channel.hpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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.
 *
 * Antkeeper source code 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 Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef ANTKEEPER_EVENT_CHANNEL_HPP
#define ANTKEEPER_EVENT_CHANNEL_HPP
 
#include <functional>
#include <list>
#include <memory>
#include <utility>
#include <engine/event/subscriber.hpp>
#include <engine/event/subscription.hpp>
#include <engine/event/dispatcher.hpp>
#include <engine/event/queue.hpp>
 
namespace event {
 
template <class T>
class publisher;
 
template <class T>
class channel
{
public:
    typedef T message_type;
    
    typedef subscriber<message_type> subscriber_type;
    
    [[nodiscard]] std::shared_ptr<subscription> subscribe(subscriber_type&& subscriber)
    {
        // Construct shared pointer to subscriber function
        std::shared_ptr<subscriber_type> shared_subscriber = std::make_shared<subscriber_type>(std::move(subscriber));
        
        // Append subscriber to subscriber list and store iterator
        auto iterator = subscribers.insert(subscribers.end(), shared_subscriber);
        
        // Construct and return a shared subscription object which removes the subscriber from the subscriber list when unsubscribed or destructed
        return std::make_shared<subscription>
        (
            std::static_pointer_cast<void>(shared_subscriber),
            [this, iterator = std::move(iterator)]
            {
                this->subscribers.erase(iterator);
            }
        );
    }
    
    [[nodiscard]] std::shared_ptr<subscription> subscribe(event::dispatcher& dispatcher)
    {
        return subscribe
        (
            [&dispatcher](const message_type& message)
            {
                dispatcher.dispatch<message_type>(message);
            }
        );
    }
    
    [[nodiscard]] std::shared_ptr<subscription> subscribe(event::queue& queue)
    {
        return subscribe
        (
            [&queue](const message_type& message)
            {
                queue.enqueue<message_type>(message);
            }
        );
    }
    
private:
    friend class publisher<T>;
    
    std::list<std::shared_ptr<subscriber_type>> subscribers;
};
 
} // namespace event
 
#endif // ANTKEEPER_EVENT_CHANNEL_HPP