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

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

namespace Aurora::Threading::Primitives
{
    EventImpl::EventImpl(bool bTriggered, bool bAtomicRelease, bool bPermitMultipleTriggers) :
        bTriggered_(bTriggered),
        bAtomicRelease_(bAtomicRelease),
        bPermitMultipleTriggers_(bPermitMultipleTriggers)
    {}

    EventImpl::~EventImpl() {}

    bool EventImpl::Init()
    {
        return true;
    }

    bool EventImpl::LockMS(AuUInt64 uTimeout /*=0*/)
    {
        return this->LockNS(AuMSToNS<AuUInt64>(uTimeout));
    }

    bool EventImpl::LockNS(AuUInt64 uTimeout /*=0*/)
    {
        AuInt64 uStartTime {};
        AuInt64 uEndTime {};

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

        if (uTimeout)
        {
            uStartTime = Time::SteadyClockNS();
            uEndTime = uStartTime + uTimeout;
        }

        if (gPreferFutexEvent)
        {
            auto pSleepCounter = this->GetSleepCounter();

            while (!this->AtomicIsEventSetLogicNoSpinNoLock())
            {
                bool bStatus {};
                EventBits bits;
                bits.state = AuAtomicLoad(&this->state_);

                if (bits.bTriggered)
                {
                    continue;
                }

                AuAtomicAdd(pSleepCounter, 1u);
                bStatus = InternalLTSWaitOnAddressHighRes(&this->state_, &bits.state, sizeof(bits.state), uEndTime);
                AuAtomicSub(pSleepCounter, 1u);
                
                if (!bStatus)
                {
                    return false;
                }
            }
        }
        else
        {
            AU_LOCK_GUARD(this->mutex_);

            while (!AtomicIsEventSetLogicNoSpinNoLock())
            {
                AuUInt32 uTimeoutNS {};

                if (uTimeout)
                {
                    uStartTime = Time::SteadyClockNS();
                    if (uStartTime >= uEndTime)
                    {
                        return false;
                    }

                    uTimeoutNS = uEndTime - uStartTime;
                }

                if (!this->condition_.WaitForSignalNsEx(&this->mutex_, uTimeoutNS))
                {
                    continue;
                }
            }
        }

        return true;
    }
    
    bool EventImpl::LockAbsNS(AuUInt64 uEndTime)
    {
        if (this->AtomicIsEventSetLogicNoSpinNoLock())
        {
            return true;
        }

        if (gPreferFutexEvent)
        {
            auto pSleepCounter = this->GetSleepCounter();

            while (!this->AtomicIsEventSetLogicNoSpinNoLock())
            {
                bool bStatus {};
                EventBits bits;
                bits.state = AuAtomicLoad(&this->state_);

                if (bits.bTriggered)
                {
                    continue;
                }

                AuAtomicAdd(pSleepCounter, 1u);
                bStatus = InternalLTSWaitOnAddressHighRes(&this->state_, &bits.state, sizeof(bits.state), uEndTime);
                AuAtomicSub(pSleepCounter, 1u);

                if (!bStatus)
                {
                    return false;
                }
            }
        }
        else
        {
            AU_LOCK_GUARD(this->mutex_);

            while (!AtomicIsEventSetLogicNoSpinNoLock())
            {
                AuUInt32 uTimeoutNS {};

                if (uEndTime)
                {
                    auto uStartTime = Time::SteadyClockNS();
                    if (uStartTime >= uEndTime)
                    {
                        return false;
                    }

                    uTimeoutNS = uEndTime - uStartTime;
                }

                if (!this->condition_.WaitForSignalNsEx(&this->mutex_, uTimeoutNS))
                {
                    continue;
                }
            }
        }

        return true;
    }

    bool EventImpl::TryLock()
    {
        return AtomicIsEventSetLogicNoSpinNoLock();
    }

    bool EventImpl::AtomicIsEventSetLogicNoSpinNoLock()
    {
        EventBits bits;
        bits.state = AuAtomicLoad(&this->state_);
        if (bits.bAtomicRelease)
        {
            if (bits.bTriggered)
            {
                auto next = bits;
                next.bTriggered = 0;
                return AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state;
            }
            else
            {
                return false;
            }
        }
        else
        {
            return bits.bTriggered;
        }
    }

    void EventImpl::Reset()
    {
        while (true)
        {
            EventBits bits, next;
            bits.state = AuAtomicLoad(&this->state_);

            if (!bits.bTriggered)
            {
                break;
            }

            next.state = bits.state;
            next.bTriggered = 0;
            if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state)
            {
                break;
            }
        }
    }

    void EventImpl::Set()
    {
        EventBits bits, next;

        while (true)
        {
            bits.state = AuAtomicLoad(&this->state_);

            // TODO: runtime config option to turn this into a handable exception
            SysAssertExp((bits.bPermitMultipleTriggers) || (!bits.bTriggered), "Can not trigger an awake event object");

            next.state = bits.state;
            next.bTriggered = 1;
            if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state)
            {
                break;
            }
        }

        this->DoSignal(bits);
    }

    bool EventImpl::TrySet()
    {
        EventBits bits, next;

        while (true)
        {
            bits.state = AuAtomicLoad(&this->state_);

            if (!bits.bPermitMultipleTriggers)
            {
                if (bits.bTriggered)
                {
                    return false;
                }
            }

            next.state = bits.state;
            next.bTriggered = 1;
            if (AuAtomicCompareExchange(&this->state_, next.state, bits.state) == bits.state)
            {
                break;
            }
        }

        this->DoSignal(bits);

        return true;
    }

    void EventImpl::DoSignal(const EventBits &bits)
    {
        if (gPreferFutexEvent)
        {
            if (!AuAtomicLoad(GetSleepCounter()))
            {
                return;
            }

            if (bits.bAtomicRelease)
            {
                InternalLTSWakeOne(&this->state_);
            }
            else
            {
                InternalLTSWakeAll(&this->state_);
            }
        }
        else
        {
            this->mutex_.Lock();
            this->mutex_.Unlock();

            if (bits.bAtomicRelease)
            {
                this->condition_.Signal();
            }
            else
            {
                this->condition_.Broadcast();
            }
        }
    }

    bool EventImpl::HasOSHandle(AuMach &mach)
    {
        mach = this->bAtomicRelease_ ? 0xFF69421 : 0;
        return false;
    }

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

    void EventImpl::Lock()
    {
        auto ok = LockNS(0);
        SysAssert(ok);
    }

    void EventImpl::Unlock()
    {
        // Unlock is always a NOP; inverse of a lock/wait is nothing
    }

    AuUInt32 *EventImpl::GetSleepCounter()
    {
        return (AuUInt32 *)&this->condition_;
    }

    AUKN_SYM IEvent *EventNew(bool bTriggered, bool bAtomicRelease, bool bPermitMultipleTriggers)
    {
        auto event = _new EventImpl(bTriggered, bAtomicRelease, bPermitMultipleTriggers);
        if (!event)
        {
            return nullptr;
        }

        if (!event->Init())
        {
            EventRelease(event);
            return nullptr;
        }
        
        return event;
    }

    AUKN_SYM void EventRelease(IEvent *pEvent)
    {
        AuSafeDelete<EventImpl *>(pEvent);
    }

    AUROXTL_INTERFACE_SOO_SRC_EX(AURORA_SYMBOL_EXPORT, Event, EventImpl, (bool, bTriggered), (bool, bAtomicRelease), (bool, bPermitMultipleTriggers))
}