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

    File: LSTimer.Linux.cpp
    Date: 2021-10-1
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "LSTimer.hpp"
#include "LSFromFdNonblocking.hpp"
#include <Source/Time/Time.hpp>
#include <sys/timerfd.h>

namespace Aurora::Loop
{
    
    struct LSTimer : ITimer, LSHandle
    {
        LSTimer(AuUInt32 reschedStepMsOrZero, AuUInt32 maxIterationsOrZero, int handle);
        ~LSTimer();

        virtual void UpdateTime(AuUInt64 absTimeMs) override;
        virtual void UpdateTickRateIfAny(AuUInt32 reschedStepMsOrZero, AuUInt32 maxIterationsOrZero) override;
        virtual void Stop() override;

        virtual bool OnTrigger(AuUInt handle) override;

        virtual bool IsSignaled() override;
        virtual bool WaitOn(AuUInt32 timeout) override;
        virtual ELoopSource GetType() override;

        void UpdateTimeInternal(AuUInt64 absTimeMs);

    private:
        AuUInt32 reschedStepMsOrZero_ {}, maxIterationsOrZero_ {};
        AuUInt64 targetTime_ {};
        AuUInt32 count_ {};

        bool IsSignaledNonblocking();

    };

    LSTimer::LSTimer(AuUInt32 reschedStepMsOrZero, AuUInt32 maxIterationsOrZero, int handle) :
        LSHandle(handle),
        reschedStepMsOrZero_(reschedStepMsOrZero),
        maxIterationsOrZero_(maxIterationsOrZero)
    {
        this->targetTime_ = AuTime::CurrentClockMS();
    }

    LSTimer::~LSTimer()
    {
        if ((this->handle != 0) &&
            (this->handle != -1))
        {
            ::close(AuExchange(this->handle, -1));
        }
    }

    void LSTimer::UpdateTime(AuUInt64 absTimeMs)
    {
        this->targetTime_ = absTimeMs;
        UpdateTimeInternal(this->targetTime_);
    }

    void LSTimer::UpdateTimeInternal(AuUInt64 absTimeMs)
    {
        this->targetTime_ = absTimeMs;

        itimerspec spec {};
        AuTime::auabsms2ts(&spec.it_value, this->targetTime_);
        AuTime::ms2ts(&spec.it_interval, this->reschedStepMsOrZero_);
        SysAssert(::timerfd_settime(this->handle, TFD_TIMER_ABSTIME, &spec, nullptr) == 0);
    }

    void LSTimer::UpdateTickRateIfAny(AuUInt32 reschedStepMsOrZero, AuUInt32 maxIterationsOrZero)
    {
        this->reschedStepMsOrZero_ = reschedStepMsOrZero;
        this->maxIterationsOrZero_ = maxIterationsOrZero;
        this->count_ = 0;
        this->UpdateTime(this->targetTime_);
    }
    
    bool LSTimer::OnTrigger(AuUInt handle)
    {
        return IsSignaledNonblocking();
    }

    void LSTimer::Stop()
    {
        itimerspec spec {};
        SysAssert(::timerfd_settime(this->handle, 0, &spec, nullptr) == 0);
    }

    bool LSTimer::IsSignaled()
    {
        return IsSignaledFromNonblockingImpl(this, this, &LSTimer::IsSignaledNonblocking);
    }

    bool LSTimer::WaitOn(AuUInt32 timeout)
    {
        return LSHandle::WaitOn(timeout);
    }

    ELoopSource LSTimer::GetType()
    {
        return ELoopSource::eSourceTimer;
    }

    bool LSTimer::IsSignaledNonblocking()
    {
        AuUInt64 oldSemaphoreValue {};
        auto ok = ::read(this->handle, &oldSemaphoreValue, sizeof(oldSemaphoreValue)) == 8;
        if (ok && this->maxIterationsOrZero_)
        {
            ok = AuAtomicAdd<AuUInt32>(&this->count_, 1) <= this->maxIterationsOrZero_;
            if (ok)
            {
                // fall through
            }
            else
            {
                Stop();
                return false;
            }
        }

        if (ok && !this->reschedStepMsOrZero_)
        {
            // Ensure non-step timers remain signaled despite the read above us caneling them
            this->UpdateTime(this->targetTime_);
        }
        return ok;
    }

    AUKN_SYM AuSPtr<ITimer> NewLSTimer(AuUInt64 absStartTimeMs, AuUInt32 reschedStepMsOrZero, AuUInt32 maxIterationsOrZero)
    {
        int fd = timerfd_create(CLOCK_REALTIME, TFD_NONBLOCK);
        if (fd == -1)
        {
            SysPushErrorIO();
            return {};
        }

        auto object = AuMakeShared<LSTimer>(reschedStepMsOrZero, maxIterationsOrZero, fd);
        if (!object)
        {
            SysPushErrorMem();
            ::close(fd);
            return {};
        }

        object->UpdateTime(absStartTimeMs);

        return object;
    }
}