/***
    Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: IPCPromises.hpp
    Date: 2022-07-19
    Author: Reece
***/
#pragma once

struct AuNullS
{
    AuUInt8 null;
};

namespace Aurora::Async
{
    struct IPromiseCompleter
    {
        virtual void Complete() = 0;
        virtual void Fail() = 0;
    };

    struct IPromiseComplete
    {
        virtual void OnSuccess(void *in) = 0;
    };

    struct IPromiseFailure
    {
        virtual void OnFailure(void *in) = 0;
    };

    struct IPromisePtrs
    {
        virtual void *GetSuccessPtr() = 0;
        virtual void *GetErrorPtr() = 0;
        virtual AuSPtr<void> GetData() = 0;
    };

    template <class SuccessValue_t>
    struct PromiseSuccessTmpl : IPromiseComplete
    {
        using OnSuccess_f = AuFunction<void(const AuSPtr<SuccessValue_t> &)>;

        inline virtual void OnSuccess(void *in);

        inline void Init(IPromisePtrs *parent, const OnSuccess_f &onDelegate) noexcept
        {
            this->parent_ = parent;
            this->onSuccess_ = onDelegate;
        }

    private:
        IPromisePtrs *parent_;
        OnSuccess_f onSuccess_;
    };

    template <class SuccessValue_t, class ErrorValue_t = AuNullS>
    struct PromiseCallback : IPromiseFailure, IPromiseComplete
    {
        inline PromiseCallback()
        {}

        inline virtual void OnFailure(void *in) override
        {
            this->OnFailure(AuReinterpretCast<ErrorValue_t *>(in));
        }

        inline virtual void OnSuccess(void *in) override
        {
            this->OnSuccess(AuReinterpretCast<SuccessValue_t *>(in));
        }

        virtual void OnFailure(ErrorValue_t *in) = 0;
        virtual void OnSuccess(SuccessValue_t *in) = 0;
    };

    template <class SuccessValue_t, class ErrorValue_t = AuNullS>
    struct PromiseCallbackFunctional : PromiseCallback<SuccessValue_t, ErrorValue_t>, AuEnableSharedFromThis<PromiseCallbackFunctional<SuccessValue_t, ErrorValue_t>>
    {
        using OnSuccess_f = AuFunction<void(const AuSPtr<SuccessValue_t> &)>;
        using OnFailure_f = AuFunction<void(const AuSPtr<ErrorValue_t> &)>;

        inline PromiseCallbackFunctional(OnSuccess_f onSuccess,
                                         OnFailure_f onFailure) :
            onSuccess(onSuccess),
            onFailure(onFailure)
        {

        }

        inline PromiseCallbackFunctional(OnSuccess_f onSuccess) :
            onSuccess(onSuccess)
        {

        }

        inline PromiseCallbackFunctional()
        {

        }

        virtual void OnFailure(ErrorValue_t *in) override
        {
            if (this->onFailure)
            {
                if (!in)
                {
                    this->onFailure({});
                }
                else
                {
                    this->onFailure(AuSPtr<ErrorValue_t>(AuSharedFromThis(), in));
                }
            }
        }

        virtual void OnSuccess(SuccessValue_t *in) override
        {
            if (this->onSuccess)
            {
                if (!in)
                {
                    this->onSuccess({});
                }
                else
                {
                    this->onSuccess(AuSPtr<SuccessValue_t>(AuSharedFromThis(), in));
                }
            }
        }

        OnFailure_f onFailure;
        OnSuccess_f onSuccess;
    };

    template <class ErrorValue_t>
    struct PromiseFailTmpl : IPromiseFailure
    {
        using OnFailure_f = AuFunction<void(const AuSPtr<ErrorValue_t> &)>;

        inline virtual void OnFailure(void *in) override;

        inline void Init(IPromisePtrs *parent, const OnFailure_f &onDelegate) noexcept
        {
            this->parent_ = parent;
            this->onFailure_ = onDelegate;
        }
    private:
        IPromisePtrs *parent_;
        OnFailure_f onFailure_;
    };

    template <class SuccessValue_t, class ErrorValue_t>
    struct Promise;


    template <class SuccessValue_t, class ErrorValue_t>
    struct IPromiseAccessor : IPromiseCompleter
    {
        inline virtual AuSPtr<SuccessValue_t> WriteIntoSuccess() = 0;
        inline virtual AuSPtr<ErrorValue_t>   WriteIntoError() = 0;
    };

    struct IPromiseDelegate
    {
        virtual void OnPromiseDelegate(const AuSPtr<IPromiseCompleter> &promise) = 0;
    };

    template <class SuccessValue_t, class ErrorValue_t>
    struct PromiseCallTmpl : IPromiseDelegate
    {
        using OnDelegate_f = AuFunction<void(const AuSPtr<IPromiseAccessor<SuccessValue_t, ErrorValue_t>> &)>;

        inline virtual void OnPromiseDelegate(const AuSPtr<IPromiseCompleter> &promise) override;

        inline void Init(IPromisePtrs *parent, const OnDelegate_f &onDelegate) noexcept
        {
            this->parent_ = parent;
            this->onDelegate_ = onDelegate;
        }

    private:
        IPromisePtrs *parent_;
        OnDelegate_f onDelegate_;
    };


    struct IPromisePrivateCallbacks
    {
        virtual void OnCBTick() = 0;
        virtual void OnCBDelegate() = 0;
        virtual void OnCBFailure() = 0;
    };

    struct PromiseStartupAdapter : IWorkItemHandler
    {
        inline PromiseStartupAdapter(IPromisePrivateCallbacks *parent) noexcept
        {
            this->parent_ = parent;
        }

        inline virtual void DispatchFrame(IWorkItemHandler::ProcessInfo &info) override
        {
            this->parent_->OnCBDelegate();
        };

        inline virtual void OnFailure() override
        {
            SysPushErrorGeneric("Didnt fire initial delegate");
            this->parent_->OnCBFailure();
        };

    private:
        IPromisePrivateCallbacks *parent_;
    };

    struct PromiseTickAdapter : IWorkItemHandler
    {
        inline PromiseTickAdapter(IPromisePrivateCallbacks *parent) noexcept
        {
            this->parent_ = parent;
        }

        inline virtual void DispatchFrame(IWorkItemHandler::ProcessInfo &info) override
        {
            this->parent_->OnCBTick();
        };

        inline virtual void OnFailure() override
        {
            SysPushErrorGeneric("Didnt fire initial delegate");
            this->parent_->OnCBFailure();
        };

    private:
        IPromisePrivateCallbacks *parent_;
    };

    template <class SuccessValue_t, class ErrorValue_t>
    struct Promise final : IPromiseAccessor<SuccessValue_t, ErrorValue_t>, AuEnableSharedFromThis<Promise<SuccessValue_t, ErrorValue_t>>, private IPromisePtrs, private IPromisePrivateCallbacks
    {
        using This_t = Promise<SuccessValue_t, ErrorValue_t>;

        AU_SAFE_DESTROY(Promise);

        Promise(bool inlineResponse = false, bool allowSync = false);

        using FunctionalCall_t = PromiseCallTmpl<SuccessValue_t, ErrorValue_t>;
        using FunctionalResponse_t = PromiseSuccessTmpl<SuccessValue_t>;
        using FunctionalFail_t = PromiseFailTmpl<ErrorValue_t>;
        using FunctionalResponse_f = typename FunctionalResponse_t::OnSuccess_f;
        using FunctionalFail_f = typename FunctionalFail_t::OnFailure_f;
        using FunctionalDelegate_f = typename FunctionalCall_t::OnDelegate_f;

        inline AuSPtr<This_t> SetCallback(const AuSPtr<PromiseCallback<SuccessValue_t, ErrorValue_t>> &callbacks);

        inline AuSPtr<This_t> OnSuccessFunctional(const FunctionalResponse_f &in);
        inline AuSPtr<This_t> OnSuccessCallback(const AuSPtr<IPromiseComplete> &in);

        inline AuSPtr<This_t> OnFailureFunctional(const FunctionalFail_f &in);
        inline AuSPtr<This_t> OnFailureCallback(const AuSPtr<IPromiseFailure> &in);

        inline AuSPtr<SuccessValue_t> WriteIntoSuccess() override;
        inline AuSPtr<ErrorValue_t>   WriteIntoError() override;

        inline void Complete() override;
        inline void Fail() override;

        //inline AuSPtr<IWorkItem> GetBarrier() = 0;

        inline bool WaitBeforeWork(const AuSPtr<IWorkItem> &startingBarrier);

        inline bool BeginWork(WorkerPId_t worker = GetCurrentWorkerPId());
        inline bool BeginWorkEx(const AuSPtr<IPromiseDelegate> &promise, WorkerPId_t worker = GetCurrentWorkerPId());
        inline bool BeginWorkFunc(const FunctionalDelegate_f &promise, WorkerPId_t worker = GetCurrentWorkerPId());


        inline bool FinalizeWithWork(const AuSPtr<IWorkItem> &sendingFires);

    private:
        bool bHasBeganWork {};

        AuSPtr<IWorkItem> startingBarrier_;
        PromiseStartupAdapter startupAdapter;
        PromiseTickAdapter tickAdapter;

        inline virtual void OnCBTick() override;
        inline virtual void OnCBDelegate() override;
        inline virtual void OnCBFailure() override;

        inline void DestroyPrivate();

        inline void *GetSuccessPtr() override;
        inline void *GetErrorPtr() override;
        inline AuSPtr<void> GetData() override;

        void DoStartBlocking();
        void DoFailureBlocking();
        void DoSuccessBlocking();
        void DoEndBlocking();

        void DispatchNotifier();

        WorkerPId_t currentThread_;

        SuccessValue_t success;
        ErrorValue_t error;
        bool bHasSuccess_ {};
        bool bHasError_ {};

        bool bHasFiredSuccess_ {};
        bool bHasFiredError_ {};

        bool bInlineResponse_ {};

        FunctionalResponse_t responseFunctional_;
        AuSPtr<IPromiseComplete> responseCallback_;

        FunctionalFail_t failureFunctional_;
        AuSPtr<IPromiseFailure> failureCallback_;

        FunctionalCall_t delegateFunctional_;
        AuSPtr<IPromiseDelegate> delegateCallback_;

        bool bHasSentError_ {};
        bool bHasSentSuccess_ {};

        Aurora::Threading::Primitives::SpinLock lock_;

        AuSPtr<IWorkItem> notifier_;

        AuList<AuSPtr<IWorkItem>> startBarriers_;
    };

    template<class SuccessValue_t, class ErrorValue_t>
    inline Promise<SuccessValue_t, ErrorValue_t>::Promise(bool inlineResponse, bool allowSync) : startupAdapter(this), tickAdapter(this)
    {
        this->bInlineResponse_ = inlineResponse;
        auto pid = GetCurrentWorkerPId();
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DestroyPrivate()
    {
        if (this->notifier_)
        {
            this->notifier_->Cancel();
        }
        this->notifier_.reset();

        if (!this->bHasFiredSuccess_ &&
            !this->bHasFiredError_)
        {
            this->bHasFiredError_ = true;
            DoFailureBlocking();
        }
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DoStartBlocking()
    {}

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DoEndBlocking()
    {
        this->failureCallback_.reset();
        this->responseCallback_.reset();
        this->currentThread_ = {};
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::OnCBTick()
    {
        if (AuExchange(this->bHasFiredError_, false))
        {
              DoFailureBlocking();
        }
        else if (AuExchange(this->bHasFiredSuccess_, false))
        {
              DoSuccessBlocking();
        }
        else
        {
            SysPanic("");
        }

        this->bHasSentSuccess_ = true;
        this->bHasSentError_ = true;
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::OnCBDelegate()
    {
        //SysAssert(this->currentThread_ == GetCurrentWorkerPId());
        SysAssert(this->delegateCallback_);
        AuExchange(this->delegateCallback_, decltype(this->delegateCallback_) {})->OnPromiseDelegate(AuSharedFromThis());
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::OnCBFailure()
    {
        Destroy();
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DoFailureBlocking()
    {
        {
            AU_LOCK_GUARD(this->lock_);

            if (AuExchange(this->bHasSentError_, true))
            {
                return;
            }
        }

        this->DoStartBlocking();

        if (this->failureCallback_)
        {
            this->failureCallback_->OnFailure(this->bHasError_ ? &this->error : nullptr);
        }

        this->DoEndBlocking();
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DoSuccessBlocking()
    {
        {
            AU_LOCK_GUARD(this->lock_);

            if (AuExchange(this->bHasSentError_, true))
            {
                return;
            }

            if (AuExchange(this->bHasSentSuccess_, true))
            {
                return;
            }
        }

        this->DoStartBlocking();

        if (this->responseCallback_)
        {
            this->responseCallback_->OnSuccess(this->bHasSuccess_ ? &this->success : nullptr);
        }

        this->DoEndBlocking();
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void *Promise<SuccessValue_t, ErrorValue_t>::GetSuccessPtr()
    {
        return &this->success;
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void *Promise<SuccessValue_t, ErrorValue_t>::GetErrorPtr()
    {
        return &this->error;
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<void> Promise<SuccessValue_t, ErrorValue_t>::GetData()
    {
        return AuSPtr<void>(AuSharedFromThis());
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::Complete()
    {
        SysAssert(!this->bHasFiredSuccess_);
        SysAssert(!this->bHasFiredError_);
        this->bHasFiredSuccess_ = true;

        if (this->bInlineResponse_ &&
            this->currentThread_ == GetCurrentWorkerPId())
        {
            this->DoSuccessBlocking();
        }
        else
        {
            DispatchNotifier();
        }
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::Fail()
    {
        SysAssert(!this->bHasFiredSuccess_);
        this->bHasFiredError_ = true;

        if (this->bInlineResponse_ && 
            this->currentThread_ == GetCurrentWorkerPId())
        {
            this->DoFailureBlocking();
        }
        else
        {
            DispatchNotifier();
        }
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void Promise<SuccessValue_t, ErrorValue_t>::DispatchNotifier()
    {
        if (!this->notifier_)
        {
            this->notifier_ = this->currentThread_.pool->NewWorkItem(this->currentThread_, AuSPtr<IWorkItemHandler>(AuSharedFromThis(), &this->tickAdapter));
        }

        SysAssert(this->notifier_);
        this->notifier_->Dispatch();
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline bool Promise<SuccessValue_t, ErrorValue_t>::WaitBeforeWork(const AuSPtr<IWorkItem> &startingBarrier)
    {
        if (!this->startingBarrier_)
        {
            this->startingBarrier_ = GetCurrentWorkerPId().pool->NewFence();
        }

        if (!this->startingBarrier_)
        {
            return false;
        }

        this->startingBarrier_->WaitFor(startingBarrier);
        return true;
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline bool Promise<SuccessValue_t, ErrorValue_t>::BeginWork(WorkerPId_t worker)
    {
        this->currentThread_ = GetCurrentWorkerPId();

        SysAssert(worker.pool);

        if (worker == GetCurrentWorkerPId())
        {
            if (this->startingBarrier_)
            {
                this->startingBarrier_->Dispatch();
                return true;
            }

            this->OnCBDelegate();
            return true;
        }
        else
        {
            auto newItem = worker.pool->NewWorkItem(worker, AuSPtr<IWorkItemHandler>(AuSharedFromThis(), &this->startupAdapter));
            if (!newItem)
            {
                return {};
            }

            if (this->startingBarrier_)
            {
                this->startingBarrier_->Then(newItem);
            }
            else
            {
                newItem->Dispatch();
            }

            return true;
        }
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline bool Promise<SuccessValue_t, ErrorValue_t>::BeginWorkEx(const AuSPtr<IPromiseDelegate> &promise, WorkerPId_t worker)
    {
        this->delegateCallback_ = promise;
        return BeginWork(worker);
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline bool Promise<SuccessValue_t, ErrorValue_t>::BeginWorkFunc(const FunctionalDelegate_f &promise, WorkerPId_t worker)
    {
        this->delegateFunctional_.Init(this, promise);
        return BeginWorkEx(AuUnsafeRaiiToShared(&this->delegateFunctional_), worker);
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<Promise<SuccessValue_t, ErrorValue_t>> Promise<SuccessValue_t, ErrorValue_t>::SetCallback(const AuSPtr<PromiseCallback<SuccessValue_t, ErrorValue_t>> &callbacks)
    {
        this->OnSuccessCallback(callbacks);
        this->OnFailureCallback(callbacks);
        return AuSPtr<Promise>(AuSharedFromThis());
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<Promise<SuccessValue_t, ErrorValue_t>> Promise<SuccessValue_t, ErrorValue_t>::OnSuccessFunctional(const FunctionalResponse_f &in)
    {
        this->responseFunctional_.Init(this, in);
        return OnSuccessCallback(AuUnsafeRaiiToShared(&this->responseFunctional_));
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<Promise<SuccessValue_t, ErrorValue_t>> Promise<SuccessValue_t, ErrorValue_t>::OnSuccessCallback(const AuSPtr<IPromiseComplete> &in)
    {
        bool succeedFast {};
        {
            AU_LOCK_GUARD(this->lock_);

            if (this->bHasSentSuccess_)
            {
                succeedFast = true;
            }
            else
            {
                this->responseCallback_ = in;
            }
        }

        if (succeedFast)
        {
            in->OnSuccess(this->bHasSuccess_ ? &this->success : nullptr);
        }

        return AuSPtr<Promise>(AuSharedFromThis());
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<Promise<SuccessValue_t, ErrorValue_t>> Promise<SuccessValue_t, ErrorValue_t>::OnFailureFunctional(const FunctionalFail_f &in)
    {
        this->failureFunctional_.Init(this, in);
        return OnFailureCallback(AuUnsafeRaiiToShared(&this->failureFunctional_));
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<Promise<SuccessValue_t, ErrorValue_t>> Promise<SuccessValue_t, ErrorValue_t>::OnFailureCallback(const AuSPtr<IPromiseFailure> &in)
    {
        bool failFast {};
        {
            AU_LOCK_GUARD(this->lock_);

            if (this->bHasSentError_)
            {
                failFast = true;
            }
            else
            {
                this->failureCallback_ = in;
            }
        }

        if (failFast)
        {
            in->OnFailure(this->bHasError_ ? &this->error : nullptr);
        }

        return AuSPtr<Promise>(AuSharedFromThis());
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<SuccessValue_t> Promise<SuccessValue_t, ErrorValue_t>::WriteIntoSuccess()
    {
        this->bHasSuccess_ = true;
        return AuSPtr<SuccessValue_t>(AuSharedFromThis(), &this->success);
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline AuSPtr<ErrorValue_t> Promise<SuccessValue_t, ErrorValue_t>::WriteIntoError()
    {
        this->bHasError_ = true;
        return AuSPtr<ErrorValue_t>(AuSharedFromThis(), &this->error);
    }

    template<class SuccessValue_t, class ErrorValue_t>
    inline void PromiseCallTmpl<SuccessValue_t, ErrorValue_t>::OnPromiseDelegate(const AuSPtr<IPromiseCompleter> &promise)
    {
        auto ptr = static_cast<IPromiseAccessor<SuccessValue_t, ErrorValue_t> *>(promise.get());
        auto sptr = AuSPtr<IPromiseAccessor<SuccessValue_t, ErrorValue_t>>(promise, ptr);

        SysAssert(this->onDelegate_);

        this->onDelegate_(sptr);
    }

    template<class ErrorValue_t>
    inline void PromiseFailTmpl<ErrorValue_t>::OnFailure(void *in)
    {
        SysAssert(this->onFailure_);

        if (!in)
        {
            this->onFailure_({});
        }
        else
        {
            this->onFailure_(AuSPtr<ErrorValue_t>(this->parent_->GetData(), (ErrorValue_t *) in));
        }
    }

    template<class SuccessValue_t>
    inline void PromiseSuccessTmpl<SuccessValue_t>::OnSuccess(void *in)
    {
        SysAssert(this->onSuccess_);

        if (!in)
        {
            this->onSuccess_({});
        }
        else
        {
            this->onSuccess_(AuSPtr<SuccessValue_t>(this->parent_->GetData(), (SuccessValue_t *)in));
        }
    }
}

using AuNullPromise = Aurora::Async::Promise<AuNullS, AuNullS>;

template <class Out_t, class Error_t = AuNullS>
using AuPromise = Aurora::Async::Promise<Out_t, Error_t>;