/* ========================================================================
 * Copyright (c) 2005-2019 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * The complete license agreement can be found here:
 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

#include "StdAfx.h"
#include "COpcThreadPool.h"

//==============================================================================
// Local Declarations

static UINT g_uLastID = 0;

//==============================================================================
// Local Functions

static DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    ((COpcThreadPool*)lpParameter)->Run();
	return 0;
}

//==============================================================================
// COpcMessage

// Constructor
COpcMessage::COpcMessage(UINT uType, IOpcMessageCallback* ipCallback)
{
	m_uType = uType;
	m_uID   = (UINT)InterlockedIncrement((LONG*)&g_uLastID);

	m_ipCallback = NULL;

	if (ipCallback != NULL)
	{
		m_ipCallback = ipCallback;
		m_ipCallback->AddRef();
	}
}

// Copy Constructor
COpcMessage::COpcMessage(const COpcMessage& cMessage)
{
	m_uType      = cMessage.m_uType;
	m_uID        = cMessage.m_uID;
	m_ipCallback = cMessage.m_ipCallback;

	if (m_ipCallback != NULL)
	{
		m_ipCallback->AddRef();
	}
}

// Destructor
COpcMessage::~COpcMessage()
{
	if (m_ipCallback != NULL)
	{
		m_ipCallback->Release();
	}
}

//==============================================================================
// COpcThreadPool

// Constructor
COpcThreadPool::COpcThreadPool()
{
	m_hEvent          = NULL;
	m_uTotalThreads   = 0;
	m_uWaitingThreads = 0;
	m_uMinThreads     = 1;
	m_uMaxThreads     = 4;
}

// Destructor
COpcThreadPool::~COpcThreadPool()
{
	// check that stop was called prior to destruction.
	OPC_ASSERT(m_cQueue.GetCount() == 0);
}
    
// Start
bool COpcThreadPool::Start()
{
	COpcLock cLock(*this);

	if (m_hEvent != NULL)
	{
		Stop();
	}

	m_hEvent = CreateEvent(
		NULL,
		TRUE,
		FALSE,
		NULL
	);

	if (m_hEvent == NULL)
	{
		return false;
	}

	return true;
}

// Stop
void COpcThreadPool::Stop()
{
	COpcLock cLock(*this);

	// delete any remaining messages.
	while (m_cQueue.GetCount() > 0)
	{
		COpcMessage* pMessage = m_cQueue.RemoveHead();
		delete pMessage;
	}
	
	// close handle.
	CloseHandle(m_hEvent);
	m_hEvent = NULL;
}

// QueueMessage
bool COpcThreadPool::QueueMessage(COpcMessage* pMsg)
{
	COpcLock cLock(*this);

	// check for active queue.
	if (m_hEvent == NULL)
	{
		return false;
	}

	// add to queue.
	m_cQueue.AddTail(pMsg);

	// signal that the queue is not empty
	SetEvent(m_hEvent);

	// start a new thread if required.
	if (m_uWaitingThreads == 0 && m_uTotalThreads < m_uMaxThreads)
	{
		DWORD dwID = 0;

		HANDLE hThread = CreateThread(
			NULL,
			NULL,
			ThreadProc,
			(void*)this,
			NULL,
			&dwID);

		if (hThread == NULL)
		{
			return false;
		}

		CloseHandle(hThread);

		// increment thread count.
		m_uTotalThreads++;
	}

	return true;
}

// Run
void COpcThreadPool::Run()
{
	COpcLock cLock(*this);

	do
	{
		// increment waiting thread count.
		m_uWaitingThreads++;

		cLock.Unlock();

		// wait for message.
		DWORD dwResult = WaitForSingleObject(m_hEvent, INFINITE);

		cLock.Lock();		

		// decrement waiting thread count.
		m_uWaitingThreads--;

		// check for error or shutdown event.
		if (m_hEvent == NULL || dwResult != WAIT_OBJECT_0)
		{
			break;
		}

		// check if the queue has already been cleared.
		if (m_cQueue.GetCount() == 0)
		{
			ResetEvent(m_hEvent);

			if (m_uWaitingThreads >= m_uMinThreads)
			{
				break;
			}

			continue;
		}

		// get next message.
		COpcMessage* pMessage = m_cQueue.RemoveHead();

		// release queue lock - process message could hang.
		cLock.Unlock();

		// process message.
		pMessage->Process();
		delete pMessage;

		// re-acquire lock.
		cLock.Lock();
	}
	while (m_uWaitingThreads < m_uMinThreads);

	// decrement thread count.
	m_uTotalThreads--;
}

// SetSize
void COpcThreadPool::SetSize(UINT uMinThreads, UINT uMaxThreads)
{
	COpcLock cLock(*this);

	m_uMinThreads = uMinThreads;
	m_uMaxThreads = uMaxThreads;
}