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

    File: Schedular.cpp
    Date: 2021-6-26
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Async.hpp"
#include "Schedular.hpp"
//#include "AsyncApp.hpp"
#include "ThreadPool.hpp"
#include <Console/Commands/Commands.hpp>

namespace Aurora::Async
{
    struct SchedEntry
    {
        AuUInt64 ns;
        WorkerId_t target;
        AuSPtr<IAsyncRunnable> runnable;
        IThreadPoolInternal *pool;
    };

    static AuThreads::ThreadUnique_t gThread;
    static AuThreadPrimitives::MutexUnique_t gSchedLock;
    static AuWorkerPId_t gMainThread;
    static bool gBOriginal;
    static AuList<SchedEntry> gEntries;
    
    void StartSched2();

    static void GetDispatchableTasks(AuList<SchedEntry> &pending)
    {
        AU_LOCK_GUARD(gSchedLock);

        auto time = Time::CurrentClockNS();

        for (auto itr = gEntries.begin(); itr != gEntries.end(); )
        {
            if (itr->ns <= time)
            {
                if (!AuTryInsert(pending, *itr))
                {
                    break;
                }

                itr = gEntries.erase(itr);
            }
            else
            {
                itr ++;
            }
        }
    }

    static bool gLockedPump = false;

    static void PumpSysThread()
    {
        try
        {
            RuntimeSysPump();
        }
        catch (...)
        {
            SysPushErrorCatch("SysPump failed");
        }
        gLockedPump = false;
    }

    static void SchedThread()
    {
        AuUInt32 counter {};
        AuList<SchedEntry> pending;
        
        auto thread = AuThreads::GetThread();

        while (!thread->Exiting())
        {
            AuList<SchedEntry> pending;

            Threading::SleepNs(1000000 / 2 * gRuntimeConfig.async.schedularFrequency);

            GetDispatchableTasks(pending);

            for (auto &entry : pending)
            {
                try
                {
                    entry.pool->Run(entry.target, entry.runnable);
                    entry.pool->DecrementTasksRunning();
                }
                catch (...)
                {
                    if (entry.pool->ToThreadPool()->InRunnerMode())
                    {
                        AuLogWarn("Dropped scheduled task! Expect a leaky counter!");
                        AuLogWarn("Would you rather `Why u no exit?!` or a spurious crash in production?");
                    }
                    Debug::PrintError();
                }
            }

            counter++;

            if (gRuntimeConfig.async.enableSysPumpFreqnecy)
            {

                if ((!gRuntimeConfig.async.sysPumpFrequency) || ((gRuntimeConfig.async.sysPumpFrequency) && (counter % gRuntimeConfig.async.sysPumpFrequency) == 0))
                {
                    try
                    {
                        if (!AuExchange(gLockedPump, true))
                        {
                            NewWorkItem(gMainThread, AuMakeShared<BasicWorkStdFunc>(PumpSysThread))->Dispatch();
                        }
                    }
                    catch (...)
                    {
                        AuLogWarn("Dropped SysRuntimePump");
                        Debug::PrintError();
                    }
                }
            }
        }
    }

    void InitSched()
    {
        gSchedLock = AuThreadPrimitives::MutexUnique();
    }

    void DeinitSched()
    {
        gThread.reset();
        gSchedLock.reset();
    }

    AUKN_SYM void SetMainThreadForSysPumpScheduling(AuWorkerPId_t pid)
    {
        if (!pid)
        {
            gRuntimeConfig.async.enableSysPumpFreqnecy = gBOriginal;
            gMainThread = AuWorkerPId_t(AuAsync::GetSharedAsyncApp(), AuWorkerId_t {0, 0});
            Console::Commands::UpdateDispatcher(gMainThread);

            return;
        }

        gMainThread = pid;
        Console::Commands::UpdateDispatcher(gMainThread);
        gRuntimeConfig.async.enableSysPumpFreqnecy = true;

        StartSched2();
    }

    void StartSched()
    {
        if (!gRuntimeConfig.async.enableSchedularThread)
        {
            return;
        }
        else
        {
            if (gRuntimeConfig.async.sysPumpFrequency && !gMainThread)
            {
                gMainThread = AuWorkerPId_t(AuAsync::GetSharedAsyncApp(), AuWorkerId_t {0, 0});
            }
        }

        StartSched2();
    }

    void StartSched2()
    {
        AU_LOCK_GUARD(gSchedLock);

        if (gThread) return;

        gBOriginal = gRuntimeConfig.async.enableSysPumpFreqnecy;

        gThread = AuThreads::ThreadUnique(AuThreads::ThreadInfo(
            AuMakeShared<AuThreads::IThreadVectorsFunctional>(AuThreads::IThreadVectorsFunctional::OnEntry_t(std::bind(SchedThread)),
            AuThreads::IThreadVectorsFunctional::OnExit_t {})
        ));

        gThread->Run();
    }

    void StopSched()
    {
        gThread.reset();
    }

    bool Schedule(AuUInt64 ns, IThreadPoolInternal *pool, WorkerId_t target, AuSPtr<IAsyncRunnable> runnable)
    {
        // TODO (Reece): urgent
        if (!gSchedLock)
        {
            return false;
        }
        AU_LOCK_GUARD(gSchedLock);
        pool->IncrementTasksRunning();
        return AuTryInsert(gEntries, SchedEntry {ns, target, runnable, pool});
    }

    void TerminateSceduledTasks(IThreadPoolInternal *pool, WorkerId_t target)
    {
        if (!gSchedLock)
        {
            SysAssert(gEntries.empty());
            return;
        }

        AU_LOCK_GUARD(gSchedLock);

        for (auto itr = gEntries.begin(); itr != gEntries.end(); )
        {
            if ((itr->pool == pool) &&
                ((itr->target == target) || (target.second == Async::kThreadIdAny && target.first == itr->target.first)))
            {
                itr->runnable->CancelAsync();
                itr = gEntries.erase(itr);
            }
            else
            {
                itr ++;
            }
        }
    }
}