/*
 * Copyright 2015 (C) Tom Parker <thpr@users.sourceforge.net>
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library 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 Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package pcgen.cdom.content;

import java.io.StringReader;

import pcgen.base.formula.base.Function;
import pcgen.base.formula.library.GenericFunction;
import pcgen.base.formula.parse.FormulaParser;
import pcgen.base.formula.parse.ParseException;
import pcgen.base.formula.parse.SimpleNode;

/**
 * A UserFunction is a Formula Function that has been defined by the user via
 * data control. This is then made available to the Formula system as a custom
 * function, based on the given name (in UserContent).
 */
public class UserFunction extends UserContent
{

	/**
	 * The underlying Function for this UserFunction.
	 */
	private Function function;

	/**
	 * The original Expression for this UserFuction.
	 */
	private String origExpression;

	/**
	 * Sets the Function for this UserFunction to the function defined by the
	 * given UserExpression.
	 * 
	 * @param expression
	 *            The expression to be parsed into a Function.
	 */
	public void setFunction(String expression)
	{
		if (expression == null)
		{
			throw new IllegalArgumentException(
				"Cannot make formula from null String");
		}
		origExpression = expression;
		try
		{
			SimpleNode root =
					new FormulaParser(new StringReader(expression)).query();
			function = new GenericFunction(getKeyName(), root);
		}
		catch (ParseException e)
		{
			throw new IllegalArgumentException(e);
		}
	}

	@Override
	public String getLSTformat()
	{
		return origExpression;
	}

	/**
	 * Returns the Function for this UserFunction.
	 * 
	 * @return The Function for this UserFunction
	 */
	public Function getFunction()
	{
		return function;
	}

	@Override
	public String getDisplayName()
	{
		return getKeyName();
	}
}