Magic-Scrolls/include/engine/core/engine_bus.hpp

#ifndef __MSC_ENGINE_BUS_HPP__
#define __MSC_ENGINE_BUS_HPP__

#include <string>
#include <vector>
#include <mutex>
#include <unordered_map>
#include <functional>
#include <cstdint>

/// @brief Event base class
class MscEvent
{
public:
    virtual ~MscEvent() = default;

    /// @brief Get event name
    virtual std::string getName() const = 0;

    /// @brief Is current event is canceled
    bool isCanceled() const
    {
        return canceled;
    }

    /// @brief Cancel current event
    void cancel()
    {
        canceled = true;
    }

private:
    bool canceled = false;
};

/// @brief Engine event bus
class MscEventBus
{
public:
    /// @brief Event handler alias
    using Listener = std::function<void(MscEvent &)>;

    /// @brief Subscription identifier alias
    using SubscriptionId = std::uint64_t;

    /// @brief Emit event
    /// @param event event context
    void publish(MscEvent &event);

    /// @brief Subscribe to specified event
    /// @param name event name
    /// @param listener event handler
    /// @returns subscription identifier to make it possitble to remove listener
    SubscriptionId subscribe(const std::string &name, Listener listener);

    /// @brief Subscribe to specified event and execute once on publish
    /// @param name event name
    /// @param listener event handler
    SubscriptionId subscribeOnce(const std::string &name, Listener listener);

    /// @brief Unsubscribe listener by its own id
    /// @param id subscription id
    /// @return `true` if listener has been deleted, otherwise `false`
    bool unsubscribe(SubscriptionId id);

private:
    using ListenerWithId = struct
    {
        SubscriptionId id;
        Listener listener;
        bool once;
    };

    std::unordered_map<std::string, std::vector<ListenerWithId>> _listeners;
    std::unordered_map<SubscriptionId, std::string> _listenersPaths;
    std::uint64_t _lastId = 0;
    std::mutex _listenersMutex;

    SubscriptionId _subscribe(const std::string &name, Listener listener, bool once);
};

#endif // __MSC_ENGINE_BUS_HPP__