/*******************************************************************************
 * Copyright (c) 2006, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.internal.intro.impl.util;

import org.eclipse.core.expressions.EvaluationContext;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.PlatformUI;

/*
 * Supplies en evaluation context for filtering intro documents. This is used for
 * resolving variables in enablement expressions.
 */
public final class IntroEvaluationContext {

	private static final String VARIABLE_PLATFORM = "platform"; //$NON-NLS-1$
	private static final String VARIABLE_WORKBENCH = "workbench"; //$NON-NLS-1$

	private static EvaluationContext context;

	/*
	 * Returns the evaluation context to use in intro documents.
	 */
	public static EvaluationContext getContext() {
		if (context == null) {
			context = new EvaluationContext(null, Platform.class);
			context.addVariable(VARIABLE_PLATFORM, Platform.class);
			context.addVariable(VARIABLE_WORKBENCH, PlatformUI.getWorkbench());
		}
		return context;
	}

	/*
	 * Not meant to be instantiated.
	 */
	private IntroEvaluationContext() {
	}
}