/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

#include <poll.h>

enum FdType {
    INTERNAL_QUEUE_FD,
    WINDOW_SYSTEM_FD,
    FD_COUNT,
};

//==============================================================================
class InternalMessageQueue
{
public:
    InternalMessageQueue()
        : fdCount (1),
          loopCount (0),
          bytesInSocket (0)
    {
        int ret = ::socketpair (AF_LOCAL, SOCK_STREAM, 0, fd);
        ignoreUnused (ret); jassert (ret == 0);

        auto internalQueueCb = [this] (int _fd)
        {
            if (const MessageManager::MessageBase::Ptr msg = this->popNextMessage (_fd))
            {
                JUCE_TRY
                {
                    msg->messageCallback();
                    return true;
                }
                JUCE_CATCH_EXCEPTION
            }
            return false;
        };

        pfds[INTERNAL_QUEUE_FD].fd = getReadHandle();
        pfds[INTERNAL_QUEUE_FD].events = POLLIN;
        readCallback[INTERNAL_QUEUE_FD] = new LinuxEventLoop::CallbackFunction<decltype(internalQueueCb)> (internalQueueCb);
    }

    ~InternalMessageQueue()
    {
        close (getReadHandle());
        close (getWriteHandle());

        clearSingletonInstance();
    }

    //==============================================================================
    void postMessage (MessageManager::MessageBase* const msg) noexcept
    {
        ScopedLock sl (lock);
        queue.add (msg);

        const int maxBytesInSocketQueue = 128;

        if (bytesInSocket < maxBytesInSocketQueue)
        {
            bytesInSocket++;

            ScopedUnlock ul (lock);
            const unsigned char x = 0xff;
            ssize_t bytesWritten = write (getWriteHandle(), &x, 1);
            ignoreUnused (bytesWritten);
        }
    }

    void setWindowSystemFd (int _fd, LinuxEventLoop::CallbackFunctionBase* _readCallback)
    {
        jassert (fdCount == 1);

        ScopedLock sl (lock);

        fdCount = 2;
        pfds[WINDOW_SYSTEM_FD].fd = _fd;
        pfds[WINDOW_SYSTEM_FD].events = POLLIN;
        readCallback[WINDOW_SYSTEM_FD] = _readCallback;
        readCallback[WINDOW_SYSTEM_FD]->active = true;
    }

    void removeWindowSystemFd()
    {
        jassert (fdCount == FD_COUNT);

        ScopedLock sl (lock);

        fdCount = 1;
        readCallback[WINDOW_SYSTEM_FD]->active = false;
    }

    bool dispatchNextEvent() noexcept
    {
        for (int counter = 0; counter < fdCount; counter++)
        {
            const int i = loopCount++;
            loopCount %= fdCount;
            if (readCallback[i] != nullptr && readCallback[i]->active)
            {
                if ((*readCallback[i]) (pfds[i].fd))
                    return true;
            }
        }

        return false;
    }

    bool sleepUntilEvent (const int timeoutMs)
    {
        const int pnum = poll (pfds, static_cast<nfds_t> (fdCount), timeoutMs);
        return (pnum > 0);
    }

    //==============================================================================
    juce_DeclareSingleton_SingleThreaded_Minimal (InternalMessageQueue)

private:
    CriticalSection lock;
    ReferenceCountedArray <MessageManager::MessageBase> queue;
    int fd[2];
    pollfd pfds[FD_COUNT];
    ScopedPointer<LinuxEventLoop::CallbackFunctionBase> readCallback[FD_COUNT];
    int fdCount;
    int loopCount;
    int bytesInSocket;

    int getWriteHandle() const noexcept     { return fd[0]; }
    int getReadHandle() const noexcept      { return fd[1]; }

    MessageManager::MessageBase::Ptr popNextMessage (int _fd) noexcept
    {
        const ScopedLock sl (lock);

        if (bytesInSocket > 0)
        {
            --bytesInSocket;

            const ScopedUnlock ul (lock);
            unsigned char x;
            ssize_t numBytes = read (_fd, &x, 1);
            ignoreUnused (numBytes);
        }

        return queue.removeAndReturn (0);
    }
};

juce_ImplementSingleton_SingleThreaded (InternalMessageQueue)


//==============================================================================
namespace LinuxErrorHandling
{
    static bool keyboardBreakOccurred = false;

    //==============================================================================
    void keyboardBreakSignalHandler (int sig)
    {
        if (sig == SIGINT)
            keyboardBreakOccurred = true;
    }

    void installKeyboardBreakHandler()
    {
        struct sigaction saction;
        sigset_t maskSet;
        sigemptyset (&maskSet);
        saction.sa_handler = keyboardBreakSignalHandler;
        saction.sa_mask = maskSet;
        saction.sa_flags = 0;
        sigaction (SIGINT, &saction, 0);
    }
}

//==============================================================================
void MessageManager::doPlatformSpecificInitialisation()
{
    if (JUCEApplicationBase::isStandaloneApp())
    {
        LinuxErrorHandling::installKeyboardBreakHandler();
    }

    // Create the internal message queue
    InternalMessageQueue* queue = InternalMessageQueue::getInstance();
    ignoreUnused (queue);
}

void MessageManager::doPlatformSpecificShutdown()
{
    InternalMessageQueue::deleteInstance();
}

bool MessageManager::postMessageToSystemQueue (MessageManager::MessageBase* const message)
{
    if (InternalMessageQueue* queue = InternalMessageQueue::getInstanceWithoutCreating())
    {
        queue->postMessage (message);
        return true;
    }

    return false;
}

void MessageManager::broadcastMessage (const String& /* value */)
{
    /* TODO */
}

// this function expects that it will NEVER be called simultaneously for two concurrent threads
bool MessageManager::dispatchNextMessageOnSystemQueue (bool returnIfNoPendingMessages)
{
    for (;;)
    {
        if (LinuxErrorHandling::keyboardBreakOccurred)
            JUCEApplicationBase::getInstance()->quit();

        if (InternalMessageQueue* queue = InternalMessageQueue::getInstanceWithoutCreating())
        {
            if (queue->dispatchNextEvent())
                break;

            else if (returnIfNoPendingMessages)
                return false;

            // wait for 2000ms for next events if necessary
            queue->sleepUntilEvent (2000);
        }
    }

    return true;
}

//==============================================================================


void LinuxEventLoop::setWindowSystemFdInternal (int fd, LinuxEventLoop::CallbackFunctionBase* readCallback) noexcept
{
    if (InternalMessageQueue* queue = InternalMessageQueue::getInstanceWithoutCreating())
        queue->setWindowSystemFd (fd, readCallback);
}

void LinuxEventLoop::removeWindowSystemFd() noexcept
{
    if (InternalMessageQueue* queue = InternalMessageQueue::getInstanceWithoutCreating())
        queue->removeWindowSystemFd();
}
