/***
    Copyright (C) 2021-2024 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: AuSemaphore.Generic.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuSemaphore.Generic.hpp"
#include "../AuWakeInternal.hpp"
#include "SMTYield.hpp"

#if defined(_AURUNTIME_GENERIC_SEMAPHORE)
namespace Aurora::Threading::Primitives
{
    SemaphoreGeneric::SemaphoreGeneric(AuUInt16 uIntialValue) :
        uAtomicState(uIntialValue),
        uAtomicSleeping(0)
    {

    }
    SemaphoreGeneric::~SemaphoreGeneric()
    {

    }

    bool SemaphoreGeneric::TryLockNoSpin()
    {
        auto uState = this->uAtomicState;
        return (uState != 0 && AuAtomicCompareExchange(&this->uAtomicState, uState - 1, uState) == uState);
    }

    bool SemaphoreGeneric::TryLockHeavy()
    {
        return DoTryIfAlderLake([=]()
        {
            return this->TryLockNoSpin();
        }, &this->uAtomicState);
    }

    bool SemaphoreGeneric::TryLock()
    {
        if (ThrdCfg::gPreferUnixPrimitivesNoSpin)
        {
            return this->TryLockNoSpin();
        }
        else
        {
            return this->TryLockHeavy();
        }
    }

    bool SemaphoreGeneric::HasOSHandle(AuMach &mach)
    {
        return false;
    }

    bool SemaphoreGeneric::HasLockImplementation()
    {
        return true;
    }

    void SemaphoreGeneric::Unlock()
    {
        this->Unlock(1);
    }

    void SemaphoreGeneric::Unlock(AuUInt16 uThreads)
    {
        AuAtomicAdd(&this->uAtomicState, AuUInt32(uThreads));

        if (auto uSleeping = AuAtomicLoad(&this->uAtomicSleeping))
        {
            InternalLTSWakeCount((const void *)&this->uAtomicState, AuMin(uSleeping, uThreads));
        }
    }

    void SemaphoreGeneric::Lock()
    {
        static const AuUInt32 kRef { 0 };

        if (this->TryLock())
        {
            return;
        }

        while (!this->TryLockNoSpin())
        {
            AuAtomicAdd(&this->uAtomicSleeping, 1u);
            InternalLTSWaitOnAddressHighRes((const void *)&this->uAtomicState, &kRef, sizeof(kRef), 0);
            AuAtomicSub(&this->uAtomicSleeping, 1u);
        }
    }

    bool SemaphoreGeneric::LockMS(AuUInt64 qwTimeout)
    {
        return LockNS(AuMSToNS<AuUInt64>(qwTimeout));
    }

    bool SemaphoreGeneric::LockAbsMS(AuUInt64 qwTimeout)
    {
        return LockAbsNS(AuMSToNS<AuUInt64>(qwTimeout));
    }

    bool SemaphoreGeneric::LockNS(AuUInt64 qwTimeout)
    {
        static const AuUInt32 kRef { 0 };

        if (this->TryLockNoSpin())
        {
            return true;
        }

        auto qwEndTime = qwTimeout ?
            Time::SteadyClockNS() + qwTimeout :
            0;

        if (!ThrdCfg::gPreferUnixPrimitivesNoSpin)
        {
            if (this->TryLockHeavy())
            {
                return true;
            }
        }

        while (!this->TryLockNoSpin())
        {
            bool bStatus {};

            AuAtomicAdd(&this->uAtomicSleeping, 1u);
            bStatus = InternalLTSWaitOnAddressHighRes((const void *)&this->uAtomicState, &kRef, sizeof(kRef), qwEndTime);
            AuAtomicSub(&this->uAtomicSleeping, 1u);

            if (!bStatus)
            {
                return TryLockNoSpin();
            }
        }

        return true;
    }

    bool SemaphoreGeneric::LockAbsNS(AuUInt64 qwTimeoutAbs)
    {
        static const AuUInt32 kRef { 0 };

        if (!ThrdCfg::gPreferUnixPrimitivesNoSpin)
        {
            if (this->TryLockHeavy())
            {
                return true;
            }
        }

        while (!TryLockNoSpin())
        {
            bool bStatus {};

            AuAtomicAdd(&this->uAtomicSleeping, 1u);
            bStatus = InternalLTSWaitOnAddressHighRes((const void *)&this->uAtomicState, &kRef, sizeof(kRef), qwTimeoutAbs);
            AuAtomicSub(&this->uAtomicSleeping, 1u);

            if (!bStatus)
            {
                return TryLockNoSpin();
            }
        }

        return true;
    }

    AUKN_SYM ISemaphore *SemaphoreNew(AuUInt16 uIntialValue)
    {
        return _new SemaphoreGeneric(uIntialValue);
    }

    AUKN_SYM void SemaphoreRelease(ISemaphore *waitable)
    {
        AuSafeDelete<SemaphoreGeneric *>(waitable);
    }

    AUROXTL_INTERFACE_SOO_SRC_EX(AURORA_SYMBOL_EXPORT, Semaphore, SemaphoreGeneric)
}
#endif