/***
    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: CompletionGroup.cpp
    Date: 2023-12-28
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include <Aurora/IO/IOExperimental.hpp>
#include "CompletionGroup.hpp"
#include "CompletionGroupAndedIOWorkItem.hpp"

namespace Aurora::IO::CompletionGroup
{
    struct CompletionGroup;

    CompletionGroup::CompletionGroup() :
        anyProbablyAlwaysPresentEvent(this, false),
        andPlsDontAllocateFdIfUntouchedEvent(this, true)
    {

    }

    CompletionGroup::~CompletionGroup()
    {
        this->ResetMemoryPins();
    }

    bool CompletionGroup::HasCompleted()
    {
        return this->uTriggered == this->uAdded &&
            bool(this->uAdded);
    }

    AuPair<AuUInt32, AuUInt32> CompletionGroup::GetStats()
    {
        return AuMakePair(this->uTriggered, this->uAdded);
    }

    void CompletionGroup::SetCallbacks(const AuSPtr<ICompletionGroupHooks> &pCallbacks)
    {
        AU_LOCK_GUARD(this->mutex);
        this->pCallbacks = pCallbacks;
    }

    void CompletionGroup::ResetMemoryPins()
    {
        AuResetMember(this->pCallbacks);
        AuResetMember(this->pAnyBarrier);
        AuResetMember(this->pAndBarrier);

        for (const auto &pOld : this->workItems)
        {
            pOld->CleanupForGCWI();
        }
        
        AuResetMember(this->callbackTicks);
        this->bTerminated = true;
    }

    bool CompletionGroup::HasItemsActive()
    {
        return this->workItems.size();
    }

    void CompletionGroup::DoIOTick(bool bManual)
    {
        AuList<AuPair<AuSPtr<ICompletionGroupWorkItem>, bool>> removedItems;

        {
            AU_DEBUG_MEMCRUNCH;
            AU_LOCK_GUARD(this->mutex);

            for (auto itr = this->workItems.begin();
                 itr != this->workItems.end();
                 )
            {
                if (itr->get()->HasCompletedForGCWI())
                {
                    auto that = *itr;
                    itr = this->workItems.erase(itr);

                    this->uTriggered++;


                    if (that->HasNonTrivialCleanup())
                    {
                        removedItems.push_back(AuMakePair(that, true));
                    }
                    else if (this->pCallbacks)
                    {
                        removedItems.push_back(AuMakePair(that, false));
                        that->CleanupForGCWI();
                    }
                    else
                    {
                        that->CleanupForGCWI();
                    }
                }
                else
                {
                    itr++;
                }
            }
        }
     
        for (const auto &[pRemoved, bNonTrivial] : removedItems)
        {
            if (auto pCallbacks = this->pCallbacks)
            {
                try
                {
                    pCallbacks->OnHandleComplete(pRemoved);
                }
                catch (...)
                {
                    SysPushErrorCatch();
                }
            }

            if (bNonTrivial)
            {
                pRemoved->CleanupForGCWI();
            }
        }

        {
            AU_LOCK_GUARD(this->mutex);

            for (const auto &[pCallback, bAny] : this->callbackTicks)
            {
                if (!bAny)
                {
                    continue;
                }

                try
                {
                    pCallback->InvokeManualTick();
                }
                catch (...)
                {
                    SysPushErrorCatch();
                }
            }
        }

        if (this->workItems.empty() &&
            (bManual || !this->bIsNeverEnding))
        {
            this->andPlsDontAllocateFdIfUntouchedEvent.Set();

            if (AuExchange(this->pCallbacks, {}))
            {
                try
                {
                    this->pCallbacks->OnComplete();
                }
                catch (...)
                {
                    SysPushErrorCatch();
                }
            }

            {
                AU_LOCK_GUARD(this->mutex);

                for (const auto &[pCallback, bAny] : this->callbackTicks)
                {
                    if (bAny)
                    {
                        continue;
                    }

                    try
                    {
                        pCallback->InvokeManualTick();
                    }
                    catch (...)
                    {
                        SysPushErrorCatch();
                    }
                }
            }

            // anyone else?
            this->ResetMemoryPins();
        }

        this->TryCollectInternal();
    }

    void CompletionGroup::AddWorkItem(const AuSPtr<ICompletionGroupWorkItem> &pCompletable)
    {
        SysAssert(!this->bTerminated, "Completion group already terminated");
        AU_LOCK_GUARD(this->mutex);
        this->workItems.push_back(pCompletable);
        AuAtomicAdd(&this->uAdded, 1u);
        this->TryCreateInternal();
    }

    void CompletionGroup::UnsafeRemoveItem(const AuSPtr<ICompletionGroupWorkItem> &pCompletable)
    {
        AU_LOCK_GUARD(this->mutex);

        if (AuTryRemove(this->workItems, pCompletable))
        {
            AuAtomicAdd(&this->uTriggered, 1u);
        }
    }

    void CompletionGroup::AddCallbackTick(const AuSPtr<IIOProcessorManualInvoker> &pCallbackInvoker, bool bAny)
    {
        AU_LOCK_GUARD(this->mutex);
        this->callbackTicks.push_back(AuMakePair(pCallbackInvoker, bAny));
    }

    bool CompletionGroup::IsNeverEnding()
    {
        return this->bIsNeverEnding;
    }

    void CompletionGroup::SetNeverEnding(bool bValue)
    {
        this->bIsNeverEnding = bValue;
    }

    AuSPtr<Loop::ILoopSource> CompletionGroup::ToAndLoopSource()
    {
        return this->andPlsDontAllocateFdIfUntouchedEvent.GetLoopSource();
    }

    AuSPtr<Loop::ILoopSource> CompletionGroup::ToAnyLoopSource()
    {
        return this->anyProbablyAlwaysPresentEvent.GetLoopSource();
    }

    AuSPtr<Loop::ILSEvent> CompletionGroup::GetTriggerLoopSource()
    {
        return this->anyProbablyAlwaysPresentEvent.GetLoopSource();
    }

    void CompletionGroup::TryTriggerLater()
    {
        if (auto pEvent = GetTriggerLoopSource())
        {
            pEvent->Set();
        }
    }

    bool CompletionGroup::WaitForAnyMS(AuUInt32 uTimeoutOrZeroMS)
    {
        if (auto pLoopSource = this->ToAnyLoopSource())
        {
            return pLoopSource->WaitOn(uTimeoutOrZeroMS);
        }
        else
        {
            return false;
        }
    }

    bool CompletionGroup::WaitForAllMS(AuUInt32 uTimeoutOrZeroMS)
    {
        if (auto pLoopSource = this->ToAndLoopSource())
        {
            return pLoopSource->WaitOn(uTimeoutOrZeroMS);
        }
        else
        {
            return false;
        }
    }

    void CompletionGroup::TryTrigger()
    {
        if (auto pSource = GetTriggerLoopSource())
        {
            pSource->Set();
        }

        this->DoIOTick(true);
    }

    AuSPtr<AuAsync::IWorkItem> CompletionGroup::OnCompletion()
    {
        AU_LOCK_GUARD(this->cs);

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

        auto pWorker = AuAsync::GetCurrentWorkerPId().GetPool();
        if (!pWorker)
        {
            pWorker = AuUnsafeRaiiToShared(AuAsync::GetAsyncApp());
        }

        auto pRet = AuMakeShared<CompletionGroupAndedIOWorkItem>((AuAsync::IThreadPoolInternal *)AuStaticPointerCast<AuAsync::ThreadPool>(pWorker).get(),
                                                                 AuWorkerPId_t {}, 
                                                                 this->SharedFromThis());
        if (!pRet)
        {
            SysPushErrorMemory();
            return {};
        }

        // prevent attaching a singular loop source to a loop queue multiple times
        if (this->pAnyBarrier)
        {
            auto pEvent = this->andPlsDontAllocateFdIfUntouchedEvent.GetLoopSource();
            if (!pEvent)
            {
                return {};
            }

            pRet->SetSchedByLoopSourceOnce(pEvent)->Dispatch();
        }
        else
        {
            auto pEvent = this->anyProbablyAlwaysPresentEvent.GetLoopSource();
            if (!pEvent)
            {
                return {};
            }

            pRet->SetSchedByLoopSourceOnce(pEvent)->Dispatch();
            this->bNoAny = true;
        }

        this->pAndBarrier = pRet;
        return pRet;
    }

    void CompletionGroup::ResetAnd()
    {
        AuResetMember(this->pAndBarrier);
    }

    AuSPtr<AuAsync::IWorkItem> CompletionGroup::OnSingleCompletionIntl()
    {
        if (this->bNoAny)
        {
            SysPushErrorGeneric("To prevent double LoopQueue::SourceAdd on the same source, you must not call ::OnSingleCompletion() after ::OnCompletion() in this specific order");
            return {};
        }

        auto pRet = AuAsync::NewFence();
        if (!pRet)
        {
            SysPushErrorNested();
            return {};
        }

        pRet->SetSchedByLoopSourceRepeating(this->anyProbablyAlwaysPresentEvent.GetLoopSource())->Dispatch();
        this->pAnyBarrier = pRet;
        return pRet;
    }

    AuSPtr<AuAsync::IWorkItem> CompletionGroup::OnSingleCompletion()
    {
        AU_LOCK_GUARD(this->cs);

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

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

        if (this->workerId)
        {
            TryCreateInternal();
            return this->pAnyBarrierInternal;
        }
        else
        {
            return this->pAnyBarrier = OnSingleCompletionIntl();
        }
    }

    void CompletionGroup::TryCreateInternal()
    {
        if (!this->workerId)
        {
            return;
        }

        if (this->pAnyBarrierInternal)
        {
            return;
        }

        if (this->workerId != AuAsync::GetCurrentWorkerPId())
        {
            return;
        }

        this->pAnyBarrierInternal = OnSingleCompletionIntl();
        this->SetNeverEnding(true);

        if (auto pKernel = this->workerId.GetPool()->ToKernelWorkQueue(this->workerId))
        {
            (void)pKernel->Commit();
        }
    }

    void CompletionGroup::TryCollectInternal()
    {
        if (!this->workItems.empty())
        {
            return;
        }

        if (!this->workerId)
        {
            return;
        }

        if (!this->pAnyBarrierInternal)
        {
            return;
        }

        if (this->workerId != AuAsync::GetCurrentWorkerPId())
        {
            return;
        }

        AuResetMember(this->pAnyBarrierInternal);

        if (auto pKernel = this->workerId.GetPool()->ToKernelWorkQueue(this->workerId))
        {
            (void)pKernel->Commit();
        }
    }

    void CompletionGroup::MakeInternalAsync(AuWorkerID pid)
    {
        this->SetNeverEnding(true);
        this->workerId = pid;
    }

    AUKN_SYM AuSPtr<ICompletionGroup> NewCompletionGroup()
    {
        return AuMakeShared<CompletionGroup>();
    }
}