/** 
 * @file lllivefile.h
 * @brief Automatically reloads a file whenever it changes or is removed.
 *
 * $LicenseInfo:firstyear=2006&license=viewergpl$
 * 
 * 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.
 * $/LicenseInfo$
 */

#ifndef LL_LLLIVEFILE_H
#define LL_LLLIVEFILE_H

#include "llpreprocessor.h"

#include "stdtypes.h"

constexpr F32 DEFAULT_CONFIG_FILE_REFRESH = 5.f;

class LLLiveFile
{
public:
	LLLiveFile(const std::string& filename, F32 refresh_period = 5.f);
	virtual ~LLLiveFile();

	// Checks to see if this live file should reload. Call this method before
	// using anything that was read & cached from the file.
	// It calls the loadFile() method if any of the following events:
	//	- the file has a new modify time since the last check;
	//	- the file used to exist and now does not;
	//	- the file used to not exist but now does.
	// Returns true if the file was reloaded.
	bool checkAndReload();

	std::string filename() const;

	// Adds this live file to an automated recheck. Normally, just calling
	// checkAndReload() is enough. In some cases though, you may need to let
	// the live file periodically check itself.
	void addToEventTimer();

	void setRefreshPeriod(F32 seconds);

protected:
	// This virtual method loads your file if it changed. It is called
	// automatically by checkAndReload(), so though you must implement this in
	// derived classes, you do not need to call it manually. Returns true if
	// the file was successfully loaded.
	virtual bool loadFile() = 0;

	// Implement this virtual method if you want to get a change callback: it
	// will be called automatically at the end of checkAndReload() if a new
	// configuration was loaded. This does not track differences between the
	// current and newly loaded file, so any successful load event will trigger
	// a changed() callback. Default is to do nothing.
	virtual void changed() {}

private:
	class Impl;
	Impl& impl;
};

#endif //LL_LLLIVEFILE_H