/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2009 Daniel De Graaf <danieldg@inspircd.org>
 *   Copyright (C) 2008 Craig Edwards <craigedwards@brainbox.cc>
 *
 * This file is part of InspIRCd.  InspIRCd is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#pragma once

#include "config.h"
#include "base.h"

class Thread;

/** The ThreadEngine class has the responsibility of initialising
 * Thread derived classes. It does this by creating operating system
 * level threads which are then associated with the class transparently.
 * This allows Thread classes to be derived without needing to know how
 * the OS implements threads. You should ensure that any sections of code
 * that use threads are threadsafe and do not interact with any other
 * parts of the code which are NOT known threadsafe! If you really MUST
 * access non-threadsafe code from a Thread, use the Mutex class to wrap
 * access to the code carefully.
 */
class CoreExport ThreadEngine
{
 public:
	/** Per-thread state, present in each Thread object, managed by the ThreadEngine
	 */
	struct ThreadState
	{
		HANDLE handle;
	};

	static DWORD WINAPI Entry(void* parameter);

	/** Create a new thread. This takes an already allocated
	  * Thread* pointer and initializes it to use this threading
	  * engine. On failure, this function may throw a CoreException.
	  * @param thread_to_init Pointer to a newly allocated Thread
	  * derived object.
	  */
	void Start(Thread* thread_to_init);

	/** Stop a thread gracefully.
	 * First, this function asks the thread to terminate by calling Thread::SetExitFlag().
	 * Next, it waits until the thread terminates (on the operating system level). Finally,
	 * all OS-level resources associated with the thread are released. The Thread instance
	 * passed to the function is NOT freed.
	 * When this function returns, the thread is stopped and you can destroy it or restart it
	 * at a later point.
	 * Stopping a thread that is not running is a bug.
	 * @param thread The thread to stop.
	 */
	void Stop(Thread* thread);
};

/** The Mutex class represents a mutex, which can be used to keep threads
 * properly synchronised. Use mutexes sparingly, as they are a good source
 * of thread deadlocks etc, and should be avoided except where absolutely
 * neccessary. Note that the internal behaviour of the mutex varies from OS
 * to OS depending on the thread engine, for example in windows a Mutex
 * in InspIRCd uses critical sections, as they are faster and simpler to
 * manage.
 */
class CoreExport Mutex
{
 private:
	CRITICAL_SECTION wutex;
 public:
	Mutex()
	{
		InitializeCriticalSection(&wutex);
	}
	void Lock()
	{
		EnterCriticalSection(&wutex);
	}
	void Unlock()
	{
		LeaveCriticalSection(&wutex);
	}
	~Mutex()
	{
		DeleteCriticalSection(&wutex);
	}
};

class ThreadQueueData : public Mutex
{
	HANDLE event;
 public:
	ThreadQueueData()
	{
		event = CreateEvent(NULL, false, false, NULL);
		if (event == NULL)
			throw CoreException("CreateEvent() failed in ThreadQueueData::ThreadQueueData()!");
	}

	~ThreadQueueData()
	{
		CloseHandle(event);
	}

	void Wakeup()
	{
		PulseEvent(event);
	}

	void Wait()
	{
		Unlock();
		WaitForSingleObject(event, INFINITE);
		Lock();
	}
};

class ThreadSignalData
{
 public:
	int connFD;
	ThreadSignalData()
	{
		connFD = -1;
	}
};
