// SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
//
// SPDX-License-Identifier: GPL-3.0-or-later

#include "threads/condition_variable.h"

#include "utility/validate_aligned_storage.h"

#include <algorithm>

#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
#include "errors/fatal.h"
#include <pthread.h>
#elif defined(_WIN32) || defined(_WIN64)
#include <windows.h>
#undef max
#undef min
#endif

namespace BaseKit {

//! @cond INTERNALS

class ConditionVariable::Impl
{
public:
    Impl()
    {
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        int result = pthread_cond_init(&_cond, nullptr);
        if (result != 0)
            throwex SystemException("Failed to initialize a condition variable!", result);
#elif defined(_WIN32) || defined(_WIN64)
        InitializeConditionVariable(&_cond);
#endif
    }

    ~Impl()
    {
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        int result = pthread_cond_destroy(&_cond);
        if (result != 0)
            fatality(SystemException("Failed to destroy a condition variable!", result));
#elif defined(_WIN32) || defined(_WIN64)
        // Condition variables do not need to be explicitly destroyed.
#endif
    }

    void NotifyOne()
    {
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        int result = pthread_cond_signal(&_cond);
        if (result != 0)
            throwex SystemException("Failed to signal a condition variable!", result);
#elif defined(_WIN32) || defined(_WIN64)
        WakeConditionVariable(&_cond);
#endif
    }

    void NotifyAll()
    {
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        int result = pthread_cond_broadcast(&_cond);
        if (result != 0)
            throwex SystemException("Failed to broadcast a condition variable!", result);
#elif defined(_WIN32) || defined(_WIN64)
        WakeAllConditionVariable(&_cond);
#endif
    }

    void Wait(CriticalSection& cs)
    {
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        int result = pthread_cond_wait(&_cond, (pthread_mutex_t*)cs.native());
        if (result != 0)
            throwex SystemException("Failed to waiting a condition variable!", result);
#elif defined(_WIN32) || defined(_WIN64)
        if (!SleepConditionVariableCS(&_cond, (CRITICAL_SECTION*)cs.native(), INFINITE))
            throwex SystemException("Failed to waiting a condition variable!");
#endif
    }

    bool TryWaitFor(CriticalSection& cs, const Timespan& timespan)
    {
        if (timespan < 0)
            return false;
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
        struct timespec timeout;
        timeout.tv_sec = timespan.seconds();
        timeout.tv_nsec = timespan.nanoseconds() % 1000000000;
        int result = pthread_cond_timedwait(&_cond, (pthread_mutex_t*)cs.native(), &timeout);
        if ((result != 0) && (result != ETIMEDOUT))
            throwex SystemException("Failed to waiting a condition variable for the given timeout!", result);
        return (result == 0);
#elif defined(_WIN32) || defined(_WIN64)
        if (!SleepConditionVariableCS(&_cond, (CRITICAL_SECTION*)cs.native(), std::max((DWORD)0, (DWORD)timespan.milliseconds())))
        {
            if (GetLastError() != ERROR_TIMEOUT)
                throwex SystemException("Failed to waiting a condition variable for the given timeout!");
            return false;
        }
        return true;
#endif
    }

private:
#if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
    pthread_cond_t _cond;
#elif defined(_WIN32) || defined(_WIN64)
    CONDITION_VARIABLE _cond;
#endif
};

//! @endcond

ConditionVariable::ConditionVariable()
{
    // Check implementation storage parameters
    [[maybe_unused]] ValidateAlignedStorage<sizeof(Impl), alignof(Impl), StorageSize, StorageAlign> _;
    static_assert((StorageSize >= sizeof(Impl)), "ConditionVariable::StorageSize must be increased!");
    static_assert(((StorageAlign % alignof(Impl)) == 0), "ConditionVariable::StorageAlign must be adjusted!");

    // Create the implementation instance
    new(&_storage)Impl();
}

ConditionVariable::~ConditionVariable()
{
    // Delete the implementation instance
    reinterpret_cast<Impl*>(&_storage)->~Impl();
}

void ConditionVariable::NotifyOne() { impl().NotifyOne(); }
void ConditionVariable::NotifyAll() { impl().NotifyAll(); }

void ConditionVariable::Wait(CriticalSection& cs) { impl().Wait(cs); }

bool ConditionVariable::TryWaitFor(CriticalSection& cs, const Timespan& timespan) { return impl().TryWaitFor(cs, timespan); }

} // namespace BaseKit
