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

    File: Loop.Unix.cpp
    Date: 2021-10-1
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Loop.Unix.hpp"
#include "ILoopSourceEx.hpp"
#include <poll.h>

// TODO:
#if defined(AURORA_IS_LINUX_DERIVED)

namespace Aurora::IO::UNIX
{
    bool LinuxOverlappedYield(bool bUserspaceOnly);
}

#endif

namespace Aurora::IO::Loop
{
    extern AuRWRenterableLock gWaitForMultipleALLLock;

    void ResetLoopSourceFalseAlarm(const AuSPtr<Loop::ILoopSource> &pLoopSource);

    AuList<AuSPtr<ILoopSource>> WaitMultipleOrObjects(const AuList<AuSPtr<ILoopSource>> &objects, bool bAlert, bool bBreakAPCs, bool bZeroTick, AuUInt32 dwTimeoutReq, bool bAllowOthers, bool &bTooMany)
    {
    #if defined(AURORA_HAS_NO_POSIX_POLL)
        // do the WinNT falllback into loop queue.
        //
        // loop queues should have long term persistency in a user-space ABI (kqueue) or in the kernel (epoll)
        // they may take longer to setup, may seem wasteful to create and throw away, but it's probably the best we can do under BSD kernels.
        // why? kevents exist for posix aio objects. they dont use fds.
        //
        // BSDs with posix AIO based async file transactions, >2.2 linux kernels, macos with corefoundation interop with kqueues, and other posix kernels with alternative aio will probably need
        //  need to use the win32 64 <= handles path.
        bTooMany = true;
        return false;
    #else
        AuList<AuSPtr<ILoopSource>>   triggered;

        // fallback
        AuList<AuSPtr<ILoopSourceEx>> loopSourceExs1;
        AuList<AuSPtr<ILoopSourceEx>> loopSourceExs21;
        AuList<pollfd>                handleArray1;
        AuList<AuPair<AuUInt, bool>>  handleIndicies1;
        
        // 4k~ of stack
        AuSPtr<ILoopSourceEx>         loopSourceExs12[128];
        AuSPtr<ILoopSourceEx>         loopSourceExs22[128];
        pollfd                        handleArray2[128];
        AuPair<AuUInt, bool>          handleIndicies2[128];
        
        // phead
        AuSPtr<ILoopSourceEx> *       pLoopSourceExs1;
        AuSPtr<ILoopSourceEx> *       pLoopSourceExs2;
        pollfd *                      pHandleArray;
        AuPair<AuUInt, bool> *        pHandleIndicies;
        AuUInt32 uHandleOffset, uFDOffset, uHandleOffset2;

        // length / size
        uHandleOffset   = 0;
        uHandleOffset2  = 0;
        uFDOffset       = 0;

        // default heads
        pLoopSourceExs1 = loopSourceExs12;
        pLoopSourceExs2 = loopSourceExs22;
        pHandleArray    = handleArray2;
        pHandleIndicies = handleIndicies2;

    #define HANDLE_PUSH_CHILD_Z(value, aaa, bbb, ccc, ggg, FF)                                                               \
        {                                                                                                                    \
            if (FF > AuArraySize(aaa))                                                                                       \
            {                                                                                                                \
                ccc.push_back(value);                                                                                        \
                bbb = ccc.data();                                                                                            \
            }                                                                                                                \
            else if (FF == AuArraySize(aaa))                                                                                 \
            {                                                                                                                \
                ccc.insert(ccc.begin(), &ggg[0], &ggg[AuArraySize(aaa)]);                                                    \
                ccc.push_back(value);                                                                                        \
                bbb = ccc.data();                                                                                            \
            }                                                                                                                \
            else                                                                                                             \
            {                                                                                                                \
                bbb[FF] = value;                                                                                             \
            }                                                                                                                \
        }
                                                                                                        
    #define HANDLE_PUSH_MAIN2(value)                                                                                         \
            HANDLE_PUSH_CHILD_Z(value, loopSourceExs22, pLoopSourceExs2, loopSourceExs21, pLoopSourceExs2, uCurHandle)

    #define HANDLE_PUSH_MAIN(value, handle)                                                                                  \
            HANDLE_PUSH_CHILD_Z(value, loopSourceExs22,  pLoopSourceExs1, loopSourceExs1,  pLoopSourceExs1, handle)

    #define HANDLE_PUSH_CHILD(value)                                                                                         \
        {                                                                                                                    \
            auto uCurFD = uFDOffset++;                                                                                       \
            HANDLE_PUSH_CHILD_Z(value, loopSourceExs22, pHandleArray, handleArray1, handleArray2, uCurFD)                    \
        }

    #define HANDLE_PUSH_CHILD2(value)                                                                                        \
        {                                                                                                                    \
            HANDLE_PUSH_CHILD_Z(value, loopSourceExs22, pHandleIndicies, handleIndicies1,  handleIndicies2, (uFDOffset - 1)) \
        }

        try
        {
            if (AuArraySize(loopSourceExs22) < objects.size())
            {
                loopSourceExs1.reserve(objects.size());
                loopSourceExs21.reserve(objects.size());
                handleArray1.reserve(objects.size());
                handleIndicies1.reserve(triggered.size());
            }

            triggered.reserve(triggered.size());

            for (const auto &source : objects)
            {
                if (!source)
                {
                    continue;
                }

                if (auto extended = AuDynamicCast<ILoopSourceEx>(source))
                {
                    auto uCurHandle = uHandleOffset++;

                    HANDLE_PUSH_MAIN2(extended)

                    if (extended->Singular())
                    {
                        auto handle      = extended->GetHandle();
                        auto handleWrite = extended->GetWriteHandle();

                        auto i = uHandleOffset2++;
                        HANDLE_PUSH_MAIN(extended, i);

                        if (handle != -1)
                        {
                            pollfd poll;
                            poll.fd      = handle;
                            poll.events  = POLLIN;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                        }

                        if (handleWrite != -1)
                        {
                            pollfd poll;
                            poll.fd      = handleWrite;
                            poll.events  = POLLOUT;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                        }
                    }
                    else
                    {
                        auto handles      = extended->GetHandles();
                        auto handlesWrite = extended->GetWriteHandles();

                        auto i = uHandleOffset2++;
                        HANDLE_PUSH_MAIN(extended, i);

                        for (const auto &handle : handles)
                        {
                            pollfd poll;
                            if (handle == -1)
                            {
                                continue;
                            }

                            poll.fd      = handle;
                            poll.events  = POLLIN;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                        }

                        for (const auto &handle : handlesWrite)
                        {
                            pollfd poll;
                            if (handle == -1)
                            {
                                continue;
                            }
                            
                            poll.fd      = handle;
                            poll.events  = POLLOUT;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                        }
                    }
                }
            }
        }
        catch (...)
        {
            return {};
        }

        // must be 1:1 - do not mess with
        for (AU_ITERATE_N(i, uHandleOffset))
        {
            pLoopSourceExs2[i]->OnPresleep();
        }

        AuUInt32 uTimeout {};
        if (bZeroTick)
        {
            uTimeout = 0;
        }
        else if (!dwTimeoutReq)
        {
            uTimeout = -1;
        }
        else
        {
            uTimeout = dwTimeoutReq;
        }

        int ret;
        do
        {
            // TODO: bAlert awareness (cannot enter alert sleep yet. no such impl on linux)
            //                        (we need an io_submit posix poll shim + apc event + queue that we dont have yet)
            ret = poll(pHandleArray, uFDOffset, uTimeout);
            uTimeout = 0;

            if (ret > 0)
            {
                AU_LOCK_GLOBAL_GUARD(gWaitForMultipleALLLock->AsReadable());

                for (AU_ITERATE_N(i, uFDOffset))
                {
                    if (!pHandleArray[i].revents)
                    {
                        continue;
                    }

                    auto uIndex      = AuGet<0>(pHandleIndicies[i]);
                    auto bRead       = AuGet<1>(pHandleIndicies[i]);
                    auto pLoopSource = AuExchange(pLoopSourceExs1[uIndex], nullptr);
                    if (!pLoopSource)
                    {
                        // TODO: notify other? special types go here?
                        continue;
                    }

                    if (!pLoopSource->OnTrigger(pHandleArray[i].fd))
                    {
                        pLoopSourceExs1[uIndex] = pLoopSource;
                        continue;
                    }

                    triggered.push_back(pLoopSource);

                    if (!bAllowOthers)
                    {
                        break;
                    }
                }
            }
        }
        while (ret == -1 &&
               errno == EINTR);

        // must be 1:1 - do not mess with
        for (AU_ITERATE_N(i, uHandleOffset))
        {
            pLoopSourceExs2[i]->OnFinishSleep();
        }

        if (bAlert)
        {
        #if defined(AURORA_IS_LINUX_DERIVED)
            // Do not syscall after read or select again under Linux
            UNIX::LinuxOverlappedYield(true);
        #else
            IOYield();
        #endif
        }

        return AuMove(triggered);
    #endif
    }

    bool WaitMultipleAndObjects_(const AuList<AuSPtr<ILoopSource>> &objects, bool bAlert, bool bBreakAPCs, bool bZeroTick, AuUInt64 qwTimeoutAbs, bool &bTooMany, bool &bTimeout)
    {
    #if defined(AURORA_HAS_NO_POSIX_POLL)
        // do the WinNT falllback into loop queue.
        //
        // loop queues should have long term persistency in a user-space ABI (kqueue) or in the kernel (epoll)
        // they may take longer to setup, may seem wasteful to create and throw away, but it's probably the best we can do under BSD kernels.
        // why? kevents exist for posix aio objects. they dont use fds.
        //
        // BSDs with posix AIO based async file transactions, >2.2 linux kernels, macos with corefoundation interop with kqueues, and other posix kernels with alternative aio will probably need
        //  need to use the win32 64 <= handles path.
        bTooMany = true;
        return false;
    #else
        AuList<AuSPtr<ILoopSource>>   triggered;

        // fallback
        AuList<AuSPtr<ILoopSourceEx>> loopSourceExs1;
        AuList<AuSPtr<ILoopSourceEx>> loopSourceExs21;
        AuList<pollfd>                handleArray1;
        AuList<pollfd>                handleArrayPersistent1;
        AuList<AuPair<AuUInt, bool>>  handleIndicies1;
        
        // 4k~ of stack
        AuSPtr<ILoopSourceEx>         loopSourceExs12[128];
        AuSPtr<ILoopSourceEx>         loopSourceExs22[128];
        pollfd                        handleArray2[128];
        pollfd                        handleArrayPersistent2[128];
        AuPair<AuUInt, bool>          handleIndicies2[128];
        
        // phead
        AuSPtr<ILoopSourceEx> *       pLoopSourceExs1;
        AuSPtr<ILoopSourceEx> *       pLoopSourceExs2;
        pollfd *                      pHandleArray;
        pollfd *                      pHandleArrayPersistent;
        AuPair<AuUInt, bool> *        pHandleIndicies;
        AuUInt32 uHandleOffset, uFDOffset, uHandleOffset2;

        // length / size
        uHandleOffset   = 0;
        uHandleOffset2  = 0;
        uFDOffset       = 0;

        // default heads
        pLoopSourceExs1 = loopSourceExs12;
        pLoopSourceExs2 = loopSourceExs22;
        pHandleArray    = handleArray2;
        pHandleIndicies = handleIndicies2;
        pHandleArrayPersistent = handleArrayPersistent2;

        AuUInt32 uTotal { 0 };


    #define HANDLE_PUSH_CHILD3(value)                                                                                                             \
        {                                                                                                                                         \
            HANDLE_PUSH_CHILD_Z(value, loopSourceExs22, pHandleArrayPersistent, handleArrayPersistent1,  handleArrayPersistent2, (uFDOffset - 1)) \
        }

        try
        {
            if (AuArraySize(loopSourceExs22) < objects.size())
            {
                loopSourceExs1.reserve(objects.size());
                loopSourceExs21.reserve(objects.size());
                handleArray1.reserve(objects.size());
                handleIndicies1.reserve(triggered.size());
            }

            triggered.reserve(triggered.size());

            for (const auto &source : objects)
            {
                if (!source)
                {
                    continue;
                }

                if (auto extended = AuDynamicCast<ILoopSourceEx>(source))
                {
                    auto uCurHandle = uHandleOffset++;

                    HANDLE_PUSH_MAIN2(extended)

                    if (extended->Singular())
                    {
                        auto handle      = extended->GetHandle();
                        auto handleWrite = extended->GetWriteHandle();

                        auto i = uHandleOffset2++;
                        HANDLE_PUSH_MAIN(extended, i);

                        if (handle != -1)
                        {
                            pollfd poll;
                            poll.fd      = handle;
                            poll.events  = POLLIN;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                            HANDLE_PUSH_CHILD3(poll)
                        }

                        if (handleWrite != -1)
                        {
                            pollfd poll;
                            poll.fd      = handleWrite;
                            poll.events  = POLLOUT;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                            HANDLE_PUSH_CHILD3(poll)
                        }
                    }
                    else
                    {
                        auto handles      = extended->GetHandles();
                        auto handlesWrite = extended->GetWriteHandles();

                        auto i = uHandleOffset2++;
                        HANDLE_PUSH_MAIN(extended, i);

                        for (const auto &handle : handles)
                        {
                            pollfd poll;
                            if (handle == -1)
                            {
                                continue;
                            }

                            poll.fd      = handle;
                            poll.events  = POLLIN;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                            HANDLE_PUSH_CHILD3(poll)
                        }

                        for (const auto &handle : handlesWrite)
                        {
                            pollfd poll;
                            if (handle == -1)
                            {
                                continue;
                            }
                            
                            poll.fd      = handle;
                            poll.events  = POLLOUT;
                            poll.revents = 0;

                            HANDLE_PUSH_CHILD(poll);
                            HANDLE_PUSH_CHILD2(AuMakePair(i, false));
                            HANDLE_PUSH_CHILD3(poll)
                        }
                    }
                }
            }
        }
        catch (...)
        {
            return {};
        }

        // must be 1:1 - do not mess with
        for (AU_ITERATE_N(i, uHandleOffset))
        {
            pLoopSourceExs2[i]->OnPresleep();
        }

        int ret;
        do
        {
            AuUInt32 uTimeout;

            if (bZeroTick)
            {
                uTimeout = 0;
            }
            else if (qwTimeoutAbs)
            {
                auto uNow = AuTime::SteadyClockNS();
                if (uNow >= qwTimeoutAbs)
                {
                    uTimeout = 0;
                }
                else
                {
                    uTimeout = AuNSToMS<AuUInt32>(qwTimeoutAbs - uNow);
                }
            }
            else
            {
                uTimeout = -1;
            }

            ret = poll(pHandleArray, uFDOffset, uTimeout);
            uTimeout = 0;

            if (ret > 0)
            {
                for (AU_ITERATE_N(i, uFDOffset))
                {
                    if (!pHandleArray[i].revents)
                    {
                        continue;
                    }

                    uTotal += 1;
                    pHandleArrayPersistent[i] = pHandleArray[i];
                    pHandleArray[i].fd = -1;
                }
            }

            if (qwTimeoutAbs)
            {
                auto uNow = AuTime::SteadyClockNS();
                if (uNow >= qwTimeoutAbs)
                {
                    bTimeout = true;
                    break;
                }
            }
        }
        while ((ret == -1 &&
                errno == EINTR) || (uTotal != uFDOffset));

        bool bRet = uTotal == uFDOffset;

        if (bRet)
        {
            AU_LOCK_GLOBAL_GUARD(gWaitForMultipleALLLock->AsWritable());

            for (AU_ITERATE_N(i, uFDOffset))
            {
                auto uIndex      = AuGet<0>(pHandleIndicies[i]);
                auto bRead       = AuGet<1>(pHandleIndicies[i]);
                auto pLoopSource = AuExchange(pLoopSourceExs1[uIndex], nullptr);
                if (!pLoopSource)
                {
                    continue;
                }

                if (!pLoopSource->OnTrigger(pHandleArrayPersistent[i].fd))
                {
                    for (AU_ITERATE_N(z, i))
                    {
                        ResetLoopSourceFalseAlarm(pLoopSourceExs1[z]);
                    }

                    bRet = false;
                    break;
                }
            }
        }

        // must be 1:1 - do not mess with
        for (AU_ITERATE_N(i, uHandleOffset))
        {
            pLoopSourceExs2[i]->OnFinishSleep();
        }

        return bRet;
    #endif
    }

    bool WaitMultipleAndObjects(const AuList<AuSPtr<ILoopSource>> &objects, bool bAlert, bool bBreakAPCs, bool bZeroTick, AuUInt64 qwTimeoutAbs, bool &bTooMany, bool &bTimeout)
    {
        bool bRet {};
        do
        {
            bool bAPCDispatch {};

            bRet = WaitMultipleAndObjects_(objects, bAlert, bBreakAPCs, bZeroTick, qwTimeoutAbs, bTooMany, bTimeout);

            if (bAlert)
            {
            #if defined(AURORA_IS_LINUX_DERIVED)
                // Do not syscall after read or select again under Linux
                bAPCDispatch = UNIX::LinuxOverlappedYield(true);
            #else
                bAPCDispatch = IOYield();
            #endif
            }

            if (bBreakAPCs && bAPCDispatch)
            {
                break;
            }
        }
        while (!bRet && !bTimeout);
        
        return bRet;
    }
}