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

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

namespace Aurora::Async
{
    WorkItem::WorkItem(const DispatchTarget_t &worker, const AuSPtr<IWorkItemHandler> &task, bool supportsBlocking) : worker_(worker), task_(task)
    {
        if (supportsBlocking)
        {
            finishedEvent_ = Threading::Primitives::EventUnique(false, true, true);
            SysAssert(finishedEvent_ ? true : false);
        }
    }

    WorkItem::~WorkItem()
    {
        //Fail();
    }

    AuSPtr<IWorkItem> WorkItem::WaitFor(const AuSPtr<IWorkItem> &workItem)
    {
        bool status {};

        {
            auto dependency = std::reinterpret_pointer_cast<WorkItem>(workItem);

            AU_LOCK_GUARD(lock);
            AU_LOCK_GUARD(dependency->lock);

            if (dependency->HasFailed())
            {
                status = true;
            }

            dependency->waiters_.push_back(shared_from_this());
            waitOn_.push_back(workItem);
        }
        
        if (status)
        {
            Fail();
        }

        return AU_SHARED_FROM_THIS;
    }
    

    AuSPtr<IWorkItem> WorkItem::WaitFor(const AuList<AuSPtr<IWorkItem>> &workItems)
    {
        bool status {};

        {
            AU_LOCK_GUARD(lock);

            for (auto &workItem : workItems)
            {
                auto dependency = std::reinterpret_pointer_cast<WorkItem>(workItem);
                AU_LOCK_GUARD(dependency->lock);

                if (dependency->HasFailed())
                {
                    status = true;
                }

                dependency->waiters_.push_back(shared_from_this());
                waitOn_.push_back(workItem);
            }
        }

        if (status)
        {
            Fail();
        }

        return AU_SHARED_FROM_THIS;
    }
    
    AuSPtr<IWorkItem> WorkItem::Then(const AuSPtr<IWorkItem> &next)
    {
        auto that = AU_SHARED_FROM_THIS;
        next->WaitFor(that);
        next->Dispatch();
        return that;
    }
    
    AuSPtr<IWorkItem> WorkItem::SetSchedTimeNs(AuUInt64 ns)
    {
        dispatchTimeNs_  = Time::CurrentClockNS() + ns;
        return AU_SHARED_FROM_THIS;
    }

    AuSPtr<IWorkItem> WorkItem::SetSchedTime(AuUInt32 ms)
    {
        dispatchTimeNs_  = Time::CurrentClockNS() + (AuUInt64(ms) * AuUInt64(1000000));
        return AU_SHARED_FROM_THIS;
    }
    
    AuSPtr<IWorkItem> WorkItem::AddDelayTime(AuUInt32 ms)
    {
        delayTimeNs_ += AuUInt64(ms) * AuUInt64(1000000);
        return AU_SHARED_FROM_THIS;
    }

    AuSPtr<IWorkItem> WorkItem::AddDelayTimeNs(AuUInt64 ns)
    {
        delayTimeNs_ += ns;
        return AU_SHARED_FROM_THIS;
    }

    AuSPtr<IWorkItem> WorkItem::Dispatch()
    {
        DispatchEx(false);
        return AU_SHARED_FROM_THIS;
    }

    void WorkItem::DispatchEx(bool check)
    {
        AU_LOCK_GUARD(lock);

        if (check)
        {
            if (dispatchPending_)
            {
                return;
            }
        }

        if (HasFailed())
        {
            return;
        }

        for (auto itr = waitOn_.begin(); itr != waitOn_.end(); )
        {
            auto &waitable = *itr;

            if (!waitable->HasFinished())
            {
                return;
            }
            
            itr = waitOn_.erase(itr);
        }

        dispatchPending_ = true;

        if (Time::CurrentClockNS() < dispatchTimeNs_)
        {
            Schedule();
            return;
        }
        
        if (auto delay = std::exchange(delayTimeNs_, {}))
        {
            dispatchTimeNs_ = delay + Time::CurrentClockNS();
            Schedule();
            return;
        }

        SendOff();
    }

    void WorkItem::CancelAsync()
    {
        AU_LOCK_GUARD(lock);
        Fail();
    }

    void WorkItem::RunAsync()
    {
        AU_LOCK_GUARD(lock);

        IWorkItemHandler::ProcessInfo info(true);

        if (task_)
        {
            task_->DispatchFrame(info);
        }

        switch (info.type)
        {
        case IWorkItemHandler::EProcessNext::eFinished:
        {
            // do nothing
            break;
        }
        case IWorkItemHandler::EProcessNext::eInvalid:
        {
            SysPanic("Handle Invalid");
            break;
        }
        case IWorkItemHandler::EProcessNext::eSchedule:
        {
            if (info.reschedMs)
            {
                SetSchedTime(info.reschedMs);
            }
            if (info.reschedNs)
            {
                SetSchedTimeNs(info.reschedNs);
            }
            WaitFor(info.waitFor);

        }
        [[fallthrough]];
        case IWorkItemHandler::EProcessNext::eRerun:
        {
            DispatchEx(false);
            return;
        }
        case IWorkItemHandler::EProcessNext::eFailed:
        {
            Fail();
            return;
        }
        }

        finished = true;
        if (finishedEvent_)
        {
            finishedEvent_->Set();
        }

        for (auto &waiter : waiters_)
        {
            std::reinterpret_pointer_cast<WorkItem>(waiter)->DispatchEx(true);
        }
    }

    void WorkItem::Fail()
    {
        failed = true;

        if (auto task_ = std::exchange(this->task_, {}))
        {
            task_->Shutdown();
        }

        for (auto &waiter : waiters_)
        {
            std::reinterpret_pointer_cast<WorkItem>(waiter)->Fail();
        }

        waiters_.clear();
        waitOn_.clear();
     
        if (finishedEvent_)
        {
            finishedEvent_->Set();
        }
    }
    
    bool WorkItem::BlockUntilComplete()
    {
        if (!finishedEvent_) return false;
        return Async::GetAsyncApp()->WaitFor(this->worker_, finishedEvent_.get(), 0);
    }
    
    bool WorkItem::HasFinished()
    {
        return finished;
    }

    bool WorkItem::HasFailed()
    {
        return failed;
    }
    
    void WorkItem::Schedule()
    {
        Aurora::Async::Schedule(dispatchTimeNs_, worker_, this->shared_from_this());
    }

    void WorkItem::SendOff()
    {
        static_cast<AsyncApp *>(GetAsyncApp())->Run(worker_, this->shared_from_this());
    }

    AUKN_SYM AuSPtr<IWorkItem> NewWorkItem(const DispatchTarget_t &worker, const AuSPtr<IWorkItemHandler> &task, bool supportsBlocking)
    {
        return AuMakeShared<WorkItem>(worker, task, supportsBlocking);
    }
}