// ===========================================================================
// Copyright 2018 Autodesk, Inc. All rights reserved.
//
// Use of this software is subject to the terms of the Autodesk license
// agreement provided at the time of installation or download, or which
// otherwise accompanies this software in either electronic or hard copy form.
// ===========================================================================
//
//	createNSystem.mel
//
//	Description:
//		Find a suitable nucleus node or create one.
//
//		Arguments:
//			None.
//

global proc string createNSystem()
//
//	Description:
//
//		If there is an nucleus node selected, return it, 
//	otherwise, create a new one and return it.
//	TODO - add a create flag, and decide exactly when to create a new one.
//	TODO - or perhaps allow an nThing as an argument
//
{
	string $nucleus;
	string $selected[] = `ls -sl`;
	// Get the selected nucleuss
	//
	string $nsys[] = `listRelatives -type "nucleus" $selected`;
	int $numSystems = size($nsys);

	if( $numSystems == 0 ){
		$nucleus = `createNode nucleus`;
		connectAttr time1.outTime  ($nucleus + ".currentTime");
		string $ax = `upAxis -q -axis`;
		if( $ax == "z" ){
			setAttr( $nucleus + ".gravityDirection" ) 0 0 -1;
		} 
	} else {
		$nucleus = $nsys[0];
	}
	return $nucleus;
}