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

    File: Loop.cpp
    Date: 2021-9-21
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Loop.hpp"
#include "ILoopSourceEx.hpp"
#include "LSIOHandle.hpp"
#include <Source/Threading/Primitives/SMTYield.hpp>

namespace Aurora::IO::Loop
{
#if !defined(AURORA_IS_MODERNNT_DERIVED)
    AUKN_SYM AuSPtr<ILoopSource>    NewLSWin32Source(bool)
    {
        return {};
    }
#endif

#if !defined(AURORA_IS_XNU_DERIVED)
    AUKN_SYM AuSPtr<ILoopSource>    NewLSAppleSource()
    {
        return {};
    }
#endif

    AUKN_SYM AuSPtr<ILoopSource>    NewLSFile(const AuSPtr<AuIO::IAsyncTransaction> &pFileTransaction)
    {
        if (!pFileTransaction)
        {
            SysPushErrorArg();
            return {};
        }

        return pFileTransaction->NewLoopSource();
    }

    AUKN_SYM AuSPtr<ILoopSource>    NewStdIn()
    {
        return AuConsole::StdInBufferLoopSource();
    }

    AUKN_SYM AuSPtr<ILoopSource>    NewLSAsync(AuAsync::WorkerPId_t workerPid)
    {
        if (!workerPid)
        {
            return AuAsync::GetAsyncApp()->WorkerToLoopSource(workerPid);
        }

        return workerPid.GetPool()->WorkerToLoopSource(workerPid);
    }

#if defined(AURORA_IS_MODERNNT_DERIVED)
    AuList<AuSPtr<ILoopSource>> WaitMultipleOrObjects(const AuList<AuSPtr<ILoopSource>> &objects, bool bZeroTick, AuUInt32 timeout, bool bAllowOthers, bool &bTooMany);
#endif
    AuList<AuSPtr<ILoopSource>> WaitMultipleOrObjectsFallback(const AuList<AuSPtr<ILoopSource>> &objects, AuUInt32 timeout, bool bZeroTick, bool bAllowOthers, bool &bTimeout);

    void ResetLoopSourceFalseAlarm(const AuSPtr<Loop::ILoopSource> &pLoopSource)
    {
        if (!pLoopSource)
        {
            return;
        }

        if (pLoopSource->GetType() == ELoopSource::eSourceWin32)
        {
            return;
        }

        if (auto pMutex = AuDynamicCast<Loop::ILSMutex>(pLoopSource))
        {
            pMutex->Unlock();
            return;
        }

        if (auto pEvent = AuDynamicCast<Loop::ILSEvent>(pLoopSource))
        {
            pEvent->Set();
            return;
        }

        if (auto pSemaphore = AuDynamicCast<Loop::ILSSemaphore>(pLoopSource))
        {
            pSemaphore->AddOne();
            return;
        }
    }

    AUKN_SYM bool WaitMultipleLoopSources(const AuList<AuSPtr<Loop::ILoopSource>> &lsList,
                                          AuList<AuSPtr<Loop::ILoopSource>> &signaled,
                                          bool bAny,
                                          AuOptionalEx<AuUInt32> optTimeoutMS)
    {
        return WaitMultipleLoopSourcesEx(lsList, signaled, bAny ? kWaitMultipleFlagAny : 0, optTimeoutMS);
    }

    AUKN_SYM bool WaitMultipleLoopSourcesEx(const AuList<AuSPtr<Loop::ILoopSource>> &lsList,
                                            AuList<AuSPtr<Loop::ILoopSource>> &signaled,
                                            AuUInt64 uFlags,
                                            AuOptional<AuUInt32> optTimeoutMS)
    {
        signaled.clear();
        AuList<AuUInt32> reverseList;

        if (lsList.empty())
        {
            return true;
        }
        
        bool bAny          { bool(uFlags & kWaitMultipleFlagAny) };
        bool bSpin         { !(uFlags & kWaitMultipleFlagNoSpin) };
        bool bAvoidKrn     { bool(uFlags & kWaitMultipleFlagAvoidKern) };
        bool bZeroTick     { optTimeoutMS && optTimeoutMS.value() == 0 };
        bool bHasTimeOut   { optTimeoutMS && optTimeoutMS.value() };
        bool bSleepForever { !optTimeoutMS };

        if (lsList.size() == 1)
        {
            auto pSource = lsList[0];
            if (!pSource)
            {
                signaled.push_back({});
                return true;
            }

            bool bStatus {};
            if (bSleepForever)
            {
                bStatus = pSource->WaitOn(0);
            }
            else if (bHasTimeOut)
            {
                bStatus = pSource->WaitOn(optTimeoutMS.value());
            }
            else
            {
                bStatus = pSource->IsSignaled();
            }

            if (bStatus)
            {
                signaled.push_back(pSource);
            }

            return bStatus;
        }

        AuUInt64 uTimeoutEnd = bHasTimeOut ?
            AuTime::SteadyClockNS() + AuMSToNS<AuUInt64>(optTimeoutMS.value()) :
            0;

        AU_DEBUG_MEMCRUNCH;

        signaled.reserve(lsList.size());

        if (!bAny)
        {
            auto &entryZero = lsList[0];

            if (!entryZero)
            {
                signaled.push_back({});
            }

            if (entryZero)
            {
                bool bStatus {};

                if (bSleepForever)
                {
                    bStatus = entryZero->WaitOn(0);
                }
                else if (bHasTimeOut)
                {
                    bStatus = entryZero->WaitOn(optTimeoutMS.value());
                }
                else if (bSpin)
                {
                    bStatus = entryZero->IsSignaled();
                }
                else
                {
                    auto pSourceEx = AuDynamicCast<Loop::ILoopSourceEx>(entryZero);
                    bStatus = pSourceEx ?
                        pSourceEx->IsSignaledNoSpinIfUserland() :
                        entryZero->IsSignaled();
                }
         
                if (!bStatus)
                {
                    goto next;
                }
                else
                {
                    reverseList.push_back(0);
                    signaled.push_back(entryZero);
                }
            }

            if (lsList.size() > 1 &&
                (!bAvoidKrn || signaled.empty()))
            {
                for (AU_ITERATE_N_TO_X(i, 1, lsList.size()))
                {
                    AuUInt32 uTimeoutMS {};

                    if (uTimeoutEnd)
                    {
                        auto uStartTime = Time::SteadyClockNS();
                        if (uStartTime >= uTimeoutEnd)
                        {
                        #if 0
                            break;
                        #else
                            bZeroTick = true;
                        #endif
                        }

                        uTimeoutMS = AuNSToMS<AuInt64>(uTimeoutEnd - uStartTime);
                        if (!uTimeoutMS)
                        {
                        #if 0
                            break;
                        #else
                            bZeroTick = true;
                        #endif
                        }
                    }

                    if (bZeroTick)
                    {
                        if (bSpin)
                        {
                            if (!lsList[i]->IsSignaled())
                            {
                                break;
                            }
                        }
                        else
                        {
                            auto pSourceEx = AuDynamicCast<Loop::ILoopSourceEx>(lsList[i]);
                            if (!(pSourceEx ?
                                  pSourceEx->IsSignaledNoSpinIfUserland() :
                                  entryZero->IsSignaled()))
                            {
                                break;
                            }
                        }
                    }
                    else
                    {
                        if (!lsList[i]->WaitOn(uTimeoutMS))
                        {
                            break;
                        }
                    }

                    reverseList.push_back(i);
                    signaled.push_back(lsList[i]);
                }
            }

        next:
            bool bReturnStatus { true };

            if (signaled.size() != lsList.size())
            {
                bReturnStatus = false;
                signaled.clear();

                for (const auto &uIndex : reverseList)
                {
                    ResetLoopSourceFalseAlarm(lsList[uIndex]);
                }
            }

            return bReturnStatus;
        }
        else
        {
            bool bTimedout {};
            AuList<AuSPtr<Loop::ILoopSource>> signalTemp;

            auto lsList2 = lsList;
            bool bAnyFound {};

            auto DoTheThing = [&](bool bLastTick)
            {
                for (auto itr = lsList2.begin();
                     itr != lsList2.end();
                     )
                {
                    if (signalTemp.size() &&
                        uFlags & kWaitMultipleFlagBreakAfterOne)
                    {
                        break;
                    }

                    auto pSource = *itr;
                    if (!pSource)
                    {
                        signalTemp.push_back({});
                        itr = lsList2.erase(itr);
                        continue;
                    }

                    auto eType = pSource->GetType();

                    if (eType == ELoopSource::eSourceFastMutex ||
                        eType == ELoopSource::eSourceFastSemaphore ||
                        eType == ELoopSource::eSourceFastEvent)
                    {
                        auto pSourceEx = AuDynamicCast<Loop::ILoopSourceEx>(pSource);
                        
                        bAnyFound = true;

                        if ((pSourceEx && pSourceEx->IsSignaledNoSpinIfUserland()) ||
                            (!pSourceEx && pSource->IsSignaled()))
                        {
                            signalTemp.push_back(pSource);
                            itr = lsList2.erase(itr);
                        }
                        else
                        {
                            if (bLastTick && bZeroTick)
                            {
                                itr = lsList2.erase(itr);
                            }
                            else
                            {
                                itr++;
                            }
                        }
                    }
                    else
                    {
                        itr++;
                    }
                }
            };

            if (bSpin &&
                gRuntimeConfig.threadingConfig.bPlatformIsSMPProcessorOptimized &&
                !bZeroTick)
            {
                AuThreadPrimitives::DoTryIf([&]()
                {
                    DoTheThing(false);

                    if (!bAnyFound)
                    {
                        return true;
                    }

                    return bool(signalTemp.size());
                });

                if (bAnyFound)
                {
                    DoTheThing(true);
                }
            }
            else
            {
                DoTheThing(true);
            }

            bool bAllowOthers = !(uFlags & kWaitMultipleFlagBreakAfterOne);

            if (lsList2.size() &&
                (bAllowOthers || signalTemp.empty()))
            {
                bZeroTick |= bool(signalTemp.size());
                AuUInt32 uTimeoutMS {};
                
                if (uTimeoutEnd)
                {
                    auto uStartTime = Time::SteadyClockNS();
                    if (uStartTime >= uTimeoutEnd)
                    {
                        bZeroTick = true;
                    }

                    uTimeoutMS = AuNSToMS<AuInt64>(uTimeoutEnd - uStartTime);
                    if (!uTimeoutMS)
                    {
                        bZeroTick = true;
                    }
                }

                bool bTooMany {};
            #if defined(AURORA_IS_MODERNNT_DERIVED)
                if (AuBuild::kCurrentVendor == AuBuild::EVendor::eGenericMicrosoft &&
                    lsList2.size() < MAXIMUM_WAIT_OBJECTS)
                {
                    signaled = WaitMultipleOrObjects(lsList2, bZeroTick, uTimeoutMS, bAllowOthers, bTooMany);
                    bTimedout = uTimeoutEnd && uTimeoutMS && !bZeroTick ?
                        Time::SteadyClockNS() >= uTimeoutEnd :
                        false;
                }
                else
            #endif
                {
                    bTooMany = true;
                }

                if (bTooMany)
                {
                    signaled = WaitMultipleOrObjectsFallback(lsList2, uTimeoutMS, bZeroTick, bAllowOthers, bTimedout);
                    bTimedout &= !bZeroTick;
                }
            }

            signaled.insert(signaled.end(), signalTemp.begin(), signalTemp.end());

            if (bTimedout)
            {
                return false;
            }
            else
            {
                return signaled.size();
            }
        }
    }

    AuList<AuSPtr<ILoopSource>> WaitMultipleOrObjectsFallback(const AuList<AuSPtr<ILoopSource>> &objects, AuUInt32 timeout, bool bZeroTick, bool bAllowOthers, bool &bTimeout)
    {
        AuList<AuSPtr<ILoopSourceEx>> loopSourceExs;
        AuList<AuSPtr<ILoopSource>> triggered;

        if (objects.empty())
        {
            return {};
        }

        bTimeout  = false;

        auto pQueue = AuLoop::NewLoopQueue();
        if (!pQueue)
        {
            return {};
        }

        try
        {
            loopSourceExs.reserve(objects.size());
            triggered.reserve(triggered.size());

            for (const auto &source : objects)
            {
                if (!source)
                {
                    continue;
                }

                if (!pQueue->SourceAdd(source))
                {
                    return {};
                }

                if (source->GetType() == ELoopSource::eSourceWin32)
                {
                    continue;
                }

                if (auto pLoopSourceEx = AuDynamicCast<ILoopSourceEx>(source))
                {
                    if (!AuTryInsert(loopSourceExs, pLoopSourceEx))
                    {
                        return {};
                    }
                }
            }
        }
        catch (...)
        {
            return {};
        }

        auto pListener = AuMakeSharedThrow<AuLoop::ILoopSourceSubscriberFunctional>([&](const AuSPtr<ILoopSource> &source)
        {
            triggered.push_back(source);
            return false;
        });

        if (!pQueue->AddCallback(pListener))
        {
            return {};
        }

        for (const auto &source : loopSourceExs)
        {
            source->OnPresleep();
        }
       
        if (bZeroTick)
        {
            (void)pQueue->PumpNonblocking();
        }
        else
        {
            bTimeout = !pQueue->WaitAny(timeout);
        }

        for (AU_ITERATE_N(i, loopSourceExs.size()))
        {
            auto pLoopSource = loopSourceExs[i];

            if (bAllowOthers || triggered.empty())
            {
                if (std::find(triggered.begin(), triggered.end(), pLoopSource) == triggered.end())
                {
                    auto eType = pLoopSource->GetType();

                    if (eType == ELoopSource::eSourceFastMutex ||
                        eType == ELoopSource::eSourceFastSemaphore ||
                        eType == ELoopSource::eSourceFastEvent)
                    {
                        if (pLoopSource->IsSignaledNoSpinIfUserland())
                        {
                            triggered.push_back(pLoopSource);
                        }
                    }
                }
            }

            pLoopSource->OnFinishSleep();
        }

        if (!bAllowOthers && triggered.size() > 1)
        {
            for (AU_ITERATE_N_TO_X(i, 1, triggered.size()))
            {
                ResetLoopSourceFalseAlarm(triggered[i]);
            }

            return { triggered[0] };
        }
        else
        {
            return triggered;
        }
    }

    AUKN_SYM AuInt64                DbgLoopSourceToReadFd(AuSPtr<ILoopSource> pLoopSource)
    {
        if (!pLoopSource)
        {
            return -1;
        }

        auto pSourceEx = AuDynamicCast<Loop::ILoopSourceEx>(pLoopSource);
        if (!pSourceEx)
        {
            return -1;
        }

        if (!pSourceEx->Singular())
        {
            return -1;
        }

        return pSourceEx->GetHandle();
    }

    AUKN_SYM AuInt64                DbgLoopSourceToWriteFd(AuSPtr<ILoopSource> pLoopSource)
    {
        if (!pLoopSource)
        {
            return -1;
        }

        if (auto pIOHandle = AuDynamicCast<Loop::LSIOHandle>(pLoopSource))
        {
            return pIOHandle->pHandle->GetOSWriteHandleSafe().OrElse([&]()
            {
                return pIOHandle->pHandle->GetOSReadHandleSafe();
            }).ValueOr(AuUInt(-1));
        }

        auto pSourceEx = AuDynamicCast<Loop::ILoopSourceEx>(pLoopSource);
        if (!pSourceEx)
        {
            return -1;
        }

        if (!pSourceEx->Singular())
        {
            return -1;
        }

    #if defined(AURORA_IS_POSIX_DERIVED)
        return pSourceEx->GetWriteHandle();
    #else
        return pSourceEx->GetHandle();
    #endif
    }
}