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

    File: AuIOThreadPool.cpp
    Date: 2024-2-25
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuIOThreadPool.hpp"

namespace Aurora::IO::Async
{
    static AuMutex gMutex;
    static AuAsync::WorkerPId_t gDefaultGroup;
    static AuSPtr<AuAsync::IThreadPool> gThreadPool;
    static AuList<AuWPtr<AuAsync::IThreadPool>> gWorkersRegistered;
    static AuUInt gJobRunners = 0;
    static bool bOwnsThreadPool { true };

    static AuUInt32 GetDefaultThreadCount()
    {
        AuUInt32 uRet {};

        // TODO: gJobRunners = runtime config?

        if (!uRet)
        {
            uRet = AuClamp(AuHWInfo::GetCPUInfo().uThreads / 3, 2, 8);
        }

        return uRet;
    }

    AUKN_SYM void UseSpecifiedWorkerGroup(AuAsync::WorkerPId_t worker)
    {
        AU_LOCK_GLOBAL_GUARD(gMutex);
        gDefaultGroup = worker;
        bOwnsThreadPool = false;
    }

    AUKN_SYM AuUInt32 GetSpawnedThreads()
    {
        return bOwnsThreadPool ? gJobRunners : 0;
    }

    AUKN_SYM AuUInt32 SpawnMoreThreads(AuUInt32 uRequest)
    {
        AU_LOCK_GLOBAL_GUARD(gMutex);

        AuUInt32 ret {};
        AuUInt32 uStartOffset {};

        if (uRequest > 64)
        {
            return 0;
        }

        if (!bOwnsThreadPool)
        {
            return 0;
        }

        if (!gThreadPool)
        {
            gThreadPool = AuAsync::NewThreadPool();
            if (!gThreadPool)
            {
                return 0;
            }

            uRequest += (uStartOffset = GetDefaultThreadCount());
        }

        {
            AuAsync::WorkerPId_t workerId { gThreadPool, 0, AuAsync::kThreadIdAny };

            auto uMax = AuClamp<AuUInt>(gJobRunners + uRequest, 0, 255);

            for (AU_ITERATE_N_TO_X(i, gJobRunners, uMax))
            {
                AuAsync::WorkerPId_t copy = workerId;
                copy.second = i;

                if (!gThreadPool->Spawn(copy))
                {
                    break;
                }

                ret++;
            }
        }

        gJobRunners += ret;
        return ret - uStartOffset;
    }

    static AuAsync::WorkerPId_t SpawnDefaultGroup()
    {
        AuAsync::WorkerPId_t ret;

        gJobRunners = GetDefaultThreadCount();

        gThreadPool = AuAsync::NewThreadPool();
        if (!gThreadPool)
        {
            return {};
        }

        ret = { gThreadPool, 0, AuAsync::kThreadIdAny };

        for (AU_ITERATE_N(i, gJobRunners))
        {
            AuAsync::WorkerPId_t copy = ret;
            copy.second = i;

            if (!gThreadPool->Spawn(copy))
            {
                if (i > 1)
                {
                    return ret;
                }
                else
                {
                    return {};
                }
            }
        }

        return ret;
    }

    static AuAsync::WorkerPId_t GetAuxWorkerPool()
    {
        if (gDefaultGroup)
        {
            return gDefaultGroup;
        }
        else
        {
            return gDefaultGroup = SpawnDefaultGroup();
        }
    }

    AuAsync::WorkerPId_t GetAuxWorkerPoolAndRegister()
    {
        AU_LOCK_GLOBAL_GUARD(gMutex);

        if (auto worker = GetAuxWorkerPool())
        {
            if (auto selfWorker = AuAsync::GetCurrentWorkerPId())
            {
                if (gWorkersRegistered.size() > 10)
                {
                    AuRemoveAllIf(gWorkersRegistered, [](AuWPtr<AuAsync::IThreadPool> wpThat)
                    {
                        return wpThat.expired();
                    });
                }

                for (const auto &wpThat : gWorkersRegistered)
                {
                    if (auto pThat = AuTryLockMemoryType(wpThat))
                    {
                        if (pThat == selfWorker.GetPool())
                        {
                            return worker;
                        }
                    }
                }

                gWorkersRegistered.push_back(selfWorker.GetPool());
                selfWorker.GetPool()->AddDependency(worker.GetPool());
            }

            return worker;
        }
        else
        {
            SysPanic("No async threadpool");
        }
    }
}