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

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

#if !defined(_AURUNTIME_GENERIC_SEMAPHORE)
namespace Aurora::Threading::Primitives
{
    static BOOL(_stdcall *WaitOnAddress_f)(
        volatile VOID *Address,
        PVOID         CompareAddress,
        SIZE_T        AddressSize,
        DWORD         dwMilliseconds
    ) =
    #if defined(AURORA_PLATFORM_WIN32)
        decltype(WaitOnAddress_f)(GetProcAddress(LoadLibraryA("API-MS-Win-Core-Synch-l1-2-0.dll"), "WaitOnAddress"));
    #else
        WaitOnAddress;
    #endif

    static void(_stdcall *WakeByAddressSingle_f)(
        PVOID Address
    ) =
    #if defined(AURORA_PLATFORM_WIN32)
        decltype(WakeByAddressSingle_f)(GetProcAddress(LoadLibraryA("API-MS-Win-Core-Synch-l1-2-0.dll"), "WakeByAddressSingle"));
    #else
        WakeByAddressSingle;
    #endif

    static void(_stdcall *WakeByAddressAll_f)(
        PVOID Address
    ) =
    #if defined(AURORA_PLATFORM_WIN32)
        decltype(WakeByAddressAll_f)(GetProcAddress(LoadLibraryA("API-MS-Win-Core-Synch-l1-2-0.dll"), "WakeByAddressAll"));
    #else
        WakeByAddressAll;
    #endif
    
    Semaphore::Semaphore(long iIntialValue)
    {
        this->value_ = iIntialValue;
        if (!WaitOnAddress_f)
        {
            ::InitializeSRWLock(&this->lock_);
            ::InitializeConditionVariable(&this->winCond_);
        }
    }
    
    Semaphore::~Semaphore()
    {

    }

    bool Semaphore::HasOSHandle(AuMach &mach)
    {
        return false;
    }
    
    bool Semaphore::HasLockImplementation()
    {
        return true;
    }
    
    bool Semaphore::TryLock()
    {
        auto old = this->value_;
        return (old != 0 && AuAtomicCompareExchange(&this->value_, old - 1, old) == old);
    }
    
    bool Semaphore::Lock(AuUInt64 uTimeout)
    {
        if (this->TryLock())
        {
            return true;
        }

        AuUInt64 uStart = AuTime::SteadyClockMS();
        AuUInt64 uEnd = uStart + uTimeout;

        if (WaitOnAddress_f)
        {
            auto old = this->value_;
                 //!tryLock (with old in a scope we can access)
            while (!((old != 0) &&
                     (AuAtomicCompareExchange(&this->value_, old - 1, old) == old)))
            {
                AuUInt32 timeoutMs = INFINITE;

                if (uTimeout != 0)
                {
                    uStart = Time::SteadyClockMS();
                    if (uStart >= uEnd)
                    {
                        return false;
                    }

                    timeoutMs = uEnd - uStart;
                }

                if (!WaitOnAddress_f(&this->value_, &old, sizeof(this->value_), timeoutMs))
                {
                    SysAssertExp(GetLastError() == ERROR_TIMEOUT);
                    return false;
                }

                old = this->value_;
            }

            return true;
        }
        else
        {
            ::AcquireSRWLockShared(&this->lock_); // we use atomics. using shared is fine, let's not get congested early 
            while (!TryLock())
            {
                AuUInt32 dwTimeoutMs = INFINITE;

                if (uTimeout != 0)
                {
                    uStart = Time::SteadyClockMS();
                    if (uStart >= uEnd)
                    {
                        ::ReleaseSRWLockShared(&this->lock_);
                        return false;
                    }

                    dwTimeoutMs = uEnd - uStart;
                }

                if (!::SleepConditionVariableSRW(&this->winCond_, &this->lock_, AuUInt32(dwTimeoutMs), CONDITION_VARIABLE_LOCKMODE_SHARED))
                {
                    ::ReleaseSRWLockShared(&this->lock_);
                    return false;
                }
            }
            ::ReleaseSRWLockShared(&this->lock_);
        }

        return true;
    }
    
    void Semaphore::Lock()
    {
        auto status = Lock(0);
        SysAssert(status, "Couldn't lock semaphore");
    }
    
    void Semaphore::Unlock(long count)
    {
        if (!WaitOnAddress_f)
        {
            ::AcquireSRWLockShared(&this->lock_);
            AuAtomicAdd<AuInt32>(&this->value_, count);
            ::WakeAllConditionVariable(&this->winCond_);
            ::ReleaseSRWLockShared(&this->lock_);
        }
        else
        {
            AuAtomicAdd<AuInt32>(&this->value_, count);
            if (count == 1)
            {
                WakeByAddressSingle_f(&this->value_);
            }
            else
            {
                WakeByAddressAll_f(&this->value_);
            }
        }
    }
    
    void Semaphore::Unlock()
    {
        return Unlock(1);
    }
    
    AUKN_SYM ISemaphore *SemaphoreNew(int iInitialCount)
    {
        return _new Semaphore(iInitialCount);
    }

    AUKN_SYM void SemaphoreRelease(ISemaphore *pSemaphore)
    {
        AuSafeDelete<Semaphore *>(pSemaphore);
    }
}
#endif