dispatcher.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_DISPATCHER_HPP
#define ANTKEEPER_EVENT_DISPATCHER_HPP
 
#include <engine/event/subscriber.hpp>
#include <engine/event/subscription.hpp>
#include <any>
#include <map>
#include <memory>
#include <typeindex>
#include <utility>
 
namespace event {
 
class dispatcher
{
public:
    template <class T>
    [[nodiscard]] std::shared_ptr<subscription> subscribe(subscriber<T>&& subscriber)
    {
        // Allocate shared pointer to std::any object containing subscriber
        std::shared_ptr<std::any> shared_subscriber = std::make_shared<std::any>(std::make_any<event::subscriber<T>>(std::move(subscriber)));
        
        // Append subscriber to subscriber list and store iterator
        auto iterator = subscribers.emplace(std::type_index(typeid(T)), 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);
            }
        );
    }
    
    template <class T>
    void dispatch(const T& message) const
    {
        // For each subscriber of the given message type
        const auto range = subscribers.equal_range(std::type_index(typeid(T)));
        for (auto i = range.first; i != range.second; ++i)
        {
            // Send message to subscriber
            std::any_cast<subscriber<T>>(*(i->second))(message);
        }
    }
 
private:
    std::multimap<std::type_index, std::shared_ptr<std::any>> subscribers;
};
 
} // namespace event
 
#endif // ANTKEEPER_EVENT_DISPATCHER_HPP