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

    File: AuConditionMutex.Win32.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuConditionMutex.Generic.hpp"
#include "SMPYield.hpp"
#include "AuProcAddresses.NT.hpp"

#if !defined(_AURUNTIME_GENERICCM)

namespace Aurora::Threading::Primitives
{

    Win32ConditionMutex::Win32ConditionMutex()
    {
        if (gKeyedEventHandle == INVALID_HANDLE_VALUE)
        {
            if (!pNtCreateKeyedEvent)
            {
                InitNTAddresses();
            }

            pNtCreateKeyedEvent(&gKeyedEventHandle, -1, NULL, 0);
        }
    }

    Win32ConditionMutex::~Win32ConditionMutex()
    {
    }

    bool Win32ConditionMutex::TryLock()
    {
        return DoTryIf([=]()
        {
            return !AuAtomicTestAndSet(&this->lock_.uWaitCount, 0);
        });
    }

    void Win32ConditionMutex::Lock()
    {
        while (!TryLock())
        {
            auto &uValueRef = this->lock_.uWaitCount;
            auto uValue = uValueRef | 1;
        
            if (AuAtomicCompareExchange(&uValueRef, uValue + FAST_M_WAIT, uValue) == uValue)
            {
                pNtWaitForKeyedEvent(gKeyedEventHandle, (void *)&uValueRef, 0, NULL);
        
                AuAtomicSub(&uValueRef, FAST_M_WAKE);
            }
        }
    }

    void Win32ConditionMutex::Unlock()
    {
        auto &uValueRef = this->lock_.uWaitCount;

        while (true)
        {
            auto uNow    = uValueRef;
            auto uNext   = uNow & ~0xFF;

            if (AuAtomicCompareExchange(&uValueRef, uNext, uNow) == uNow)
            {
                break;
            }
        }

        while (true)
        {
            auto uOld = uValueRef;
            auto uValue = uOld;
        
            if (uValue & 1)
            {
                return;
            }

            if (uValue < FAST_M_WAIT)
            {
                return;
            }
          
            if (uValue & FAST_M_WAKE)
            {
                return;
            }
        
            if (AuAtomicCompareExchange(&uValueRef, uValue - FAST_M_WAIT + FAST_M_WAKE, uValue) == uValue)
            {
                pNtReleaseKeyedEvent(gKeyedEventHandle, (void *)&uValueRef, 0, NULL);
                return;
            }
        
            SMPPause();
        }
    }

    AuUInt Win32ConditionMutex::GetOSHandle()
    {
        return reinterpret_cast<AuUInt>(&this->lock_);
    }

    AUKN_SYM IConditionMutex *ConditionMutexNew()
    {
        return _new Win32ConditionMutex();
    }

    AUKN_SYM void ConditionMutexRelease(IConditionMutex *pMutex)
    {
        AuSafeDelete<Win32ConditionMutex *>(pMutex);
    }
}

#endif