/*
 * Deskflow -- mouse and keyboard sharing utility
 * SPDX-FileCopyrightText: (C) 2012 - 2016 Symless Ltd.
 * SPDX-FileCopyrightText: (C) 2002 Chris Schoeneman
 * SPDX-License-Identifier: GPL-2.0-only WITH LicenseRef-OpenSSL-Exception
 */

#if defined(_MSC_VER) && !defined(_MT)
#error multithreading compile option is required
#endif

#include "arch/win32/ArchMultithreadWindows.h"
#include "arch/Arch.h"
#include "arch/ArchException.h"

#include <process.h>

//
// note -- implementation of condition variable taken from:
//   http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
// titled "Strategies for Implementing POSIX Condition Variables
// on Win32."  it also provides an implementation that doesn't
// suffer from the incorrectness problem described in our
// corresponding header but it is slower, still unfair, and
// can cause busy waiting.
//

//
// ArchThreadImpl
//

class ArchThreadImpl
{
public:
  ArchThreadImpl();
  ~ArchThreadImpl();

public:
  int m_refCount;
  HANDLE m_thread;
  DWORD m_id;
  IArchMultithread::ThreadFunc m_func;
  void *m_userData;
  HANDLE m_cancel;
  bool m_cancelling;
  HANDLE m_exit;
  void *m_result;
  void *m_networkData;
};

ArchThreadImpl::ArchThreadImpl()
    : m_refCount(1),
      m_thread(nullptr),
      m_id(0),
      m_func(nullptr),
      m_userData(nullptr),
      m_cancelling(false),
      m_result(nullptr),
      m_networkData(nullptr)
{
  m_exit = CreateEvent(nullptr, TRUE, FALSE, nullptr);
  m_cancel = CreateEvent(nullptr, TRUE, FALSE, nullptr);
}

ArchThreadImpl::~ArchThreadImpl()
{
  CloseHandle(m_exit);
  CloseHandle(m_cancel);
}

//
// ArchMultithreadWindows
//

ArchMultithreadWindows *ArchMultithreadWindows::s_instance = nullptr;

ArchMultithreadWindows::ArchMultithreadWindows()
{
  assert(s_instance == nullptr);
  s_instance = this;

  // no signal handlers
  for (size_t i = 0; i < static_cast<size_t>(ThreadSignal::MaxSignals); ++i) {
    m_signalFunc[i] = nullptr;
    m_signalUserData[i] = nullptr;
  }

  std::scoped_lock lock{m_threadMutex};

  // create thread for calling (main) thread and add it to our
  // list.  no need to lock the mutex since we're the only thread.
  m_mainThread = new ArchThreadImpl;
  m_mainThread->m_thread = nullptr;
  m_mainThread->m_id = GetCurrentThreadId();
  insert(m_mainThread);
}

ArchMultithreadWindows::~ArchMultithreadWindows()
{
  s_instance = nullptr;

  // clean up thread list
  for (ThreadList::iterator index = m_threadList.begin(); index != m_threadList.end(); ++index) {
    delete *index;
  }
}

void ArchMultithreadWindows::setNetworkDataForCurrentThread(void *data)
{
  std::scoped_lock lock{m_threadMutex};
  ArchThreadImpl *thread = findNoRef(GetCurrentThreadId());
  thread->m_networkData = data;
}

void *ArchMultithreadWindows::getNetworkDataForThread(ArchThread thread)
{
  std::scoped_lock lock{m_threadMutex};
  return thread->m_networkData;
}

HANDLE ArchMultithreadWindows::getCancelEventForCurrentThread()
{
  std::scoped_lock lock{m_threadMutex};
  ArchThreadImpl *thread = findNoRef(GetCurrentThreadId());
  return thread->m_cancel;
}

ArchMultithreadWindows *ArchMultithreadWindows::getInstance()
{
  return s_instance;
}

ArchCond ArchMultithreadWindows::newCondVar()
{
  ArchCondImpl *cond = new ArchCondImpl;
  cond->m_events[ArchCondImpl::kSignal] = CreateEvent(nullptr, FALSE, FALSE, nullptr);
  cond->m_events[ArchCondImpl::kBroadcast] = CreateEvent(nullptr, TRUE, FALSE, nullptr);
  cond->m_waitCountMutex = newMutex();
  cond->m_waitCount = 0;
  return cond;
}

void ArchMultithreadWindows::closeCondVar(ArchCond cond)
{
  CloseHandle(cond->m_events[ArchCondImpl::kSignal]);
  CloseHandle(cond->m_events[ArchCondImpl::kBroadcast]);
  closeMutex(cond->m_waitCountMutex);
  delete cond;
}

void ArchMultithreadWindows::signalCondVar(ArchCond cond)
{
  // is anybody waiting?
  lockMutex(cond->m_waitCountMutex);
  const bool hasWaiter = (cond->m_waitCount > 0);
  unlockMutex(cond->m_waitCountMutex);

  // wake one thread if anybody is waiting
  if (hasWaiter) {
    SetEvent(cond->m_events[ArchCondImpl::kSignal]);
  }
}

void ArchMultithreadWindows::broadcastCondVar(ArchCond cond)
{
  // is anybody waiting?
  lockMutex(cond->m_waitCountMutex);
  const bool hasWaiter = (cond->m_waitCount > 0);
  unlockMutex(cond->m_waitCountMutex);

  // wake all threads if anybody is waiting
  if (hasWaiter) {
    SetEvent(cond->m_events[ArchCondImpl::kBroadcast]);
  }
}

bool ArchMultithreadWindows::waitCondVar(ArchCond cond, ArchMutex mutex, double timeout)
{
  // prepare to wait
  const DWORD winTimeout = (timeout < 0.0) ? INFINITE : static_cast<DWORD>(1000.0 * timeout);

  // make a list of the condition variable events and the cancel event
  // for the current thread.
  HANDLE handles[4];
  handles[0] = cond->m_events[ArchCondImpl::kSignal];
  handles[1] = cond->m_events[ArchCondImpl::kBroadcast];
  handles[2] = getCancelEventForCurrentThread();

  // update waiter count
  lockMutex(cond->m_waitCountMutex);
  ++cond->m_waitCount;
  unlockMutex(cond->m_waitCountMutex);

  // release mutex.  this should be atomic with the wait so that it's
  // impossible for another thread to signal us between the unlock and
  // the wait, which would lead to a lost signal on broadcasts.
  // however, we're using a manual reset event for broadcasts which
  // stays set until we reset it, so we don't lose the broadcast.
  unlockMutex(mutex);

  // wait for a signal or broadcast
  DWORD result = WaitForMultipleObjects(3, handles, FALSE, winTimeout);

  // cancel takes priority
  if (result != WAIT_OBJECT_0 + 2 && WaitForSingleObject(handles[2], 0) == WAIT_OBJECT_0) {
    result = WAIT_OBJECT_0 + 2;
  }

  // update the waiter count and check if we're the last waiter
  lockMutex(cond->m_waitCountMutex);
  --cond->m_waitCount;
  const bool last = (result == WAIT_OBJECT_0 + 1 && cond->m_waitCount == 0);
  unlockMutex(cond->m_waitCountMutex);

  // reset the broadcast event if we're the last waiter
  if (last) {
    ResetEvent(cond->m_events[ArchCondImpl::kBroadcast]);
  }

  // reacquire the mutex
  lockMutex(mutex);

  // cancel thread if necessary
  if (result == WAIT_OBJECT_0 + 2) {
    ARCH->testCancelThread();
  }

  // return success or failure
  return (result == WAIT_OBJECT_0 + 0 || result == WAIT_OBJECT_0 + 1);
}

ArchMutex ArchMultithreadWindows::newMutex()
{
  ArchMutexImpl *mutex = new ArchMutexImpl;
  InitializeCriticalSection(&mutex->m_mutex);
  return mutex;
}

void ArchMultithreadWindows::closeMutex(ArchMutex mutex)
{
  DeleteCriticalSection(&mutex->m_mutex);
  delete mutex;
}

void ArchMultithreadWindows::lockMutex(ArchMutex mutex)
{
  EnterCriticalSection(&mutex->m_mutex);
}

void ArchMultithreadWindows::unlockMutex(ArchMutex mutex)
{
  LeaveCriticalSection(&mutex->m_mutex);
}

ArchThread ArchMultithreadWindows::newThread(ThreadFunc func, void *data)
{
  // note that the child thread will wait until we release this mutex
  std::scoped_lock lock{m_threadMutex};

  // create thread impl for new thread
  ArchThreadImpl *thread = new ArchThreadImpl;
  thread->m_func = func;
  thread->m_userData = data;

  // create thread
  unsigned int id = 0;
  thread->m_thread = reinterpret_cast<HANDLE>(_beginthreadex(nullptr, 0, threadFunc, (void *)thread, 0, &id));
  thread->m_id = static_cast<DWORD>(id);

  // check if thread was started
  if (thread->m_thread == 0) {
    // failed to start thread so clean up
    delete thread;
    thread = nullptr;
  } else {
    // add thread to list
    insert(thread);

    // increment ref count to account for the thread itself
    refThread(thread);
  }

  return thread;
}

ArchThread ArchMultithreadWindows::newCurrentThread()
{
  std::scoped_lock lock{m_threadMutex};
  ArchThreadImpl *thread = find(GetCurrentThreadId());
  assert(thread != nullptr);
  return thread;
}

void ArchMultithreadWindows::closeThread(ArchThread thread)
{
  assert(thread != nullptr);

  // decrement ref count and clean up thread if no more references
  if (--thread->m_refCount == 0) {
    // close the handle (main thread has a nullptr handle)
    if (thread->m_thread != nullptr) {
      CloseHandle(thread->m_thread);
    }

    // remove thread from list
    {
      std::scoped_lock lock{m_threadMutex};
      assert(findNoRefOrCreate(thread->m_id) == thread);
      erase(thread);
    }

    // done with thread
    delete thread;
  }
}

ArchThread ArchMultithreadWindows::copyThread(ArchThread thread)
{
  refThread(thread);
  return thread;
}

void ArchMultithreadWindows::cancelThread(ArchThread thread)
{
  assert(thread != nullptr);

  // set cancel flag
  SetEvent(thread->m_cancel);
}

void ArchMultithreadWindows::setPriorityOfThread(ArchThread thread, int n)
{
  struct PriorityInfo
  {
  public:
    DWORD m_class;
    int m_level;
  };
  static const PriorityInfo s_pClass[] = {
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_IDLE},
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_LOWEST},
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_BELOW_NORMAL},
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_NORMAL},
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_ABOVE_NORMAL},
      {IDLE_PRIORITY_CLASS, THREAD_PRIORITY_HIGHEST},
      {NORMAL_PRIORITY_CLASS, THREAD_PRIORITY_LOWEST},
      {NORMAL_PRIORITY_CLASS, THREAD_PRIORITY_BELOW_NORMAL},
      {NORMAL_PRIORITY_CLASS, THREAD_PRIORITY_NORMAL},
      {NORMAL_PRIORITY_CLASS, THREAD_PRIORITY_ABOVE_NORMAL},
      {NORMAL_PRIORITY_CLASS, THREAD_PRIORITY_HIGHEST},
      {HIGH_PRIORITY_CLASS, THREAD_PRIORITY_LOWEST},
      {HIGH_PRIORITY_CLASS, THREAD_PRIORITY_BELOW_NORMAL},
      {HIGH_PRIORITY_CLASS, THREAD_PRIORITY_NORMAL},
      {HIGH_PRIORITY_CLASS, THREAD_PRIORITY_ABOVE_NORMAL},
      {HIGH_PRIORITY_CLASS, THREAD_PRIORITY_HIGHEST},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_IDLE},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_LOWEST},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_BELOW_NORMAL},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_NORMAL},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_ABOVE_NORMAL},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_HIGHEST},
      {REALTIME_PRIORITY_CLASS, THREAD_PRIORITY_TIME_CRITICAL}
  };
#if defined(_DEBUG)
  // don't use really high priorities when debugging
  static const size_t s_pMax = 13;
#else
  static const size_t s_pMax = sizeof(s_pClass) / sizeof(s_pClass[0]) - 1;
#endif
  static const size_t s_pBase = 8; // index of normal priority

  assert(thread != nullptr);

  size_t index;
  if (n > 0 && s_pBase < (size_t)n) {
    // lowest priority
    index = 0;
  } else {
    index = (size_t)((int)s_pBase - n);
    if (index > s_pMax) {
      // highest priority
      index = s_pMax;
    }
  }
  SetPriorityClass(GetCurrentProcess(), s_pClass[index].m_class);
  SetThreadPriority(thread->m_thread, s_pClass[index].m_level);
}

void ArchMultithreadWindows::testCancelThread()
{
  // find current thread
  std::scoped_lock lock{m_threadMutex};
  ArchThreadImpl *thread = findNoRef(GetCurrentThreadId());

  // test cancel on thread
  testCancelThreadImpl(thread);
}

bool ArchMultithreadWindows::wait(ArchThread target, double timeout)
{
  assert(target != nullptr);

  ArchThreadImpl *self = nullptr;
  {
    std::scoped_lock lock{m_threadMutex};
    // find current thread
    self = findNoRef(GetCurrentThreadId());
    // ignore wait if trying to wait on ourself
    if (target == self) {
      return false;
    }
    // ref the target so it can't go away while we're watching it
    refThread(target);
  }

  // convert timeout
  DWORD t;
  if (timeout < 0.0) {
    t = INFINITE;
  } else {
    t = (DWORD)(1000.0 * timeout);
  }

  // wait for this thread to be cancelled or woken up or for the
  // target thread to terminate.
  HANDLE handles[2];
  handles[0] = target->m_exit;
  handles[1] = self->m_cancel;
  DWORD result = WaitForMultipleObjects(2, handles, FALSE, t);

  // cancel takes priority
  if (result != WAIT_OBJECT_0 + 1 && WaitForSingleObject(handles[1], 0) == WAIT_OBJECT_0) {
    result = WAIT_OBJECT_0 + 1;
  }

  // release target
  closeThread(target);

  // handle result
  switch (result) {
  case WAIT_OBJECT_0 + 0:
    // target thread terminated
    return true;

  case WAIT_OBJECT_0 + 1:
    // this thread was cancelled.  does not return.
    testCancelThreadImpl(self);

  default:
    // timeout or error
    return false;
  }
}

bool ArchMultithreadWindows::isSameThread(ArchThread thread1, ArchThread thread2)
{
  return (thread1 == thread2);
}

bool ArchMultithreadWindows::isExitedThread(ArchThread thread)
{
  // poll exit event
  return (WaitForSingleObject(thread->m_exit, 0) == WAIT_OBJECT_0);
}

void *ArchMultithreadWindows::getResultOfThread(ArchThread thread)
{
  std::scoped_lock lock{m_threadMutex};
  return thread->m_result;
}

IArchMultithread::ThreadID ArchMultithreadWindows::getIDOfThread(ArchThread thread)
{
  return static_cast<ThreadID>(thread->m_id);
}

void ArchMultithreadWindows::setSignalHandler(ThreadSignal signal, SignalFunc func, void *userData)
{
  std::scoped_lock lock{m_threadMutex};
  const auto index = static_cast<int>(signal);
  m_signalFunc[index] = func;
  m_signalUserData[index] = userData;
}

void ArchMultithreadWindows::raiseSignal(ThreadSignal signal)
{
  using enum IArchMultithread::ThreadSignal;
  std::scoped_lock lock{m_threadMutex};
  const auto index = static_cast<int>(signal);
  if (m_signalFunc[index] != nullptr) {
    m_signalFunc[index](signal, m_signalUserData[index]);
    ARCH->unblockPollSocket(m_mainThread);
  } else if (signal == Interrupt || signal == Terminate) {
    ARCH->cancelThread(m_mainThread);
  }
}

ArchThreadImpl *ArchMultithreadWindows::find(DWORD id)
{
  ArchThreadImpl *impl = findNoRef(id);
  if (impl != nullptr) {
    refThread(impl);
  }
  return impl;
}

ArchThreadImpl *ArchMultithreadWindows::findNoRef(DWORD id)
{
  ArchThreadImpl *impl = findNoRefOrCreate(id);
  if (impl == nullptr) {
    // create thread for calling thread which isn't in our list and
    // add it to the list.  this won't normally happen but it can if
    // the system calls us under a new thread, like it does when we
    // run as a service.
    impl = new ArchThreadImpl;
    impl->m_thread = nullptr;
    impl->m_id = GetCurrentThreadId();
    insert(impl);
  }
  return impl;
}

ArchThreadImpl *ArchMultithreadWindows::findNoRefOrCreate(DWORD id)
{
  // linear search
  for (ThreadList::const_iterator index = m_threadList.begin(); index != m_threadList.end(); ++index) {
    if ((*index)->m_id == id) {
      return *index;
    }
  }
  return nullptr;
}

void ArchMultithreadWindows::insert(ArchThreadImpl *thread)
{
  assert(thread != nullptr);

  // thread shouldn't already be on the list
  assert(findNoRefOrCreate(thread->m_id) == nullptr);

  // append to list
  m_threadList.push_back(thread);
}

void ArchMultithreadWindows::erase(ArchThreadImpl *thread)
{
  for (ThreadList::iterator index = m_threadList.begin(); index != m_threadList.end(); ++index) {
    if (*index == thread) {
      m_threadList.erase(index);
      break;
    }
  }
}

void ArchMultithreadWindows::refThread(ArchThreadImpl *thread)
{
  assert(thread != nullptr);
  assert(findNoRefOrCreate(thread->m_id) != nullptr);
  ++thread->m_refCount;
}

void ArchMultithreadWindows::testCancelThreadImpl(ArchThreadImpl *thread)
{
  assert(thread != nullptr);

  // poll cancel event.  return if not set.
  const DWORD result = WaitForSingleObject(thread->m_cancel, 0);
  if (result != WAIT_OBJECT_0) {
    return;
  }

  // update cancel state
  std::scoped_lock lock{m_threadMutex};
  bool cancel = !thread->m_cancelling;
  thread->m_cancelling = true;
  ResetEvent(thread->m_cancel);

  // unwind thread's stack if cancelling
  if (cancel) {
    throw ThreadCancelException();
  }
}

unsigned int __stdcall ArchMultithreadWindows::threadFunc(void *vrep)
{
  // get the thread
  ArchThreadImpl *thread = static_cast<ArchThreadImpl *>(vrep);

  // run thread
  s_instance->doThreadFunc(thread);

  // terminate the thread
  return 0;
}

void ArchMultithreadWindows::doThreadFunc(ArchThread thread)
{
  // wait for parent to initialize this object
  {
    std::scoped_lock lock{m_threadMutex};
  }

  void *result = nullptr;
  try {
    // go
    result = (*thread->m_func)(thread->m_userData);
  }

  catch (ThreadCancelException &) {
    // client called cancel()
  } catch (...) {
    // note -- don't catch (...) to avoid masking bugs
    {
      std::scoped_lock lock{m_threadMutex};
      SetEvent(thread->m_exit);
    }
    closeThread(thread);
    throw;
  }

  // thread has exited
  {
    std::scoped_lock lock{m_threadMutex};
    thread->m_result = result;
    SetEvent(thread->m_exit);
  }

  // done with thread
  closeThread(thread);
}