subscription_manager.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_SERVICE_SUBSCRIPTION_MANAGER_HPP
#define ORES_COMMS_SERVICE_SUBSCRIPTION_MANAGER_HPP
 
#include <mutex>
#include <string>
#include <vector>
#include <chrono>
#include <memory>
#include <functional>
#include <unordered_map>
#include <unordered_set>
#include "ores.utility/log/make_logger.hpp"
 
namespace ores::comms::service {
 
using notification_callback =
    std::function<bool(const std::string&, std::chrono::system_clock::time_point)>;
 
using session_id = std::string;
 
class subscription_manager final {
private:
    [[nodiscard]] static auto& lg() {
        using namespace ores::utility::log;
        static auto instance = make_logger(
            "ores.comms.service.subscription_manager");
        return instance;
    }
 
    struct session_info {
        notification_callback callback;
        std::unordered_set<std::string> subscribed_events;
    };
 
public:
    subscription_manager() = default;
    ~subscription_manager() = default;
 
    subscription_manager(const subscription_manager&) = delete;
    subscription_manager& operator=(const subscription_manager&) = delete;
    subscription_manager(subscription_manager&&) = delete;
    subscription_manager& operator=(subscription_manager&&) = delete;
 
    void register_session(const session_id& id, notification_callback callback);
 
    void unregister_session(const session_id& id);
 
    bool subscribe(const session_id& id, const std::string& event_type);
 
    bool unsubscribe(const session_id& id, const std::string& event_type);
 
    std::size_t notify(const std::string& event_type,
                       std::chrono::system_clock::time_point timestamp);
 
    [[nodiscard]] std::size_t subscriber_count(const std::string& event_type) const;
 
    [[nodiscard]] std::size_t session_count() const;
 
    [[nodiscard]] std::vector<std::string> get_subscriptions(const session_id& id) const;
 
private:
    mutable std::mutex mutex_;
    std::unordered_map<session_id, session_info> sessions_;
    std::unordered_map<std::string, std::unordered_set<session_id>> event_subscribers_;
};
 
}
 
#endif