Copyright (c) 2004, 2015 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2004, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.preferences;

import java.net.URL;
import java.util.*;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.osgi.service.datalocation.Location;

Since:
3.0/**
 * @since 3.0
 */
public class ConfigurationPreferences extends EclipsePreferences {

	// cached values
	private int segmentCount;
	private String qualifier;
	private IPath location;
	private IEclipsePreferences loadLevel;
	// cache which nodes have been loaded from disk
	private static Set<String> loadedNodes = Collections.synchronizedSet(new HashSet<String>());
	private static boolean initialized = false;
	private static IPath baseLocation;

	static {
		Location location = PreferencesOSGiUtils.getDefault().getConfigurationLocation();
		if (location != null) {
			URL url = location.getURL();
			if (url != null)
				baseLocation = new Path(url.getFile());
		}
	}

	
Default constructor. Should only be called by #createExecutableExtension.
/**
	 * Default constructor. Should only be called by #createExecutableExtension.
	 */
	public ConfigurationPreferences() {
		this(null, null);
	}

	private ConfigurationPreferences(EclipsePreferences parent, String name) {
		super(parent, name);

		initializeChildren();

		// cache the segment count
		String path = absolutePath();
		segmentCount = getSegmentCount(path);
		if (segmentCount < 2)
			return;

		// cache the qualifier
		qualifier = getSegment(path, 1);

		// cache the location
		if (qualifier == null)
			return;
		if (baseLocation != null)
			location = computeLocation(baseLocation, qualifier);
	}

	@Override
	protected IPath getLocation() {
		return location;
	}

	@Override
	protected boolean isAlreadyLoaded(IEclipsePreferences node) {
		return loadedNodes.contains(node.name());
	}

	@Override
	protected void loaded() {
		loadedNodes.add(name());
	}

	/*
	 * Return the node at which these preferences are loaded/saved.
	 */
	@Override
	protected IEclipsePreferences getLoadLevel() {
		if (loadLevel == null) {
			if (qualifier == null)
				return null;
			// Make it relative to this node rather than navigating to it from the root.
			// Walk backwards up the tree starting at this node.
			// This is important to avoid a chicken/egg thing on startup.
			IEclipsePreferences node = this;
			for (int i = 2; i < segmentCount; i++)
				node = (EclipsePreferences) node.parent();
			loadLevel = node;
		}
		return loadLevel;
	}

	protected void initializeChildren() {
		if (initialized || parent == null)
			return;
		try {
			synchronized (this) {
				if (baseLocation == null)
					return;
				String[] names = computeChildren(baseLocation);
				for (String n : names) {
					addChild(n, null);
				}
			}
		} finally {
			initialized = true;
		}
	}

	@Override
	protected EclipsePreferences internalCreate(EclipsePreferences nodeParent, String nodeName, Object context) {
		return new ConfigurationPreferences(nodeParent, nodeName);
	}
}