fallback_thread_backend.h

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// BSD 3-Clause License
// Copyright (c) 2025, 🍀☀🌕🌥 🌊
// See the LICENSE file in the project root for full license information.
 
#pragma once
 
#include "thread_backend.h"
 
#include <atomic>
#include <condition_variable>
#include <mutex>
#include <queue>
#include <thread>
#include <vector>
 
namespace database
{
namespace integrated
{
namespace adapters
{
namespace backends
{
 
class fallback_thread_backend : public thread_backend
{
public:
    explicit fallback_thread_backend(const db_thread_config& config);
    ~fallback_thread_backend() override;
 
    // Non-copyable, non-movable
    fallback_thread_backend(const fallback_thread_backend&) = delete;
    fallback_thread_backend& operator=(const fallback_thread_backend&) = delete;
    fallback_thread_backend(fallback_thread_backend&&) = delete;
    fallback_thread_backend& operator=(fallback_thread_backend&&) = delete;
 
    common::VoidResult initialize() override;
    common::VoidResult shutdown() override;
    bool is_initialized() const override;
 
    common::VoidResult execute(std::function<void()> task) override;
    void wait_for_completion() override;
    bool wait_for_completion_timeout(std::chrono::milliseconds timeout) override;
 
    std::size_t worker_count() const override;
    std::size_t queue_size() const override;
    bool is_idle() const override;
 
private:
    void worker_thread();
 
    const db_thread_config& config_;
    bool initialized_;
    std::atomic<bool> shutdown_requested_;
 
    std::vector<std::thread> workers_;
    std::queue<std::function<void()>> task_queue_;
 
    mutable std::mutex queue_mutex_;
    std::condition_variable queue_cv_;
 
    std::atomic<std::size_t> active_tasks_;
    mutable std::mutex completion_mutex_;
    std::condition_variable completion_cv_;
};
 
} // namespace backends
} // namespace adapters
} // namespace integrated
} // namespace database