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

    File: ThreadPool.hpp
    Date: 2021-10-30
    Author: Reece
***/
#pragma once

namespace Aurora::Async
{
    struct GroupState;
    struct ThreadState;
    struct IAsyncRunnable;
    //class WorkItem;


    struct IThreadPoolInternal
    {
        virtual bool WaitFor(WorkerId_t unlocker, const AuSPtr<Threading::IWaitable> &primitive, AuUInt32 ms) = 0; 
        virtual void Run(WorkerId_t target, AuSPtr<IAsyncRunnable> runnable) = 0;
        virtual IThreadPool *ToThreadPool() = 0;

        AuUInt32 uAtomicCounter {};
        AuUInt32 uAtomicIOProcessors {};
        AuUInt32 uAtomicIOProcessorsWorthlessSources {};
    };


    struct ThreadPool : IThreadPool, IThreadPoolInternal, AuEnableSharedFromThis<ThreadPool>
    {
        ThreadPool();
        
        // IThreadPoolInternal
        bool WaitFor(WorkerPId_t unlocker, const AuSPtr<Threading::IWaitable> &primitive, AuUInt32 ms);
        bool WaitFor(WorkerId_t unlocker, const AuSPtr<Threading::IWaitable> &primitive, AuUInt32 ms)  override;
        void Run(WorkerId_t target, AuSPtr<IAsyncRunnable> runnable)                                   override;
        void Run(WorkerId_t target, AuSPtr<IAsyncRunnable> runnable, bool bIncrement);
        IThreadPool *ToThreadPool()                                                                    override;
    
        // IThreadPool
        virtual bool Spawn(WorkerId_t workerId)                                                        override;
        
        virtual void SetRunningMode(bool eventRunning)                                                 override;
        
        virtual bool Create(WorkerId_t workerId)                                                       override;
        
        virtual bool InRunnerMode()                                                                    override;

        virtual bool Poll()                                                                            override;
        virtual bool RunOnce()                                                                         override;
        virtual bool Run()                                                                             override;
                                                                                                       
        virtual void Shutdown()                                                                        override;
        virtual bool Exiting()                                                                         override;

        virtual AuUInt32 PollAndCount(bool bStrict = true)                                             override;
        virtual AuUInt32 RunAllPending()                                                               override;
        
        virtual AuSPtr<IWorkItem> NewWorkItem(const WorkerId_t &worker, const AuSPtr<IWorkItemHandler> &task) override;
        virtual AuSPtr<IWorkItem> NewWorkFunction(const WorkerId_t &worker, AuVoidFunc callback) override;
        virtual AuSPtr<IWorkItem> NewFence()  override;

        virtual Threading::Threads::ThreadShared_t ResolveHandle(WorkerId_t)                           override;
                                                                                                       
        virtual AuBST<ThreadGroup_t, AuList<ThreadId_t>> GetThreads()                                  override;
                                                                                                       
        virtual WorkerId_t GetCurrentThread()                                                          override;

        virtual bool Sync(WorkerId_t workerId, AuUInt32 timeoutMs, bool requireSignal)                 override;
        virtual void Signal(WorkerId_t workerId)                                                       override;
        virtual AuSPtr<AuLoop::ILoopSource> WorkerToLoopSource(WorkerId_t id)                          override;
        virtual void SyncAllSafe()                                                                     override;

        virtual void AddFeature(WorkerId_t id, AuSPtr<Threading::Threads::IThreadFeature> feature, bool async) override;
        
        virtual void AssertInThreadGroup(ThreadGroup_t group)                                          override;
        virtual void AssertWorker(WorkerId_t id)                                                       override;

        virtual AuSPtr<AuLoop::ILoopQueue> ToKernelWorkQueue()                                         override;
        virtual AuSPtr<AuLoop::ILoopQueue> ToKernelWorkQueue(WorkerId_t workerId)                      override;
        virtual void UpdateWorkMode(WorkerId_t workerId, RunMode mode)                                 override;
        virtual ERunMode GetCurrentThreadRunMode()                                                     override;
        virtual ERunMode GetThreadRunMode(WorkerId_t workerId)                                         override;

        virtual AuSPtr<AuThreading::IWaitable> GetShutdownEvent() override;
        virtual void AddDependency(AuSPtr<IThreadPool> pPool) override;

        bool IsSelfDepleted();
        bool IsDepleted();

        //virtual bool ScheduleLoopSource(const AuSPtr<Loop::ILoopSource> &loopSource, WorkerId_t workerId, AuUInt32 timeout, const AuConsumer<AuSPtr<Loop::ILoopSource>, bool> &callback) override;

        // Internal API

        bool Spawn(WorkerId_t workerId, bool create);

        bool InternalRunOne(AuSPtr<ThreadState>, bool block, AuUInt32 &uCount);
        bool PollInternal(AuSPtr<ThreadState>, bool block, AuUInt32 &uCount);
        void DoThing(ThreadState *pState);

        size_t GetThreadWorkersCount(ThreadGroup_t group);
        
        virtual void CleanUpWorker(WorkerId_t wid) {};
        virtual void CleanWorkerPoolReservedZeroFree() {}; // calls shutdown under async apps

        // Secret old fiber api
        bool CtxYield();
        int  CtxPollPush();
        void CtxPollReturn(const AuSPtr<ThreadState> &state, int status, bool hitTask);

        // TLS handle
        struct WorkerWPId_t : WorkerId_t
        {
            WorkerWPId_t()
            {}
        
            WorkerWPId_t(const WorkerPId_t &ref) : WorkerId_t(ref.first, ref.second), pool(ref.pool)
            {}
      
            AuWPtr<IThreadPool> pool;
        };

        AuThreads::TLSVariable<WorkerWPId_t> tlsWorkerId;

        AuSPtr<ThreadState> GetThreadHandle(WorkerId_t id);
    private:
        // TODO: BarrierMultiple
        bool Barrier(WorkerId_t, AuUInt32 ms, bool requireSignal, bool drop);

    protected:
        void Entrypoint(WorkerId_t id);

    private:
        void EarlyExitTick();

        void ThisExiting();

        AuSPtr<GroupState>  GetGroup(ThreadGroup_t type);
        AuSPtr<ThreadState> GetThreadState();
        AuSPtr<ThreadState> GetThreadStateNoWarn();
        AuList<AuSPtr<ThreadState>> GetThreadHandles(WorkerId_t id);

        AuSPtr<GroupState> threadGroups_[255];
        AuUInt32 shuttingdown_ {};
        bool shutdown {};
        AuThreadPrimitives::RWRenterableLock rwlock_;
        AuThreadPrimitives::Event shutdownEvent_;
        bool runnersRunning_ {};
        AuList<AuWPtr<ThreadPool>> listWeakDeps_;
        AuList<AuWPtr<ThreadPool>> listWeakDepsParents_;

        friend struct KeepGroupAlive;
    };
}