event_bus.h

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#pragma once
 
#include "event.h"
#include <stdint.h>
#include <stddef.h>
 
namespace ersa {
namespace events {
 
using SubscriptionId = uint16_t;
using EventCallback = void (*)(const Event& event, void* userData);
 
class IEventListener {
public:
    virtual ~IEventListener() = default;
    virtual void onEvent(const Event& event) = 0;
};
 
struct Subscription {
    SubscriptionId id{0};
    EventType type{EventType::None}; // None = match all events
    EventCallback callback{nullptr};
    IEventListener* listener{nullptr};
    void* userData{nullptr};
    bool active{false};
};
 
class EventBus {
public:
    static constexpr size_t MAX_SUBSCRIBERS = 24;
    static constexpr size_t MAX_QUEUE = 32;
 
    EventBus();
 
    SubscriptionId subscribe(EventType type, EventCallback callback, void* userData = nullptr);
 
    SubscriptionId subscribe(EventType type, IEventListener* listener);
 
    bool unsubscribe(SubscriptionId id);
 
    void publish(const Event& event);
 
    bool post(const Event& event);
 
    size_t dispatchQueue();
 
    void clear();
 
    static EventBus& instance();
 
private:
    Subscription subscribers_[MAX_SUBSCRIBERS];
    SubscriptionId nextSubId_{1};
 
    Event queue_[MAX_QUEUE];
    size_t queueHead_{0};
    size_t queueTail_{0};
    size_t queueCount_{0};
};
 
} // namespace events
} // namespace ersa