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

    File: AuCoreLoadSampler.cpp
    Date: 2023-12-30
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuCoreLoadSampler.hpp"

namespace Aurora::HWInfo
{

    static CoreLoadSamplerImpl gDefaultCoreUsageSampler(AuSToMS<AuUInt32>(1), true);

    CoreLoadSamplerImpl::CoreLoadSamplerImpl(AuUInt32 uMinSamplePeriodMS,
                                           bool bCountKernelUsage) :
        uMinSamplePeriod(uMinSamplePeriodMS),
        bCountKernelUsage(bCountKernelUsage)
    {

    }

    CoreLoadSamplerImpl::~CoreLoadSamplerImpl()

    {

    }

    double CoreLoadSamplerImpl::GetCoreLoad(AuUInt8 uCore)
    {
        return this->state.GetLoad(this->uMinSamplePeriod,
                                   uCore,
                                   this->bCountKernelUsage);
    }

    double CoreLoadSamplerImpl::GetCoreLoadCached(AuUInt8 uCore)
    {
        if (uCore >= AuArraySize(this->state.dCurrentLoad))
        {
            return 0.0f;
        }

        return this->state.dCurrentLoad[uCore];
    }

    double CoreLoadSamplerImpl::GetTotalLoad()
    {
        (void)this->GetCoreLoad(0);
        return this->GetTotalLoadCached();
    }

    double  CoreLoadSamplerImpl::GetTotalLoadCached()
    {
        return this->state.dCurrentLoadAll;
    }

    double CoreLoadSamplerState::GetLoad(AuUInt32 uMinSamplePeriod,
                                         AuUInt8 uThread,
                                         bool bCountKernelUsage)
    {
        AuUInt64 uCurrentTimes[256] {};
        AuUInt64 uNow {};
        double dDeltaCore[256];
        double dAverage {}, dDeltaSteady {};
        AuList<CpuCoreTime> times;
        double dUsage[256] { 0.0f };
        double dMinSamplePeriod = double(AuMSToNS<AuUInt64>(uMinSamplePeriod));

        if (!GetPerCoreCPUTime(times))
        {
            return 0;
        }

        uNow         = AuTime::SteadyClockNS();
        dDeltaSteady = uNow - this->uPrevSteadyTime;

        if (!this->uCount)
        {
            auto uThreads = GetCPUInfo().uThreads;
            this->uCount = AuMin(uThreads, AuArraySize(uCurrentTimes));
            this->uCount = AuMin(this->uCount, times.size());
        }

        for (AU_ITERATE_N(i, this->uCount))
        {
            if (times.size() > i)
            {
                if (bCountKernelUsage)
                {
                    uCurrentTimes[i] = times[i].uUptime;
                }
                else
                {
                    uCurrentTimes[i] = times[i].uUserTime;
                }
            }
            dDeltaCore[i] = uCurrentTimes[i] - this->uPrevTimes[i];
        }

        if (!bool(this->uPrevSteadyTime))
        {
            this->uPrevSteadyTime = uNow;
            AuMemcpy(this->uPrevTimes, uCurrentTimes, sizeof(uCurrentTimes));
            return 0;
        }

        if (!uMinSamplePeriod ||
            (dDeltaSteady >= dMinSamplePeriod))
        {
            AuMemcpy(this->uPrevTimes, uCurrentTimes, sizeof(uCurrentTimes));
            this->uPrevSteadyTime = uNow;
            this->bSet = true;

            for (AU_ITERATE_N(i, this->uCount))
            {
                dUsage[i] = dDeltaCore[i] / dDeltaSteady;

                if (uMinSamplePeriod)
                {
                    if (dUsage[i] > AuNumericLimits<double>::epsilon() &&
                        this->dPrevLoad[i] > AuNumericLimits<double>::epsilon())
                    {
                        dUsage[i] = AuMin(dUsage[i], dUsage[i] + this->dPrevLoad[i] / 2.0);
                    }
                    else
                    {
                        dUsage[i] = AuMax(this->dPrevLoad[i] / 2.0, 0.0001);
                    }
                }
                else if (!dUsage[i])
                {
                    dUsage[i] = AuMax(this->dPrevLoad[i] / 2.0, 0.0001);
                }

                this->dPrevLoad[i] = dUsage[i];
            }
        }
        else
        {
            for (AU_ITERATE_N(i, this->uCount))
            {
                if (dDeltaCore[i])
                {
                    dUsage[i] = dDeltaCore[i] / dDeltaSteady;

                    if (this->bSet)
                    {
                    #if 0
                        dUsage[i] *= dDeltaSteady / double(dMinSamplePeriod);
                        if (this->dPrevLoad[i]) dUsage[i] = dUsage[i] + this->dPrevLoad[i] / 2.0;
                    #else
                        if (this->dPrevLoad[i])
                        {
                            auto dFrameDelta = dDeltaSteady / dMinSamplePeriod;
                            auto dFrameDeltaInverse = 1.0 - dFrameDelta;
                            dUsage[i] *= dFrameDelta;
                            dUsage[i] += this->dPrevLoad[i] * dFrameDeltaInverse;
                        }
                        else
                        {
                            dUsage[i] *= dDeltaSteady / dMinSamplePeriod;
                        }
                    #endif
                    }
                }
                else
                {
                    dUsage[i] = this->dPrevLoad[i];
                }
            }
        }

        for (AU_ITERATE_N(i, this->uCount))
        {
            dUsage[i] = dUsage[i] * 100.0;

            if (dUsage[i] > 100.0)
            {
                dUsage[i] = 100.0;
            }
            else if (dUsage[i] < 0.0)
            {
                dUsage[i] = 0.0;
            }

            dAverage += dUsage[i];
        }

        dAverage /= this->uCount;

        this->dCurrentLoadAll = dAverage;
        AuMemcpy(this->dCurrentLoad, dUsage, sizeof(dUsage));

        if (uThread >= AuArraySize(dUsage))
        {
            return 0;
        }
        else
        {
            return dUsage[uThread];
        }
    }

    double *CoreLoadSamplerImpl::GetCoreLoadsCached(AuUInt32 *pOut)
    {
        if (!this->state.uCount ||
            !pOut)
        {
            return nullptr;
        }

        *pOut = this->state.uCount;
        return this->state.dCurrentLoad;
    }

    AUKN_SYM ICoreLoadSampler *CoreLoadSamplerNew(AuUInt32 uMinSamplePeriodMS,
                                                  bool bCountKernelUsage)
    {
        return _new CoreLoadSamplerImpl(uMinSamplePeriodMS,  bCountKernelUsage);
    }

    AUKN_SYM void CoreLoadSamplerRelease(ICoreLoadSampler *pSampler)
    {
        AuSafeDelete<CoreLoadSamplerImpl *>(pSampler);
    }

    AUKN_SYM ICoreLoadSampler *GetDefaultCoreLoadSampler()
    {
        return &gDefaultCoreUsageSampler;
    }
}