/*
 * This file is part of the Code::Blocks IDE and licensed under the GNU Lesser General Public License, version 3
 * http://www.gnu.org/licenses/lgpl-3.0.html
 *
 * $Revision: 12752 $
 * $Id: cbthreadpool.cpp 12752 2022-03-15 08:28:38Z wh11204 $
 * $HeadURL: https://svn.code.sf.net/p/codeblocks/code/trunk/src/sdk/cbthreadpool.cpp $
 */

#include "sdk_precomp.h"

#ifndef CB_PRECOMP
    #include "sdk_events.h"
    #include "manager.h"
    #include "logmanager.h"
#endif

#include "cbthreadpool.h"
#include <algorithm>
#include <functional>

cbThreadPool::~cbThreadPool()
{
    wxMutexLocker lock(m_Mutex);

    std::for_each(m_threads.begin(), m_threads.end(), std::mem_fn(&cbWorkerThread::Abort));
    Broadcast(); // make every waiting thread realise it's time to die

    std::for_each(m_tasksQueue.begin(), m_tasksQueue.end(), std::mem_fn(&cbThreadedTaskElement::Delete));
}

void cbThreadPool::SetConcurrentThreads(int concurrentThreads)
{
    // m_concurrentThreads is set here, it should always be a positive integer
    if (concurrentThreads <= 0)
    {
        concurrentThreads = wxThread::GetCPUCount(); // GetCPUCount will return -1 if it failed
        if (concurrentThreads == -1)
            m_concurrentThreads = 1;                   // as a fallback, we set the value to 1
    }

    if (concurrentThreads == m_concurrentThreads)
    {
        m_concurrentThreadsSchedule = 0;
        return;
    }

    wxMutexLocker lock(m_Mutex);
    _SetConcurrentThreads(concurrentThreads);
}

// this function is already wrappered by a mutex
void cbThreadPool::_SetConcurrentThreads(int concurrentThreads)
{
    if (!m_workingThreads)// if pool is not running (no thread is running)
    {
        std::for_each(m_threads.begin(), m_threads.end(), std::mem_fn(&cbWorkerThread::Abort));
        Broadcast();
        m_threads.clear();

        // set a new Semaphore for the new threads, note the max value is the concurrentThreads
        m_semaphore = CountedPtr<wxSemaphore>(new wxSemaphore(0, concurrentThreads));

        m_concurrentThreads = concurrentThreads;
        m_concurrentThreadsSchedule = 0;

        for (std::size_t i = 0; i < static_cast<std::size_t>(m_concurrentThreads); ++i)
        {
            m_threads.push_back(new cbWorkerThread(this, m_semaphore));
            m_threads.back()->Create(m_stackSize);
            m_threads.back()->Run(); // this will run cbWorkerThread::Entry()
        }

        // Manager::Get()->GetLogManager()->DebugLog(_T("Concurrent threads for pool set to %d"), m_concurrentThreads);
    }
    else
        m_concurrentThreadsSchedule = concurrentThreads;
}

void cbThreadPool::AddTask(cbThreadedTask *task, bool autodelete)
{
    if (!task)
        return;

    wxMutexLocker lock(m_Mutex);

    m_tasksQueue.push_back(cbThreadedTaskElement(task, autodelete));
    m_taskAdded = true;

    // we are in batch mode, so no need to awake the idle thread
    // m_workingThreads < m_concurrentThreads means there are some threads in idle mode (no task assigned)
    if (!m_batching && m_workingThreads < m_concurrentThreads)
        AwakeNeeded();
}

void cbThreadPool::AbortAllTasks()
{
    wxMutexLocker lock(m_Mutex);

    std::for_each(m_threads.begin(), m_threads.end(), std::mem_fn(&cbWorkerThread::AbortTask));
    std::for_each(m_tasksQueue.begin(), m_tasksQueue.end(), std::mem_fn(&cbThreadedTaskElement::Delete));
    m_tasksQueue.clear();
}

void cbThreadPool::BatchEnd()
{
    wxMutexLocker lock(m_Mutex);
    m_batching = false;

    AwakeNeeded();
}

cbThreadPool::cbThreadedTaskElement cbThreadPool::GetNextTask()
{
    wxMutexLocker lock(m_Mutex);

    if (m_tasksQueue.empty())
        return cbThreadedTaskElement();

    cbThreadedTaskElement element = m_tasksQueue.front();
    m_tasksQueue.pop_front();

    return element;
}

// a thread is leaving from idle mode, and run a task
void cbThreadPool::WorkingThread()
{
    wxMutexLocker lock(m_Mutex);
    ++m_workingThreads;
}

// this thread is finishing the task, and is going to be idle.
// if there is no task left, and the total threads is running is 0, then we have all task done
// otherwise, just put me to the idle mode by m_semaphore->Post()
bool cbThreadPool::WaitingThread()
{
    wxMutexLocker lock(m_Mutex);
    --m_workingThreads;

    if (m_workingThreads <= 0 && m_tasksQueue.empty())
    {
        if (m_taskAdded)
        {
            // notify the owner that all tasks are done
            CodeBlocksEvent evt = CodeBlocksEvent(cbEVT_THREADTASK_ALLDONE, m_ID);
            wxPostEvent(m_pOwner, evt);
            m_taskAdded = false;
        }

        // The last active thread is now waiting and there's a pending new number of threads to assign...
        if (m_concurrentThreadsSchedule)
        {
            _SetConcurrentThreads(m_concurrentThreadsSchedule);
            return false; // the thread must abort
        }
    }
    else
        m_semaphore->Post(); // return the resource back to pool

    return true;
}

void cbThreadPool::TaskDone(cb_unused cbWorkerThread* thread)
{
    // notify the owner that the task has ended
    CodeBlocksEvent evt = CodeBlocksEvent(cbEVT_THREADTASK_ENDED, m_ID);
    wxPostEvent(m_pOwner, evt);
}

/* *********************************************** */
/* ******** cbWorkerThread IMPLEMENTATION ******** */
/* *********************************************** */

cbThreadPool::cbWorkerThread::cbWorkerThread(cbThreadPool *pool, CountedPtr<wxSemaphore> &semaphore)
    : m_abort(false),
      m_pPool(pool),
      m_semaphore(semaphore),
      m_pTask(nullptr)
{
    // empty
}

wxThread::ExitCode cbThreadPool::cbWorkerThread::Entry()
{
    bool workingThread = false; // keeps the state of the thread so it knows better what to do
    // a working thread  = true means it is running a task, false means it is waiting a task

    while (!Aborted())
    {
        if (workingThread)
        {
            workingThread = false;

            // normally if pool own some resource, it will release one
            // If a call to WaitingThread returns false, we must abort
            if (!m_pPool->WaitingThread())
                break;

            // if there are still some tasks in the queue, WaitingThread() function will Post the
            // semaphore, and we don't delay much here for the Wait() function.
            // if there are no tasks to do, then WaitingThread() does not Post the semaphore, then
            // we are going to Idle mode now... Until some one release the resource

            m_semaphore->Wait(); // nothing to do... so just wait until it get the resource
        }

        if (Aborted())
            break;

        if (!workingThread)
        {
            m_pPool->WorkingThread(); // time to work! thread status from idle to running
            workingThread = true;
        }

        // fetch a task from the task queue
        cbThreadPool::cbThreadedTaskElement element = m_pPool->GetNextTask();

        {
            wxMutexLocker lock(m_taskMutex);
            m_pTask = element.task;
        }

        // are we done with all tasks?
        if (!m_pTask)
            continue;

        if (!Aborted())
        {
            m_pTask->Execute(); // run task's job here

            {
                wxMutexLocker lock(m_taskMutex);
                m_pTask = nullptr;
                element.Delete();
            }

            m_pPool->TaskDone(this); // send an notification event that one task is done.
        }
    }

    if (workingThread)
        m_pPool->WaitingThread();

    return nullptr;
}

void cbThreadPool::cbWorkerThread::Abort()
{
    m_abort = true;
    AbortTask();
}

bool cbThreadPool::cbWorkerThread::Aborted() const
{
    return m_abort;
}

void cbThreadPool::cbWorkerThread::AbortTask()
{
  wxMutexLocker lock(m_taskMutex);

  if (m_pTask)
      m_pTask->Abort();
}
