceptor_ = std::make_unique<asio::ip::tcp::acceptor>(
                *io_context_,
                asio::ip::tcp::endpoint(asio::ip::tcp::v4(), port));
 
            use_tls_ = true;
            is_running_ = true;
 
            // Start I/O thread
            io_future_ = std::async(std::launch::async, [this]() { run_io(); });
 
            // Start accepting connections
            do_accept_tls();
            start_cleanup_timer();
 
            return ok();
        } catch (const std::exception& e) {
            return error_void(
                error_codes::network_system::bind_failed,
                std::string("Failed to start TLS server: ") + e.what(),
                "http2_server");
        }
    }
 
    auto http2_server::stop() -> VoidResult
    {
        if (!is_running_) {
            return ok();
        }
 
        is_running_ = false;
 
        // Close acceptor
        if (acceptor_ && acceptor_->is_open()) {
            std::error_code ec;
            acceptor_->close(ec);
        }
 
        // Stop all connections
        {
            std::lock_guard<std::mutex> lock(connections_mutex_);
            for (auto& [id, conn] : connections_) {
                conn->stop();
            }
            connections_.clear();
        }
 
        // Stop cleanup timer
        if (cleanup_timer_) {
            cleanup_timer_->cancel();
        }
 
        stop_io();
 
        // Signal stop
        try {
            stop_promise_.set_value();
        } catch (...) {
            // Already set
        }
 
        return ok();
    }
 
    auto http2_server::is_running() const -> bool
    {
        return is_running_;
    }
 
    auto http2_server::wait() -> void
    {
        stop_future_.wait();
    }
 
    auto http2_server::set_request_handler(request_handler_t handler) -> void
    {
        request_handler_ = std::move(handler);
    }
 
    auto http2_server::set_error_handler(error_handler_t handler) -> void
    {
        error_handler_ = std::move(handler);
    }
 
    auto http2_server::set_settings(const http2_settings& settings) -> void
    {
        settings_ = settings;
        encoder_->set_max_table_size(settings.header_table_size);
        decoder_->set_max_table_size(settings.header_table_size);
    }
 
    auto http2_server::get_settings() const -> http2_settings
    {
        return settings_;
    }
 
    auto http2_server::active_connections() const -> size_t
    {
        std::lock_guard<std::mutex> lock(const_cast<std::mutex&>(connections_mutex_));
        return connections_.size();
    }
 
    auto http2_server::active_streams() const -> size_t
    {
        std::lock_guard<std::mutex> lock(const_cast<std::mutex&>(connections_mutex_));
        size_t total = 0;
        for (const auto& [id, conn] : connections_) {
            total += conn->stream_count();
        }
        return total;
    }
 
    auto http2_server::server_id() const -> std::string_view
    {
        return server_id_;
    }
 
    auto http2_server::do_accept() -> void
    {
        if (!is_running_ || !acceptor_) {
            return;
        }
 
        acceptor_->async_accept(
            [this](std::error_code ec, asio::ip::tcp::socket socket) {
                handle_accept(ec, std::move(socket));
            });
    }
 
    auto http2_server::do_accept_tls() -> void
    {
        if (!is_running_ || !acceptor_) {
            return;
        }
 
        acceptor_->async_accept(
            [this](std::error_code ec, asio::ip::tcp::socket socket) {
                handle_accept_tls(ec, std::move(socket));
            });
    }
 
    auto http2_server::handle_accept(std::error_code ec, asio::ip::tcp::socket socket) -> void
    {
        if (!is_running_) {
            return;
        }
 
        if (ec) {
            if (error_handler_) {
                error_handler_(std::string("Accept error: ") + ec.message());
            }
        } else {
            uint64_t conn_id = next_connection_id_++;
            auto conn = std::make_shared<http2_server_connection>(
                conn_id,
                std::move(socket),
                settings_,
                request_handler_,
                error_handler_);
 
            add_connection(conn);
            conn->start();
        }
 
        // Continue accepting
        do_accept();
    }
 
    auto http2_server::handle_accept_tls(std::error_code ec, asio::ip::tcp::socket socket) -> void
    {
        if (!is_running_) {
            return;
        }
 
        if (ec) {
            if (error_handler_) {
                error_handler_(std::string("Accept error: ") + ec.message());
            }
            do_accept_tls();
            return;
        }
 
        auto tls_socket = std::make_unique<asio::ssl::stream<asio::ip::tcp::socket>>(
            std::move(socket), *ssl_context_);
 
        auto* raw_socket = tls_socket.get();
        raw_socket->async_handshake(
            asio::ssl::stream_base::server,
            [this, tls_socket = std::move(tls_socket)](std::error_code ec) mutable {
                if (ec) {
                    if (error_handler_) {
                        error_handler_(std::string("TLS handshake error: ") + ec.message());
                    }
                } else {
                    uint64_t conn_id = next_connection_id_++;
                    auto conn = std::make_shared<http2_server_connection>(
                        conn_id,
                        std::move(tls_socket),
                        settings_,
                        request_handler_,
                        error_handler_);
 
                    add_connection(conn);
                    conn->start();
                }
 
                // Continue accepting
                do_accept_tls();
            });
    }
 
    auto http2_server::add_connection(std::shared_ptr<http2_server_connection> conn) -> void
    {
        std::lock_guard<std::mutex> lock(connections_mutex_);
        connections_[conn->connection_id()] = std::move(conn);
    }
 
    auto http2_server::remove_connection(uint64_t connection_id) -> void
    {
        std::lock_guard<std::mutex> lock(connections_mutex_);
        connections_.erase(connection_id);
    }
 
    auto http2_server::cleanup_dead_connections() -> void
    {
        std::lock_guard<std::mutex> lock(connections_mutex_);
        for (auto it = connections_.begin(); it != connections_.end();) {
            if (!it->second->is_alive()) {
                it = connections_.erase(it);
            } else {
                ++it;
            }
        }
    }
 
    auto http2_server::start_cleanup_timer() -> void
    {
        if (!io_context_) {
            return;
        }
 
        cleanup_timer_ = std::make_unique<asio::steady_timer>(*io_context_);
        cleanup_timer_->expires_after(std::chrono::seconds(30));
        cleanup_timer_->async_wait([this](std::error_code ec) {
            if (!ec && is_running_) {
                cleanup_dead_connections();
                start_cleanup_timer();
            }
        });
    }
 
    auto http2_server::run_io() -> void
    {
        if (io_context_) {
            io_context_->run();
        }
    }
 
    auto http2_server::stop_io() -> void
    {
        if (work_guard_) {
            work_guard_.reset();
        }
 
        if (io_context_) {
            io_context_->stop();
        }
 
        if (io_future_.valid()) {
            io_future_.wait();
        }
    }
 
    // =========================================================================
    // http2_server_connection implementation
    // =========================================================================
 
    http2_server_connection::http2_server_connection(
        uint64_t connection_id,
        asio::ip::tcp::socket socket,
        const http2_settings& settings,
        http2_server::request_handler_t request_handler,
        http2_server::error_handler_t error_handler)
        : connection_id_(connection_id)
        , use_tls_(false)
        , plain_socket_(std::make_unique<asio::ip::tcp::socket>(std::move(socket)))
        , local_settings_(settings)
        , encoder_(settings.header_table_size)
        , decoder_(settings.header_table_size)
        , request_handler_(std::move(request_handler))
        , error_handler_(std::move(error_handler))
        , frame_header_buffer_{}
    {
    }
 
    http2_server_connection::http2_server_connection(
        uint64_t connection_id,
        std::unique_ptr<asio::ssl::stream<asio::ip::tcp::socket>> socket,
        const http2_settings& settings,
        http2_server::request_handler_t request_handler,
        http2_server::error_handler_t error_handler)
        : connection_id_(connection_id)
        , use_tls_(true)
        , tls_socket_(std::move(socket))
        , local_settings_(settings)
        , encoder_(settings.header_table_size)
        , decoder_(settings.header_table_size)
        , request_handler_(std::move(request_handler))
        , error_handler_(std::move(error_handler))
        , frame_header_buffer_{}
    {
    }
 
    http2_server_connection::~http2_server_connection()
    {
        stop();
    }
 
    auto http2_server_connection::start() -> VoidResult
    {
        // Read connection preface from client
        read_connection_preface();
        return ok();
    }
 
    auto http2_server_connection::stop() -> VoidResult
    {
        if (!is_alive_) {
            return ok();
        }
 
        is_alive_ = false;
 
        // Close socket
        std::error_code ec;
        if (use_tls_ && tls_socket_) {
            tls_socket_->lowest_layer().close(ec);
        } else if (plain_socket_) {
            plain_socket_->close(ec);
        }
 
        return ok();
    }
 
    auto http2_server_connection::is_alive() const -> bool
    {
        return is_alive_;
    }
 
    auto http2_server_connection::connection_id() const -> uint64_t
    {
        return connection_id_;
    }
 
    auto http2_server_connection::stream_count() const -> size_t
    {
        std::lock_guard<std::mutex> lock(const_cast<std::mutex&>(streams_mutex_));
        return streams_.size();
    }
 
    auto http2_server_connection::read_connection_preface() -> void
    {
        constexpr size_t PREFACE_SIZE = 24; // "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
        auto buffer = std::make_shared<std::vector<uint8_t>>(PREFACE_SIZE);
 
        auto read_handler = [this, buffer](std::error_code ec, std::size_t bytes_read) {
            if (ec || bytes_read != 24) {
                if (error_handler_) {
                    error_handler_("Failed to read connection preface");
                }
                stop();
                return;
            }
 
            // Verify preface
            const std::string expected = "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n";
            if (std::string(buffer->begin(), buffer->end()) != expected) {
                if (error_handler_) {
                    error_handler_("Invalid connection preface");
                }
                stop();
                return;
            }
 
            preface_received_ = true;
 
            // Send our SETTINGS frame
            auto result = send_settings();
            if (result.is_err()) {
                if (error_handler_) {
                    error_handler_("Failed to send settings");
                }
                stop();
                return;
            }
 
            // Start reading frames
            start_reading();
        };
 
        if (use_tls_) {
            asio::async_read(*tls_socket_, asio::buffer(*buffer), read_handler);
        } else {
            asio::async_read(*plain_socket_, asio::buffer(*buffer), read_handler);
        }
    }
 
    auto http2_server_connection::send_settings() -> VoidResult
    {
        std::vector<setting_parameter> params = {
            {static_cast<uint16_t>(setting_identifier::max_concurrent_streams),
             local_settings_.max_concurrent_streams},
            {static_cast<uint16_t>(setting_identifier::initial_window_size),
             local_settings_.initial_window_size},
            {static_cast<uint16_t>(setting_identifier::max_frame_size),
             local_settings_.max_frame_size},
            {static_cast<uint16_t>(setting_identifier::header_table_size),
             local_settings_.header_table_size},
        };
 
        settings_frame frame(params, false);
        return send_frame(frame);
    }
 
    auto http2_server_connection::handle_settings_frame(const settings_frame& frame) -> VoidResult
    {
        if (frame.is_ack()) {
            // Settings acknowledgment received
            return ok();
        }
 
        // Apply peer settings
        for (const auto& param : frame.settings()) {
            switch (static_cast<setting_identifier>(param.identifier)) {
                case setting_identifier::header_table_size:
                    remote_settings_.header_table_size = param.value;
                    encoder_.set_max_table_size(param.value);
                    break;
                case setting_identifier::enable_push:
                    remote_settings_.enable_push = (param.value != 0);
                    break;
                case setting_identifier::max_concurrent_streams:
                    remote_settings_.max_concurrent_streams = param.value;
                    break;
                case setting_identifier::initial_window_size:
                    remote_settings_.initial_window_size = param.value;
                    break;
                case setting_identifier::max_frame_size:
                    remote_settings_.max_frame_size = param.value;
                    break;
                case setting_identifier::max_header_list_size:
                    remote_settings_.max_header_list_size = param.value;
                    break;
            }
        }
 
        // Send ACK
        return send_settings_ack();
    }
 
    auto http2_server_connection::send_settings_ack() -> VoidResult
    {
        settings_frame frame({}, true);
        return send_frame(frame);
    }
 
    auto http2_server_connection::start_reading() -> void
    {
        read_frame_header();
    }
 
    auto http2_server_connection::read_frame_header() -> void
    {
        if (!is_alive_) {
            return;
        }
 
        auto read_handler = [this](std::error_code ec, std::size_t bytes_read) {
            if (ec || bytes_read != 9) {
                if (ec != asio::error::eof && ec != asio::error::operation_aborted) {
                    if (error_handler_) {
                        error_handler_(std::string("Read error: ") + ec.message());
                    }
                }
                stop();
                return;
            }
 
            auto header_result = frame_header::parse(frame_header_buffer_);
            if (header_result.is_err()) {
                if (error_handler_) {
                    error_handler_("Failed to parse frame header");
                }
                stop();
                return;
            }
 
            auto header = header_result.value();
            if (header.length > 0) {
                read_frame_payload(header.length);
            } else {
                // Process frame with empty payload
                auto frame_result = frame::parse(frame_header_buffer_);
                if (frame_result.is_ok()) {
                    process_frame(std::move(frame_result.value()));
                }
                read_frame_header();
            }
        };
 
        if (use_tls_) {
            asio::async_read(*tls_socket_, asio::buffer(frame_header_buffer_), read_handler);
        } else {
            asio::async_read(*plain_socket_, asio::buffer(frame_header_buffer_), read_handler);
        }
    }
 
    auto http2_server_connection::read_frame_payload(uint32_t length) -> void
    {
        if (!is_alive_) {
            return;
        }
 
        read_buffer_.resize(9 + length);
        std::copy(frame_header_buffer_.begin(), frame_header_buffer_.end(), read_buffer_.begin());
 
        auto payload_buffer = asio::buffer(read_buffer_.data() + 9, length);
 
        auto read_handler = [this](std::error_code ec, std::size_t /*bytes_read*/) {
            if (ec) {
                if (ec != asio::error::eof && ec != asio::error::operation_aborted) {
                    if (error_handler_) {
                        error_handler_(std::string("Read payload error: ") + ec.message());
                    }
                }
                stop();
                return;
            }
 
            auto frame_result = frame::parse(read_buffer_);
            if (frame_result.is_ok()) {
                process_frame(std::move(frame_result.value()));
            } else {
                if (error_handler_) {
                    error_handler_("Failed to parse frame");
                }
            }
 
            read_frame_header();
        };
 
        if (use_tls_) {
            asio::async_read(*tls_socket_, payload_buffer, read_handler);
        } else {
            asio::async_read(*plain_socket_, payload_buffer, read_handler);
        }
    }
 
    auto http2_server_connection::send_frame(const frame& f) -> VoidResult
    {
        auto data = f.serialize();
 
        std::error_code ec;
        if (use_tls_) {
            asio::write(*tls_socket_, asio::buffer(data), ec);
        } else {
            asio::write(*plain_socket_, asio::buffer(data), ec);
        }
 
        if (ec) {
            return error_void(
                error_codes::network_system::send_failed,
                std::string("Failed to send frame: ") + ec.message(),
                "http2_server_connection");
        }
 
        return ok();
    }
 
    auto http2_server_connection::process_frame(std::unique_ptr<frame> f) -> VoidResult
    {
        auto& header = f->header();
 
        switch (header.type) {
            case frame_type::settings: {
                auto* settings_f = dynamic_cast<settings_frame*>(f.get());
                if (settings_f) {
                    return handle_settings_frame(*settings_f);
                }
                break;
            }
            case frame_type::headers: {
                auto* headers_f = dynamic_cast<headers_frame*>(f.get());
                if (headers_f) {
                    return handle_headers_frame(*headers_f);
                }
                break;
            }
            case frame_type::data: {
                auto* data_f = dynamic_cast<data_frame*>(f.get());
                if (data_f) {
                    return handle_data_frame(*data_f);
                }
                break;
            }
            case frame_type::rst_stream: {
                auto* rst_f = dynamic_cast<rst_stream_frame*>(f.get());
                if (rst_f) {
                    return handle_rst_stream_frame(*rst_f);
                }
                break;
            }
            case frame_type::ping: {
                auto* ping_f = dynamic_cast<ping_frame*>(f.get());
                if (ping_f) {
                    return handle_ping_frame(*ping_f);
                }
                break;
            }
            case frame_type::goaway: {
                auto* goaway_f = dynamic_cast<goaway_frame*>(f.get());
                if (goaway_f) {
                    return handle_goaway_frame(*goaway_f);
                }
                break;
            }
            case frame_type::window_update: {
                auto* wu_f = dynamic_cast<window_update_frame*>(f.get());
                if (wu_f) {
                    return handle_window_update_frame(*wu_f);
                }
                break;
            }
            default:
                // Ignore unknown frame types
                break;
        }
 
        return ok();
    }
 
    auto http2_server_connection::get_or_create_stream(uint32_t stream_id) -> http2_stream*
    {
        std::lock_guard<std::mutex> lock(streams_mutex_);
 
        auto it = streams_.find(stream_id);
        if (it != streams_.end()) {
            return &it->second;
        }
 
        // Create new stream
        http2_stream stream;
        stream.stream_id = stream_id;
        stream.state = stream_state::open;
        stream.window_size = static_cast<int32_t>(local_settings_.initial_window_size);
 
        auto [iter, inserted] = streams_.emplace(stream_id, std::move(stream));
        if (stream_id > last_stream_id_) {
            last_stream_id_ = stream_id;
        }
 
        return &iter->second;
    }
 
    auto http2_server_connection::close_stream(uint32_t stream_id) -> void
    {
        std::lock_guard<std::mutex> lock(streams_mutex_);
        streams_.erase(stream_id);
    }
 
    auto http2_server_connection::handle_headers_frame(const headers_frame& f) -> VoidResult
    {
        uint32_t stream_id = f.header().stream_id;
        auto* stream = get_or_create_stream(stream_id);
 
        if (!stream) {
            return error_void(
                error_codes::common_errors::internal_error,
                "Failed to create stream",
                "http2_server_connection");
        }
 
        // Decode headers
        auto header_block = f.header_block();
        std::vector<uint8_t> block_data(header_block.begin(), header_block.end());
        auto headers_result = decoder_.decode(block_data);
 
        if (headers_result.is_err()) {
            // Send GOAWAY with COMPRESSION_ERROR
            goaway_frame goaway(last_stream_id_,
                static_cast<uint32_t>(error_code::compression_error));
            send_frame(goaway);
            stop();
            return error_void(
                headers_result.error().code,
                headers_result.error().message,
                "http2_server_connection");
        }
 
        stream->request_headers = headers_result.value();
 
        if (f.is_end_stream()) {
            stream->state = stream_state::half_closed_remote;
            dispatch_request(stream_id);
        } else if (f.is_end_headers()) {
            stream->headers_complete = true;
        }
 
        return ok();
    }
 
    auto http2_server_connection::handle_data_frame(const data_frame& f) -> VoidResult
    {
        uint32_t stream_id = f.header().stream_id;
 
        std::lock_guard<std::mutex> lock(streams_mutex_);
        auto it = streams_.find(stream_id);
        if (it == streams_.end()) {
            // Stream doesn't exist
            rst_stream_frame rst(stream_id, static_cast<uint32_t>(error_code::stream_closed));
            return send_frame(rst);
        }
 
        auto& stream = it->second;
        auto data = f.data();
        stream.request_body.insert(stream.request_body.end(), data.begin(), data.end());
 
        // Send WINDOW_UPDATE if needed
        size_t data_size = data.size();
        if (data_size > 0) {
            // Update connection window
            window_update_frame conn_wu(0, static_cast<uint32_t>(data_size));
            send_frame(conn_wu);
 
            // Update stream window
            window_update_frame stream_wu(stream_id, static_cast<uint32_t>(data_size));
            send_frame(stream_wu);
        }
 
        if (f.is_end_stream()) {
            stream.state = stream_state::half_closed_remote;
            stream.body_complete = true;
 
            // Need to unlock before dispatching
            lock.~lock_guard();
            dispatch_request(stream_id);
        }
 
        return ok();
    }
 
    auto http2_server_connection::handle_rst_stream_frame(const rst_stream_frame& f) -> VoidResult
    {
        close_stream(f.header().stream_id);
        return ok();
    }
 
    auto http2_server_connection::handle_ping_frame(const ping_frame& f) -> VoidResult
    {
        if (f.is_ack()) {
            return ok();
        }
 
        // Send PING ACK
        ping_frame ack(f.opaque_data(), true);
        return send_frame(ack);
    }
 
    auto http2_server_connection::handle_goaway_frame(const goaway_frame& /*f*/) -> VoidResult
    {
        // Client is closing connection
        stop();
        return ok();
    }
 
    auto http2_server_connection::handle_window_update_frame(const window_update_frame& f) -> VoidResult
    {
        uint32_t stream_id = f.header().stream_id;
        int32_t increment = static_cast<int32_t>(f.window_size_increment());
 
        if (stream_id == 0) {
            // Connection-level flow control
            connection_window_size_ += increment;
        } else {
            // Stream-level flow control
            std::lock_guard<std::mutex> lock(streams_mutex_);
            auto it = streams_.find(stream_id);
            if (it != streams_.end()) {
                it->second.window_size += increment;
            }
        }
 
        return ok();
    }
 
    auto http2_server_connection::dispatch_request(uint32_t stream_id) -> void
    {
        if (!request_handler_) {
            return;
        }
 
        http2_stream* stream = nullptr;
        {
            std::lock_guard<std::mutex> lock(streams_mutex_);
            auto it = streams_.find(stream_id);
            if (it == streams_.end()) {
                return;
            }
            stream = &it->second;
        }
 
        // Create request from headers
        auto request = http2_request::from_headers(stream->request_headers);
        request.body = stream->request_body;
 
        // Create server stream for response
        auto encoder_ptr = std::make_shared<hpack_encoder>(encoder_);
        auto weak_this = weak_from_this();
 
        http2_server_stream server_stream(
            stream_id,
            std::move(request),
            encoder_ptr,
            [weak_this](const frame& f) -> VoidResult {
                auto self = weak_this.lock();
                if (!self) {
                    return error_void(
                        error_codes::common_errors::internal_error,
                        "Connection closed",
                        "http2_server_stream");
                }
                return self->send_frame(f);
            },
            remote_settings_.max_frame_size);
 
        // Call request handler
        try {
            request_handler_(server_stream, server_stream.request());
        } catch (const std::exception& e) {
            if (error_handler_) {
                error_handler_(std::string("Request handler exception: ") + e.what());
            }
        }
 
        // Close stream after handler completes
        close_stream(stream_id);
    }
 
} // namespace kcenon::network::protocols::http2