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#include "scheduler.h"

#include <util/datetime/base.h>
#include <util/generic/algorithm.h>
#include <util/generic/yexception.h>

//#include "dummy_debugger.h"
 
using namespace NBus; 
using namespace NBus::NPrivate; 

class TScheduleDeadlineCompare {
public:
    bool operator()(const IScheduleItemAutoPtr& i1, const IScheduleItemAutoPtr& i2) const noexcept {
        return i1->GetScheduleTime() > i2->GetScheduleTime(); 
    }
};

TScheduler::TScheduler()
    : StopThread(false) 
    , Thread([&] { this->SchedulerThread(); })
{
}

TScheduler::~TScheduler() {
    Y_VERIFY(StopThread, "state check");
}

size_t TScheduler::Size() const {
    TGuard<TLock> guard(Lock);
    return Items.size() + (!!NextItem ? 1 : 0);
}

void TScheduler::Stop() {
    { 
        TGuard<TLock> guard(Lock); 
        Y_VERIFY(!StopThread, "Scheduler already stopped");
        StopThread = true; 
        CondVar.Signal(); 
    } 
    Thread.Get(); 

    if (!!NextItem) {
        NextItem.Destroy();
    }

    for (auto& item : Items) {
        item.Destroy();
    }
}

void TScheduler::Schedule(TAutoPtr<IScheduleItem> i) {
    TGuard<TLock> lock(Lock); 
    if (StopThread) 
        return;
 
    if (!!NextItem) { 
        if (i->GetScheduleTime() < NextItem->GetScheduleTime()) { 
            DoSwap(i, NextItem); 
        } 
    }
 
    Items.push_back(i);
    PushHeap(Items.begin(), Items.end(), TScheduleDeadlineCompare()); 
 
    FillNextItem(); 
 
    CondVar.Signal(); 
}

void TScheduler::FillNextItem() { 
    if (!NextItem && !Items.empty()) { 
        PopHeap(Items.begin(), Items.end(), TScheduleDeadlineCompare()); 
        NextItem = Items.back(); 
        Items.erase(Items.end() - 1); 
    } 
} 
 
void TScheduler::SchedulerThread() {
    for (;;) { 
        IScheduleItemAutoPtr current; 
 
        {
            TGuard<TLock> guard(Lock); 
 
            if (StopThread) { 
                break; 
            }
 
            if (!!NextItem) { 
                CondVar.WaitD(Lock, NextItem->GetScheduleTime()); 
            } else { 
                CondVar.WaitI(Lock); 
            }
 
            if (StopThread) { 
                break; 
            } 
 
            // signal comes if either scheduler is to be stopped of there's work to do 
            Y_VERIFY(!!NextItem, "state check");
 
            if (TInstant::Now() < NextItem->GetScheduleTime()) { 
                // NextItem is updated since WaitD 
                continue; 
            } 
 
            current = NextItem.Release();
        }
 
        current->Do(); 
        current.Destroy(); 
 
        { 
            TGuard<TLock> guard(Lock); 
            FillNextItem(); 
        } 
    }
}