client_session.hpp

/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * Copyright (C) 2025 Marco Craveiro <marco.craveiro@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */
#ifndef ORES_COMMS_NET_CLIENT_SESSION_HPP
#define ORES_COMMS_NET_CLIENT_SESSION_HPP
 
#include <mutex>
#include <deque>
#include <memory>
#include <chrono>
#include <optional>
#include <expected>
#include <functional>
#include <string>
#include <vector>
#include <set>
#include <boost/uuid/uuid.hpp>
#include "ores.logging/make_logger.hpp"
#include "ores.comms/messaging/message_types.hpp"
#include "ores.comms/messaging/message_traits.hpp"
#include "ores.comms/messaging/frame.hpp"
#include "ores.comms/messaging/error_protocol.hpp"
#include "ores.comms/net/client.hpp"
#include "ores.comms/net/client_options.hpp"
 
namespace ores::comms::service {
 
class remote_event_adapter;
 
}
 
namespace ores::comms::net {
 
struct client_session_info {
    boost::uuids::uuid account_id;
    std::string username;
    std::string email;
};
 
struct pending_notification {
    std::string event_type;
    std::chrono::system_clock::time_point timestamp;
    std::vector<std::string> entity_ids;
};
 
enum class client_session_error {
    not_connected,
    not_logged_in,
    login_required,
    admin_required,
    request_failed,
    deserialization_failed,
    server_error,
    connection_lost
};
 
struct session_error {
    client_session_error code;
    std::string message;
 
    explicit session_error(client_session_error c)
        : code(c) {}
 
    session_error(client_session_error c, std::string msg)
        : code(c), message(std::move(msg)) {}
};
 
template<typename Request>
concept Serializable = requires(Request req) {
    { req.serialize() } -> std::convertible_to<std::vector<std::byte>>;
};
 
template<typename Response>
concept Deserializable = requires(std::span<const std::byte> data) {
    {
        Response::deserialize(data)
    } -> std::same_as<std::expected<Response, ores::utility::serialization::error_code>>;
};
 
class client_session final {
private:
    inline static std::string_view logger_name =
        "ores.comms.net.client_session";
 
    static auto& lg() {
        using namespace ores::logging;
        static auto instance = make_logger(logger_name);
        return instance;
    }
 
public:
    client_session();
    ~client_session();
 
    // Non-copyable, non-movable (contains mutex)
    client_session(const client_session&) = delete;
    client_session& operator=(const client_session&) = delete;
    client_session(client_session&&) = delete;
    client_session& operator=(client_session&&) = delete;
 
    std::expected<void, session_error> connect(client_options options);
 
    std::expected<void, session_error>
    attach_client(std::shared_ptr<client> external_client);
 
    void disconnect();
 
    void detach_client();
 
    [[nodiscard]] bool is_connected() const noexcept;
 
    [[nodiscard]] std::shared_ptr<client> get_client() const noexcept {
        return client_;
    }
 
    [[nodiscard]] bool is_logged_in() const noexcept {
        return session_info_.has_value();
    }
 
    void set_session_info(client_session_info info) {
        session_info_ = std::move(info);
    }
 
    void clear_session_info() noexcept {
        session_info_.reset();
    }
 
    [[nodiscard]] const std::optional<client_session_info>& session_info() const noexcept {
        return session_info_;
    }
 
    [[nodiscard]] std::string username() const noexcept {
        return session_info_.has_value() ? session_info_->username : std::string{};
    }
 
    [[nodiscard]] std::string email() const noexcept {
        return session_info_.has_value() ? session_info_->email : std::string{};
    }
 
    void set_email(const std::string& email) {
        if (session_info_.has_value()) {
            session_info_->email = email;
        }
    }
 
    [[nodiscard]] std::optional<boost::uuids::uuid> account_id() const noexcept {
        if (session_info_.has_value()) {
            return session_info_->account_id;
        }
        return std::nullopt;
    }
 
    template <Serializable RequestType,
              Deserializable ResponseType,
              messaging::message_type RequestMsgType>
    std::expected<ResponseType, session_error>
    process_request(RequestType request) {
        using namespace ores::logging;
 
        if (!client_ || !client_->is_connected()) {
            BOOST_LOG_SEV(lg(), error) << "Not connected to server";
            return std::unexpected(session_error(client_session_error::not_connected));
        }
 
        BOOST_LOG_SEV(lg(), debug) << "Processing request type: "
                                   << RequestMsgType;
 
        auto payload = request.serialize();
        messaging::frame request_frame(RequestMsgType, 0, std::move(payload));
 
        auto response_result = client_->send_request_sync(std::move(request_frame));
 
        if (!response_result) {
            auto error_code = response_result.error();
            BOOST_LOG_SEV(lg(), error) << "Request failed with error code: "
                                       << static_cast<int>(error_code);
            // Check if this is a network error indicating connection loss
            if (error_code == ores::utility::serialization::error_code::network_error) {
                return std::unexpected(session_error(
                    client_session_error::connection_lost,
                    "Connection to server lost"));
            }
            return std::unexpected(session_error(
                client_session_error::request_failed,
                "Request failed: " + messaging::to_string(error_code)));
        }
 
        auto decompressed = response_result->decompressed_payload();
        if (!decompressed) {
            BOOST_LOG_SEV(lg(), error) << "Failed to decompress response payload";
            return std::unexpected(session_error(client_session_error::deserialization_failed));
        }
 
        // Check for error response
        if (response_result->header().type == messaging::message_type::error_response) {
            auto err_resp = messaging::error_response::deserialize(*decompressed);
            if (err_resp) {
                BOOST_LOG_SEV(lg(), error) << "Server returned error: "
                                           << err_resp->message;
                return std::unexpected(session_error(
                    client_session_error::server_error,
                    err_resp->message));
            }
            return std::unexpected(session_error(client_session_error::server_error));
        }
 
        auto response = ResponseType::deserialize(*decompressed);
        if (!response) {
            BOOST_LOG_SEV(lg(), error) << "Failed to deserialize response";
            return std::unexpected(session_error(client_session_error::deserialization_failed));
        }
 
        BOOST_LOG_SEV(lg(), debug) << "Successfully processed request";
        return std::move(*response);
    }
 
    template <Serializable RequestType,
              Deserializable ResponseType,
              messaging::message_type RequestMsgType>
    std::expected<ResponseType, session_error>
    process_authenticated_request(RequestType request) {
        using namespace ores::logging;
        if (!is_logged_in()) {
            BOOST_LOG_SEV(lg(), warn) << "Attempted authenticated request while "
                                      << "not logged in";
            return std::unexpected(session_error(client_session_error::not_logged_in));
        }
        return process_request<RequestType, ResponseType, RequestMsgType>(
            std::move(request));
    }
 
    template <Serializable RequestType,
              Deserializable ResponseType,
              messaging::message_type RequestMsgType>
    [[deprecated("Permission checks are now server-side via RBAC")]]
    std::expected<ResponseType, session_error>
    process_admin_request(RequestType request) {
        // Permission checks now happen server-side via RBAC
        return process_authenticated_request<RequestType, ResponseType, RequestMsgType>(
            std::move(request));
    }
 
    // =========================================================================
    // Traits-based process_request overloads
    // =========================================================================
    // These overloads use message_traits to infer the response type and
    // message_type enum from the request type, simplifying the API.
 
    template <typename RequestType>
        requires messaging::has_message_traits<RequestType>
    std::expected<typename messaging::message_traits<RequestType>::response_type,
                  session_error>
    process_request(RequestType request) {
        using traits = messaging::message_traits<RequestType>;
        return process_request<
            RequestType,
            typename traits::response_type,
            traits::request_message_type>(std::move(request));
    }
 
    template <typename RequestType>
        requires messaging::has_message_traits<RequestType>
    std::expected<typename messaging::message_traits<RequestType>::response_type,
                  session_error>
    process_authenticated_request(RequestType request) {
        using traits = messaging::message_traits<RequestType>;
        return process_authenticated_request<
            RequestType,
            typename traits::response_type,
            traits::request_message_type>(std::move(request));
    }
 
    template <typename RequestType>
        requires messaging::has_message_traits<RequestType>
    [[deprecated("Permission checks are now server-side via RBAC")]]
    std::expected<typename messaging::message_traits<RequestType>::response_type,
                  session_error>
    process_admin_request(RequestType request) {
        // Permission checks now happen server-side via RBAC
        return process_authenticated_request(std::move(request));
    }
 
    bool subscribe(const std::string& event_type);
 
    bool unsubscribe(const std::string& event_type);
 
    [[nodiscard]] bool is_subscribed(const std::string& event_type) const;
 
    [[nodiscard]] std::set<std::string> get_subscriptions() const;
 
    std::vector<pending_notification> take_pending_notifications();
 
    [[nodiscard]] bool has_pending_notifications() const;
 
    using notification_callback_t = std::function<void(
        const std::string& event_type,
        std::chrono::system_clock::time_point timestamp,
        const std::vector<std::string>& entity_ids)>;
 
    void set_notification_callback(notification_callback_t callback);
 
private:
    void on_notification(const std::string& event_type,
        std::chrono::system_clock::time_point timestamp,
        const std::vector<std::string>& entity_ids);
 
    std::shared_ptr<client> client_;
    std::unique_ptr<service::remote_event_adapter> event_adapter_;
    std::optional<client_session_info> session_info_;
    mutable std::mutex notifications_mutex_;
    std::deque<pending_notification> pending_notifications_;
 
    // External notification callback (if set, replaces internal queuing)
    notification_callback_t external_notification_callback_;
 
    // True when client is externally managed (attached via attach_client).
    // In this mode, disconnect() will not call client_->disconnect().
    bool external_client_{false};
};
 
std::string to_string(client_session_error error);
 
std::string to_string(const session_error& error);
 
}
 
#endif