/**
 * @file llevent.cpp
 * @brief LLEvent and LLEventListener base classes.
 *
 * $LicenseInfo:firstyear=2006&license=viewergpl$
 *
 * Copyright (c) 2006-2009, Linden Research, Inc.
 *
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 *
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 *
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 *
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
 * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
 * COMPLETENESS OR PERFORMANCE.
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "llevent.h"

using namespace LLOldEvents;

/************************************************
    Events
************************************************/

// virtual
bool LLEvent::accept(LLEventListener* listener)
{
	return true;
}

// virtual
const std::string& LLEvent::desc()
{
	return mDesc;
}

/************************************************
    Observables
************************************************/

LLObservable::LLObservable()
:	mDispatcher(new LLEventDispatcher())
{
}

// virtual
LLObservable::~LLObservable()
{
	if (mDispatcher.notNull())
	{
		mDispatcher->disengage(this);
		mDispatcher = NULL;
	}
}

// virtual
bool LLObservable::setDispatcher(LLPointer<LLEventDispatcher> dispatcher)
{
	if (mDispatcher.notNull())
	{
		mDispatcher->disengage(this);
		mDispatcher = NULL;
	}
	if (dispatcher.notNull() && dispatcher->engage(this))
	{
		mDispatcher = dispatcher;
		return true;
	}
	return false;
}

// Returns the current dispatcher pointer.
// virtual
LLEventDispatcher* LLObservable::getDispatcher()
{
	return mDispatcher;
}

// Notifies the dispatcher of an event being fired.
void LLObservable::fireEvent(LLPointer<LLEvent> event, LLSD filter)
{
	if (mDispatcher.notNull())
	{
		mDispatcher->fireEvent(event, filter);
	}
}

/************************************************
    Dispatchers
************************************************/

class LLEventDispatcher::Impl
{
public:
	virtual ~Impl()										{ }
	virtual bool engage(LLObservable* observable)		{ return true; }
	virtual void disengage(LLObservable* observable)	{}

	virtual void addListener(LLEventListener* listener, LLSD filter,
							 const LLSD& userdata) = 0;
	virtual void removeListener(LLEventListener* listener) = 0;
	virtual std::vector<LLListenerEntry> getListeners() const = 0;
	virtual bool fireEvent(LLPointer<LLEvent> event, LLSD filter) = 0;
};

bool LLEventDispatcher::engage(LLObservable* observable)
{
	return impl->engage(observable);
}

void LLEventDispatcher::disengage(LLObservable* observable)
{
	impl->disengage(observable);
}

void LLEventDispatcher::addListener(LLEventListener* listener, LLSD filter,
									const LLSD& userdata)
{
	impl->addListener(listener, filter, userdata);
}

void LLEventDispatcher::removeListener(LLEventListener* listener)
{
	impl->removeListener(listener);
}

std::vector<LLListenerEntry> LLEventDispatcher::getListeners() const
{
	return impl->getListeners();
}

bool LLEventDispatcher::fireEvent(LLPointer<LLEvent> event, LLSD filter)
{
	return impl->fireEvent(event, filter);
}

class LLSimpleDispatcher : public LLEventDispatcher::Impl
{
public:
	LLSimpleDispatcher(LLEventDispatcher* parent)
	:	mParent(parent)
	{
	}

	virtual ~LLSimpleDispatcher();
	virtual void addListener(LLEventListener* listener, LLSD filter,
							 const LLSD& userdata);
	virtual void removeListener(LLEventListener* listener);
	virtual std::vector<LLListenerEntry> getListeners() const;
	virtual bool fireEvent(LLPointer<LLEvent> event, LLSD filter);

protected:
	std::vector<LLListenerEntry>	mListeners;
	LLEventDispatcher*				mParent;
};

LLSimpleDispatcher::~LLSimpleDispatcher()
{
	while (mListeners.size() > 0)
	{
		removeListener(mListeners.begin()->listener);
	}
}

void LLSimpleDispatcher::addListener(LLEventListener* listener, LLSD filter,
									 const LLSD& userdata)
{
	if (listener)
	{
		removeListener(listener);
		LLListenerEntry new_entry;
		new_entry.listener = listener;
		new_entry.filter = filter;
		new_entry.userdata = userdata;
		mListeners.push_back(new_entry);
		listener->handleAttach(mParent);
	}
}

void LLSimpleDispatcher::removeListener(LLEventListener* listener)
{
	for (std::vector<LLListenerEntry>::iterator it = mListeners.begin(),
												end = mListeners.end();
		 it != end; ++it)
	{
		if (it->listener == listener)
		{
			mListeners.erase(it);
			break;
		}
	}
	listener->handleDetach(mParent);
}

std::vector<LLListenerEntry> LLSimpleDispatcher::getListeners() const
{
	std::vector<LLListenerEntry> ret;

	for (std::vector<LLListenerEntry>::const_iterator it = mListeners.begin(),
													  end = mListeners.end();
		 it != end; ++it)
	{
		ret.push_back(*it);
	}

	return ret;
}

// virtual
bool LLSimpleDispatcher::fireEvent(LLPointer<LLEvent> event, LLSD filter)
{
	std::string filter_string = filter.asString();

	for (std::vector<LLListenerEntry>::iterator it = mListeners.begin();
		 it != mListeners.end(); ++it)
	{
		LLListenerEntry& entry = *it;
		if (filter_string.empty() || entry.filter.asString() == filter_string)
		{
			(entry.listener)->handleEvent(event, it->userdata);
		}
	}

	return true;
}

LLEventDispatcher::LLEventDispatcher()
{
	impl = new LLSimpleDispatcher(this);
}

LLEventDispatcher::~LLEventDispatcher()
{
	if (impl)
	{
		delete impl;
		impl = NULL;
	}
}

/************************************************
    Listeners
************************************************/

LLSimpleListener::~LLSimpleListener()
{
	clearDispatchers();
}

void LLSimpleListener::clearDispatchers()
{
	// Remove myself from all listening dispatchers
	std::vector<LLEventDispatcher*>::iterator it;
	while (mDispatchers.size() > 0)
	{
		it = mDispatchers.begin();
		LLEventDispatcher* dispatcher = *it;
		dispatcher->removeListener(this);
		it = mDispatchers.begin();
		if (it != mDispatchers.end() && *it == dispatcher)
		{
			// Somehow, the dispatcher was not removed. Remove it forcibly
			mDispatchers.erase(it);
		}
	}
}

bool LLSimpleListener::handleAttach(LLEventDispatcher* dispatcher)
{
	// Add dispatcher if it does not already exist
	for (std::vector<LLEventDispatcher*>::iterator it = mDispatchers.begin(),
												   end = mDispatchers.end();
		 it != end; ++it)
	{
		if (*it == dispatcher)
		{
			return true;
		}
	}

	mDispatchers.push_back(dispatcher);

	return true;
}

bool LLSimpleListener::handleDetach(LLEventDispatcher* dispatcher)
{
	// Remove dispatcher from list
	for (std::vector<LLEventDispatcher*>::iterator it = mDispatchers.begin();
		 it != mDispatchers.end(); )
	{
		if (*it == dispatcher)
		{
			it = mDispatchers.erase(it);
		}
		else
		{
			++it;
		}
	}
	return true;
}