EventListener.h

/*
 * MIT License
 *
 * Copyright (c) 2025 Adriano dos Santos Fernandes
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
 
#ifndef FBCPP_EVENT_LISTENER_H
#define FBCPP_EVENT_LISTENER_H
 
#include "Attachment.h"
#include "Client.h"
#include "Exception.h"
#include "SmartPtrs.h"
#include "fb-api.h"
#include <condition_variable>
#include <cstdint>
#include <deque>
#include <functional>
#include <mutex>
#include <string>
#include <thread>
#include <vector>
 
 
namespace fbcpp
{
    struct EventCount final
    {
        std::string name;
 
        unsigned count;
    };
 
    class EventListener final
    {
    public:
        using Callback = std::function<void(const std::vector<EventCount>& counts)>;
 
    private:
        class FirebirdCallback final : public fb::IEventCallbackImpl<FirebirdCallback, impl::StatusWrapper>
        {
        public:
            explicit FirebirdCallback(EventListener& owner) noexcept
                : owner{&owner}
            {
            }
 
            void eventCallbackFunction(unsigned length, const std::uint8_t* events) override
            {
                if (owner)
                    owner->handleEvent(length, events);
            }
 
            void addRef() override
            {
                // The listener owns this callback for its whole lifetime.
            }
 
            int release() override
            {
                // Prevent Firebird from attempting to destroy the stack-allocated callback.
                return 1;
            }
 
            void detach() noexcept
            {
                owner = nullptr;
            }
 
        private:
            EventListener* owner;
        };
 
    public:
        explicit EventListener(Attachment& attachment, const std::vector<std::string>& eventNames, Callback callback);
 
        ~EventListener() noexcept
        {
            try
            {
                stop();
            }
            catch (...)
            {
                // swallow
            }
        }
 
        EventListener(const EventListener&) = delete;
        EventListener& operator=(const EventListener&) = delete;
 
        EventListener(EventListener&&) = delete;
        EventListener& operator=(EventListener&&) = delete;
 
    public:
        bool isListening() noexcept;
 
        void stop();
 
    private:
        void handleEvent(unsigned length, const std::uint8_t* events);
        void dispatchLoop();
        void cancelEventsHandle();
        void decodeEventCounts();
 
    private:
        Attachment& attachment;
        Client& client;
        std::vector<std::string> eventNames;
        Callback callback;
        FbRef<fb::IEvents> eventsHandle;
        FirebirdCallback firebirdCallback;
        std::vector<std::uint8_t> eventBuffer;
        std::vector<std::uint8_t> resultBuffer;
        std::vector<std::uint32_t> rawCounts;
        std::vector<unsigned> countOffsets;
        std::deque<std::vector<EventCount>> pendingNotifications;
        std::thread dispatcher;
        std::mutex mutex;
        std::condition_variable condition;
        bool listening = false;
        bool running = false;
        bool first = false;
    };
}  // namespace fbcpp
 
 
#endif  // FBCPP_EVENT_LISTENER_H