/***
    Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: IOProcessor.cpp
    Date: 2022-6-6
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include <Aurora/IO/IOExperimental.hpp>
#include "IOProcessorItem.hpp"
#include "IOProcessorItems.hpp"
#include "IOProcessor.hpp"
#include "IOPipeProcessor.hpp"
#include "Loop/Loop.hpp"
#include "Loop/LoopQueue.hpp"

namespace Aurora::IO
{
    IOProcessor::IOProcessor(AuUInt threadId, bool tickOnly,
                             AuAsync::WorkerPId_t worker,
                             const AuSPtr<AuLoop::ILoopQueue> &loop) :
        mutliplexIOAndTimer(!tickOnly),
        loopQueue(loop),
        asyncWorker(worker),
        threadId(threadId),
        streamProcessors(this)
    {

    }
    
    IOProcessor::~IOProcessor()
    {
        this->ReleaseAllWatches();
    }

    bool IOProcessor::Init()
    {
        if (!this->ToQueue())
        {
            return {};
        }

        if (!this->items.Init())
        {
            SysPushErrorNested();
            return false;
        }

        if (!this->timers.Init(this, AuLoop::NewLSTimer(0)))
        {
            SysPushErrorNested();
            return false;
        }

        this->ToQueue()->SourceAdd(this->items.cvEvent);

        return true;
    }

    bool IOProcessor::QueueIOEvent(const AuSPtr<IIOProcessorItem> &ioEvent)
    {
        return this->items.AddFrameOrFallback(AuStaticCast<IOProcessorItem>(ioEvent));
    }

    AuUInt32 IOProcessor::TryTick()
    {
        if (!CheckThread())
        {
            SysPushErrorGeneric("Wrong Thread");
            return 0;
        }

        AU_LOCK_GUARD(this->items.mutex);
        FrameStart();
        FrameRunThreadIO();
        FrameRunCheckLSes();

        bool bHasAlertedItems = this->items.workSignaled.size() ||
                                this->timers.nbTicker.HasPassed();

        if (!bHasAlertedItems)
        {
            ReportState(EIOProcessorEventStage::eFrameEndOfFrame);
            return 0;
        }

        return FrameRunEpilogue();
    }

    bool IOProcessor::TickForRegister(const AuSPtr<IIOProcessorItem> &ioEvent)
    {
        return this->items.AddFrameOrFallback(AuStaticCast<IOProcessorItem>(ioEvent));
    }

    void IOProcessor::TickForHack(const AuSPtr<IIOProcessorItem> &ioEvent)
    {
        SysAssert(this->TickForRegister(ioEvent));
    
        if (AuExchange(this->bScheduled_, true))
        {
            return;
        }
    
        AuStaticCast<Loop::LoopQueue>(this->loopQueue)->AddHook([that = AuSharedFromThis()]()
        {
            that->RunTick();
        });
    }

    AuUInt32 IOProcessor::TickFor(const AuSPtr<IIOProcessorItem> &ioEvent)
    {
        SysAssert(TickForRegister(ioEvent));

        if (IsTickOnly())
        {
            return 0;
        }

        if (this->bFrameStart)
        {
            return 0;
        }

        if (!CheckThread())
        {
            SysPushErrorGeneric("Wrong Thread");
            return 0;
        }


        AU_LOCK_GUARD(this->items.mutex);
        FrameStart();
        FrameRunThreadIO();
        FrameRunCheckLSes();
        return FrameRunEpilogue();
    }

    AuUInt32 IOProcessor::RunTick()
    {
        if (!CheckThread())
        {
            SysPushErrorGeneric("Wrong Thread");
            AuThreading::Sleep(1);
            return 0;
        }

        this->bScheduled_ = false;
        this->bFrameStart = false;

        AU_LOCK_GUARD(this->items.mutex);
        FrameStart();
        FrameWaitForAny(0);
        FramePumpWaitingBlocked();
        FrameRunThreadIO();
        FrameRunCheckLSes();
        return FrameRunEpilogue();
    }

    AuUInt32 IOProcessor::ManualTick()
    {
        if (!CheckThread())
        {
            SysPushErrorGeneric("Wrong Thread");
            return 0;
        }

        this->bFrameStart = false;

        AU_LOCK_GUARD(this->items.mutex);
        FrameStart();
        FrameRunThreadIO();
        FrameRunCheckLSes();
        return FrameRunEpilogue();
    }

    void IOProcessor::FrameRunIOWorkUnits()
    {
        AU_LOCK_GUARD(this->items.mutex);

        while (this->workUnits.size())
        {
            for (auto workItems : AuExchange(this->workUnits, {}))
            {
                workItems->OnRun();
            }
        }
    }

    AuUInt IOProcessor::FrameRunEpilogue()
    {
        FrameRunAlerted();
        FrameRunAlertedSniffers();
        FrameRunIOWorkUnits();
        FrameEndOfFrameEvents();
        return FrameFinalize();
    }

    void IOProcessor::FrameRunCheckLSes()
    {
        if (!this->IsTickOnly())
        {
            return;
        }

        for (auto &item : this->items.allItems)
        {
            if (item->item->IsRunOnSelfIO() && item->item->IsRunOnSelfIOCheckedOnTimerTick())
            {
                auto ls = item->item->GetSelfIOSource();
                if (ls && ls->IsSignaled())
                {
                    // Should deadlock without critical sections
                    this->QueueIOEvent(item);
                }
            }
        }
    }

    void IOProcessor::FrameRunAlerted()
    {
        for (auto &a : this->items.onTickReceivers)
        {
            if (a->listener)
            {
                try
                {
                    a->listener->Tick_RunOnTick();

                    if (!AuExists(this->items.workSignaled, a) &&
                        !AuExists(this->items.onTickReceivers, a))
                    {
                        a->listener->Tick_Any();
                    }
                }
                catch (...)
                {
                    SysPushErrorCatch();
                }
            }
            
            SysAssert(AuTryInsert(this->items.finalizeQueue, a));
        }

        for (auto &a : this->items.workSignaled)
        {
            if (a->listener)
            {
                try
                {
                    a->listener->Tick_SelfIOEvent();
                    a->listener->Tick_Any();
                }
                catch (...)
                {
                    SysPushErrorCatch();
                }
            }

            SysAssert(AuTryInsert(this->items.finalizeQueue, a));
        }
    }

    void IOProcessor::FrameRunAlertedSniffers()
    {
        if (this->items.workSignaled.empty())
        {
            return;
        }

        for (auto &a : this->items.onOtherReceivers)
        {
            if (AuExists(this->items.workSignaled, a))
            {
                continue;
            }

            if (a->listener)
            {
                try
                {
                    a->listener->Tick_OtherIOEvent();
                    a->listener->Tick_Any();
                }
                catch (...)
                {
                    SysPushErrorCatch();

                    SysAssert(a->FailWatch());
                }
            }

            this->items.finalizeQueue.push_back(a);
        }
    }

    void IOProcessor::FrameEndOfFrameEvents()
    {
        ReportState(EIOProcessorEventStage::eFrameWorkDone);

        for (auto &pumped : this->items.finalizeQueue)
        {
            if (!pumped->listener)
            {
                continue;
            }

            try
            {
                pumped->listener->Tick_FrameEpilogue();
            }
            catch (...)
            {
                SysPushErrorCatch();
                pumped->FailWatch();
            }
        }

        auto hasRemoved = this->items.crossThreadAbort.size();

        for (auto itr = this->items.crossThreadAbort.begin(); itr != this->items.crossThreadAbort.end(); )
        {
            bool fatal = itr->second;
            auto item = itr->first;

            
            this->ClearProcessor(item, fatal);
         
            itr = this->items.crossThreadAbort.erase(itr);
        }

        if (hasRemoved)
        {
            ToQueue()->Commit();
        }
    }


    void IOProcessor::ClearProcessor(const AuSPtr<IOProcessorItem> &processor, bool fatal)
    {
        if (!AuTryRemove(this->items.allItems, processor))
        {
            return;
        }

        try
        {
            if (fatal)
            {
                processor->listener->OnFailureCompletion();
            }
            else
            {
                processor->listener->OnNominalCompletion();
            }
        }
        catch (...)
        {
            SysPushErrorCatch();
        }

        auto item = processor->item;

        if (item->IsRunOnTick())
        {
            if (!AuTryRemove(this->items.onTickReceivers, processor))
            {
                SysPushErrorMem();
            }
        }

        if (item->IsRunOnOtherTick())
        {
            if (!AuTryRemove(this->items.onOtherReceivers, processor))
            {
                SysPushErrorMem();
            }
        }

        if (item->IsRunOnSelfIO())
        {
            if (!AuTryRemove(this->items.registeredIO, processor))
            {
                SysPushErrorMem();
            }

            auto src = item->GetSelfIOSource();
            if (!src)
            {
                SysPushErrorGeneric();
                return;
            }

            if (!this->ToQueue()->SourceRemove(src))
            {
                SysPushErrorNested("IO Remove Error [!!!]");
            }
        }
    }

    AuUInt IOProcessor::FrameFinalize()
    {
        auto C = this->items.finalizeQueue.size();
        this->items.workSignaled.clear();
        this->items.finalizeQueue.clear();

        ReportState(EIOProcessorEventStage::eFrameEndOfFrame);
        this->bFrameStart = false;
        return C;
    }

    bool IOProcessor::InternalIsTickReady()
    {
        // TODO: tickless io ad-hoc event-as-condvar?
        return this->items.workSignaled.size() ||
               this->items.crossThreadAbort.size();
    }

    bool IOProcessor::FrameWaitForAny(AuUInt32 msMax)
    {
        if (InternalIsTickReady())
        {
            return true;
        }

        if (this->IsTickOnly())
        {
            auto next = this->timers.nbTicker.nextTriggerTime;
            auto now = AuTime::CurrentInternalClockNS();

            if (now >= next)
            {
                return true;
            }

            auto delay = AuNSToMS<AuUInt>(next - now);

        #if 0
            if (delay == 1)
            {
                bool ret {};
                while (IO::IOYield());
            }
            else
        #endif
            {
                return IO::WaitFor(msMax ? AuMin<AuUInt32>(msMax, delay) : delay, true);
            }
        }
        else
        {
            return this->loopQueue->WaitAny(msMax);
        }
    }

    bool IOProcessor::SubmitIOWorkItem(const AuSPtr<IIOProcessorWorkUnit> &work)
    {
        AU_LOCK_GUARD(this->items.mutex); // < critical section / reentrant | can nest submission 
        return AuTryInsert(this->workUnits, work);
    }

    bool IOProcessor::AddEventListener(const AuSPtr<IIOProcessorEventListener> &eventListener)
    {
        AU_LOCK_GUARD(this->listenersSpinLock);

        return AuTryInsert(this->listeners, eventListener);
    }

    void IOProcessor::RemoveEventListener(const AuSPtr<IIOProcessorEventListener> &eventListener)
    {
        AU_LOCK_GUARD(this->listenersSpinLock);

        AuTryRemove(this->listeners, eventListener);
    }

    void IOProcessor::DispatchFrame(ProcessInfo &info)
    {
        this->ManualTick();

        auto ns = this->refreshRateNs;
        if (ns)
        {
            info = AuAsync::ETickType::eSchedule;
            info.reschedNs = ns;
        }
    }

    void IOProcessor::FramePumpWaitingBlocked()
    {
        auto blocked = this->items.GetBlockedSignals();
        if (blocked.size())
        {
            this->items.workSignaled.insert(this->items.workSignaled.end(), blocked.begin(), blocked.end());
        }
    }

    void IOProcessor::FrameStart()
    {
        ReportState(EIOProcessorEventStage::eFrameStartOfFrame);
        this->bFrameStart = true;

        FramePumpWaitingBlocked();
    }

    void IOProcessor::FrameRunThreadIO()
    {
        ReportState(EIOProcessorEventStage::eFrameYieldIO);
        while (IO::IOYield());
        ReportState(EIOProcessorEventStage::eFrameIODone);
    }

    AuUInt64 IOProcessor::SetRefreshRate(AuUInt64 ns)
    {
        if (!CheckThread())
        {
            AU_THROW_STRING("Wrong Thread");
        }

        bool changed = bool(ns) != bool(this->refreshRateNs);

        auto old = AuExchange(this->refreshRateNs, ns);

        UpdateTimers();

        if (changed)
        {
            if (ns)
            {
                AddTimer();
            }
            else
            {
                RemoveTimer();
            }
        }

        return old;
    }

    bool IOProcessor::HasRefreshRate()
    {
        return bool(this->refreshRateNs);
    }

    bool IOProcessor::MultiplexRefreshRateWithIOEvents()
    {
        return this->mutliplexIOAndTimer;
    }

    AuUInt64 IOProcessor::GetOwnedThreadId()
    {
        return this->threadId;
    }

    void IOProcessor::UpdateTimers()
    {
        this->timers.lsTicker->UpdateTickRateIfAnyNs(this->refreshRateNs);
        this->timers.nbTicker.nsTimeStep = this->refreshRateNs;

        if (!this->timers.nbTicker.nextTriggerTime)
        {
            this->timers.nbTicker.nextTriggerTime = AuTime::CurrentInternalClockNS() + this->timers.nbTicker.nsTimeStep;
        }
    }

    void IOProcessor::AddTimer()
    {
        if (IsAsync())
        {
            StartAsyncTimerIfAny();
        }
        else
        {
            AddTimerLS();
        }
    }

    void IOProcessor::AddTimerLS()
    {
        this->ToQueue()->SourceAdd(this->timers.lsTicker);
        this->ToQueue()->AddCallback(this->timers.lsTicker, AuSPtr<AuLoop::ILoopSourceSubscriber>(AuSharedFromThis(), &this->timers));
        this->ToQueue()->Commit();
    }

    void IOProcessor::StartAsyncTimerIfAny()
    {
        if (!this->workItem)
        {
            this->workItem = this->asyncWorker.pool->NewWorkItem(this->asyncWorker, AuSharedFromThis());
        }

        this->workItem->SetSchedTimeNs(this->refreshRateNs);

        this->workItem->Dispatch();
    }

    void IOProcessor::RemoveTimer()
    {
        if (IsAsync())
        {
            CancelWorkItem();
        }
        else
        {
            RemoveLSTimer();
        }
    }

    void IOProcessor::CancelWorkItem()
    {
        if (!this->workItem)
        {
            return;
        }

        this->workItem->Cancel();
        this->workItem.reset();
    }

    void IOProcessor::RemoveLSTimer()
    {
        auto queue = this->ToQueue();
        if (!queue)
        {
            return;
        }

        queue->SourceRemove(this->timers.lsTicker);
    }

    bool IOProcessor::IsAsync()
    {
        return bool(this->asyncWorker.pool);
    }

    bool IOProcessor::IsTickOnly()
    {
        return !this->mutliplexIOAndTimer &&
                this->timers.nbTicker.nextTriggerTime;
    }

    bool IOProcessor::RequestRemovalForItemFromAnyThread(const AuSPtr<IIOProcessorItem> &processor)
    {
        return {};
    }


    AuSPtr<IIOProcessorItem> IOProcessor::StartIOWatchEx(const AuSPtr<IIOWaitableItem>& object, const AuSPtr<IIOEventListener>& listener, bool singleshot)
    {
        if (!CheckThread())
        {
            AU_THROW_STRING("Wrong Thread");
        }

        auto item = AuMakeShared<IOProcessorItem>();
        item->parent = this;
        item->listener = listener;
        item->item = object;
        item->singleshot = singleshot;

        AU_LOCK_GUARD(this->items.mutex);

        this->items.allItems.push_back(item);

        if (object->IsRunOnTick())
        {
            if (!AuTryInsert(this->items.onTickReceivers, item))
            {
                SysPushErrorMem();
                return {};
            }
        }

        if (object->IsRunOnOtherTick())
        {
            if (!AuTryInsert(this->items.onOtherReceivers, item))
            {
                SysPushErrorMem();
                return {};
            }
        }

        if (object->IsRunOnSelfIO())
        {
            auto src = object->GetSelfIOSource();
            if (!src)
            {
                SysPushErrorGeneric();
                return {};
            }

            auto timeout = object->IOTimeoutInMS();
            if (timeout)
            {
                if (!this->ToQueue()->SourceAddWithTimeout(src, timeout))
                {
                    SysPushErrorNested("IO Error");
                    return {};
                }
            }
            else
            {
                if (!this->ToQueue()->SourceAdd(src))
                {
                    SysPushErrorNested("IO Error");
                    return {};
                }
            }

            if (!this->ToQueue()->AddCallbackEx(src, item))
            {
                SysPushErrorNested("IO Error");
                SysAssert(this->ToQueue()->SourceRemove(src));
                return {};
            }

            if (!this->ToQueue()->Commit())
            {
                SysPushErrorIO("midframe recommit");
            }

            if (!AuTryInsert(this->items.registeredIO, item))
            {
                SysPushErrorMem();
                SysAssert(this->ToQueue()->SourceRemove(src));
                return {};
            }
        }

        return item;
    }
    
    AuSPtr<IIOProcessorItem> IOProcessor::StartSimpleIOWatchEx(const AuSPtr<IIOWaitableItem>& object, const AuSPtr<IIOSimpleEventListener>& listener, bool singleshot)
    {
        auto adapter = DesimplifyIOEventListenerAdapter(listener);
        if (!adapter)
        {
            SysPushErrorMem();
            return {};
        }

        return this->StartIOWatchEx(object, adapter, singleshot);
    }

    AuSPtr<IIOProcessorItem> IOProcessor::StartSimpleLSWatchEx(const AuSPtr<Loop::ILoopSource>& source, const AuSPtr<IIOSimpleEventListener>& listener, bool singleshot, AuUInt32 msTimeout)
    {
        auto sourceAdapter = NewWaitableLoopSourceEx(source, msTimeout);
        if (!sourceAdapter)
        {
            SysPushErrorMem();
            return {};
        }

        return this->StartSimpleIOWatchEx(sourceAdapter, listener, singleshot);
    }

    AuSPtr<IIOProcessorItem> IOProcessor::StartIOWatch(const AuSPtr<IIOWaitableItem> &object, const AuSPtr<IIOEventListener> &listener)
    {
        return StartIOWatchEx(object, listener, false);
    }

    AuSPtr<IIOProcessorItem> IOProcessor::StartSimpleIOWatch(const AuSPtr<IIOWaitableItem> &object, const AuSPtr<IIOSimpleEventListener> &listener)
    {
        return this->StartSimpleIOWatchEx(object, listener, false);
    }

    AuSPtr<IIOProcessorItem> IOProcessor::StartSimpleLSWatch(const AuSPtr<Loop::ILoopSource> &source, const AuSPtr<IIOSimpleEventListener> &listener)
    {
        return this->StartSimpleLSWatchEx(source, listener, false, 0);
    }

    AuSPtr<IIOPipeProcessor> IOProcessor::ToPipeProcessor()
    {
        if (!CheckThread())
        {
            AU_THROW_STRING("Wrong Thread");
        }

        return AuSPtr<IIOPipeProcessor>(AuSharedFromThis(), &this->streamProcessors);
    }

    AuSPtr<AuLoop::ILoopQueue> IOProcessor::ToQueue()
    {
        return this->loopQueue;
    }

    void IOProcessor::ReleaseAllWatches()
    {
        RemoveTimer();
        auto queue = ToQueue();
        if (queue)
        {
            if (this->items.cvEvent)
            {
                queue->SourceRemove(this->items.cvEvent);
            }

            for (auto &io : this->items.registeredIO)
            {
                queue->SourceRemove(io->item->GetSelfIOSource());
            }

            queue->Commit();
        }
    }

    bool IOProcessor::HasItems()
    {
        return bool(this->items.allItems.size());
    }

    void IOProcessor::ReportState(EIOProcessorEventStage stage)
    {
        AU_LOCK_GUARD(this->listenersSpinLock);
        
        for (auto &listeners : this->listeners)
        {
            try
            {
                listeners->OnIOProcessorStateEvent(stage);
            }
            catch (...)
            {
                SysPushErrorCatch();
            }
        }
    }

    bool IOProcessor::CheckThread()
    {
        if (this->threadId == 0)
        {
            this->threadId = AuThreads::GetThreadId();
            return true;
        }

        return this->threadId == AuThreads::GetThreadId();
    }

    AUKN_SYM AuSPtr<IIOProcessor> NewIOProcessor(bool tickOnly, const AuSPtr<AuLoop::ILoopQueue> &queue)
    {
        auto processor = AuMakeShared<IOProcessor>(0, tickOnly, AuAsync::WorkerPId_t {}, queue);
        if (!processor)
        {
            SysPushErrorMem();
            return {};
        }

        if (!processor->Init())
        {
            SysPushErrorNested();
            return {};
        }

        return processor;
    }

    AUKN_SYM AuSPtr<IIOProcessor> NewIOProcessorOnThread(bool tickOnly, Async::WorkerPId_t id)
    {
        if (!id.pool)
        {
            return {};
        }

        auto thread = id.pool->ResolveHandle(id);
        if (!thread)
        {
            SysPushErrorGeneric("Worker PID failed to resolve to a thread object");
            return {};
        }

        auto queue = id.pool->ToKernelWorkQueue(id);
        if (!queue)
        {
            SysPushErrorGeneric("Worker PID has no kernel work queue");
            return {};
        }

        auto processor = AuMakeShared<IOProcessor>(AuUInt(thread.get()), tickOnly, id, queue);
        if (!processor)
        {
            SysPushErrorMem();
            return {};
        }

        if (!processor->Init())
        {
            SysPushErrorNested();
            return {};
        }

        return processor;
    }

    AUKN_SYM AuSPtr<IIOProcessor> NewIOProcessorNoQueue(bool tickOnly)
    {
        auto loop = AuLoop::NewLoopQueue();
        if (!loop)
        {
            SysPushErrorMem();
            return {};
        }

        return NewIOProcessor(tickOnly, loop);
    }
}