package net.sourceforge.phpdt.externaltools.internal.registry;

/**********************************************************************
 Copyright (c) 2002 IBM Corp. and others. All rights reserved.
 This file is made available under the terms of the Common Public License v1.0
 which accompanies this distribution, and is available at
 http://www.eclipse.org/legal/cpl-v10.html
 �
 Contributors:
 **********************************************************************/

import net.sourceforge.phpdt.externaltools.variable.ExpandVariableContext;
import net.sourceforge.phpdt.externaltools.variable.IVariableLocationExpander;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IPath;

/**
 * Represents the variable for the path location
 */
public final class PathLocationVariable extends ExternalToolVariable {
	private static final DefaultLocationExpander defaultExpander = new DefaultLocationExpander();

	private IVariableLocationExpander expander = null;

	/**
	 * Creates a path location variable
	 * 
	 * @param tag
	 *            the variable tag
	 * @param description
	 *            a short description of what the variable will expand to
	 * @param element
	 *            the configuration element
	 */
	/* package */PathLocationVariable(String tag, String description,
			IConfigurationElement element) {
		super(tag, description, element);
	}

	/**
	 * Returns the object that can expand the variable into a path location.
	 */
	public IVariableLocationExpander getExpander() {
		if (expander == null) {
			expander = (IVariableLocationExpander) createObject(ExternalToolVariableRegistry.TAG_EXPANDER_CLASS);
			if (expander == null)
				expander = defaultExpander;
		}
		return expander;
	}

	/**
	 * Default variable location implementation which does not expand variables,
	 * but just returns <code>null</code>.
	 */
	private static final class DefaultLocationExpander implements
			IVariableLocationExpander {
		/*
		 * (non-Javadoc) Method declared on IVariableLocationExpander.
		 */
		public IPath getPath(String varTag, String varValue,
				ExpandVariableContext context) {
			return null;
		}
	}
}